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PEARSON
Investigating SCIENCE
9
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PEARSON
Investigating SCIENCE
9
Senior Author Lionel Sandner
Pauline Webb
Science Education Consultant and Writer formerly Lead Coordinator, Pan-Canadian Science Project
Markham District High School York Region District School Board
Authors
Otto Wevers Toronto District School Board
Clayton Ellis
Sandy M. Wohl
Fletcher’s Meadow Secondary School Peel District School Board
Instructor, Curriculum Studies Faculty of Education, University of British Columbia
Donald Lacy Stelly’s Secondary School Saanich School District 63, British Columbia
Catherine Little Program Coordinator Science, Environmental and Ecological Studies Toronto District School Board
Heather A. Mace Featherston Drive Public School Ottawa-Carleton District School Board
Igor Nowikow Markham District High School York Region District School Board
Contributing Authors Cathy Costello Education Consultant formerly Curriculum Coordinator, Literacy York Region District School Board
Jay Ingram Science Journalist Daily Planet Discovery Channel Canada
Senior Technology Consultant Josef Martha Science Education Consultant and Writer formerly Northern Gateway Public Schools, AB
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Copyright © 2009 Pearson Canada Inc. All rights reserved. This publication is protected by copyright, and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permission, write to the Permissions Department at Pearson Education Canada. The information and activities presented in this book have been carefully edited and reviewed. However, the publisher shall not be liable for any damages resulting, in whole or in part, from the reader’s use of this material. Brand names that appear in photographs of products in this textbook are intended to provide students with a sense of the real-world applications of science and technology and are in no way intended to endorse specific products.
ISBN-13: 978-0-13208062-0 ISBN-10: 0-13-208062-1
Printed and bound in Canada
2 3 4 5 6 TC 13 12 11 10 9
PUBLISHER: Reid McAlpine MANAGING EDITOR: Lee Ensor RESEARCH AND COMMUNICATION MANAGERS: Martin Goldberg, Patti Henderson
DIRECTOR OF PUBLISHING: Yvonne Van Ruskenveld (Edvantage Press) PROJECT MANAGER: Lee Geller (Edvantage Press) DEVELOPMENTAL EDITORS: Tricia Armstrong (Edvantage Press), Louise MacKenzie, Georgina Montgomery, Alexandra Venter CONTRIBUTING WRITER: James Milross (Edvantage Press) COPY EDITORS: Maja Grip, Jennifer Hedges, Kathy Vanderlinden PROOFREADERS: Maja Grip, Kari Magnuson, Christine McPhee INDEXER: Jennifer Hedges SENIOR PRODUCTION EDITOR: Susan Selby PRODUCTION COORDINATORS: Sharlene Ross, Shonelle Ramserran MANUFACTURING MANAGER: Jane Schell DESIGN: Alex Li COMPOSITION: Carolyn E. Sebestyen ILLUSTRATORS: Kevin Cheng, Crowle Art Group, Imagineering Media Services, Jane Whitney PHOTO RESEARCHER: Terri Rothman
This book was printed using paper containing recycled fibre content.
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Acknowledgements Consultants and Reviewers Science, Technology, Society, and the Environment Marietta (Mars) Bloch Director, Education Services Let’s Talk Science
Erminia Pedretti Director, Centre for Studies in Science, Mathematics & Technology Education OISE/University of Toronto
Catholic Education
Unit Reviewers
Kathleen Mack
Marvin Chase
St. Thomas Aquinas Catholic High School Catholic District School Board of Eastern Ontario
Sir Allan MacNab Secondary School Hamilton Wentworth District School Board
ELL/ESL
Stouffville District Secondary School York Region District School Board
Jane E. Sims
Sai Chung
Education Consultant formerly Sir Sandford Fleming Academy Toronto District School Board
Assessment and Differentiated Instruction Safety Karen Hume Educational Consultant and Writer formerly Student Success Leader Durham District School Board
Literacy Cathy Costello Education Consultant formerly Curriculum Coordinator, Literacy York Region District School Board
Andrew Cherkas
Peter Cudmore STAO Safety Committee
Ian Mackellar STAO Safety Committee
A.Y. Jackson Secondary School Toronto District School Board
Gail De Souza Marshall McLuhan Secondary School Toronto Catholic District School Board
Barbara Gaudet Elmira District Secondary School Waterloo Region District School Board
Katherine Hui
Dr. Scott Weese
Markville Secondary School York Region District School Board
University of Guelph Ontario Veterinary College
Ann Jackson
Lab and Activity Testers Radhika Artham
St. Thomas Aquinas Catholic High School Catholic District School Board of Eastern Ontario
Andrew Jordan
Environmental Education
Wexford Collegiate School for the Arts Toronto District School Board
Erindale Secondary School Peel District School Board
Jane Forbes
Farrah Jaffer
Sumble Kaukab
Instructor, Science and Technology Ontario Institute for Studies in Education University of Toronto
Wexford Collegiate School for the Arts Toronto District School Board
Instructional Coordinator Peel District School Board
Andrew Jordan
Carrie Pilgrim
Numeracy
Erindale Secondary School Peel District School Board
Lindsay Collegiate and Vocational Institute Trillium Lakelands District School Board
Bonnie Edwards
Lianne Tan
Ailynne Sobec
formerly Wellington Catholic District School Board
Aboriginal Education Corinne Mount Pleasant-Jette, C.M. Mount Pleasant Educational Services Inc.
Dawn Wiseman Mount Pleasant Educational Services Inc.
Appleby College
Fletcher’s Meadow Secondary School Peel District School Board
Expert Reviewers
Kevin Spence
Dr. Monika Havelka
Adult High School Ottawa-Carleton District School Board
University of Toronto
Lianne Tan
Dr. Brian Martin
Appleby College
The King’s University College
Ron Thorpe
Dr. Marina Milner-Bolotin
TDSB Program/Project Coordinator (retired) Canadian Space Resource Centre Toronto District School Board
Ryerson University
Dr. Rashmi Venkateswaran University of Ottawa
Jennifer Wilson R.H. King Academy Toronto District School Board
Acknowledgements
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Contents Welcome to Investigating Science 9
xviii
Science 9 at a Glance
xxiv
Science Safety Procedures
UNIT
A
Sustainable Ecosystems
1
2
3
Exploring
4
Ecosystems are complex, self-regulating systems of organisms and their abiotic environments. Before Reading
1.1 Ecosystems A2 Quick Lab Representing Canadian Biodiversity
DI
36
A7 Quick Lab Keeping a Balance
37
During Reading
38
Learning Checkpoint
42
Take It Further
42
A8 STSE Science, Technology, Society, and the Environment Spotlight on Nature
43
A9 Just-in-Time Math Choosing a Scale
43
A10 Inquiry Activity Predation Simulation
44
1.3 Check and Reflect
46
Science Everywhere Cool Symbiosis
47
1.0 Chapter Review
48
After Reading
49
Unit Task Link
49
5
2
Human activity affects the sustainability of ecosystems. Before Reading
6 7
8 9
2.1 Human Use of Ecosystems
50 51
52
A11 Quick Lab Managing Resources
53
During Reading
55
Learning Checkpoint
60
Take It Further
63
Learning Checkpoint
63
A12 STSE Decision-Making Analysis Wild Fish Versus Farmed Fish
64
During Reading
10
Learning Checkpoint
13
Take It Further
19
A3 Quick Lab Natural Versus Artificial
20
A13 STSE Case Study: Decision-Making Analysis Invasive Species
66
1.1 Check and Reflect
21
2.1 Check and Reflect
67
1.2 Nutrient Cycles and Energy Flow
vi
xxvi
Unit Task
A1 STSE Science, Technology, Society and the Environment Pesticide Use Across the Country
1.3 Interactions in Ecosystems
22
A4 Quick Lab Finding the Relationships Among Organisms
23
Learning Checkpoint
27
Learning Checkpoint
29
During Reading
30
Take It Further
32
A5 Quick Lab Analyzing Cycles
33
A6 Quick Lab Comparing Energy Pyramids
34
1.2 Check and Reflect
35
Contents
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Contents 2.2 Assessing the Impact of Human Activities on Ecosystems DI
3.2 Environmental Stewardship 68
104
A21 Quick Lab Making Connections
105
A14 Quick Lab If Earth Were an Apple
69
During Writing
108
Learning Checkpoint
75
Learning Checkpoint
109
Take It Further
80
Take It Further
112
During Reading
80
Learning Checkpoint
114
Learning Checkpoint
80
A22 STSE Science, Technology, Society, and the Environment What’s for Dinner? 114
A15 STSE Science, Technology, Society, and the Environment Increasing Biodiversity in Your Community 81 A16 Skill Builder Activity Extrapolation
81
A17 Design a Lab Testing the Effects of Fertilizer on Soil and Aquatic Ecosystems
82
A18 Quick Lab Deforestation and Watersheds
84
2.2 Check and Reflect
85
Investigating Careers in Science Great Canadians in Science David Suzuki
86
Science in MY Future Ecological Consultant
87
2.0 Chapter Review
88
After Reading
89
Unit Task Link
89
3
DI
Governments, groups and individuals work together to promote sustainable ecosystems. Before Writing
3.1 Government Action to Protect Canada’s Ecosystems
A23 Quick Lab Calculating Your Ecological Footprint
115
A24 Quick Lab Environmental Organizations
115
3.2 Check and Reflect
116
Cool Ideas Panamanian Cowbird Puzzle
117
3.0 Chapter Review
118
After Writing
119
Unit Task Link
119
Unit A Summary
120
Unit A Task
122
Unit A Review
124
90 91
92
A19 Quick Lab Modelling a Wetland
93
During Writing
95
Learning Checkpoint
97
Take It Further
101
Learning Checkpoint
101
A20 Decision-Making Analysis Assessing a Government Program — Recycling
102
3.1 Check and Reflect
103
Contents
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Contents 4.0 Chapter Review
Atoms, Elements, and Compounds 130
UNIT
B
5 Unit Task
131
Exploring
132
B1 STSE Science, Technology, Society, and the Environment Do We Need Plastic Shopping Bags? 133
4
Matter has physical and chemical properties.
134
Before Reading
135
4.1 Investigating Matter
136
After Reading
165
Unit Task Link
165
The periodic table organizes elements by patterns in properties and atomic structure.
166
Before Reading
5.1 Developing the Atomic Theory
167 DI
168
B10 Quick Lab Calcium Metal in Water
169
During Reading
172
Learning Checkpoint
175
Take It Further
175
B11 STSE Quick Lab Developing the Atomic Theory
176
5.1 Check and Reflect
177
B2 Quick Lab Observing Changes in Matter
137
Learning Checkpoint
140
During Reading
140
B12 Quick Lab Meet the Elements
179
Take It Further
143
During Reading
182
Learning Checkpoint
143
Learning Checkpoint
183
B3 Inquiry Activity Identifying Gases
144
Take It Further
185
B4 Quick Lab Foam in a Cup
146
4.1 Check and Reflect
147
B13 Skill Builder Activity Using a Dissecting Microscope
186
B14 Quick Lab Growing Silver
186
5.2 Check and Reflect
187
4.2 Physical and Chemical Properties
DI
148
During Reading
149
B5 Quick Lab Observing a Physical Change
149
Learning Checkpoint
153
Take It Further
155
B6 STSE Science, Technology, Society, and the Environment Polyethylene Plastic 155
5.2 The Elements
5.3 The Periodic Table
178
188
B15 Quick Lab Exploring the Periodic Table
189
Learning Checkpoint
190
Learning Checkpoint
193
Learning Checkpoint
195
During Reading
196
Take It Further
198
Learning Checkpoint
199
B7 Inquiry Activity Using Properties to Identify Pure Substances
156
B8 Inquiry Activity Investigating Physical and Chemical Changes
158
B9 Design a Lab Properties of Common Substances
B16 STSE Science, Technology, Society, and the Environment Working with Toxic Elements 200
160
B17 Quick Lab Drawing Bohr Diagrams
4.2 Check and Reflect
161
B18 STSE Case Study: Decision-Making Analysis Heavy Metals in Fish 201
Great Canadians in Science Lee Wilson
162
B19 Inquiry Activity Building a Periodic Table
202
Science in My Future The Art of Chemistry
163
5.3 Check and Reflect
204
Science Everywhere Diamonds: Responsible Mining and Production
205
Investigating Careers in Science
viii
164
Contents
200
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Contents 5.0 Chapter Review
6
206
After Reading
207
Unit Task Link
207
Elements combine to form ionic compounds and molecular compounds. Before Writing
6.1 How Compounds Form
6.3 Balancing the Hazards and Benefits of Compounds DI
230
B27 Quick Lab What Do I Do with My Batteries? 231 During Writing
232
Learning Checkpoint
236
B28 STSE Science, Technology, Society, and the Environment POPs and Pesticides 236
208 209
210
B29 STSE Case Study: Decision-Making Analysis Fluoridation of Drinking Water 237 6.3 Check and Reflect
238
Cool Ideas How Small Is an Atom?
239
B20 Quick Lab Water and Hydrogen Peroxide (Teacher Demonstration)
211
6.0 Chapter Review
During Writing
212
After Writing
241
Learning Checkpoint
213
Unit Task Link
241
Take It Further
214
B21 Quick Lab Salt and Sugar
215
B22 Skill Builder Activity Molecular Model Kits
215
B23 Quick Lab Building Molecular Models
216
6.1 Check and Reflect
217
6.2 Names and Formulas of Common Compounds
240
Unit B Summary
242
Unit B Task
244
Unit B Review
246
218
B24 Quick Lab Naming Compounds
219
Learning Checkpoint
220
Take It Further
224
B25 Quick Lab Copper Compounds
227
B26 STSE Decision-Making Analysis Salt or Sand?
228
6.2 Check and Reflect
229
Contents
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Contents 7.3 The Expanding Universe
UNIT
C
The Study of the Universe 252
C8 Quick Lab Comparing Light Spectra
279
During Reading
280
Learning Checkpoint
284
Take It Further
286
C9 STSE Science, Technology, Society, and the Environment The Power of Observation 286 Unit Task
253
Exploring
C10 Quick Lab Modelling the Expansion of the Universe
254
C1 STSE Science, Technology, Society, and the Environment Space Exploration in the News 255
Scientific evidence suggests that the universe began expanding from a single point about 13.7 billion years ago. Before Reading
7.1 Space Flight to the Stars
257
258
C2 Quick Lab A Map of the Universe
259
During Reading
260
Learning Checkpoint
262
Take It Further
264
C3 Just-in-Time Math Scientific Notation
265
C4 Quick Lab All These Worlds
266
7.1 Check and Reflect
267
7.2 Galaxies
DI
C5 Quick Lab Hunting for Galaxies in the Hubble Ultra Deep Field
x
256
268 269
During Reading
271
Learning Checkpoint
273
Take It Further
274
C6 Just-in-Time Math Math Scaling
275
C7 Quick Lab Modelling the Distances to Galaxies
276
7.2 Check and Reflect
277
Contents
8
287
7.3 Check and Reflect
288
Science Everywhere Hunting Black Holes
289
7.0 Chapter Review
7
278
290
After Reading
291
Unit Task Link
291
The solar system formed 5 billion years ago, in the same way other star-and-planet systems in the universe formed. 292 Before Reading
293
8.1 Stars
294
C11 Quick Lab Reading Star Charts
295
During Reading
297
Take It Further
301
C12 Inquiry Activity Using a Star Chart
302
C13 Design a Lab Star Light, How Bright?
303
C14 Quick Lab Analyzing the Stars by Their Spectral Patterns
304
8.1 Check and Reflect
305
8.2 The Solar System
DI
306
C15 Quick Lab Sizing Up the Solar System
307
During Reading
308
Learning Checkpoint
311
Take It Further
318
C16 Inquiry Activity Measuring the Sun’s Diameter
319
C17 Problem-Solving Activity A Model of the Solar System
320
8.2 Check and Reflect
321
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Contents 8.3 Earth, the Sun, and the Moon
322
352
C18 Quick Lab The Effects of Earth’s Motion on Our View of the Sky
323
During Reading
324
C25 Quick Lab The Value of the View from High Above Earth
353
Learning Checkpoint
326
During Writing
358
Take It Further
329
Take It Further
360
C19 STSE Science, Technology, Society, and the Environment Space Weather 329
C26 STSE Quick Lab Canadian Contributions to Space Research, Technology, and Exploration
361
C20 Quick Lab The Phases of the Moon
330
C27 Quick Lab On Location with GPS
362
8.3 Check and Reflect
331
9.2 Check and Reflect
363
Investigating Careers in Science Great Canadians in Science Julie Payette
332
Science in My Future Robotics Engineer
333
8.0 Chapter Review
9
9.2 Benefits of Space Research and Exploration DI
334
After Reading
335
Unit Task Link
335
Space exploration improves our knowledge and gives us beneficial technologies, but its hazards and costs are significant. Before Writing
336
9.3 Costs and Hazards of Space Research and Exploration
365
During Writing
367
C29 STSE Science, Technology, Society, and the Environment Sharing a Small Place in Space 370 C30 Problem-Solving Activity The Effects of Space Travel on Human Health
371
C31 STSE Case Study: Decision-Making Analysis Our Mess in Space: The Growing Problems of Space Debris
372
9.3 Check and Reflect
374
Cool Ideas Save the Stars…with Dark-Night Preserves
375
337
9.0 Chapter Review 9.1 How Ideas of the Universe Have Changed over Time
364
C28 STSE Quick Lab Who Owns Space?
338
C21 STSE Quick Lab Greetings from the People of Earth
339
Learning Checkpoint
345
During Writing
348
Take It Further
348
C22 STSE Quick Lab Human Time and the Sky
349
C23 Just-in-time Math Showing Different Types of Data on the Same Graph
349
C24 Quick Lab Plotting a Planet’s Orbital Radius and Its “Year”
350
9.1 Check and Reflect
351
376
After Writing
377
Unit Task Link
377
Unit C Summary
378
Unit C Task
380
Unit C Review
382
Contents
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Contents
UNIT
D
The Characteristics of Electricity 388
Unit Task
Exploring
10
D10 Quick Lab Make Your Own Photocopier
389
390
424
D11 Quick Lab Make Your Own Precipitator
425
10.3 Check and Reflect
426
Science Everywhere Deep Brain Stimulation
427
10.0 Chapter Review
428
D1 STSE Science, Technology, Society, and the Environment Electricity Concept Map 391
After Reading
429
Unit Task Link
429
Static charges collect on surfaces and remain there until given a path to escape. 392
Current electricity is the continuous flow of electrons in a closed circuit.
Before Reading
10.1 Exploring the Nature of Static Electricity
393
394
11
Before Reading
11.1 Current, Potential Difference, and Resistance
430 431
432
D2 Quick Lab Characteristics of Electric Charge
395
D12 Quick Lab Light the Lights
433
Learning Checkpoint
398
During Reading
434
During Reading
399
Learning Checkpoint
436
Learning Checkpoint
401
Learning Checkpoint
438
Take It Further
401
Learning Checkpoint
442
D3 Inquiry Activity Investigating Static Electricity 402
Take It Further
443
10.1 Check and Reflect
D13 Quick Lab Make Your Own Dimmer Switch
444
D14 Quick Lab Modelling Potential Difference, Current, and Resistance
445
D15 Design a Lab Investigating Conductivity
446
11.1 Check and Reflect
447
10.2 The Transfer of Static Electric Charges DI
403
404
D4 Quick Lab Using an Electroscope
405
During Reading
407
Learning Checkpoint
409
Take It Further
411
D16 Quick Lab Keep the Lights On
449
D5 Quick Lab Charge Sorter
412
Learning Checkpoint
450
D6 Inquiry Activity Charging by Contact
413
Take It Further
453
D7 Inquiry Activity Charging by Induction
414
Learning Checkpoint
453
10.2 Check and Reflect
415
D17 Quick Lab Off and On
453
D18 Skill Builder Activity Using Equipment Accurately and Safely
454
10.3 Electrostatics in Our Lives
xii
D9 STSE Science, Technology, Society, and the Environment Advertisments for Static Control Products 423
416
11.2 Series Circuits and Parallel Circuits 448
D8 STSE Quick Lab Lightning: Facts and Fiction
D19 Inquiry Activity Series Circuit Analysis
455
417
D20 Inquiry Activity Parallel Circuit Analysis
456
During Reading
419
11.2 Check and Reflect
457
Learning Checkpoint
420
Take It Further
422
Contents
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Contents 11.3 Ohm’s Law
DI
458
D21 Quick Lab Potential Difference, Current, and Resistance
459
During Reading
462
Take It Further
464
D22 STSE Science, Technology, Society, and the Environment Electrical Safety 464 D23 Inquiry Activity Investigating Ohm’s Law
465
D24 Inquiry Activity Resisting the Flow
466
11.3 Check and Reflect
467
Investigating Careers in Science Great Canadians in Science Max Donelan
468
Science in My Future Line Installers and Repairers
469
11.0 Chapter Review
12
470
After Reading
471
Unit Task Link
471
We can reduce our electrical energy consumption and use renewable energy resources to produce electrical energy. 472 Before Writing
12.1 Renewable and Non-Renewable Energy Resources for Generating Electricity
473
D29 STSE Science, Technology, Society, and the Environment A Self-Sufficient Energy Community
496
D30 Quick Lab Electricity in Your Home
496
D31 Quick Lab Marketing Fluorescent Light Bulbs
497
12.2 Check and Reflect
498
Cool Ideas A Light Show in Your Mouth
499
12.0 Chapter Review
500
After Writing
501
Unit Task Link
501
Unit D Summary
502
Unit D Task
504
Unit D Review
506
Skills References
512
Answers to Numerical Questions
555
Glossary
559
Index
566
Credits
573
Periodic Table
576
474
D25 Quick Lab Renewable Energy Projects in Your Community
475
During Writing
477
Learning Checkpoint
479
Learning Checkpoint
483
Take It Further
484
D26 STSE Case Study: Decision-Making Analysis Three Gorges: Potential Disaster or Good Choice? 486 D27 Decision-Making Analysis Producing Electricity in an Ontario Community
488
12.1 Check and Reflect
489
12.2 Reducing Our Electrical Energy Consumption DI
490
D28 Quick Lab Analyzing Home Electrical Use
491
Learning Checkpoint
492
During Writing
493
Take It Further
495
Contents
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Labs and Activities UNIT
A 1
2
UNIT
B
Sustainable Ecosystems
Unit Task
131
B2 Quick Lab Observing Changes in Matter
137
B3 Inquiry Activity Identifying Gases DI
144
B4 Quick Lab Foam in a Cup
146
B5 Quick Lab Observing a Physical Change
149
B7 Inquiry Activity Using Properties to Identify Pure Substances
156
B8 Inquiry Activity Investigating Physical and Chemical Changes
158
B9 Design a Lab Properties of Common Substances
160
Unit Task Link
165
B10 Quick Lab Calcium Metal in Water
169
B11 STSE Quick Lab Developing the Atomic Theory
176
66
B12 Quick Lab Meet the Elements DI
179
A14 Quick Lab If Earth Were an Apple
69
A16 Skill Builder Activity Extrapolation
81
B13 Skill Builder Activity Using a Dissecting Microscope
186
B14 Quick Lab Growing Silver
186
Unit Task
3
A2 Quick Lab Representing Canadian Biodiversity
9
A3 Quick Lab Natural Versus Artificial
20
A4 Quick Lab Finding the Relationships Among Organisms
23
A5 Quick Lab Analyzing Cycles
33
A6 Quick Lab Comparing Energy Pyramids
34
A7 Quick Lab Keeping a Balance
37
A10 Inquiry Activity Predation Simulation DI
44
Unit Task Link
49
A11 Quick Lab Managing Resources
53
4
5
A12 STSE Decision-Making Analysis Wild Fish Versus Farmed Fish
64
A13 STSE Case Study: Decision-Making Analysis Invasive Species
A17 Design a Lab Testing the Effects of Fertilizer on Soil and Aquatic Ecosystems
3
Atoms, Elements, and Compounds
82
B15 Quick Lab Exploring the Periodic Table
189
A18 Quick Lab Deforestation and Watersheds
84
B17 Quick Lab Drawing Bohr Diagrams
200
Unit Task Link
89
B18 STSE Case Study: Decision-Making Analysis Heavy Metals in Fish 201
A19 Quick Lab Modelling a Wetland
93
B19 Inquiry Activity Building a Periodic Table
202
Unit Task Link
207
B20 Quick Lab Water and Hydrogen Peroxide (Teacher Demonstration)
211
115
B21 Quick Lab Salt and Sugar
215
A24 Quick Lab Environmental Organizations
115
B22 Skill Builder Activity Molecular Model Kits
215
Unit Task Link
119
B23 Quick Lab Building Molecular Models DI
216
B24 Quick Lab Naming Compounds
219
B25 Quick Lab Copper Compounds
227
B26 STSE Decision-Making Analysis Salt or Sand?
228
A20 Decision-Making Analysis Assessing a Government Program — Recycling DI
102
A21 Quick Lab Making Connections
105
A23 Quick Lab Calculating Your Ecological Footprint
Unit A Task
122
6
B27 Quick Lab What Do I Do with My Batteries? 231 B29 STSE Case Study: Decision-Making Analysis Fluoridation of Drinking Water 237 Unit Task Link
Unit B Task
xiv
Labs and Activities
241
244
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Labs and Activities
UNIT
UNIT
C 7
8
9
D
The Study of the Universe
Unit Task
253
C2 Quick Lab A Map of the Universe
259
C4 Quick Lab All These Worlds
266
10
The Characteristics of Electricity
Unit Task
389
D2 Quick Lab Characteristics of Electric Charge
395
D3 Inquiry Activity Investigating Static Electricity DI
402
D4 Quick Lab Using an Electroscope
405
D5 Quick Lab Charge Sorter
412
C5 Quick Lab Hunting for Galaxies in the Hubble Ultra Deep Field
269
C7 Quick Lab Modelling the Distances to Galaxies DI
276
D6 Inquiry Activity Charging by Contact
413
C8 Quick Lab Comparing Light Spectra
279
D7 Inquiry Activity Charging by Induction
414
C10 Quick Lab Modelling the Expansion of the Universe
287
D8 STSE Quick Lab Lightning: Facts and Fiction
417
Unit Task Link
291
D10 Quick Lab Make Your Own Photocopier
424
C11 Quick Lab Reading Star Charts
295
D11 Quick Lab Make Your Own Precipitator
425
C12 Inquiry Activity Using a Star Chart
302
Unit Task Link
429
C13 Design a Lab Star Light, How Bright?
303
D12 Quick Lab Light the Lights
433
C14 Quick Lab Analyzing the Stars by Their Spectral Patterns
304
D13 Quick Lab Make Your Own Dimmer Switch
444
C15 Quick Lab Sizing Up the Solar System DI
307
D14 Quick Lab Modelling Potential Difference, Current, and Resistance
445
C16 Inquiry Activity Measuring the Sun’s Diameter
319
D15 Design a Lab Investigating Conductivity
446
D16 Quick Lab Keep the Lights On
449 453
11
C17 Problem-Solving Activity A Model of the Solar System
320
D17 Quick Lab Off and On
C18 Quick Lab The Effects of Earth’s Motion on Our View of the Sky
323
D18 Skill Builder Activity Using Equipment Accurately and Safely
454
C20 Quick Lab The Phases of the Moon
330
D19 Inquiry Activity Series Circuit Analysis
455
Unit Task Link
335
D20 Inquiry Activity Parallel Circuit Analysis
456
D21 Quick Lab Potential Difference, Current, and Resistance
459 465
C21 STSE Quick Lab Greetings from the People of Earth
339
D23 Inquiry Activity Investigating Ohm’s Law
C22 STSE Quick Lab Human Time and the Sky
349
D24 Inquiry Activity Resisting the Flow DI
466
Unit Task Link
471
D25 Quick Lab Renewable Energy Projects in Your Community
475
C24 Quick Lab Plotting a Planet’s Orbital Radius and Its “Year” DI
350
C25 Quick Lab The Value of the View from High Above Earth
353
12
C26 STSE Quick Lab Canadian Contributions to Space Research, Technology, and Exploration
361
C27 Quick Lab On Location with GPS
362
9.2 Check and Reflect
363
D27 Decision-Making Analysis Producing Electricity in an Ontario Community
488
C28 STSE Quick Lab Who Owns Space?
365
12.1 Check and Reflect
489
C30 Problem-Solving Activity The Effects of Space Travel on Human Health
D28 Quick Lab Analyzing Home Electrical Use
491
371
D30 Quick Lab Electricity in Your Home
496
D31 Quick Lab Marketing Fluorescent Light Bulbs DI
497
Unit Task Link
501
C31 STSE Case Study: Decision-Making Analysis Our Mess in Space: The Growing Problems of Space Debris
372
Unit Task Link
377
Unit C Task
380
D26 STSE Case Study: Decision-Making Analysis Three Gorges: Potential Disaster or Good Choice? 486
Unit D Task
504 Labs and Activities
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Science, Technology, Society, and the Environment UNIT
UNIT
A
C
Sustainable Ecosystems
A1 STSE Science, Technology, Society and the Environment Pesticide Use Across the Country
5
1
A8 STSE Science, Technology, Society, and the Environment Spotlight on Nature
43
2
A12 STSE Decision-Making Analysis Wild Fish Versus Farmed Fish
64
A13 STSE Case Study: Decision-Making Analysis Invasive Species
66
C1 STSE Science, Technology, Society, and the Environment Space Exploration in the News 255
7
C9 STSE Science, Technology, Society, and the Environment The Power of Observation 286
8
C19 STSE Science, Technology, Society, and the Environment Space Weather 329
9
C21 STSE Quick Lab Greetings from the People of Earth
339
C22 STSE Quick Lab Human Time and the Sky
349
C26 STSE Quick Lab Canadian Contributions to Space Research, Technology, and Exploration
361
C28 STSE Quick Lab Who Owns Space?
365
A15 STSE Science, Technology, Society, and the Environment Increasing Biodiversity in Your Community 81 A22 STSE Science, Technology, Society, and the Environment What’s for Dinner? 114
3
The Study of the Universe
C29 STSE Science, Technology, Society, and the Environment Sharing a Small Place in Space 370 C31 STSE Case Study: Decision-Making Analysis Our Mess in Space: The Growing Problems of Space Debris
UNIT
B
UNIT
Atoms, Elements, and Compounds
D
B1 STSE Science, Technology, Society, and the Environment Do We Need Plastic Shopping Bags? 133
4 5
B6 STSE Science, Technology, Society, and the Environment Polyethylene Plastic 155 B11 STSE Quick Lab Developing the Atomic Theory
B18 STSE Case Study: Decision-Making Analysis Heavy Metals in Fish 201 B26 STSE Decision-Making Analysis Salt or Sand?
228
B28 STSE Science, Technology, Society, and the Environment POPs and Pesticides 236 B29 STSE Case Study: Decision-Making Analysis Fluoridation of Drinking Water 237
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Science, Technology, Society, and the Environment
The Characteristics of Electricity
D1 STSE Science, Technology, Society, and the Environment Electricity Concept Map 391
10
D8 STSE Quick Lab Lightning: Facts and Fiction
417
D9 STSE Science, Technology, Society, and the Environment Advertisments for Static Control Products 423
176
B16 STSE Science, Technology, Society, and the Environment Working with Toxic Elements 200
6
372
11
D22 STSE Science, Technology, Society, and the Environment Electrical Safety 464
12
D26 STSE Case Study: Decision-Making Analysis Three Gorges: Potential Disaster or Good Choice? 486 D29 STSE Science, Technology, Society, and the Environment A Self-Sufficient Energy Community
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Science Readings UNIT
UNIT
A 1
Science Everywhere Cool Symbiosis
2
Investigating Careers in Science
47
7
Science Everywhere Hunting Black Holes
8
Investigating Careers in Science
4
86
Great Canadians in Science Julie Payette
332
87
Science in My Future Robotics Engineer
333
117
375
D
The Characteristics of Electricity
10 162
Science Everywhere Deep Brain Stimulation
163
11
Investigating Careers in Science
Investigating Careers in Science Science in My Future The Art of Chemistry
6
Cool Ideas Save the Stars…with Dark-Night Preserves
9
UNIT
Atoms, Elements, and Compounds
Great Canadians in Science Lee Wilson
5
289
Science in MY Future Ecological Consultant
UNIT
B
The Study of the Universe
Great Canadians in Science David Suzuki Cool Ideas Panamanian Cowbird Puzzle
3
C
Sustainable Ecosystems
Science Everywhere Diamonds: Responsible Mining and Production
205
Cool Ideas How Small Is an Atom?
239
12
427
Great Canadians in Science Max Donelan
468
Science in My Future Line Installers and Repairers
469
Cool Ideas A Light Show in Your Mouth
499
Science Readings
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PEARSON
Investigating SCIENCE
9
You are about to begin a scientific exploration using Investigating Science 9. To assist you in your journey, this book has been designed with the following features to help you.
1. Unit Overview — what you will learn The book is divided into four units. Each unit opens with a large photograph that captures one of the ideas that will be covered in the unit. The unit Contents lists the Chapters, Key Ideas, and sections in the unit. The orange DI box indicates essential lessons that have additional differentiated instruction support in the Teacher’s Resource.
An introduction to the Unit Task is provided below the unit Contents. This task is revisited at the end of each chapter, providing you with an opportunity to review key ideas covered in the chapter that will be required to successfully complete the Unit Task.
2. Exploring — adds interest This spread is an introduction. It has an interesting real-world example to introduce the unit.
This activity connects the themes of Science, Technology, Society, and the Environment to what you are learning.
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3. Chapter Introduction — organizes the topics Each chapter starts with an engaging visual designed to motivate your interest and provide discussion opportunities for the class.
The right side of the page provides learning support for you by listing What Skills You Will Use, Concepts You Will Learn, and Why This Is Important. A Before Reading or Before Writing strategy starts the Before, During, and After literacy activities for each chapter.
4. Sections — engaging information on the topics There are two or three sections in each chapter. Each section starts with a reading and a Quick Lab activity.
The Quick Lab activity is a short, informal learning experience using simple materials and equipment.
Each section includes a summary of what you will learn in the section.
During Reading and During Writing literacy activities provide you with an opportunity to consolidate your understanding. The Learning Checkpoint allows you to check your understanding of what you have just read. Words Matter helps you understand a term by describing its origin.
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4. Sections — engaging information on the topics (continued) Skill Builder Activity reviews or reinforces certain skills necessary for completing some of the activities.
Just-in-Time Math provides an opportunity to review some of your math skills before using those skills in an activity.
Example Problems show the detailed steps in solving problems.
Practice Problems model the example problem and provide opportunities for further practice. Use these problems to check if you understand the concept being discussed.
Check and Reflect questions provide opportunities for you to review the main ideas you have learned in each section.
At the end of the section is a Take It Further. This is an additional way to study one of the ideas in the section.
You will find many photos and illustrations to help explain or clarify many of the ideas in the unit. After Reading or After Writing literacy activities provide you with an opportunity to consolidate your understanding
The Chapter Review contains questions relevant to the whole chapter. Answering the questions will help you consolidate what you have learned in the various parts of the chapter.
The Unit Task Link provides you with an opportunity to review key ideas covered in the chapter that will be required to successfully complete the Unit Task.
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5. Activities — develop your science skills There are five main types of activities: Inquiry Activities, Quick Labs, Decision-Making Analyses, ProblemSolving Activities, and Design a Lab activities. The Quick Lab was discussed on page xix.
Inquiry Activity: These activities provide the oportunity for you to work in a lab setting. You will develop scientific skills of predicting, observing, measuring, recording, inferring, analyzing, and many more. In these activities, you will investigate many different phenomena found in our world.
Design a Lab: These activities provide an opportunity to apply the skills you have learned to investigate a question related to a concept. You will research, plan, and carry out your own investigation. After collecting data from your experiment, you will draw conclusions and report on your findings.
Decision-Making Analysis: These activities present issues or questions related to everyday life. You will need to analyze the issue and develop an opinion based on the evidence you collect and make an informed decision. In many instances, you will present your findings and decisions to your classmates. If your Decision-Making Analysis has a Case Study logo, then you will analyze a particular issue that may involve several viewpoints or have more than one solution. Here is an opportunity for you to use the different ideas you have learned from the unit or collected from other sources to form your own opinion.
Problem-Solving Activity: These are open-ended activities that allow you to be creative. You will identify a problem, make a plan, and then construct a solution. These activities tend to have very little set-up, and there is usually more than one correct solution.
6. Unit Summary — a review of what you’ve learned At a glance, you can find all of the key concepts you have learned within the unit. You can also read the summary of ideas in each section of the unit as well as review vocabulary and key visuals. These pages can help you organize your notes for studying.
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7. Unit Task — lets you demonstrate learned skills A task at the end of each unit presents an opportunity for you to demonstrate what you’ve learned. You’ll work in a group or individually. The task requires you to apply some of the skills and knowledge that you have acquired during the unit.
8. Unit Review — connects what you have learned The Unit Review is an opportunity to review the concepts, skills, and ideas you have learned in the unit.
Key Terms Review This is a chance to review the important terms in the unit
Connect Your Understanding Questions that require you to use the ideas in more than one chapter in your answers
Skills Practice Questions related to specific skills you have learned in the unit
Key Concept Review Questions designed to review your basic understanding of the key concepts in each chapter of the unit
Science, Technology, Society, and the Environment Opportunities to express your thoughts about ideas related to Science, Technology, Society, and the Environment issues discussed in the unit
Revisit the Big Ideas and Fundamental Concepts Questions that revisit the Big Ideas and Fundamental Concepts covered in the unit
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Reflection Opportunities to express your thoughts about ideas you have discovered in the unit
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9. Other Features — bring science to life Here are other features you will find in each unit. Each one has a different purpose and is designed to help you learn about the ideas in the unit.
Investigating Careers in Science Here you will find profiles of great Canadians in science as well as careers in science based on the different types of science studied in each unit.
Science Everywhere This feature presents interesting information about concepts covered in the unit. Cool Ideas This feature is written by Discovery Channel Daily Planet host Jay Ingram to connect concepts covered in the unit to findings coming from current research.
10. Skills Reference — provides skills information and practice These pages provide references to lab safety and other basic scientific skills that will help you as you do the activities. Remember to check the Skills Reference when you need a reminder about these skills.
Now it is time to start. We hope you will enjoy your scientific exploration using Investigating Science 9!
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Science 9 at a Glance Biology
Chemistry
UNIT A: Sustainable Ecosystems
UNIT B: Atoms, Elements, and Compounds
Big Ideas
Big Ideas
• Ecosystems are dynamic and have the ability to respond to change, within limits, while maintaining their ecological balance.
• Elements and compounds have specific physical and chemical properties that determine their practical uses.
• People have the responsibility to regulate their impact on the sustainability of ecosystems in order to preserve them for future generations.
• The use of elements and compounds has both positive and negative effects on society and the environment.
Fundamental Concepts • Systems and Interactions
• Matter
• Sustainability and Stewardship
• Structure and Function
• Change and Continuity
• Sustainability and Stewardship
Overall Expectations 1. assess the impact of human activities on the sustainability of terrestrial and/or aquatic ecosystems, and evaluate the effectiveness of courses of action intended to remedy or mitigate negative impacts 2. investigate factors related to human activity that affect terrestrial and aquatic ecosystems, and explain how they affect the sustainability of these ecosystems 3. demonstrate an understanding of the dynamic nature of ecosystems, particularly in terms of ecological balance and the impact of human activity on the sustainability of terrestrial and aquatic ecosystems
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Fundamental Concepts
Overall Expectations 1. assess social, environmental, and economic impacts of the use of common elements and compounds, with reference to their physical and chemical properties 2. investigate, through inquiry, the physical and chemical properties of common elements and compounds 3. demonstrate an understanding of the properties of common elements and compounds, and of the organization of elements in the periodic table
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Science 9 at a Glance
Earth and Space Science
Physics
UNIT C: The Study of the Universe
UNIT D: The Characteristics of Electricity
Big Ideas
Big Ideas
• Different types of celestial objects in the solar system and universe have distinct properties that can be investigated and quantified.
• Electricity is a form of energy produced from a variety of non-renewable and renewable sources.
• People use observational evidence of the properties of the solar system and the universe to develop theories to explain their formation and evolution.
• The production and consumption of electrical energy has social, economic, and environmental implications.
• Space exploration has generated valuable knowledge but at enormous cost.
Fundamental Concepts
• Static and current electricity have distinct properties that determine how they are used.
Fundamental Concepts
• Matter
• Energy
• Energy
• Systems and Interactions
• Systems and Interactions
• Structure and Function
• Structure and Function • Change and Continuity
Overall Expectations 1. assess some of the costs, hazards, and benefits of space exploration and the contributions of Canadians to space research and technology 2. investigate the characteristics and properties of a variety of celestial objects visible from Earth in the night sky 3. demonstrate an understanding of the major scientific theories about the structure, formation, and evolution of the universe and its components and of the evidence that supports these theories
Overall Expectations 1. assess some of the costs and benefits associated with the production of electrical energy from renewable and non-renewable sources, and analyze how electrical efficiencies and savings can be achieved, through both the design of technological devices and practices in the home 2. investigate, through inquiry, various aspects of electricity, including the properties of static and current electricity, and the quantitative relationships between potential difference, current, and resistance in electrical circuits 3. demonstrate an understanding of the principles of static and current electricity
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Safety Science Safety Procedures You will be doing many activities in this book. When doing an activity, it is very important that you follow the safety rules below. Your teacher may have safety instructions to add to this list.
Before You Begin 1. Read and make sure you understand the instructions in the text or in any handouts your teacher may provide. Follow your teacher’s direction always. Never change or start an activity without approval. 2. Watch for “Caution” notes such as the one below. These notes will tell you how to take extra care as you work through the activity. Make sure you understand what the cautions mean. CAUTION: Tie back long hair, and be careful around open flames. Do not touch calcium metal with your bare hands as the metal will react with moisture in your skin.
3. Learn to recognize the safety symbols and the warning symbols for hazardous materials as seen on the next page. These include WHMIS symbols. WHMIS is the Workplace Hazardous Materials Information System. 4. Keep your work area uncluttered and organized. 5. Know the location of fire extinguishers and other safety equipment. 6. Always wear safety goggles and any other safety clothing as requested by your teacher or identified in this book. 7. If you have long or loose hair, tie it back. Roll up long sleeves. 8. Inform your teacher if you have any allergies or medical conditions or anything else that might affect your work in the science classroom. 9. Review the Material Safety Data Sheet (MSDS) for any chemicals you use in the lab. See an example of one on the next page.
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Safety
Safety Symbols
WHMIS Symbols
When you see this symbol, wear goggles or safety glasses while doing the activity. This symbol tells you that you will be using glassware during the activity. Take extra care when handling it.
compressed gas
biohazardous infectious material
dangerously reactive material
corrosive material
oxidizing material
flammable and combustible material
poisonous and infectious material causing immediate and serious toxic effects
poisonous and infectious material causing other toxic effects
When you see this symbol, wear an apron while doing the activity. When you see this symbol, wear insulated gloves to protect your hands from heat. This symbol tells you that you will be working with sharp objects. Take extra care when handling them. When you see this symbol, wear gloves while doing the activity. This symbol tells you that you will be working with wires and power sources. Take extra care when handling them. This symbol tells you that you will be working with fire. Make sure to tie back loose hair. Take extra care around flames.
In Canada, manufacturers of all hazardous products used in workplaces, including schools, must provide information sheets about their products. The Material Safety Data Sheet (MSDS) identifies the chemical and physical hazards associated with each substance. It includes physical data, such as melting point and boiling point, toxicity, health effects, first aid, and spill and leak cleanup procedures. WHMIS regulations require employers to make these sheets available to employees who use hazardous substances in their work. The above is an example of an MSDS for a substance that you might use in a science activity.
Safety
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Safety
During the Activity 10. Report any safety concerns you have, or hazards you see (such as spills) to your teacher.
17. When you heat test tubes, make sure that the open end is pointing away from you and anyone else in the room.
11. Don’t chew gum, eat, or drink in your science classroom. 12. Never taste anything in science class. 13. Never smell any substance directly. Instead, gently wave your hand over it to bring its vapours toward your nose.
18. When heating a substance, make sure the container does not boil dry.
14. Handle all glassware carefully. If you see cracked or broken glass, ask your teacher how to dispose of it properly. 15. Handle knives and other sharp objects with care. Always cut away from yourself, and never point a sharp object at another person. 16. Heat solids and liquids only in open heatresistant glass containers and test tubes. Use tongs or protective gloves to pick up hot objects.
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19. If any part of your body comes in contact with a chemical, wash the area immediately and thoroughly with water. If you get anything in your eyes, do not touch them. Wash them immediately and continuously with water for 15 min. Inform your teacher. 20. Keep water or wet hands away from electrical outlets or sockets. 21. Use tools safely when cutting, joining, or drilling. Make sure you know how to use any tools properly. 22. Use special care when you are near objects in motion, gears and pulleys, and elevated objects. 23. Make sure equipment is placed safely so that people will not knock it over or trip
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Safety
over it. Report any damaged equipment to your teacher immediately. 24. Treat all living things with respect. Follow your teacher’s instructions when working with living things in the classroom or on a field trip.
When You Finish the Activity 25. Make sure you close the containers of chemicals immediately after you use them.
27. Always wash your hands well with soap, preferably liquid soap, after handling chemicals or other materials. Always wash your hands after touching plants, soil, or any animals and their cages or containers. 28. When you have finished an experiment, clean all the equipment before putting it away. Be careful with hot plates and equipment that have been heated as they may take a long time to cool down.
26. Follow your teacher’s instructions to safely dispose of all waste materials.
Learning Checkpoint Your teacher will give you a copy of an MSDS for bleach solution. Use this MSDS to answer questions 1–8. 1. List three synonyms for the name “bleach.” 2. Bleach solution has two ingredients. What are they? Which of these ingredients is hazardous? 3. Find the hazard identification section. Under “Emergency Overview,” there is a short summary. Find the summary, and record it. 4. Read the list of potential health effects. Copy down the potential health effect caused by eye contact. 5. Find the section under “First Aid Measures,” and record the instructions for what to do in case of eye contact. 6. If a fire were to break out near bleach, should the bleach itself be considered a fire hazard? What special equipment is required to fight a fire in which bleach is present?
7. Suppose someone drank bleach. Should the first aid procedure include inducing vomiting to get the solution out of the person? What other treatments are possible? 8. Find out what is meant by the term “chronic exposure.” 9. Why is it important for all students to follow the safety rules in a science class? 10. List precautions used in the science laboratory to minimize the following risks. (a) poisoning (b) scalding (c) eye damage 11. List the steps you should take before starting a science activity. 12. Draw a sketch of your classroom or science lab indicating the location of all emergency equipment and exits.
Safety
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UNIT
A
Northern leopard frogs like this one were once common in lakes and ponds across North America. In North America and around the world, populations of frogs and toads have been decreasing. Scientists view this gradual disappearance as a sign that the ecosystems these creatures are part of are in trouble. 2
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Sustainable Ecosystems
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Contents 1
Ecosystems are complex, self-regulating systems of organisms and their abiotic environments. 1.1 Ecosystems 1.2 Nutrient Cycles and Energy Flow 1.3 Interactions in Ecosystems
2
DI
Human activity affects the sustainability of ecosystems. 2.1 Human Use of Ecosystems 2.2 Assessing the Impact of Human Activities on Ecosystems DI
3
Governments, groups, and individuals work to promote sustainable ecosystems. 3.1 Government Action to Protect Canada’s Ecosystems 3.2 Environmental Stewardship
DI
Unit Task You will be part of a team that is designing a totally sustainable community to be built in your area. You will look into how resources are currently used in your area and research ways to lessen the impact on your local ecosystems.
Essential Question How do human activities, both positive and negative, affect the sustainability of ecosystems?
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Exploring
Cootes Paradise lies on the edge of the city of Hamilton.
Cootes Paradise By 1985, almost 85 percent of the wetland’s vegetation had disappeared.
Carp like this one invaded Cootes Paradise.
4
UNIT A
Sustainable Ecosystems
The lush green of Cootes Paradise bumps up against the hard edge of the city of Hamilton. Cootes Paradise is a wetland located beside the city of Hamilton. A wetland is an area in which the soil is saturated with water for at least part of the year. Wetlands provide a home for many different species of fish, plants, insects, and birds. Many people also use wetlands for camping, fishing, and wildlife viewing. Pollution and urban development have affected Cootes Paradise, but another factor has taken a toll on the wetland — carp. These fish feed in the shallow waters by pulling up the roots of water plants, damaging the plants and muddying the waters as they go. This makes it difficult for water plants and other fish species to survive. By 1985, almost 85 percent of the wetland’s vegetation had disappeared. This was never supposed to happen. In the 1800s, the federal government stocked the Great Lakes with carp, a fish that is native to Asia. But adult carp have few predators in the Great Lakes, and their populations exploded. As many as 50 000 adult carp used to feed and spawn each year in Cootes Paradise.
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Taking Action In 1993, the municipal government of Hamilton and the local community joined together to take on the challenge of restoring Cootes Paradise. One of the many things they did was to install a fishway at the entrance to Cootes Paradise. It allows small fish to enter the wetland but prevents large fish from entering. The large fish are then captured and inspected. Wetland fish species are returned to Cootes Paradise, but adult carp are not. The fishway project has been a tremendous success, and wetland plant and fish species are recovering.
A1
The fishway at the mouth of Cootes Paradise
STSE Science, Technology, Society, and the Environment
Pesticide Use Across the Country Households Using Pesticides on Lawn or Garden Canada
2006 1994
Canada and Provinces
BC AB SK
(b) Why does each region show two bars? (c) Which one of the regions on the graph is the average of all of the other regions? (d) Which province had the highest pesticide use in 1994? in 2006? (e) Which province had the lowest pesticide use in 1994? in 2006?
MB ON
(f) What percentage of households used pesticides in New Brunswick in 1994?
QC NB
(g) Which province did not change pesticide use over the period of the study?
NS PE
(h) Did pesticide use in Canada increase or decrease between 1994 and 2006?
NF 0
10
20
30
40
50
Percent
Pesticide use by Canadian households
Pesticides are substances used to kill pests, such as dandelions or grubs. Some pesticides do not break down quickly, and they may enter local streams and wetlands, killing wild organisms. In response, some communities have banned the use of pesticides on lawns and gardens. 1. Work with a partner to analyze the information about pesticide use contained in the graph. Use the following questions as a guide. (a) Over what span of time does the graph show pesticide use?
2. An important skill is inferring information from a graph. Consider the following questions. (a) One province put strict limits on pesticide use on lawns after 1994. Infer from the graph which province did this. Be prepared to explain your inference. (b) In 2006, more pesticide was used in Ontario than in Manitoba, Saskatchewan, and Alberta combined. How is this possible given the data in the graph? 3. Banning pesticides may have benefits. Are there any drawbacks to banning pesticides? Are there any people or organizations that might not welcome a pesticide ban? Explain why.
Exploring
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Ecosystems are complex, self-regulating systems of organisms and their abiotic environments.
1
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UNIT A
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Skills You Will Use In this chapter, you will: This woodchuck and the wildflowers are parts of a complex ecological system, a meadow.
• interpret data from undisturbed and disturbed ecosystems and graph the results, and explain the importance of biodiversity for all sustainable ecosystems
Concepts You Will Learn In this chapter, you will: • describe the complementary processes of photosynthesis and cellular respiration with respect to the flow of energy and the cycling of matter within ecosystems, and explain how human activities can disrupt the balance achieved by these processes • describe the limiting factors and explain how these factors affect the carrying capacity of an ecosystem • identify Earth's four spheres (biosphere, hydrosphere, lithosphere, and atmosphere), and describe how these spheres interact to maintain sustainability and biodiversity
Why It Is Important There are many different ecosystems on Earth. If we know how an ecosystem functions as a system, we can analyze how human activities sometimes disrupt ecosystems and make them unsustainable. We can then help to repair or restore ecosystems.
Before Reading Visualize to Understand Good readers picture words and whole phrases of text in their minds. Preview the key terms and main subheadings in section 1.1, and use the words or parts of words you know to begin constructing a picture of ecosystems.
Key Terms • abiotic • atmosphere • biodiversity • biosphere • biotic • carrying capacity • cellular respiration • energy pyramid • equilibrium • hydrosphere • limiting factor • lithosphere • nutrient cycle • photosynthesis • population
Ecosystems are complex, self-regulating systems of organisms and their abiotic environments.
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1.1
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Ecosystems
Here is a summary of what you will learn in this section: • Systems have components that interact. • Ecosystems are systems with abiotic and biotic components that interact. • Ecosystems combine to form biomes, and the biosphere contains all the biomes on Earth. • The biosphere is composed of the atmosphere, the lithosphere, and the hydrosphere.
Figure 1.1 A view of Earth from space
Planet Earth High above the planet, the International Space Station offers a breathtaking view of Earth (Figure 1.1). Canadian astronaut Dave Williams has been privileged to see that view first-hand. After returning to Earth, he had this to say about his experience: “I am truly in awe of the beauty of the planet, and it’s something I’ve been able to experience in so many different environments, whether in space, underwater, camping, hiking, climbing mountains, or whatever. For me, it generates a sense of planetary stewardship.” Stewardship is a way of acting that involves taking personal responsibility for the management and care of something. Planetary stewardship means working to take care of the whole world. A more common term for this is environmental stewardship. The environment is all the living and non-living things that exist on Earth as well as their interactions with each other. The beautiful blue sphere that astronauts have photographed from space helps us to remember that the resources in our environment are limited. All life depends on what is contained on that sphere. While the view from space is new to us, the idea of the importance of environmental stewardship is far from new. 8
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Many cultures, especially those with a history of living close to the land, hold a deep respect for the natural world. For example, Cree and other First Nations teach that the members of each generation must be careful stewards of the Earth to ensure the survival of at least the next seven generations. For this to be possible, the natural environment must be used in a sustainable way. Sustainability in the environment means that populations of plants, animals, and other living organisms can continue to interact and to reproduce indefinitely. It also means that biodiversity is preserved. Biodiversity is the number of different types of organisms in an area. The more types of organisms there are in an area, the more biodiversity the area has. High levels of biodiversity are associated with a healthy, sustainable environment.
W O R D S M AT T E R
“Bio-” is a prefix derived from the Greek word bios, which means life.
A2 Quick Lab Representing Earth’s Biodiversity There are many different types of organisms on Earth. To study Earth’s biodiversity, similar species are placed into categories. For example, foxes, bears, and mice can be grouped under “mammals.” In this activity, you will make a visual representation of the 14 categories of organisms shown in Table 1.1. Table 1.1 Earth’s Biodiversity Category Mammals (e.g., deer)
Number of Species 4 500
Reptiles and amphibians (e.g., snake, frog)
10 500
Fish (e.g., trout)
22 000
Crustaceans (e.g., shrimp)
40 000
Molluscs (e.g., clam)
70 000
Sponges (e.g., glass sponge)
10 000
Birds (e.g., crow)
10 000
Insects (e.g., fly)
963 000
Arachnids (e.g., spider)
75 000
Plants (e.g., cherry tree)
270 000
Purpose To visually represent the numbers of each group of organisms living on Earth
Procedure 1. Work with a partner to brainstorm a method of representing the numbers of each type of organism in a visual way. It may be a twodimensional representation such as a graph, or a three-dimensional model. 2. Once you have decided on a method, check with your teacher, and then create your representation.
Questions 3. Look for and try to explain any relationship you can find between the numbers of species in a group and the type of organisms that are in that group. 4. Compare your representation with that of other students in your class. Which features of each model did you like best, and which could be improved? 5. How could you improve your representation?
Fungi and lichens (e.g., mushroom)
100 000
Ecosystems are complex, self-regulating systems of organisms and their abiotic environments.
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Systems in the Environment Imagine a wild bee moving from flower to flower on a spring day. The bee busily visits many flowers, then, suddenly, it darts back to its hive (Figure 1.2). There, it unloads the tiny drop of nectar that it has gathered on its journey. This activity seems very straightforward: the bee is simply collecting food for itself and its hive.
Figure 1.2 Bees visit flowers to collect nectar, which they convert into honey at the hive.
During Reading Little Pictures Lead to the Big Picture The story of the bee helps you to understand the larger picture of how organisms interact within a system. Draw and label a picture in your mind as you read about the bee, the hive, and flowering plants. How does this picture help you to understand the concept of ecological systems?
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However, there is something more to this interaction between the bee and the flower. Producing flowers and nectar takes a lot of energy and resources. Yet flowering plants produce vast numbers of colourful and fragrant flowers, each stocked with nectar to attract bees and other animals. The answer is that pollinators such as bees help plants to reproduce. In order to produce seeds, most flowers need to be fertilized with pollen from another plant. The plants cannot move to get the pollen. That is where bees and other pollinators come in. When a bee visits a flower to get nectar, pollen sticks to its fuzzy coat. When it visits another flower, the pollen on its coat fertilizes the flower. Once fertilized, the flower can produce seeds, which will eventually grow into the next generation of plants.
Systems Have Components and Interactions A bee fertilizing a flower is an example of an interaction between different organisms. Such interactions are not always positive. If you have ever been stung by a bee, then you know that the interaction between you and the bee is painful. The bee also dies once it has stung you. It may seem that you and the bee both lose
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in this interaction, but this is not necessarily the case. The bee may have successfully defended its hive by encouraging you to move away from the area. You may even have benefitted if the sting prevented you from accidentally walking right into the hive, risking hundreds more stings. A system is a group of individual parts that interact as a whole to accomplish a task. The parts of a system are called components. For example, a bicycle is a mechanical system (Figure 1.3). All of the components of a bicycle interact to do something that none of the parts can do alone, which is to move the rider along a road. Systems exist in the natural world as well. Returning to the bee example, think of all the interactions that happen in the life of a worker bee. The worker supports the hive by building it, bringing in nectar, or defending the entrances to the hive. These interactions give the drones, the male bees, a place to live until the queen bee needs to mate with them. The queen bee’s role is to produce eggs. Each bee is driven by instinct to perform various tasks. The result of all the individual bees’ interactions is a complex and self-sustaining system: the hive.
Figure 1.3 The wheels, chain, pedals, and the rider interact to perform a task: movement.
A Holistic Approach Although ecologists have to identify the components of ecological systems, such as water temperature and the number of fish, they also have to take a holistic approach as well. In a holistic approach, the entire system is emphasized. If you took a bicycle apart and just looked at all the pieces, you could know everything about all the parts and yet still not know that a bicycle’s function is to move a rider along a road (Figure 1.4). This is because “riding” is not something that has meaning to any of the individual parts. It has meaning only when the system — all the bicycle parts, including the rider — is considered as a whole. The same is true in the study of the environment. Many Aboriginal ways of knowing have long taught the importance of a holistic approach to the environment. Many Aboriginal people believe that everything is connected through interactions. They also take the view that we are all part of the environment that we live in. Figure 1.4 The individual parts of a bicycle give you no clue about These beliefs result in a deep respect for Earth. how they work as a whole. Ecosystems are complex, self-regulating systems of organisms and their abiotic environments.
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Figure 1.5 The more components a system has, the more complex the system becomes. A coral reef is a very complex system.
Traditional ways of living require that everything in nature, from water to organisms, be treated with respect and used wisely.
Ecological Systems Are Complex Ecology is the study of how organisms interact with each other as well as with their environment. A person who studies ecology is called an ecologist. Consider, for example, how an ecologist might study a coral reef. Coral reefs are one of the world’s most important and sensitive ecological systems (Figure 1.5). An ecologist might want to find out such things as which kinds of fish live there permanently, and which stay for short periods and then leave. They might also study the physical parts of the system, such as the amount of salt dissolved in the water or the water temperature, and how they affect reef organisms. Currently, ecologists are examining how reefs respond to rising water temperatures. Early results suggest that warmer water can be very harmful to a reef. It is often impossible to predict what will happen when one component changes because the components of the system are so interconnected. A coral reef has a large number of components and an even larger number of interactions. Most ecological systems are similarly complex. 12
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Learning Checkpoint 1. Explain what is meant by each of the following terms. (a) stewardship (b) environment (c) sustainability (d) biodiversity 2. List three possible interactions between a bee and its environment. 3. What is meant by the term “system”? How are a bicycle and a rider a kind of system? 4. Ecology can be described as a holistic science. Explain why this is the case.
Elements of Ecosystems An ecosystem is a complex, self-regulating system in which living things interact with each other and with non-living things. Self-regulating means that the interactions keep the ecosystem healthy and sustainable. In order to analyze how ecosystems function, ecologists classify all parts, or factors, of ecosystems as either biotic or abiotic. Biotic factors are organisms, such as animals, plants, fungi, bacteria, and algae. Abiotic factors are everything else (Figure 1.6). Abiotic factors can be physical things, such as rocks, air, and water. Abiotic factors can also be things that are measured, such as air temperature, hours of daylight, and salt concentration in seawater. It is the interactions of the biotic and abiotic elements that help keep the ecosystem self-regulating.
Figure 1.6 The abiotic components in this pond ecosystem include water, air, and dead branches. The biotic components include reeds, bushes, and the duck. Ecosystems are complex, self-regulating systems of organisms and their abiotic environments.
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Ecosystems Have Communities A species is a group of similar organisms in an ecosystem. Members of a species can reproduce with each other, and their offspring can reproduce. For example, the grey squirrel is widespread throughout Ontario (Figure 1.7 (a)). All grey squirrels are members of the same species. They can reproduce with each other but not with red squirrels, which also live in Ontario. A population is a group of members of the same species that live in the same area (Figure 1.7 (b)). The physical environment of an organism is its habitat. Suggested Activity • A3 Quick Lab on page 20
(a)
(b)
Figure 1.7 (a) A single grey squirrel is a member of the grey squirrel species. (b) A group of grey squirrels living in the same area form a population.
All grey squirrels are part of the same species, but they are not all part of the same population. For example, one group of grey squirrels might live in a pine forest, while another might live in a park in the next valley over. These two groups of squirrels are two different populations. A community is made up of populations of different species that live and interact in an area. For example, a park contains populations of squirrels, robins, trees, and shrubs (Figure 1.8). The interactions of the populations with each other and with the local abiotic factors make up the ecosystem. All the interactions of a given species with its ecosystem form the species’ niche. For example, the niche of grey squirrels
Figure 1.8 Populations of different species living in the same area form a community.
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includes eating nuts and other seeds, being hunted by foxes and owls, being active during the day, and living and nesting in trees.
Ecosystems Come in All Sizes Ecosystems vary widely in size. They can be as tiny as a drop of water or as large as a desert or an entire ocean. The size of an ecosystem is not the most important thing about it. What really matters for it to be sustainable is that it is a complete system. Consider a single drop of water resting on the needle of a fir tree (Figure 1.9). This drop contains millions of tiny organisms, such as bacteria and microscopic algae. These are the biotic components of the ecosystem. The drop contains matter that the bacteria absorb to help them live. The drop also receives sunlight, which is a source of energy that makes it possible for the bacteria to use the matter and to grow. Matter and sunlight are some of the abiotic components of the ecosystem. Even as new bacteria are produced, others die. The matter in the dead bacteria can be recycled. The recycled matter then provides nourishment for the living bacteria. There can be many interactions between biotic components in the drop. For example, there are probably many different kinds of bacteria in the drop, and they often compete with each other for resources. Some bacteria may eat other bacteria. Other types of bacteria may group together under difficult conditions, such as when the water drop dries out between rainfalls.
Figure 1.9 If the bacteria in the drop of water interact with the water, light, and other abiotic factors, the drop is an ecosystem, even though it may be temporary.
Ecosystems Combine to Make Biomes Ecosystems can exist within larger ecosystems. For example, a stream is composed of fresh water, rocks, crayfish, fish, and various types of plants. All these abiotic and biotic factors interact as a unit. Suppose, however, that this stream runs through a forest (Figure 1.10). Animals that live in the forest drink and catch fish from the stream, and certain trees, such as cedars, grow along the banks of the stream. Because the forest plants and animals interact with the stream ecosystem, the stream is also part of the forest ecosystem. A single rotting log on
Figure 1.10 This forest ecosystem contains a stream ecosystem and many other smaller ecosystems.
Ecosystems are complex, self-regulating systems of organisms and their abiotic environments.
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the forest floor is an ecosystem as well because the organisms that live in or on the log interact with one another and with the non-living log. It too is part of the forest ecosystem. All these ecosystems are interconnected. The forest ecosystem is part of a larger region that contains many similar forests. Similarly, the small stream feeds into a larger river, which is another ecosystem. The river eventually feeds into an ocean, which contains many more ecosystems. A biome is a large geographical region that contains similar ecosystems. On land, biomes are defined by the types of plants that grow in them. They are also classified according to the average temperature and the amount of rainfall. Because the ecosystems in a biome usually have similar plants, animals, and weather and
(a)
(b)
(c)
(d)
Figure 1.11 Canadian terrestrial biomes include (a) deciduous forest, (b) boreal forest, (c) tundra, (d) grassland, and (e) temperate coniferous forest. Abiotic factors, such as the amount of rainfall and the average temperature, determine what types of vegetation exist in each biome.
(e)
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receive similar amounts of precipitation, it can be very helpful in the study of an ecosystem to know which biome it is in. Biomes are often divided into those on land and those in water. Throughout the world there are many types of biomes. In Canada, there are five major land, or terrestrial, biomes (Figure 1.11). Terrestrial Biomes Canada’s five main terrestrial biomes are defined by their dominant vegetation.
• Deciduous forests have trees that lose their leaves in the autumn, such as maples and oaks. Southern Ontario is mainly a deciduous forest biome. • Boreal forests (also known as taiga) have trees that have cones and needles, such as spruce and fir. Most of northern Ontario is covered with boreal forests. • Tundra has no trees, only small shrubs, hardy grasses, mosses, and lichens. Even some flowers such as crocuses grow here. Ontario’s northern coastline on Hudson Bay, to the west of James Bay, is tundra. • Grasslands have few trees but are covered in various kinds of grasses and shrubs. Ontario has very few grasslands. They are found in Manitoba, Saskatchewan, and a small part of Alberta. • Temperate coniferous forests have different types of needle- and cone-bearing trees than the boreal forest: Douglas fir, Sitka spruce, and western hemlock. Most of western British Columbia is temperate coniferous forest. Aquatic Biomes Water-based, or aquatic, biomes fall under two main categories: marine and freshwater (Figure 1.12). The water in marine biomes has a high salt content, and the water in freshwater biomes has a very low salt content.
(a)
• Marine biomes are found in the oceans. Coral reefs, the ocean floor, the open ocean, and the intertidal zones are marine biomes. Ontario has marine biomes along Hudson Bay and James Bay. • Freshwater biomes include lakes, streams, rivers, and wetlands. Some of Ontario’s lakes and rivers are huge, such as the Great Lakes and the St. Lawrence River. Ontario has countless smaller lakes, streams, and wetlands.
(b) Figure 1.12 Two aquatic biomes. (a) A lake is a freshwater biome. (b) The open ocean of Hudson Bay is a marine biome.
Ecosystems are complex, self-regulating systems of organisms and their abiotic environments.
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Biomes Combine to Make the Biosphere This section began with a view of Earth from space. With the whole planet in view, the idea of promoting stewardship and sustainability becomes urgent because we can see that the resources of Earth are limited. We also now know that Earth’s biotic and abiotic factors interact in ecosystems. Ecosystems can be large or small, and they overlap and interconnect. The very largest of these ecosystems, the biomes, combine to make a planetary system. It is the most important system on Earth, and it is our home. It is called the biosphere (Figure 1.13). The biosphere is the part of the planet, including water, land, and air, where life exists. It is very thin relative to the whole Earth. If Earth were represented by a beach ball, the biosphere could be represented by a sheet of plastic wrap laid over its surface one layer thick. Three main interacting components make up the physical environment of the biosphere. They are the atmosphere, the lithosphere, and the hydrosphere (Figure 1.14).
60˚N N
30˚N
equator 0˚
30˚S 0
1500
3000 km
60˚S
tropical rainforest
temperate grassland
temperate deciduous forest
tundra
tropical dry forest
desert
boreal forest (taiga)
tropical savanna
temperate woodland and shrubland
temperate coniferous forest
mountains and icecaps
Figure 1.13 Earth’s major terrestrial biomes. These biomes, plus the ocean biomes, contain all life on Earth. The biosphere is the part of Earth that contains all the world’s biomes.
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Take It Further Around the world there are several other major types of terrestrial biomes, including more forest biomes. Find out more about the world’s biomes. Begin your research at ScienceSource.
atmosphere
biosphere
lithosphere
hydrosphere
Figure 1.14 The biosphere is composed of all living things on Earth and the physical environment that surrounds them.
• The atmosphere is the layer of gases that surrounds Earth. Water vapour and carbon dioxide in the atmosphere absorb sunlight and retain the Sun’s energy as heat, warming the planet to temperatures suitable for life. The lower atmosphere contains oxygen, which many organisms need to survive, while the upper atmosphere contains a different form of oxygen called ozone. Ozone protects organisms in the biosphere from the Sun’s harmful ultraviolet radiation. • The lithosphere is Earth’s solid, outer layer. It includes the rigid crust and the upper mantle, which lies directly below the crust. The lithosphere extends 100 km down from the surface and runs under the continents and oceans. It includes the soil, which is home to many micro-organisms, plants, animals, and fungi. • The hydrosphere is all the water on Earth. About 97 percent of this water is salt water in Earth’s oceans. The other 3 percent is fresh water and includes water in lakes and streams and the ice and snow in glaciers. All living organisms need water, and so they depend on the hydrosphere.
Ecosystems are complex, self-regulating systems of organisms and their abiotic environments.
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A3 Quick Lab Natural Versus Artificial
Figure 1.16 A flower garden
Figure 1.15 A forest
A forest and a flower garden are located in the same area. One is a natural ecosystem, and the other is an artificial ecosystem.
Purpose To determine the differences between artificial and natural ecosystems
Procedure 1. Create a tally chart like the one in Figure 1.17. Forest
Garden
Figure 1.17
2. Examine the forest ecosystem in Figure 1.15. For each species you find, put a tally mark in the tally chart.
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3. Repeat step 2 for the garden ecosystem in Figure 1.16. 4. Create a bar graph that shows both the garden’s and the forest’s biodiversity.
Questions 5. Which ecosystem has more biodiversity? How do you know? 6. What things do you think humans do in the flower garden to alter the abiotic elements of the ecosystem? What effects do these actions have, if any, on biodiversity? 7. What things do humans do in the flower garden that alter the biotic elements of the ecosystem? What effects do they have on biodiversity?
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CHECK and REFLECT 15. Examine the ecosystem in the photograph below.
Key Concept Review 1. What is an ecosystem? 2. What is biodiversity a measure of? 3. What are the characteristics of a sustainable ecosystem? 4. Do biomes contain ecosystems, or do ecosystems contain biomes? Explain your answer.
(a) Identify three abiotic factors that are part of this ecosystem. (b) Identify three biotic factors that are a part of the ecosystem.
5. What is ecology? 6. What is the difference between a biotic and an abiotic component of an ecosystem? 7. How do marine biomes differ from freshwater biomes? 8. Explain what a population is. 9. What are the three components that support the biosphere?
Connect Your Understanding Question 15
10. You interact with abiotic and biotic parts of your environment every day.
11. What abiotic factors may affect the growth of an oak tree in an Ontario forest?
16. An analogy is a comparison between two different things that are alike in some ways, but different in others. In this section, a bicycle was an analogy used to identify some of the characteristics of an ecosystem. Create another analogy that shows some of the characteristics of an ecosystem.
12. If you travelled north from southern Ontario to the Arctic, you would pass through several biomes. How would the vegetation change during this trip?
17. Ecologists must understand the components that make up an ecosystem. Ecologists have to take a holistic view. Explain how both of these statements are true.
13. A stream is an aquatic ecosystem, but it can also be part of a forest ecosystem at the same time. Explain how this is possible.
Reflection
(a) List five abiotic factors in your environment. (b) List five biotic factors in your environment.
14. Our planet has been referred to as Spaceship Earth. Explain how this might be an effective way to describe our planet.
18. Describe three things you did not know about ecosystems before you started working on this chapter. For more questions, go to ScienceSource.
Ecosystems are complex, self-regulating systems of organisms and their abiotic environments.
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Nutrient Cycles and Energy Flow
Here is a summary of what you will learn in this section: • Nutrients move through ecosystems in cycles. • Energy enters ecosystems through photosynthesis, is transferred through cellular respiration, and is eventually lost as heat. • Producers, consumers, and decomposers are related through food webs and energy pyramids.
Figure 1.18 The wildebeests are wary of the dangers hidden in the water.
A Great Migration At the end of each summer in Tanzania, Africa, a great migration begins. Over 1 million wildebeests move across the Serengeti Plain in search of food. They move north to Kenya, where rains have watered the plain and lush grasses have emerged from the moist soil. The wildebeests’ need for food is so strong that they risk their lives to swim across rivers to get to greener pastures (Figure 1.18). Drowning is not the only danger. The wildebeests also risk being eaten by crocodiles (Figure 1.19). All organisms need food to survive. Animals must eat other organisms to survive. The wildebeests eat grasses, and the crocodiles eat some of the wildebeests. Grass and wildebeests are examples of food. Food contains nutrients. Nutrients are substances that an organism uses to build and repair the cells of its body. Plants generally draw nutrients up from the soil and extract them from the air. They use sunlight and nutrients to make their own food. In addition to nutrients, food contains energy, which Figure 1.19 Crocodiles remain under the surface of all organisms need to grow and maintain their bodies the cloudy water and ambush wildebeests that enter the water. and to reproduce. 22
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When a crocodile eats a wildebeest, some of the matter in the wildebeest becomes part of the crocodile. When the crocodile dies, some of its body ends up becoming part of the soil. Since grasses get some of their nutrients from the soil, the matter has come full circle. However, energy usually enters the ecosystem as sunlight and leaves it as heat. It is not recycled.
A4 Quick Lab Finding the Relationships Among Organisms Purpose
Questions
To determine the relationships among organisms
Procedure 1. Study the organisms shown in Figure 1.20. Create a mind map to show how these organisms relate to one another. Once you have finished, share your map with a partner and explain why you made the connections you did.
2. Which organisms have the most connections in your mind map? 3. A photo of one very important component is missing. Can you figure out what it is? 4. Remove one of the organisms from your mind map. Describe the ways this would affect the community of organisms.
4400ⴛ Figure 1.20
Ecosystems are complex, self-regulating systems of organisms and their abiotic environments.
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Table 1.2 Examples of Nutrients Nutrient
Examples
carbohydrate
bread, rice, sugar
fats and oils
butter, corn oil
protein
beans, chicken
vitamins
vitamin C, vitamin D
minerals
calcium, potassium
Figure 1.21 The sugar that makes an orange sweet is a carbohydrate.
Suggested Activity • A5 Quick Lab on page 33
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Nutrient Cycles The nutrients in the food you eat provide energy and matter that your body needs to stay alive. Every living organism needs nutrients to carry out life functions. Nutrients include carbohydrates, fats and oils, proteins, vitamins, and minerals (Table 1.2). Nutrients are made up of elements, which are pure substances that cannot be broken down into simpler substances. For example, sugar, a carbohydrate, is made from the elements carbon, oxygen, and hydrogen (Figure 1.21). Water is made from the elements oxygen and hydrogen. The element nitrogen is a part of proteins. In fact, 95 percent of our bodies are made up of just four elements: carbon, oxygen, hydrogen, and nitrogen. Humans and other animals obtain the carbon, hydrogen, oxygen, and nitrogen they need from eating carbohydrates, fats, and proteins. Plants obtain them by absorbing carbon dioxide from the air and water and substances called nitrates from the soil. Nutrients cycle back and forth between the biotic parts of ecosystems (organisms) and the abiotic parts of ecosystems. The process of moving a nutrient back and forth is called a nutrient cycle. For example, carbon dioxide is exhaled by a wildebeest. The carbon contained in the carbon dioxide is now in the atmosphere, an abiotic part of the ecosystem. The carbon dioxide is then absorbed by a grass plant, and the carbon particle it contains becomes part of a carbohydrate in the grass’s cells. The carbon is now once again in the biotic part of the ecosystem. Sometimes matter can cycle back and forth between the biotic and abiotic parts of an ecosystem fairly quickly. Sometimes matter can remain in one place for a long time. For example, the ice in glaciers has been there for thousands of years. Any place where matter accumulates is called a reservoir. The cycles that water, carbon, and nitrogen follow all have reservoirs.
The Water Cycle Water is a substance that moves in a cycle. A cycle has no beginning or end. In the water cycle, water is moved throughout the whole biosphere. The Sun’s heat warms the surface water, and the water evaporates into the atmosphere (Figure 1.22). In the atmosphere, the water exists as a gas, called water vapour. As the water vapour cools, it condenses to form clouds. From there, it may fall to Earth as rain, hail, snow, or sleet. If it falls to the ground, it will tend to run off the surface into nearby streams 24
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or rivers. This water is called run-off. Some water seeps down through the soil into the ground water. Some ground water may flow into large underground lakes, known as aquifers, while some may flow into other bodies of water such as wetlands or oceans. Some of the water on the surface or in the soil is taken up by animals and plants. Plants play a major role in the water cycle through a process known as transpiration. Transpiration occurs when plants release water vapour into the atmosphere through their leaves. The water vapour rises into the atmosphere, and the cycle continues.
condensation precipitation
transpiration
evaporation
run-off lake seepage
nd rou
ter
wa
g
ifer
ocean
aqu root uptake
Figure 1.22 The water cycle
The Nitrogen Cycle All organisms need nitrogen to make proteins. Nitrogen also moves in a cycle. Nitrogen gas makes up 78 percent of the atmosphere, but it cannot be used directly by most organisms. They get their nitrogen from substances such as ammonia that contain nitrogen. Converting nitrogen gas into ammonia is called nitrogen fixation. Nitrogen-fixing bacteria perform this critical step. Without these bacteria, movement of nitrogen would stop almost completely. Lightning is the only other natural nitrogen-fixing process. It accounts for only about 1 percent of the world’s nitrogen fixation. Ecosystems are complex, self-regulating systems of organisms and their abiotic environments.
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Plants called legumes (peas, beans, and alfalfa) have nodules on their roots that contain nitrogen-fixing bacteria. The bacteria supply usable nitrogen directly to the plant. Nitrogen-fixing bacteria also live freely in the soil and water (Figure 1.23). Most plants cannot use the ammonia these bacteria produce. Nitrifying bacteria convert ammonia into nitrites and then nitrates, which plants absorb through their roots. Animals get the nitrogen they need by eating plants or animals. When animals digest proteins, a by-product is ammonia. Ammonia is toxic to animals, and they get rid of it in their wastes. Bacteria and fungi in the soil break down the ammonia in wastes and dead organisms into nitrates and nitrites and release them into the soil where they can be absorbed by plants. Denitrifying bacteria in the soil convert nitrates back into nitrogen gas, which returns to the atmosphere.
nitrogen in atmosphere
uptake
Figure 1.23 The nitrogen cycle nitrates
nitrogen-fixing bacteria in root nodules of legumes
denitrifying bacteria
decomposers ammonification
nitrites
ammonia nitrogen-fixing bacteria in soil
nitrifying bacteria
nitrification
nitrifying bacteria
The Carbon Cycle All living things contain carbon. Carbon dioxide gas contains carbon. Although carbon dioxide makes up only 0.04 percent of the gases in the atmosphere, it is from this that all plants get the carbon they need to grow. For example, a tall oak tree is both massive and solid. A large portion of the matter in the tree is made of carbon, and all of the carbon came from the atmosphere. The world’s forests are biotic reservoirs of carbon (Figure 1.24). 26
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CO2 in atmosphere photosynthesis photosynthesis cellular respiration
burning of fossil fuels and wood
primary consumers
phytoplankton
carbon compounds in water
plants
higher-level consumers
Figure 1.24 The carbon cycle
decomposers dead organisms
fossil fuels
A huge carbon reservoir sits underground locked up in deposits of coal, which are almost pure carbon, oil, and natural gas which are mostly carbon combined with hydrogen. These deposits were formed from the remains of huge forests that lived hundreds of millions of years ago. Because oil, natural gas, and coal were formed so long ago, they are called fossil fuels. The other abiotic carbon reservoir is the oceans. Carbon dioxide dissolves in water. Marine organisms use the carbon from the dissolved carbon dioxide to build their tissues. Many natural processes move carbon between these various carbon reservoirs. Two of the most important processes are photosynthesis and respiration. Not only are both of these processes central to nutrient cycles, they are also closely connected with the flow of energy through ecosystems.
Learning Checkpoint 1. Explain what is meant by each of the following terms. (a) nutrient (b) element 2. Give an example of the possible steps in a water cycle where water leaves an ocean, moves to land, and then returns to an ocean. 3. What are the types of bacteria involved in the nitrogen cycle? 4. List one biotic and one abiotic reservoir for the element carbon. Ecosystems are complex, self-regulating systems of organisms and their abiotic environments.
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Energy Flows Through Ecosystems The ultimate source of energy for Earth’s ecosystems is the Sun. A small fraction of the sunlight that reaches Earth is absorbed by the substance that causes plant leaves to be green. This substance is called chlorophyll. Plants use chlorophyll to capture the energy in sunlight and convert it into chemical energy. They then use the chemical energy for all the processes in their cells.
Photosynthesis The process plants use to capture the energy in sunlight is complex (Figure 1.25). Plants absorb the chemical carbon dioxide gas and combine it chemically with water to produce a third chemical called glucose. Glucose is actually a form of sugar. All sugars are carbohydrates. Carbohydrates contain energy. The process of producing carbohydrates from carbon dioxide, water, and sunlight is called photosynthesis. Photosynthesis can be written out in the form of a short statement, usually called a word equation, as follows: carbon dioxide gas + water + sunlight glucose + oxygen gas
Photosynthesis Sun
Oxygen is released as a product of photosynthesis. light
Light energy drives the reaction.
glucose made in leaf
carbon dioxide cells form glucose
carbon dioxide from the atmosphere
oxygen
water water from the soil Figure 1.25 Photosynthesis
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Carbon dioxide gas and water are shown to the left of the arrow because they are being used, along with sunlight, to make glucose and oxygen gas, shown to the right of the arrow. The plant releases some of the oxygen gas into the atmosphere, and it uses the rest of it to extract the energy from the glucose. The plant then uses the energy for the processes in its cells. When you breathe, it is the oxygen gas in the air that keeps you alive. About 21 percent of the atmosphere is made of oxygen, and almost all of it was produced through photosynthesis. The trees in the world’s forest biomes and algae in the marine biomes produce most of the world’s oxygen (Figure 1.26).
300ⴛ Figure 1.26 Microscopic marine algae
Cellular Respiration Plants store the energy they capture from the Sun through photosynthesis in the form of glucose. However, plants need a continuous supply of energy for functions such as growth, repair of tissues, and reproduction. The process plants use to obtain the energy from the glucose is called cellular respiration. In cellular respiration, glucose combines chemically with oxygen from the air, in what looks like almost the reverse of photosynthesis. The equation for it is: glucose + oxygen gas carbon dioxide gas + water + energy
Plants use the energy released by cellular respiration for all the processes inside their cells. Animals also carry out cellular respiration. Since they cannot carry out photosynthesis, they must obtain glucose by eating food containing carbohydrates. The equation also shows why we need to breathe. Breathing supplies oxygen needed for cellular respiration (Figure 1.27).
Figure 1.27 When we breathe out, we are getting rid of carbon dioxide, one of the products of cellular respiration.
Learning Checkpoint 1. What is the role of photosynthesis in an ecosystem? 2. What substances are produced and consumed in photosynthesis? 3. How are photosynthesis and cellular respiration related? 4. Since plants can capture the energy of sunlight in photosynthesis, why do plants need cellular respiration?
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Producers and Consumers
During Reading Picture Mapping As you read about producers and consumers, draw pictures with arrows to confirm your understanding of how producers and consumers connect.
Producers are organisms that carry out photosynthesis. Terrestrial and aquatic plants, algae, and other organisms are producers. Producers are critical to ecosystems because they bring the Sun’s energy into biological systems and turn it into chemical energy that plants can use. Consumers are organisms that eat other organisms to obtain energy because they cannot produce their own food. There are several types of consumers. For example, a caterpillar is a primary consumer because it eats producers. A robin is a secondary consumer because it feeds on primary consumers. The third level of consumer, which eats secondary consumers, is called a tertiary consumer. For example, a hawk or eagle that feeds on a robin would be a tertiary consumer. Because primary consumers always eat plants, they are called herbivores. For example, moose and deer are herbivores. Other consumers eat meat. If they eat mostly meat, they are called carnivores. Scavengers are carnivores that eat the remains of dead animals. Vultures are scavengers. Some consumers eat both animals and plants. They are called omnivores. Bears, raccoons and many humans are omnivores. Detritivores are consumers that feed on organic matter. Organic matter is the remains of dead organisms and animal wastes. Earthworms and maggots are detritivores. Animals that catch and feed on other live animals are called predators. Animals that the hunter catches are called prey. For example, when a robin eats a worm, the robin is the predator and the worm is the prey. However, if a hawk hunts a robin for food, then the robin is the prey.
Decomposers There is a group of special consumers called decomposers. The role of decomposers is to break down organic matter and release the nutrients in the organic matter back into the ecosystem. The major decomposers are fungi and bacteria (Figure 1.28). They do not consume the organic matter directly. Instead, they release special chemicals, called enzymes, into the organic matter to break it down. They then absorb the nutrients that are released.
Figure 1.28 This fungus is feeding on the organic matter in the soil. As it does, nutrients in the organic matter are released into the soil.
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Food Chains and Food Webs Food chains are a way of showing feeding relationships among organisms. They start with a producer and end with a final consumer (Figure 1.29).
algae
water flea
damselfly nymph
frog
Figure 1.29 An aquatic food chain
However, most consumers usually eat many different types of food. For example, a snowshoe hare eats willow, bog birch, and many other green plants. A fox eats snowshoe hares as well as squirrels, voles, ptarmigan, and many other animals. These complicated feeding relationships can be modelled with a food web, as in Figure 1.30.
Canadian lynx
grey wolf
great horned owl red fox grey jay
red squirrel
beetle
moose spruce grouse
white spruce
snowshoe hare
bog birch
bunchberry
Figure 1.30 This food web of a boreal forest shows how different food chains interconnect.
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Both food webs and food chains are limited in the information that they provide. They both clearly show who eats what, but they do not show how much energy is being passed from one organism to the next. Energy pyramids help us understand the flow of energy through ecosystems.
Energy Pyramids Suggested Activity • A6 Quick Lab on page 34
100 J eaten
60 J
10 J 30 J
passed out in waste
stored in body tissue
used in body processes
Figure 1.31 Of the 100 J the caterpillar eats, only 10 J is stored in its tissues. Only the energy stored in the caterpillar’s tissues is available to the animal that eats it.
Generally, when an animal eats, 60 percent of the energy contained in the food cannot be accessed by the animal and it passes out of the organism in its wastes (Figure 1.31). Thirty percent of the energy is used to run cellular processes. Only about 10 percent of the energy in the food is used to make body tissues such as bones, muscles, and fat. This is very important when tracing the path of usable energy through a food web. It means that only about 10 percent of the energy that the animal eats is available to pass on to an animal that eats it. Put another way, as energy moves along a food chain, about 90 percent of the energy is lost at each transfer, most of it as heat. Energy pyramids show the amount of available energy the producers and consumers contain as energy flows through the ecosystem (Figure 1.32). The more levels that exist between the producers and the top-level consumer in an ecosystem, the less energy is left from the original amount provided by the producers. Energy pyramids also show how important producers are to ecosystems. The wider the base of the pyramid, the more energy producers provide to the consumers.
10 J
100 J
1 000 J
Take It Further Other types of ecological pyramids are pyramids of numbers and pyramids of biomass. Find out what these pyramids model. Begin your research at ScienceSource.
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10 000 J
Figure 1.32 An energy pyramid shows the flow of energy through an ecosystem. The top level shows the amount of energy from the bottom level that is still available.
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A5 Quick Lab Analyzing Cycles Figure 1.33 demonstrates how nutrients cycle in an ecosystem. Different nutrients all follow the same general path.
Questions 4. Suggest the ways in which a nutrient moves: (a) from the ocean to the atmosphere
Purpose
(b) from the land to the ocean
To observe the path of nutrients as they move through the atmosphere, lithosphere, hydrosphere, and biosphere
5. If the ocean were removed from this diagram, how would this affect the flow of nutrients? 6. How do producers, consumers, and decomposers contribute to nutrient cycles?
Procedure 1. With a partner, study Figure 1.33. 2. Discuss any patterns that you observe. 3. Even though a nutrient moves through the ecosystem, there are certain locations where it may be stored for a period of time. Identify these locations.
7. Notice that the arrows are all the same width. However, this is not a completely accurate representation of nutrient flow. If a wide arrow represented a high level of flow and a thin arrow represented a low level of flow, which arrows would you make thicker and which arrows would you make thinner? 8. What abiotic factors do you think might affect the cycle (temperature, wind, rain, sunlight)? In what way would each one affect the cycle?
atmosphere
land producers
consumers
oceans
producers
consumers
decomposers to deep stores (takes millions of years)
decomposers
marine sediments and sedimentary rock
nutrient flows (exchanges) natural processes nutrient reservoirs
Figure 1.33 A general nutrient cycle
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A6 Quick Lab Comparing Energy Pyramids Purpose To create and compare energy pyramids for two different ecosystems: a deciduous forest and a boreal forest
Materials & Equipment • calculator
• glue
• eight 2-cm strips of coloured paper
• scissors
• ruler
• blank sheet of paper
6. Repeat step 5 for the remaining levels of the pyramid. If you could not cut a narrow enough strip, use a pencil to draw a 2-cm vertical line and indicate the width, in millimetres, that the line represents. 7. Glue the strips horizontally one above the other to form a pyramid. Make sure that the producer strip forms the base of the pyramid and that the tertiary consumer strip forms the top. 8. Label each level of the pyramid. Give the pyramid a title.
Procedure 1. Copy Table 1.3 into your notebook and write 30 000 for Producers under the “Energy Present” column. This table will be for the deciduous forest.
Energy Present (kJ/m2)
9. Repeat steps 1 to 6 for the boreal forest. (For step 1, write 12 000 for Producers under the “Energy Present” column.) 10. Glue the strips onto the same page below the deciduous forest pyramid.
Table 1.3 Energy Pyramid Data
Producers
5. Cut a strip of paper to the correct length for the producer level of the pyramid.
Length of Paper Strip (mm)
30 000
11. Label each level of the second pyramid, and give the second pyramid a title.
Questions
Primary consumers Secondary consumers Tertiary consumers
2. Remember that only 10 percent of the energy in producers is available to the primary consumers that eat the producers. Calculate the amount of energy available to the primary consumers. Record the value in your table. 3. Calculate the amount of energy available to the secondary consumers and tertiary consumers, and record the values in the table. 4. To create the energy pyramid, you will need to use a scale for your model so that 10 mm equals 2000 kJ/m2. Calculate the length, in millimetres, of paper strips you will need to represent each level of the pyramid. Record the values in your table.
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12. Compared to the height of each pyramid, are the bases relatively large or small? What does this mean about the way energy flows through the ecosystem? 13. Which forest has more energy available to the primary consumers? More energy available to the tertiary consumers? 14. Explain what happens to the energy that is not transferred at each level of the pyramid. 15. Write a statement comparing energy availability in boreal and deciduous forests. 16. Suppose half of the deciduous forest was cut down and not replanted. Explain the consequences to the consumers in the ecosystem. Would the consequences be the same if half of the boreal forest was cut down?
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CHECK and REFLECT
Key Concept Review 1. What role do producers, consumers, and decomposers each have in ecosystems? 2. Write the equation that summarizes photosynthesis. 3. Look at the organisms pictured below. (a) Identify the producer, primary consumer, and secondary consumer. (b) Identify the decomposers in this ecosystem.
A
C
B
D
10. Suppose that an unknown disease were to kill all the bacteria and fungi in an ecosystem. (a) Predict how this would affect nutrient cycling in the ecosystem. (b) Predict what would happen to energy flow in the ecosystem. 11. How is the cycling of nutrients different from the movement of energy in an ecosystem? 12. Photosynthesis and cellular respiration are called “complementary processes.” Explain why. 13. A food web contains green plants, grasshoppers, frogs, snakes, insect-eating birds, and falcons. (a) Identify the group that contains the most energy. (b) Rank the remaining groups from most to least in terms of energy content.
Question 3
4. What are two processes that cause carbon to enter the atmosphere? 5. What are two processes that cause water to enter the atmosphere? 6. Give an example of how water moves from the biotic part to the abiotic part of an ecosystem.
Connect Your Understanding 7. When you eat a healthful meal, what two things are you providing your body with? 8. How is an element different from a nutrient? 9. All decomposers are consumers, but not all consumers are decomposers. Explain.
14. Suppose a plant could perform photosynthesis but it lost the ability to perform cellular respiration. Explain what would happen to the plant and why. 15. Consider a situation where a squirrel eats a nut. (a) How much of the energy in the nut will be incorporated into the squirrel’s tissues? (b) Explain what happens to the remaining energy.
Reflection 16. In what ways has studying this section changed your understanding of ecosystems? For more questions, go to ScienceSource.
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Interactions in Ecosystems
Here is a summary of what you will learn in this section: • Biotic interactions in a community include predation, competition, and symbiosis. • Abiotic and biotic factors prevent a population from increasing beyond its carrying capacity.
Figure 1.34 The island of Surtsey near Iceland is less than 60 years old. It is a United Nations World Heritage Site.
Birth of an Ecosystem
Figure 1.35 Puffins started to nest on Surtsey in 2002.
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On November 14, 1963, an underwater volcano near Iceland erupted and poured lava onto the floor of the Atlantic Ocean, building the volcano ever closer to the ocean’s surface. Eventually, it rose above the surface and a new island was born. As Iceland welcomed a new island into its territory, the world welcomed its newest ecosystem. The Icelandic government designated the island, named Surtsey, as an ecological reserve (Figure 1.34). Only scientists visit to document the gradual appearance of new life, seed by seed, plant by plant, bird by bird. Many factors limit the populations of new species that can live on Surtsey. Seeds can be blown to its shores by the wind, but they first need soil to grow in. Although volcanic rock is rich in many of the elements present in fertilizers, such as potassium, phosphorus, and sulphur, soil has other components, such as organic matter. Birds often carry seeds in their stomachs. When they land on the island, the birds can deposit viable seeds in their wastes. Once they are deposited, the seeds are capable of growing. The birds’ wastes make excellent fertilizer. As small plants, lichens, mosses, and other organisms continue to grow, the first soils begin to form.
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Populations Increase As years go by, the ability of Surtsey to support new species and larger populations continues to increase (Figure 1.35). Populations will increase or decrease depending on the availability of abiotic factors, such as water. Some factors have more impact than others. For Surtsey, the main abiotic factor is water erosion. Since the time it was formed, erosion has already removed half of the island. Erosion will eventually wash Surtsey back into the sea.
A7 Quick Lab Keeping a Balance Organisms have to find resources in order to survive.
Purpose To simulate the competition for resources over several generations and see what happens to a population of animals
Table 1.4 Symbols Resource
Sign
Food
Hand over stomach
Water
Hand over mouth
Shelter
Hands over head to make a roof (elbows out and fingertips touching)
Materials & Equipment 4. On the signal from your teacher, turn around to face the other group. Each person in the animal group moves toward a person in the resource group that has the same sign.
• graph paper • paper and pencil • ruler
Procedure 1. You will be a member of one of two groups. One group of five will represent the animal population, the other larger group will represent the resources. Record the number in each group.
5. If an animal successfully finds a match, then the animal escorts the resource back to his or her side and the resource becomes one of a new generation of animals. If an animal is unable to find its resource, then it dies and becomes a part of the resource side. 6. Record the number of animals.
2. The animal group forms a line down one side of the class. The resource group forms a line down the other side. Each side faces away from the other. 3. Each person in both groups chooses a resource and makes the appropriate hand sign (Table 1.4). (Do not turn around.)
7. Repeat steps 2 to 6 another 10 to 15 more times. 8. Graph the data, and discuss the following questions with a partner.
Questions 9. What are some factors that affected the survival of the animals? 10. Did you notice any trends? 11. Did the animal population rise, fall or stay the same?
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Ecosystem Interactions
During Reading Create a Picture Glossary To learn unfamiliar terms, create a three-column chart in your notebook. Write the new term in the first column on the left. Add a definition in the middle column. In the third column, draw a picture that will help you to remember the term.
In an ecosystem, many interactions are happening all the time. For example, producers use the Sun’s energy to produce carbohydrates, and while they are doing this they also take in nutrients and water from the soil. Rising water levels on a lake can flood birds’ nests at the water’s edge, preventing the eggs they contain from hatching. Predators hunt, catch, and eat their prey. This reduces the prey population, but this also makes the prey population healthier as a whole because predators often remove the least healthy prey individuals from the ecosystem. Aboriginal people describe these interactions as “connections.” These connections mean that when something changes in an ecosystem, the change will affect other parts of the ecosystem. For example, when a drought occurs, plants that cannot survive in dry conditions die. Populations that depend on those plants may have trouble surviving also.
Biotic Interactions Organisms in a community interact with one another in many ways. Three main ways are through competition, predation, and symbiosis. Competition Competition is the interaction between two or more organisms competing for the same resource in a given habitat. Competition can occur between members of the same species. For example, male mountain goats compete to determine who will mate and produce offspring. Members of different species may also compete for resources. For example, raccoons and ravens might both try to feed on eggs from the same nest of a common loon.
Cape May warbler
bay-breasted warbler
Figure 1.36 These warbler species feed on spruce budworms in different parts of the same spruce tree. Notice that there is some overlap of niches.
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yellow-rumped warbler
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For similar species to coexist in an area, they must have slightly different niches. For example, many different species of similar birds called warblers feed on the same spruce budworms, but each species feeds in a different part of the spruce tree (Figure 1.36). This reduces the competition between them. Predation Predation occurs when one organism eats another organism to obtain food. Prey animals are well adapted to avoid being eaten. For example, a deer can usually outrun a bear. A porcupine’s quills are a formidable defence against lynx and other predators. Many animals use camouflage to avoid predators. For example, a stick insect resembles the twigs that it lives on. By blending into its surroundings, it avoids being eaten. Other prey animals, such as the monarch butterfly, defend themselves by tasting repulsive. They often have bright colours to warn predators away. Some species use mimicry to avoid predators. In mimicry, one species looks like another species. For example, the viceroy butterfly has markings similar to the monarch butterfly (Figure 1.37). Both species taste foul to their predators. By looking similar to each other, they both have a greater chance of not being eaten because their predators recognize their markings and avoid them both.
(a)
(b)
Figure 1.37 (a) The viceroy butterfly looks so similar to the (b) monarch butterfly that predators cannot tell them apart.
Many predators have sharp eyesight, a keen sense of smell, or both. An owl can spot a tiny mouse in the dark from high above and then swoop down to grab it on wings that are adapted to make no sound. (Flapping sounds might scare the mouse away.) The owl’s sharp beak and claws are also adapted to snag and kill its prey. Symbiosis Symbiosis is a close interaction between two different species in which members of one species live in, on, or near members of another species. There are three main types of symbiosis:
W O R D S M AT T E R
“Symbiosis” is derived from the Greek words syn, meaning with or together, and bios, meaning life.
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• In mutualism, both species benefit from the symbiotic partnership. For example, there is a South American species of ant called a leaf-cutter ant that has a mutualistic relationship with a certain species of fungus (Figure 1.38). The fungus grows in the ants’ underground colony. The ants provide the fungus with a constant supply of leaves, and the ants eat certain parts of the fungus. Figure 1.38 A leaf-cutter ant brings a piece of leaf into the colony. The white areas are the mould.
• Commensalism occurs when one species benefits from a relationship with another species without any harm or benefit to the other species. A bird building a nest on a branch of a tree, where the nest does not harm or help the tree, is an example of this. • Parasitism occurs when one species benefits at the expense of another species. Parasites live on or inside the host species and obtain some or all of their nutrition from the host. Ticks live on the bodies of mammals and feed on the host’s blood (Figure 1.39).
Figure 1.39 A tick burrows into the skin of its host. Only the tick’s abdomen is visible.
Characteristics of Populations As a population grows, each individual gets a smaller share of the resources in the area. When this happens, the organisms affected become stressed. Some die, while others are not able to reproduce. After a while, there are fewer births and more deaths. Eventually, the number of births equals the number of deaths and the population is in equilibrium. In other words, the number of individuals stays the same over time. Figure 1.40 shows a rabbit population that was introduced into a new habitat. Notice that after a while, the number of rabbits does not change. The habitat has reached its carrying capacity. Carrying capacity is the maximum number of
Figure 1.40 Real-world data on a rabbit population over a long period show that the population increases quickly at first but then increases more slowly until an equilibrium is reached and the population is steady. The ecosystem’s carrying capacity for rabbits has been reached. At this point, the number of rabbit births equals the number of rabbit deaths.
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Number of Rabbits
Ecosystem’s Carrying Capacity for a Rabbit Population
carrying capacity
Time
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individuals that an ecosystem can support without reducing its ability to support future generations of the same species. If a population exceeds its carrying capacity for a long time, it usually harms its environment.
Factors that Affect Populations in Ecosystems Various combinations of abiotic and biotic factors cause populations to increase or decrease. For example, if there is an unlimited amount of food, water, and space, populations can grow very quickly. Without any limits, 10 breeding pairs of rabbits could expand to 10 million breeding pairs in only 3 years. In a healthy, properly functioning ecosystem, limiting factors prevent overpopulation from happening. A limiting factor is an environmental factor that prevents an increase in the number of organisms in a population or prevents them from moving into new habitats (Figure 1.41). • Abiotic limiting factors include the amounts of sunlight, water, soil, and air, natural disturbances such as storms, fires, and droughts, and human disturbances such as logging. • Biotic limiting factors include competition among organisms for resources, presence of predators, reliance on other organisms for survival, and the presence of disease-causing organisms.
Figure 1.41 Many different factors can limit a population’s size.
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Take It Further Find out more about the close link between the lynx and snowshoe hare populations, including the role plants play in the lynx–snowshoe hare population cycle. Begin your research at ScienceSource.
Suggested Activity • A10 Inquiry Activity on page 44
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Consider a population of snowshoe hares, which are prey for lynx. As the population of hares increases, the lynx can capture hares more easily. The lynx are well fed and can have more offspring (Figure 1.42). As a result, their population increases. This increase in the number of lynx causes the number of hares to decrease because they are being eaten by more lynx. As more hares are eaten, the lynx’s food supply gets smaller. Some lynx starve, and those that survive may be too malnourished to produce offspring. So, the lynx population declines as well. Finally, with fewer lynx preying on them, the hare population begins to recover and the cycle repeats. This cycling is shown in Figure 1.43. For an ecosystem to be sustainable, none of the populations in the community can exceed its carrying capacity by very much or for very long. If all the populations remain at their carrying capacity, the ecosystem can usually be maintained without being weakened or losing its important biotic and abiotic factors. The goal of sustainability is to meet the needs of the present generation of individuals without affecting the ability of future generations to meet their needs.
160 snowshoe hares
lynx
9
120
6
80
3
40
0 1850
1880
1910
0 1940
Hare Population (thousands)
Lynx Population (thousands)
Snowshoe Hare and Lynx Population Cycles 12
Year Figure 1.42 The survival of these lynx kittens depends on the size of the hare population.
Figure 1.43 The rise and fall of the lynx and showshoe hare populations follows a 10-year cycle.
Learning Checkpoint 1. How does the idea of niches explain how similar species can coexist with a minimum of competition?
2. List and explain the three types of symbiosis. 3. Explain what is meant by the following terms. (a) limiting factor (b) carrying capacity (c) equilibrium
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STSE Science, Technology, Society, and the Environment
Spotlight on Nature Internet, television, and print media are powerful technologies advertisers use to sell a wide variety of products. Many corporations use images of organisms and ecosystems in their advertising or in their logos. Collect three advertisements from media sources that use images of organisms as their company’s brand or to sell a product.
1. For each advertisement, suggest a reason or reasons why the company chose the organism it did.
2. Explain whether there is a relationship between the values of the company and the organism being used in its advertising. Does it matter whether a relationship exists? 3. Does the company in any way support these organisms in their natural environment? Does it cause the organisms harm? 4. In your opinion, does a company that uses an organism to help sell its products have any responsibility to that organism? Explain your position.
A9 Just-in-Time Math 2. For each of the following population data sets, choose scales for the x- and y-axis and plot the data.
Choosing a Scale A graph’s scale is the sequence of numbers placed beside the grid points that subdivide the axis. Here are some pointers for choosing a scale, assuming the scale starts at zero.
(a) Time (years)
Rabbit
Fox
0 1 2 3 4
2 10 10 15 10
0 5 4 5 4
Time (years)
Rabbit
Fox
0 2 4 6 8
10 50 100 190 10
2 4 40 100 2
Time (years)
Rabbit
Fox
0 10 20 30
10 40 300 300
2 6 80 100
• Make sure the data point with the largest value falls in the top half of the grid and below the top of the grid. • Choose useful increments. Good increments include ones (0, 1, 2, 3, 4, . . . ), twos (0, 2, 4, 6, 8, . . . ), fives (0, 5, 10, 15, . . . ), and tens (0, 10, 20, 30, . . . ). For example, suppose there are 14 grid points available (including zero) for your y-axis and the largest y value in the data set is 20. If you choose increments of two, then the scale will be 0, 2, 4, 6, 8, and so on. The y value of 20 will be plotted on the eleventh point (counting the zero) grid point, which is more than halfway up the grid and less than the maximum value that could be plotted, which is 26. 1. Assume you are selecting a scale for the y-axis of a graph that begins at zero. For each of the following situations, what increment should you choose and what is the maximum value that could be plotted on your scale? (a) There are 33 grid points available (including 0), and the largest y value in the data set is 300. (b) There are 12 grid points available (including 0), and the largest y value in the data set is 52.
(b)
(c)
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DI Key Activity
SKILLS YOU WILL USE
A10 Inquiry Activity
Skills Reference 4
Predation Simulation Lynx are members of the cat family that live by preying on snowshoe hares (Figure 1.44). In this activity, you will simulate the predator-prey interactions between these two animals using a model in which a desk represents a forest and cardboard and paper squares represent the lynx and hares in that forest. Each lynx is represented by one medium-sized cardboard square, and each snowshoe hare is represented by a smaller paper square. When three small paper squares are tossed onto the desk, it represents three snowshoe hares entering and living in the forest. When a medium-sized cardboard square is tossed onto the desk, it represents a lynx entering the forest to hunt. If a medium-sized cardboard square lands on or touches a small paper square, it means the lynx has eaten the hare. You will generate and graph population data and use the graph to predict future populations of each species.
Processing and synthesizing data Interpreting data to identify patterns or relationships
Figure 1.44 Snowshoe hare and lynx populations are closely linked.
Materials & Equipment • desk or other flat surface, 60 cm ⫻ 60 cm • masking tape
• 250 paper squares, 3 cm ⫻ 3 cm • 12 cardboard squares, 10 cm ⫻ 10 cm • graph paper
Question What are the long-term trends in the lynx and snowshoe hare populations in this model ecosystem?
Table 1.5 Predation Simulation Data Table Generation
1
Hares at Start of Generation
Lynx at Start of Generation
3
1
2 3
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Hares Eaten
Lynx Starved
Surviving Hares
Surviving Lynx
Hares Born
Lynx Born
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Procedure 1. Create a data table similar to Table 1.5. 2. Use masking tape to mark a 60-cm square on a desktop. This represents a forest. 3. To start the first generation, toss three paper squares (representing snowshoe hares) at random onto the forest. 4. Toss one cardboard square (representing one lynx) onto the forest. Make sure it does not slide when it lands. 5. Note whether the lynx square touches any of the snowshoe hare squares. • Any snowshoe hare in contact with the lynx has been eaten. Count and remove the eaten snowshoe hares. Record the number of hares that were eaten. • If the lynx is touching fewer than three hares, it has starved. Count and remove any starved lynx. Record that the lynx starved by putting a 1 in the “Lynx Starved” column of your data table. 6. Determine the number of snowshoe hares and lynx born in this first generation. • Any snowshoe hare not in contact with the lynx has survived and reproduced. One new hare is born for each hare that survives. Toss in one new snowshoe hare square for each surviving hare. Count and record the number of hares born. • If the lynx is in contact with three or more hares, it has survived and reproduced. One new lynx is born for every three hares eaten by the lynx. Toss in one new lynx square for every three hares eaten by the lynx. Count and record the number of lynx born. • If the lynx did not survive in the first generation, wait for three generations before adding another lynx. In those generations, just add hares. Then add one new lynx that has moved in from a neighbouring forest.
hares born. Enter this number in your data table. The number of lynx will equal the surviving lynx plus any new lynx born. Enter this number in your data table. 8. Continue the simulation until you have completed 15 generations. If the hares are ever wiped out, restart the population with three new hares.
Analyzing and Interpreting 9. Graph the data for the lynx and hare populations. Plot both the lynx and hare data on the same graph to make comparisons easier. Label the yaxis “Number of Animals” and the x-axis “Generations.” (a) Describe any pattern you notice in the population of hares. (b) Describe any pattern you notice in the population of lynx. (c) Explain any relationship that exists between the populations of lynx and hares in your model. 10. Why do changes in the population of lynx lag behind the changes in the hare population? 11. Snowshoe hares eat twigs from willow trees. When snowshoe hare populations are high, overeating of willow twigs occurs. As the hare population begins to decrease due to a lack of food, the population of willow twigs increases, but young replacement twigs contain a toxin and cannot be eaten for two to three years. This can delay hare populations from recovering as quickly. Using this information, create a second graph that represents how the populations of the willow, hares, and lynx may all interact.
Skill Practice 12. Based on patterns in your graph, predict what will happen to the hare and lynx populations over the next 10 generations.
Forming Conclusions 13. State the relationship between the population of hares and the population of lynx.
7. For the beginning of generation 2, the number of hares will equal the surviving hares plus the new
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CHECK and REFLECT
Key Concept Review 1. Describe three adaptations that different prey species use to avoid being eaten. 2. Suppose that there is a forested park in which squirrels are reproducing very quickly because there is so much food available. In this situation, the population will grow until it reaches the carrying capacity. What will define the carrying capacity of the squirrel population?
6. Aphids are tiny insects that eat plants. What abiotic factors may contribute to the changes in the population that you see in the graph? Aphid Population
Number of Aphids
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Connect Your Understanding 3. Classify the following interactions as mutualism, commensalism, or parasitism. (a) A yucca moth caterpillar feeds on the yucca plant and pollinates the yucca plant. (b) Lice feed harmlessly on the feathers of birds. (c) A cowbird removes an egg from a robin’s nest and replaces it with one of its own. (d) An orchid plant grows on the branch of a tree. The tree remains healthy. 4. Identify the following limiting factors as either abiotic or biotic. (a) Wind blows the seeds of a dandelion into a pond. The seeds fail to grow. (b) A population of grasshoppers eats all the available food, and their numbers drop dramatically. (c) A bacterium causes a deadly disease in a herd of reindeer, and some of them die. (d) Plants growing beneath the trees in a forest are unable to get enough sunlight. 5. Does the success of a prey population depend on its predators? Explain.
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April
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Aug Sep Month
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Question 6
7. Cockroaches are insects that reproduce very rapidly. Suggest reasons why the world is not covered in cockroaches. 8. Revisit the interactions of the lynx and the hare. Predict how the predator-prey interactions would change if a second prey species that ate the same food as the hare were introduced into the same area. Predict how the cycle might change if a second predator were added. Draw a graph to illustrate your answers.
Reflection 9. Limiting factors normally control a population from expanding past its carrying capacity in a specific area. Most of the limiting factors that would normally control the human population have been removed through various technologies. How does this affect your quality of life? How might it affect your children’s or grandchildren’s lives? For more questions, go to ScienceSource.
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S C I E N Ceverywhere E
Cool Symbiosis
This bird is looking for parasites. The bird gets a tasty meal, and the buffalo gets rid of itchy pests such as ticks. However, these birds can also be parasites. If a buffalo is wounded, the birds will pick at the scabs, which keeps the wound open and prevents it from healing.
The adult monarch butterfly feeds on the nectar in the flowers of the milkweed plant and pollinates it. The butterfly also lays its eggs on the plant. When the eggs hatch, the larvae and caterpillars feed on the plant. Milkweed sap contains a large amount of a substance called latex. The monarch larvae and caterpillars incorporate this substance into their tissues. As a result, they taste bad and are poisonous. Monarch butterflies feed exclusively on milkweed plants.
The clownfish and the sea anemone are each other’s guardians. The clownfish can swim safely among the anemone’s stinging tentacles. This ability protects the clownfish because its predators will not get close to the stinging tentacles. There are several species of fish that can tolerate the anemone's stings and will eat the anemone's tentacles, if given a chance. This is where the clownfish comes in. It will chase away any fish that comes too close to the anemone, and so protects the anemone.
Ecosystems are complex self-regulating systems of organisms and their abiotic environments.
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CHAPTER REVIEW
ACHIEVEMENT CHART CATEGORIES t Thinking and investigation k Knowledge and understanding c Communication
7. (a) What do nitrifying bacteria do?
a Application
(b) What do denitrifying bacteria do?
8. What is the difference between a habitat and a niche? k
Key Concept Review 1. List the following terms in order from smallest to largest. k
9. When similar species live in the same habitat, explain how competition between these species is reduced. k
biome, ecosystem, biosphere, habitat 2. Identify the following items in the photograph. (a) a species
10. Name the five main terrestrial biomes found in Canada. k
k
(b) a population
11. The open ocean and a lake are both aquatic biomes. What abiotic factor makes the two biomes different? k
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(c) a community
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(d) an ecosystem
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Connect Your Understanding 12. Predict what would happen if a plant from a deciduous forest were transplanted to the tundra. Explain your answer. t 13. Compare a forest to a bicycle. How are they similar, and how are they different? t
Question 2
3. (a) Describe the role photosynthesis plays in the carbon cycle. k (b) Describe the role that cellular respiration plays in the carbon cycle.
k
4. What term best describes where all life is found? k 5. Name four elements that are found in most organisms. k 6. Give an example of an abiotic reservoir.
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14. The black-throated blue warbler migrates from the Caribbean to wetlands in northern Ontario each spring, and then it flies back again in the fall. Why would the bird make such a lengthy journey two times a year? t 15. A crow’s niche is being a scavenger. Is this an accurate description of its niche? Justify your answer. t 16. Pick any organism in your area and explain how it has adapted to the specific biotic and abiotic factors of that environment. a 17. Photosynthesis is the most important process on Earth. Justify this statement.
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18. The paths that nutrients and energy take in ecosystems are different. (a) Draw a symbol to indicate the path energy takes. c (b) Draw a symbol to indicate the path nutrients take. c 19. Suppose that a herd of reindeer had been introduced to a small island that had no reindeer on it and their population had been monitored. The table below shows the population data. Reindeer Population 1910–1940 Year
Population
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(a) Graph the population data.
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22. Suppose you had to create an imaginary animal and its predators are eagles. What adaptations would you give this animal to avoid being caught by an eagle? a 23. Disease-causing organisms can be termed parasites. However, in this chapter, disease and parasites are both listed as biotic limiting factors. Why do you suppose the author chose to separate these two factors? a
Reflection 24. Describe three things you did not know about ecosystems before you started working on this chapter. c 25. You have learned about competition among species. Think of your daily activities, and list some ways you may compete with other species for resources. c
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(b) Suggest why the population of reindeer was lower in 1940 than in 1935. t (c) Extend the graph, predicting the population in 1950 and 1960 by extrapolating from the given data. Several different plausible extrapolations are possible. Suggest one or more, and be prepared to explain your predictions. t 20. When a predator catches its prey, it may appear that the prey species suffers. But there are benefits to this type of interaction for the prey species as well. What are two ways in which the prey species may benefit from the predator hunting them? a 21. Bacteria can reproduce so quickly that, under ideal conditions, one bacterium could produce enough bacteria to cover the entire planet in only a few weeks. Explain why this does not happen. a
After Reading Reflect and Evaluate How did the use of visualization and picture mapping help you to understand new ideas and terms? Share with a partner one of the diagrams or picture maps that you drew, and explain the concept or terms that it illustrates.
Unit Task Link In the Unit Task, you will be designing a community that will have as low an impact as possible on the surrounding ecosystems. You will have to assess the abiotic and biotic factors in your area. What are the abiotic factors that affect the area where you live (for example, availability of water, average temperatures, and amount of sunlight)? Also think about the energy flow and cycling of matter. Where does your energy come from? How is matter cycled where you live?
Ecosystems are complex, self-regulating systems of organisms and their abiotic environments.
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Human activity affects the sustainability of ecosystems.
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Skills You Will Use In this chapter, you will: A pulp and paper mill produces paper, but it also produces pollution.
• plan and carry out investigations into how using fertilizer affects water quality and the fertility of soil and explain how fertilizer use affects the survival of a terrestrial and an aquatic ecosystem • interpret data from undisturbed and disturbed ecosystems, communicate the results graphically, extrapolate from the data, and infer the importance of biodiversity for sustainable ecosystems • analyze the effect of human activity on populations in ecosystems by interpreting data and generating graphs
Concepts You Will Learn In this chapter, you will: • identify human activities that can upset the balance of ecosystems and affect their survival
Why It Is Important Humans need ecosystems. Human activities have harmed ecosystems in many ways. If we know what factors lead to a decrease in biodiversity in ecosystems, we can take steps to undo or lessen the damage we have done to them. We also need tools to assess the damage that we have done to ecosystems. If we know what causes soil and water quality to be reduced, we can take steps to fix the damage or prevent further damage to ecosystems.
Before Reading Asking Questions of the Text and of Ourselves Good readers do not read passively. They think as they read and evaluate the information, often asking questions about the different ideas in the text. They also question their own and others’ actions and decisions that may have contributed to a particular situation. Skim the subheadings in chapter 2, and turn them into questions that begin with “How can we...?” or “How do we...?”
Key Terms • acid rain • bioaccumulation • biological oxygen demand • biomagnification • clearcutting • eutrophication • habitat change • heavy metals • invasive species • overexploitation • pesticide • urban sprawl
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Human Use of Ecosystems
Here is a summary of what you will learn in this section: • All human societies depend on sustainable ecosystems characterized by maximum biodiversity. • Managing the world’s ecosystems means achieving sustainable use, preventing sudden irreversible changes to ecosystems, and addressing the impact of poverty on society and sustainability. • Habitat change, overexploitation, pollution, invasive species, and climate change are the main factors influencing loss of biodiversity. Figure 2.1 These stone statues are roughly 4 m high, and each has a mass of over 11 tonnes. No one knows exactly how the Easter Islanders moved these statues from the quarries across the island to the coast, where they currently sit.
A Lesson in Sustainability In 1722, Dutch sailors arrived on Easter Island, a 165-km2 island in the Pacific Ocean. They found an island with no trees and little significant plant life. There were also no domestic animals. The few people on the island were so desperate for food that they had resorted to cannibalism. The mystery of what happened on the island has only recently been solved after scientists discovered that Easter Island had once been covered with large palm trees. Hundreds of years ago, a small group of Polynesians migrated from a nearby island to Easter Island in large sea-going canoes. They brought chickens, rats, dogs, and some crop plants with them. When they arrived, the island was covered with palm trees. The island’s climate proved to be too cool to grow their crops, but its coasts were rich with sea life: porpoises, fish, turtles, and nesting birds. Within five or six centuries, the population grew to 10 000. With more people, they needed more resources. They hunted all the animals that were close to shore, and they had to venture farther out to sea to find food. They also cut down the palm trees to use for fuel faster than the trees could grow back. To complicate matters, the rats they brought with them ate both the seeds and saplings of young trees. 52
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Eventually, the last tree was cut down. Due to the lack of wood, the islanders no longer had working canoes, and food became very scarce. The islanders ate all the dogs, rats, chickens, and nearly all the nesting birds. By the time the Europeans arrived, there were only a few small communities living in caves. The islanders’ only legacy was their stone statues (Figure 2.1). Because of unrestricted population growth, too high a demand on their resources, and no long-term plan to use their resources wisely, the result was an ecological disaster, which caused the population to crash. Easter Island shows what can happen when resources are not used in a sustainable way.
Figure 2.2 Modern-day Easter Island
A11 Quick Lab Managing Resources Purpose To manage a resource, candy, in a sustainable way
Materials & Equipment • 100 small candies • 1 paper napkin or piece of paper towel CAUTION: Do not eat anything in the lab.
Procedure 1. In small groups, arrange yourselves so that you are facing each other with 16 candies in a pile on a paper napkin in the middle of your group. Each group member plays once per round. Work out a group agreement on the order of play. 2. The candies represent your resources. Your goal is to manage them as you see fit, either as individuals or as a group. 3. Each turn, a player will have an opportunity to remove candies from the pile. (Do not eat any of the candies.) • To survive, each group member must take at least one candy per turn.
• During his or her turn, each group member may take as many candies from the resource pile as he or she wishes. 4. After each round, count the number of candies left in the resource pile and add the same number of candies to the pile. For example, if there are 10 candies left in the pile, add 10 more to the pile. 5. Stop after three rounds. Assess what has happened as a result of the game play so far. 6. Restart the simulation several times, trying out different strategies for managing the candies. Note the results.
Questions 7. Decide on a set of rules that would result in the best sustainability for the group with the least amount of restrictions on the behaviour of individuals. 8. In what situations would a one-time renewal of candy resources lead to sustainable availability of candies in the long term?
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Human Impacts and Biodiversity Human well-being depends upon ecosystems. Ecosystems provide humans with many services. Ecosystems supply food, fuel, natural resources, and water. Ecosystems cycle nutrients and decompose wastes. They regulate climate. The animals they contain help pollinate crops and disperse seeds. Ecosystems also provide humans with cultural and recreational opportunities (Figure 2.3).
Figure 2.3 Enjoying nature contributes to the well-being of humans.
Figure 2.4 These wolf pups may look similar, but each one has slight differences that may influence its survival.
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All the species contained in ecosystems contribute to these services. So we all have a vital interest in maintaining biodiversity, which is the types and numbers of organisms in an ecosystem. To maintain biodiversity, we have to use ecosystems in a sustainable way. Sustainable use of an ecosystem means using an ecosystem’s resources in a way that meets our current needs without compromising the ability of future generations to meet their needs. So far, we have referred to biodiversity as the variety of species on Earth. But the term also refers to other levels of biodiversity. There is diversity within a species. For example, members of a human family may all look similar, yet each individual is unique and is different from every other member. Differences in individuals can help keep a population healthy. For example, in a wolf pack some wolves may be better able to resist certain diseases than other members, and some may be better than others at tolerating a lack of water (Figure 2.4). These differences among individuals of the same species are called genetic differences or genetic diversity. Lack of genetic diversity in a population can be a real threat to its survival and can even lead to extinction. Extinction is the death of every member of a species. Reducing the sizes of populations can reduce genetic diversity in a population, putting the whole population at risk.
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Biodiversity also refers to the variety of ecosystems found on Earth. This includes human-made ecosystems, such as farms, as well as the variety of naturally occurring ecosystems. Because different ecosystems provide different services, it is vital that we maintain as many types of ecosystems as possible. Human activity has caused all levels of biodiversity to decrease at an unprecedented rate. The five major causes of this are: • habitat change • overexploitation • pollution
During Reading Making Inferences By asking the question “Why?” you can often make inferences or calculated guesses about the factors that affect biodiversity. As you read about each factor, ask the question “Why?” and make note of your answers. Draw conclusions about how we might lessen the effect of these factors.
• invasive species • climate change
Habitat Change Habitat change is the process by which humans alter a habitat enough so that the native species can no longer live there. Native species are species that normally live in that habitat. If their habitat changes, they either die or move to another habitat. Throughout the biosphere, habitat change is the most common cause of declines in the populations of many species. Humans change habitats for many different purposes. We clear land for things such as agriculture, forestry, and urban development (Figure 2.5). Habitat change has been severe in the world’s tropical rainforests. Currently, only 9 million square kilometres are left of the 16 million square kilometres that originally existed.
Figure 2.5 This tropical rainforest in Brazil is being cleared in order to create pasture for
cattle. Human activity affects the sustainability of ecosystems.
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Figure 2.6 (a) A redfish in an intact ocean reef (b) After a bottom trawler has passed, a reef has been reduced to rubble.
Altering habitat may also lead to habitat fragmentation. Often, small areas within a large region are altered a bit at a time. This creates a patchwork of altered and original habitats. For example, southern Ontario was once covered in deciduous forest. Now, the original forest habitat is fragmented into small patches of forest interspersed among farms, suburban developments, and cities. Habitat change also occurs in marine and coastal systems. For example, in a fishing method called bottom trawling, nets are dragged along the bottom of the oceans to catch shrimp and bottom-dwelling fish. This can completely disrupt the marine ecosystem by removing many producers from the food web as well as harming coral formations (Figure 2.6).
Overexploitation
Figure 2.7 Catching cod in the
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Overexploitation of a resource means using a resource faster than it can be replaced. Overexploitation can often lead to extinction. A common example of overexploitation is overfishing. Around the world, many species of fish have been overfished, which has resulted in complete collapse of these populations of fish. Since the 1950s, humans have removed an estimated 90 percent of large fish from the sea. Overexploitation of the seas is one of the greatest environmental catastrophes in human history. One example of overexploitation of a fish stock occurred in Atlantic Canada, where cod used to be abundant (Figure 2.7). Over the past century, the demand for cod grew and fishing technologies allowed more cod to be caught. Mature fish normally swim relatively close to the surface. When fishing fleets no longer caught
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Figure 2.8 Cod were fished commercially for 500 years before the modern industrial fishing fleets wiped out much of the population.
Canadian Cod Harvest 1850–2002 900 000 800 000 Fish Catches (tons)
700 000 600 000 500 000 400 000 300 000 200 000 100 000 0 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Year Source: Millennium Ecosystem Assessment
fish at the surface, they fished deeper in the ocean, where the young fish are found. The fish on which cod fed were also located farther down. By fishing deeper, the industry was, in effect, collecting next year’s cod harvest as well as the cod’s food source. By the 1990s, the populations were so low that the cod fishery had to be closed. The cod populations have yet to recover (Figure 2.8).
Suggested STSE Activity • A12 Decision-Making Analysis on page 64
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Overuse of Water Around the world, fresh water is a precious resource. Canada has the world’s largest supply of fresh water, and we are still working on ways to sustainably manage it. The consequences of water mismanagement are illustrated by the Aral Sea in central Asia (Figure 2.9). The Aral Sea was once the fourth-largest lake in the world. It is called a sea because it is so large, but it is a freshwater ecosystem. The government of what was then the Soviet Union decided to grow cotton and rice in the region. To irrigate the crops, water was diverted from the two rivers that flowed into the lake. Slowly, the lake’s water level dropped N BELARUS RUSSIA (Figure 2.10 on the following page). Dropping water levels UKRAINE KAZAKHSTAN split the lake in two, creating the North Aral Sea and the Aral Sea MOLDOVA South Aral Sea. The water drop affected the ecosystem in ROMANIA the lake, including the fish. Many people relied on fishing Black Sea BULGARIA GEORGIA UZBEKISTAN for jobs. But as the water level dropped, the fish ARMENIA TURKMENISTAN TURKEY AZERBAIJAN disappeared. As a result, the lake’s commercial fishery no SYRIA CYPRUS longer exists. Despite the slow shrinkage of the sea, the AFGHANISTAN LEBANON IRAN IRAQ ISRAEL rivers are still being diverted for irrigation. However, the 0 400 800 km JORDAN Kazakh government has increased water flow into the Figure 2.9 The Aral Sea borders Kazakhstan and Uzbekistan. lake, and the North Aral Sea level is slowly rising.
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Figure 2.10 (a) The Aral Sea was already shrinking in 1985. (b) By 2007, it was less than 10 percent of its original size.
Pollution Pollution is any substance added to the environment that produces a condition that is harmful to organisms. One example of pollution is solid waste that cannot be recycled. The garbage you put out on the curb or take to the landfill is solid waste. Currently, most garbage goes to landfills, where it is prevented from entering the environment. Garbage that does not enter the landfill and litter contaminate ecosystems. Another form of pollution is air pollution. One of the most important pollutants worldwide is human-produced carbon dioxide gas. Automobiles, airplanes, power plants, and factories all emit carbon dioxide. Increased levels of carbon dioxide have caused global temperatures to rise. This, in turn, is accelerating global climate change. Water can become polluted very easily. Pollution can enter water sources in different ways (Figure 2.11). Point source pollution enters a body of water at a specific place from an identifiable source. Oil spills from tankers, waste water from pulp and paper mills, and partly treated waste water released from a sewage treatment plant are examples of point-source pollution. Non-point source pollution enters bodies of water indirectly when water from rain or snow travels over land and picks up pollutants from many different sources before entering a stream or a lake. Fertilizer and pesticide run-off from farms and salt runoff from roads are both examples of non-point source pollution. Since all organisms need water, all organisms are exposed to the pollutants water contains. You will learn more about water pollution in the following section. 58
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agricultural non-point sources
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forest non-point sources
Figure 2.11 Point and non-point sources of pollution
urban non-point sources industrial point source
septic systems
Invasive Species Increases in international travel and trade have introduced non-native species to all parts of the globe. For example, the Great Lakes are part of an important shipping route. While in these waters, foreign ships may release non-native species when they empty their ballast tanks. An invasive species is a non-native species that causes harm to the ecosystem into which it has been introduced. Invasive species tend to outcompete native species, often because they have no natural predators in the new ecosystem or they reproduce faster than native species. As a result, their populations increase rapidly while native species’ populations decline (Figure 2.12). The dog-strangling vine is native to Eurasia and was introduced to North America as a garden plant (Figure 2.13). It has invaded sunny hillsides and ravines across southern Ontario. It grows in dense colonies and smothers small plants and tree seedlings, small shrubs, and saplings. It also affects monarch butterflies. The vine is a member of the milkweed family. Monarchs lay their eggs on native milkweed plants, but they will also lay them on the dog-strangling vine. However, the larvae cannot survive on the vine and die.
Figure 2.12 The eastern bluebird has suffered from the presence of starlings and sparrows. These two invasive species outcompete bluebirds for nest sites. In the past century, bluebird populations declined by 90 percent.
Suggested STSE Activity • A13 Decision-Making Analysis Case Study on page 66
Figure 2.13 The dog-strangling vine has completely invaded the understorey of this tree plantation. Human activity affects the sustainability of ecosystems.
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Climate Change Climate change is a cause of loss of biodiversity around the world. Climate is the average weather conditions that occur in a region over a span of 30 years or more. When climate change occurs in a region, average temperatures may rise or fall, the amount of rainfall may increase or decrease, and even general wind directions may change. If species are to survive through periods of climate change, individuals must be able to adapt to the new conditions. However, climate change is currently being driven by a process called global warming, which is an increase in Earth’s average temperature, caused partly by an increase in carbon dioxide in the atmosphere. Over the past two centuries, the amount of carbon dioxide in the atmosphere has increased, largely due to human activities that burn fossil fuels. Global warming has caused relatively rapid climate change. For example, the Arctic is warming faster than at any time in recorded history. The ice packs are shrinking and breaking up. Species that depend on ice packs, such as seals and polar Frigure 2.14 Walruses in the eastern Arctic rely on ice floes. bears, are losing their habitat (Figure 2.14). As a They haul themselves onto the ice to rest. result, their populations are declining.
Learning Checkpoint 1. List three levels of biodiversity. 2. What is the difference between habitat change and habitat fragmentation? 3. What resources have been overexploited? 4. (a) Name an invasive species in Ontario. (b) Explain how this species has affected native species.
Human Impacts on Ontario Ecosystems People in Ontario use the land and water for a variety of different purposes: farming, housing, industry, recreation, mining, logging, and a whole host of other uses. Each human activity affects the land and local biodiversity in different ways. By knowing how a human activity affects the ecosystem, steps can be taken to help lessen these effects.
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A Freshwater Ecosystem The thriving cottage and recreational industries in Ontario put a great deal of stress on the lake ecosystems. Figure 2.15 shows some of the sources of stress on a typical lake in cottage country. Table 2.1 summarizes the effects of these stresses.
Figure 2.15 A typical lake in the heart of Ontario’s cottage country
Table 2.1 Stresses on Lakes and Their Effects Stress
Effects
Motor boats
Oil leaks can easily contaminate lake water. Oil reduces the water’s oxygen level and so affects the health of fish and other lake organisms.
Sewage
Sewage leaking from septic tanks can increase the nitrogen content of the water. This contamination eventually reduces the biodiversity of aquatic organisms.
Docks
Building docks can disturb fish spawning grounds and disturbs floating and submerged aquatic vegetation.
Boat wakes
Waves disturb aquatic and terrestrial vegetation along the shoreline and nesting sites of loons and other birds.
Beaches
Removal of aquatic and terrestrial vegetation along the shoreline means loss of habitat for other organisms.
Clearing shoreline
When shoreline vegetation is cut down, fish lose the shade and cover the vegetation provides.
These stresses affect the sustainability and biodiversity of a freshwater ecosystem. For example, some animals, such as loons, are affected by waves from boat wakes. They will move to other less disturbed habitat. The fish populations decline due to the pollution. Human activity affects the sustainability of ecosystems.
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Ge
A Suburban Terrestrial Ecosystem
or
N
gi
The Niagara Escarpment is a long cliff that forms the Bruce boundary between two flat regions, each with a Peninsula different elevation. The escarpment stretches 725 km Lake from the western end of Lake Erie, northwest to the Huron tip of the Bruce Peninsula (Figure 2.16). Most SIMCOE Owen famously, it forms the ledge that makes Niagara Falls COUNTY Sound so impressive. Along its length are forests and other GREY Barrie COUNTY BRUCE wildlife habitats, and the headwaters for five major COUNTY DUFFERIN rivers flow from its slopes (Figure 2.17). Among its COUNTY Orangeville forests are cedar trees that are over 1000 years old. PEEL The Niagara Escarpment also runs through the Toronto Golden Horseshoe, one of the most heavily populated HALTON Lake areas in Canada. Cities such as Hamilton are built on Ontario the edge of the escarpment. As the population of HAMILTON WENTWORTH Hamilton southern Ontario grew, so did the demand for land NIAGARA Niagara Falls for housing developments, industry, farmland, WELLAND Niagara Escarpment Plan area vineyards, and rock quarries. Some parts of the 0 25 50 km Lake escarpment gradually fell victim to urban sprawl. Erie Urban sprawl is the unplanned, disorganized Figure 2.16 The escarpment area marked on the map contains natural areas, farmland, subdivisions, and growth of urban and suburban development into the parks. surrounding countryside. Urban sprawl has affected local biodiversity through habitat change and habitat fragmentation. The remaining undisturbed forest on the escarpment is now in smaller, disconnected sections. A smaller, fragmented habitat leads to a loss of biodiversity. The Ontario government recognized that the escarpment’s ecosystems were threatened, so it created the Niagara Escarpment Plan. It is a land-use plan that focusses on environmental protection. It has guidelines on how land in the escarpment area can be developed. an
Ba
y
A Forest Ecosystem
Figure 2.17 Bruce Peninsula National Park is one of the protected areas on the Niagara Escarpment.
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Boreal forest covers most of Ontario’s land area. Commercial logging is a major industry in northern Ontario. Logging companies often use clearcutting to remove trees. Clearcutting removes all the trees in an area at one time, regardless of size. When forestry companies clear-cut forests, they break large areas of forest into smaller fragments (Figure 2.18), which can threaten local biodiversity. Some species, such as wolves, require very large areas of forest to hunt moose and other prey. Fragmenting their habitat makes it difficult to find food.
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Take It Further Overexploitation of water happens in North America. Find out about the state of the Ogallala Aquifer. Begin your research at ScienceSource.
Figure 2.18 Logging companies clear-cut relatively small sections of forest, leaving other patches still standing.
Fragmentation is a serious problem in Ontario. About 30 percent of northern Ontario’s boreal forests are within three kilometres of a road. This increases animal deaths through road kill, habitat destruction, altered water flow, and soil degradation. Ontario has adopted certain measures to ensure a sustainable forestry industry. Companies have to plant new trees in an area that has been clear-cut. Also, they are not allowed to cut down more trees than they can replant in the same year. Logging companies have started to use more sustainable logging practices, such as leaving the forest in place around bodies of water. This reduces changes in water flow that can result from logging.
Learning Checkpoint 1. (a) What are three stresses put on a freshwater lake in Ontario? (b) Describe the effects of these stresses. 2. Explain how urban sprawl affects the Niagara Escarpment. 3. What is clearcutting? 4. What is the major effect that clearcutting has on the boreal forest ecosystem?
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A12
STSE Decision-Making Analysis
Skills References 4, 9
Defining and clarifying the research problem Justifying conclusions
Wild Fish Versus Farmed Fish Issue Fish stocks around the globe have been drastically reduced due to unsustainable fishing practices. Many countries are turning to fish farms, also known as aquaculture, in which the fish are housed in underwater cages and farmed. However, some kinds of fish farming are very controversial because diseases among farmed fish sometimes infect wild stocks. Also, farmed fish that escape can become invasive species or interbreed with wild stocks, potentially weakening the wild stocks. Fishing wild species almost always results in by-catch, which is unintentionally catching fish species other than the target fish species. Sometimes, the fish populations most threatened by fishing wild stocks are not even the intended catch. This leaves a very important question: which is more sustainable, aquaculture, wild stock fishing, or a mixture of both?
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Data from harvests of three species of wild stocks are presented in Table 2.2. These numbers are actual data taken from Fisheries and Oceans Statistical Services archives. The numbers represent the total mass of fish caught in Canada. Table 2.3 on the next page shows data on farmed salmon and trout. Table 2.2 Wild Fish Harvests 1985–2006 (tonnes)
Year
Cod
Redfish
Herring
2006
28 266
32 525
182 194
2005
27 693
34 273
192 041
2004
26 049
32 431
207 235
2003
23 573
36 268
229 613
2002
36 434
36 898
219 648
2001
40 913
41 583
224 914
2000
46 888
44 306
233 785
1999
56 314
43 683
214 679
Background Information
1998
39 201
47 691
216 836
Making management decisions about fishing depends on knowledge of wild fish populations. If wild stocks are threatened by overexploitation, banning fishing is a sound decision. However, how do we know if a fish population is threatened? Gathering data on fish and other species from marine and freshwater ecosystems is challenging. One method is to keep track of the total mass, or tonnage, of fish caught in commercial fisheries. However, relying solely on this data has often meant that by the time enough data were gathered and analyzed, the fish population was already in an advanced stage of collapse. Around the world, stocks of many different species have collapsed. This has happened time and time again across the globe in the last half century, mainly due to the introduction of large factory fishing fleets. Even so, a great deal of valuable information can be inferred from the data obtained through fisheries.
1997
31 418
39 277
218 525
1996
16 447
45 200
211 568
1995
14 661
39 624
220 472
1994
26 270
75 070
247 777
1993
84 767
109 329
242 968
1992
198 078
125 103
251 433
1991
321 833
116 109
256 485
1990
401 257
109 164
301 328
1989
435 373
100 604
270 035
1988
479 141
104 828
310 283
1987
471 897
104 774
284 626
1986
478 730
104 320
203 086
1985
492 767
89 283
219 167
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STSE Decision-Making Analysis (continued)
Table 2.3 Aquaculture Harvests 1986–2006 (tonnes)
Year
Salmon
Trout
2006
118 058
5 033
2005
98 369
4 878
2004
90 646
4 858
2. Create a second line graph for the farmed species in Table 2.3. The vertical scale will probably be different than the one on the first graph because the numbers are much smaller. Use a different coloured pencil for each species, and add a legend and a title.
2003
99 961
5 253
3. Describe any trends you see in the wild fish data.
2002
126 321
6 833
2001
105 606
6 513
2000
82 195
6 514
1999
72 890
6 574
1998
58 618
6 022
1997
57 775
5 930
1996
45 624
6 615
1995
42 515
4 429
1994
36 083
4 004
1993
36 670
3 718
1992
30 325
3 511
1991
34 109
2 839
1990
?
4 497
1989
?
3 614
1988
?
3 259
1987
?
2 842
1986
?
2 167
Analyze and Evaluate 1. Create a line graph for each wild species listed in Table 2.2. Graph the data for all three species on one graph. Choose the vertical scale (tonnes of fish harvested) carefully so that all the data fit on the graph. Use a different coloured pencil for each species. Be sure to put a legend and title on your graph.
4. Some wild fish populations change more drastically than others. Suggest reasons for this. 5. What inferences can you draw about sustainability of the wild stocks over time? 6. Describe any trends you see in the farmed fish data. 7. What do the data from the farmed fish stocks suggest about the sustainability of aquaculture? 8. Fish harvest data alone do not give enough information to decide which kind of fishing method is more sustainable. Working in small groups, choose one of the two fishing methods to investigate. Research the pros and cons of your chosen method. Consider the costs and benefits to society and to the environment. 9. Summarize your findings, and present a brief list of the costs and benefits of your method to the class. 10. As a class, discuss the issue and try to reach a consensus as to the most sustainable way to use wild fish and farmed fish.
Skill Practice 11. Justify any conclusions you drew from the discussion.
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CASE STUDY
A13
STSE Decision-Making Analysis
SKILLS YOU WILL USE Skills Reference
4
Gathering information Summarizing information
Invasive Species Issue When people mention dangerous fish, sharks, piranhas, and barracudas probably come to mind. By comparison, the round goby seems harmless (Figure 2.19). However, this fish and other invasive species cost the Ontario economy hundreds of millions of dollars. How could human activities be modified to minimize or prevent the introduction of non-native organisms to the environment?
mussel. Zebra mussels often have very high levels of contaminants in their tissues. These become concentrated in the round goby. Any animals that eat the round goby are likely to have much higher levels of contaminants in their tissues as well. Other invasive species, including the Eurasian ruffe, spiny water flea, zebra mussel, and purple loosestrife, have also been introduced to the Great Lakes through ballast water.
Background Information
Analyze and Evaluate
Native to eastern Europe, the round goby arrived in North America in the ballast tanks of a ship. When the ship dumped its ballast water in Lake St. Clair, it released a number of invasive species into the Great Lakes, including the round goby. The round goby arrived in North America without the predators and parasites that are associated with it in its natural habitat, and the exotic invader was free to reproduce as fast as it could. The round goby is highly territorial and able to outcompete many native fish, including mottled sculpin and native logperch, causing declines in these populations. This fish is relatively small, growing to an average length of 18 cm in the Great Lakes. It prefers the rocky and sandy lake bottoms that are typical of the Great Lakes. In addition to displacing a number of native fish, the round goby is also a voracious predator of another invasive species, the zebra
1. ScienceSource Use the Internet to research how human activities have contributed to the introduction of so many invasive species in the Great Lakes. Identify how the invasive species and native species interact. Also research how the environment and human society have been affected by the invasive species. 2. Draw a concept map to show the social, economic, and environmental consequences of these interactions. 3. Analyze your research, and describe the effects invasive species have on society, the economy, and the environment. 4. Write a proposal to the Ministry of Natural Resources recommending which human activities should be discontinued in the Great Lakes to reduce the introduction of non-native species. Alternatively, you may propose potential solutions to reduce the introduction of invasive organisms to the Great Lakes. 5. Web 2.0 Develop your proposal as a Wiki, a presentation, a video, or a podcast. For support, go to ScienceSource.
Skill Practice 6. Summarize the information you found in a brochure for the public to educate them about the issue. Figure 2.19 The round goby is a relatively small fish and is considered very aggressive.
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CHECK and REFLECT
Key Concept Review 1. List five services that we rely on ecosystems to provide. 2. Describe three levels of biodiversity. 3. What is extinction, and how is it related to biodiversity? 4. Give two examples of how overexploitation of a resource has harmed ecosystems.
Connect Your Understanding
8. Easter Island represents an unsustainable use of ecosystems. You have learned that five factors can affect the sustainability of ecosystems. Did all of these factors contribute to the islanders’ demise? Justify your answer. 9. What are three negative ecological consequences of logging within the boreal forest ecosystem? 10. Explain the possible threats to biodiversity shown in the photograph below.
5. Suppose a non-native species of beetle is introduced into a forest. How would you know if the beetle was becoming an invasive species? 6. Rhinoceros horns are valued in certain countries and are used to make dagger handles. This has led to the illegal hunting of rhinoceros in all parts of Africa. Rhino populations are low and still declining. (a) What is the factor that is affecting the rhino population? (b) What is a possibility if the current trend is not reversed? 7. Identify the misconception in each of the following statements. Rewrite each sentence so that it is no longer misleading. (a) Not all species are important, so some have to be sacrificed. (b) If an ecosystem appears to have a lot of one particular species, then it must be healthy. (c) Biodiversity is unimportant to humans. (d) A large, smelly swamp is a nuisance to humans and not ecologically valuable.
Question 10
Reflection 11. Ecosystems provide things that directly affect you. Do you take these things for granted? Give an example of how an ecosystem specifically helps you. Which value related to the preservation of biodiversity do you hold most important? For more questions, go to ScienceSource.
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Assessing the Impact of Human Activities on Ecosystems
2.2
Here is a summary of what you will learn in this section: • Different soils have different characteristics that can be assessed. Human activities can have long-lasting effects on soil. • Water can be tested for the presence of pollutants such as heavy metals, pesticides, and fertilizers. • Human activities have affected Ontario’s terrestrial and aquatic ecosystems in many ways.
Figure 2.20 The amount of plastic in the world’s oceans exceeds 100 million tonnes. Most of us usually encounter this plastic pollution only when it washes ashore as it has done here on Hawaii.
Great Pacific Garbage Patch The world’s oceans are so big, it is easy to think that tossing garbage into them will not really affect the environment. Evidence suggests that the opposite is true. There are great circular ocean currents, called gyres, that swirl floating debris to their centres, and the debris stays there. The North Pacific Ocean has two large gyres, each thousands of kilometres across. People passing through them in sailboats have reported constant encounters with floating garbage. This does not mean, however, that there is an “island of floating junk” that you could bump into or photograph from space. It might be better for the environment if there actually were such an island. At least we could travel to it and clean it up. In reality, enormous amounts of garbage, mostly plastic, are spread out over thousands of square kilometres of ocean. These items float on or just beneath the surface. Occasionally, the North Pacific gyre brushes past the Hawaiian Islands and deposits mounds of plastic from across the world onto Hawaii’s beaches (Figure 2.20).
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The Impact of Human Pollution The United Nations Environment Programme (UNEP) estimates that plastic debris kills more than a million sea birds every year. Sea birds, sea turtles, and other animals mistake bits of plastic for food items. Plastic pieces can last for over 50 years in the ocean, and because they are not digested when eaten, they can go on killing animals. The animals die from eating plastic items, and their remains decompose. The plastic items, however, do not. They stay in the environment and can be eaten by other animals. UNEP reports that cigarette lighters, syringes, and toothbrushes are just some of the items that have been found in the stomachs of dead sea birds (Figure 2.21).
Figure 2.21 This albatross chick died from plastic consumption.
A14 Quick Lab If Earth Were an Apple Purpose To create a model that demonstrates the amount of land on Earth that is available to grow food
Materials & Equipment • apple • cutting board • knife CAUTION: Do not eat anything in the lab.
Procedure 1. With a partner, estimate what fraction of Earth’s surface is available to grow food for the world’s human population. Record your estimate. 2. Obtain an apple, and place it on the cutting board. The apple represents Earth. 3. Cut the apple into four quarters. Three of the quarters represent the oceans of the world. Place them in the discard pile.
4. Cut the remaining quarter in half. One piece represents the land area that is uninhabitable: polar areas, deserts, swamps, and high mountains. Discard one piece. The remaining eighth represents the land area where people live. 5. Cut the eighth into four equal pieces. Three of these represent the areas unable to produce food because they are too wet, too stony, too cold, too steep, or have poor soil. They also represent cities, suburbs, highways, malls, schools, parks, industrial areas, parking lots, and many other places where people live and work but do not grow food. Put them in the discard pile. 6. Carefully peel the 1/32nd slice of Earth. This tiny bit of peel represents the surface of Earth’s crust upon which humankind depends to grow food. It is less than 2 m deep and is a quite fixed amount of food-producing land.
Question 7. Think about your model and the information in step 6. What does this mean for humans and the amount of space on Earth to grow food?
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Acid Rain and Ontario’s Ecosystems Emissions from a variety of human activities contain pollutants that enter the atmosphere and can have wide-ranging effects on the environment. In Canada, emissions come from mining and refining metals, electrical power generation, oil and gas operations, and automobiles. Nitrogen- and sulphur-containing substances are two of the most common pollutants in emissions (Figure 2.22).
chemical transformation
condensation
nitric acid sulphuric acid
emissions to atmosphere nitrogen-containing substances sulphur-containing substances
dry fallout dust, gases
industry
transportation
mining and refining metals
precipitation acid rain, fog, snow, and mist
power generation
Figure 2.22 The steps involved in forming acid rain
Once these substances are released into the air, they combine with water vapour in the air and form acids. An acid is a common type of chemical. Some acids are safe for the environment. You even consume them in foods such as orange juice and salad dressing. However, many acids are not safe and can damage ecosystems. The acids formed in the air by emissions fall as acid rain. Acid rain affects soils, vegetation, lakes, rivers, and terrestrial and aquatic animals.
Effects of Acid Rain Acid rain damages the waxy coating that protects leaves from infection. When acid rain seeps into soil, it burns the skin of earthworms. It increases the acidity of the soil and affects plant roots’ ability to absorb nutrients. Acid rain also makes bodies of water more acidic. Shellfish are the most sensitive because the acid in the water dissolves their shells. When lakes become acidic enough, no organisms can survive in them. These lakes have clear blue water but contain no life.
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When scientists discovered how acid rain was caused and its wide-ranging effects, governments put limits on emissions. In response, the mining industry installed scrubbers, which remove a large proportion of the damaging chemicals from the emissions before they are released. As a result, acid rain has been reduced. However, it has not been eliminated completely. Countries that have not implemented these changes continue to produce emissions that cause acid rain. The wind carries these emissions to other countries (Figure 2.23). Acid rain is an international problem, not just a Canadian one.
Figure 2.23 The trees in this forest have been damaged by acid precipitation. The pollutants that caused the acid rain probably entered the atmosphere far from this forest.
Assessing Impacts on Ecosystems When we examine pollutants, such as acid rain, in ecosystems, we have to have ways of assessing their effects on soils and water. Understanding the effects of human activities on soils and water, and the organisms that depend on them, helps us to find ways to prevent harm to ecosystems. It also helps us to find ways to improve the health of ecosystems that have been damaged by human activities.
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Assessing Soils Soil and water are essential to all ecosystems. Soils are much more than just dirt. They are bursting with life. The condition of a soil indicates the health of any ecosystem that depends on it, as well as the effects human activities have on it. To assess the condition of a soil, it is helpful to know what soil is. Soil is a loose covering on the ground containing a mixture of organic matter, minerals, and moisture. Soil quality includes soil profile, soil type, and acidity.
Soil Profile Soil is made up of distinct layers, as shown in Figure 2.24. • Topsoil is the uppermost layer in soil. It is composed chiefly of humus, which is decaying organic matter. It also contains rock particles and organisms such as bacteria, fungi, insects, and worms. • Subsoil is the layer below topsoil. It is very compact and has little or no organic matter except roots of very large trees and bacteria. • Bedrock forms the bottom of the soil profile. It is solid rock, and water cannot pass through it. Water travels down through the upper layers and is trapped above the bedrock. The bottom of the subsoil gets saturated like a sponge sitting in water. The top surface of the ground water is called the water table.
topsoil
water table ground water
subsoil
bedrock Figure 2.24 Soil is composed of subsoil, topsoil, and bedrock.
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Soil Types Three main soil types are loam, clay, and sandy. Each supports different varieties of plants, but the most fertile, and the one generally preferred for agriculture, is loam. • Loam soil has rock particles of many different sizes. This results in many pockets that can hold air or water, which keeps the soil loose enough that plants can grow into it easily (Figure 2.25). Loam also tends to have a lot of humus, and it drains well without drying out. The black soil of Holland Marsh, near Lake Simcoe, is loam (Figure 2.26). • Clay soil contains particles that are extremely small and so pack tightly together. This prevents the formation of air pockets. Many plant roots do not grow well in clay soil. Clay tends to block root growth and trap water, making the soil excessively wet. • Sandy soil contains sand particles, which are relatively large compared to clay particles. The presence of sand creates large spaces that permit root growth and air pockets. It also permits water to drain away quickly into the subsoil, carrying essential nutrients away from roots. This makes sandy soil much less fertile than loam. Many areas near the Great Lakes have sandy soil.
Figure 2.26 Farming in the Holland
Marsh
soil particle root cell
water
air space
Figure 2.25 The areas between soil particles are filled with air spaces and water.
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Acidity Levels Acidity is an abiotic factor that is connected to the chemical environment of soil. Soils vary in their acidity. If you have ever sucked on a lemon, you know that it is extremely sour. This is caused by acid in the lemon juice. By contrast, a banana is not sour at all. However, even bananas are very slightly acidic. Not all substances are acidic. For example, pure water is not. It is classified as neutral. To precisely assess acidity levels in soil, a special scale is used. It is called the pH scale (Figure 2.27). The pH of a soil can be measured by testing the moisture in the soil with specially treated strips of paper that change colour depending on the pH.
4.6 acid rain
2.2 vinegar
5.6 normal rain
1.0 stomach acid
0 acidic
1
2
2.0 0.5 battery acid lemon juice
3
4
4.2 tomatoes
5
6
6.0 milk
8.0 sea water
7 neutral
8
8.2 baking soda
7.0 pure water
9
10
10 toothpaste
11
12
12 ammonia
13
14 alkaline 13.8 drain cleaner
Figure 2.27 pH scale
The pH measurement of a substance can be classified as low, neutral, or high. If a soil has a low pH, it is acidic. If it has a high pH, it is called alkaline. If a soil has a pH that falls exactly between the two extremes, it is neutral. Most organisms, including plants, prefer a nearly neutral environment. Soil that is too acidic or too alkaline can damage the tissues of plants and animals or make it difficult for them to absorb nutrients. Some plants do require slightly acidic or basic pH levels and will grow only under the correct conditions (Figure 2.28).
Human Impacts on Soils Figure 2.28 These hen-and-chicks
plants require alkaline soil. Gardeners will often add limestone to soil to raise the pH.
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One of the most devastating effects of human activity on soil is soil erosion. Soil erosion is the loss of soil when water or wind washes or blows it away. The roots of plants normally hold the topsoil in place. When soil is ploughed, or tilled, the topsoil is
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exposed to wind and water, which can erode it (Figure 2.29). Overgrazing by livestock animals, such as cows and sheep, can also erode the soil. If livestock eat too many of the plants’ leaves, the plants die. Without plants to hold the soil in place, the soil erodes. Once the topsoil is gone, the land can no longer be used for grazing or growing crops. Plants draw nutrients from the soil and use them to build plant tissue. As you learned previously, when plants die, decomposers consume the dead plants and release some of the nutrients in the organic matter back into Figure 2.29 Wind is eroding the soil as it is tilled to plant crops. the soil. The nutrients can then be used again. If the same type of crop is grown in the same soil year after year, the nutrients in the soil get used up, and the crops no longer grow well in the soil. Early in the history of agriculture, farmers learned that they had to rotate their crops. Crop rotation is the practice of planting a different type of crop in a particular field each year. For example, farmers will plant wheat or corn one year, and then plant soybeans or alfalfa in the same field the following year. This replenishes some of the nutrients in the soil, especially nitrogen. Plants of the legume family, such as soybeans, peas, lentils, and alfalfa, have a symbiotic relationship with nitrogen-fixing bacteria (Figure 2.30). The bacteria supply nitrogen in a usable form directly to the plant. In return, the plant provides the bacteria with other nutrients. Nitrogen-fixing bacteria also live freely in the soil. By planting nitrogen-fixing plants, the nitrogen Figure 2.30 The white bumps on in the soil gets replenished. This reduces the need to add chemical the roots of this pea plant are called fertilizers to the soil. If farmers do not rotate their crops, they nodules. Each nodule contains millions of nitrogen-fixing bacteria. have to supply nutrients to the soil by adding fertilizers.
Learning Checkpoint 1. What are the three layers of soil? 2. Describe how sandy soil is different from clay soil. 3. Explain why it is important to know the level of acidity in soil. 4. In what ways can farming contribute to soil erosion? 5. Describe how crop rotation helps restore nitrogen to the soil.
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Assessing Water Quality Water is critical to life, and every community in Ontario has some plan to manage its use and protect its quality. Being able to assess water quality and act responsibly to protect it is essential for sustainable ecosystems in Canada and around the world. Many different aspects of water are used to assess its quality.
Aquatic Organisms Healthy aquatic ecosystems are full of organisms. These include ones that are easily recognizable, such as fish, large plants, and invertebrates. On the microscopic level, there are plankton, which are tiny plantlike and animal-like organisms, and bacteria and viruses. Sometimes, the types and quantities of species present in the water can indicate that the water is unsafe. For example, certain bacteria can cause serious health problems if they are present in large enough numbers. In summer, lakes are closed for swimming because of temporary high levels of micro-organisms that can cause diseases such as ear infections and intestinal infections. The presence or absence of some organisms can indicate that water is polluted. Indicator organisms include certain insects and insect larvae, shrimp, clams, and worms (Figure 2.31). Different organisms prefer different conditions. For example, some organisms can survive in polluted water, while others cannot. water boatman
mosquito larva
water strider
flatworm
leech midge larva
dragonfly nymph
mayfly nymph
caddisfly larva stonefly nymph
clam
Figure 2.31 The number and types of aquatic organisms indicate water quality.
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Oxygen Just as terrestrial organisms need the oxygen in the air, aquatic organisms need the oxygen gas that is dissolved in the water. • Dissolved oxygen measurements give the level of oxygen present in water. Table 2.4 shows the levels of dissolved oxygen needed by various organisms. If levels of oxygen drop below a certain level, fewer organisms are able to live in that body of water. For example, caddisfly larvae prefer water that has a high level of dissolved oxygen (Figure 2.32). If the oxygen level falls, the larvae will die.
Figure 2.32 A caddisfly larva
Table 2.4 Levels of Dissolved Oxygen Needed by Aquatic Organisms Dissolved Oxygen (mg/L)
Aquatic Organisms
8
Large numbers of diverse species thrive.
6
Mayflies, stoneflies, and beetles start to disappear.
4
Freshwater shrimps, midge larvae, and worms can survive.
2
Midge larvae and some worms can survive.
• Biological oxygen demand (BOD) measures how quickly oxygen is used up by micro-organisms in a given body of water (Table 2.5). BOD is an effective test for certain types of water pollution. Polluted water can actually promote the growth of some micro-organisms, which feed off the pollution. These organisms use up oxygen, which means oxygen is removed from the water at a high rate. In addition to the possible toxic effects the pollution can have on an aquatic ecosystem, its presence results in low oxygen levels in the water. This can cause organisms to die. Table 2.5 Typical BOD Values for Selected Water Samples Water Sample
BOD Value (mg/L)
Clear lake water with few organisms
0–5
Clear lake water with many organisms
8–20
Slightly polluted lake water
20–100
Highly polluted lake water
100–10 000
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Acidity As with soil, most aquatic organisms prefer a neutral environment. If the acidity increases, the diversity of plants and animals that live in this water decreases. Most fish die if the water’s pH falls to 4.5.
Phosphorus and Nitrogen Fertilizers are applied to fields and gardens to supply plants with nutrients, such as the elements nitrogen and phosphorus. When the field or garden is watered, the water dissolves the fertilizer and this provides the nutrients to the plants. However, water from the garden then runs into local waters and streams and takes these nutrients with it. If the stream runs into a pond or lake, the high levels of nutrients in the water cause algae to grow rapidly. This process is called eutrophication. Eutrophication is the addition of nutrients to an aquatic ecosystem causing increased growth of plants such as algae (Figure 2.33). As the large amount of algae dies and decomposes, oxygen is depleted from the water. The resulting low amount of oxygen in the water may cause fish and other animals to die. Eutrophication is a huge problem in aquatic ecosystems in areas where chemical fertilizers are widely used.
Sunlight
(1) Nitrogen and phosphorus in surface run-off enter lake.
(2) Nutrients fertilize aquatic plants on the surface. (3) Surface aquatic plants increase. (4) Less light can penetrate, and plants below the surface die.
(7) Lake can only support aquatic plants at the surface.
(5) Decomposers feed on dead plants, depleting the oxygen in the water.
(6) Animals eventually die from lack of oxygen.
Figure 2.33 The steps in the process of eutrophication
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Heavy Metals Some kinds of metals cause illness if they are present in water in even very tiny amounts. Mercury belongs to a group of substances called heavy metals. They are called heavy metals because they have a density of 5 g/mL or higher. This means that they are five or more times heavier than an equal volume of water. Other heavy metals include copper, magnification of fish-eating birds lead, and cadmium. There are many sources chemical’s concentration of heavy metals including batteries, which often contain cadmium, and compact fluorescent light bulbs, which contain 10 000 000 mercury. Both of these kinds of devices must be disposed of responsibly. Many industrial processes release heavy metals directly into the environment. For example, all coal-fired power plants, large 1 000 000 fish incinerators, and steel mills emit mercury from their smokestacks, because mercury is found naturally in coal. Mercury in the atmosphere usually settles in water. Algae absorb very tiny amounts of mercury from 100 000 small fish the water. Over time, mercury builds up in their tissues. The gradual build-up of a substance in an organism’s body is called bioaccumulation. Unfortunately, this is not the end. The contaminated algae are consumed by zooplankton, and the 10 000 zooplankton mercury bioaccumulates in their tissues. In a process called biomagnification, the mercury becomes more and more concentrated in each link in the food chain as one animal eats many contaminated 1000 producers animals (Figure 2.34). Many predatory fish, including some salmon and trout, have levels of mercury high enough to be toxic if they are eaten by humans and other animals. water 1 Health problems caused by heavy metals include kidney and lung disease, immune system disorders, cancer, sterility in men, and infertility in women. Figure 2.34 The steps involved in biomagnification
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Take It Further Aboriginal farmers developed a system of cultivation known as "the three sisters." Find out what crops made up the three sisters and what advantage each crop provided. Begin your research at ScienceSource.
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Pesticides Pesticides are chemicals that kill unwanted organisms, usually ones that attack crops and reduce their yield (Figure 2.35). Some pesticides last a long time in the environment, though in Canada these kinds are strictly controlled or banned. Just as heavy metals can biomagnify, so can some long-lasting pesticides. One such pesticide is DDT. Used in Canada until the 1970s, it built up in many top level predators, such as peregrine falcons. It made their eggshells so thin that few eggs hatched, and their populations declined. In Canada, the peregrine falcon almost became extinct due to DDT use. Modern pesticides are designed to last one growing season and then break down into less harmful substances. DDT has not been banned worldwide because in some cases, its societal benefits outweigh its environmental risks. DDT is used responsibly in mosquito-infested parts of Africa in homes and on mosquito nets. This saves millions of lives by combatting an often lethal disease called malaria, which is carried by mosquitoes.
During Reading Drawing Conclusions When we ask questions, we can analyze ideas and draw conclusions. Use a three-column chart to help you draw conclusions from the reading you have done about human interactions with ecosystems. Label the first column “I read” and record a phrase or sentence from the text. Label the second column “I asked” and write down your question(s). Label the final column “Therefore” and record your conclusion.
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Figure 2.35 Pesticides help reduce the amount of crops lost to pests. However, in addition to killing the pest species, pesticides can also kill other non-target species. This can reduce local biodiversity.
Learning Checkpoint 1. How does the presence of certain bacteria affect water quality? 2. Explain what biological oxygen demand is. 3. Explain why the presence of nitrogen and phosphorus in water can threaten ecosystems. 4. Give an example of a heavy metal. 5. Explain the process of biomagnification.
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STSE Science, Technology, Society, and the Environment
Increasing Biodiversity in Your Community 2. Brainstorm ways to increase biodiversity in your chosen area. Try to be as practical as possible. • How will you lessen or eliminate the effects that pollution, invasive species, and habitat change have had in the area? • How could you improve the water quality and soil quality? • What species do you want to introduce into your area? How will their needs be met? • How will human needs be met? Will humans use the area? If so, how will any possible impacts on the biodiversity be minimized?
To achieve sustainability, we have to maintain all levels of biodiversity: genetic, species, and ecosystem diversity. But we must remain part of our ecosystems to exist, so we have to find ways to balance human needs with maintaining biodiversity.
1. Working in groups, think of an area in or near your community where biodiversity could be increased. In a city, this could be a city park, a waterway running through a densely populated area, or a vacant lot. In a rural farming community, it could be an undeveloped patch of land between cultivated areas. In a community located within a forest, it might be the entire area surrounding the community.
3. Present your action plan to the class. Be prepared to answer any questions.
A16 Skill Builder Activity Extrapolation World Population
1. By how much did the world’s population increase from 1980 to 2000? 2. Extrapolate to predict the world’s population in 2020. 3. What assumptions did you make when you extrapolated from the data?
8.0 7.0 Population (billions)
Extrapolation is the process of estimating the value of a measurement beyond the known or measured values of a set of data. To make predictions about what may happen in the future, scientists extrapolate from existing data. For example, you can estimate how tall you will be next year based on your height measurements over the last five years. Use Figure 2.36 to answer the following questions.
6.0 5.0 4.0 3.0 2.0 0 1940
1960
1980
2000
2020
Year Figure 2.36
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DI Key Activity
SKILLS YOU WILL USE
A17 Design a Lab
Skills References 2, 6, 9
Developing a hypothesis Evaluating whether data support a hypothesis
Testing the Effects of Fertilizer on Soil and Aquatic Ecosystems Part A — Fertilizer and Soil Fertility Question How does using fertilizer affect the fertility of soil?
Design and Conduct Your Investigation 1. Create a hypothesis to explain how fertilizer could affect soil fertility. For example, adding fertilizer increases soil fertility. 2. Once you have developed your hypothesis, think about how you can test it. Consider the following questions. •
How will you measure fertility?
•
There are many different types of fertilizer. What type of fertilizer will you use, and how much should you use? How often will you apply it?
•
What kind of plants should you use? For example, will you grow plants from seeds, or will you use seedlings?
•
What aspect of a plant will you measure (for example, plan height, leaf colour)?
•
What type of soil will you choose? Potting soil? Soil from your area? How much should you use?
•
What containers will you use to grow your plants in? How many will you need?
•
How long will your experiment run?
3. Decide what variables you will control and what variables you will measure. For example, will you control the amount of water the plants get? 4. Decide what the control should be for the investigation. For example, will you grow two identical kinds of plants and treat each differently?
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5. Decide what variables you will measure in the experiment, and decide how you will measure these variables. Design a data table in which you can record your measurements. 6. Write out your procedure. Have your teacher check it before you carry out your investigation. 7. When you have finished your investigation, dispose of your materials as instructed by your teacher. Clean your work area, and wash your hands. 8. Analyze your data. Did your results support your hypothesis? Explain why or why not. 9. ScienceSource Use the Internet and other sources to find out about fertilizer use in agriculture (Figure 2.37). In what ways can fertilizer use affect the soil? 10. Extrapolating from your data and from your research, what conclusions can you draw about fertilizer use and soil fertility?
Figure 2.37 Fertilizer being applied to a field
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A17 Design a Lab (continued)
Part B — Fertilizers and Aquatic Ecosystems Question How does fertilizer use affect aquatic ecosystems?
Design and Conduct Your Investigation 1. Create a hypothesis to explain the effects fertilizer might have on aquatic ecosystems. 2. Once you have developed your hypothesis, consider the following questions. •
How will you create an aquatic ecosystem?
•
What plants will you use? How many different types will you use?
•
Will you use animals as well as plants?
•
What type of fertilizer will you use and how much?
•
What will you measure in the aquatic ecosystem?
•
How long should the investigation run?
6. Write out your procedure. Have your teacher check it before you carry out your investigation. 7. When you have finished your investigation, dispose of your materials as instructed by your teacher. Clean your work area, and wash your hands. 8. Analyze your data. Did your results support your hypothesis? Explain why or why not. 9. ScienceSource Use the Internet and other sources to find out about the effects of fertilizer use on the sustainability of aquatic ecosystems (Figure 2.38). 10. Extrapolating from your data and from your research, what conclusions can you draw about the effects of fertilizer use on the sustainability of aquatic ecosystems?
3. Decide what variables you will control and what variables you will measure. For example, will you control the amount of sunlight the ecosystems get? 4. Decide what the control should be for the investigation. For example, will you construct two identical aquatic ecosystems and treat each differently? 5. Decide what variables you will measure in the experiment, and decide how you will measure these variables. Design a data table in which you can record your measurements or observations. Figure 2.38 Aquatic ecosystems can be very near fields.
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A18 Quick Lab Deforestation and Watersheds At the Hubbard Brook Experimental Forest, ecologists carry out large-scale long-term ecological experiments. Because forests take up a great deal of water and return water vapour back to the atmosphere through transpiration, ecologists believed that deforestation may affect the water cycle. You will be provided with actual data from a 30-year experiment, which continues to this day. One set of data is from a forested watershed in which all the trees were clear-cut in 1965 (Figure 2.39). In 1966, 1967, and 1968, two herbicides were applied to the entire watershed to prevent any vegetation from growing again. The other set of data is from a neighbouring watershed where the trees were left untouched. In both watersheds, a weir was built to measure the amount of water in the stream flowing out of the watershed (Figure 2.40).
Purpose
Materials & Equipment • data sets
• coloured pencils
• graph paper
Procedure 1. Plot the data for both watersheds from 1958 to 1970 only. Use different colours to represent the two different watersheds. 2. Study the graphs for both watersheds. What trends do the data show? 3. Does cutting all the trees in a watershed increase water flow over the short term? Is there a significant difference? Explain your reasoning. 4. On the same graph, plot the remaining data for both forests from 1970 to 1988.
Questions
To analyze data to determine the short-term and long-term effects deforestation has on the amount of water flowing out of a watershed
5. Does cutting all the trees in a watershed increase water flow over the long term? Is there a significant difference? Explain your reasoning. 6. Data were collected for seven years before the trees were cut down. (a) Why is this information important? (b) What misinterpretations could have been made without the first seven years of data? 7. (a) What was the control in this experiment? (b) Why is it necessary to have a control?
Figure 2.39 The deforested watershed
8. If the experiment had been stopped five years after the forest was cut, would the conclusions have been different? What is the importance of long-term research? 9. If a community wishes to increase the water in its reservoirs, would cutting down trees be a good solution? Explain. 10. Extrapolate data points for an additional five years, and infer any future trends.
Figure 2.40 A weir
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CHECK and REFLECT
Key Concept Review 1. Which has bigger rock particles, clay soil or sandy soil?
14. (a) What is the ecological problem illustrated in the photo below? (b) Name the human activity that may have caused the situation.
2. Describe the three layers of soil. 3. Why is humus important for healthy soil? 4. Why is it important to test for bacteria in water reserved for human use? 5. What indicators can be used to test water quality? 6. How is the water table connected to the soil? 7. Define a heavy metal, and give three examples.
Connect Your Understanding 8. Explain why topsoil is a vitally important layer of soil. 9. At which level of the food chain does biomagnification have the most impact? Explain. 10. What properties of plastic make it a dangerous pollutant in aquatic ecosystems? 11. Explain how the presence of coal-fired electricity plants can affect the ability of lakes to support life. 12. Suppose that there has been a sudden growth of algae in a lake in cottage country. (a) Suggest three possible causes for this situation. (b) Explain what could happen in the lake.
Question 14
15. Acid rain is not just a Canadian problem. It is an international problem. Justify this statement. 16. In the 1980s, lakes and forests in eastern Ontario were affected by acid rain. Describe the effects the acid rain might have had on the terrestrial and aquatic ecosystems.
Reflection 17. You can be a part of solution to the various problems you learned about in this section. Does your lifestyle affect neighbouring bodies of water? Identify any habits that you or your family have that may have an impact. How can you change your habits so that you do not negatively affect the water cycle? For more questions, go to ScienceSource.
13. Manure is often used by gardeners to fertilize soil. How might this be effective in replenishing soil nutrients?
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CAREERS
in Science
Great CANADIANS in Science
David Suzuki
Investigating
Figure 2.41 Dr. Suzuki visits students at William Lyon Mackenzie Collegiate to congratulate them on creating a renewable energy project. Figure 2.42 Dr. Suzuki answers questions at a press conference about Canada’s environmental priorities.
Dr. David Suzuki is an environmentalist, broadcaster, and scientist. As the cofounder of the David Suzuki Foundation, he has devoted an enormous amount of his time to saving the ecosystems of the world. The foundation focusses on four main areas: oceans and sustainable fishing; climate change and clean energy; sustainability; and the Nature Challenge. Through science and education, the foundation encourages solutions that will conserve nature while achieving sustainability within a single generation. The use of science and education are key to how Suzuki increases environmental awareness. The Nature of Things is a television science magazine show, which is hosted by Suzuki. Suzuki uses the show to engage viewers in the natural world, point out threats to human well-being and the environment, and offer ideas for how to achieve a more sustainable future. With 6.6 billion
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human inhabitants, the biosphere is under tremendous pressure to support everyone’s needs. Suzuki is inspired by the energy of today’s youth. He is encouraged to see students using tools such as blogs, email, podcasts, and social networking sites to spread the message about protecting the biosphere. The future depends on it!
Questions 1. What has David Suzuki done to increase awareness of sustainable ecosystems? 2. Go to ScienceSource to research David Suzuki’s Nature Challenge. List three things you can do right now to live a greener life. Try them out for a week. How easy or hard were they to do?
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Ecological Consultant
Figure 2.43 An overpass being built for the Red Hill Valley Expressway in 2003. The expressway opened in 2007. Figure 2.44 Ecological consultants spend time in the field collecting data.
As people and businesses become more aware of the stresses on ecosystems, they are starting to think more critically about their actions. An ecological consultant helps people make those decisions by doing many of the following things: • providing data and recommendations on lessening impacts on the environment • doing landscape assessment and planning • ecological monitoring and research • creating materials for educational workshops and public consultations • providing logistical support for municipal environmental strategies • providing expert testimony in environmental trials The construction of a new highway through the environmentally sensitive Red Hill Valley in Hamilton is a typical project that requires the services of an ecological consultant (Figure 2.43). On this project, ecological consultants ensured
that environmental concerns were being addressed before any construction began. A consultant’s job varies greatly depending on the client, the season, and the type of environment. However, it includes writing proposals and reports, working with clients, making presentations, and managing support staff. Field work is mostly done during the summer (Figure 2.44), and research, designs, and reports are mostly done during the winter. Most ecological consultants are passionate about their work. They help to find a balance between ecosystem health and human needs.
Questions 1. Write a short paragraph explaining what the typical day or week in the life of an ecological consultant would look like. 2. Go to ScienceSource to research what education or training is needed to become an ecological consultant.
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CHAPTER REVIEW
ACHIEVEMENT CHART CATEGORIES k Knowledge and understanding t Thinking and investigation c Communication
a Application
Key Concept Review 1. What negative effect can habitat change have on native species? k 2. (a) What is causing climate change?
k
(b) Describe the impact climate change is having on an Arctic species. k 3. What is the relationship between dissolved oxygen and biological oxygen demand? k 4. Classify the following pollutants as either point source or non-point source. k (a) excess fertilizer from fields (b) pesticide residue from local gardens (c) discharge of waste water from a cruise ship (d) leaking storage tanks (e) a leaking landfill (f) animal waste treatment facility (g) sediment from a clear-cut forest (h) stormwater from an urban parking lot (i) bacteria from pet wastes 5. Give an example of overexploitation in a marine environment. k
8. If too much sewage is added to water, the aquatic organisms may die due to lack of oxygen. Explain how this might occur. k 9. Explain habitat fragmentation, and suggest ways in which it could degrade the quality of an ecosystem. k 10. What advantages might an introduced species have when competing with native species? k
Connect Your Understanding 11. Explain how irrigation systems might actually cause a decrease in water quality.
12. Many potential home buyers want lots of trees around their homes. A housing developer builds a residential community in a forested area. To show his ecological responsibility, he leaves patches of the forest untouched and builds roads to connect the various parts of the development. Critique how ecologically responsible the developer’s actions are. a 13. The human activity pictured below may affect biodiversity. Create a concept map that shows how the activity may affect biodiversity. c
6. List some chemical indicators that can be used to test water quality. k 7. (a) What is acid rain?
k
(b) What are the causes of acid rain?
k
(c) List ways that acid rain affects a terrestrial ecosystem. k Question 13
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a
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14. Suppose that a homeowner wishes to start a small garden in her backyard. Why is it important that she determine the type of soil she has before planting any vegetables? a
(a) Graph the data.
15. How might biodegradable plastics help reduce pollution? a
(c) The name “dead zone” is given to the zones in aquatic ecosystems that do not have enough oxygen to support life. Why is this name appropriate? t
16. Consider the following hypothetical situation. Suppose that a factory emits a number of pollutants that cause health problems in young children and the elderly. This factory also employs 50 percent of the town’s residents directly and indirectly, and closing the factory would cause severe financial hardship in the town. Forcing the factory to clean up its emissions would also cause the company to lose money and make it difficult for it to compete with similar companies. You are the mayor. Suggest an action plan for your town that will help to deal with this crisis. a
(b) Which months have dissolved oxygen levels that are too low to support aquatic life? t
(d) Create a hypothesis that might explain the trends in the data. t (e) What changes could be made to correct this situation? t
Reflection 18. The World Water Council ranked Canada second out of 147 countries in terms of water sustainability. However, Canada ranked 129th in terms of responsible water use. How could you change your actions to improve this placement? c
17. The data in the table gives the average dissolved oxygen values in the Gulf of Mexico. Normal seawater has at least 6.9 mg/L.
After Reading
Dissolved Oxygen Values
Reflect and Evaluate
Month
Dissolved Oxygen (mg/L)
Month
Dissolved Oxygen (mg/L)
Jan 1
8.5
Jan 15
9.0
Feb 1
8.5
Feb 15
9.0
Mar 1
8.0
Mar 15
7.5
Apr 1
5.0
Apr 15
3.5
May 1
2.0
May 15
3.0
June 1
0.0
June 15
1.0
July 1
1.0
July 15
0.0
Aug 1
0.0
Aug 15
0.0
Sept 1
0.0
Sep 15
0.0
Oct 1
3.0
Oct 15
4.5
Nov 1
6.5
Nov 15
7.5
Dec 1
8.0
Dec 15
7.5
c
With a partner, share and summarize some of the questions you posed during this chapter. Compare any conclusions you drew. Write a three-sentence resolution about ways that you will both be more responsible in how you deal with ecosystems in the environment. Share your resolutions with another pair of students.
Unit Task Link In this chapter, you have learned about the negative effects human activities can have on ecosystems. In the Unit Task, you will be designing a sustainable community. Think about ways you could lessen habitat loss/fragmentation, pollution, and overexploitation in your sustainable community.
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Governments, groups, and individuals work together to promote sustainable ecosystems.
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Skills You Will Use This farmers market is in the Kitchener area. Using farmers markets is one of the many actions that groups and individuals are taking to live in a more sustainable way.
In this chapter, you will: • find sources of information that are relevant to the questions you are researching • select, organize, and record the relevant information you find as you research a topic
Concepts You Will Learn In this chapter, you will: • assess the impact of a human activity that threatens the sustainability of an ecosystem • evaluate the effectiveness of actions people are taking to ensure that ecosystems are sustainable.
Why This Is Important You need to know what actions governments, organizations, and individuals are taking to correct the damage humans have done to ecosystems. Once you know the things they are doing, you can evaluate whether their actions are effective. You can also decide what types of actions you can take to help the environment.
Before Writing Preparing to Select and Organize Information When you are researching a topic, not all the information that you read will be useful to you. Get in the habit of deciding what’s truly important and what’s not essential. As you think about issues related to sustainable ecosystems, skim section 3.1 and decide which information could be truly useful and which is just nice to know.
Key Terms • at risk • ecological footprint • endangered • environmental steward • ex-situ conservation • extirpated • in-situ conservation • integrated pest management • special concern • threatened
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Government Action to Protect Canada’s Ecosystems
3.1
Here is a summary of what you will learn in this section: • Conservation biology works to protect biodiversity, partly by assessing which species are at risk of extinction and developing strategies to protect these species. • Species at risk are protected in their own surroundings by improving their habitat or by removing them from the wild until their wild habitats can be restored. • Governments use laws to enact programs to protect ecosystems. Figure 3.1 Many people enjoy Lake Erie.
Lake Erie: “The Comeback Kid”
Figure 3.2 A pulp and paper mill dumps polluted waste water directly into Lake Erie in the 1970s.
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Lake Erie, the shallowest and smallest of the Great Lakes, can be the ultimate Canadian getaway. Because the lake is shallow, it warms quickly in the summer. This makes it popular for many different recreational activities (Figure 3.1). In the 1970s, Lake Erie was very different. Its water was full of sewage, farm chemicals, and industrial chemicals (Figure 3.2). This chemical “soup” had the potential to cause a collapse of the entire lake ecosystem. The most visible example was runaway algae growth, which left an unsightly scum across the lake. When the algae grew, it choked out other organisms. When it died, its decay removed dissolved oxygen from the water, causing massive fish kills. How did this come about? There are many pressures on the lake. More than 12 million people live near its shores. The Lake Erie watershed is one of the most intensely farmed regions on the continent. With population growth came industry. Many people, though not all, operated for decades on the assumption that the lake was so large that it could safely absorb any amount of substances put into it by humans. By the 1970s, the effects of this approach had produced a smelly lake filled with sick or dead fish. No one wanted to go near Lake Erie.
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Governments Take Action In 1978, the United States and Canadian governments signed the Great Lakes Water Quality Agreement. Its goal was to restore the chemical, physical, and biological integrity of the Great Lakes in a co-ordinated way. As a result, the Ontario provincial government and various U.S. state governments created management plans to clean up each of the Great Lakes. One of the many actions proposed in Lake Erie’s management plan was to restore wetlands along its shores. In addition to restoration projects, the Essex County Stewardship Council has helped private landowners create new wetlands on their land. These wetlands filter the water entering the lake and remove contaminants from it. The amount of chemical fertilizer, pesticide run-off, and untreated sewage entering the lake was also reduced. As a result, Lake Erie has made a significant recovery, though there is still much work to do. Lake Erie’s ongoing restoration is an example of the power of collective action. When governments, groups, and individuals work together for a common purpose, great things are possible.
A19 Quick Lab Modelling a Wetland Plants can purify water as they live and grow. In this activity, you will investigate this process.
Purpose To model a wetland removing chemicals from water
Materials & Equipment • 50-mL beaker • 2 large test tubes and stoppers • warm water • phenol red indicator
2. Add five drops of phenol red solution to the beaker, and use a straw to blow bubbles into it until the solution just turns yellow. 3. Fill two test tubes three-quarters full with the solution. 4. Place an aquatic plant into each test tube, and seal each test tube tightly with a stopper. 5. Wrap one of the test tubes with aluminum foil. Put the foil-wrapped test tube in a dark place, and place the unwrapped test tube under a bright light. After 20 min, observe each one.
• straw • 2 aquatic plants • aluminum foil • bright light source
Procedure 1. Fill a beaker with 50 mL of water.
Questions 6. The colour change that occurred in step 4 was a result of removing carbon dioxide from the solution. Consider which tube the colour change occurred in, and explain how carbon dioxide was being removed. 7. Explain how this model demonstrates the ability of a wetland to purify water. Governments, groups, and individuals work to promote sustainable ecosystems.
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Conserving Biodiversity The modern science of conservation biology seeks to understand and protect biodiversity. Part of this task includes assessing which species are most in danger of extinction as well as developing strategies to protect them.
Species at Risk If you had strolled through meadows near Peterborough sometime in the 1900s, you might have seen the bright blue wings of a Karner blue butterfly as it flew from plant to plant. Today, this would be impossible because the butterfly no longer exists in Ontario. Luckily, it still exists in small populations elsewhere in North America. Around the world, extinctions are happening at a rapid rate. But species do not become extinct overnight. When populations of a species decline over time, the species may be at risk. At risk means any native species that is in danger of becoming extinct or disappearing from a region. There are different levels of risk (Table 3.1). Table 3.1 Definitions of Some Risk Levels for Species
Figure 3.3 Some at-risk species in Ontario. (a) The Karner blue butterfly is extirpated. (b) The eastern prairie fringed orchid is endangered. (c) The eastern Massasauga rattlesnake is threatened. (d) The red-headed woodpecker is of special concern.
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Level of Risk
Definition
Extirpated
A species that no longer exists in Ontario but still occurs elsewhere
Endangered
A species that faces extinction or extirpation
Threatened
A species that is at risk of becoming endangered if limiting factors are not reversed
Special concern
A species with characteristics that make it sensitive to human activities or natural events
(a)
(b)
(c)
(d)
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There are currently over 200 species at risk in Ontario (Figure 3.3). There are two conservation strategies that governments and groups are using to protect biodiversity.
Conservation Strategies One problem in conserving biodiversity is that plants and animals do not recognize national boundaries. In order to co-ordinate conservation efforts, governments of different countries use international treaties. A treaty is an agreement, usually between nations, in which they agree to do certain things to achieve a common goal. The Convention on Biological Diversity is the name of an international treaty whose goals are to conserve Earth’s biodiversity and to use this biodiversity in a sustainable way. The Convention on Biological Diversity has been signed by 161 countries, including Canada. It makes use of two broad strategies: one is to protect species in human-made environments such as zoos, while the other protects species in their native habitats.
During Writing Making Notes As you research, take notes in point form. Never copy word for word. Instead, choose key words, definitions, and any direct quotes that will support your writing purpose.
Protecting Species in Human-Made Habitats The black-footed ferret was extirpated in Canada in 1937, and by the 1980s, only 18 individuals remained in Wyoming. The decision was made to capture these individuals and take them to various zoos, including the Metro Toronto Zoo. This is an example of ex-situ conservation (Figure 3.4).
Figure 3.4 The Metro Toronto Zoo maintains a population of black-footed ferrets through its captive breeding program. Governments, groups, and individuals work to promote sustainable ecosystems.
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Figure 3.5 Constructed 120 m below the ice on an island in the Arctic Ocean, the Svalbard Seed Bank can conserve up to 4.5 million seeds. These seeds can act as a backup for any plants that have been lost due to accidents, mismanagement, or natural disasters.
W O R D S M AT T E R
“In situ” is Latin for in the original place, and “ex situ” is Latin for out of the original place.
Figure 3.6 A loggerhead shrike
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Ex-situ conservation conserves species by removing them from their natural habitats. This strategy is used when a species’ habitat is threatened or no longer exists, or if the existing population is extremely small. The at-risk individuals are taken to zoos, botanical gardens, or reserves. Zoos play an active role in preserving biological diversity through breeding programs and other efforts. Many zoos across North America participate in Species Survival Plans (SSPs). SSPs are breeding programs specifically for species threatened with extinction. The strategy seems to have worked for the black-footed ferret. The Metro Toronto Zoo’s SSP has been very successful, and hundreds of ferrets have been reintroduced to protected areas in the U.S. prairies. The zoo and various other organizations are currently developing plans to reintroduce the ferret into Grasslands National Park in Saskatchewan. Seed banks are an additional ex-situ conservation strategy (Figure 3.5). Seeds of endangered plants and rare crop plants can be stored in seed banks. Seed banks may be used to maintain the ability to restore the population even if it completely disappears from the wild. Protecting Species in Their Native Habitats Ex-situ conservation is considered a strategy of last resort. In-situ conservation focusses on conserving species in their natural surroundings. In-situ conservation uses many strategies, but the main one is protecting species’ habitats. For example, the endangered eastern loggerhead shrike needs short grasslands surrounded by trees, shrubs, and hedgerows (Figure 3.6). Much of this habitat has been lost by farmers removing hedgerows and converting pastureland to other crops. By getting farmers to preserve their pastureland and hedgerows, the shrike’s habitat is maintained and the population may increase. Another strategy is to help protect a species from its predators. For example, female Blanding’s turtles leave their eggs in buried nests. The eggs are vulnerable to raccoons and coyotes, who dig up the nests. One strategy is to protect nest sites by fencing them off. Other strategies include cleaning up or restoring habitat or isolating a habitat from human activity by creating reserves. For animals, this usually means establishing large enough land reserves to allow the population to recover to sufficiently large numbers. Recall that biodiversity means much more than just having many different kinds of species in an ecosystem. A population
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within an ecosystem must have sufficient genetic diversity to be able to adapt to changing circumstances and to evolve over time. When a large population is brought back from just a few surviving pairs, all the offspring are very closely related. A single disease could wipe out the entire population in one epidemic. This problem rarely occurs in a healthy, genetically diverse population. In-situ conservation helps keep organisms interconnected with their habitat and, over time, helps re-establish genetic diversity.
Learning Checkpoint 1. What is the difference between a species that is endangered and one that is threatened? 2. What is a treaty? 3. What are the two main conservation strategies endorsed by the Convention on Biological Diversity? 4. Which of the two strategies in question 3 is considered to be a strategy of last resort? Why is it a last-resort strategy? 5. Explain the importance of genetic diversity within a species.
Protecting Endangered Species The American badger is endangered in Ontario (Figure 3.7). Fewer than 200 individuals remain in isolated pockets, mostly on private land. In 2007, the Ontario government passed the Endangered Species Act. This law prohibits killing, capturing, possessing, selling, or trading species that are endangered in Ontario. The law not only protects at-risk species, it protects their habitats as well. This means that it becomes illegal to damage or destroy ecosystems that the species depends upon. This gives developers, local governments, and people who live or work in the habitat direction as to what is or is not permissible in a given situation. For example, landowners that have American badgers on their property are responsible for preserving the badgers’ habitat. The law has some flexibility so that local concerns about resource use in a particular habitat can be addressed. However, individuals or groups that ignore the law can be accountable and financially liable for repairing the damage they cause.
Figure 3.7 The badger’s main food is woodchucks and rabbits, which it catches by digging into their burrows.
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Establishing Protected Areas Establishing protected areas is one method to slow down the loss of biodiversity. Protected areas include national and provincial parks, wildlife reserves, and marine sanctuaries. Choosing which areas to protect can be a challenge. Worldwide, conservation biologists have identified “biodiversity hot spots,” areas that have many unique ecosystems and whose biodiversity is threatened (Figure 3.8). These areas contain species found nowhere else on Earth. Many of these species are endangered. The Role of Parks In Ontario and the rest of Canada, parks and wilderness areas protect ecosystems by keeping them relatively undisturbed. Leaving ecosystems undisturbed helps conserve biodiversity. Figure 3.8 The biodiversity hot spots are shown in orange on the map.
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Figure 3.9 Algonquin Park receives about six million visitors a year.
Another role of parks is to allow humans to enjoy these ecosystems. Sometimes, this is difficult. For example, Algonquin Park is one of Ontario’s larger provincial parks, but it is also one of the most heavily visited (Figure 3.9). Parks officials work hard to balance humans’ need for recreation with ecosystems’ need to remain undisturbed.
Creating Action Plans to Restore Ecosystems As we have seen, many human activities cause damage to the natural environment. Remedial action plans involve governments, industries, and community groups working together. For example, the St. Lawrence River near Cornwall had many environmental problems, including bacterial and heavy-metal contamination and habitat destruction. The first stage of the remedial action plan for the area was to identify the specific causes of the problems. In the next stage, government agencies, industry representatives, and community groups met to develop specific plans to fix the problems. As a result, Cornwall’s municipal government improved its sewage treatment plants to reduce bacterial contamination in the river. Domtar Fine Papers’ pulp and paper mill improved its waste water treatment process to reduce the amount of heavy metals entering the river. Also, various agencies built artificial reefs and small wetlands along the shore to improve fish habitat. The third stage of remedial action plans is to monitor conditions to check that the actions taken are working. In Cornwall, the actions seem to have worked. Water quality as well as fish diversity and populations are starting to improve. But there is still more work to be done.
Suggested STSE Activity • A20 Decision-Making Analysis on page 102
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Figure 3.10 Because plants take time to grow, habitat restoration often takes many years to complete.
Many wetlands in Ontario have been threatened by population growth, farming, and industrial activities. One major focus of remedial action plans is habitat restoration, such as returning a disturbed wetland to a condition as close to its original state as possible (Figure 3.10). For example, the Oshawa Second Marsh has been undergoing a complex clean-up and replanting to restore it.
Preventing the Introduction of Invasive Species Ontario is home to many species of hardwood trees, including the sugar maple. These trees have evolved for thousands of years and adapted to life in this region. The Asian long-horned beetle, a species native to China, was first detected in North American forests in 1996 (Figure 3.11). It may have arrived in wooden packing crates used to deliver goods from Asia. These beetles are now a serious threat to hardwood tree species in Ontario. Various levels of government are involved in preventing the spread of the Asian long-horned beetle. For example, the City of Toronto is trying to stop further spread of the beetle by establishing by-laws against moving firewood and other wood products that may contain the beetle (Figure 3.12).
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Take It Further According to some estimates, species are going extinct at a rate of 1 every 20 minutes. Data collected by ecologists are combined with models to calculate this average rate. The model helps estimate how many species are currently on the verge of extinction. Go to ScienceSource to find out more about the model. Figure 3.11 The Asian long-horned beetle was first discovered in Toronto and Vaughn in 2003.
Figure 3.12 The City of Toronto, the Municipality of Vaughn, and Agriculture Canada are working together to prevent the spread of the beetle.
Also, Agriculture Canada, a branch of the federal government, has strict laws against citizens or visitors bringing foreign food, animals, or plants into the country. This helps prevent people from unwittingly introducing foreign organisms into Canada’s ecosystems (Figure 3.13).
Figure 3.13 This sniffer dog at Pearson International Airport is trained to detect food and plants in luggage.
Learning Checkpoint 1. List four ways in which governments can help sustain biodiversity. 2. (a) How does the establishment of protected areas help sustain biodiversity? (b) What are three types of protected areas used by governments to do this? 3. What is a remedial action plan? Give an example of such a plan. 4. What organism currently threatens Ontario hardwood species, and what government actions are being used to slow its spread?
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DI Key Activity
A20
STSE Decision-Making Analysis
Skills Reference
4
Identifying and locating research sources Thinking critically and logically
Assessing a Government Program — Recycling Issue Recycling programs divert wastes from landfills. Recycling was practically unknown only a generation ago. Now, all municipalities in Ontario participate in some form of recycling program. It is not without its difficulties, and making it possible to connect everyone into a recycling network is still a major goal.
Background Information Garbage disposal is a major issue for many municipalities across Ontario because the use of landfills only is not a sustainable approach. Landfills have a tendency to fill up. Building new landfills is expensive, and local residents are usually reluctant to have them near their property. Chemicals can leak out of an improperly constructed landfill. Heavy metal contamination from old batteries and electronics is just one example. Blue and grey boxes, green bins, and yard waste composting programs have generally been successful in Ontario (Figure 3.14). For example, in the City of Toronto, 42 percent of residential waste is redirected from landfills through recycling programs. However, apartment dwellers recycle only 13 percent of their garbage. Suppose that you have been hired by your local council to create an action plan to increase participation in the local recycling program. The council wants you to find out which groups cannot or will not participate in the current recycling program.
They also want you to suggest ways to increase participation. Be aware that some members of the council do not see the benefits of recycling. In order to make the case for expanding the recycling program, you have to outline the benefits to them as well.
Analyze and Evaluate 1. ScienceSource On the Internet, find information about the diversion of solid waste from landfills. Also look in print materials for information on waste diversion from landfills. 2. Research your local recycling program. Find brochures, fact sheets, and newspaper articles to answer the questions below. • Who can participate in the program? Businesses, single-family dwellings, apartment buildings? People in rural areas? • How does it work? Is there curbside pickup, or do residents have to take their recycling to a depot? • Is it difficult for some groups to participate? If so, which groups, and why? 3. Use your research to develop a plan that could improve current recycling efforts for the groups you have identified that have trouble participating. 4. Web 2.0 Develop your findings about recycling for the local council in the form of a Wiki, a presentation, a video, or a podcast. Make sure to outline your action plan to improve participation in the recycling program.
Skill Practice 5. Prepare a five-point summary specifically designed to explain the benefits of recycling to someone who may not think recycling is worthwhile. Figure 3.14 Some municipalities do not have curbside pickup for recycling.
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CHECK and REFLECT
Key Concept Review 1. What is the role of conservation biology in ecosystem management? 2. List four levels of classification of at-risk organisms, and explain the meaning of each.
13. The grey fox, pictured in the photograph, is threatened in Canada. It is estimated that there are at least several thousand breeding pairs. Would in-situ or ex-situ methods be most appropriate to protect this species? Explain.
3. Give an example for both in-situ conservation and ex-situ conservation. 4. What is the difference between extirpated and extinct? 5. List two approaches that the Convention on Biological Diversity uses to help conserve species. 6. What are two major roles for zoos? 7. What are the advantages of protecting a species without removing it from its natural habitat? 8. How does the Ontario Endangered Species Act work to protect at-risk species?
Connect Your Understanding 9. Why is it important for there to be an agreement between Canada and the United States to help rehabilitate the Great Lakes? 10. Suppose the Canadian government has decided to create more national parks. You have been asked to decide which places should be considered as potential sites for parks. How would the concept of biodiversity hot spots help you make decisions? 11. How has the rehabilitation of the Great Lakes helped to ensure ecological sustainability? 12. Propose a course of action to successfully reintroduce the Karner blue butterfly to the meadows near Peterborough.
Question 13
14. Canadian border officials allow a family to bring a box of grapefruit home to Canada from their trip to Florida. However, United States border officials confiscate a box of grapefruit that another family wishes to bring with them on their trip to the U.S. Propose a reason for the different responses to the grapefruit by U.S. and Canadian officials.
Reflection 15. This section identified different actions that governments can take to ensure the sustainability of ecosystems. Which of the actions interested you the most? Why? 16. How can you, as an individual, have an impact on the way your municipal, provincial, or national government takes care of ecosystems? For more questions, go to ScienceSource.
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Environmental Stewardship
Here is a summary of what you will learn in this section: • Ecological footprints show individuals, groups, or nations how much land is needed to produce what they consume and absorb their wastes. • Environmental stewardship means taking care of resources in a sustainable way. • Organizations and individuals are taking action to make sure we use resources in a sustainable way.
Figure 3.15 An artist’s rendition of the restored Brick Works, once it is completed.
The Toronto Evergreen Brick Works
Figure 3.16 The Brick Works farmers market opened in 2007 and has been a great success.
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What happens when you combine leading-edge technologies in sustainability, support for local food producers, use of abandoned heritage buildings, and a way to connect a city community with its own local ecosystem? In Toronto, the result is Evergreen Brick Works, an urban restoration project (Figure 3.15). The Brick Works was originally built in 1889 on a flood plain in the Don River Valley, in the heart of the city. The factory produced many of the bricks used in many of Toronto’s buildings, as well as buildings across Ontario and Canada. As the city grew, the Don Valley was spared from development because the river flooded occasionally. This helped keep the area available as parkland. The Brick Works closed in the 1980s, and the buildings were abandoned. Today, these abandoned buildings are being transformed into a national centre for environmental education. The centre will offer programs on how to integrate sustainability into daily living. One of the first projects to open was a farmers market. Every weekend, it is filled with shoppers (Figure 3.16). The market supports local producers and connects consumers with high-quality, locally produced food.
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Restore, Reduce, Renew The restoration plan for one of the buildings includes many measures to reduce the building’s environmental impact. It incorporates a vertical garden or “living wall” to help moderate the building’s temperature. To reduce the need for heating and cooling, a series of movable panels on the exterior walls shade the building in summer and help to warm the building in winter. Large-scale art installations can be attached to the panels. The Don River is also being restored to make its banks more suitable for native species to thrive. In this way, both the lands and the buildings are undergoing renewal. Evergreen Brick Works is one of many examples of how environmental stewardship continues to take hold in our society (Figure 3.17).
Figure 3.17 Evergreen Brick Works site in the Don Valley
A21 Quick Lab Making Connections “Environmental stewardship” is a term that relates many ideas that you have studied in this unit. In this activity, you will have an opportunity to recall the meanings of some of these ideas and will practise connecting them in sentences.
Purpose To make connections between concepts related to environmental stewardship
Environment factor, and the third corresponds to an Impact factor. For example, if the first roll is 4, then the factor is “regulations.” 3. The roller now creates one to three sentences that connect the three terms together. 4. While the first roller writes, the other partner does steps 2 and 3. 5. Repeat as many times as time permits.
Questions
Materials & Equipment • 1 six-sided die
6. Share with your class the best sentence that you came up with, and explain why you think it worked so well.
Procedure
7. List any combinations of words that did not work well together, and suggest a reason why this was the case.
1. Pick a partner. 2. To start, one partner rolls the die three times. The first roll of the die corresponds to a Society factor listed below, the second corresponds to an
8. Think of one new word for each category, and write a sentence connecting the new words.
Society
Environment
Impact
1 Conservation 2 Culture 3 Politics 4 Regulations 5 Consumption 6 Recycle
1 Nutrients 2 Water 3 Air 4 Soil 5 Habitat 6 Energy
1 Overexploitation 2 Habitat change 3 Invasive species 4 Pollution 5 Climate change 6 Technology
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Ecological Footprint
Suggested Activity • A23 Quick Lab on page 115
An ecological footprint is an estimate of how much land and water is needed to support your lifestyle (Figure 3.18). This includes all the land and water needed to produce the resources you consume as well as absorb all the wastes you produce. The wastes include all the emissions produced in manufacturing the products you consume. All the things that ecosystems provide are also considered to be a part of your ecological footprint, including providing fresh water and decomposers that recycle wastes.
Figure 3.18 A person’s ecological footprint includes the space needed for extracting energy, living and working, manufacturing and waste disposal, growing food, and extracting resources (timber, pulp and paper, textiles).
Table 3.2 Some Other Nations’ Footprints Country
Footprint (ha/person)
India
0.86
Pakistan
0.64
Japan
4.77
United States
9.57
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The average Canadian requires 8.9 ha to maintain his or her lifestyle. This is equivalent to about 17 football fields. If everyone on Earth had the same ecological footprint as a typical Canadian, we would need 5.7 Earths! The size of people’s ecological footprints varies widely throughout the world (Table 3.2). An ecological footprint is a tool that can be used to determine how much resources a person, an organization, or even an entire country consumes. Once we know our ecological footprints, individuals, organizations, and countries can then know to what extent they need to engage in more sustainable activities. Many Canadian municipalities are now using ecological footprints to measure their progress towards sustainability. A large number of environmental stewardship programs also calculate ecological footprints in order to evaluate their progress. An ecological footprint can be calculated for a person, a building, a nation, or a whole continent.
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Scientists are concerned that as populations increase and consumption of resources also increases, at some point, the world’s ecological footprint will eventually equal all the available land and water on Earth. A number of estimates now suggest that we reached that point in 1990. From that time on, we have been consuming Earth’s resources faster than the planet can regenerate them. We live in a unique and risky period where we consume more than Earth can produce. We have to change the way we use Earth’s resources.
Environmental Stewardship A good steward is someone who manages any sort of resource wisely. Being an environmental steward means taking care of our natural resources to ensure that they are used in sustainable ways for current and future generations. Stewardship includes activities such as reducing the amount of resources we use, reusing items instead of throwing them away, and recycling used items. It also includes conserving existing ecosystems and restoring damaged ones. To be successful, environmental stewardship requires governments, organizations, and communities to work to prevent or reduce threats to ecosystems.
Suggested Activity • A24 Quick Lab on page 115
Sustainable Agriculture In the 1980s, a group of Ontario farmers were worried about the effects that some farming methods were having on the environment. For example, some were concerned about the effects that fertilizers were having on water quality. Others were concerned that their tilling methods were causing soil erosion. Together, they developed plans to address problems related to pollution from farms. With the assistance of the federal government and agriculture organizations, they developed a program called the Environmental Farm Plan (EFP). The EFP is a tool that farmers can use to identify environmental problems on their farms and develop action plans to address these problems (Figure 3.19). For example, pesticides can have many negative effects on ecosystems. In the 20 years since the EFP started, pesticide use has been reduced by 50 percent on Ontario farms. EFPs are now being used on farms across Canada. Environmental farm plans can include actions such as using integrated pest management, which is a method of pest control
Figure 3.19 Environmental Farm Plans have become a useful tool for Ontario farmers.
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that uses knowledge about a pest’s biology and habitats. The technique is to choose the best combination of common-sense methods to keep the pest population under control, rather than using pesticides to totally eradicate them. For example, rotating different crops in the same field each year can be used to control pests that only eat one of the two crops. If the pest has nothing to feed on, its population drops. Reducing pesticide use helps the surrounding ecosystems and it also reduces risks to human health.
During Writing Organizing for Writing Once your research is complete, begin to organize your notes. Create headings for major subtopics, and gather your notes under each heading. If you use sticky notes to record your research points, then you can arrange and rearrange them under the appropriate headings to create maximum impact.
Soil Conservation and Organic Farming Soil is a limited resource. It takes hundreds of years to form, but it can be blown or washed away very easily. Soil conservation means using farming methods that protect the soil from erosion and loss of nutrients. No-till farming is a method of planting and growing crops from year to year that does not disturb the soil (Figure 3.20). This means leaving the stubble and roots of last year’s crop in the soil. The roots hold the soil and prevent erosion. The next year’s crop is planted among the stubble. However, not all crops can be grown using no-till farming. Some farmers use organic farming. On organic farms, farmers do not use chemical fertilizers or pesticides. This helps to reduce water pollution. However, organic farms may not be able to produce the same amount of food as a non-organic farm.
Figure 3.20 A new crop of soybeans is growing among the stubble of last year’s corn crop in a no-till field.
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Eating Locally Produced Foods Your lunch may have contained oranges from South Africa or apples from New Zealand. Before modern refrigeration processes and efficient transportation networks, most foods were consumed close to where they were produced. We have benefited from being able to move foods great distances very quickly. We can now eat fresh fruit and vegetables in the middle of winter. Currently, in North America, many foods are grown and processed on a very large scale. It is very efficient, but it can lead to problems. Most food items, including fruits and vegetables, are packaged or processed in large, centralized processing plants and then shipped all over the continent. If food spoilage or contamination is found in one of these centralized plants, food that has already been distributed has to be recalled and removed from supermarket shelves all over North America. This is costly and time-consuming. Decentralized food production can help reduce this problem. Also, the amount of energy needed to bring California-grown strawberries to Ontario is much greater than the amount needed to bring Ontario-grown strawberries to a local farmers market. Sustainable agriculture and eating locally produced foods, if they are available, are connected. Buying locally produced food supports local farmers. If these farmers get enough income from their farms, they will continue to use their land for agriculture rather than selling their land to be developed for housing or other purposes. Locally grown produce tends to be fresher because it has been picked more recently than produce grown in California or other distant areas (Figure 3.21). In season, you might be able to eat corn that was picked less than 24 hours before. Even when more food is sustainably produced, some foods will have to be transported long distances, especially in Ontario, where our growing seasons are relatively short.
Figure 3.21 The Niagara region produces many fruits such as peaches, apples, and plums.
Learning Checkpoint 1. What is meant by the term “ecological footprint”? 2. What do calculations of the total ecological footprint of all of humanity say about our current use of Earth’s resources? 3. What does it mean to be an environmental steward? 4. What is an Environmental Farm Plan? 5. How is soil conservation related to sustainable agriculture?
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Sustainable Forestry The Forest Stewardship Council of Canada (FSC) is a non-governmental organization, or NGO. This means it operates independently of any government. The FSC originated in Ontario but now operates around the world. This organization sets standards for sustainable forest management and certifies forests and forestry practices that meet their standards. For a forestry practice to be certified: • Waterways and wildlife habitat have to be protected. • Parts of the forest have to be preserved. • The cut areas have to be replanted. • The cut areas cannot be replanted with just a single species. The forest must be able to achieve a wild state. Figure 3.22 The FSC’s tree check logo identifies products as being produced from wood from sustainably managed forests.
The FSC also provides a way for consumers to know whether the wood or wood product they are planning to buy has been made without endangering an ecosystem. For example, someone who wants to buy a wooden bench can look for an FSC symbol on the product (Figure 3.22). The symbol indicates that the wood was obtained in a responsible manner. There are different sustainable management standards for different types of forests and different locations. For example, there is one set of standards for national boreal forests and a different set of standards for British Columbia’s forests. However, this is taken into account in the certification process, so the consumer simply has to look for the logo on the product to know the appropriate standards were followed. Urban Forests It is easy to think of forests as existing only away from settled areas, but there are urban forests too (Figure 3.23). Like a wild forest, an urban forest includes all the trees and shrubs present as well as their soils. Healthy urban forests can help communities achieve many sustainability goals, such as removing excess carbon from the atmosphere. Trees store carbon and continuously remove it from the atmosphere. Large trees can remove 50 times more carbon than small trees can. They also reduce energy consumption by providing shade. If urban buildings are shaded, the need for air conditioning is reduced. Less air conditioning means less energy consumption. Urban forests provide many other benefits as well. They help slow the run-off of water from rainstorms. This reduces the
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Figure 3.23 Part of Ottawa’s urban forest
pressure on a city’s storm-drain system. Trees protect soils from erosion and filter chemicals from water and air. Urban forests can actually help repair damaged ecosystems by repairing unhealthy or damaged soils. They also provide habitat for other species, so they help increase biodiversity. And, of course, trees are also enjoyable to look at and be around. Many cities and municipalities realize the importance of planting and maintaining healthy trees on public land. Most have urban forestry departments. The many trees on private land are vital too. There are many different organizations that educate the public about planting trees. For example, Tree Canada is an organization that promotes planting trees on both public and private land. In the last week of April, Arbour Week focusses on educating the Ontario public about the advantages of planting trees.
Sustainable Construction Most people in Canada spend a lot of time in buildings, especially in the winter. The thousands of large buildings and millions of homes in Canada have a significant effect on the environment. Building them, living in them, and heating and cooling them uses energy, uses many different resources, and produces many different types of pollution. Sustainable construction methods help reduce these impacts. Just as it is possible to certify a forest as being used in a sustainable way, buildings can be certified as being built in a sustainable way as well. The Canada Green Building Council uses the Leadership in Energy and Environmental Design (LEED) Governments, groups, and individuals work to promote sustainable ecosystems.
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(b)
(a)
Figure 3.24 (a) The École secondaire jeunes sans frontières building in Brampton is a LEED-certified building. It has a green roof, energyefficient windows, and water-efficient plumbing, and 91 percent of the construction waste was recycled or reused on other projects. (b) LEED statistics on the building.
rating system. Libraries, schools, office buildings, and homes can be scored on how efficiently they reduce water consumption, reduce energy consumption, use renewable energy sources, reuse and restore existing buildings, incorporate daylight, and many other factors (Figure 3.24).
Businesses and Sustainability Take It Further The Canadian Federation of Municipalities has conducted a survey of ecological footprints of large municipalities across Canada. How does your city or a city near you compare with the rest of the country? Begin your research at ScienceSource.
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Many businesses are responding to consumers’ demands to improve their business practices by promoting sustainability and reducing their footprints (Figure 3.25). Many manufacturers of cleaning products are introducing “green” cleaning products that do not have phosphates and other substances that cause eutrophication or degrade ecosystems in other ways. Many manufacturers have their products certified by independent ecological certifying organizations, such as EcoLogo. Two Canadian businesses are taking sustainability seriously. Bullfrog Power is an Ontario company that sells environmentally friendly electricity produced from renewable sources such as wind turbines and low-impact hydroelectric projects. These sources produce no emissions and so do not contribute to climate change or acid rain. Bullfrog’s electricity costs slightly more than conventionally produced electricity, but many businesses, government agencies, and homeowners buy their power from Bullfrog. The company that produces Boomerang paints takes recycling seriously. It takes leftover paint from recycling centres, sorts the leftovers by colour, and blends similar shades into new paint shades. The leftover paint cans are melted down and
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(c)
Figure 3.25 (a) Clorox has introduced cleaners that use more environmentally friendly ingredients. (b) EcoLogo has been certifying products as environmentally friendly for over 20 years. (c) Boomerang paints are reused paint and recycled paint cans.
reshaped into new paint cans. The reclaimed paint is then sold in the recycled cans. By reusing paint and recycling cans, they reduce the amount of waste going to landfills and use no new resources to make the paint.
Individuals and Sustainability Table 3.3 lists actions individuals can take to use resources in a more sustainable way. You and your family may have already started to do many of these things. Table 3.3 Environmentally Sustainable Actions Action
Consequence
Reduce emissions.
• Riding your bike, taking public transit, and using fuel-efficient vehicles are all ways to reduce carbon emissions.
Save energy.
• Lowering the thermostat, unplugging small appliances, and installing compact fluorescent light bulbs all reduce the demand for electricity, which is often generated by burning fossil fuels. • Reducing electricity consumption indirectly reduces air pollution.
Eat food produced locally.
• Buying food from local farmers reduces pollution from the trucks used to transport the produce. Buying from local organic farmers reduces pollution from pesticides as well.
Plant wisely.
• Planting native plants reduces the chance of introducing an invasive species. • Planting drought-tolerant plants reduces water usage in summer.
Buy wisely.
• Buying only what you really need reduces waste and reduces pressure on ecosystems. • Think about the impact that using and disposing of the item will have on the environment. • Choose products that have the EcoLogo or that you know were made in an environmentally responsible way.
Get involved.
• Check out your school community. Does it have an environmental awareness group? Is a full recycling program in place? If so, check it out. If not, think about organizing one. • Invite your family and friends to do an ecological footprint assessment. • Check out local or national organizations promoting environmental sustainability.
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Learning Checkpoint 1. How does the Forest Stewardship Council help make it possible for consumers to make environmentally responsible decisions regarding the purchase of wood products? 2. What is meant by the acronym “NGO” with respect to community groups? 3. List four standards that any forestry practice must meet to receive Forest Stewardship Council certification. 4. What are three ways in which an urban forest can benefit a community? 5. What are three ecological benefits that result from using sustainable building construction methods? 6. Identify one environmentally sustainable action that an individual can do, and give one or two positive consequences of this action.
A22
STSE Science, Technology, Society, and the Environment
What’s for Dinner? For many Canadians, a typical dinner may contain food shipped from all over the world. As you walk through your local supermarket, have you considered how much of the food is actually “fresh”? For example, the tomatoes you see in the produce section were probably picked weeks ago in California and shipped thousands of kilometres by truck or airplane before arriving at your local grocery store.
1. Would you consider changing what you eat in order to eat more locally grown food? How difficult would it be? 2. If you did eat more locally grown food, what changes would you have to make to your diet during the winter? 3. If you did eat more locally grown food in the summertime, what changes would you have to make to your diet?
Figure 3.26 The produce section of the supermarket has items from many countries.
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A23 Quick Lab Calculating Your Ecological Footprint Purpose
Questions
To determine the size of your ecological footprint and determine if your lifestyle is sustainable
Materials & Equipment
3. How does your footprint compare to the average Canadian’s footprint? Give reasons for why yours is higher or lower than average. 4. How does your footprint compare to that of an average person living in China (1.4 ha/person)?
• computer with Internet access
5. Is the ecological footprint of China greater or less than the ecological footprint of Canada? Explain.
Procedure 1. Use the ecological footprint calculator your teacher provides to calculate your ecological footprint. 2. Record or print out the relevant information.
6. What factors cause the average Canadian footprint to be so much larger than those in the developing world (Nigeria: 1.2 ha/person; Brazil: 2.2 ha/person)? 7. List three things that you could do to reduce your ecological footprint.
A24 Quick Lab Environmental Organizations Purpose There are many environmental organizations in Ontario and Canada. What are some of these organizations doing to sustain ecosystems?
4. How does the organization promote sustainable use of ecosystems?
• computer with Internet access
Procedure 1. ScienceSource Use the Internet to research one of the following environmental organizations or another approved by your teacher: • Pollution Probe • Ducks Unlimited • Greenbelt of Ontario
Questions 3. What kinds of environmental problem(s) does the organization attempt to improve?
Materials & Equipment
• World Wildlife Fund
2. Find out what types of projects your organization is doing in Ontario or across Canada.
• Nature Conservancy of Canada
5. Do you think the organization’s projects are effective? In what ways do you think they could be more effective? 6. Write a short summary of your findings, and present it to the class.
• The Sierra Club of Canada • The Suzuki Foundation
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CHECK and REFLECT
Key Concept Review 1. How does the idea of an ecological footprint help an individual determine whether he or she is living in a sustainable fashion? 2. The ecological footprint of all of humanity has been calculated to be equivalent to 1.3 Earths. What does this mean? 3. How do Environmental Farm Plans help Ontario farmers?
13. An owner of a plant nursery finds aphids, a small insect pest, on some of her plants. She decides to introduce ladybugs to eat the aphids. (a) Name the strategy she is using to control the pest. (b) Explain the benefits of this strategy. 14. What is the meaning of the symbol shown below, and how might you make use of it?
4. What two technological developments contributed to the ability to ship food products very long distances? 5. What is organic farming? 6. How can shopping locally promote the conservation of farmland? 7. How do good soil conservation practices reduce soil erosion? 8. How do forests act like air conditioners to cool a region during hot spells? 9. List five ways that urban forests benefit urban ecosystems. 10. What percentage of Canada’s contribution to excess carbon in the atmosphere comes from office buildings and homes? 11. List three ways that individuals can help reduce emissions from transportation.
Connect Your Understanding 12. The Evergreen Brick Works project embodies the ideas of “restore, reduce, and renew.” Give one example of how each of these terms is put into action at the Brick Works.
Question 14
15. Eco-labels help consumers by demonstrating to them that the producer of a product has operated in a sustainable fashion. Meeting the certification standards can mean a lot of extra work for a producer. Yet many producers strongly support the use of eco-labels. Suggest four ways that eco-labels are a benefit to suppliers.
Reflection 16. Will the ideas encountered in this section affect the way you live? How? 17. If you were determined to make one personal lifestyle change that would have the greatest impact on improving sustainability in your community, what would it be? Explain. For more questions, go to ScienceSource.
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COOL IDEAS f r o m J AY I N G R A M
Panamanian Cowbird Puzzle Back in the 1960s, a biologist named Neil Griffith Smith, working in Panama, could not understand the behaviour of cowbirds (Figure 3.27). A cowbird is a nest parasite: a female lays an egg in another bird’s nest, and the host bird raises the foreign chick along with its own chicks. Usually, female cowbirds have to be stealthy or else the host bird will recognize the cowbird’s egg and remove it from the nest. But in Panama, cowbirds behaved in two different ways. Some cowbirds behaved normally: a female would hide until the host bird left the nest and then lay one or two eggs that looked almost exactly like the host bird’s eggs. Other cowbirds were strangely obvious. In this situation, a cowbird would sit next to a nest in plain view of the host bird. When the host bird flew off, the cowbird would sit on the nest and lay an obviously foreign-looking egg among the host bird’s eggs (Figure 3.28). But why did the mother bird not just get rid of that egg when she returned? Smith discovered that it was all about botflies and bees. Botflies lay their eggs on newly hatched chicks, and the larvae feed on the chicks. Chicks infested with botfly larvae died. But they did not die if a cowbird chick shared the nest with them. The cowbird chick would eat the botfly larvae, thus protecting the other chicks. Of course, there was a price for this service: the cowbird chick took Figure 3.27 The giant cowbird is native to Panama.
Jay Ingram is an experienced science journalist, author of The Daily Planet Book of Cool Ideas, and host of the Daily Planet on Discovery Channel Canada.
up most of the nest and ate most of the food. One or two deprived chicks would die as a result, but not all of them. In this situation, host adult birds tolerated the presence of a cowbird (Figure 3.29). However, if the nest was near a beehive, it was a different story. The bees kept the botflies away. With a smaller fly population, chicks were less likely to be infested with larvae. In this case, there was no advantage to having a cowbird chick in the nest. Female cowbirds had to be much stealthier or their eggs would be removed by the host bird.
Question 1. A cowbird has different strategies for laying eggs in a host’s nest. Explain what each strategy is and when a cowbird would use each one.
Figure 3.28 In this case, the cowbird’s egg looks very different from the host bird’s eggs.
Figure 3.29 Cowbirds often lay eggs in the nests of crested oropendolas.
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CHAPTER REVIEW
ACHIEVEMENT CHART CATEGORIES t Thinking and investigation k Knowledge and understanding c Communication
a Application
Key Concept Review
9. The amount of biologically productive land and water area on Earth is about 6 ha per person.
1. What is the risk level classification for a species that is at risk of becoming endangered if limiting factors are not reversed? k
(a) Currently, the average American uses about 10 ha per person. What does this mean about consumption by the average American compared to the availability of resources on Earth? k
2. (a) What is the difference between ex-situ and in-situ methods of conservation? k
(b) How do Canadians compare to Americans in terms of average consumption per person? k
(b) Which is considered a method of last resort? k 3. How can botanical gardens play a role in the conservation of some species? k 4. What is often the single most important factor determining the success or failure of the in-situ protection of a particular species? k 5. What law helps to protect the approximately 200 species at risk in Ontario? k
(c) Do Canadians, on average, live within Earth’s ability to supply resources for generations to come? k 10. What is the term that relates to taking care of our natural resources to ensure they are used in sustainable ways for future generations? k 11. The image below shows a typical farmers market that sells local produce. What are three ecological benefits from buying locally produced foods? k
6. What is the main ecological purpose of establishing provincial parks, national parks, wildlife reserves, and marine sanctuaries? k 7. What are “biodiversity hot spots”? How are conservation biologists working to protect them? k 8. What major Ontario industry is threatened by the Asian long-horned beetle, and what measures are being taken to limit the beetle’s spread? k
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Question 11
12. Name three different actions individuals can take that lead to sustainable use of resources, and explain how these actions help the environment. k
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Connect Your Understanding 13. Explain how the restoration of Lake Erie is an example of effective collective action. k 14. Suggest ways that governments could encourage sustainable building construction practices. a 15. The bird’s-foot violet shown below is endangered because of habitat loss due to farming. It often thrives in areas that have had a forest fire, but such fires are limited by humans. Suggest a method of protecting this plant other than banning farming or permitting wildfires. t
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19. The average Canadian’s ecological footprint is 8.9 ha of land. If this land area were multiplied by the total number of people in the world, would it be greater or less than the total area of the planet? t 20. Certification programs are effective ways to demonstrate sustainable use of resources. However, some certification programs have been criticized as being ineffective. What might make a certification program ineffective? a
Reflection 21. Given that humanity is consuming resources faster than Earth can produce them, how will you take action to create a sustainable future? Write a short paragraph outlining the action you will take. c
After Writing Reflect and Evaluate
Question 15
16. Sometimes, a forestry company will log an area and replant the entire area with a single tree species. Would this company be certified as using sustainable practices? Explain why or why not. a 17. Suppose you have been hired by a tree planting organization to promote tree planting by individuals. Create a brochure to educate homeowners about the benefits of planting trees on their land. c 18. Create a concept map that shows how government, group, and individual actions promote environmental sustainability. c
Share your summary of information about an environmental organization with a classmate who wrote about a different organization. Listen to a reading of your classmate’s article. What was the most important information you heard? What was nice to know but not entirely necessary? Reconsider your own summary with the same questions. Write a statement to express what you have learned about researching and taking notes.
Unit Task Link In the Unit Task, you will be designing a sustainable community with a small ecological footprint. Reflect on the examples of government, group, and individual actions to promote sustainability. How have groups and individuals worked together to take action to promote sustainable communities?
Governments, groups, and individuals work to promote sustainable ecosystems.
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UNIT
Summary
KEY CONCEPTS
1
CHAPTER SUMMARY
Ecosystems are complex, self-regulating systems of organisms and their abiotic environments.
• Abiotic and biotic characteristics • Photosynthesis and cellular respiration • Nutrient cycles and energy flows • Equilibrium and carrying capacity
• The biodiversity on Earth is found in the biosphere, which includes the lithosphere, atmosphere, and hydrosphere. All of these spheres interact. (1.1) • Energy in ecosystems comes from the Sun. It is transformed into chemical energy by plants. As energy travels along food chains, the amount of usable energy decreases. (1.2) • Matter is recycled in ecosystems. Plants use matter from the soil and air to make their tissues. Matter then passes along food chains, which are the biotic parts of ecosystems. (1.2) • Decomposers release the substances in organic matter back into the soil, and the substances are reused by plants. (1.2) • Abiotic and biotic factors affect the size of populations in ecosystems. (1.2) • A population’s carrying capacity is the maximum number of animals that the habitat can support over a long period. (1.3) • When a population is at carrying capacity, it is at equilibrium. The number of births equals the number of deaths, and the population is steady. (1.3)
2
Human activity affects the sustainability of ecosystems.
• Factors affecting biodiversity • Soil profile and soil types • Factors affecting water quality • Bioaccumulation and biomagnification
• Biodiversity includes species diversity, genetic diversity, and ecosystem diversity. (2.1) • Overexploitation, habitat destruction, pollution, invasive species, and climate change are factors that decrease biodiversity. (2.1) • Soil is made up of humus, rock particles, and living organisms. Soil can be clay, sandy or loam, and it can vary in acidity. (2.2) • Water’s quality is assessed by its oxygen levels and acidity as well as by the presence of heavy metals, nitrogen, phosphorus, and pesticides. Poor water quality affects organisms that depend on the water. (2.2)
3
Governments, groups, and individuals work together to promote sustainable ecosystems.
• Conserving biodiversity • Conservation strategies • Environmental stewardship and sustainable use
• Extinction means the loss of biodiversity. Ex-situ and in-situ conservation strategies work to protect at-risk species. (3.1) • Governments use legislation to enact programs to protect ecosystems. (3.1) • Ecological footprints are a way of representing our resource use. (3.2) • Environmental stewardship means using resources in a sustainable way. Groups and individuals are taking action to increase sustainable use. (3.2)
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VOCABULARY
KEY VISUALS
• • • • • • • • • • • • • • • • •
abiotic (p. 13) aquifer (p. 25) atmosphere (p. 19) biodiversity (p. 9) biome (p. 16) biosphere (p. 18) biotic (p. 13) boreal forest (p. 17) carnivores (p. 30) cellular respiration (p. 29) chlorophyll (p. 28) community (p. 14) components (p. 11) consumers (p. 30) decomposers (p. 30) denitrifying bacteria (p. 26) detritivores (p. 30)
• • • • • • • • • • • • • • • • •
ecology (p. 12) ecosystem (p. 13) elements (p. 24) environment (p. 8) freshwater (p. 17) grasslands (p. 17) habitat (p. 14) herbivores (p. 30) hydrosphere (p. 19) lithosphere (p. 19) marine (p. 17) niche (p. 14) nitrifying bacteria (p. 26) nitrogen fixation (p. 25) nutrient (p. 22) nutrient cycle (p. 24) omnivores (p. 30)
• • • • • • • •
• • • • •
acid rain (p. 70) acidity (p. 74) bedrock (p. 72) bioaccumulation (p. 79) biological oxygen demand (p. 77) biomagnification (p. 79) clay soil (p. 73) clearcutting (p. 62) climate (p. 60) climate change (p. 60) crop rotation (p. 75) dissolved oxygen (p. 77)
• • • • • •
eutrophication (p. 78) extinction (p. 54) genetic diversity (p. 54) global warming (p. 60) habitat change (p. 55) habitat fragmentation (p. 56) heavy metals (p. 79) invasive species (p. 59) loam soil (p. 73) native species (p. 55) non-point source pollution (p. 58)
• overexploitation (p. 56) • pesticides (p. 80) • point source pollution (p. 58) • pollution (p. 58) • sandy soil (p. 73) • soil (p. 72) • soil erosion (p. 74) • subsoil (p. 72) • sustainable use (p. 54) • topsoil (p. 72) • urban sprawl (p. 62)
• • • • • • •
• at risk (p. 94) • conservation biology (p. 94) • ecological footprint (p. 106) • endangered (p. 94)
• • • • •
• environmental steward (p. 107) • ex-situ conservation (p. 96) • extirpated (p. 94) • in-situ conservation (p. 96)
• • • • • • •
organic matter (p. 30) photosynthesis (p. 28) population (p. 14) primary consumers (p. 30) producers (p. 30) reservoir (p. 24) scavengers (p. 30) secondary consumers (p. 30) species (p. 14) stewardship (p. 8) sustainability (p. 9) system (p. 11) temperate coniferous forest (p. 17) tertiary consumers (p. 30) tundra (p. 17)
CO2 in atmosphere photosynthesis photosynthesis cellular respiration
burning of fossil fuels and wood
plants
primary consumers phytoplankton
carbon compounds in water
higher-level consumers
decomposers dead organisms
fossil fuels
Carbon cycle
magnification of chemical’s concentration
fish-eating birds
10 000 000
large fish
1 000 000
small fish
100 000
zooplankton
10 000
producers
1000
water
1
Biomagnification
• integrated pest management (p. 107) • organic farming (p. 108) • soil conservation (p. 108) • special concern (p. 94) • threatened (p. 94) Ecological footprint
UNIT A
Summary
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UNIT
Task
Building a Sustainable Community Getting Started Changing your light bulbs and being more conscientious about recycling are two simple ways to move towards a more sustainable lifestyle. Imagine if your entire community adopted such practices as a way of life. There are communities that do. They even have a name: eco-villages. Eco-villages are completely self-sufficient, sustainable communities designed to have a minimal footprint on surrounding ecosystems. Eco-villagers carefully control their fuel and food consumption. Eco-villagers try to live, work, and play in a small region to minimize commuting, which reduces energy consumption. Walking a short distance to work or school can be a lot more satisfying than spending hours a day in traffic.
Criteria for Success You will work effectively and co-operatively as part of a team designing a new eco-village. You will assume a specific role on the team, such as: • builder • food specialist • technologist • water manager • waste supervisor • restoration specialist You will research aspects of the eco-village relating to your area of research and collaborate with the other team members to design the village. For the area of expertise you select to research, you must: • outline the ways the current situation is unsustainable • outline specific changes that will increase the sustainable use of local ecosystem resources
What You Need to Know A green-roofed cabin in Findhorn, an eco-village in Scotland.
Most eco-villages share several key characteristics, including the following: • use of renewable energy sources
Your Goal The project has three parts. • First, you will investigate in what ways certain aspects of your local community may be ecologically unsustainable. • Then, you will research changes that can be made to make some of these aspects more sustainable. • Finally, you will use your research to design a completely sustainable community for your area.
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• agriculture that is closely related to natural local conditions • homes built using techniques and materials that have a minimal impact on the environment • homes that have the capacity to provide power, water, and sewage solutions without relying on a centralized system
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What You Need • computer with Internet access
Procedure 1. In your group, brainstorm aspects of your local community that are unsustainable. Organize your thoughts into the following categories: buildings, food, technology, water, waste, and restoration. Brainstorm possible problems with: • current building design and construction techniques • current food production and consumption patterns • energy demand at global, national, and local levels • local water sources and how much people use for such things as irrigation, washing, and food preparation • how well your community reduces, reuses, and recycles • local ecological issues such as habitat change or fragmentation or pollution
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2. Decide which expert role each person will assume. Use the results of the group brainstorming that relate to your field of expertise to start a graphic organizer. 3. ScienceSource On the Internet, find information related to the aspect of sustainable communities you are researching. Look for terms such as “eco-village,” “sustainable community,” and “permaculture” in your search. 4. As a group, decide on the best location for your eco-village. Keep in mind that your village must be as self-sufficient as possible. Your location should have ready access to building materials, water, places of employment, and schools. 5. Collaborate with your team to design an eco-village that incorporates some of each expert’s ideas. 6. Decide how to present your design ideas. Will you create a pamphlet, a PowerPoint presentation, a poster, a Web page, or use some other method? 7. Present your eco-village design.
Assessing Your Work 8. Do you think building a completely sustainable community is possible? Explain. 9. What were the advantages and disadvantages of having a group of experts create the eco-village design?
Beddington Zero Energy Development is an eco-village in London, England. Its homes use 10 percent of the energy needed to heat similar-sized conventional homes.
This eco-village vegetable garden makes use of existing materials.
UNIT A
Task
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UNIT
Review
ACHIEVEMENT CHART CATEGORIES k Knowledge and understanding t Thinking and investigation c Communication a Application
2
Human activity affects the sustainability of ecosystems.
7. Define the term “genetic diversity.”
Key Terms Review 1. Create a concept map that illustrates your understanding of the following terms and how they relate to sustainable ecosystems. • abiotic factors • atmosphere • biodiversity • biomagnification • biosphere • biotic factors • carrying capacity • cellular respiration
8. List five major factors that affect biodiversity. k c
• ecosystem • equilibrium • hydrosphere • limiting factors • lithosphere • photosynthesis • population • sustainability
12. What method can farmers use to restore nutrients in the soil of their fields? k
2. Describe an abiotic factor that could affect a population of squirrels. k k
4. Snapping turtles eat frogs, frogs eat grasshoppers, and grasshoppers eat grass. (a) Construct a food chain using the above organisms. c (b) Add a decomposer to your diagram.
k
11. What type of measurement can be used to determine the acidity of the soil? k
Ecosystems are complex, self-regulating systems of organisms and their abiotic environments.
3. How is a food chain related to a food web?
9. List the elements that make up soil.
10. Which type of soil would most gardeners prefer to have? Why? k
Key Concept Review
1
k
c
(c) Add a source of energy for the producers to your diagram. c
13. Do “dissolved oxygen” and “biological oxygen demand” describe the same phenomenon? If not, how are the two terms different? k 14. How are modern pesticides an improvement over earlier ones?
3
k
Governments, groups, and individuals work to promote sustainable ecosystems.
15. Place the following categories in order from the least serious to most serious: extirpated, special concern, extinct, endangered, threatened. k 16. How can soil erosion be reduced?
k
5. The nitrogen cycle relies on the actions of several distinct types of bacteria. List and describe the function of each. k
17. What is one measure the federal government takes to prevent invasive species from being accidentally introduced into Canada? k
6. Describe three types of symbiotic relationships, and give an example for each one. k
18. Name an international treaty that protects biodiversity in Canada and around the world. k
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Connect Your Understanding
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23. Examine the graph below.
19. Explain why it is more accurate to define the biosphere as a global ecosystem rather than a global community. t
Growth of a Mink Population 12
21. Bacteria are bad for your health and are responsible for many diseases that hurt humans, animals, and plants. All efforts should be taken to completely eradicate bacteria on the planet. (a) Evaluate the validity of this statement. Support your answer. t (b) If necessary, modify the statement to make it more accurate. c 22. Study the following energy pyramids. (a) Which pyramid best represents a sustainable ecosystem? a (b) Explain why each of the other two pyramids is unsustainable. a (c) Suppose data were collected from the ecosystem represented by B in 10 years’ time. Draw an energy pyramid that might describe energy flow in the ecosystem at that time. Explain why you drew it the way you did. c
secondary consumers primary consumers producers
A
Question 22
B
C
Population (thousands)
10
20. Hypothesize what would happen to an ecosystem that had all of its decomposers removed. t
8 6 4 2 0 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 Year
Question 23
(a) During which years is this population of minks growing the fastest? t (b) What is the carrying capacity of the population? t (c) What factors cause the population to level off rather than continue to increase? t (d) What may have contributed to the sudden increase in minks? a 24. Decide which factor each of the following scenarios describes. a (a) A new school is built near a forest. A section of trees is clear-cut, and a nearby creek is diverted away from the building area. (b) Emissions from industry and automobiles are entering the atmosphere and contributing to increasing temperatures around the planet. (c) Sea otters have the thickest fur of any animal. Humans prized their fur for making coats. Sea otters were hunted almost to extinction.
Unit A
Review
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UNIT
Review
(continued)
25. What activity does the photograph show? (a) What effects does the activity in the photograph have on a nearby aquatic ecosystem? a (b) What effects might the activity have on a boreal forest ecosystem? a
29. The black-footed ferret population is increasing as a result of captive breeding programs. The ferrets’ main habitat is grassland. Most of their habitat was turned into farmland. The ferrets’ primary source of food is prairie dogs, which live in large colonies. The ferrets also use abandoned prairie dog burrows for shelter. They are vulnerable to sylvatic plague, a disease that is transmitted by fleas on prairie dogs. Create an in-situ conservation strategy to increase the ferret population. a 30. (a) What changes would you recommend to your local lumber supplier to reduce its ecological footprint? c
Question 25
26. Many people assume that if water appears clear, then it is safe to drink. Are they correct? What indicators would you use to determine whether the water is actually safe? a 27. The pond in the photo is located in a farming area. Hypothesize what may have occurred in the pond. t
Question 27
28. Many pollutants enter an ecosystem in very small amounts. If the amounts are so small, how can they harm ecosystems? t 126
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(b) If, as a result of following your recommendations, the products cost more than similar products in other stores, would you buy the product from this store? Explain why or why not. a 31. Suppose your school board wants to renovate your school to improve the building’s LEED rating, and they have hired you as an ecological consultant. Create a report that outlines changes you think need to be implemented to increase your school’s LEED rating. a 32. A homeowner dislikes the dandelions and chickweed in his front yard. He wants a lush, grassy lawn that his children could play on and that his neighbours would admire. He decides to use pesticides to eliminate the weeds. Critique his decision to use pesticides. List the positive and negative consequences of using pesticides. If you decide that using pesticides is not the best course of action, propose alternative actions the homeowner could take. c
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Skills Practice 33. The diagram shows the set-up for an experiment. Water taken from a tank full of fish was added to all the test tubes. A small aquatic plant was placed in test tubes B and D. Carbon dioxide forms carbonic acid when it dissolves in water. Phenol red is a substance that turns yellow in the presence of carbonic acid. A few drops of phenol red were added to each test tube. The table shows the initial observations for the experiment. Test tubes A and B were placed in a dark, cool location. Test tubes C and D were placed in a sunny location.
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(a) What is the purpose of test tubes A and C? t (b) Using your knowledge of the carbon cycle, predict final water colour for each test tube. t (c) Explain your predictions for each test tube. t (d) The experiment is repeated, but each test tube is filled with cold tap water instead of water from a tank full of fish. Predict the initial and final colour of the water in each test tube. t 34. A pitcher plant is a carnivorous plant that traps insects such as crickets. The insects die inside the plant and decompose. The plant absorbs the nutrients from their decomposing bodies that the soil does not contain. The pitcher plants are consumed by herbivorous mammals. Draw a food chain that represents this scenario. c 35. In a particular ecosystem, it has been determined that the secondary consumers use 5200 kJ/m2 of energy.
A
B
C
(a) How much energy was stored in the producers in that same food chain? t
D
Question 33
(b) How much energy would be used by the tertiary consumers? t
Experimental Observations Water Colour Test Tube
Initial
A
yellow
B
yellow
C
yellow
D
yellow
Final
36. (a) Create a graph that shows the population growth of an invasive species that has been recently introduced to a new area. c (b) Why did you draw the graph the way you did? Justify your answer. c
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(continued)
37. The following graph shows the population of a group of caribou on an island. How would you explain the changes in population? t Caribou Population 1945–70 5000 Population
Fish Catches 1990–2000 Year
6000
4000 3000 2000 1000 0 1945 1950 1955 1960 1965 Year
Question 37
38. A population of wolves was also introduced to the same island that had the caribou in question 37. The following table contains wolf population data. Use the graph and data from the table to develop a hypothesis that explains the fluctuations in the deer population and the island’s carrying capacity. t
Total Groundfish Landed
Total Aquacultured Salmon Harvested
1990
791 246
49 594
1992
630 574
46 931
1994
452 896
57 147
1996
374 086
72 572
1998
287 498
91 499
2000
229 637
127 336
(a) Graph both sets of data. Analyze the trend of the groundfish that have been caught. t (b) Predict how many groundfish will be caught in 2002 and 2004. t (c) Propose an explanation for the decreasing groundfish catch in Canadian waters. t (d) Based on the graph of total salmon harvested through aquaculture, will the fish needs of Canadian diets be met? t (e) Add the extra data in the table below to your graph. t
Wolf Population 1950–1970 Year
40. The Department of Fisheries and Oceans collects data on fish catches as shown in the following table.
Wolf Population
1950
100
1955
90
1960
50
1965
20
1970
0
39. Create a graphic organizer that shows different types of pollutants and how they affect terrestrial and aquatic ecosystems. c
Fish Catches 2002, 2004 Year
Total Groundfish Landed
Total Aquacultured Salmon Harvested
2002
255 994
171 035
2004
306 693
141 580
(f) How does this additional information change your prediction on how many fish will be available in 2006? t (g) Why is it important to have long-term data when working with ecological data? a
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Revisit the Big Ideas and Fundamental Concepts 41. The term “ecosystem” is short for ecological system. Ecosystems are complex, self-regulating systems of organisms and their abiotic environments. (a) What is ecology?
k
(b) What is a system?
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worked to promote sustainable ecosystems in Ontario. a 47. What kinds of actions are available to individuals in Canada to help make us more ecologically sustainable? a
STSE k
(c) Using the example of an aquatic ecosystem that has algae, a fish that eats algae, a trout that eats algae eaters, and eagles that eat trout, explain how matter cycles and energy flows through the ecosystem. k (d) Suppose the population of algae eaters suddenly increased due to an increase in algae. How might the ecosystem self-regulate to restore the algae-eater population? k 42. Explain how sustainability and biodiversity are interrelated. a 43. What are the five main factors that increase loss of biodiversity on Earth? k 44. What are soils, and what are the most devastating effects of human activities on soils? k 45. Suppose you were given the task of assessing the water quality of a lake ecosystem, and you could have measurements of the water done by sending water samples to labs for analysis. What are some types of tests you would order to be done on the water? a 46. Governments are able to take certain kinds of actions that other groups cannot. For example, they can make treaties with other countries and also pass laws. Explain how making treaties and passing laws have
Science, Technology, Society, and the Environment
48. The polluting of Lake Erie is a dramatic example of how activities in your neighbourhood can affect other parts of the province or even the world. Compile a short report that outlines how one or more personal activities could have a negative impact on distant ecosystems. Then, propose solutions to lessen these impacts on ecosystems. a 49. Governments, groups, and individuals are working to promote sustainability of ecosystems. Choose one of these that you have learned about, and explain what environmental issues they have tackled and their solutions to the problem. Elaborate on what you have learned, and suggest additional actions that they could take. a
Reflection 50. Suppose you were to throw a sustainability party for your friends, family, and neighbours to make them aware of the various factors that affect the sustainability of ecosystems. What kinds of things do you think you could do to make them aware of the problems and the possible solutions to these problems? c 51. What is the most important thing you have learned in this unit about the sustainability of ecosystems? c
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Each of these octopuslike structures has a tiny metal head and “nanowire” arms made of silica. Silica is a common substance with useful characteristics. It is, for example, a major part of sand and glass. Silica nanowires, shown here magnified about 20 000 times, can be used in communications devices. 130
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Atoms, Elements, and Compounds
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Contents 4
Matter has physical and chemical properties. 4.1 Investigating Matter 4.2 Physical and Chemical Properties
5
DI
The periodic table organizes elements by patterns in properties and atomic structure. 5.1 Developing the Atomic Theory
DI
5.2 The Elements 5.3 The Periodic Table
6
Elements combine to form ionic compounds and molecular compounds. 6.1 How Compounds Form 6.2 Names and Formulas of Common Compounds 6.3 Balancing the Hazards and Benefits of Elements and Compounds DI
Unit Task Every substance has special properties that may make it useful or hazardous or both. In this unit, you will learn about the components that make up different substances and give them their unique properties. In your Unit Task, you will design and test a toothpaste and investigate the properties of the ingredients that you use.
Essential Question What properties make one substance different from another?
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Exploring
We use plastic bags to carry groceries, package food, and contain garbage. When plastic bags are not recycled, they often become litter.
Plastic World We would need to make many changes in our everyday lives if we did not have plastics.
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Count the number of plastic items that you can see around you. People use plastic pens, cutlery, and bags. We use plastic in shoes, computers, cellphones, furniture, and cars. We use plastic to make food containers and the refrigerators they are stored in. There are many reasons that plastics are so widely used. A plastic is a material that can be shaped when soft and then hardened. This characteristic is very useful. There are many different kinds of plastics. Some plastics are made into sturdy structures and can be used to replace or strengthen human body parts, such as a faulty heart valve. Other types are made into thin, flexible sheets, perfect for making bags. Many plastics do not break down easily. This characteristic is useful for making longlasting structures, such as outdoor furniture, or items we use every day, such as household appliances. Plastic containers and gloves are very useful for safely handling corrosive chemicals. Chemistry helps us explore these and other characteristics of substances.
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The Lifetime of the Plastic Bag Plastic bags often end up as litter instead of being recycled. In some countries, so many plastic bags litter streets that the plastic shopping bag is known as “the national flower” or “the national flag.” Plastic bags have clogged storm drains, causing floods. The bags can also kill marine animals that eat them. For these reasons, and to save resources, many communities around the world have restricted the use of plastic bags. A typical plastic shopping bag is made of polyethylene. Polyethylene is relatively inert, which means that it does not react easily with other chemicals. This makes polyethylene useful, but since it does not easily break down in the environment, care must be taken to reduce its use and to recycle or dispose of it responsibly. The Town of Leaf Rapids, Manitoba, once spent thousands of dollars each year to clean plastic bags out of the forest. Bags scattered by the wind would cling to trees and fences near the town garbage dump. The town wanted a solution, and so Leaf Rapids became the first community in Canada to ban disposable plastic shopping bags.
B1
Sea turtle eating a discarded plastic bag
STSE Science, Technology, Society, and the Environment
Do We Need Plastic Shopping Bags? When we are finished using a plastic bag, we are faced with its disposal. Recycling is one option, but this uses energy and resources, possibly more than making the plastic bag in the first place. Plastic bags and other polyethylene products often end up in landfill — or as litter — and may not break down for decades.
2. At 16 years old, Daniel Burd won the Canada-Wide Science Fair for discovering that a certain type of bacteria can degrade over 40 percent of the weight of plastic bags in less than 3 months. How could this discovery be applied to improve the environment?
1. Should disposable plastic shopping bags be made illegal? Make a table with the headings “Advantages” and “Disadvantages.” Give your table a title. Identify at least two advantages and disadvantages of this idea. Decide your position, and defend your stance in a class discussion.
3. Plastic bags are not only used for shopping. List three other common uses for plastic bags. Can plastic shopping bags be safely reused for these other purposes? Explain.
Exploring
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Matter has physical and chemical properties.
UNIT B
Atoms, Elements, and Compounds
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Skills You Will Use The same properties of water that cause it to form beads on the surface of a leaf allow water to form a column inside a plant's stem. The column of water stretches from the roots to the top of even the tallest trees.
In this chapter, you will: • investigate and identify the physical and chemical properties of substances • plan and conduct an inquiry into the properties of common substances • conduct tests to identify gases
Concepts You Will Learn In this chapter, you will: • assess the usefulness and hazards of polyethylene • use appropriate terms to describe elements and compounds • describe the physical and chemical properties of common elements and compounds
Why It Is Important Plastic, diamond, road salt, and table salt are different types of matter with their own special properties. Understanding the properties of matter helps us to work safely with different substances and to change them to make useful things.
Before Reading The Language of Chemistry Make a “Language of Chemistry” chart for the terms below. Your chart should have three columns: Key Term, Before Reading, and During Reading. Under Key Term, write each word on its own row in the chart. Record what you think each term means in the Before Reading column of the chart by either writing a statement or drawing a diagram. As you read the chapter, make notes for yourself in the During Reading column to clarify your ideas about each term.
Key Terms • adhesion • chemical change • chemical property • cohesion • combustibility • mechanical mixture • physical property • pure substance • solution
Matter has physical and chemical properties.
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Investigating Matter
Here is a summary of what you will learn in this section: • Matter has mass and occupies volume. • Matter is composed of particles. The arrangement and movement of the particles determines whether a substance is solid, liquid, or gas. • Matter can be classified as a pure substance or a mixture. • Mixtures can be further classified as mechanical mixtures, suspensions, and solutions.
Figure 4.1 Fireworks displays combine art and chemistry.
The Chemistry of Fireworks
Figure 4.2 Fireworks are lit with a
flame.
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On Canada Day, when darkness falls, the skies of towns and cities across the country come alive with colours and sounds. Flares of red, blue, green, and white are joined by cracks and bangs as fireworks displays mark Canada’s national day of celebration (Figure 4.1). Fireworks are an ancient technology, first invented in China over 2000 years ago. Today, fireworks can be seen around the world and creating them is an art form called pyrotechnics. Pyrotechnics is a branch of chemistry, the science concerned with understanding and changing matter. The spectacular sights, sounds, and smells of fireworks come from the fusion of science and art. The designers of fireworks know that some substances burn with brilliant colours when heated (Figure 4.2). Aluminum metal is used in the kitchen as cooking foil. However, when aluminum is heated by an explosion, the metal burns with a bright white flame. To use aluminum in fireworks, it is first made into a powder so that it will burn quickly and spread out easily. The types of fireworks that light up the night sky or leave a thick glowing trail of light often contain aluminum.
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Many substances change colour when heated. The green colours in fireworks usually come from heated copper substances, while the bright oranges are based on another substance called sodium, which is present in ordinary table salt. The crack and bang of fireworks are produced when certain substances heat up and rapidly expand. The rapid expansion makes the sound. The explosions are often so powerful that they can be felt as well as heard.
B2 Quick Lab Observing Changes in Matter When substances are mixed, they may change in state or they may change into different substances with different characteristics. Watch for changes in colour, volume, and state (solid, liquid, or gas) as you complete this activity.
Purpose To observe changes in matter
Materials & Equipment • medium graduated cylinder • small beaker • bromothymol blue indicator solution • water • resealable plastic bag • 2 scoopulas • sodium hydrogen carbonate powder (baking soda)
Procedure 1. Measure about 30 mL of bromothymol blue indicator solution into a small beaker. 2. Hold open a resealable plastic bag. Place one scoop of sodium hydrogen carbonate powder in one corner of the bag. Place one scoop of calcium chloride powder in the other corner of the bag. 3. Pour about 30 mL of bromothymol blue indicator solution into the bag. Squeeze out the air, and quickly seal the bag. 4. Mix the contents by squeezing the bag for about 20 seconds. Use your hands to detect any temperature changes. 5. Observe as many kinds of changes to the matter in the bag as you can. 6. Clean up your work area. Follow your teacher’s instructions to safely dispose of all materials used. Wash your hands thoroughly.
• calcium chloride powder
Questions 7. Describe what you observed when you: (a) added indicator solution to sodium hydrogen carbonate (b) added indicator solution to calcium chloride (c) mixed the indicator solution and both powders 8. Were there any changes to the substances in this activity? How do you know? What evidence did you observe?
Matter has physical and chemical properties.
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Matter Has Many Forms Matter is anything that has mass and volume. Mass is a measure of the quantity of matter in an object. For example, a brick has more mass than an equal-sized volume of Styrofoam®. Mass is often measured in kilograms (kg) or in grams (g). Volume is a measure of how big an object is or how much space a fluid takes up. For example, a volleyball is larger than a baseball. Volume is often measured in litres (L) or in millilitres (mL). All matter has some volume, even if that volume is very small. Matter can be solid, liquid, or gas or a combination of these states. For example, foam is a mixture of a liquid and a gas, or a solid and a gas. Bubbles in a foamy bubble bath are liquid films of soap with air trapped inside them. Styrofoam® is a solid plastic containing trapped air. Lightweight aluminum foam can be made by trapping gas inside melted aluminum and then letting the metal harden (Figure 4.3).
Figure 4.3
A piece of aluminum foam
Suggested Activity • B4 Quick Lab on page 146
Changes of State Solids, liquids, and gases are called states of matter. Specific terms are used to describe changes of state of a substance (Figure 4.4). A change from a solid to a liquid is melting. A change from a liquid to a gas is evaporation (also known as vaporization). A change from a gas to a liquid is condensation and from a liquid to a solid is freezing. A solid can also change directly into a gas through sublimation. The opposite change is deposition, in which a gas changes directly into a solid.
sublimation
solid
melting
liquid
freezing
condensation
deposition Figure 4.4 Changes in states of matter
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evaporation
gas
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The temperature at which a solid turns into a liquid is called the melting point. For example, the melting point of water is 0°C. The reverse process, freezing, occurs at the freezing point. The melting point and the freezing point are always the same temperature. Similarly, the temperature at which a liquid turns to a gas is called the boiling point. The boiling point is the same temperature as the condensing point, the temperature at which a gas changes into a liquid.
solid
strong force close together
The Particle Theory of Matter The particle theory of matter is a way to describe the structure of matter and its behaviour (Figure 4.5). Matter can be broken into smaller and smaller pieces. Is there a limit to how many times a piece of graphite from a pencil can be divided and still be graphite? The answer is yes. The smallest possible pieces of graphite are particles. The particle theory of matter explains how this works.
liquid
• All matter is composed of very tiny objects called particles. These particles are too small to be seen, even with a powerful light microscope. • All particles have spaces between them. The distances between the particles change for different states of matter. For example, particles in a liquid have more space between them than the particles in a solid of the same substance, but particles in a liquid have less space between them than particles in a gas.
weaker force farther apart
gas
• Particles present in matter are always in motion. They may be vibrating back and forth, as in a solid, or moving in all directions, as in a gas. In a liquid, particles stay close together but can slide past one another. • The particles in a substance attract each other. The amount of attraction is different for different kinds of particles. In iron, which is a very hard solid at room temperature, the particles strongly attract each other. In water, which is a liquid at room temperature, the particles of water can slide past each other because the attractions between them are not very strong.
very weak force very far apart
Figure 4.5 Particles are arranged differently in a solid, a liquid, or a gas.
For a given substance such as water, the state it is in is related to its temperature.
Matter has physical and chemical properties.
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Particles and Heat In ice, the particles of water vibrate in place but cannot move around. They attract each other strongly, forming a solid. As heat is added, the particles of water vibrate more quickly, which weakens the attraction between them, allowing them to slide past each other (Figure 4.6). This allows water to flow as a liquid. When enough heat is added, the particles of water break free from each other and separate, forming a gas.
(c)
(a)
(b)
Figure 4.6 (a) When enough heat is added to ice, (b) the particles of water begin to slide past each other. (c) Eventually, the particles spread apart, forming a gas.
During Reading Learning Checkpoint Examples Help Give a Word Meaning Authors use examples to help readers really see the meaning of a word in their minds. If you can picture the example, you can usually understand the concept or idea. Watch for examples as you read to help you understand new terms.
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1. What are two features that all forms of matter have? 2. Use the particle theory of matter to explain what makes a liquid different from a solid of the same substance. 3. Compare the amount of space between particles of a gas with that of a liquid of the same substance. 4. What is the effect of adding heat to the particles in a sample of matter? 5. What is the difference between the melting of water and the melting point of water?
Atoms, Elements, and Compounds
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Classifying Matter
Suggested Activity • B3 Inquiry Activity on page 144
All matter is made up of different types or combinations of particles. For example, gold and iron are both metals, but they have very different characteristics. Pure gold is yellow and is so soft that a fingernail can put a mark on it, whereas iron is silvercoloured and much too hard to scratch with a fingernail. These two metals have different characteristics because the particles that make up each are different. That is, all particles of gold are identical, and all particles of iron are identical, but particles of gold are different from particles of iron. Different types and combinations of particles give every type of matter particular characteristics, or properties. A property is a characteristic that describes a substance. Substances may be classified as pure substances or mixtures, depending on how their particles are arranged.
Pure Substances A pure substance is made up of only one kind of matter and has a unique set of properties, such as colour, hardness, boiling point, and melting point. A pure substance is either an element or a compound. For example, gold is an element and sugar is a compound (Figures 4.7 and 4.8). • An element is a substance that cannot be broken down into any simpler substance by chemical means. Later in this unit, you will learn how elements are organized into a periodic table according to their properties. Each element has its own name and symbol. For example, hydrogen’s symbol is H. • A compound is a pure substance that is made from two or more elements that are combined together chemically. For example, water (H2O) is a compound containing the elements hydrogen and oxygen.
Figure 4.7 An ancient gold mask from Peru in South America. Gold is an element and a pure substance.
Figure 4.8 Sugar is a compound and a pure substance. All sugar particles are like all other sugar particles. It is a compound because sugar particles are made of more than one element.
Matter has physical and chemical properties.
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Mixtures A mixture is a combination of pure substances. However, the substances in a mixture do not combine chemically as happens when a compound forms. Each substance remains in its original, pure form, although each is not always easy to see distinctly once the mixture is made. There are three main types of mixtures. Figure 4.9 A chocolate chip cookie is a mechanical mixture. Different parts of the mixture are visible.
• In a mechanical mixture, the different substances that make up the mixture are visible (Figure 4.9). Soil is an example of a mechanical mixture. So is a mixture of salt and pepper. A mixture in which the different parts are visible is called heterogeneous. The prefix “hetero-” means different. • A suspension is a cloudy mixture in which tiny particles of one substance are held within another (Figure 4.10). Tomato juice is an example of a suspension. These particles can be separated out when the mixture is poured through filter paper. A suspension is also a heterogeneous mixture. • In a solution, the different substances that make it up are not individually visible (Figure 4.11). One substance is dissolved in another, creating a homogeneous mixture. The prefix “homo-” means same, and all parts of a homogeneous mixture look the same. Examples of solutions are sugar dissolved in hot coffee, and acetic acid dissolved in water to make vinegar.
Figure 4.10 A salad vinaigrette is a mixture of oil, vinegar, and spices. When shaken, they form a suspension. After a while, the components will separate. This is why salad dressings are usually shaken before using.
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Atoms, Elements, and Compounds
Figure 4.11 Tea is a solution of water and the extract of tea leaves that are dissolved in the water. A solution is homogeneous. Every part of the tea looks like every other part.
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A Summary of Matter Classification All matter can be classified as either a pure substance or a mixture. Mixtures are either heterogeneous or homogeneous. This is summarized in Figure 4.12.
matter
mixtures
homogeneous mixtures
heterogeneous mixtures
mechanical mixtures
pure substances
suspensions
compounds
elements
solutions
Figure 4.12 The classification of matter
Learning Checkpoint 1. How is a compound different from an element? Give an example of each.
Take It Further
2. What is the difference between a mixture and a pure substance?
Just like salt and other solid crystals, liquid crystals are pure substances with an ordered arrangement of matter. However, the fluidity of liquid crystals gives them some unusual properties. For example, some liquid crystals change colour with temperature changes. Find out about other properties of liquid crystals by visiting ScienceSource.
3. How is a suspension different from a solution? 4. Classify each of the following as either a pure substance or a mixture. (a) Pop is composed of water, sugar, and carbon dioxide. (b) Carbon dioxide is composed of carbon and oxygen chemically combined. (c) Sand is composed of white grains and black grains. (d) The graphite at the centre of a pencil is composed of carbon.
Matter has physical and chemical properties.
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DI Key Activity
SKILLS YOU WILL USE
B3
Inquiry Activity
Skills Reference 1
Conducting inquiries safely Processing and synthesizing data
Identifying Gases Changes to matter can result in the formation of gases. There are many different kinds of gas, and we can use their properties to help identify them. Three common gases are hydrogen, oxygen, and carbon dioxide. • Oxygen gas will cause a glowing splint to
reignite (catch fire).
Purpose To use gas tests to identify oxygen gas, carbon dioxide gas, and hydrogen gas
Procedure Part 1 — Preparation of Oxygen
• Carbon dioxide gas will put out a flame.
1. Using a medicine dropper, add 1 mL (about 20 drops) of hydrogen peroxide solution to a clean test tube.
• Hydrogen gas will make a “pop” sound in the presence of a flaming splint.
2. Add two drops of dish soap. 3. Using a scoopula, add a small amount (less than the size of a pea) of potassium iodide powder to the test tube.
Materials & Equipment
4. Use matches to light a wooden splint.
• 3 medicine droppers
5. Blow out the flame to make a glowing splint. Insert the glowing splint into the mouth of the test tube. Observe and record what happens to the splint.
• 3 medium test tubes • test-tube rack • 3% hydrogen peroxide solution • dish soap • scoopula • potassium iodide powder • matches • wooden splints • 0.1 M acetic acid solution • sodium hydrogen carbonate powder • 2 M hydrochloric acid solution • forceps • mossy zinc chunks • 1 large test tube
Figure 4.13 A glowing splint will reignite in the presence
of oxygen.
• test-tube holder
6. Clean up as directed by your teacher. CAUTION: Hydrogen peroxide may sting your skin. Potassium iodide will stain skin and clothing. Keep your hair tied back when working near open flames.
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Part 2 — Preparation of Carbon Dioxide 7. Using a medicine dropper, add 1 mL (about 20 drops) of acetic acid to the second clean test tube.
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(continued)
8. Using a clean scoopula, add a small amount (less than the size of a pea) of sodium hydrogen carbonate powder to the test tube.
14. Keep holding the large test tube upside down as you lift it off of the small test tube. Use matches to light a wooden splint.
9. Use matches to light a wooden splint.
15. Insert the flaming splint into the large test tube. Observe and record what happens to the splint.
10. Insert the flaming splint into the test tube. Observe and record what happens to the splint.
16. Clean up your work area. Follow your teacher’s instructions to safely dispose of all materials used. Wash your hands thoroughly.
Analyzing and Interpreting 17. Describe what happens in a positive test for oxygen gas. 18. Describe what happens in a positive test for carbon dioxide gas. 19. Describe what happens in a positive test for hydrogen gas. Figure 4.14 A flaming splint will be extinguished in the presence of carbon dioxide.
Skill Practice
11. Clean up as directed by your teacher.
20. Write a procedure for distinguishing between oxygen gas and carbon dioxide gas.
Part 3 — Preparation of Hydrogen
Forming Conclusions
12. Using a medicine dropper, add about 2 mL of hydrochloric acid to the third clean test tube.
21. Explain why the three parts of this activity can be used to distinguish among oxygen, hydrogen, and carbon dioxide gas but not to determine whether an unknown gas is one of these three.
13. Use forceps to add a small piece of mossy zinc to the third test tube. Use a test tube holder to place a large test tube upside down and over the smaller test tube in order to trap any gas.
Figure 4.15 Trapping hydrogen gas
Matter has physical and chemical properties.
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B4 Quick Lab Foam in a Cup You can manipulate matter to change its properties. In this activity, you will mix together different liquids and a solid to produce a completely different substance: a foam.
5. Position the tip of the medicine dropper at the very bottom of the first beaker, then squeeze the bulb in order to release all the vinegar. Record your observations.
Purpose To produce a foam and observe its characteristics
Materials & Equipment • corn syrup • two 250-mL beakers • 2 colours of food colouring • stirring rod • teaspoon • sodium hydrogen carbonate powder Figure 4.16 Adding coloured vinegar to the first beaker
• water • 50-mL graduated cylinder • vegetable oil • white vinegar • medicine dropper
Questions
Procedure 1. Pour about 30 mL of corn syrup into a beaker. Stir in three drops of one food colouring. Use a teaspoon to sprinkle a heaping spoonful (about 20 g) of sodium hydrogen carbonate powder on the corn syrup. 2. Pour 30 mL of water into the graduated cylinder. Tip the beaker slightly, and carefully pour the water in down one side. Add 30 mL of vegetable oil to the beaker in the same way. 3. Into a separate beaker, pour 20 mL of vinegar. Add three drops of the other food colouring. 4. Fill the medicine dropper with coloured vinegar from the second beaker.
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6. Clean up your work area. Follow your teacher’s instructions to safely dispose of all materials used. Wash your hands thoroughly.
Atoms, Elements, and Compounds
7. Write a statement to describe your observations in step 4. 8. Write a statement to describe your observations in step 5. 9. What types of changes did you observe? 10. Describe a characteristic of foam that you observed. 11. Describe the state or states of matter of the foam produced in step 5.
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CHECK and REFLECT
Key Concept Review 1. Water can exist as ice, liquid water, or gas. In each of the following processes, is heat added or removed in order to change the state of water?
9. Identify each of the following as a heterogeneous mixture, a homogeneous mixture, or a pure substance. (a)
(a) evaporation (b) condensation (c) freezing (d) melting
(b)
2. According to the particle theory of matter, gases contain particles that are far apart. Do the particles in a solid have spaces between them? Are the particles moving? Explain. 3. How could you speed up the particles that make up the silver in a table fork? How could you slow down the particles? 4. How is a mechanical mixture different from a solution? 5. The melting point of aluminum metal is 660°C. Is its freezing point slightly less than, equal to, or slightly more than 660°C?
Connect Your Understanding 6. Tin is a metal with a melting point of 232°C and a boiling point of 2602°C. What is its state of matter at each of the following temperatures? (a) 0°C (b) 1000°C (c) 2000°C (d) 4000°C 7. For each of the four statements in the particle theory of matter, choose one word that best sums up that statement’s meaning. Explain your four word choices. 8. Is a compound, such as water, a pure substance or a mixture? Explain.
Question 9
10. If you put olive oil in the fridge, the oil becomes solid. Explain what has happened using the particle theory of matter. 11. Can a sample of matter exist in two states at one time? Use an example to explain your answer. 12. Do all substances have the same melting point and boiling point as water? How do you know?
Reflection 13. The particles in matter are too small to see either with the unaided eye or with a strong light microscope. Does this fact have any influence on whether you accept the statements in particle theory or not? Explain why or why not. 14. What are three things about forms of matter that you learned about in this section? For more questions, go to ScienceSource. Matter has physical and chemical properties.
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Physical and Chemical Properties
Here is a summary of what you will learn in this section: • Physical properties describe the characteristics of a substance that can be observed or measured. • Chemical properties describe the reactivity of a substance and ways in which it forms new substances. • Physical properties include hardness, conductivity, colour, density, melting point, solubility, and viscosity. • Chemical properties include combustibility and reaction with water or acid. Figure 4.17 A fire produces many changes in matter.
The Chemistry of a Campfire A fire can be fascinating to watch (Figure 4.17). Although all the flames look similar, each particular spark and flicker is unique — never to be repeated in exactly the same way. With investigation, however, some patterns become clear. Chemistry reveals that all forms of burning are variations on a theme. Every fire needs the same three components: fuel, oxygen gas, and heat. In a campfire, the fuel is wood, a complex natural material that is rich in carbon. Carbon reacts with oxygen in the air but only if the air can reach the carbon in the wood. This is why the first step in building a campfire is usually to split a log into tiny splinters, called kindling. By chopping a thick log into kindling, much more carbon in the wood is exposed to the air. Oxygen gas has easy access to the carbon at the surface of the wood and so can react with it. The components of a fire must be in just the right balance. When lighting a fire, extra oxygen is sometimes needed. This is why gentle blowing on the first embers of the fire can help. There is enough oxygen in the breath to provide the extra boost. It is important not to blow the heat of the first sparks away from the fuel, however, as this will blow out the fire. Because combustion releases heat, there is no need to keep relighting the flame. 148
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Changes in Properties
During Reading
Fires produce new substances. One of these is invisible carbon dioxide gas. It is formed when oxygen from the air and carbon in the wood chemically combine. Where does all the wood go while it is burning? Most of the solid matter in a wood log changes into a gas and simply blows away. What is left is ash. Ash is a mixture of carbon compounds that did not have a chance to burn before the fire went out and other substances that simply do not burn. If left to burn for long enough, a fire can become smothered in its own ashes.
Understanding Vocabulary Authors often provide additional information — called an “elaboration” — to help you understand a new term or word. As you find new terms or expressions, look not just for a definition but also for added information that clarifies the term.
B5 Quick Lab Observing a Physical Change Soda pop contains carbon dioxide. In the air, carbon dioxide exists as a gas. However, when carbon dioxide is dissolved in water, this is not the case. The particles of water and carbon dioxide are attracted to each other, so they intermix, forming a solution. Disrupting these attractions produces a change that you will observe. When a substance undergoes a physical change, such as melting, its appearance or state may change but its composition stays the same. For example, melted chocolate ice cream has the same composition as frozen chocolate ice cream. In contrast, a chemical change results in the formation of a new substance or substances.
Purpose To investigate a change in matter
Materials & Equipment • 2 glasses • soda pop • chewy mint candy CAUTION: Do not eat or drink anything in the lab, including the soda pop and candy.
Procedure 2 full with soda pop. 3 2. Into one glass, drop a piece of the mint candy. Observe what happens in both glasses, and record your observations. 1. Fill the two glasses about
Questions 3. Adding candy to the soda pop caused a mainly physical change that disrupted the attraction between particles of liquid. How did you recognize this physical change? 4. Can you tell whether the composition of the candy changed after it was added to the soda pop? Why or why not? 5. Consider the change that took place. Suggest one reason that you would describe it as a physical change. Suggest one reason that you might also describe it as a chemical change. 6. In the procedure, you were instructed to fill two glasses with soda pop in step 1 but to add candy to only one glass. What is the reason for this? 7. Suggest ways to modify the procedure to produce an interesting effect or display involving the change in properties. Check with your teacher before trying it out.
Matter has physical and chemical properties.
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Physical Properties of Water
Figure 4.18 Water sticks to itself, forming droplets (cohesion), and to the spider web (adhesion).
Figure 4.19 In winter, fish are protected from freezing temperatures by the ice at the surface of the water. People can use this same ice as a platform when fishing.
All life on Earth depends on water. Our bodies are about 70 percent water. Some plants are 95 percent water. A characteristic of water is that it sticks to itself, a property that is known as cohesion. Due to cohesion, water forms beads on non-absorbent surfaces, such as glass. Water also sticks to other substances, a property known as adhesion (Figure 4.18). Adhesion allows you to mop up water with a towel. A physical property describes a characteristic of a substance that can be observed or measured. One example of a physical property is the melting point of a substance. Water has many interesting physical properties that make it very useful to organisms. For example, adhesion and cohesion help move water up through the stems of plants, including tall trees. Its ability to be a liquid at room temperature is another. Most materials shrink when they freeze. Water does not. Due to special interactions between water particles during freezing, water actually expands. This makes ice less dense than liquid water. As a result, ice floats on water. Why is this important? In winter, the ice on a body of water shelters the fish below. Floating ice can also make a useful temporary roadway or platform for ice fishing (Figure 4.19). However, the same properties that make water useful can also cause problems. As ice forms, it widens cracks in roads. In addition, snow and ice on the roofs of houses can cause damage when it melts and refreezes. Not only is the ice heavy, it can block gutters and downspouts that are meant to keep water flowing off the roof and away from the sides of the building.
Observing Physical Properties
Figure 4.20 The pieces of beach glass show a variety of physical properties.
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Figure 4.20 shows a dull, red, clouded piece of beach glass. Three physical properties of the glass include its lustre (shiny or dull), its colour, and its transparency (how see-through it is). Other physical properties can be observed using special equipment. For example, you could measure the mass and the volume of the glass to determine its density. Table 4.1 lists a number of other physical properties.
Atoms, Elements, and Compounds
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Table 4.1 Physical Properties of Matter Property
Description
Examples
What It Looks Like
Colour and lustre
The light a substance reflects gives it colour and lustre (shine).
The names for some substances, such as gold, are also the names of colours. Gold has lustre; concrete is dull. Gold and silver coins
Conductivity
Density
Conductivity is the ability of a substance to conduct electricity or heat. A substance that conducts electricity or heat is called a conductor. A substance with little or no conductivity is an insulator.
Most metals are good conductors. Copper is a very good conductor of electricity and so is used to make electric wires. Styrofoam® and glass are insulators.
Density is the amount of mass in a given volume of a substance.
The density of pure water is 1 g/mL. The density of gold is 19 g/mL. Water is denser than oil, but gold is denser than water.
Electric circuit with wires to conduct electricity
Fluids and solids with different densities
Ductility
Any solid that can be stretched into a long wire is said to be ductile.
Copper is a common example of a ductile material.
Copper wire
Hardness
Malleability
Hardness is a substance’s ability to resist being scratched. Hardness is usually measured on the Mohs hardness scale from 1 to 10.
The mineral talc is the softest substance on the Mohs hardness scale (1). Emerald is quite hard (7.5). Diamond is the hardest (10).
A substance that can be pounded or rolled into sheets is said to be malleable.
Aluminum foil is an example of a malleable substance. Metals such as gold and tin are also malleable.
An emerald gemstone
Aluminum foil
Viscosity
Viscosity is the resistance of a fluid to flow.
Syrup has a high viscosity compared to water.
Pancake syrup
Matter has physical and chemical properties.
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Observing Chemical Properties
Suggested Activities • B7 Inquiry Activity on page 156 B8 Inquiry Activity on page 158 B9 Design a Lab on page 160
A chemical property describes the ability of a substance to change into a new substance or substances. Chemical properties include how a substance interacts with other substances, such as acids, or how it reacts to heat or light. A chemical change always results in the formation of a new substance or substances. For example, when zinc metal and hydrochloric acid are mixed, they undergo a chemical change that produces two new substances: hydrogen gas and a compound called zinc chloride. A chemical reaction is a process in which a chemical change occurs. Chemical properties can be observed only when a chemical change occurs. If you mix baking soda and vinegar, you will produce a chemical change that involves the formation of gas bubbles. In general, evidence of chemical change can include a great variety of changes, including colour, odour, temperature, the production of light, the formation of a new solid inside a liquid, or the production of a new gas (Figures 4.21 and 4.22). Table 4.2 lists various chemical properties.
Table 4.2 Examples of Chemical Properties Chemical Properties Absorbs heat during reaction Combustible Forms gas when heated Reacts with acid Reacts with water Emits heat during reaction Emits light during reaction Forms a precipitate (solid) in a solution
Figure 4.21 Fireflies contain a chemical called luciferin. When luciferin reacts with oxygen, light is emitted.
Figure 4.22 Chemical changes made this banana ripe — and then rotten.
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Heat and Chemical Change Applying heat to a substance can result in chemical changes. For example, when baking powder is heated, it undergoes a chemical change that results in the production of carbon dioxide gas. This is very useful in cooking. It is this chemical reaction of baking powder in some baked foods that produces the gas needed to lift the cake and make it light and fluffy (Figure 4.23). If you forget to add baking powder to a cake batter, the cake will be flat and dense. Heating causes many different kinds of substances to react. Burning is another example of this kind of chemical change. Paper is combustible and so will simply burst into flame when raised above a certain temperature. Combustibility is the ability of a substance to react quickly with oxygen to produce heat and light. When some substances are mixed, their reaction absorbs heat. A chemical cold pack, for example, depends on a reaction that absorbs heat (Figure 4.24). Typically, a chemical cold pack is filled with water but also has an inner bag or tube full of chemicals. The inner compartment keeps its contents separated from the water until it is time to use the cold pack. When the inner bag is popped open, the chemicals within mix with the water in the cold pack. The reaction removes heat from the surroundings, and so the pack feels cold to the touch.
Figure 4.23 When baking powder in a cake batter is heated, it produces a new substance: a gas.
water
chemicals that will react with water
Figure 4.24 A chemical cold pack has an inner compartment containing reactive chemicals and an outer compartment containing water.
Learning Checkpoint 1. What is a physical property? 2. List three physical properties of water. 3. What is a chemical property? 4. List three examples of chemical properties. 5. How does a physical change differ from a chemical change?
Matter has physical and chemical properties.
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Controlling Changes in Matter to Meet Human Needs In our everyday lives, there are many examples of how understanding and controlling changes in matter help us meet our basic needs. Consider the freeze-dried foods business. Freezedrying is a way to preserve foods so that they can be eaten months and sometimes years later. As well, freeze-drying makes foods easy to prepare: all you have to do is add hot water (Figure 4.25). In the freeze-drying process, the food is first frozen to convert the water content in the food to ice. The frozen food is then put in a pressure chamber, and the pressure is reduced until the ice sublimes (changes from a solid to a gas). The result is that about 98 percent of the water in the original food item is removed. This leaves a food that is about 10 percent its original mass and that, once packaged, does not need to be refrigerated. Freeze-drying is also used by biologists to study tissue samples and by restoration experts to rescue important documents that are water damaged. During hot, dry weather, hikers are often restricted from making campfires. However, a fire-free heating pouch has been developed. The freeze-dried food is placed in the heating pouch. The pouch contains the elements magnesium and iron, as well as salt, which is a compound. When water is added to these chemicals, the resulting chemical change releases enough heat to warm the freeze-dried contents.
Figure 4.25 Freeze-drying removes
the water from food, which preserves the food until it is time to eat. 154
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From Corn to Biodegradable Plastic Wrap
Take It Further Being able to change materials from one form to another allows Adding cornstarch to plastic is one way to make the plastic us to make products that are not only useful but which also biodegradable. Find out about support a sustainable environment. For example, chemicals made other “green” products by visiting from corn can be used to make juice bottles, remove paint or nail ScienceSource. polish, and fuel some cars. Corn is put through a chemical change called fermentation. Once this chemical process is complete, the new substances are recovered, purified, and made into solvents, biodegradable plastics, and automobile fuel. Solvents are substances that dissolve other substances. Solvents are useful for making inks and nail polish and for removing paint. Corn-based solvents are not as harmful to the environment as some other types of solvents (Figure 4.26). An advantage of corn-based biodegradable plastics is that they can be broken down by bacteria. However, making and using corn-based products also has its drawbacks. People sometimes cut down rainforests to make way for cornfields. Corn that would otherwise be used for food is sometimes diverted to make disposable products. Figure 4.26 The inks used here contain solvents made from corn.
B6
STSE Science, Technology, Society, and the Environment
Polyethylene Plastic Polyethylene plastic is flexible, heat resistant, and strong. Children play with polyethylene toys, athletes drink from polyethylene bottles, and police officers wear polyethylene vests. Unlike some other types of plastic, polyethylene is considered safe to use in food containers. What happens to polyethylene products when we no longer need them? If they cannot be reused, another option is to recycle them. Some types of polyethylene break down more easily when exposed to sunlight. These types of plastics are considered photodegradable. This process releases tiny pieces of polyethylene.
1. Make a list of items you used today that are made from polyethylene. Identify which items you could live without and which are necessities. 2. Describe two ways you could help decrease the amount of polyethylene that goes into landfills. 3. What are some possible benefits of using photodegradable polyethylene to make disposable food containers or shopping bags? What are some possible problems with this type of plastic?
Matter has physical and chemical properties.
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B7
Inquiry Activity
Skills References 1, 2, 6
Using Properties to Identify Pure Substances Question How can you identify a substance from its properties?
Observing and recording observations Using appropriate formats to communicate results
2. Read the labels of the six known white substances, and note any hazard symbols or cautions.
Part 1 — Appearance 3. Place the spot plate on a piece of paper. Label the top of the spot plate with the tests you will conduct.
Materials & Equipment • cornstarch
• grease pencil
• magnesium sulphate powder
• scoopulas
• sodium chloride powder
• medicine droppers
• sodium hydrogen carbonate powder • sodium nitrate powder
• magnifying lens • water
4. Label the left of the spot plate with the identity of two or more of the six known white substances. Using a clean scoopula each time, deposit a sample of each substance in a separate well in the first column of the spot plate.
• 0.5 M hydrochloric acid • 5% iodine solution
• sodium thiosulphate powder • spot plate
• unknown substances
• blank sheet of paper
CAUTION: Iodine will stain your skin and clothing.
Procedure 1. In your notebook, make an observation table like the one below.
Figure 4.27 Placing substances in the spot plate
Table 4.3 Pure Substances Observation Table Substance
Appearance
Cornstarch Magnesium sulphate Sodium chloride Sodium hydrogen carbonate Sodium nitrate Sodium thiosulphate Unknown # ___
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Crystal Shape
Water
Acid
Iodine
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(continued)
5. Closely observe each white substance. In your table, record as many observations as you can about the appearance of each substance.
Part 2 — Shape 6. Use the magnifying lens to observe the crystal shape of each white substance. Record the crystal shape of each substance as “regular” or “irregular.”
Part 3 — Water 7. Use a clean scoopula to place a bit of the first substance into three more wells in the same row. Do the same for the second substance. 8. Using a medicine dropper, add a few drops of water to the second well of the second and third rows. Record your observations.
Part 4 — Acid 9. Using a clean medicine dropper, add a few drops of hydrochloric acid to the third well of the second and third rows. Record your observations.
Part 5 — Iodine 10. Using a clean medicine dropper, add a few drops of iodine to the fourth well of the first and second rows. Record your observations. 11. Clean out the spot plate as directed by your teacher. 12. Repeat steps 3–11 for the remaining white substances.
Part 6 — Unknown Substance 13. Repeat steps 3–11 for an unknown substance provided by your teacher. Be sure to record the unknown substance number in the table. 14. Clean up your work area. Follow your teacher’s instructions to safely dispose of all materials used. Wash your hands thoroughly.
Analyzing and Interpreting 15. For each white substance, there is one unique property that distinguishes it from the others. Identify this property for each white substance. 16. Which results from this inquiry were not what you expected? Explain. 17. How can the properties of the six white substances be used to identify the unknown substance? 18. What is the identity of the unknown substance? Explain how your observations support your conclusion.
Skill Practice 19. Identify the chemical and physical properties you observed in this activity.
Forming Conclusions 20. Write concluding statements to describe the chemical and physical properties of each substance that you examined.
Matter has physical and chemical properties.
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B8
Inquiry Activity
Skills References 1, 2
■ ■
Observing and recording observations Justifying conclusions
Investigating Physical and Chemical Changes You can use a chemical reaction to change one substance into another substance that has different physical and chemical properties. You can also use heat to change the properties of substances.
Question What are some characteristics of physical changes and chemical changes?
Materials & Equipment • scoopulas
• 3 test tubes
• sodium carbonate powder
• 0.5 M solution of sodium carbonate
• 250-mL beaker • medicine dropper • 0.5 M hydrochloric acid
• 0.5 M solution of copper(II) sulphate
Test 1 — Sodium carbonate and hydrochloric acid 2. Using a scoopula, add a small amount (the size of a pea) of sodium carbonate powder to the beaker. In your observation table, describe the appearance of the sodium carbonate powder. 3. Using a clean medicine dropper, obtain a few drops of hydrochloric acid. Observe the hydrochloric acid, and record what you see in your observation table. 4. Write a statement about the kinds of evidence for physical or chemical change that you will look for when you add the hydrochloric acid to the sodium carbonate. 5. Add five to eight drops of hydrochloric acid to the sodium carbonate. Record your observations.
Test 2 — Sugar and heat • aluminum muffin tin • white table sugar • candle
• two 5-mL measuring spoons • test-tube rack
• candle holder
• copper(II) sulphate (solid)
• matches
• water
• tongs or wooden clothespin
• stirring rod
6. Obtain an aluminum muffin tin. Use a clean scoopula to put a small amount of sugar (the size of a pea) in the centre of the aluminum muffin tin. Record your observations of the sugar. 7. Suggest possible ways that the sugar might change with heating. 8. Place the candle securely in a candle holder, then light the candle.
CAUTION: Copper(II) sulphate is poisonous and can stain your clothes and skin. Keep your hair tied back when working near open flames.
Procedure 1. Copy the following observation table into your notebook. Be sure to leave a row for each test.
9. Using tongs or a wooden clothespin, hold the aluminum muffin tin over the candle’s flame. Slowly move the muffin tin back and forth over the flame to heat the sugar. Record your observations. 10. Place the aluminum muffin tin in a safe place to cool.
Table 4.4 Observations of Physical and Chemical Changes Observations Test
Before Change
Sodium carbonate and hydrochloric acid
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During Change
After Change
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(continued)
Test 3 — Copper(II) sulphate and sodium carbonate 11. Using a measuring spoon, add 5 mL of copper(II) sulphate solution to a clean test tube. Using a different measuring spoon, add 5 mL of sodium carbonate solution to another test tube. In your observation table, describe the appearance of each solution.
Analyzing and Interpreting 19. Which of the changes that you observed were physical? How do you know? 20. Which of the changes that you observed were chemical? How do you know?
Skill Practice 21. Identify two properties for each of the following.
12. Write a suggestion about what you think will happen when the solutions are combined.
(a) sodium carbonate (b) white table sugar
13. Combine the solutions, and record your observations. 14. Dispose of the solutions as directed by your teacher.
Test 4 — Copper(II) sulphate and water
(c) copper(II) sulphate
Forming Conclusions 22. Create a flowchart that a classmate could follow in order to identify physical and chemical changes.
15. Using a scoopula, add a small amount (the size of a pea) of solid copper(II) sulphate to a clean test tube. In your observation table, describe the appearance of the substance. 16. Write a suggestion about what you think will happen when you add water to the copper(II) sulphate. 2 17. Fill the test tube full of water and record your 3 observations. Use a stirring rod to mix the water and copper(II) sulphate, and record any additional observations. 18. Clean up your work area. Follow your teacher’s instructions to safely dispose of all materials used. Wash your hands thoroughly.
Figure 4.28 Adding water to copper(II) sulphate
Matter has physical and chemical properties.
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B9 Design a Lab
Skills References 1, 2
Properties of Common Substances Elements, compounds, and mixtures are part of everyday life. From the kitchen to the chemistry lab, we make use of different substances for their different properties.
Question How can you use chemical and physical properties to distinguish among common substances?
Figure 4.29 Common substances
Selecting instruments and materials Observing and recording observations
Design and Conduct Your Investigation 1. Choose at least three substances to investigate. They may be substances from your chemistry lab or from home. 2. Decide which properties you will investigate. Select some from the list below, or add others. •
colour and lustre
•
combustibility
•
conductivity
•
density
•
hardness
•
melting point
•
solubility
•
texture
•
reaction with acid
•
reaction with water
3. Have your teacher approve your list of test substances and the properties you wish to investigate. 4. Plan your procedure. Think about these questions: (a) How will you observe different properties, and what materials and equipment will you need to make these observations? (b) How will you record your results? (c) How will you organize and present your results?
Figure 4.30 Possible materials and equipment
5. Write up your procedure. Show it to your teacher for approval before carrying it out. CAUTION: Keep your hair tied back when working near open flames. Take note of safety precautions for the substances you will be working with.
6. Carry out your procedure, and collect your observations. 7. Present your findings in a poster or in another form suggested by your teacher.
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CHECK and REFLECT
Knowledge 1. What does a physical property describe about a substance?
8. Identify each of the following as a statement that describes either a physical property or a physical change. (a) Ice melts.
2. For each of the following substances, list four physical properties. (a) water (b) iron metal (c) baking soda (sodium hydrogen carbonate) 3. What does a chemical property describe about a substance? 4. Identify each of the following observations as evidence of either a physical change or a chemical change. (a) A piece of copper is heated until it melts. (b) A piece of aluminum corrodes in a solution of acid. (c) A piece of paper burns in a candle flame. (d) A piece of plastic is stretched until it breaks. (e) Table salt boils at 1465°C. 5. From the following list, indicate which items would make good conductors.
(b) Hydrogen is a colourless gas. (c) You chop a carrot. (d) A diamond jewel is hard. (e) Copper wire bends easily. (f) The ruby slippers are red. 9. Examine this photograph of the graduated cylinder. What properties of water allow it to form a meniscus (the curve in the water)? Question 9 10. Use diagrams and captions to explain what happens to the particles of matter in each of the following situations.
(a) Butter melts. (b) Water boils on a stove. (c) Water vapour in the air cools and forms raindrops. 11. Do water and vegetable oil have the same freezing point? How do you know for sure?
(a) copper (b) Styrofoam®
Reflection
(c) iron
12. Name an object that you use every day, such as earphones, a plastic mug, or your toothbrush. What would you like to find out about this object’s properties now that you have completed this section?
(d) woollen mitten 6. What is the difference between the properties of ductility and malleability?
Connect Your Understanding
For more questions, go to ScienceSource.
7. Would you rather mop up spilled milk with a paper towel or a plastic bag? Use the terms “adhesion” and “cohesion” to explain your choice. Matter has physical and chemical properties.
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Investigating
CAREERS
Great CANADIANS in Science
Figure 4.31 Dr. Lee Wilson wants his research to make a difference in the world.
For Dr. Lee Wilson, chemistry is not just a research subject — it is a source of solutions to problems that touch our lives. Dr. Wilson is an awardwinning professor of chemistry at the University of Saskatchewan, where he teaches and conducts research (Figure 4.31). He hopes his work will made a big difference in medical and environmental science. Dr. Wilson’s special interest is in nanostructured materials. Nanostructured materials are made from components too small to be seen even with a light microscope. These components, which are less than 0.0001 mm in size, are very useful for making membranes with tiny pores. Such membranes can be used as filters to purify water of toxic chemicals. The opaque white material looks very ordinary, despite its special properties. Dr. Wilson says that the material acts like a sponge. Instead of trapping water, however, the material traps small particles, such as contaminants. Personal experience has been a major motivating factor in Dr. Wilson’s work. While working in rural Alberta, his father became dangerously ill due to contaminated water and had to have surgery. Dr. Wilson would like to see his research used so that even remote communities can protect their water supplies.
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in Science Lee Wilson Dr. Wilson feels it is important to be a scientist with a conscience. Scientists should do work that benefits society as a whole, he says. He also says it is important to follow your passion. “When I have a passion for something, whether it be a problem to solve or an idea of interest, it is the passion that carries me through the hardship, despite how difficult the challenges in solving the problem or learning a new skill may be.” Dr. Wilson was the first in a small Metis community in Manitoba to go to university, the first in his family to complete a university degree, and the first Metis student to get a PhD from the University of Saskatchewan. Today he mentors young Aboriginal students participating in science fairs and camps and his own graduate students (Figure 4.32). His advice to young scientists is to get a good education, take lots of science courses, but also to take courses in the arts. Scientists need to be able to communicate, he says, not just do research in a lab.
Questions 1. How is Dr. Lee Wilson’s work being applied to improve the environment? 2. ScienceSource Use the Internet to research nanostructured materials. What are nanostructured materials, and how are they different from other substances?
Figure 4.32 Dr. Lee Wilson working with his students
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The Art of Chemistry
Lost Wax — Found Metals Figure 4.34 The final product
Figure 4.33 Foundry artisans working with hot liquid metal
Imagine sculpting a beautiful object or statue in clay and then transforming it into a single solid piece of metal. This is the job of a foundry artisan. A foundry artisan is a master of both the art and science of manipulating matter. A foundry is a place where metals such as gold and iron are fashioned into specialized parts. The metal is first melted until it becomes a liquid and then poured into a mould where it can harden and take on a new shape. An artisan adds creativity to the process, often making one-of-a-kind pieces of art. It may take an artist a week or a month to make a clay sculpture. When it is ready, the sculpture is brought to a foundry, where the work is completed. The clay sculpture is covered with silicone rubber to form a mould. The mould is a “negative” version of the clay sculpture. Hot wax is poured into the mould to coat the inside. This step is repeated until a “positive” version of the clay sculpture has been created. This looks just like the original clay sculpture. A second negative of the sculpture is made by coating the wax with a ceramic material, which is a solid that can withstand the heat of molten metal without
breaking. Melting away the wax creates an empty vessel into which molten metal can be poured. One major step remains before the cast metal piece of art is complete. A hot furnace is used to heat aluminum, silver, iron, or gold until it melts. The metal is then poured into the empty mould, where it takes on the shape of the original clay sculpture (Figure 4.33). After allowing the mould to cool slowly, it is removed and the metal piece is sanded and polished to add the finishing touches. The cast metal art is now ready for sale or shipping to the museum or person who commissioned it (Figure 4.34). The work of a foundry artisan takes a combination of skills and talents. Being able to visualize the finished product from the start is important. A foundry artisan is creative, pays attention to detail, and has the self-discipline to meet deadlines. Also, an artisan must know how to work safely in the foundry. Most artisans apprentice with an expert in order to learn the specific skills they need for foundry work. Many have been to art college or studied the arts in university. It is common for artisans to be self-employed, and so basic business training can be helpful.
Questions 1. The process of casting a piece of artwork in metal involves making several positive and negative versions of the final cast object. Sketch a flow chart that identifies these steps. 2. ScienceSource Research where you can take courses in jewellery casting or foundry art.
Matter has physical and chemical properties.
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CHAPTER REVIEW
ACHIEVEMENT CHART CATEGORIES t Thinking and investigation k Knowledge and understanding c Communication
a Application
Key Concept Review 1. What is the main difference between a pure substance and a mixture? Name an example of each. k 2. What is a chemical change?
k
3. In the following diagram, what change of state does each letter indicate? k
solid
(d)
(c)
liquid
9. For each example, identify whether the property described is chemical or physical. Justify your answer in each case. c (a) Bronze metal has a shiny lustre. (b) When silver nitrate is added to calcium chloride, a cloudy solid (precipitate) appears. (c) Mercury is liquid at room temperature.
Connect Your Understanding
(a)
(b)
8. What are two physical changes that cooling a hot substance may result in? k
gas
(e)
10. Identify the processes shown in the following photographs as chemical changes or physical changes. Justify your answers. t (a)
(f)
4. Low-density polyethylene is a plastic that can be stretched somewhat without breaking it. Why is this property useful for disposable shopping bags? k
(b)
5. Explain the difference between cohesion and adhesion, using an example. c 6. Explain why particles of water in the air can form frost on a cold window. k 7. Name a physical property that is:
k
(a) shared by gold, copper, and iron (b) shared by gold and copper but not iron (c) shared by diamond and glass
(c)
(d) not shared by diamond and glass
Question 10
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11. Why will water form droplets on a smooth surface, such as a countertop? a 12. Classify and compare the following mixtures. a (a) a drink made by dissolving drink crystals in water (b) a cup of tea with tea leaves in it (c) tomato juice 13. How can the application of heat result in a chemical change? Explain, using an example. a 14. Metal foams are 75 to 95 percent air. What effect does this have on the density of metal foam compared to solid metal? t 15. If water freezes inside of a building’s water pipes, the pipes may burst. Explain why this happens. a 16. Some types of clear plastic can be used to make lenses. List three important properties of plastic that make it suitable for use in eyeglass lenses. a 17. Winter car tires are made from a soft type of rubber that remains flexible, even in icy temperatures. Winter tires also have deeper grooves than all-season tires. Do you think people should be required by law to have winter tires for their vehicles? Why or why not? Support your response with a discussion of the properties of rubber tires. c 18. List five items you have used today. Try to identify one substance that each item is made from and the property or properties that make that substance useful. For example: cellphone — plastic — lightweight and hard
a
19. Maple syrup comes from the sap that flows in maple trees. The sap is collected and then boiled so that much of the water it contains
will evaporate. Boiling off the water increases the sugar concentration of the syrup and makes the syrup more viscous. Describe what is happening to the particles in the syrup at each stage in the process. c 20. Consider a homogeneous mixture, such as a salt solution, and a heterogeneous mixture, such as rice and pebbles. Suggest and compare how you could separate the substances within each type of mixture. a
Reflection 21. Describe something that you did not know before reading this chapter about how people change the properties of matter. c 22. How has your opinion of the use of chemicals in our society changed since completing this chapter? c
After Reading Reflect and Evaluate Review the “Language of Chemistry” chart you made at the beginning of the chapter. How did the strategies for finding word meanings help you to add definitions and explanations of new terms in the “During Reading” section of the chart? Compare your chart and use of strategies with a partner, and discuss how each strategy helped you to get a clear picture of new vocabulary.
Unit Task Link What steps should you take before investigating the properties of different substances? List some of the physical and chemical properties that you could investigate in the Unit Task, for which you will design a toothpaste. Make a list of safety precautions that you and your lab partners will need to follow.
Matter has physical and chemical properties.
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The periodic table organizes elements by patterns in properties and atomic structure.
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Home At night, signs created from tubes of neon gas light up the streets. One of the properties of the element neon is that it is a gas at room temperature. Another property of neon gas is that it glows when an electric current passes through it.
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Skills You Will Use In this chapter, you will: • conduct investigations into the physical and chemical properties of elements • assess social, environmental, and economic impacts of the use of elements, such as heavy metals
Concepts You Will Learn In this chapter, you will: • explain how experimental evidence has been used to develop models of the atom • describe characteristics of neutrons, protons, and electrons • describe physical and chemical properties of common elements • compare physical properties of elements within and between groups in the periodic table • explain the relationship between atomic structure and the arrangement of elements in the periodic table • describe patterns in the arrangements of electrons in atoms of different elements
Why It Is Important All of the substances that make up our world — and ourselves — are composed of elements or combinations of elements. Understanding the properties of elements helps us to obtain, produce, and use substances responsibly and effectively.
Before Reading Monitoring Understanding Good readers keep track of places where their understanding of new words or ideas breaks down, and they use strategies to fix up their understanding. Preview the Key Terms below and the subheadings for section 5.1. Make predictions about places where you may have difficulty understanding the ideas.
Key Terms • atom • electron • metal • metalloid • neutron • non-metals • nucleus • proton
The periodic table organizes elements by patterns in properties and atomic structure.
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Developing the Atomic Theory
Here is a summary of what you will learn in this section: • An element is a pure substance that cannot be broken down into other substances by chemical reactions. The smallest piece of any element having all of that element’s properties is one atom. • Different models of the atom have evolved over time as experiments have revealed new information. • Atoms are composed of subatomic particles: negatively charged electrons, positively charged protons, and neutrons, which have no electric charge.
Figure 5.1 Copper and iron are both metals and are both made of tiny particles. However, the particles in copper are different from the particles in iron.
Science, Art, and Atoms
Figure 5.2 Made of individual iron atoms on a base of copper atoms, this is an enlargement of one of the smallest pieces of art. The characters mean “atom” in Chinese.
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Recent advances in technology have made it possible to make images of individual particles and even to pick up the particles and move them around. Some artists who are also scientists have used individual particles to create the tiniest works of art in existence, such as the Chinese characters shown in Figure 5.2. This artwork is much too small to ever be seen with the unaided eye. About 100 000 copies laid end to end would be needed to cover the distance across the diameter of a human hair. Both Figures 5.1 and 5.2 show artwork made from two different metals — iron and copper. The Chinese characters in Figure 5.2 are made from particles of iron, and the background is made of copper particles. The individual particles of each element, called atoms, are visible as small bumps in the image. An atom is the smallest part of an element that has all of the element’s properties. Creative scientists and artists are finding new ways to put atoms together. Atoms of copper are not the same as atoms of iron. This is why a piece of copper metal has different properties than a piece of iron metal. Iron’s strength is useful to artists because it can be used to support heavy weights. Copper has an attractive colour and lustre, and its malleability makes it easy to work with.
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B10 Quick Lab Calcium Metal in Water Like copper and iron, the element calcium is a metal. However, calcium is easy to tell apart from metals like copper and iron.
Purpose To observe how calcium metal reacts with water
2. Dry your hands well. Your teacher will give you a few pieces of calcium metal on a paper towel. Use forceps to drop a piece of calcium metal into the water. Adjust the position of the test tube so that the mouth of the test tube covers the calcium metal. Observe what happens. 3. Light a wooden splint.
Materials & Equipment • 2 medium test tubes
• candle and matches or lighter
• 2 rubber stoppers
• wooden splints
• water
• test-tube clamp or tongs
• two 400-mL beakers
• pieces of calcium metal
• phenolphthalein indicator solution • paper towel
• medicine dropper
• forceps
4. Use clamps or tongs to lift the test tube out of the water without turning it upright. Place the flaming splint under the mouth of the test tube, and observe what happens. 5. Repeat step 1 with a clean beaker. Add five drops of phenolphthalein to the water in the beaker, and then repeat steps 2 through 4. 6. Clean up your work area. Follow your teacher’s instructions to safely dispose of all materials used. Wash your hands thoroughly.
Questions
CAUTION: Keep your hair tied back when working near open flames. Do not touch calcium metal with your bare hands as the metal will react with moisture in your skin.
7. Why is it important to keep the test tube upside down after removing it from over the piece of calcium metal? 8. The gas produced in this experiment was hydrogen gas. Briefly describe the procedure for testing for hydrogen gas.
Procedure 1. Fill a beaker with about 300 mL of water. Completely fill a test tube with water. Place a rubber stopper over the opening of the test tube, then place the test tube upside down in the beaker. Reach into the water, and remove the rubber stopper. Try not to let any air into the test tube.
9. How does the phenolphthalein indicator solution respond when calcium reacts with water?
The periodic table organizes elements by patterns in properties and atomic structure.
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Evolving Models of the Atom W O R D S M AT T E R
We get the modern term “atom” from the Greek atomos, meaning indivisible.
Different kinds of atoms give elements different properties. Atomic theory is the study of the nature of atoms and how they combine to form all types of matter. Atomic theory helps us to understand why there are different kinds of atoms. It explains how atoms combine to form over 100 known elements and all other forms of matter, including compounds and mixtures. The idea that most of the matter we encounter is made from combinations of simple forms of matter is very ancient. The philosophers of ancient Greece reasoned that the basic forms of matter, which they called elements, were fire, water, earth, and air. In ancient China, the elements were thought to be fire, water, wood, metal, and earth (Figure 5.3). Ancient civilizations used these and similar ideas as the basis for understanding the world and practising medicine. Today, we still use the term element, though in a different way. For example, we still believe that most substances are built up from simpler ones. About 440 B.C.E., the Greek philosopher Democritus hypothesized that breaking down rock into powder and then grinding the powder further would reduce it to tiny bits of matter that could not be broken down any more. His idea was not popular and, at the time, there was no experimental evidence to support it.
Figure 5.3 An ancient Chinese idea about matter is that it is formed from five elements that interact in particular ways. 170
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Atomic Theory Takes Shape Atomic theory is rooted in the idea that an understanding of atoms and their structure can help us predict many of the properties of matter. Modern atomic theory began to take shape in the early 1800s. It was then that John Dalton (1766–1844), a scientist and teacher in England, reconsidered the ancient idea that each different kind of element is composed of a different kind of atom (Figure 5.4). Dalton imagined that all atoms were like small spheres but that they could have different properties. They might vary in size, mass, or colour. Figure 5.5 shows how Dalton imagined atoms would look. Dalton used the following theory to explain the nature of matter:
Figure 5.4 Science teacher and researcher John Dalton
• All matter is made of small, indivisible particles called atoms. • All the atoms of an element are identical in properties such as size and mass.
Suggested STSE Activity • B11 Quick Lab on page 176
• Atoms of different elements have different properties. • Atoms of different elements can combine in specific ways to form new substances. Dalton also devised a series of element symbols to represent the atoms of different elements. These symbols are shown in his Table of Elements from 1808 (Figure 5.6). The small round symbols were meant to resemble atoms.
Figure 5.5 John Dalton suggested that atoms were like small spheres. Each element, he proposed, had a unique type of atom with a particular mass.
Figure 5.6 John Dalton devised a set of element symbols to improve communication between scientists.
The periodic table organizes elements by patterns in properties and atomic structure.
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During Reading Fixing Up Understanding Using Illustrations Make a note of the sentences or paragraphs that you do not understand. Look at the figures on that page and the pages before and after it. Reread each sentence or paragraph, and connect the words and ideas to the illustrations. How do the illustrations help you to understand the words?
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Atoms Are Composed of Smaller Particles J. J. Thomson (1856–1940), an English physicist, researched the idea that atoms might be made from a combination of particles. He experimented with electric currents in glass tubes called cathode ray tubes (Figure 5.7). Using the tubes, he was able to cause non-radioactive atoms to produce streams of negatively charged particles, later named electrons. Figure 5.8 shows how the cathode Figure 5.7 J.J. Thomson used a simple cathode ray ray tube worked. tube like this one.
electricity source
Figure 5.8 In a cathode ray tube, the heated metal at one end of the gas-filled tube sends out a stream of electrons.
Figure 5.9 Thomson’s model of the
atom.
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magnet
electrical condenser plates
Electrons are now understood to be negatively charged particles in atoms. Because all of the elements that Thomson tested in his cathode ray tube produced electrons, he reasoned that atoms of all elements must contain electrons. In 1897, Thomson proposed a revolutionary new model for atoms, in which each atom was composed of smaller particles. Because Thomson had detected negatively charged particles, he reasoned that atoms, which have no overall electric charge, must also contain positive charges. A diagram of Thomson’s model is shown in Figure 5.9. It depicts the atom as a positive sphere with negative electrons scattered throughout it.
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The Discovery of the Atomic Nucleus New Zealand-born scientist Ernest Rutherford (1891–1937) tested Thomson’s model of the atom while working in England. Rutherford conducted an experiment in which he shot positively charged particles at a very thin foil of pure gold. Rutherford obtained the stream of positive particles from a radioactive substance, which he placed in a lead block with a tiny hole. Out of the hole escaped a stream of these particles, which Rutherford directed at the gold foil. In the experiment, as shown in Figure 5.10, most of the highspeed positive particles went right through the foil. However, about 1 in 10 000 positive particles bounced back from the foil as if it had been deflected by something very massive and positively charged. Rutherford had discovered the nucleus, the centre of the atom. This tiny positively charged part of the atom also contains most of the atom’s mass. He calculated that the size of the nucleus compared to the rest of the atom was like the size of a single green pea compared to that of an entire football field!
high-speed particles
high-speed particles nucleus
gold foil (a) prediction
atom
gold foil (b) evidence
(c) new model
Figure 5.10 (a) Rutherford predicted that if nothing blocked the way of high-speed particles shot at a piece of gold foil, then all the particles would pass through the foil. (b) The data showed that something massive blocked a few of the particles. (c) Rutherford revised the atomic model to include the nucleus.
Based on his gold foil experiment, Rutherford revised the atomic model using his prediction that all atoms everywhere contain a nucleus (Figure 5.11). His model was like Thomson’s except that all of the atom’s positive charge and most of the atom’s mass were concentrated at a tiny point in the centre. The electrons surrounded the nucleus and occupied most of the atom’s volume, but they contained only a small fraction of the atom’s total mass. Inside the Nucleus James Chadwick (1891–1974), Rutherford’s student, refined the concept of the nucleus. Chadwick discovered that the nucleus contains neutral particles as well as positively charged particles. The neutral particles in the nucleus of the atom are called neutrons. The positively charged particles in the atom are called protons. Each neutron in an atom has about the same mass as each proton in the same atom, but the neutron carries no electrical charge.
Figure 5.11 Rutherford’s model depicted the atom as a tiny yet massive point of positive charge surrounded by electrons.
The periodic table organizes elements by patterns in properties and atomic structure.
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Electrons Exist in Energy Levels Danish physicist Niels Bohr (1885–1962) studied the properties of electrons in atoms and, along with other researchers, transformed Rutherford’s model into one of the models that are used today (Figure 5.12). A simplified version of this model that shows how electrons are arranged in the elements hydrogen and magnesium is given in Figure 5.13. Although some of the features shown here, such as the pairing up of electrons, were discovered after Bohr did his work, this kind of illustration has come to be known as a Bohr model, or Bohr diagram.
electron
Figure 5.12 Niels Bohr was only 28
when he proposed his theory of the atom. In 1922, he won the Nobel Prize in physics.
nucleus
electron
nucleus
electron shells
hydrogen atom magnesium atom
Figure 5.13 Bohr diagrams like the ones shown here for hydrogen and magnesium are often used to show the arrangement of electrons in atoms.
nucleus
cloud of electrons
Bohr suggested that electrons surround the nucleus in specific energy levels, called shells. He discovered that electrons jump between these shells by gaining or losing energy. Each shell can contain only a specific number of electrons. The maximum number of electrons that can exist in each of the first three shells is two, eight, and eight. Many people still use this model to describe the particles that make up the atom.
The Quantum Mechanical Model
Figure 5.14 The quantum mechanical model of an atom describes a cloud of electrons surrounding the nucleus.
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The most advanced and accurate model of the atom, and the one in use today by physicists and chemists, is called the quantum mechanical model (Figure 5.14). In this model, electrons do not exist as tiny points inside an atom. Electrons exist in specific energy levels, but they surround the positively charged nucleus in a form resembling a cloud.
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Learning Checkpoint
Take It Further Modern understanding of the properties of matter is built on the inquiries of many different people from around the world working over the ages. The alchemists, for example, were people who tried to use magic and chemical changes to turn various substances into gold. In 1597, the German alchemist Andreas Libau published Alchemia, a book describing the achievements of alchemists. In it, Libau explained how to prepare chemicals such as hydrochloric acid. Find out what else the alchemists discovered. Go to ScienceSource to start your search.
1. (a) What is similar about the ancient and modern definitions of “elements”? (b) What is different about the ancient and modern definitions of “elements”? 2. What evidence led J.J. Thomson to believe that atoms of all elements contain electrons? 3. On what information did J.J. Thomson base his hypothesis that atoms contain positive particles? 4. Describe the experiment that showed that the atom has a dense, positively charged nucleus. 5. Describe three ways in which protons are different from electrons. 6. What are three features of a Bohr diagram?
A Summary of the Atom All elements are composed of atoms, and one atom is the smallest unit of any element. Although there are more than 100 different elements, each with its own kind of atoms, the atoms themselves are made of different kinds of smaller particles, called subatomic particles. Three subatomic particles are protons, neutrons, and electrons, and they have different properties. One such property is relative mass. Relative mass compares the mass of an object to the mass of another object. An electron is the least massive subatomic particle of the three subatomic particles, so it is assigned a relative mass of 1. Compared to it, a proton has a relative mass of 1836, meaning that it is 1836 times heavier than an electron. Compared to an electron, a neutron is 1837 times heavier. This property of the particles is summarized in Table 5.1, along with electric charge and location within the atom. Table 5.1 Properties of Subatomic Particles Name
Symbol
Relative Mass
Electric Charge
Location
Proton
p
1836
1+
nucleus
Neutron
n
1837
0
nucleus
Electron
e
1
1–
in energy levels surrounding the nucleus
The periodic table organizes elements by patterns in properties and atomic structure.
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STSE Quick Lab
Developing the Atomic Theory It takes many scientists exploring different possibilities to develop a theory. The atomic theory took shape only after many debates, novel ideas, and experiments. Even today, scientists are making discoveries that will add to our understanding of the atom.
3. Web 2.0 Summarize your findings as a Wiki, a slide presentation, a video, or a podcast, and present them to the class. For support, go to ScienceSource.
Purpose
4. How did your scientist’s contributions alter the previous model of the atom?
To learn about the contribution of particular scientists to atomic theory
5. How were your scientist’s ideas revised once further research was done?
Procedure
6. Do you think today’s atomic model will be changed in future? Why or why not?
1. Choose a scientist to research from the timeline shown in Figure 5.15 below. 2. ScienceSource Find information from two sources on the scientist that you have decided to research. •
Focus on one way that the scientist’s work has shaped our understanding of the atom.
•
Find out about at least one challenge that the scientist had to overcome.
7. Why are collaboration and communication between scientists necessary? 8. Ultimately, who do you think should get credit for the current atomic theory? Justify your response.
410 B.C.E.
1600s C.E.
1700s C.E.
1800s C.E.
1900s C.E.
Democritus Aristotle
Robert Boyle Isaac Newton
Joseph Priestly Antoine Lavoisier Joseph Louis Proust
John Dalton Michael Faraday Jöns Berzelius Dmitri Mendeleev William Crookes Henry Moseley J.J. Thomson
Hantaro Nagaoka Hans Geiger Ernest Rutherford Harriet Brooks Henri Becquerel Marie Curie Niels Bohr Max Planck James Chadwick Werner Heisenberg Louis de Broglie Richard Feynman Murray Gell-Mann Gerd Binning Heinrich Rohrer
Figure 5.15 Timeline of contributors to the atomic theory
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CHECK and REFLECT
Key Concept Review 1. How are atoms and elements related?
11. Use the following Bohr diagram of a fluorine atom to complete this question.
2. In your notebook, redraw and complete the following table. Subatomic Particles Particle
Charge
Location in Atom Question 11
Proton
(a) How many electrons does a fluorine atom have?
Electron Neutron
3. How does J. J. Thomson’s atomic model differ from the model depicted by a Bohr diagram? 4. What particles make up a cathode ray? 5. A statement is missing from the atomic theory given below. What is missing? •
Atoms of different elements have different properties.
•
All matter is made of small, indivisible particles called atoms.
•
Atoms of different elements can combine in specific ways to form new substances.
Connect Your Understanding 6. Atoms contain electrons, which are negatively charged. Why are atoms electrically neutral? 7. Why do you think John Dalton used the Greek word for indivisible to describe atoms? 8. List two ways in which atoms of different elements are different from one another. 9. J. J. Thomson’s discovery about electrons was an important step in the development of the atomic theory. Explain why. 10. History shows that many scientists make important discoveries while they are still students. Use one or more examples from this chapter to illustrate this point.
(b) How many protons does a fluorine atom have? 12. Create a flowchart that shows the atomic model at its different stages of development. Your flowchart should include: • drawings of the different versions of the atomic model • the names of the scientists who contributed to each version of the atomic model • labels to show how past versions of the atomic model are different from today’s model 13. (a) Why do you think it took so long for people to accept the concept of atoms? (b) Describe a discovery or experiment that would have made it easier for people to believe in atoms.
Reflection 14. Consider an element that is important in your life — for example, the element that makes up your watch or ring. How have your ideas about the composition of this element changed since completing this section? For more questions, go to ScienceSource.
The periodic table organizes elements by patterns in properties and atomic structure.
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The Elements
Here is a summary of what you will learn in this section: • All elements can be classified as metals, non-metals, or metalloids based on their properties. • Each element can be identified by its name or symbol, which consists of one or two letters.
Figure 5.16 Many elements have properties that make them well-suited for use in jewellery.
The Elements We Wear Jewellery is very personal. Some people never wear it. Others wear it all the time. Sometimes, as in Figure 5.16, people wear it for special occasions. Jewellery often carries special meanings for the wearer and for others who see it. For example, the element gold is considered a precious metal. Gold is not only rare but also has a deep yellow colour and resists corrosion. These properties make gold both attractive and long lasting. Gold rings, for instance, will not corrode when people wash their hands. Because it is one of the least reactive metals, gold does not usually irritate human tissues. For some people, gold is the only metal that can be worn for long periods without causing discomfort.
Metal Elements and Alloys
Figure 5.17 These pieces of jewellery are made from pure gold and a mixture of gold and other metals.
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Gold is soft and has a low melting point. This means it can be poured into a mould and made into a wide variety of shapes. Solid gold can be pulled, flattened, and bent without breaking it. This allows it to be used in intricate ways. However, when used as a ring or to hold a gemstone in place, gold’s softness becomes a problem. To make gold jewellery stronger, gold is mixed with other metal elements, such as silver (Figure 5.17). A mixture of two or more metals is called an alloy. An alloy of gold and silver is sometimes called white gold because is a lighter
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colour than pure gold. White gold is often used in engagement rings and wedding bands to give them strength and durability. An understanding of the elements and how they combine has led to the invention and mass production of a wide range of alloys. Alloys are not only used in jewellery but also in magnets, sports equipment, vehicles, and many household items. DI Key Activity
B12 Quick Lab Meet the Elements Like the early chemists, you will examine various elements and observe their different properties. You will then look for patterns that you can use to group these elements.
Purpose To become familiar with a variety of different elements and to compare their properties
Materials & Equipment • samples of elements (such as aluminum, carbon, copper, iodine , magnesium , silver, sulphur , or zinc )
• magnet
Procedure 1. Create an observation table in your notebook with the following column headings: Element, Symbol, State, Appearance, Hardness, Magnetism, Electrical Conductivity. Give your table a title. 2. Your teacher will tell you how many element samples to observe. They may be examined in any order. Each time you examine an element, record its name and symbol in your table. 3. Examine each element, and record your observations of its properties in your table. Use the following guidelines to help you:
• low-voltage conductivity tester
State: Is it a solid, a liquid, or a gas at room temperature?
• hand magnifying lens
Appearance: Describe its colour, lustre, opacity, and texture. Hardness: Is it easily scratched? Magnetism: Is it magnetic?
CAUTION: Follow your teacher’s directions about handling each element. Some are too reactive or toxic to touch. If a container is sealed, do not open it.
Electrical Conductivity: Is it conductive?
Questions 4. What similarities are there among most of the elements that conduct electricity? Do any of these elements have different properties from the other conductive elements? Explain. 5. Are all conductive elements that you observed also magnetic? 6. Given that copper is a metallic element, classify each of the elements that you observed as either metallic or non-metallic.
Figure 5.18 Pure iodine is a solid, shiny, deep purple coloured crystal.
The periodic table organizes elements by patterns in properties and atomic structure.
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Elements and Their Symbols Approximately 90 elements occur naturally on Earth, and in recent years, chemists have made more than 25 new elements. Based on their properties, all the elements can be divided into three classes: metals, non-metals, and metalloids.
Metals
Figure 5.19 Silver metal is used in jewellery, coins, and table cutlery, which is sometimes called silverware.
Suggested Activity • B14 Quick Lab on page 186
Most of the elements are metals. Of the metals, most are shiny and silver or grey in colour. They are all excellent conductors of electricity and heat. They are also malleable and ductile. As described in Chapter 4, a malleable substance can be beaten into sheets, and a ductile substance can be stretched into long wires. Silver is an example of a metal (Figure 5.19). Pure, polished silver has an attractive, almost white appearance. It can be moulded and shaped easily and is often used to make jewellery or special table cutlery. It is also one of the best conductors of electricity. Some metals, such as sodium, react explosively with water. Others, such as platinum, will not react even if mixed with strong acids. Mercury metal is unique in that it is a liquid at room temperature.
Non-Metals Only 17 elements are non-metals. They are grouped together mainly because they do not resemble metals. For example, 11 of the non-metals are gases at room temperature, 5 are solids, and 1, bromine, is a red-brown liquid (Figure 5.20). Sulphur is an example of a solid non-metal (Figure 5.21). It is brittle and will crumble if struck. It does not conduct electricity and is not shiny. It is reactive and will burn in air to produce a poisonous gas. With a little heating, it will melt into a liquid.
Figure 5.20 The element bromine is a red-brown liquid at room temperature. Pure bromine is very reactive and toxic.
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Figure 5.21 The element sulphur is a yellow solid.
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Metalloids The remaining elements are metalloids. The metalloids are elements with metallic and non-metallic properties. Metalloids conduct electricity but not very well, and so they are called semiconductors. It is easier to control the flow of electricity through semiconductors than through conductors. For this reason, metalloids are often used as semiconductors in electronic devices, such as computers. Silicon is the most common metalloid. Pure silicon is shiny and grey, but unlike a metal, it is brittle (Figure 5.22). Although pure silicon is rare in nature, in combination with other elements it makes up sand and other many other compounds. The microscopic structures shown in Figure 5.23 are made from a silicon compound. About 40 percent of the mass of almost any rock comes from silicon. It is also a major component of glass.
Figure 5.22 Pieces of pure silicon
Figure 5.23 These microscopic structures, called silicon nanoflowers, contain wires that could be used in tiny electronic devices. Each flower is about 0.005 mm long.
Element Symbols Each language has its own name for each of the elements, and so to help with communication, chemists worldwide have agreed to use the same set of symbols for the elements. The symbols are all taken from the Roman alphabet, which is the same alphabet used for English. For example, sulphur’s symbol is S and carbon’s symbol is C. The names of the elements silicon and silver, like sulphur, begin with the letter “s.” In fact, they both begin with “si.” To tell them apart, silicon was given the symbol Si. Silver, which has the Latin name argentum, was given the symbol Ag. Table 5.2 on the next page lists some of the elements’ names and symbols. An element symbol consists of one or two letters. The first letter is always capitalized. If there is a second letter, it is not capitalized. These rules about capitalization are very important. For example, the symbol Co stands for the metal element cobalt, while CO represents a poisonous compound made up of carbon (C) and oxygen (O) produced in car exhaust. The periodic table organizes elements by patterns in properties and atomic structure.
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Table 5.2 Selected Element Names and Symbols English Name
Symbol
Non-English Name and Meaning
hydrogen
H
Hydro genes – water generating
helium
He
Helios – the Sun
neon
Ne
Neos – new
argon
Ar
Argos – inactive or idle
fluorine
F
Fluere – flowing
chlorine
Cl
Chloros – yellow-green
bromine
Br
Bromos – pungent odour
iodine
I
Iodes – violet
oxygen
O
Oxy genes – acid forming
phosphorus
P
Phosphoros – light bringer
carbon
C
Carbo – charcoal
silicon
Si
Silex – flint
germanium
Ge
Germania – Germany
lithium
Li
Lithos – stone
sodium
Na
Natrium – Latin name for soda ash
potassium
K
Kalium – Latin name for potash
rubidium
Rb
Rubidius – ruby-red
magnesium
Mg
Magnesia – a location in Greece
calcium
Ca
Calx – limestone
chromium
Cr
Chroma – colour
iron
Fe
Ferrum – ancient Latin name
nickel
Ni
Kupfernickel – devil’s copper
copper
Cu
Cuprum – Cyprus
silver
Ag
Argentum – ancient Latin name
gold
Au
Aurum – glow of sunrise
mercury
Hg
Hydragyrum – liquid silver
lead
Pb
Plumbum – ancient Latin name
Understanding Chart Features Charts or tables are organized in columns and rows. Good readers read down the columns and across the rows, and check for other organizational features. Note the three rows where only the first column has an entry. “Non-Metals,” “Metalloids,” and “Metals” are subheadings, indicating that information is divided into three subcategories in this chart.
Non-Metals
Metalloids
Metals
W O R D S M AT T E R
Titanium (Ti) is a strong yet light metal element. It is named for the Titans, powerful gods of Greek mythology.
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Atoms, Elements, and Compounds
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Learning Checkpoint 1. What makes mercury different from other metal elements? 2. Give an example of a metal element with the following properties. (a) It conducts heat and electricity. (b) It is shiny. (c) It reacts explosively with water. 3. (a) Compare and contrast the properties of silver, sulphur, and silicon. (b) How are these elements classified? 4. Give the symbols for the following elements. (a) nitrogen
(b) nickel
(c) lead
5. How can the meaning of the Latin name for gold help you to remember its element symbol?
Some Common Elements Human history has long been influenced by the availability of certain elements. Iron, for example, occurs mainly in Earth’s surface as iron ores, minerals that contain iron. The Iron Age began several thousand years ago, when technologies to obtain iron from iron ore became widespread. When another element, carbon, was added to iron, steel was formed. Two other elements, hydrogen and oxygen, can combine to make water, a pure substance vital to living organisms. Another two elements, sodium and chlorine, can combine in another pure substance that rivals water in importance: table salt. Without either water or salt, life as we know it could not survive.
Iron (Fe) Iron is quite common, and once separated from ore, it can be used for a wide range of items. Iron is very strong, and when combined with carbon to make steel, it is even stronger (Figure 5.24). Another advantage of steel is that it can be made fairly resistant to corrosion. In contrast, plain iron corrodes easily in moist air, forming an orange compound known as rust. Like most metals, iron is silver-grey and can be molded and shaped when heated. It is hard enough to keep a sharp edge, a property that people have used for centuries in order to make tools and household items.
Figure 5.24 Iron is very strong and somewhat flexible. These properties make it useful for building bridges and other structures.
The periodic table organizes elements by patterns in properties and atomic structure.
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Carbon (C)
Figure 5.25 Diamonds are found in a rock called kimberlite. Extremely high temperatures and pressures are needed for diamonds to form.
Carbon exists in several forms, including graphite and diamond (Figure 5.25). Both diamonds and graphite form underground as the remains of organisms become compressed. Coal, a form of graphite, is a black solid made mostly of carbon. Around the world, coal is mined and burned to produce heat, mainly for generating electricity. Burning coal produces air pollution and is a major contributor of greenhouse gases to the atmosphere. These gases can affect our climate. Another form of graphite is used for pencil leads. Diamond is also pure carbon. However, in diamond the carbon atoms are connected differently than they are in graphite. Diamond is the hardest natural substance known, yet light can easily pass through it. These properties make it a prized gemstone. Carbon is also one of the main building blocks of life. Your body and the food you eat contain many different carbon compounds.
Hydrogen (H) Hydrogen is the most common element in the universe. It makes up most of the atoms in stars as well as large planets like Jupiter and Saturn. Hydrogen atoms are the simplest and lightest of all atoms. The atoms of all other elements can be thought of as combinations of hydrogen atoms. At the centre of stars, including our own Sun, hydrogen atoms combine to form atoms of other elements. On Earth, almost all of the hydrogen that is present is in water. Pure hydrogen gas is colourless, odourless, and lighter than air. Its low density means it can be used in weather balloons (Figure 5.26). It is also extremely flammable, which is why it is not often used in balloons that carry people. Figure 5.26 A hydrogen-filled weather balloon
Oxygen (O)
Figure 5.27 This person is using an oxygen tank to help her breathe more easily.
Pure oxygen is a gas at room temperature. It makes up about 21 percent of the air we breathe, and our bodies need a constant supply of oxygen to survive (Figure 5.27). Just as pure carbon can exist in more than one form, so can pure oxygen. The oxygen gas that we breathe is in the form of two oxygen atoms connected together. This form is simply called oxygen gas. Most of the oxygen gas in Earth’s atmosphere comes from plants and algae, which produce oxygen while using sunlight to make sugar. Ozone is a form of pure oxygen in which three oxygen atoms are connected together. Ozone is toxic to breathe, and when it occurs close to the ground it is a pollutant (Figure 5.28). However, in the upper atmosphere, ozone forms a layer that
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Atoms, Elements, and Compounds
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absorbs harmful ultraviolet light. Without the ozone layer, ultraviolet light would kill much of life on Earth. Oxygen is the most common element on Earth’s surface. Oxygen makes up more than 50 percent of the mass of most rocks, in which it is combined with the element silicon. When certain kinds of rocks are ground up, they become sand, which can melt and reharden to form glass. Most of the atoms in glass are oxygen atoms.
Take It Further Find out about the newest elements to have been discovered or named in the past few years, and present your findings in a movie poster. Begin your search at ScienceSource.
Figure 5.28 A leaf damaged by ground-level ozone
Sodium (Na) Sodium is a metal, and so it shares many properties with iron. Both conduct electricity and are shiny, silver-grey, malleable, and ductile. However, they also have distinct differences. Iron reacts slowly in moisture to form rust. In contrast, sodium metal reacts immediately and violently if it contacts either air or water (Figure 5.29). Pure sodium metal is usually stored in oil, where it can remain without reacting for a long time. Sodium metal is so soft that a knife easily cuts right through it. Sodium also melts quite easily as it has a melting point of 98ºC, two degrees lower than the boiling point of water. These properties may seem unfamiliar because sodium most commonly exists in compounds such as table salt, which it forms with the element chlorine.
Figure 5.29 Sodium metal burns in air.
Chlorine (Cl) Chlorine, a non-metal, is a yellow-green gas at room temperature (Figure 5.30). High concentrations of chlorine gas are toxic and will quickly destroy lung tissue. At lower concentrations, chlorine is extremely useful as a disinfectant. It is added to swimming pools and community water supplies in order to kill bacteria and other organisms that spread disease.
Figure 5.30 Used in the correct concentrations, chlorine will purify community water supplies.
The periodic table organizes elements by patterns in properties and atomic structure.
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B13 Skill Builder Activity Using a Dissecting Microscope A dissecting microscope is a type of compound light microscope used to view small objects. You will examine a leaf with the dissecting microscope in order to practise your microscopy skills. 1. Carry the microscope with two hands. Place it on the lab bench, and remove its cover. Plug it in, and turn it on. 2. Rotate the nosepiece so that the objective lens with the lowest magnifying power is in place.
3. Place a leaf on the stage. While watching from the side, use the coarse adjustment knob to bring the stage and objective lens as close as possible without the lens touching the leaf. 4. While looking through the ocular lenses of the microsope, use the fine adjustment knob to focus on the leaf. Focus in and out to see what happens to the image of the leaf.
B14 Quick Lab Growing Silver A crystal is a solid with atoms that are arranged in a very regular way. Some crystals, such as salt crystals, contain two or more types of elements. Other crystals, such as silver crystals, contain atoms of only one type of element (Figure 5.31). To produce a sample of silver, you can grow a crystal from its atoms.
Purpose
Materials & Equipment • dissecting microscope • 2 cm of copper ribbon
1. Place a piece of copper ribbon on the microscope slide. 2. Place the slide on the microscope stage, and focus on one edge of the piece of copper ribbon. Record your observations of the copper ribbon. 3. Squeeze a drop of silver nitrate solution onto the copper ribbon.
To grow a silver crystal
• microscope slide
Procedure
• 0.1 M silver nitrate solution in a dropper bottle
4. Look through the microscope to observe changes to the copper ribbon. Look for silver crystals forming on the edges of the copper. 5. Wash your hands after putting the materials and equipment away.
Questions
CAUTION: Do not get silver nitrate on your skin. Wear gloves for this activity.
6. Based on your observations, what are some of the properties of copper and silver? 7. How do you know that the crystals that formed were silver crystals and not copper? 8. Do you think the changes you observed were physical or chemical? Explain.
Figure 5.31 The arrangement of atoms in a silver crystal is very regular.
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9. Silver is a highly valued element. Why could we not “grow” silver on a massive scale instead of mining it?
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CHECK and REFLECT
Key Concept Review 1. Give the names and symbols of three elements that are gases at room temperature. 2. (a) Give the names and symbols of the two elements that are liquids at room temperature. (b) Classify each of the elements you named in (a) as a metal, a metalloid, or a non-metal.
6. List the following elements in order of their ability to conduct electricity, starting with the least conductive: Si, Ag, S.
Connect Your Understanding 7. The metal element shown in the following photograph reacts violently with water. Suggest the identity of the element shown. Justify your response.
3. Using Table 5.2 on page 182, identify what element was named after each meaning below, then write the symbol for that element. (a) Germany (b) ruby-red (c) the Sun Question 7
(d) violet (e) water generating
8. List two elements present in each of the following.
(f) acid forming (g) charcoal
(a) steel
(h) colour
(b) water
(i) liquid silver
(c) table salt
(j) flowing 4. Using Table 5.2 on page 182, find the common name and symbol of each element from the ancient Latin name provided below. (a) natrium
9. (a) What is ozone? (b) Explain how ozone can be both harmful and beneficial to life. 10. What pure elements can you identify as you look around your surroundings? What are the elements being used for?
(b) ferrum (c) argentum (d) plumbum
Reflection
5. Using Table 5.2 on page 182, find and list the following. (a) the symbols of five elements beginning with the letter C
11. Briefly describe three environmental issues related to pure elements that you learned about in this section.
(b) the names of three elements named after places
12. Write five element names that you were unfamiliar with before reading this section.
(c) the symbols for any five non-metals with symbols composed of two letters
For more questions, go to ScienceSource.
The periodic table organizes elements by patterns in properties and atomic structure.
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The Periodic Table
Here is a summary of what you will learn in this section: • The periodic table organizes the elements by their properties, such as the mass of each element’s atoms and the element’s melting point.
H=1
• Atomic number is the number of protons in an atom and uniquely identifies an element. • Bohr diagrams of the first 20 elements of the periodic table reveal important patterns that relate to the elements’ properties.
Li = 7
Be B C N O F Na
= = = = = = =
9, 4 11 12 14 16 19 23
Ti V Cr Mn Fe Ni = Co Cu Mg = 24 Zn ? Al = 27,4 Si = 28 ? P = 31 As S = 32 Se Br Cl = 35, 5 K = 39 Rb ? = 45 Sr ?Er = 56 Ce ?Yt = 60 La ?In = 75, 5 Di Th
= = = = = = = = = = = = = = = = = = =
50 51 52 55 56 59 63,4 65,2 68 70 75 79,4 80 85,4 87,5 92 94 95 118?
Zr Nb Mo Rh Ru Pl Ag Cd Ur Su Sb Te I Cs Ba
= = = = = = = = = = = = = = =
90 94 96 104,4 104,4 106,6 108 112 116 118 122 128? 127 133 137
? Ta W Pt Ir Os Hg
= = = = = = =
180. 182. 186. 197,4 198. 199. 200.
Au = 197? Bi = 210 Tl = 204 Pb = 207
Figure 5.32 Dmitri Mendeleev arranged the elements according to certain properties.
Patterns among the Elements
Figure 5.33 Mendeleev gathered information on each known element and wrote it on a card.
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By the 1780s, chemists wondered why some elements, such as oxygen, were gases, while others, such as gold, were metals. To complicate matters, by the 1860s, the list of known elements had grown to 63. No one knew if that list included all the elements that existed or whether there were hundreds or even thousands more that were still undiscovered. Many chemists continued to search for a unifying pattern among the elements. Then, in 1867, Russian chemist and teacher Dmitri Mendeleev (1834–1907) found the pattern (Figure 5.32). He did it by gathering all the information that he could about the known elements and writing it down on cards, using one element per card (Figure 5.33). The information included properties such as estimates of the mass of the atoms of each element, colour, density, melting point, and what each element did or did not react with. He then sorted the cards into rows and columns, based on similarities in the elements’ properties. This arrangement of cards formed a table, as shown in Figure 5.32. Within Mendeleev’s table, and for the first time in history, a complete pattern of the elements emerged.
Atoms, Elements, and Compounds
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A Table Based on Properties In Mendeleev’s table, all the cards representing metals ended up on one side, and all the non-metals ended up on the other. Metalloids were in the middle. Even most of the elements that were gases at room temperature were grouped together. Mendeleev was on to something. Mendeleev knew that some elements were very similar, and it made sense to him to group them together (Figure 5.34). For example, he grouped together sodium, lithium, and other metals that reacted violently with water. Mendeleev had so much confidence in his arrangement that he left a gap in his table if he could not find an element with the right properties to put in a column. The gap represented an element that was yet to be discovered. Other chemists were doubtful. Then, in 1886, the element germanium was discovered. Its properties were an exact match of the properties predicted for a missing element in Mendeleev’s table. After that, other scientists were convinced that Mendeleev had it right. Today, we use a table based on Mendeleev’s table called the periodic table of the elements.
Figure 5.34 Dmitri Mendeleev was the first to create a table that logically organized all the elements, including those undiscovered at the time.
B15 Quick Lab Exploring the Periodic Table Your teacher will provide you with a copy of the periodic table. Within the periodic table, you will look for patterns among the elements’ properties.
Purpose To become familiar with the periodic table
Materials & Equipment
2. All the elements to the left of the metalloids, except hydrogen, are metals. All the elements to the right of the metalloids are non-metals. Label the metals and non-metals, but do not shade them. 3. All the elements in the farthest left column, except hydrogen, react violently with water. Shade them the same colour, and label them “alkali metals.” 4. All the elements in the column to the right of the alkali metals are slightly less reactive than the alkali metals. Shade them another colour, and label them “alkaline earth metals.”
• a periodic table • pencil crayons or highlighters
Procedure 1. Find the element boron (B) and shade it in. Then, with the same colour, shade in all elements that make a diagonal below and to the right of boron, starting with silicon (Si). Finally, shade in germanium (Ge), antimony (Sb), and polonium (Po). These elements are the metalloids.
5. Find column 17, and shade all the elements in it the same colour. Label the column “halogens.” Find column 18, and shade those elements their own colour. Label them “noble gases.”
Question 6. Why does it make sense to colour columns rather than rows?
The periodic table organizes elements by patterns in properties and atomic structure.
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The Modern Periodic Table Figure 5.36 on the next page shows the periodic table of the elements. The periodic table is a chart that places all of the elements in rows and columns. In the modern periodic table, elements are listed from left to right and top to bottom according to a property called atomic number.
Atomic Number 1p
H atom
2p 2n
He atom Figure 5.35 A hydrogen atom has one proton, and a helium atom has two protons.
Atomic number is the number of protons in an atom of an element. The lowest atomic number is 1, which is the atomic number of the element hydrogen (H) (Figure 5.35). This means that every hydrogen atom has one proton in its nucleus. Hydrogen is placed in the top row and farthest left column of the table. The next element in the periodic table is helium (He), which has atomic number 2. All helium atoms have two protons. Another way to look at it is that any atom with two protons must be a helium atom. Moving down to the next row and back to the farthest left column, the element with atomic number 3 is lithium (Li). Atomic number increases by one with each consecutive element. This increase continues though the entire table until the atomic number is well past 100. No one knows what the highest possible atomic number is, but as of 2009 it was 118.
Learning Checkpoint 1. Use the periodic table to find the atomic number of each of the following elements. (a) C
(b) O
(c) Na
(e) S
(f) Cl
(g) Fe
(d) Si
2. How many protons are in an atom of each of the following elements? (a) lithium
(b) nitrogen
(c) fluorine
(d) aluminum
(e) copper
(f) gold
3. Name the element with the following number of protons.
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(a) 1
(b) 2
(c) 10
(e) 20
(f) 31
(g) 47
Atoms, Elements, and Compounds
(d) 19
Be
2+
Ca
magnesium 24.31 1 + 20 2 + 21
sodium 22.99
K
Mg
Na
beryllium 9.01 + 1 12 2+
4
Sc
3 3+
22
Ti
4 4+ 3+
23
non-metal
metalloid
V
5 5+ 4+
Br
C
24
6
Cr
gas
liquid
solid
3+ 2+
25
Mn
7 2+ 4+
26
Fe
8
name atomic mass
symbol
atomic number
3+ 2+
27
9
O
2+ 3+
28
Ni
2+ 3+
2–
10
oxygen 16.00
Co
8
29
Cu
11 2+ 1+
30
Zn
12
ion charge (if more than one, first one is the most common)
Al
boron 10.81
B 3+
14
6
Si
carbon 12.01
C
14
15
7
P
nitrogen 14.01
N
15
3–
3–
16
8
S
oxygen 16.00
O
16
2–
2–
17
9
Cl
fluorine 19.00
F
17
1–
1–
18
10
Ar
neon 20.18
Ne
helium 4.00
He
18
Ga
Ge
As
5
Se
Br
Kr
aluminum silicon phosphorus sulphur chlorine argon 26.98 28.09 30.97 32.07 35.45 39.95 – – – + 2 + 31 3 + 32 3 2 1 4 33 34 35 36
13
5
13
2
Sr
The periodic table organizes elements by patterns in properties and atomic structure.
francium (223)
Fr
1+
88
7
6
radium (226)
Ra
2+
La
3+
89–103
57–71
Ac
3+
actinium (227)
89
lanthanum 138.91
57
Y
yttrium 88.91
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
90
58
thorium 232.04
Th
cerium 140.12
Ce 4+
3+
rutherfordium (261)
Rf
hafnium 178.49 104
Hf
Pr 4
3+
60
Nd 4
3+
seaborgium (266)
Sg
W
tungsten 183.84 106
61
Pm
3+
bohrium (264)
Bh
Re
rhenium 186.21 107
62
Sm
3+ 2+
hassium (277)
Hs
Os
osmium 190.23 108
Pt
Ds
platinum 195.08 110
Rg
gold 196.97 111
Au
63
Eu
3+ 2+
64
Gd
3+
65
Tb
4
3+
meitnerium darmstadtium roentgenium (271) (272) (268)
Mt
Ir
iridium 192.22 109
66
Dy
3+
ununbium (285)
Uub
Hg
mercury 200.59 112
Tl
67
Ho
3+
ununtrium (284)
Uut
113
thallium 204.38
Bi
Uup
115
bismuth 208.98
Po
4
Uuh
116
polonium (209)
At
protactinium 231.04
Pa
uranium 238.03
U
neptunium (237)
Np
6
plutonium (244)
Pu
4
americium (243)
Am
curium (247)
Cm
berkelium (247)
Bk
Es
einsteinium (252)
Cf
californium (251)
118
radon (222)
Rn
Uus Uuo
117
astatine (210)
68
Er
3+
69
Tm
3
3+
70
Yb
3+ 2+
71
Lu
2+
ununquadium ununpentium ununhexium ununseptium ununoctium (289) (288) (293) (?) (294)
Uuq
lead 207.21 114
Pb
fermium (257)
Fm
mendelevium (258)
Md
3
nobelium (259)
No
lawrencium (262)
Lr
dysprosium holmium erbium thulium ytterbium lutetium praseodymium neodymium promethium samarium europium gadolinium terbium 162.50 164.93 167.26 168.93 173.04 174.97 140.91 144.24 (145) 150.36 151.96 157.25 158.93 5 + 92 6 + 93 5 + 94 4 + 95 3 + 96 3 + 97 3 + 98 3 + 99 3 + 100 3 + 101 2 + 102 2 + 103 3+ 91 + + + + + + +
59
dubnium (262)
Db
tantalum 180.95 105
Ta
palladium silver cadmium indium tin antimony tellurium iodine zirconium niobium molybdenum technetium ruthenium rhodium xenon 106.42 107.87 112.41 114.82 118.71 121.76 127.60 126.90 91.22 92.91 95.94 (98) 101.07 102.91 131.29 + + + + + + + + + + + + – + 4 5 6 7 4 4 4 3 2 1 2 3 1 2 78 79 80 81 82 83 85 86 72 73 74 75 76 77 84 + 2+ 1+ 1+ 3+ 4+ 5+
Figure 5.36 The periodic table of the elements
87
Ba
barium 137.33
Cs
cesium 132.91
rubidium strontium 85.47 87.62 + 1 2+ 55 56
Rb
nickel copper zinc gallium germanium arsenic selenium bromine potassium calcium scandium titanium vanadium chromium manganese iron cobalt krypton 58.69 63.55 65.41 69.72 72.64 74.92 78.96 79.90 39.10 40.08 44.96 47.87 50.94 52.00 54.94 55.85 58.93 83.80 + + + + + + + + + + + + + + – – + 1 2 3 4 5 6 7 3 3 2 1 2 3 4 2 1 3 52 46 47 48 49 50 53 54 37 38 39 40 41 42 43 44 45 51 + 3+ 4+ 4+ 2+
19
11
lithium 6.94
Li
1+
2
metal
Home
7
6
5
4
3
2
3
H
hydrogen 1.01
1+
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ion charges atomic number
3+ 2+
26
Fe iron 55.85 atomic mass
Figure 5.37 Information from the periodic table about iron (Fe)
Fe
3e
+
Fe3
Figure 5.38 When an iron atom loses electrons, it becomes a positive ion.
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Atomic Mass and Ion Charge Each element has its own square on the periodic table. The information given in the square is not always the same on different versions of the periodic table, but the element’s name, symbol, and atomic number are almost always given. Figure 5.37, taken from the periodic table on the previous page, shows two other pieces of information: atomic mass and ion charge. Atomic Mass Atomic mass is the average mass of an element’s atoms. Atomic mass is given in atomic mass units (amu). As Figure 5.37 shows, the atomic mass of iron is 55.85 amu. From the periodic table, we can see that the atomic mass of hydrogen is 1.01 amu. This means that iron atoms are about 55.85 times heavier than hydrogen atoms, which are the least massive of all atoms. Atomic masses are always expressed as decimal fractions. One reason that they do not have whole number values is that, except for fluorine, atoms of the same element have different numbers of neutrons. For example, the most common type of hydrogen atom has one proton and one electron but no neutron. A small percentage of hydrogen atoms have one proton, one electron, and one neutron, and an even smaller percentage have one proton, one electron, and two neutrons. Recall that most of an atom’s mass comes from its protons and neutrons. For this reason, hydrogen atoms with different numbers of neutrons have different masses. The atomic mass of hydrogen is an average of these masses. Notice that atomic mass generally increases in order of atomic number. There are a few exceptions to this pattern. For example, iodine (I) has a lower atomic mass than tellurium (Te). Ion Charge Ion charge is the electric charge that an atom takes on when it loses or gains electrons. An atom or group of atoms that has lost or gained electrons is called an ion. Metal atoms can lose electrons in certain situations. Electrons have a negative charge, and so an atom that loses electrons becomes a positive ion. For example, if an iron atom loses three electrons, it becomes an ion with a 3+ charge (Figure 5.38). If an iron atom loses two electrons, it becomes an ion with a 2+ charge.
Atoms, Elements, and Compounds
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Elements with atoms that can form similar ions are grouped together in the periodic table. Metals generally lose electrons and become positive ions. Many non-metals can gain electrons and so become negative ions. Some elements do not form ions. Helium, for example, does not normally form ions. For these elements, no ion charges are shown in their squares in the periodic table.
Learning Checkpoint 1. Use the periodic table to find the atomic mass for each of the following elements. (a) H
(b) He
(c) N
(d) F
(e) S
(f) Ca
(g) Ag
2. Name the element with the following atomic mass. (a) 12.01 amu
(b) 16.00 amu (c) 39.10 amu
(d) 83.80 amu
3. What is the electric charge on an ion of each of the following elements? (a) Li
(b) Be
(c) N
(d) S
(e) Al
(f) I
4. Although the element hydrogen is a non-metal, it is located on the left side of the periodic table. Explain how placing hydrogen in this position relates to its ion charge. 5. Describe the patterns in atomic masses and ion charges in the periodic table.
Periods and Chemical Families The periodic table has seven horizontal rows. Each of these rows is called a period. A number written on the left side of the table identifies each period. For example, hydrogen and helium are in Period 1. Potassium is the first of 18 elements in Period 4. There are 18 vertical columns in the periodic table, and each represents a different group (also called a chemical family). The elements within a group share certain physical and chemical properties. Each group has its own number, written at the top of the periodic table. For example, the element carbon (C) is in Group 14. It is also common to refer to a group by the first element in it. Group 14 is also called the carbon group. Some groups have special names (Figure 5.39). We will discuss three of these very important groups in more detail: • alkali metals • halogens • noble gases
18 1 1
H Alkali Metals
Noble Gases
2 Alkaline Earth Metals
17 Halogens
2
He
3
4
9
10
Li
Be
F
Ne
11
12
Na
Mg
Groups 3 - 16
17
18
Cl
Ar
19
20
35
36
K
Ca
Br
Kr
37
38
53
54
Rb
Sr
I
Xe
55
56
85
86
Ca
Ba
At
Rn
87
88
Fr
Ra
Figure 5.39 Four groups in the periodic table known by special names
The periodic table organizes elements by patterns in properties and atomic structure.
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Properties within Groups When we compare the physical properties of elements within groups, a number of patterns become clear. Refer to the periodic table on page 191 as you read about these patterns. Alkali Metals (Group 1): Li, Na, K, Rb, Cs
• Similarities: All of these metals are silver-grey in colour (Figure 5.40). Like other metals, they are malleable and ductile, and they conduct electricity and heat. However, compared to other metals, the alkali metals have low melting points. They all melt below 170°C, a temperature easily achieved by most ordinary kitchen ovens. They are all soft enough to cut with a knife. In addition, they all react easily with water and air.
Figure 5.40 Alkali metals
• Differences: There is a gradual change in the physical properties in this group from the first element, at the top, through to the last, at the bottom. Moving from lithium to cesium, there is a regular increase in density. The elements also get softer and easier to cut. Lithium’s melting point is 170°C, while potassium’s is 64°C. Cesium’s melting point is just 28°C. Halogens (Group 17): F, Cl, Br, I
• Similarities: All of these elements are non-metals. Each has a noticeable colour. Although bromine is a liquid and iodine is a solid at room temperature, with slight heating they form gases, like the other halogens. All are very reactive, and chlorine, bromine, and iodine can be used as disinfectants. • Differences: From fluorine, the first element in the group, down through to iodine, the colours of the halogens grow in intensity (Figure 5.41). Their melting points also gradually increase from –219°C for fluorine to 113°C for iodine.
Figure 5.41 The halogens. From left to right: fluorine, chlorine, bromine, and iodine
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Atoms, Elements, and Compounds
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Noble Gases (Group 18): He, Ne, Ar, Kr, Xe, Rn
• Similarities: Although all exist naturally as colourless gases, these elements will glow with bright colours if an electric current is passed through them, as in a neon light (Figure 5.42). None of these gases is chemically reactive except in certain special situations. • Differences: The density of the gases increases steadily moving from helium through to radon. Balloons filled with helium or neon will rise in the air, with helium balloons rising faster than neon balloons. Argon balloons sink slowly in air. Balloons filled with krypton, xenon, or radon would sink quite quickly in air, with radon balloons sinking the fastest.
Figure 5.42 This lighted glass sculpture of a sea anemone contains noble gases. As an electric current runs through the gases, they light up, each with a different colour. Some of the gases are denser than the others, making the sculpture different colours in different areas.
Learning Checkpoint 1. Give the names and symbols for the elements found at these locations in the periodic table. (a) Period 3, Group 1
(b) Period 2, Group 13
(c) Period 4, Group 11
(d) Period 5, Group 17
2. Give the period and group for each of the following elements. (a) Mg
(b) Si
(c) Cl
(d) He
(e) Au
(f) Pb
3. Compare and contrast the physical properties of different alkali metals. 4. Compare and contrast the chemical and physical properties of the halogens and the noble gases.
The periodic table organizes elements by patterns in properties and atomic structure.
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During Reading Fixing Up Understanding Using Key Words As you read, identify the key words and write them in your notebook. Look at the key words, and try to restate what you read using the words as cues. Talk with a partner to compare what each of you understood from what you read.
Suggested Activity • B17 Quick Lab on page 200
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Atomic Theory Supports the Periodic Table Mendeleev created his periodic table long before studies of atomic structure revealed the arrangements of subatomic particles. As a result, Mendeleev did not know about atomic number, which is used to order the elements in the modern periodic table. Instead, he used atomic mass. Similarly, he did not know about electrons or their arrangements within atoms. When electron arrangements are considered, it makes Mendeleev’s work all the more remarkable.
Chlorine: A Typical Atom Atoms of all elements have the same basic structure but different numbers of protons, neutrons, and electrons. Chlorine is an example. The element chlorine is used as a disinfectant in swimming pools and to purify drinking water. A diagram of an atom of chlorine is shown in Figure 5.43 on the next page. Notice that the number of protons and the number of electrons are equal. This is true of all atoms. The Nucleus The nucleus, shown at the centre of the chlorine atom, and also enlarged, is a tiny part of the atom that contains protons and neutrons gathered together into a ball. The nucleus contains only a small part of an atom’s total volume. Depending on the atom, the region outside the nucleus of an atom is 10 000 to 50 000 times the diameter of the nucleus.
• All chlorine atoms have 17 protons. Each proton has a charge of 1+, so the total positive charge in the nucleus is therefore 17+. • Different kinds of chlorine atoms can have different numbers of neutrons. It is the number of protons in an atom that determines what element the atom is, not the number of neutrons. The most common types of chlorine atoms have 18, 19, or 20 neutrons. • The nucleus contains 99.99% of the mass of the atom because protons and neutrons have much greater mass than electrons.
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Atoms, Elements, and Compounds
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neutron
proton
nucleus
valence electron inner electron
valence shell
inner shells
(a)
chlorine atom
(b)
Figure 5.43 (a) A Bohr diagram of a chlorine atom, which contains 17 protons and 17 electrons. The number of neutrons varies between chlorine atoms. (b) A diagram of the nucleus of a chlorine atom
Suggested STSE Activity • B18 Decision-Making Analysis Case Study on page 201
Electrons Electrons exist in shells, or energy levels, surrounding the nucleus. The innermost shell can hold a maximum of two electrons. Each of the next two shells can hold up to eight. Electrons often exist in pairs.
• Electrons occupy more than 99.99% of an atom’s volume. • Electrons can move between energy levels. • The outermost shell that has electrons in it is called the valence shell. Electrons in this shell are called valence electrons. Other shells containing electrons are called inner shells, and the electrons in them are called inner electrons. The properties of elements are strongly affected by their valence electrons. Early researchers of the atom were surprised at first to discover that when a shell becomes more than half-filled, the electrons begin to pair up, as shown in Bohr diagrams. Even though the negatively charged electrons repel each other, pairing helps electrons to get closer to the positive protons in the nucleus. Friedrich Hund (1896–1997), a German physicist, was the first to work out how electron pairing occurs (Figure 5.44).
Figure 5.44 Physicist Friedrich Hund
The periodic table organizes elements by patterns in properties and atomic structure.
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Take It Further
Patterns in the Arrangements of Electrons
People have used various shapes, colours, and arrangements to organize the elements in meaningful ways. Some are shown on the next page. Go to ScienceSource to start your search for different versions of the periodic table.
Figure 5.45 shows Bohr diagrams for the first 20 elements of the periodic table. As you examine the Bohr diagrams, look carefully at the electrons in the outer shells. A very important pattern in the arrangement of electrons is that elements in the same group have the same number of valence electrons. Notice, in particular, the following points: • Group 1: Atoms of hydrogen, lithium, and sodium each have one valence electron. Although hydrogen is not in the same group as the alkali metals, it does share some chemical properties with them because of their similar valence electron arrangements. For example, they can all form ions with a 1+ charge. • Group 18: A helium atom has only two valence electrons, which is the maximum number for the first energy shell. Atoms of neon and argon each have eight valence electrons, the maximum number for the second and third shells. The noble gases share many properties because their atoms all have filled valence shells. The number of valence electrons is not only related to the physical properties of a group of elements. The number of valence electrons is also related to the ways in which atoms of elements combine to form compounds.
1
18
1
1
2
H
He
13
2 3
2
4
Li
11
3
Be
12
Na
19
4
5
B
13
Mg
14 6
C
14
Al
15 7
N
15
Si
16 8
O
16
P
S
Ca
Figure 5.45 A segment of the periodic table showing electrons arrangements for the first 20 elements
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10
F
17
20
K
17 9
Ne
18
Cl
Ar
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Organizing the Periodic Table in Different Ways Scientists continue to organize the elements in different ways. Dr. Theodor Benfey, a U.S. chemist, suggested a spiral version of the periodic table (Figure 5.46). In Dr. Benfey’s periodic table, the elements are shown in an unbroken series, starting with hydrogen and radiating outward. Figure 5.47 shows another periodic table, known as the physicist’s periodic table. This periodic table is three-dimensional and groups the elements according to the energy levels of their electrons.
Suggested Activity • B19 Inquiry Activity on page 202
H
n=1
N C
n=2
Li
Cm Bk
Pu U Fr
Pa
Rn Xe Rb Ar
I Br
Po
Te
Se
Cl S
Ac
Ba
Kr At
Ge
Jl
Rf
W
V Cr
Cu Cd
TI
Ni Ag
Fe Ru
Pd
Os
Rh
Hg
Pb
Co
Au
Bh
Re
Tc
Mn
Zn
Hn
Pt
n=7
Ir
112
111
110
Mg Al
Cl Ar
Sc
Tb
Ni Cu
Zn
n=4
Mo
Ti
Co
Na
Eu Tc Ru Dy Sm Mo As Se Rh Ho Pm Nb Ge K Ca Br Pd Er Nd Zr Ga Kr Aq Tm Pr Y Cd Yb Ce Lu Cm Bk Am Re Os Cf Pu W S b Te Ir Es N p Ta S n R b S r I Pt Fm n=5 U Hf In Xe Au Md Pa La Hg No Th Lr Ns Mt Sq Bi Po 110 Ha Pb Cs Ba At 111 n=6 Rf Ti Rn 112 Ac 113
Fm
Ta
Nb
S
Si Gd
Es
F Ne
Fe P
U
Ti
No Lr Db
Hf Zr
n=3
Cf
Md
Yb Lu
Sc
In
Bi
Er Tm
Ce
Sb Sn
Pm
Pr
Y
Dy Ho
Nd
La
Sr
K
Ca Ne Na Mg F He Li Be H O B N C AI p Ga Si
As
Th
Ro
Cs
Mn Cr
Gd Tb Eu
Sm
Be B
Am Np
He O
116 117 115 Fr Ra 118 114 119 120 121
n=8
Mt
–m –s
+s
Figure 5.46 Dr. Benfey’s periodic table
+m
n
s
p
d
f
Figure 5.47 The physicist’s periodic table
Learning Checkpoint 1. Give the number of valence electrons in an atom of each of the following elements. (a) hydrogen
(b) aluminum
(c) carbon
(d) oxygen
(e) chlorine
2. For each of the following groups of elements, give the number or numbers of valence electrons in the atoms. (a) Group 1
(b) Group 2
(c) Group 15
(d) Group 18
3. (a) What is similar about the valence electrons for atoms of elements in Period 2? (b) What is similar about the valence electrons for atoms of elements in Period 3? 4. At room temperature, oxygen is a colourless gas and sulphur is a yellow solid. Why are they in the same group in the periodic table?
The periodic table organizes elements by patterns in properties and atomic structure.
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STSE Science, Technology, Society, and the Environment
Working with Toxic Elements In the 18th and 19th centuries, mercury was used in hat making. The mercury produced toxic vapours, which caused symptoms of mercury poisoning in the hat makers and in people who wore the hats. Mercury poisoning could impair vision, speech, hearing, or balance as well as cause mood swings and memory loss. The “Mad Hatter” from Lewis Carroll’s classic fantasy books about Alice in Wonderland was a cartoon version of a hatter (hat maker) affected by mercury poisoning. Today, laws restrict how mercury can be used. Other people who work with toxic elements include scientists who study radioactive elements, painters, and pottery makers. Some of the metals that give paints and pottery glazes their bright colours include toxic cobalt, lead, and cadmium.
1. In order to protect the health of workers, how could workplaces limit the use of toxic elements? 2. What types of restrictions would you consider for artists working with toxic elements in their own homes? What questions would you need to answer in order to write a set of guidelines for artists? 3. What steps can people take to work safely with toxic elements? 4. If removing toxic elements from Earth’s surface will contaminate the environment, should we do this? What restrictions, if any, would you place on mining for toxic elements? Justify your response.
B17 Quick Lab Drawing Bohr Diagrams In this activity, you will practise drawing Bohr diagrams of atoms and ions of different elements.
Purpose To practise drawing Bohr diagrams of atoms and ions
Materials & Equipment • a copy of the periodic table
4. Look up the charge on a lithium ion in a periodic table. Draw a Bohr diagram of a lithium ion. 5. Find sodium on the periodic table. Draw a Bohr diagram of a sodium atom.
Questions
Procedure
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3. Find lithium on the periodic table. Begin a second Bohr diagram. Write down the number of protons in the nucleus of a lithium atom, and draw the energy shells and electrons in each shell.
1. Find hydrogen on the periodic table. Begin a Bohr diagram of a hydrogen atom by writing “1p” to show that there is one proton in its nucleus. Draw a circle to represent the nucleus.
6. How many protons and electrons would be shown in a Bohr diagram of a helium atom?
2. Draw the energy shell around the nucleus as well as the valence electron.
8. Describe the similarities and differences among the energy shells in your Bohr diagrams for lithium and sodium.
UNIT B
Atoms, Elements, and Compounds
7. How is a Bohr diagram of a lithium atom different from a Bohr diagram of a lithium ion?
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CASE STUDY
B18
SKILLS YOU WILL USE
STSE Decision-Making Analysis
Skills References 4, 7
Heavy Metals in Fish
Evaluating reliability of data and information Using appropriate formats to communicate results
Issue Due to environmental pollution, the concentration of heavy metals in fish is on the rise. For people who eat a lot of fish, heavy metal contamination is a serious concern.
Background Information Many metals are necessary for human health. For example, iron is so important in the diet that some people need to take iron supplements. However, the heavy metals, including cadmium, mercury, and lead, are toxic. Heavy metal pollution results mainly from industrial processes, such as refining ores, burning fuel, and using nuclear energy. Heavy metals are also used in some types of batteries and computer equipment. When these pollutants are released into the air, they come back down with precipitation. In this way, and from water washing over contaminated landfills, heavy metals get into the water supply. Once in the water, they build up in the food chain. Fish near the top of the aquatic food chain often contain high amounts of heavy metals. Therefore, Health Canada and the government of Ontario have set guidelines about how much of different types of fish people should eat to avoid heavy metal poisoning. Pregnant women in particular are cautioned not to eat too much of certain types of fish, as heavy metals can harm the fetus. It is not always clear how much humans are affected by heavy metals in their food. However, scientists have seen an effect on contaminated organisms. Fish stop functioning normally. They seem to be unaware of their natural predators and do not use their ingrained escape-and-evade techniques. Heavy metal contamination also seems to affect their sense of smell. Some fish have trouble recognizing their own offspring, and instead of protecting them, they eat them. This behaviour could have a serious impact on the numbers of some types of fish in the future — as well as the other organisms in their environment.
Your task is to work with a partner find out who may be at risk from heavy metals and why. Determine what, if anything, the government should do to protect people from this risk. Use a graphic organizer to keep track of information. After you complete your research, you will present your findings in a poster, an interview, or another form of media.
Analyze and Evaluate 1. ScienceSource Gather information to help you answer the questions below and complete your overall task. 2. Why might Aboriginal peoples and people in remote communities feel the effects of heavy metal contamination of fish more than most groups in Canada? 3. (a) What other cultures rely heavily on fish in their diet? (b) Should people from these cultures also have concerns about heavy metal poisoning? Explain. 4. What can be done to protect people from heavy metal poisoning from their food? 5. Suppose you go fishing at a pond contaminated with mercury and catch a minnow (a fish at the bottom of the food chain) and a large trout (a fish at the top of the food chain, which eats other fish). Which fish would have a higher concentration of mercury in its body? Why? 6. Create an informational poster, a question-andanswer interview that you and your partner can share with the class, or another form of media, giving the three best ways to protect people from heavy metal poisoning.
Skill Practice 7. In your research, did a certain type of graphic organizer seem more helpful than another? Why?
The periodic table organizes elements by patterns in properties and atomic structure.
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B19 Inquiry Activity
Skills References 2, 8, 9
Building a Periodic Table Scientists use models to explain things we cannot see or to display patterns in data.
Question How can a model represent the patterns in the periodic table?
Materials & Equipment • 24 assorted nuts and bolts in a bag • extra nut or bolt • large sheets of paper • ruler • balance • element cards • graph paper
Procedure Part 1 — Classifying Items Individually 1. Examine the 24 nuts and bolts from the bag provided by your teacher. 2. Your bag originally contained 25 nuts and bolts, but your teacher removed one of them. Identify whether a nut or a bolt was removed, and describe the missing piece in as much detail as possible. 3. Share your classification ideas for the missing object with another group. How were your ideas similar? How were they different? 4. Revise your classification or description based on your discussion. 5. Collect the missing nut or bolt from your teacher. How close was your description to the missing object? Revise your classification or description based on this new information.
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Atoms, Elements, and Compounds
Gathering, organizing, and recording relevant data from inquiries Interpreting data/information to identify patterns or relationships
Part 2 — Classifying Items Collectively 6. On a large sheet of paper, make a grid with five equal-size columns and five equal-size rows. Make sure the boxes are large enough to hold the largest nut or bolt. Number the boxes 1 to 25, starting on the top left at number 1 and working across the row from left to right. The first box in the second row should be number 6. 7. Place the smallest bolt at number 1 and the largest nut at number 25, as shown below in Figures 5.48 and 5.49. Now organize the rest of the nuts and bolts on the grid. 1 smallest bolt
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25 largest nut
Figure 5.48 Grid for organizing nuts and bolts
8. Follow your teacher’s instructions to measure either the length and width or mass of each nut and bolt. Record the measurements on your grid.
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B19 Inquiry Activity
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(continued)
Part 3 — Classifying Elements 9. Collect an element card from your teacher. 10. Compare the properties on your card to those of your classmates. Find classmates with cards that have similar element properties. You will form a group with these students.
16. Use your data on the elements from Part 3 to make a graph of atomic mass versus atomic number. 17. Record any patterns you notice in this graph. 18. Compare the two graphs you made. What similarities do you see?
11. Make a list of the properties your group’s elements all share. Share the list with your teacher or class. Once your teacher confirms your list, you will be given a group number.
19. Examine the periodic table on page 191. Compare your arrangement of elements with the arrangement of elements in the periodic table. Describe their similarities and their differences.
12. Arrange all of your group’s element cards in order of atomic mass.
Skill Practice
13. Make another five-by-five grid, as you did in step 6. Complete it, using the order of the elements in the class. Include the atomic mass for each element in your grid. Write the element’s group number at the top of the grid.
20. How many electrons do the following elements have? (a) carbon (b) chlorine (c) magnesium (d) neon
Analyzing and Interpreting 14. Use your data from Part 2 to graph a nut or bolt number versus nut or bolt size (length, width, or mass). (The number of each nut or bolt is the number of the box in the grid where the nut or bolt was placed.)
Forming Conclusions 21. Return to the guiding question for this inquiry activity. Examine the periodic table on page 191. Based on your data and experiences, answer the question.
15. Record any patterns you notice in this graph.
Figure 5.49 Arranging the nuts and bolts
Figure 5.50 The element cards
The periodic table organizes elements by patterns in properties and atomic structure.
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CHECK and REFLECT 10. Use the Bohr diagram below to answer the questions that follow.
Key Concept Review 1. Refer to a periodic table to answer the following questions. (a) What is the chemical symbol for sodium? (b) What element has the symbol Hg?
Question 10
(c) What element sits directly below carbon in the periodic table? (d) Which element has atoms with a greater mass: lithium or potassium? 2. Name four properties that Dmitri Mendeleev used as criteria for organizing the elements. 3. Name two groups on the periodic table that include elements that conduct heat and electricity. 4. What is the special name for Group 17 on the periodic table? 5. Using hydrogen as an example, explain the difference between atomic number and atomic mass. 6. What happens to an atom if it loses a valence electron? 7. Which of the following atoms typically form negative ions? (a) F
(b) Li
(c) Ne
(d) S
(e) Al
(a) What element is shown? (b) How many electrons does this atom have? (c) How many protons does this atom have? (d) What group in the periodic table does this element belong to? 11. In one of Dmitri Mendeleev’s first periodic tables, he left two question marks between zinc and arsenic. (a) Why did he predict that eventually someone would discover elements to fit in the spaces he left in his periodic table? (b) What were these two missing elements named when they were later discovered? 12. Suppose a sample of a metal has a low melting point and reacts easily with water. What group does the element belong to? 13. Would the latest elements to be discovered have heavier atoms or lighter atoms than the other elements? Explain.
(f) Be
Reflection Connect Your Understanding 8. If something occurs periodically — every Monday, for instance — it can be said to occur in a pattern. How do you think the periodic table got its name?
14. How has your understanding of the term “metals” changed since completing this section? Write a definition for “metal,” and list examples of metals with different properties.
9. How do chemical symbols help scientists from different countries communicate? Why is this important?
15. List three ways that you can use the periodic table in your studies that you did not know about before completing this section. For more questions, go to ScienceSource.
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Atoms, Elements, and Compounds
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S C I E N Ceverywhere E
Diamonds: Responsible Mining and Production
In the 1990s, geologists working in northern Canada made an exciting discovery — several diamond deposits! With the opening of the Ekati diamond mine, 300 km northeast of Yellowknife, Canada became a diamond-producing nation. Canada soon became the world’s third-largest producer of gemstone-quality diamonds, behind only Botswana and Russia. For some remote Aboriginal communities, the diamond mines in the Northwest Territories and Nunavut have become an important source of income. Shown here is the Diavik diamond mine of the Northwest Territories.
This raw diamond must be processed before it can be used. Diamond mining and processing raise some important ethical, economical, and political issues. Diamond-processing facilities produce waste heat and substances that can harm the environment. Mines, too, have an environmental impact. Mines can interrupt the path of migrating animals. Sometimes, lakes will be drained in order to reach underwater diamond deposits. Aboriginal communities that hunt or fish for food are concerned about the impact of the diamond industry on the local environment.
Diamonds are valued as gems for their clarity and sparkle and because they can be cut into detailed designs, as in the diamond shown here. But diamonds have many other uses than as gems. The hardest natural substance on Earth, diamond resists wear, chemical change, and temperature extremes. Diamond is hard enough to cut many types of rock and so is often used to make specialized saw blades, drill bits, or grinding wheels. In medical and laboratory equipment, thin, clear diamond membranes cover the openings where laser beams or X-rays pass through.
The periodic table organizes elements by patterns in element properties and atomic structure.
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CHAPTER REVIEW
ACHIEVEMENT CHART CATEGORIES t Thinking and investigation k Knowledge and understanding c Communication
11. Examine the photograph of mercury at room temperature and answer the questions that follow.
a Application
Key Concept Review 1. What is the smallest amount of an element that can exist? k 2. Compare and contrast the charge, the location in an atom, and the relative mass of an electron with those of a neutron. k
Question 11
3. Beginning with the innermost shell, list the maximum number of electrons that an atom can have in its first three shells. k
(a) What properties of mercury would have led early chemists to classify it as a metal? Explain. c
4. List three halogens, and describe a property that they all share. k
(b) What property makes mercury different from most other metals? k
5. (a) What is the Latin name for lead? (b) What is the symbol for lead?
12. (a) List two properties that generally increase, beginning with the first element in the periodic table through to the 100th element and beyond. k
k
k
6. Name four non-metals that are solids at room temperature. k 7. What is the difference between an insulator and a conductor? Give an example of an element that is a weak conductor. k 8. (a) If an atom has 43 protons, what element is it? k (b) If an atom contains 66 electrons, what element is it? k 9. Use Figure 5.45 on page 198 to answer the following questions. (a) How many shells containing electrons does a potassium atom have? k
UNIT B
Atoms, Elements, and Compounds
13. The symbol for gold is Au, based on the Latin term aurum. Is there any reason why Go could not have been chosen as the symbol for gold? t 14. How did Dmitri Mendeleev use the estimated mass of atoms to help him to order the elements in a table? a
(b) Name three uses for the element that you listed in (a). a
(c) Name the element that has a full valence shell of two electrons. k
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15. (a) What element is diamond made of? What is the name of another pure form of this element? k
(b) How many valence electrons does a calcium atom have? k
10. Draw a Bohr diagram of a chlorine atom.
(b) Are there any exceptions to the pattern described in (a)? Explain. k
c
(c) What are some environmental issues related to using the element that you listed in (a)? a
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16. Mendeleev believed that one of the gaps in his first periodic table would eventually be filled by an element he called eka-silicon. Such an element had not yet been discovered. In 1871, he predicted what the properties of this undiscovered element would be. In 1886, he was found to be correct. Use the information in the figure and table below to answer the following questions. 14
Si
atomic mass 31
⫹4 ⫹2
28.1 ⫹3
Ga
32
⫹4 ⫹2
“Eka-silicon”
69.7
33
? 50
Sn
⫺3 ⫹5
As
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17. In the early 1800s, just over 30 elements had been identified. Today, there are more than 100 known elements. Why might there have been such a rapid increase in the discovery of elements? t 18. In the last 50 years, many new elements have been made in laboratories. How do the numbers of subatomic particles in atoms of these elements compare to the numbers in a common element such as iron? a 19. Create a warning poster or public service announcement about an element that can cause harm if improperly used or stored. c
74.9 ⫹2 ⫹4
Reflection
118.7
20. Now that you have studied atomic theory, how has your understanding of the composition of matter changed? c
Question 16
Properties of Selected Elements Atomic Mass (amu)
Element
Colour
silicon
steel grey
28.09
gallium
grey-black
69.72
eka-silicon
?
arsenic
silver to grey-black, sometimes yellow
tin
grey-white
21. Briefly describe three ways in which pure elements are used that you did not know about before reading this chapter. c
? 74.92 118.71
(a) Which of the four elements in the figure would you use to predict the properties of Mendeleev’s new element? Explain your reasoning. t (b) Approximately what atomic mass would you predict for eka-silicon? t (c) What colour would you predict ekasilicon to be? t (d) What do we now call eka-silicon?
t
(e) Mendeleev did not predict an atomic number for eka-silicon. Why not? a
After Reading Reflect and Evaluate Summarize the “fix-up” strategies you learned to use in this chapter. Working with a partner, create a tips sheet for other readers about fixing up understanding when they are reading. Add other strategies that you have used successfully to understand what you read.
Unit Task Link Use your knowledge of the properties of the elements to explain why pure elements would not be used as toothpaste ingredients. Identify elements that you would not want to add to toothpaste, even if these elements were in the form of compounds.
The periodic table organizes elements by patterns in properties and atomic structure.
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Elements combine to form ionic compounds and molecular compounds.
UNIT B
Atoms, Elements, and Compounds
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Home Shown here is a mixture of two ordinary compounds: a component of bath salts called magnesium sulphate and a common pesticide called copper(II) sulphate. The crystals are magnified about 100 times.
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Skills You Will Use In this chapter, you will: • conduct inquiries into the physical and chemical properties of common compounds • build models of simple molecules • plan and conduct an inquiry into the properties of common household and laboratory substances
Concepts You Will Learn In this chapter, you will: • distinguish between elements and compounds and describe some common compounds • assess social, environmental, and economic impacts of the use of elements and compounds • identify, name, and write the formulas for some types of compounds
Why It Is Important Most substances on Earth do not exist in the form of pure elements. The combination of elements to form compounds results in new substances with distinct properties. The water you drink, your clothes, your hair, and the desk you sit at are made of chemical compounds. Understanding the properties of different compounds will help you to make decisions that take into account their uses and potential hazards.
Before Writing What's My Topic? Good writers let their readers know very quickly the topic of their writing. Check the opening sentences of the paragraphs in section 6.1. How many of them state the topic clearly and up front?
Key Terms • chemical bond • chemical formula • ionic bond • ionic compound • molecular compound • molecule
Elements combine to form ionic compounds and molecular compounds.
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How Compounds Form
Here is a summary of what you will learn in this section: • Compounds are composed of two or more elements that combine in a specific ratio. • Ionic compounds form when metallic and non-metallic elements combine chemically. • Molecular compounds form when non-metallic elements combine chemically.
Figure 6.1 Hydrogen peroxide is a chemical compound that may be used to create highlights in hair.
Hydrogen peroxide Strong oxidizer. Keep out of contact with finely divided reducing agents and metals. Can only be stored for prolonged periods of time if stabilized with a little phosphoric acid and stored in amber bottles.
Stability:
3
CORROSIVE
Storage: OXIDIZER
7
0 Flammability
4
5
Health
Reactivity
Chemicals Everywhere We live in a chemical world. Every kind of substance that you can think of is made of a type of chemical or mixture of chemicals. Water is a chemical, and the air you breathe is a mixture of chemicals. The ink in your pen, hair dyes and bleaches, the lead-lined cover that protects you during a dental X-ray, and life-saving medicines are all made of chemicals, too (Figure 6.1). A quick look around your home will reveal an amazing variety of chemicals in your cupboards and on your shelves. In the bathroom, you will find water, soap, shampoo, deodorant, and toothpaste — all chemicals. In the storage area, you might find cleaning products, such as ammonia and bleach, and perhaps painting and gardening products. In your kitchen, you might find table salt, baking soda, and baking powder. Each of these products contains one or more chemical compounds.
Special
Figure 6.2 People using a chemical such as hydrogen peroxide in their workplace must, by law, be trained in the meaning of all the safety symbols on the label.
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Compounds A compound is a pure substance made up of two or more elements that are chemically combined. For example, water is a compound consisting of hydrogen and oxygen. Hydrogen peroxide is also a
Atoms, Elements, and Compounds
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compound of hydrogen and oxygen but with completely different properties than water (Figure 6.2 on the previous page). Some of the differences between water and hydrogen peroxide are listed in Table 6.1. Hydrogen peroxide is a blue liquid that can dissolve in water to form a solution, which is commonly available in pharmacies. In certain concentrations, it can be used on skin to kill bacteria or in hair as a bleaching agent. All compounds have properties that make them potentially useful as well as hazardous. If a highly concentrated solution of hydrogen peroxide gets on the skin, it will cause a chemical burn. Even water, if consumed in huge volumes, can make a person sick. Understanding the properties of compounds gives us the knowledge to make use of compounds safely and responsibly.
Table 6.1 Properties of Water and Hydrogen Peroxide Water (H2O) • • • •
colourless liquid boils at 100°C stable in strong sunlight dissolves the chemical potassium iodide • does not bleach pigments Hydrogen peroxide (H2O2) • • • •
blue liquid boils at 150.2°C breaks down in light reacts with the chemical potassium iodide • strong bleaching agent
B20 Quick Lab Water and Hydrogen Peroxide (Teacher Demonstration) Purpose To observe properties of water and hydrogen peroxide
3. Observe as your teacher pours water into a beaker and then stirs in some potassium iodide crystals.
Materials & Equipment • blue litmus paper • two 400-mL beakers • water • hydrogen peroxide solution
• potassium iodide crystals • 250-mL graduated cylinder • basin
• cobalt chloride paper
• dish soap
• scoopula
• matches
• stirring rod
• wooden splint
2. Your teacher will dip one piece of cobalt chloride paper into water and another into hydrogen peroxide solution. Observe the cobalt chloride paper.
4. Your teacher will place the graduated cylinder in the basin and then pour 20 mL of hydrogen peroxide solution and 3 drops of dish soap into the graduated cylinder. Observe as your teacher adds a small scoop of potassium iodide crystals. 5. Step 4 will produce bubbles of gas. Observe as your teacher places a glowing splint into the gas.
Question CAUTION: Hydrogen peroxide is corrosive to skin. Potassium iodide will stain skin and clothing.
6. Describe three differences in the properties of water and hydrogen peroxide that you observed.
Procedure 1. Your teacher will dip one piece of blue litmus paper into water and another into hydrogen peroxide solution. Observe the litmus paper.
Elements combine to form ionic compounds and molecular compounds.
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Two Types of Compounds
During Writing Staying on Topic Writers support their topic sentence by adding sentences with details that relate to the topic. Each new sentence seems to flow logically from the words and ideas in the previous one. Notice how the paragraph about salt seems unified because all the sentences support our understanding of the topic.
Suggested Activity • B21 Quick Lab on page 215
A small change in the way the atoms combine can make a big difference in the chemical and physical properties of compounds. Although millions of compounds have been discovered, almost all of them can be classified as one of two types: ionic or molecular.
Ionic Compounds Common table salt is familiar to most people as a white substance composed of tiny crystals. As discussed in Chapter 5, sodium chloride forms when a very reactive metal — sodium — is placed in a container with a poisonous, yellow-green non-metal — chlorine gas (Figure 6.3). When these two chemical elements are combined, the sodium metal explodes in a bright orange flame. As the sodium burns, a white, coarse-grained powder is produced. This new substance has properties that are very different from the properties of sodium and chlorine. The substance is table salt, or sodium chloride (NaCl). Sodium chloride is called an ionic compound. Ionic compounds are pure substances usually consisting of at least one metal and one non-metal. Most ionic compounds share the following properties: • have high melting points • form crystals, which are very regular arrangements of particles • dissolve in water to form solutions that conduct electricity
(a)
(b)
(c)
Figure 6.3 Sodium (a), is a metal. Sodium combines with chlorine gas in a violent reaction (b). The compound that forms is sodium chloride, NaCl (c).
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All ionic compounds are solids at room temperature. In fact, table salt will not melt until it is heated to 800°C. When sodium chloride is dissolved in water or melted, it will conduct electricity. Investigations of this property led to the study of electrochemical cells, which can convert chemical energy into electricity.
W O R D S M AT T E R
The word “ion” comes from a Greek word meaning to go or to wander.
Forming Ionic Compounds While combining, each atom changes into an ion. Ions form when one or more electrons move from a metal atom over to a nonmetal atom. This process is shown in Figure 6.4. 1+
Na
1-
Na+
Cl
Cl-
Figure 6.4 A sodium atom becomes a positive ion when it loses an electron to chlorine. By gaining an electron, chlorine becomes chloride, a negative ion. Together, they form an ionic compound.
As the figure shows, a sodium atom loses an electron by giving it to a chlorine atom. This produces a positive sodium ion and a negative chloride ion. Positive and negative ions attract each other, so in an ionic compound, all the positive ions are attracted to all the negative ions. A connection between atoms or ions is known as a bond. The attractions between ions are called ionic bonds. The ionic bonds cause the ions to group together in an alternating pattern called a crystal arrangement (Figure 6.5).
Na+
CI-
Figure 6.5 The crystals in this table salt are held together by ionic bonds.
Learning Checkpoint 1. What is the main difference between a compound and an element? 2. What two kinds of elements join together to form an ionic compound? 3. What is an ionic bond? 4. How must atoms change so that they can join to form an ionic compound? 5. What physical property or properties could you use to identify an ionic compound?
Elements combine to form ionic compounds and molecular compounds.
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Suggested Activity • B23 Quick Lab on page 216
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Molecular Compounds When non-metals combine, a pure substance called a molecular compound is formed. In molecular compounds, the atoms share electrons to form small groups, called molecules. Most molecular compounds share the following properties: • can be solids, liquids, or gases at room temperature • usually good insulators but poor conductors of electricity • have relatively low boiling points
Take It Further Hydrogen peroxide is considered to be a more environmentally friendly alternative to chlorine bleaches. It is currently used in many paper-processing facilities to produce white paper, instead of using the more harmful chlorine. The chemical activity of the hydrogen peroxide changes the colour of the fibre in paper to white. With a partner, create a pamphlet to advertise one of the many other uses of hydrogen peroxide. Begin your research at ScienceSource.
(a)
Examples of molecular compounds include table sugar, hydrogen peroxide, and water. How can the same two elements (hydrogen and oxygen) combine to form compounds as different as water and hydrogen peroxide? Water is made from joining two atoms of hydrogen to one atom of oxygen. This forms a water molecule, and this is the smallest possible amount of water that can exist. We often represent this as H2O, where the subscript “2” indicates that two atoms of hydrogen are included. Hydrogen peroxide is formed when four atoms — two each of hydrogen and oxygen — join to form a single molecule. This molecule is represented as H2O2. There are a number of ways to represent the atoms in a molecule. In every representation of water in Figure 6.6, two hydrogen atoms are connected to an oxygen atom in the middle. The Bohr diagram of water shows that each hydrogen atom shares a pair of electrons with the oxygen atom (a). In the balland-stick model, a stick represents each bond between atoms (b). In the third diagram, the areas in which the atoms overlap represents the connections that holds them together (c).
(b)
(c)
Figure 6.6 Representations of a water molecule: (a) a Bohr diagram; (b) a ball-and-stick model, in which the sticks represent connections between atoms; (c) a diagram with overlap between atoms to show how they are connected
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B21 Quick Lab Salt and Sugar Adding sugar to your tea, or salt to your soup, not only changes the way your food tastes, it will dissolve to form a solution. That solution may or may not be able to conduct an electric current.
4. Use a clean spoon to add one small spoonful of sodium chloride to the third beaker. Use the spoon to stir until the sodium chloride is dissolved.
Purpose
5. When your solutions are prepared, use a batteryoperated conductivity tester to determine whether any of the three samples conduct electricity.
To compare the conductivity of different compounds: sodium chloride (table salt) and sucrose (table sugar)
Materials & Equipment • three 100-mL beakers
• sucrose (table sugar)
• marker
• sodium chloride (table salt)
• tap water • 2 small spoons
• battery-operated conductivity tester
Questions 6. Sodium chloride and sucrose are both shiny white crystals, and both dissolve in water. What evidence shows which of these crystals is an ionic compound? 7. Suggest why it is often unsafe to have high voltage electricity near water. Refer to the results of your experiment in your answer.
Procedure 1. Use the marker to label three 100-mL beakers as water, sucrose, and sodium chloride. 2. Fill each beaker with 50 mL of tap water. Set the beaker labelled “water” aside. 3. Add one small spoonful of sucrose to the second beaker. Use the spoon to stir until the sucrose is dissolved.
Figure 6.7 A conductivity tester
B22 Skill Builder Activity Molecular Model Kits In this activity, you will examine the components of a molecular model kit to prepare you to build simple models. In the kit, balls represent atoms and sticks represent connections between the atoms. Carbon is represented by a black ball, oxygen by a red ball, chlorine by a green ball, and hydrogen by a white ball. The number of holes in each ball represents the number of connections the atom can make with other atoms.
1. Examine the model atoms of carbon, oxygen, chlorine, and hydrogen. Build as many connections as you can between the different model atoms. 2. Describe what you observe about the different models you built.
Elements combine to form ionic compounds and molecular compounds.
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DI Key Activity
B23 Quick Lab Building Molecular Models Chemists use models to gain information about the shape of a molecule. The shape of a molecule is a good predictor of its properties. In this activity, you will build ball-and-stick models of simple molecules using a molecular model kit.
Purpose To represent the molecules of some common substances
Materials & Equipment • molecular model kit
2. There are two guidelines that you must follow when building molecular models: • Each molecule is complete when all the balls are connected in such a way that all the holes are filled and every connector ends in a hole. • It is possible in some cases for more than one connection to exist between the same two atoms. 3. For each of the following, build the model and then make a sketch of it. (a) H2O (water) (b) H2 (hydrogen gas) (c) O2 (oxygen gas) (d) CH4 (methane, also called natural gas) (e) CH2Cl2 (a solvent used as a degreaser) (f) C2H4 (starter material for making polyethylene plastic) (g) C3H8 (propane, a camp fuel) (h) HCl (hydrogen chloride, present in stomach acids) (i) H2O2 (hydrogen peroxide) (j) CO2 (carbon dioxide)
Figure 6.8 A ball-and-stick model of glucose, a type of sugar. Glucose can be straight, as shown here, or can twist into a ring structure.
4. The following molecules can each be assembled in two different ways. Build and sketch each: (a) C2H60 (b) C3H7Cl
Procedure
Questions
1. Work in a small group to use the molecular model kit. Your teacher will provide specific information about how to use your particular kit.
5. Identify the two molecules that represented elements rather than compounds. 6. How do the positions of the holes in each kind of model atom produce a molecule that has a three-dimensional shape?
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CHECK and REFLECT
Key Concept Review 1. What is the difference between a compound and a mixture?
9. Use the diagram below to answer the following questions. 2+
2. What are the two major types of compounds? How do the bonds differ in each type?
2-
3. Give an example of a molecular compound. 4. Give an example of a substance held together by ionic bonds.
Question 9
5. What types of elements join to form molecular compounds? Name three such elements. 6. (a) What is the total number of atoms in a water molecule?
7. How is it possible for two different compounds, such as water and hydrogen peroxide, to both be made of the same two elements? 8. Examine the following table of properties for two unknown compounds. Which is most likely an ionic compound and which is most likely a molecular compound? Explain your reasoning. Properties of Unknown Compounds Compound Y
Boiling point (°C)
82
1550
Melting point (°C)
−90
455
Conductivity in solution
poor
good
(c) Which elements does this compound contain?
11. Is it possible to wash dishes without using chemicals? Explain.
Connect Your Understanding
Compound X
(b) What type of compound is shown?
10. Describe how a salt crystal holds together.
(b) How many elements are in a water molecule?
Property
(a) What type of diagram is shown?
12. Can compounds have different properties than their elements have? Explain, using an example.
Reflection 13. Describe three types of models used in this section to represent compounds. Which model did you find most useful and why? 14. Name two compounds that you were familiar with before reading this section. Now that you have completed this section, what have you learned about these two compounds? For more questions, go to ScienceSource.
Elements combine to form ionic compounds and molecular compounds.
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Names and Formulas of Common Compounds
Here is a summary of what you will learn in this section: • Ionic and molecular compounds have many uses in our everyday lives. • Compounds can be represented by chemical formulas or chemical names. • You can use a chemical formula to write the name for a compound. You can also use the name of a compound to write its formula. Figure 6.9 The shells of sea animals and land snails are made up of the compound calcium carbonate.
Common Names and Chemical Names Have you ever drawn a picture with pastel chalks? Some classrooms use chalk for writing on a chalkboard. People sometimes use another product that contains chalk — antacids. Antacids are taken to relieve indigestion. The chalk in antacids is mixed with sweeteners and flavours so that it tastes better. However, do not eat drawing chalk for your upset stomach, because these types of chalk and the chalk in antacids are not the same chemical. Drawing chalk is mainly calcium sulphate, while the antacid chalk is calcium carbonate (Figure 6.10). Calcium carbonate is also the main compound in sea shells, snail shells, and eggshells (Figure 6.9). The different meanings of the term “chalk” show how confusing it can be to inaccurately name compounds. This example also shows the importance of using names that provide information about the chemical composition of a substance. The term “chalk” gives no hint as to what elements are present in either compound.
Naming Salts Figure 6.10 Chalkboard chalk is composed of calcium sulphate. Antacids and some calcium supplements contain calcium carbonate.
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Another example of a common name that can cause confusion is the word “salt.” We use the word “salt” as a common term for table salt. In chemistry, salt does not refer to a particular pure substance. In fact, it refers to the type of ionic compound. Salts have similarities in how they are formed and in their properties.
Atoms, Elements, and Compounds
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However, the term “salt” does not indicate which specific elements are found within a compound. In the language of chemistry, table salt is called sodium chloride. Sodium chloride is not the same as the salt used on our roads in winter to melt ice. Road salt contains calcium chloride. Calcium chloride is somewhat less harmful to plants than sodium chloride is. Figure 6.11 shows a variety of ionic compounds, all of which are salts. Every compound has a chemical name and formula. The chemical formula identifies which elements, and how much of each, are in the compound. For example, sodium chloride’s formula is NaCl. Baking soda’s chemical name is sodium hydrogen carbonate, and its chemical formula is NaHCO3.
Figure 6.11 Clockwise from the lower left, the salts shown here are sodium chloride, iron(II) sulphate, iron(III) sulphate, copper(II) sulphate, and copper(II) carbonate.
B24 Quick Lab Naming Compounds Modern naming systems try to reveal a lot about a compound. Work with a partner to uncover as much information as possible about each compound.
Purpose
Questions 3. Locate where each element named in step 1 occurs in the periodic table, and suggest answers to the following.
To interpret chemical names for compounds
(a) What two different kinds of elements are present in this type of compound?
Procedure
(b) What determines the order in which each element name occurs in the compound name?
1. Using the periodic table on page 191, work with a partner and try to figure out from each name what elements are present in the following compounds. Each compound contains two elements only. (a) sodium fluoride (prevents tooth decay) (b) zinc oxide (present in mineral supplements) (c) potassium chloride (sodium-free salt substitute) (d) lithium nitride (used in some batteries) (e) iron(III) oxide (present in common rust) 2. Examine each formula below, and determine what elements are present in each compound. (a) CuI (a mineral present in copper ore) (b) NaI (dietary supplement added to table salt) (c) CaSO4 (drawing chalk) (d) CaCO3 (main component in eggshells)
(c) Not all element names that appear in the compound names are exactly the same as they appear on the periodic table. What pattern(s) are there in how these names are changed? 4. In step 2, what patterns can you find in the way the chemical formulas of these compounds are written? 5. Chemists use both chemical names and chemical formulas. Suggest situations where one might be more useful than the other. 6. Your teacher will give you the ingredients list from a food product, medicine, or household product such as shampoo or toothpaste. Examine the list and discuss what kind of chemical information you are able to determine about the product from your analysis of the product label.
(e) Mg(OH)2 (milk of magnesia, an antacid) Elements combine to form ionic compounds and molecular compounds.
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Ion Charges Each of the elements that commonly form ionic compounds has an entry in the periodic table showing what ion charge it can have. Table 6.2 shows some examples of ions and their charges, which were taken from the periodic table. • The ion notation contains the symbol for the element and a superscript number and + or – sign at the top right. For example, the lithium ion has a 1+ charge, which is shown as Li+. • Iron, copper, and lead can form an ion in more than one way. A Roman numeral is included in the ion’s name to show the ion’s charge. For example, the name of Fe2+ is iron(II), which is read “iron two”. The “two” refers to the charge. Similarly, iron(III) is read “iron three” and names the Fe3+ ion. Table 6.2 shows the connection between the ion charge and the Roman numeral. • The name of non-metal ions is formed by taking the element name and changing the ending so that it includes the suffix “– ide.” For example, the element oxygen produces the ion O2⫺, which is called oxide. Table 6.2 Ion Charges Element
Ion Charge
Ion Notation
Ion Name
hydrogen
1+
H+
hydrogen
lithium
1+
Li+
lithium
nitrogen
3–
N3–
nitride
oxygen
2–
O2–
oxide
magnesium
2+
Mg2+
magnesium
aluminum
3+
Al3+
aluminum
iron
2+ or 3+
Fe2+ or Fe3+
iron(II) or iron(III)
copper
1+ or 2+
Cu+ or Cu2+
copper(I) or copper(II)
lead
2+ or 4+
Pb2+ or Pb4+
lead(II) or lead(IV)
Learning Checkpoint 1. What is a salt? Give an example. 2. Explain why using standard chemical names for compounds would be important when working in a laboratory. 3. Refer to the periodic table and write all possible ion charges, ion notations, and ion names for ions formed by the following elements. (a) calcium 220
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(b) chlorine
(c) phosphorus
(d) gold
(e) tin
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Naming Ionic Compounds
W O R D S M AT T E R
The following rules explain how to name ionic compounds based on a given chemical formula. 1. Name the metal ion first. The name of the metal ion is the same as the element name. For example, in NaCl, the name of the Na+ ion is sodium. If the element can form an ion in more than one way, include a Roman numeral to indicate the charge.
Sodium chloride is essential in the diet, making it a very valuable compound. Armed troops once guarded the salt supplies of ancient Rome along the Via Salarium (Salt Road) and were paid in bags of salt. In time, their payment changed from salt to money and became known as salarium, the origin of the modern English word “salary.”
2. Name the non-metal ion second. When a non-metal becomes a negative ion, the ending of its name changes to “ide.” For example, a chlorine atom (Cl) gains an electron to become a chloride ion (Cl–). 3. The name for an ionic compound is a combination of the ion names of the elements. The name of NaCl is, therefore, sodium chloride. Name of metal sodium
Name of non-metal + ide chloride
The formulas of ionic compounds often contain numbers, called subscripts, such as the “3” in AuCl3. We will look at the meaning of subscripts on page 222. If the metal forms only one type of ion, the subscript can be ignored when determining the compound name. In the examples in Table 6.3, each formula is examined and the two ions present are identified. Table 6.3 Naming Ionic Compounds Formula
Positive Ion
Negative Ion
Name
MgO
Mg2+
O2–
magnesium oxide
BaF2
Ba2+
F–
barium fluoride
K3N
K+
N3–
potassium nitride
Example Problem 6.1
Practice Problems
Write the name of the ionic compound Ag2S.
Write the names of the following ionic compounds.
1. Name the metal ion: Ag forms only one type of ion (Ag+), so the name is silver.
1. NaF 2. KI
2. Name the non-metal ion: The atom is sulphur, so the ion is sulphide.
3. MgCl2
3. Combine the names: silver sulphide
5. Ca3P2
4. AlCl3
Elements combine to form ionic compounds and molecular compounds.
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Suggested Activity • B25 Quick Lab on page 227
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Multivalent Elements Some metals can form more than one type of ion. For example, iron has two stable ions: Fe2+ and Fe3+. Elements with more than one stable ion are called multivalent elements. Ionic compounds containing multivalent elements must have Roman numerals in their names to indicate which ion is forming that compound. The Roman numeral is written in brackets after the element to indicate the charge. For example, the compound name iron(III) oxide indicates that the Fe3+ ion forms that compound (Figure 6.12). You can find the Roman numeral to use in the name of a multivalent ion by using the subscripts in the compound’s formula. For example, in FeBr2, the subscript 2 after the Br is a guide to the iron ion’s charge. The positive and negative charges in an ionic compound must be equal. According to this rule, only an Fe2+ could pair up with two Br – to give the 1:2 ratio in the formula. FeBr2 is written out as iron(II) bromide. In FeBr3, only an Fe3+ could pair up with three Br– to give the 1:3 ratio in the formula. FeBr3 is written out as iron(III) bromide.
Figure 6.12 Rust contains iron(III) oxide, or Fe2O3. Rust is produced when iron corrodes.
Example Problem 6.2 Practice Problems
Write the names of the following ionic compounds. 1. FeCl3 2. PbO2 3. Ni2S3 4. CuF2 5. Cr2S3
Write the name of the ionic compound Cu3N. 1. Identify the ions that form the compound: Cu? and N3– 2. Use the charge of the non-metal ion and the rule that the total positive and negative charges in the formula must be equal. Three copper ions are present in the formula, so each must have a charge of 1+. 3. Name the metal ion: The ion has a 1+ charge, so the name is copper(I). 4. Name the non-metal ion: The name of the atom is nitrogen, so the ion is nitride. 5. Combine the names: copper(I) nitride
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Atoms, Elements, and Compounds
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Polyatomic Ions Sometimes, a group of atoms of different elements act as a single ion. This type of ion is called a polyatomic ion. Some examples of polyatomic ions are given in Table 6.4. For example, one atom of carbon and three atoms of oxygen form the polyatomic ion called carbonate, or CO32–. This ion is present in your teeth as well as in eggshells. In both cases, it is present with calcium ions (Ca2+) and forms the compound calcium carbonate (CaCO3). As with other ionic compounds, you can use the formula for an ionic compound with a polyatomic ion to write the compound’s name. First, look at the formula and identify and name the positive ion, which will be a metal ion. For example, NaOH contains the metal ion Na+, or sodium ion. The next step is to identify and name the polyatomic ion. In NaOH, the polyatomic ion is OH –, or hydroxide. You do not need to change the ending of a polyatomic ion’s name. The name of the compound NaOH is sodium hydroxide. In some cases, the formula uses brackets to help identify the polyatomic ion. Table 6.5 gives some hints for writing the names of ionic compounds with polyatomic ions.
Table 6.4 Common Polyatomic Ions Ion Symbol
Ion Name
OH–
hydroxide
HCO3–
hydrogen carbonate
SO42–
sulphate
CO32–
carbonate
PO43–
phosphate
W O R D S M AT T E R
The prefix “poly” comes from the Greek term polys, meaning many.
Table 6.5 Naming Ionic Compounds with Polyatomic Ions Formula
Positive Ion
Negative Ion
Name
Hint for writing name
Mg(OH)2
Mg2+
OH–
magnesium hydroxide
• The polyatomic ion is often found in brackets.
AlPO4
Al3+
PO43–
aluminum phosphate
• Brackets are not always used. • Everything after the metal ion is part of the polyatomic ion.
Example Problem 6.3
Practice Problems
Write the name of the ionic compound NaHCO3. 1. Name the metal ion: Na forms only one type of ion so the name is sodium.
(Na+),
Write the names of the following ionic compounds. 1. KOH
2. Identify the polyatomic ion in each compound by examining the formula and cross-checking with the table of – common polyatomic ions: The name for HCO3 is hydrogen carbonate.
2. ZnCO3
3. Combine the names: sodium hydrogen carbonate
5. Al2(CO3)3
3. Mg3(PO4)2 4. CaSO4
Elements combine to form ionic compounds and molecular compounds.
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Writing Formulas for Ionic Compounds It is possible to write the chemical formula for an ionic compound when given the name (Figure 6.13). The steps in Table 6.6 will help you write the formulas for ionic compounds. Table 6.6 Steps for Writing Formulas for Ionic Compounds
Take It Further A hydrate is a compound that has water molecules linked to it. Hydrates usually involve ionic compounds. Two examples of hydrates are magnesium sulphate heptahydrate (bath salt) and sodium carbonate decahydrate (washing soda). The formulas for these substances are MgSO4•7H2O and Na2CO3•10H2O. With a partner, research other hydrates and make a reference guide of their uses, properties, and formulas. Begin your search at ScienceSource.
Steps
Examples
1. Examine the compound’s name. Identify the ions and their charges.
magnesium chloride
2. Determine the number of each ion needed to balance the charges.
Mg2+
3. Note the ratio of positive to negative ions, and write the formula.
MgCl2
Mg2+
Cl–
calcium nitride
iron(II) oxide
Ca2+
Fe2+
N3-
O2-
Cl–
Cl–
Ca2+ Ca2+ Ca2+
Fe2+
N3-
O2-
N3-
Ca3N2
FeO
Figure 6.13 The chemical name for this pink-purple crystal is calcium fluoride. Its formula is CaF2.
Practice Problems
Write the formulas for the following ionic compounds.
Example Problem 6.4 Write the formula for potassium sulphide.
1. lithium bromide
1. Identify the ions and their charges: K+ S2–
2. magnesium fluoride
2. Determine the number of each ion needed to balance the charges: K+ K+ S2–
3. silver nitride 4. iron(III) chloride 5. chromium(III) sulphide
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3. Note the ratio of positive to negative ions, and write the formula: K2S
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Formulas for Compounds with Polyatomic Ions The rules for writing formulas for compounds containing polyatomic ions are similar to the rules for other ionic compounds. One difference is that brackets may be used to show the ratio of ions. For example, in Zn(OH)2 there is one Zn2+ for every two OH–. Table 6.7 shows how ions are identified so that the formulas for the compounds can be written. Notice that in sodium hydroxide, the 1+ charge on Na+ balances the 1– charge on the polyatomic ion OH –. Since there is one Na+ for every OH –, the formula for sodium hydroxide is NaOH and no brackets are used (Figure 6.14).
Figure 6.14 The common name for sodium hydroxide is lye, and its formula is NaOH. Sodium hydroxide is used in low concentrations in lye soap (a) and in high concentrations in drain cleaner (b).
Table 6.7 Examples of Polyatomic Ions in Formulas Name
sodium hydroxide
zinc hydroxide
aluminum sulphate
sodium phosphate
Ions
Na+ OH–
Zn2+ OH–
Al3+ SO42–
Na+
Ratio of ions
Na+
Zn2+
Al3+
Na+ Na+ Na+
OH–
OH– OH–
SO42– SO42– SO42–
PO43–
NaOH
Zn(OH)2
Al2(SO4 )3
Na3PO4
Formula
Al3+
PO43–
Example Problem 6.5 Write the formula for magnesium phosphate. 1. Identify the ions and their charges: Mg2+ and PO43– 2. Determine the numbers of each ion needed to balance the charges: Mg2+ Mg2+ Mg2+ PO43– PO43– 3. Note the ratio of positive to negative ions: three Mg2+ for every two PO43– 4. Use the ratio to determine what subscripts to use. If a subscript is needed for the polyatomic ion, include brackets and place the subscript outside the brackets: A subscript of 3 is needed after Mg2+. A subscript of 2 outside a bracket is needed for PO43–.
Practice Problems
Write the formulas for the following ionic compounds. 1. aluminum hydroxide 2. calcium sulphate 3. sodium carbonate 4. iron(III) carbonate 5. copper(II) sulphate
5. Write the formula: Mg3(PO4)2 Elements combine to form ionic compounds and molecular compounds.
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Table 6.8 Prefixes Used for Naming Molecules Number of Atoms
Prefix
1
mono
2
di
3
tri
4
tetra
5
penta
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Naming Molecular Compounds For the names of molecular compounds of two elements, Greek prefixes are used to indicate how many atoms of each element are present in a compound. The prefixes are listed in Table 6.8. For example, N2O3 is a molecular compound present in car exhaust that contributes to smog. Its name is dinitrogen trioxide. The “di” means “2” and the “tri” means “3”. The rules in Table 6.9 will help you to name molecular compounds of two elements. Table 6.9 Steps for Naming Molecular Compounds
Steps
Examples
1. Examine the formula.
N2O
PBr3
CS2
2. Name the first element. Note that the prefix “mono-” is not used when the first element is only one atom.
nitrogen
phosphorus
carbon
3. Name the second element, which ends with “–ide.” When the prefix “mono-” is required before “oxide,” the last “o” in the prefix is dropped. For example, it is “monoxide,” not “monooxide.”
oxide
bromide
sulphide
4. Add prefixes indicating the numbers of atoms.
dinitrogen monoxide
phosphorus tribromide
carbon disulphide
Molecular compounds containing hydrogen or more than two elements are often given special names, as in Table 6.10. Table 6.10 Common Molecular Compounds that Contain Hydrogen Common Name
Chemical Name
Formula
Use
Natural gas
methane
CH4
fuel, plastics industry
Wood alcohol
methanol
CH3OH
antifreeze
Table sugar
sucrose
C12H22O11
sweetener
Rubbing alcohol
propanol
C3H8O
antiseptic
Practice Problems
Example Problem 6.6
Write the names of the following molecular compounds.
Write the name for P2O5. 1. Name the first element: phosphorus
1. CO
4. N2O4
2. Name the second element, which ends with “ide”: oxide
2. CI4
5. PCl3
3. Add prefixes indicating the numbers of atoms: diphosphorus pentaoxide
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Writing Formulas for Molecular Compounds You can also work backward to determine the formula of a binary molecular compound from its name. The prefixes indicate the number of atoms of each type of element (Table 6.8). Practice Problems
Write the formulas for the following molecular compounds.
Example Problem 6.7 Write the formula for carbon tetrachloride. 1. Identify the first element, and give its symbol: carbon, C
1. carbon dioxide
2. Identify the second element, and give its symbol: chlorine, Cl
2. oxygen difluoride
3. Add subscripts to indicate the numbers of atoms: Carbon does not have a prefix, so there is only one C. The prefix “tetra” is used with chloride, so a subscript of 4 is needed after Cl.
3. nitrogen trifluoride 4. phosphorus pentafluoride 5. dinitrogen trioxide
4. Write the formula: CCl4
B25 Quick Lab Copper Compounds Copper reacts with non-metals to form various colourful compounds. Copper reacts with oxygen to form red or black copper compounds. In moist air, copper reacts to produce a blue-green compound called copper(II) carbonate. Vinegar (acetic acid) and copper react to produce copper(II) acetate.
Purpose To produce a copper compound
Materials & Equipment • 2 pennies
• vinegar (acetic acid)
• 1 paper towel
Figure 6.15 The copper rooftops of Canada’s Parliament Buildings are coated with a blue-green copper compound.
Procedure
4. Unfold the paper towel, and observe the penny. Compare it to a penny not soaked in acetic acid.
1. Observe a penny, and note its properties. 2. Fold a paper towel in quarters. Moisten the paper towel with acetic acid.
Questions
3. Fold the wet paper towel around the penny. Set the paper and penny aside overnight or longer.
5. Describe any evidence of a chemical reaction. 6. What colour is copper(II) acetate?
Elements combine to form ionic compounds and molecular compounds.
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B26
STSE Decision-Making Analysis
Skills References
4, 6
■ ■
identifying and locating research sources Thinking critically and logically
Salt or Sand? Issue
Analyze and Evaluate
Canadian winters are harsh. Keeping our roads safe in winter is a vital concern for Canadians. Safety can be enhanced by improving traction, or grip, on slippery roads. Many car owners use winter tires, while others add chains to their tires. Substances such as road salt, sand, or gravel are also used to reduce slippery conditions. However, road salt can harm the natural environment and damage stone structures and metal on cars. Some ingredients in road salt are also toxic.
Your task is to find information about the costs and benefits of using various road salts, sand, or alternative methods to treat icy roads. This information will help you to evaluate whether or not your school or community is making the best decision for your safety and the environment. You will present your findings in a table and your decision in a brief paragraph.
Background Information Calcium chloride (CaCl2) and sodium chloride (NaCl) are the major components of road salt. Magnesium chloride (MgCl2) and iron salts may also be used in small amounts. The substances are finely crushed and spread on icy roads and pavements (Figure 6.16). In the right conditions, road salt helps ice melt away. Salt lowers the freezing point of water. For example, a 20 percent salt solution freezes at about −16°C, whereas fresh water freezes at 0°C. However, much below −15°C, road salt is not effective. Unfortunately, road salt can be harmful to plants and animals. Some types of plants die if the soil is too salty. Pets may step in the road salt and become ill when they lick their paws. Wildlife that wanders on to highways to lick the road salt may get hit by vehicles. Road salt can also damage built structures. In Ottawa, a limestone wall along a popular route is covered by plywood boards every winter. Though unattractive, these boards protect the limestone from being “eaten away.” Left uncovered, the limestone would react with the CaCl2 in the road salt.
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1. ScienceSource Begin your search for information. Use search engines. Try keywords such as “road salt,” “calcium chloride,” “winter driving,” and “road safety.” Be sure to keep a list of your online sources of information. 2. Look in print materials such as magazines, newspapers, and books for information on the effects of salt on cars and roads in Ontario. Keep a list of all information sources. 3. Examine the listed ingredients in different brands of road salt. Compare a “paw safe” brand to another. Find out about the properties of each ingredient and why it is used. 4. Create a table summarizing the pros and cons of using road salt. Give your table a title. Under “Options,” list types of road salt, sand, or alternatives such as tire chains. For the other headings, use “Pros,” “Best Conditions for Use,” and “Cons.” 5. Based on what you now know, would you use salt on the roads in your neighbourhood? If so, in what conditions would you use road salt? If not, what alternative would you use and why? Write a brief paragraph to answer these questions. Refer to the table you created to help you as you write.
Figure 6.16 Some road salts contain colour to make it easier to see where they have been spread.
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CHECK and REFLECT (d) methane
Key Concept Review 1. Identify each of the following as an atom, an ion, an ionic compound, or a molecular compound. (a) C
(e) CO
(b) CO2 2-
(c) CO3
(e) sucrose 6. Write the name of each of the following molecular compounds.
(f) NaCl
(a) CBr4
(d) IBr2
(b) NO
(g) NF3
(e) PCl3
(c) OF2
(f) N2O3
(d) Co 2. Using the periodic table on page 191, write the ion notation for all possible ions of each of the following elements. (a) lithium (b) strontium
Connect Your Understanding 7. Consider the process in which an iron atom turns into an iron(III) ion. Explain whether the atom gains or loses electrons in this process and how many. 8. Explain why H2S is a compound but HCO3– is not.
(c) vanadium (d) chlorine (e) sulphur 3. Write the chemical names of the following ionic compounds. (a) Li2O
(e) Mg(OH)2
(b) CaF2
(f) FeCl2
(c) KF
(g) Al2(SO4)3
(d) Na3N 4. Write the chemical formula for each ionic compound below. (a) magnesium chloride (b) sodium sulphide (c) calcium phosphide (d) potassium nitride (e) calcium fluoride (f) aluminum oxide 5. Write the formulas for the following molecular compounds. (a) nitrogen triiodide (b) carbon dioxide (c) sulphur hexafluoride
9. Use the following diagram to answer this question. (a) What do the differentcoloured balls in the diagram represent? (b) What do the lines in the diagram represent? (c) What compound is shown?
Question 9
10. Create a concept map about compounds. Include references to both ionic and molecular compounds, how to tell them apart based on their formulas, and some examples of specific compounds and their uses.
Reflection 11. List three chemical names for substances for which you knew only the common names when you began this section. For more questions, go to ScienceSource. Elements combine to form ionic compounds and molecular compounds.
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Balancing the Hazards and Benefits of Compounds
6.3
Here is a summary of what you will learn in this section: • Society has many uses for elements and compounds. • Synthetic chemicals such as CFCs and POPs can pollute the environment and are hard to break down. • Chemistry gives us the knowledge to make informed personal decisions that have a collective environmental impact.
Figure 6.17 These students are dropping off batteries at a collection depot in Toronto, Ontario. Some batteries contain toxic chemicals.
Toxic Chemicals, Useful Chemicals All substances, natural and manufactured, are chemicals. Water, gases in the air, the components of our bodies — all are made of elements and compounds and mixtures of them. Our society relies heavily on manufactured chemicals such as paints, plastics, fertilizers, and pesticides. Many of these chemicals are potentially hazardous, but we continue to produce and use them because they have many benefits and because we have found ways to use them safely and responsibly. How we make and dispose of chemicals is also very important (Figure 6.17).
From Manufacturing to Recycling
Figure 6.18 Manufacturing cellphones can release toxic chemicals.
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Look at the materials in the room where you are sitting. Try to find something in the room that was not made using potentially toxic or hazardous chemicals (Figure 6.18). Many paints are toxic when wet. Do you see any plastic? Most plastics, including those safe for storing food or wrapping sandwiches in, are produced from compounds that are toxic. Issues involving the use of chemicals go beyond whether the product we end up with is safe. For example, it includes concerns about the health of workers exposed to toxic substances during
Atoms, Elements, and Compounds
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manufacture. It also means preventing toxic substances from escaping into the environment. Many manufacturing processes produce byproducts that must be carefully disposed of. If this is not done, even if the final product is safe, making the product can harm people and the environment. Some products are safe until they are thrown away. For example, some batteries contain mercury (Figure 6.19). Mercury is a poison, but it is not a problem as long as the battery remains sealed. A battery may be used for mere hours or days, but if it is thrown in the garbage it may spend a decade in a ditch slowly leaching mercury into ground water. Proper disposal is essential to protect people and the environment from hazardous chemicals. For example, many communities treat computer parts and other electronic components as hazardous waste. Landfills typically ban old computer parts because they contain heavy metals.
Figure 6.19 Alkaline batteries are considered safe to throw in the garbage, but other batteries may contain toxic substances.
B27 Quick Lab What Do I Do with My Batteries? Many of the portable electronics we enjoy and rely on require a regular supply of new batteries. Even rechargeable batteries eventually wear out and can no longer be recharged. Some batteries are considered a hazardous household product because they can leach long-lasting contaminants, such as heavy metals, into the environment if not disposed of properly.
Purpose
Questions 3. With a classmate or as a class, discuss the following questions. (a) What are some of the elements and compounds found in disposable batteries? (b) What are some of the elements and compounds found in rechargeable batteries? (c) Are there battery collection depots easily available to you? If so, do you have an obligation to use them?
To identify battery use and safe disposal options
Procedure
(d) If a battery collection program is not available in your community, what could you do to establish one?
1. Estimate the number of battery-operated electronic devices that you use every day. 2. Identify those electronic devices that you use that come with rechargeable batteries (for example, laptops, iPods, and cellphones).
Elements combine to form ionic compounds and molecular compounds.
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Elements and Compounds in the Environment
During Writing Adding Details To add details to your writing, explain what something is and when and why it happens. Then, provide one or more examples or even describe real-life situations that give us a good picture of the topic. Note the ways that the paragraphs on mercury use some of these methods for adding details.
Suggested STSE Activity • B29 Decision-Making Analysis Case Study on page 237
Some chemicals are safe to handle but can cause long-term environmental damage. Other chemicals are toxic, even in tiny amounts, although the effects of exposure can take years to become apparent. Careful use, monitoring, and control of most chemicals mean that ways can be designed to use them safely.
Mercury Mercury is an element that is present in the environment naturally, but in very low levels. Although humans have always been exposed to tiny amounts of mercury, we do not know of any way in which it is good for our health. In high enough concentrations, it can cause mercury poisoning. Mercury poisoning has many devastating effects on the nervous system and muscles. Symptoms include rashes, numbness, tremors, slurred speech, and tooth loss. Mercury poisoning can also cause reproductive problems and birth defects. A number of human activities greatly increase mercury levels in the environment. One of these activities is burning coal for energy. Researchers estimate that the amount of mercury in the air is two to three times what it was before society started relying on coal and other fossil fuels for energy. The mercury levels in coal are low, but as the coal is burned, mercury atoms are spread into the atmosphere. In the environment, the mercury becomes more concentrated. It falls to the ground with precipitation and contaminates water. Then, bacteria in the water change mercury into an even more toxic substance, the compound methylmercury. Methylmercury builds up readily in plants and animals. Animals that eat other animals have the highest concentration of mercury in their bodies. Chemicals that occur in low concentrations are often measured in parts per million (ppm) or milligrams per kilogram (mg/kg). A piece of fish having a mercury concentration of 1 ppm has one part mercury per million parts fish meat. Health Canada recommends that people do not eat fish with more than 0.5 ppm mercury on a regular basis. In Ontario, mercury exposure is greatest among Aboriginal communities in the north who often eat fish caught in the local area. Mercury in the Wabigoon River System Many pulp and paper mills use chlorine bleach to make white paper. It is possible to produce chlorine gas needed to make paper
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Figure 6.20 The Wabigoon River System of Ontario. People who eat fish caught in this river system have had mercury poisoning.
products by dissolving salt in water and passing an electric current through it. Until the 1980s, the process of chlorine manufacture often used mercury. In northern Ontario, near Dryden, facilities to make chlorine used mercury, but the disposal was not carefully controlled, so large amounts of mercury leaked into the environment. Tonnes of mercury were released into the Wabigoon water system each year. The mercury was contaminating the environment and slowly poisoning the people who lived there (Figure 6.20). The issue became worldwide news in the 1970s, as fishing was banned due to high mercury levels. Residents showed symptoms of mercury poisoning. As a result, regulations were introduced to require tracking of mercury in the chlorine plant. With careful monitoring of mercury and improved techniques for using it, the escape of mercury was cut to one-thousandth of its highest levels. Within a few more years, the release of mercury was reduced to zero as a process that did not require mercury was put in place. Decades later, mercury levels are slowly dropping in the local environment. Mercury, Science, and Society Mercury lasts a long time in the environment. Studies are ongoing over 40 years later on the health effects on local peoples affected by mercury spills near Dryden. A process to compensate people has been set up, though it cannot repair the human tragedy, loss of employment, damage to tourism, and harm to the environment (Figure 6.21). Science has an important role to play in our society. Science can be used to assess the impact of technologies on society and the environment. Science also helps us to monitor ongoing practices and to improve methods of handling matter.
MERCURY DISABILITY BOARD THE GRASSY NARROWS & ISLINGTON BAND
A Historical Report 1986-2001 A CONDENSED VERSION
1
Len Manko
Figure 6.21 The disability board implements settlement payments arising out of mercury contamination and has representatives from Aboriginal, provincial, and federal governments.
Elements combine to form ionic compounds and molecular compounds.
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CFCs and the Ozone Layer The story of chlorofluorocarbons (CFCs) is another example of why it is important to monitor how chemicals are used. Eighty years ago, most homes kept stored food cool by placing it in a container with a large block of ice. The household “icebox” needed a constant supply of new ice, which was very inconvenient. The introduction of CFCs changed all that (Figure 6.22). CFCs are gases that can be used in refrigeration units to keep them cool. CFCs are non-toxic and non-flammable and were thought to be safe. In the 1970s, monitoring showed that the ozone layer, which blocks harmful UV rays from the Sun, was being destroyed by CFCs (Figure 6.23). In addition to CFCs leaked from old fridges, CFCs were being released into the atmosphere from aerosol spray cans and even asthma medications. In response, representatives from many countries met in Montreal in 1987 and decided that CFCs were too harmful to try to control. Their use had to be stopped. Canada and many other countries pledged to phase out the use of CFCs and then carried through with their ban. New technologies were invented to replace the need for CFCs. By 1997, the ozone layer was starting to get thicker, and it appears an environmental catastrophe had been narrowly averted. However, it could be 2050 before the hole in the ozone layer closes completely.
F
CI
C
F
Figure 6.22 CFCs
Figure 6.23 The ozone hole over Antarctica in the fall of 2006. Dobson units are a measure of ozone concentration.
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Benzene — A Regulated Substance You have probably seen presentations made with an overhead projector. You may have used one yourself, or your teacher may have used one in science class. The sheets of clear plastic used for overheads are called acetate sheets because they are made with a type of plastic called acetate. The process for making acetate plastics uses several compounds, one of which is benzene. Benzene is a hazardous chemical that is both toxic and flammable, but it can be used safely if proper procedures are carefully followed. Why use benzene if it can be harmful? Benzene continues to be used because it is important in many applications. It is one of the top 20 chemicals by volume produced in North America (Table 6.11). It is used to make dyes, detergents, and medicines, such as aspirin. These substances do not have benzene’s toxic properties. Environmental and health concerns are met by carefully handling and controlling the use of benzene.
Table 6.11 Some of the Top Chemicals Produced in North America Chemical
Production (109 kg)
sulphuric acid
39.62
calcium oxide
20.12
phosphoric acid
16.16
ammonia
15.03
sodium hydroxide
10.99
sodium carbonate
10.21
nitric acid
7.99
ammonium nitrate
7.49
hydrogen chloride
4.34
benzene
2.01
Safe Transportation and Handling of Benzene Benzene is a regulated substance. This means it must be used only according to strict guidelines that are regularly reviewed and revised (Figure 6.24). For example, workers should not be exposed to an average benzene concentration of more than 1 ppm. At higher concentrations, workers must wear masks with activated charcoal filters. These measures may seem complicated, but they are designed to protect workers and still allow chemical processing to continue. Science and technology make it possible Figure 6.24 Benzene is handled safely by keeping it in sealed to use a potentially hazardous substance systems such as this one. such as benzene safely and effectively to produce materials that we need and want. We can manage hazardous substances through a combination of:
• understanding the properties of substances and how to use these substances safely • designing innovative equipment and processes • placing personal safety and environmental protection as the top priority • enforcing effective regulations Elements combine to form ionic compounds and molecular compounds.
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Learning Checkpoint 1. What are some of the heath problems associated with exposure to mercury? 2. What are two kinds of human activities that have resulted in the release of excess mercury into the environment? 3. What is the effect of ozone in the upper atmosphere? 4. Why were CFCs originally thought to be safe and useful, and why were they determined to be unsafe? 5. List four ways to aid in the safe handling of regulated substances.
B28
STSE Science, Technology, Society, and the Environment
POPs and Pesticides Dichloro-diphenyl-trichloroethane (DDT) is an effective pesticide that kills insects. Although it has not been used in Canada since the 1980s, it is still used in some countries to kill mosquitoes that transmit malaria. Malaria is a serious disease that kills hundreds of thousands of people each year, many of them children. DDT belongs to a group of compounds known as persistent organic pollutants (POPs). A persistent pollutant is a chemical that will not break down in the environment. POPs are of special concern because they can build up in the body tissues, a process called bioaccummulation. Levels of the chemicals become even more concentrated in predator animals than in their prey, a process called biomagnification. Chemicals that biomagnify can build up to toxic concentrations in animals at the top of the food chain, such as bears, eagles, and humans. POPs have a number of properties that can allow them to bioaccumulate in body tissues and biomagnify in food chains: • They are long lived, meaning that they persist in the environment for a long time before breaking down into simpler compounds. • They move easily from place to place, where organisms can come in contact with them. • They are fat soluble and so can be stored in fatty tissues of the body.
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Figure 6.25 This type of mosquito can transmit malaria
• They easily change state from solid to gas and back again with temperature changes. 1. In countries where malaria outbreaks are common, DDT is sprayed on surfaces inside the home. It is also common to make mosquito netting that contains DDT. The nets can be draped around beds and babies' cribs. This method of using DDT is considered much safer than spraying DDT in the air. Do the benefits of using DDT outweigh the risks in some cases? Justify your response. 2. State what properties you would consider when choosing a pesticide to use on: (a) food crops (b) your lawn (c) a playground 3. List situations in which pesticides might be used. Rate how necessary you think their use is in each case. 4. What are some alternatives to using pesticides?
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CASE STUDY
B29
SKILLS YOU WILL USE
STSE Decision-Making Analysis
SKills References
4, 6, 7
Fluoridation of Drinking Water Issue Fluoride is often added to drinking water to help prevent tooth decay. However, some people argue that fluoridation of drinking water is unsafe.
Background Information Ever since fluoride was first added to the water supplies of Grand Rapids, Michigan, in 1945, the controversy over the fluoridation of drinking water has raged, with scientific facts becoming confused. Supporters of fluoridation say that it prevents the incidence of tooth decay and presents minimal health risks. Health experts have called it “1 of 10 great public health achievements of the 20th century.” Groups such as the American Dental Association say that fluoridation of water reduces the incidence of tooth decay by 40 percent to 65 percent. On the other hand, some people say that the fluoridation of drinking water may cause serious health problems in some individuals. Some question its effectiveness in preventing cavities. Also, some people note that they already consume fluoride in their food. Furthermore, many critics see fluoridation as a violation of individual choice, saying it is a form of medication imposed on the public. Others believe that the effects of fluoride should be investigated using the same criteria as for other environmental pollutants. The data to support the fluoridation campaign were strengthened by a study comparing Sarnia, Brantford, and Stratford, Ontario. In that study, tooth decay in Brantford dropped from a rate of over 90 percent for children age 9–11 to about 55 percent following the addition of 1 ppm fluoride ion to the water. The low rate matched that in Stratford where the water naturally contained 1.6 ppm fluoride ion. However, tooth decay is a complicated process, influenced by diet, oral hygiene, dental care, genetic factors, and the presence of naturally occurring chemicals such as fluoride in drinking water.
Thinking critically and logically Communicating ideas, procedures, and results in a variety of forms
Currently, fluoride is added to water supplies in parts of Canada, the United States, Australia, Russia, and some other countries. In developing countries, where only small amounts of sugar and processed foods are eaten, the rates of tooth decay are often lower than in developed nations such as Canada. Medical authorities such as Health Canada, the Canadian Medical Association, the Canadian Dental Association, and the Canadian Public Health Association continue to support fluoridation.
Analyze and Evaluate 1. From the information provided, prepare a Plus-Minus-Implications (PMI) chart about the addition of fluoride to water supplies. 2. Research the use of fluoride in toothpaste. Identify the fluoride-containing compounds used in different brands of toothpaste. The tubes have labels warning that young children should use very small amounts of toothpaste to prevent excessive fluoride intake. 3. Identify the reasons behind the controversies related to fluoride campaigns. 4. ScienceSource Begin your research on the Internet. Be sure to keep a list of your sources of information. 5. Look in print materials such as magazines, newspapers, and books for information on fluoridation of water and fluoride drops. 6. Develop criteria that citizens need to consider to make an informed decision. Identify potential issues and sources of misinformation. 7. Web 2.0 With your partner, create a Wiki, a presentation, a video, or a podcast giving your opinion on the issue of fluoridation based on your research. For support go to ScienceSource.
Elements combine to form ionic compounds and molecular compounds.
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CHECK and REFLECT
Key Concept Review 1. Is water a chemical? Explain. 2. List four kinds of manufactured chemicals that have widespread use in our society. 3. What are some of the negative health effects of exposure to high levels of mercury? 4. List three reasons why hazardous chemicals continue to be produced in our society.
15. How are pollution in the environment and human health related? Explain, using one or more specific examples. 16. Mercury glass thermometers used to be common, but now we use digital or glassalcohol thermometers. The mercury in a thermometer is contained, so why would digital or glass-alcohol thermometers be safer to use than mercury thermometers?
5. Dry cell batteries that contain mercury are tightly sealed. How can the mercury in a dry cell battery end up in the environment? 6. How can the burning of coal lead to the build-up of mercury in lake trout? 7. How did the production of chlorine gas lead to mercury poisoning of residents of the Wabigoon River system? 8. What were the main uses of CFCs in the 20th century? 9. Benzene is one of the top 20 chemicals produced in North America. What are three of its uses?
Question 16
12. What is the environmental hazard related to widespread use of CFCs?
17. Once residents of the Wabigoon River system began showing medical signs of mercury poisoning, action was taken to eliminate mercury contamination. This was done in several steps. How was the release of mercury to the environment first reduced and then eliminated?
Connect Your Understanding
Reflection
13. CFCs were widely used because at first they were considered to be safe. What two properties did they have that led people to believe CFCs were safe to use?
18. What have you learned in this section about the production and use of chemicals for commercial and industrial purposes? What do you consider the most important message related to the production and use of chemicals in our society?
10. Benzene is a regulated substance. What does this mean? 11. What ways of handling benzene help it to be used safely?
14. In the future, will you recycle cellphone batteries or throw them in the garbage? Explain your decision. 238
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For more questions, go to ScienceSource.
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COOL IDEAS f r o m J AY I N G R A M
How Small Is an Atom? Atoms are small — we all know that. But how small? It is almost impossible to visualize the atomic realm, but here is an image that might help. Half a century ago, physicist Richard Feynman did the math to show that all the volumes of the biggest encyclopedia of the time, the Encyclopedia Britannica (but think of Wikipedia), could be written on the head of a pin (Figure 6.26). Feynman started by showing that if you shrank all the pages of all the volumes of the encyclopedia by 25 000 times, they would fit onto that pin. But could you actually write words and print pictures in that ultramicroscopic world? Well, yes, you could — as long as you pulled together atoms for each of the little dots that make up the images and letters in the encyclopedia. Those dots are barely visible to the unaided eye, but shrink one of them 25 000 times, and it could still contain a thousand atoms (Figure 6.27). You would actually have space left over.
Figure 6.26 A single page from the Encyclopedia Britannica
Jay Ingram is an experienced science journalist, author of The Daily Planet Book of Cool Ideas, and host of the Daily Planet on Discovery Channel Canada.
But Feynman wasn’t finished. He went beyond Encyclopedia Britannica to think about all the books ever written. He figured that if you scoured all the libraries in the world you would come up with enough print to cover a million pinheads. That is a lot, but if you converted it all into code, like computer language, you would only need about 100 atoms for each bit of that code. That meant that all the books ever written could be stored in a cube of atoms one two-hundredth of an inch across; that is slightly smaller than two of the (barely visible) dots making up the letters and pictures in this book. That is how small atoms are.
Question 1. What comparisons and analogies did the author use to convey the size of an atom? How did his writing strategy help you to get a sense of the size of an atom? Figure 6.27 The dark spots in this image are individual atoms in a silicon crystal. It took a powerful microscope called a transmission electron microscope to view these atoms, shown here magnified about 5 million times.
Elements combine to form ionic compounds and molecular compounds.
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CHAPTER REVIEW
ACHIEVEMENT CHART CATEGORIES t Thinking and investigation k Knowledge and understanding c Communication
a Application
7. Write the formula for each of the following molecular compounds. k (a) nitrogen monoxide
Key Concept Review
(b) carbon disulphide
1. Define the term “compound.” Give an example. k 2. (a) The chemical formula for hydrogen peroxide is H2O2. What elements are present in this substance and in what ratio? k
(c) phosphorus tribromide 8. Does the following diagram depict a molecular compound or an ionic compound? Explain. k
(b) Identify hydrogen peroxide as an ionic compound or a molecular compound. k (c) Name two uses for hydrogen peroxide. k
3. Indicate whether or not each of the following elements can form ions, and if so, give all possible ion symbols. k (a) nitrogen
(e) chlorine
(b) lithium
(f) sodium
(c) aluminum
(g) xenon
(d) oxygen
(h) copper
4. Write the chemical name for each of the following ionic compounds. k (a) KI
(b) CaCl2
(c) AlBr3
5. Write the formula for each of the following ionic compounds. k (a) lithium nitride
10. Write the name or formula for the following compounds. k (a) magnesium hydroxide (b) sodium carbonate (c) aluminum sulphate (e) BaCO3
(c) sodium hydroxide
(f) K2SO4
6. Write the chemical name for each of the following molecular compounds. k (b) Cl2O3
9. Why are chemists interested in the valence shells of atoms? k
(d) CsHCO3
(b) iron(II) chloride
(a) PF5
Question 8
(c) CF4
11. (a) What is the main difference between ionic bonds and the bonds in a molecule? k (b) Which generally have higher melting temperatures: ionic compounds or molecular compounds? k
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12. How are chemical names different from common names? Provide an example. k
Connect Your Understanding 13. Glucose, acetic acid, and propanol are all composed of the same three elements: carbon, oxygen, and hydrogen. How can these very different compounds can be composed of the same elements? t 14. (a) Which types of batteries are considered safe to throw in the garbage? a (b) Are there any disadvantages to throwing batteries in the garbage if it is safe to do so? Explain. t (c) Evaluate the advantages of using rechargeable batteries rather than disposable ones. t 15. Chlorine is a compound that is toxic in high concentrations as a gas but which can also be used in drinking water supplies to make the water safe to drink. How might each of the four guidelines for using hazardous substances safely on page 235 be applied to the use of chlorine? a 16. What are three actions that your community could take to reduce mercury contamination of the environment? Present your ideas in a poster, a letter to the editor of your school newspaper, or a 30 s public service announcement. c 17. What would you want to find out about a chemical pesticide before using it on a lawn or a playing field? a 18. Explain the history of the use of CFCs by addressing the following questions. Why were they produced, and what were they used for throughout the world? Why were CFCs once thought to be safe, and why did they turn out to be unsafe to use? How did the world community respond to new knowledge about the effects of CFCs on the environment? a
19. Use the example of CFCs to explain why many people believe that when it comes to releasing new compounds into the environment we should proceed with caution. a 20. List the common names for two compounds mentioned in Chapter 6 that you are familiar with from your everyday life. Give the common uses, chemical names, and formulas for these compounds. a
Reflection 21. Briefly describe three ways in which specific compounds can affect your personal health that you were unaware of before reading Chapter 6. c 22. Describe an issue related to the manufacture, use, or disposal of chemicals that you had not thought about before reading this chapter. c
After Writing Reflect and Evaluate Choose your opinion paragraph about road salt or your information piece about the effects of fluoride. Exchange with a partner, read, and provide feedback on how your partner used topic sentences, details, and good flow from one sentence to the next to stay on topic and create unity.
Unit Task Link Chemical names, symbols, and formulas provide us with a common scientific language. How will you communicate the results of your tests of different toothpaste ingredients? Start by naming and giving the formulas for compounds found in commercial toothpastes. Also list the names and symbols of the elements that make up the compounds.
Elements combine to form ionic compounds and molecular compounds.
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UNIT
Summary
KEY CONCEPTS
4
CHAPTER SUMMARY
Matter has physical and chemical properties.
• Particle theory of matter • States of matter • Classifying matter • Observing physical properties • Observing chemical properties • Usefulness and impact of substances’ properties
• All matter is composed of moving particles that attract one another but have spaces between them. (4.1) • Matter can be solid, liquid, or gas, or a combination of states and can change from one state to another. (4.1) • Elements and compounds are pure substances. Mechanical mixtures, suspensions, and solutions are combinations of pure substances. (4.1) • Physical properties are characteristics of a substance that can be observed or measured without changing what the substance is. Physical properties include boiling point, colour, conductivity, viscosity, and adhesion, cohesion, and other special properties of water that are important in living systems. (4.2) • Chemical properties describe how substances react with other substances or to light or heat and can be observed when chemical changes occur. (4.2)
5
The periodic table organizes elements by patterns in properties and atomic structure.
• Atomic theory
• Every element is composed of a distinct type of atom. (5.1)
• Atomic models
• The atomic model continues to be revised based on new experimental evidence. Bohr diagrams are one way to represent atomic structure. (5.1)
• Subatomic particles • Element names and symbols • Properties of common elements
• An atom has a dense nucleus of neutrons and protons, which is surrounded by shells of electrons. (5.1)
• Periodic table
• Each element has a standard name and symbol. (5.2)
• Properties of chemical groups
• The periodic table organizes the metals, non-metals, and metalloids based on properties such as number of protons in an atom. (5.3) • The alkali metals share similar properties, such as conductivity, which are different from the properties of the halogens and noble gases. (5.3)
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Elements combine to form ionic compounds and molecular compounds.
• Compounds • Chemical bonds • Chemical names and formulas • Using elements and compounds
• Compounds are pure substances composed of atoms of two or more elements that are joined by chemical bonds. (6.1) • Ions with opposite charges attract each other in ionic compounds, while atoms in molecules share valence electrons. (6.1) • The formulas for many common compounds can be determined from their names, and vice versa. (6.2) • How we make use of elements and compounds affects society, the economy, and the environment. (6.3)
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VOCABULARY
• • • • • • • • • • • • • • •
adhesion (p. 150) boiling (p. 138) boiling point (p. 139) chemical change (p. 152) chemical property (p. 152) chemical reaction (p. 152) cohesion (p. 150) combustibility (p. 153) compound (p. 141) condensation (p. 138) deposition (p. 138) element (p. 141) freezing (p. 138) freezing point (p. 139) inert (p. 133)
KEY VISUALS
• • • • • • • • • • • • •
mass (p. 138) matter (p. 138) mechanical mixture (p. 142) melting (p. 138) melting point (p. 139) particle theory of matter (p. 139) physical property (p. 150) property (p. 141) pure substance (p. 141) solution (p. 142) sublimation (p. 138) suspension (p. 142) volume (p. 138)
A glowing firefly
• alkali metals (p. 194)
• metals (p. 180)
• atom (p. 168)
• metalloids (p. 180)
• atomic mass (p. 192)
• neutrons (p. 173)
• atomic mass units (amu) (p. 192)
• noble gases (p. 195)
• atomic number (p. 190)
• nucleus (atomic) (p. 173)
• atomic theory (p. 170)
• period (p. 193)
• electrons (p. 172)
• protons (p. 173)
• group (chemical family) (p. 193)
• relative mass (p. 175)
• halogens (p. 194) • ion (p. 192) • ion charge (p. 192)
• bond (p. 213) • chemical formula (p. 219) • ionic bonds (p. 213) • ionic compounds (p. 212)
Adhesion and cohesion of water droplets
• non-metals (p. 180)
• subatomic particles (p. 175)
Chlorine, bromine, and iodine
• valence electrons (p. 197) • valence shell (p. 197)
• molecular compound (p. 213) • molecules (p. 213) • parts per million (ppm) (p. 232)
Salts
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Summary
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UNIT
Task
Design a Toothpaste Your Goal Toothpastes are designed to remove plaque and prevent cavities. They work by making it easier to brush plaque away, killing plaque bacteria, making teeth stronger, or a combination of these effects. Your task is to investigate the properties of commercial toothpastes and possible ingredients for homemade toothpastes. You will design the testing procedure and carry it out.
What You Need to Know Plaque bacteria on teeth
Getting Started Tooth decay is a chemical process — helped along by bacteria. Within a couple hours of brushing your teeth, bacteria build up and produce a sticky coating. This coating, along with the bacteria, is known as plaque. As the plaque bacteria feed on sugars in your food, they make acids, which corrode your teeth. The bacteria grow especially well if they have sucrose to feed on. Tooth decay can lead to headaches, cavities, and tooth loss. Plaque itself can irritate the gums and make them shrink. In extreme cases, plaque can get into the bloodstream and damage the heart.
Criteria for Success • You must justify why you are investigating particular properties. For example, you may have safety concerns about certain ingredients. You may predict that some ingredients will be better at removing plaque than others.
Some 5000 years ago, the Egyptians made tooth powders from the ashes of ox hooves, myrrh, powdered and burnt eggshells, and volcanic rock. By the late 1800s, toothpaste was designed to be better tasting and more effective. Today’s commercial toothpastes contain ingredients such as sweeteners (typically saccharin or xylitol), preservatives, and artificial flavours. Fluoride compounds are also added to make the teeth stronger and more resistant to decay. In recent years, new ingredients have been added to toothpastes to remove stains and whiten teeth, kill bacteria, and improve breath. In normal use, it is expected that you might swallow a small amount of toothpaste inadvertently. This is not dangerous. However, in high concentrations, some of the substances in toothpaste can be toxic, and so toothpaste should not be consumed. For safety reasons, chemists do not conduct initial tests of products like toothpaste on people. They start by investigating the properties of ingredients and using models to see how products might work.
• You must design and use an observation table to record observations of properties. • You must test the effectiveness of different toothpastes or ingredients using a model. • Based on your results, you should design a homemade toothpaste.
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What You Need • toothbrush • two or more 250-mL beakers • spoon • medicine dropper • materials and equipment for testing various properties • hardboiled eggs, small ceramic tiles, sea shells, a plastic cutting board, or other materials that can be stained • dark tea or coffee • molasses or honey • one or more commercial toothpastes • cinnamon, cooking oil, food colouring, glycerin, sodium hydrogen carbonate, sodium chloride, starch, wax, or other possible toothpaste ingredients
CAUTION: Do not taste the toothpastes or the ingredients.
Procedure 1. Decide which properties of substances to investigate for your toothpaste recipe. Select some from the list below, or add others. • hardness • melting point • solubility • texture • reaction with acid • reaction with water
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2. Choose at least one toothpaste and three possible toothpaste ingredients to investigate. 3. Design a procedure for investigating the properties of the substances you chose above. You must include a complete list of materials and equipment. 4. Decide what you will use as a model for teeth. Design a procedure to test the effectiveness of the toothpastes and ingredients. Be sure to include controls and to identify the variables. 5. Have your teacher approve your procedure and materials. 6. Conduct your investigation according to your procedure.
Assessing Your Work 7. (a) What were the properties of the toothpastes and ingredients that you investigated? (b) Which of these properties are useful in toothpaste? 8. Examine your procedure, and make suggestions for improvement. For example, how useful was your model? Were you able to control variables when testing different substances on your model? If you were going to conduct this inquiry again, would you investigate different substances? If so, why? 9. Which type of toothpaste do you prefer? Why? 10. (a) What recipe would you recommend for a homemade toothpaste? (b) How would you improve your recipe? 11. What type of toothpaste would you recommend for a child under two years of age? Why?
UNIT B
Task
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UNIT
Review
ACHIEVEMENT CHART CATEGORIES k Knowledge and understanding t Thinking and investigation c Communication a Application
7. Use the following list of properties to create a profile of a pure substance or mixture of your choice. Add other terms as needed. c • boiling point • colour • combustibility • conductivity • density • ductility • hardness
Key Terms Review 1. Create a concept map to link the key terms listed below. Add examples of substances, where appropriate. c • atom • molecule • electron • neutron • element • period • group (chemical) • proton • ionic compound • pure substance • matter • solution • mechanical mixture • suspension • molecular compound
Key Concept Review
4
Matter has physical and chemical properties.
2. Distinguish between a homogeneous mixture and a heterogeneous mixture.
(a) Diamonds are hard. (b) Gallium will melt in the palm of your hand. (c) Wood burns easily. (d) Iron is magnetic. (e) Some cleaners are corrosive. 5. Distinguish between boiling and condensing. k 6. Use the particle theory of matter to explain how a solid can melt if sufficiently heated. k
Review
8. John Dalton described matter as being composed of atoms. How is his 200-year-old atomic model different from the current atomic model? k
k
4. Identify the following as either physical properties or chemical properties. k
UNIT B
The periodic table organizes elements by patterns in properties and atomic structure.
5
9. How did J. J. Thomson make use of cathode rays to investigate atomic structure? What did he conclude based on his results? k
3. What is the difference between cohesion and adhesion? k
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• lustre • malleability • melting point • reactivity • solubility • viscosity
10. How did Ernest Rutherford discover the atomic nucleus? k 11. How did Niels Bohr contribute to the understanding of atomic structure? k 12. What is the difference between a group and a period in the periodic table? k 13. How are metals, non-metals, and metalloids organized in the periodic table? k 14. List four properties shared by the halogens. k
15. Name an element that reacts vigorously with water. k 16. Give the number of valence electrons in an atom of each of the following elements. k (a) hydrogen
(b) aluminum
(d) oxygen
(e) chlorine
(c) carbon
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(d) ZnO
17. Use the diagram below to answer the following questions.
(e) N2S3 (f) Br2
2+
22. Identify each of the substances in the previous question as an ionic compound, a molecular compound, or neither. k 23. Describe two ways in which mercury affects the body. k
Question 17
(a) What element is shown?
k
(b) What group in the periodic table does this element belong to? k (c) What is the charge on this ion?
k
(d) How many valence electrons are in a neutral atom of this ion? k 18. Name an element that fits each of the following descriptions. k (a) a solid at room temperature (c) an alkali metal
k
(b) How can ion charges be used to determine the chemical formulas of compounds? k 20. Is a metal element more likely to form an ion by losing electrons or by gaining them? k 21. Give the names and ratios of the elements in the following substances. k (b) Al2S3 (c) AgF
25. Name three properties of water that people can benefit from and describe how we benefit. a
a
Elements combine to form ionic compounds and molecular compounds.
(a) LiCl
(b) What are some concerns associated with the use of polyethylene? t
27. How could you alter the viscosity of honey?
(d) a colourful, reactive gas at room temperature
19. (a) Explain what an “ion charge” is.
24. (a) What properties of polyethylene plastic make it useful? a
26. Why would aluminum foam be a good choice of material for a car bumper? t
(b) neither a metal nor a non-metal
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Connect Your Understanding
28. (a) Sugar dissolves in water. Does this mean that all white substances dissolve in water? Explain. t (b) Will a sugar solution conduct electricity? Explain. a 29. What is diamond made of, and why is it not considered to be a compound? a 30. Why can we not dispose of all household waste in the same way? Use at least two examples of specific substances in your answer. a 31. Some early philosophers considered elements to be earth, wind, water, and fire. Why do chemists today no longer classify water as an element? t Unit B
Review
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Review
(continued)
32. (a) Describe one property shared by elements from Group 17 and Group 18. t (b) What is a property that Groups 17 and 18 do not share? t 33. Indicate whether or not each of the following elements can form ions, and if so, give the ion symbol or symbols. t (a) silicon
(b) barium
(c) beryllium
(d) krypton
(e) lead
(f) selenium
34. Can density vary throughout a mixture? Explain. t 35. Describe two patterns found in the periodic table. a 36. For each of the following, state the type of mixture. a (a) a banana milkshake (b) water with sugar dissolved in it (c) tomato juice
38. Which of the following substances will dissolve in water to form a solution that can conduct electricity? a (d) MgO
(b) glucose
(e) CH4
(c) Ne 39. What two pieces of information does a formula for a molecule provide? t 40. Is neon likely to be part of a compound? Why or why not? a 41. Do all compounds that contain only hydrogen, carbon, and oxygen have the same properties as one another? Explain, using two examples. t 42. Use an analogy to describe the quantum mechanical model of the atom. c 43. (a) What do elements in the same period on the periodic table have in common in terms of structure of their atoms? t
37. Use the diagram of benzene below to answer the questions that follow. (a) Benzene contains hydrogen and carbon. What do the different-coloured balls in the diagram represent? a
(a) potassium chloride
(b) How does the atomic structure of the elements change within a period as you read from left to right across the periodic table? t 44. Three containers each hold a different mystery element. Four of their properties are given in the table below. Identify which element is: a (a) a non-metal (b) an alkali metal (c) a noble gas
Question 37
(b) What do the lines in the diagram represent? a (c) Is benzene an ionic compound or a molecular compound? t
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Properties of Mystery Elements Colour
State at 20°C
Reactivity
Conductivity
X
greenyellow
gas
high
no
Y
colourless
gas
none
no
Z
silverwhite
solid
high
yes
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45. What makes a ball-and-stick model a useful representation of a molecule? a
53. Draw a diagram of a boron atom with six neutrons. Label the subatomic particles. c
46. How can the manufacture of safe products, such as plastic food containers, result in the chemical contamination of the environment? t
54. Explain how you could test the conductivity of: a
47. Name three elements that can be harmful if not handled properly. How are they harmful? a
(a) a soft drink (b) a strip of copper metal 55. Use the Bohr diagrams below to answer the questions that follow. 1-
48. Suppose you go on a fishing trip to Lake Ontario and catch several fish. Which fish would be safer to eat and why: a small fish that eats plants or a big fish that eats other fish? a 49. Dish soap dissolves in both water and oil. Why would dish soap be useful for cleaning a waterbird caught in an oil spill? a
Skills Practice 50. Write a word trick to help you to remember the symbols for the elements sodium, silicon, and sulphur. c 51. The salt shown here is cobalt(II) chloride. Describe three properties of cobalt(II) chloride. a 52. Suppose you have collected a gas in a test tube. To identify the gas, you light a wooden Question 51 splint, then blow it out so that it is glowing and put it in the test tube. What do you predict would happen if the test tube were filled with oxygen gas? a
B
A
Question 55
(a) Name the elements shown.
a
(b) Did the ion shown in B form by losing an electron or gaining an electron? a (c) Would the atom shown in A be likely to be found in an ionic compound? Explain. a (d) Would the ion in B be more likely to bond with Ca2+ or with O2– ? Explain. t 56. Draw Bohr diagrams to depict atoms of the following elements. c (a) oxygen
(b) sodium
(c) hydrogen
57. Write the chemical names of the following compounds. c (a) MgBr2
(d) Al2O3
(g) K2CO3
(b) Ba3N2
(e) NaI
(h) MgSO4
(c) Ca3P2
(f) CaCl2
(i) CsHCO3
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(continued) Revisit the Big Ideas and Fundamental Concepts
58. Identify each of the following compounds as either ionic or molecular, and give the formula for each one. c
63. How can the various types of matter that exist be explained by the particle theory of matter? a
(a) magnesium phosphide (b) lithium nitride (c) phosphorus pentachloride
64. How did the development of the atomic model make it easier for people to explain how chemical reactions occur? t
(d) aluminum bromide (e) calcium sulphide (f) sulphur dioxide
65. What are elements, and how are they responsible for the properties of pure substances? a
(g) potassium iodide (h) sodium oxide (i) calcium hydroxide
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(j) aluminum hydrogen carbonate (k) nitrogen trichloride
66. Suppose you were going to purchase a refillable water bottle. Discuss the properties of all of the choices. a
59. Copy the following table into your notebook. Use the periodic table to fill in the blanks. t
(a) new plastic bottle (b) old plastic pop bottle
Information About Elements Symbol
Name
H
Atomic Mass
Science, Technology, Society, and the Environment
Protons In Atom
Electrons In Atom
1.01
(c) aluminum (d) glass Which type of bottle would you choose, and why? t
17 Ca
67. Benzene dissolves in fat, is combustible, and changes state from liquid to gas very readily. Suggest why these properties are considered hazardous. a
silver 10 U
60. Suppose you mixed a copper compound with lemon juice. How would you know if these reacted to form a new substance? a 61. Would you use the number of neutrons in an atom to find the element it belongs to? Explain. t 62. How is road salt different from table salt? Give their chemical names and formulas.
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a
68. Give examples of three substances that can cause pollution if thrown in the garbage. What are the effects of pollution from these substances? a 69. Compare the properties and composition of sand and road salt. If you had a choice between sprinkling road salt or sand to melt ice patches at the entrance to your school, which would you use? Why? a
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70. Why would living in an energy-efficient home help to reduce pollution? t 71. Compact fluorescent light bulbs are much more energy efficient than regular incandescent light bulbs. However, compact fluorescent light bulbs contain tiny amounts of mercury. Suggest what steps should be taken when it comes to handling and disposing of compact fluorescent light bulbs. a 72. How can industrial activities affect water supplies? List at least two ways. a
(b) What are some of the impacts on society, the economy, and the environment when we alter matter?
a
(c) How can we alter matter to meet our needs while improving the conditions of the environment? Explain, using one or more specific examples. t 76. Suppose you visit a lake in a wilderness area that is completely uncontaminated and unaffected by human activity. Is this lake likely to be full of chemicals or not? Explain your reasoning. t
Reflection 77. As this unit has demonstrated, everything around you is composed of chemicals. Briefly describe how your understanding of the concept of “chemicals” changed during this unit. c
Question 72
73. Is keeping water safe to drink the only reason to prevent water pollution? Explain. t
74. Think of one chemical that you know of from each of the following areas that has a positive use in your life: hygiene, food, medicine. Identify the chemical by its common name and, if possible, its chemical name, and state the positive role that it plays. a 75. (a) What kinds of physical and chemical changes can people use to alter matter?
a
78. In the past, people have often used new technologies and chemicals without carefully considering the long-term consequences of their use and disposal. List three issues relating to the use and disposal of chemicals that you became aware of while studying this unit. Write a letter to future generations explaining your view of how these issues should be addressed today and why this will make a difference in the future. c 79. The way in which we apply science and technology impacts the environment. Of the different ways that chemistry can be used to solve environmental problems, describe at least one that you think is very promising based on your new understanding of the properties of matter. c
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This astronaut, who is mounted on the end of the Canadarm2 robotic arm, is making repairs to the International Space Station in orbit around Earth. 252
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Contents 7
Scientific evidence suggests that the universe began expanding from a single point about 13.7 billion years ago. 7.1 Space Flight to the Stars 7.2 Galaxies
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7.3 The Expanding Universe
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The solar system formed 5 billion years ago, in the same way other star-and-planet systems in the universe formed. 8.1 Stars 8.2 The Solar System
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8.3 Earth, the Sun, and the Moon
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Space exploration improves our knowledge and gives us beneficial technologies, but its costs and hazards are significant. 9.1 How Ideas of the Universe Have Changed over Time 9.2 Benefits of Space Research and Exploration
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9.3 Costs and Hazards of Space Research and Exploration
Unit Task In this unit, you will learn about the planets in our solar system and about robotic probes, space missions, and human voyages beyond Earth. For your Unit Task, you will assess which is the more reasonable action: sending humans or sending robotic probes on an extended mission to Mars.
Essential Question Based on ethical, political, economic, scientific, and societal considerations, can a human mission to Mars be justified?
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Exploring
A view of deep space taken by the Hubble Space Telescope
Trying to Picture the Immensity of Space
The area of the image above is about the size of the head of a pin if you were to hold the pin at arm’s length up against the night sky.
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On a still, clear night away from city lights, what you see in the sky might look like what is shown in the image here. All the thousands of twinkling stars we can see from Earth even without a telescope are part of the galaxy we live in, the Milky Way. A galaxy is a collection of hundreds of billions of stars held together by gravity. Therefore, you might be surprised to learn that each speck of light visible in the image above is not a star. Rather, it is an individual galaxy. This picture was taken by the Hubble Space Telescope, which is in orbit (circling) high around Earth and looking far out into space. Consider for a moment that the area of sky that this image shows is equal to the area of the head of a pin held at arm’s length. Even in a patch of sky as small as that, we can see all these galaxies. Think about what that means if each galaxy in the image contains hundreds of billions of stars. The distance from Earth and the Milky Way to these other galaxies is extremely great. Not only that: scientists have also found that, with a few exceptions, all galaxies are moving farther away from ours and from each other. It seems that space between the
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galaxies is expanding, causing the distances to increase. These are incredible thoughts, yet scientific evidence supports them and many other intriguing conclusions about the nature of our universe. Universe is the term we use to refer to everything that physically exists: the entirety of space and time, and all forms of matter and energy. Canada has long worked in cooperation with other countries to explore space — what many people have referred to as the “last frontier.” Canadian astronomers have made many important discoveries through their work at observatories in this country and around the world. Canadian researchers and engineers have produced technological innovations such as robotic systems that are now helping to advance space exploration. Canadian astronauts have travelled into space, lived for weeks at a time on the International Space Station, and conducted many experiments, some on behalf of school students. While exploring space is both costly and hazardous, it seems that humans have never been able to resist the urge to learn more about what lies beyond our own planet. The more we find out, the more we realize there is to discover.
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Astronomers from around the world book time on telescopes such as this one, the Canada-France-Hawaii telescope, to study many aspects of space.
STSE Science, Technology, Society, and the Environment
Space Exploration in the News The Internet, television, radio, and print media often report on discoveries and new advances in the exploration of space. Also widely available are stunning images of celestial objects, taken from Earth and from space-based cameras. In this activity, you will brainstorm a list of news items you have read, watched, or heard about space exploration. You will consider how often space exploration news items are reported in the media and what their implications are for technology, society, and the environment.
1. As a class, brainstorm as many news items as you recall recently reading or hearing about related to the study and exploration of space. As an aid, if necessary, scan the news items brought to class by your teacher. 2. Record the main topics on the board or a flipchart. 3. For each topic, discuss as a class the implications of the event, action, or findings for: (a) society (b) technology (c) the environment
Exploring
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UNIT C
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Skills You Will Use The Sombrero galaxy contains more than 100 billion stars. The oldest stars are in the central bulge. New stars are still forming in the dust lanes, which lie in a ring around the centre.
In this chapter, you will: • use appropriate terminology related to the study of the universe • represent the distance of stars from Earth using scientific notation • compare and contrast properties of celestial objects visible in the night sky by researching and analyzing information
Concepts You Will Learn In this chapter, you will: • describe the major components of the universe, using appropriate scientific terminology and units • describe the observational and theoretical evidence relating to the origin and evolution of the universe
Why This Is Important Throughout their lives, most people ask themselves three key questions: Where did I come from? Where am I now? Where am I going? These questions can also be asked of our entire world, Earth. Assessing scientific evidence for how and when the universe formed and continues to change can help us find some answers to these questions.
Before Reading Making Connections to Prior Knowledge Skim the titles, subheadings, and illustrations of section 7.1 to get a sense of the key ideas. Scan for terms that you know. Use familiar ideas and terms to create a mind map that connects all of your knowledge about space and the universe. What you know already will help you connect to new information and ideas.
Key Terms • astronomy • astronomical unit • Big Bang theory • celestial objects • galaxy • light-year • nebula • nuclear fusion • solar system • star • supernova
Scientific evidence suggests that the universe began expanding from a single point about 13.7 billion years ago.
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Space Flight to the Stars
Here is a summary of what you will learn in this section: • Astronomy is the study of the universe and the celestial objects in it. • The solar system is composed of the Sun, four rocky inner planets, four gas giant planets, and other objects such as asteroids, comets, and moons. • An astronomical unit (AU) is a measure of distance, equal to the average distance from the Sun to Earth. • A light-year (ly) is a measure of distance, equal to the distance light can travel in 1 year. Figure 7.1 The Milky Way galaxy looks like a smudge in the sky shown above. The brightest point to the left is the planet Jupiter.
Looking Back in Time
W O R D S M AT T E R
“Astron” is the Greek word for star, and the suffix “-nomy” means science or study of. So, astronomy is literally the study of the stars.
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In all societies, people have looked at the night sky for inspiration, to find directions, to decide when to plant or harvest crops, or just to appreciate its great beauty (Figure 7.1). “Celestial” is a term that refers to the sky. Objects we can see in the sky are called celestial objects. The Sun, the Moon, Earth, other planets, and comets are all examples of celestial objects. Astronomy is the study of the universe and the objects in it. An astronomer is a person who studies astronomy. At one time, astronomers had only two aids to help them understand celestial activity: sharp eyesight and a practical knowledge of mathematics. These days, highly powerful and sensitive instruments enable us to peer farther and farther out into the universe and to gather information about the celestial objects in it. Supercomputers can analyze the incoming data from 100 000 stars at the same time. When astronomers look at a faraway celestial object, the distance they are looking across is so vast that they are really looking back in time. Light takes time to travel. When you look at your hand, for instance, you see it not as it is, but as it was a few billionths of a second ago. At short distances, this delay does not make a difference. However, when you are looking out into space,
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the delays begin to add up. For example, it takes about 1.5 s for the light to reach Earth from the Moon (Figure 7.2). We therefore always see the Moon as it was 1.5 s ago. The planet Jupiter, farther from Earth than the Moon is, appears to us as it did 45 min before.
Figure 7.2 The Moon over Toronto
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Quick Lab
A Map of the Universe Purpose To list all the objects you know of that exist in the universe and then to show their relationships to each other by arranging them on a map
Materials & Equipment
and continues to the most distant reaches of the universe away from Earth (or as far out as you know about). If you know the shape of each object or a symbol to represent it, draw that. Do not concern yourself with trying to make your map to scale. Label each object.
• poster paper or newsprint
A Map of the Universe (not to scale)
• felt pens Earth
Most Distant from Earth
Procedure 1. Working in pairs or a small group, brainstorm a list of all the different kinds of objects you know about in the universe. Examples include planets, comets, and stars. Write these down the side of a sheet of poster paper.
Figure 7.3 Step 2
4. Post your map on a wall in the classroom.
Questions
2. Copy the labels shown in Figure 7.3 onto the sheet of paper.
5. Compare your map with that of other groups. How do they differ? How are they similar?
3. Arrange the objects in the order you might encounter them on a trip that begins at Earth
6. Were there any new objects that you learned about during this activity? If so, what were they?
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During Reading Using Prior Knowledge Think about holidays or road trips you have taken. What were the destinations? What preparations did you make? How long was each journey? Now, for an imaginary voyage out among the stars, think about the preparations and travel details you would need to consider.
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From Earth to the Stars of the Milky Way Imagine that we could travel from Earth out among the stars in our Milky Way galaxy. In reality, a journey to other stars is impossible. The distances are much too great between objects and our lives are much too short to enable us to make such a journey. Still, an imaginary trip like this is a good way to let us examine much of what has recently been learned about the universe. We would start the trip by heading out into the solar system. The solar system is the Sun together with all the planets and other celestial objects that are held by the Sun’s gravitational attraction and orbit around it (Figure 7.4). Among the other celestial objects in the solar system are moons, comets, and asteroids. Chapter 8 describes these objects in more detail.
Figure 7.4 A comparison of the orbits of the eight planets in the solar system
Earth Mercury
Venus Mars
Saturn
Jupiter Uranus Neptune
The Sun and Inner Solar System
Figure 7.5 An astronaut’s footprint on the Moon’s surface
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Leaving Earth on our imaginary journey, we first encounter the Moon. Twelve people have walked on the Moon, the last time in 1972. With their Apollo spacecraft travelling about 30 times the speed of a jet airplane, the astronauts’ trip to the Moon took four days. The Moon is smaller than Earth and has no atmosphere and little or no water. Thus, a footprint left by an astronaut can last for an indefinite length of time (Figure 7.5). As the Moon orbits Earth, it rotates at a speed that keeps the same side always facing Earth. The first and so far only people to see the far side of the Moon directly were the astronauts who flew there during the Apollo missions of 1968 to 1972.
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Beyond the Moon is the rest of the solar system. At the centre of the solar system is the Sun, which is a star. A star is a hot ball of plasma, an electrically charged gas, that shines because nuclear fusion is taking place at its core. Nuclear fusion is the process in which the nuclei of atoms fuse together and form larger atoms. During this process, an enormous amount of energy is released. Between Earth and the Sun are two planets, Mercury and Venus (Figure 7.6). Turning and travelling away from the Sun, out past Mercury, Venus, and Earth, we next come to Mars, the last of the four rocky planets that make up the inner solar system (Figure 7.6).
W O R D S M AT T E R
Plasmas are a fourth phase of matter, in addition to solids, liquids, and gases. A plasma is made up of charged particles. Flames, lightning, the aurora borealis, the neon in neon lights, and stars are all examples of plasmas. This use in physics of the word plasma comes originally from the medical world, where the term refers to the colourless fluid part of the blood.
Figure 7.6 The four rocky planets of the inner solar system. Only Mars has some similarity to Earth in terms of temperature and gravity.
Measuring Distances in Space Leaving the inner planets of the solar system, the distances we begin to travel become nearly impossible to envision. So vast are the distances in space that astronomers have had to develop special units of measure. Just as you would not find it practical to measure the length of your school gymnasium in millimetres, astronomers quickly learned that measuring distances in the solar system in kilometres was not practical. For this reason, the astronomical unit was created. One astronomical unit (AU) equals the average distance between the Sun and Earth, about 150 million km. For example, the planet Mercury is 0.39 AU from the Sun. This value is less than 1 AU because Mercury is closer to the Sun than Earth is. Mars is farther from the Sun than Earth is. Its distance is 1.52 AU. Outside the solar system, the distance to other celestial objects again becomes so great that even the AU is too small to be a useful unit of measure. For these immense distances, astronomers usually use a distance measure called the light-year. One light-year (ly) equals the distance that a beam of light can travel through space in 1 year. It is equivalent to 63 000 AU or 9000 billion km. At the speed of light, you could travel around Earth seven times in 1 s. A trip from the Sun to Neptune at the speed of light takes about 5 h. Scientific evidence suggests that the universe began expanding from a single point about 13.7 billion years ago.
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The Outer Solar System Out past Mars, we encounter the asteroid belt, a region of rocky debris that forms a ring all the way around the Sun at a distance of about 3 AU. The asteroid belt contains billions of pieces of rock of all sizes. Some of these chunks are smaller than a grain of sand. Others are huge. The largest is about 1000 km across, which is equal to the distance from Ottawa to Thunder Bay. Beyond the asteroid belt lie the four gas giant planets: Jupiter, Saturn, Uranus, and Neptune (Figure 7.7). Jupiter is so large that several thousand Earths could fit inside it. The gas giant planets do not resemble Earth at all. Their atmospheres are made mostly of hydrogen and helium. The planet farthest out in the solar system is Neptune, in orbit 30.1 AU away from the Sun. Figure 7.7 The four gaseous
planets of the outer solar system, shown here with the Sun in the background for scale. Had Jupiter been a little larger, nuclear fusion might have started in its core and Jupiter might have become a star.
Jupiter
Saturn
Uranus
Neptune
Many more objects exist in the solar system besides the eight major planets. These are smaller and include moons, comets, minor planets such as Pluto, and tiny grains of dust and ice. Some objects held in the Sun’s gravitational grip orbit as far as 50 000 AU away, which is one-quarter of the way to the next nearest star.
Learning Checkpoint 1. What is the solar system? 2. (a) How are an astronomical unit and a light-year similar in terms of what they measure? (b) Which is the longer distance, 1 AU or 1 ly? 3. (a) What is a star? (b) Name the closest star to Earth.
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To the Stars With enough time and a fast enough spacecraft to transport us on this imaginary journey, we would eventually travel among the stars. The next nearest star to Earth after the Sun is actually part of a group of three stars that orbit each other. This group is called the Centauri system (Figure 7.8). It lies about 4.3 ly away from the solar system. If it were possible for you to have a cellphone conversation with someone living near these stars, just saying hello to each other would require more than 8.5 years. That is how long it would take the radio signal, moving at the same speed as light, to travel to the Centauri system and back again to Earth. As we continue our voyage out farther through deep space, we would start to notice that well over half of the star systems have two or more stars. A system with two stars is called a binary system (Figure 7.9). If the stars are close together, it might be possible for planets like ours to orbit all the way around both of them. Some astronomers suggest that Earth-like planets orbiting around tightly bound binary stars might be more common than our own one-star arrangement. Although the stars in the Centauri system may be the closest to Earth after the Sun, none of them is the brightest star we can see at night. The title of “brightest star visible from Earth” goes to Sirius, even though it is nearly twice as far from us as the Centauri system is. Sirius is brighter because it is a different kind of star than the Centauri stars. Sirius is about twice the mass of our Sun.
Figure 7.8 The Centauri system. Earth’s nearest star after the Sun is part of this system.
Suggested Activity • C4 Quick Lab on page 266
Exploding Stars During this journey, you might also see a star explode. If so, you should hope that the explosion occurs at least 100 ly away from the region of space you are travelling through. When a star explodes, it is called a supernova. A star might exist for millions or even billions of years and then suddenly come to an end in a few minutes. The gradual build-up of heavy elements in the star's centre causes the core to collapse. Figure 7.9 Albireo is an example of a binary star system. When viewed by the unaided eye, Albireo looks like a single star. A telescope shows that it is really made up of two stars, shown clearly here. Scientific evidence suggests that the universe began expanding from a single point about 13.7 billion years ago.
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Figure 7.10 In 1987, Canadian astronomer Ian Shelton photographed the explosion of the brightest supernova seen by anyone since the invention of telescopes. The images here show supernova 1987A before the explosion (a) and after (b).
(a)
Figure 7.11 The Crab Nebula
Figure 7.12 These petroglyphs (rock drawings) on the walls of Chaco Canyon in Arizona record the supernova event that created the Crab Nebula.
Take It Further Supernova 1987A, first spotted by Canadian astronomer Ian Shelton, was studied for many weeks after the event by astronomers around the world. Find out what was learned about stars from the observations made of supernova 1987A. Begin your research at ScienceSource.
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(b)
When this happens, the outer layers of the star are pulled into the core by gravity. As the outer material crashes into the inner core, the temperature and pressure increase and the star explodes (Figure 7.10). High pressures and temperatures created during the supernova explosion lead to the formation of new elements. As the star rips apart, debris from the explosion provides the matter for another type of celestial object, a nebula. A nebula is a large cloud of dust and gas. Nebulae are often called star nurseries, because it is from their dust and gas that stars develop. Figure 7.11 shows the Crab Nebula, whose beginning was observed and recorded by many observers on Earth in 1054. Among those were Arab and Chinese astronomers, as well as Aboriginal peoples in North America (Figure 7.12). Stars capable of becoming supernovas are rare right now in the region of space nearest Earth. This is fortunate because a supernova explosion anywhere within 100 ly of Earth would roast the planet. Yet, in the wide expanse of the universe, they are very common. If we had a very sensitive telescope that could look in all directions of the visible universe at once, we could expect to see a supernova explosion every few seconds. Currently, about one supernova a week is detected by telescopes that are based in orbit and can scan deep space.
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The View Back to Earth So far, our trip has taken us past about 100 billion stars. If we looked back at them, we would see that most seem to be part of a thin disk, 100 000 ly across and swirling around a common centre. This group of stars is our galactic home, the Milky Way. We cannot see the entire Milky Way directly because the solar system is inside it. However, if we could, it would look something like the collection of stars in the Pinwheel galaxy (Figure 7.13). A galaxy with this shape is known as a spiral galaxy. Figure 7.13 The Pinwheel galaxy, which has a similar shape to our galaxy, the Milky Way
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Just-in-Time Math
Scientific Notation Whether we are counting numbers of stars in a galaxy or the distance from the Sun to the next nearest star, we often deal with extremely large numbers. Scientific notation helps to make very large numbers shorter and easier to handle. Scientific notation is based on powers written using the base number 10. For instance, using scientific notation to write the number 321 000 000 000 results in 3.21 × 1011. The first part of the number (in this case, 3.21) is always greater than or equal to 1 but less than 10. The second part of the number is a power with base 10 and an exponent number (in this case, 11, written in superscript, raised and set up to the right of the 10).
Step 2: Count the number of places from the decimal point to the end of the zeros. For 2.99 800 000, there are eight places. This means the power of base 10 has an exponent of 8, written as 108. Step 3: Delete the zeroes. The number written in scientific notation is 2.998 × 108 m/s. Write the following numbers in scientific notation: 1. the distance from the Sun to the nearest star: 40 000 000 000 000 km 2. the average distance from Earth to the Sun: 150 000 000 000 m 3. the distance from the Milky Way to the farthest galaxies: 13 000 000 000 ly
Example: The speed of light is about 299 800 000 m/s. Write this in scientific notation.
4. the total number of celestial objects (mostly asteroids) in the solar system: 152 500
Step 1: Put a decimal point after the first digit on the left. This gives 2.99 800 000 for the example.
5. the mass of the Sun: 1 990 000 000 000 000 000 000 000 000 000 kg 6. the age of Earth: 4 550 000 000 years
Scientific evidence suggests that the universe began expanding from a single point about 13.7 billion years ago.
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All These Worlds In addition to the eight major planets in the solar system, astronomers have already identified more than 300 planets orbiting stars other than the Sun. The question of whether there might be other life forms living in distant worlds is clearly related to the question of how many other worlds there might be. Most of the planets astronomers have already detected appear to be gas giants, not smaller rocky planets like Earth. We do not know whether this is because rocky planets are uncommon or because they are smaller and harder to detect. In this activity, you will make a conservative estimate of the number of Earth-like planets likely to exist in the universe. A conservative estimate is a rough calculation in which assumptions are made that tend to underestimate how many of something there are. When you arrive at your conservative estimate, you can then say “There are at least this many, and probably there are more than this amount.” Listed in the next column are a number of assumptions for you to consider in finding your result.
Purpose To make a conservative estimate of the number of planets in the universe that resemble Earth, and to compare that number to the number of people on Earth
Materials & Equipment • calculator
Assumptions In the Hubble Ultra Deep Field image shown at the start of this unit, a computer counted the galaxies and determined there to be about 35 000, or 3.5 x 104. The patch of sky viewed in the Hubble Deep Field is small, the size of the head of a pin held at a distance of 1 m. The number of pin heads needed to cover the inside of a sphere 1 m in radius is approximately 13 million, or 1.3 x 107. A typical galaxy has 200 billion stars, or 2 x 1011. Assume (conservatively) that 1 star in every 100 has a planet around it, or 0.01 of stars has a planet. Assume that of stars that have planets, only 1 in 1000 has an Earth-like planet around it, or 0.001 of stars has an Earth-like planet.
2. Using a calculator, combine the above terms by multiplying them together. When you get your result, check it with that of other students.
Questions 3. The human population of Earth is about 7 billion people (7 x 109). Divide your result in step 2 by the population of Earth to estimate how many Earth-like planets there are in the visible universe for every man, woman, and child on Earth. 4. Do the above calculations affect your assessment of whether there are other forms of life in the universe? Explain.
Procedure 1. Working individually or in a small group, read the assumptions in the next column. Modify them if you can think of different ones that seem reasonable, but be prepared to explain any changes.
Figure 7.14 A tiny portion of the universe revealed by the Hubble Space Telescope
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CHECK and REFLECT
Key Concept Review 1. List five different types of celestial objects in the solar system. 2. What is a star? 3. What happens in the core of a star that causes it to shine? 4. (a) Define astronomical unit. (b) What is 1 AU equal to in kilometres? 5. (a) Define light-year. (b) What is 1 ly equal to in astronomical units?
12. (a) Calculate how many years it would take a spacecraft to travel the 150 000 000 km distance between Earth and the Sun if the travel speed were 1000 km/h. (b) Using the answer you got for (a), calculate approximately how long it would take that same spacecraft to make a one-way trip from the Sun to Neptune. 13. The star Aldebaran, visible from Earth, lies about 65 ly away from us. What is the minimum amount of time that would be required to send a message to Aldebaran and receive a reply (assuming someone was there to receive it and respond)?
6. Name the four planets that lie beyond the asteroid belt, in order from closest to farthest from the Sun. 7. Binary systems account for approximately what proportion of star systems in the universe? 8. What is the relationship between a supernova and a nebula?
Connect Your Understanding 9. Explain why looking at an object, whether it is your hand or a distant star, is like looking back in time. 10. Several astronauts have flown to the Moon and even walked on its surface. Yet, a flight from Earth out to the stars in the Milky Way galaxy can only be imagined. Explain why that is. 11. Why are astronomical units not used for measuring distances between celestial objects that lie outside the solar system?
Question 13
14. Explain why scientific notation is useful for expressing many properties of celestial objects, such as the distance from Earth to the stars in the Milky Way galaxy.
Reflection 15. Many of the activities in this unit, such as the Quick Lab at the beginning of this section (C2, A Map of the Universe), suggest that you brainstorm in a small group or even as a class. What benefits do you think such a group approach offers in terms of helping to advance ideas about a topic? For more questions, go to ScienceSource.
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Galaxies
Here is a summary of what you will learn in this section: • Galaxies contain about 200 billion stars each and usually have a supermassive black hole at their centre. • At least 90 percent of the mass in the universe may be composed of dark matter. • Galaxies come in many shapes including spiral, barred spiral, elliptical, and irregular. • Galaxies are often bound together in clusters. Clusters are often associated with other clusters.
Figure 7.15 A panoramic view of the night sky, featuring the Milky Way over the desert near Death Valley, California
W O R D S M AT T E R
The word “galaxy” comes from an ancient Greek word galaktos, meaning milk.
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Our Solar System: A Speck in the Milky Way Figure 7.15 shows a panoramic view of the Milky Way as seen from Earth. The picture, which compresses the entire night sky into a rectangle, was made by combining 30 images. Taken in the middle of a desert far from artificial lights, these images capture the brilliance of the night sky that is not usually visible to most people. The band of light arching across the sky in the composite photograph is actually a straight line. It looks curved because of the way the images were combined. The band is the result of the billions of stars that lie between Earth and the centre of the Milky Way, which is seen edge-on in the image. The dark smudgy line along the band is dust. This dust obscures our view into the centre of the galaxy. However, we are able to view stars at the very centre of our galaxy by using telescopes that detect infrared light (heat) rather than visible light.
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Our galaxy is about 100 000 ly in diameter and about 2000 ly thick at its widest point, near the core (Figure 7.16). Such a size is very difficult to imagine. The solar system, which is enormous compared to the size of Earth, is very tiny compared to the whole Milky Way galaxy. While light from the Sun takes about 5 h to reach the most distant planet in the solar system, Neptune, that same beam of light would take 100 000 years to cross the entire Milky Way. Another way to try to picture the size of our galaxy is to imagine the solar system was reduced to the size of a single bean. By comparison, the Milky Way would be slightly larger than the area of Lake Superior.
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100 000 ly Milky Way
Sun
core
disk
Figure 7.16 A top view and a side view of the Milky Way galaxy
Quick Lab
Hunting for Galaxies in the Hubble Ultra Deep Field Galaxies occur in many shapes and sizes. The Hubble Ultra Deep Field image reveals several thousand galaxies, providing a good sample of what is “out there.” By identifying and counting different shapes of galaxies, you will become more familiar with the variety that occurs in the universe.
Purpose To identify and classify some of the many galaxies found in the Hubble Ultra Deep Field image
Materials & Equipment • handout showing galaxies of different shapes • calculator
Procedure
3. Record your results. Some galaxies will appear as a tiny dot, too difficult to classify. Count as many of those as you can and record them as “unclassified.”
Questions 4. Based on your analysis, which type of galaxy is the most common and which kind is the least common? 5. Estimate the number of galaxies that were too small to classify compared with the number that you could classify. Add up the total number of galaxies that you looked at, including those labelled as “unclassified.” 6. Calculate the percentage of each type of galaxy, including unclassified galaxies, in your study.
1. Your teacher will give you a handout showing galaxies of several different shapes.
7. Arrange your classification from highest percentage to lowest percentage.
2. Study the image of the Hubble Ultra Deep Field shown in the Exploring section of this unit. Using the handout to help you, identify as many different kinds of galaxies as you can.
8. Suggest why some galaxies appeared large enough to classify, while others were too small.
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Properties of Galaxies Suggested Activity • C7 Quick Lab on page 276
All galaxies contain stars, planets, and dust. Galaxies with more dust than others tend to produce more new stars, because stars form from dust and gases present in nebulae. Some galaxies, thought to be very ancient, have almost no dust because it has all been used up in star-making. The farthest galaxies we can see may also be the oldest, because the light has taken so long to reach us. Astronomers think that the stars of these galaxies were possibly larger than the largest stars that exist today. If that was the case, then those stars lived short, hot lives, usually ending in supernova explosions. Gravity pulled the material together again, repeating the cycle of star formation, explosion, and spreading of new elements into space.
Black Holes Through studies of hundreds of thousands of galaxies, astronomers now believe that each galaxy contains at least one supermassive black hole at its centre (Figure 7.17). A black hole is a region of space where gravity is so strong that nothing, not even light, can escape. The evidence for the existence of black holes is strong. For example, at the centre of the Milky Way, a number of stars can be seen rapidly orbiting around a point in space that seems to have nothing in it. At this spot is almost Figure 7.17 Artist’s concept of a certainly a black hole. black hole The main way that a black hole affects its surroundings is through its tremendous gravitational pull. Its gravity is so strong that it can pull a star right into it (Figure 7.18). This completely destroys the star. However, the mass of the star adds to the black hole’s original mass, increasing the size of the black hole. It has been estimated that the Milky Way’s black hole has been pulling stars in for at least 7 billion years. Currently, the black hole has a mass equal to about 3 million stars that are of Figure 7.18 A region of space containing a black hole, as photographed by the Hubble Space Telescope similar size to our Sun. 270
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Astronomers speculate that when galaxies collide, the black hole at the centre of each one gradually moves toward the other. After hundreds of millions of years, they will merge, with their masses combining into a single supermassive black hole. Figure 7.19 shows the two black holes at the centre of a galaxy that resulted from the collision of two smaller galaxies.
Dark Matter Although there are billions of celestial objects in space, even more astounding is that astronomers speculate that those objects add up to less than 10 percent of Figure 7.19 In the central region of galaxy NGC 6240, two black holes the total matter in space. At least 90 percent of the universe may are visible (shown here in blue). be filled with matter that is not even visible. Astronomers have This galaxy was formed by two small named this dark matter. Dark matter refers to matter in the galaxies colliding. universe that is invisible because it does not interact with light or any other kind of radiation. Because of this, dark matter is During Reading invisible to direct observation by telescopes. Using Prior Knowledge If dark matter cannot be seen, then why would astronomers How have scientists used their think it is there? The answer is that they have detected its prior knowledge to define dark presence indirectly. matter? Write down three key Astronomers have long been puzzled by the unexpected motion statements that define or of many galaxies. It appears as though gravitational forces are describe dark matter and its affecting them, yet the amount of visible mass (such as stars, characteristics. moons, gas, and dust) does not seem to be enough to do that. For example, the stars in the Milky Way revolve around the galaxy’s centre at such high speed that we would expect them to be flung off, just like a spinning water sprinkler sends drops of water flying out in all directions. The Milky Way is not coming apart, however. Instead, as astronomers have concluded, it is being kept together by the gravitational force of an enormous amount of matter that we cannot see directly (Figure 7. 20). Today, most of the Figure 7.20 By observing how matter in this galaxy cluster bends light gravity in the universe is thought to be rays, astronomers were able to compute and map out where they believe the dark matter (shown by the dark blue ring) is distributed in the cluster. produced by dark matter. Scientific evidence suggests that the universe began expanding from a single point about 13.7 billion years ago.
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Star Clusters
Figure 7.21 A globular cluster of stars
Galaxies also contain distinct groupings of stars known as star clusters. A star cluster is a concentration of stars in a relatively small region of space. Star clusters occur in two broad types. One is an open cluster, which contains a few hundred to a few thousand stars. Open clusters are among the youngest star groups in a galaxy. The other type of star cluster is a globular cluster, which contains hundreds of thousands of stars, drawn together in a spherical form by the stars’ gravity (Figure 7.21). Globular clusters are the oldest star groups in a galaxy.
Galaxy Shapes Galaxies are commonly classified according to four main shapes: spiral, barred spiral, elliptical, and irregular.
Spiral and Barred Spiral Galaxies Spiral galaxies are named for the spiral-shaped arms that radiate out from the galaxy’s centre (Figure 7.23(a)). About half of all spiral galaxies, including the Milky Way, have what appears to be a bar across them (Figure 7.22). These are called barred spiral galaxies. A wave moving outward from the central regions of the galaxy causes the gas and dust to compress into arm-like bands that Figure 7.22 The barred spiral galaxy known as NGC 1300 rotate around the central hub (Figure 23(a)). New arms continually form as older ones disappear or change shape. Gravity keeps the spirals from flying apart. A typical spiral galaxy completes a full rotation once about every 300 million years. From the side, a spiral galaxy looks like a thin disk (Figure 7.23(b)). The disk is difficult to see through because of all the dust and gases between the stars. If you know how smog in a city or smoke from a forest fire makes it hard to see clearly into the distance, you will get an idea of how the view can be obscured. It is in these dusty regions that new stars form. Most (a) (b) spiral galaxies have hundreds to Figure 7.23 Two spiral galaxies: (a) galaxy M81 shown from the top; thousands of star clusters. and (b) galaxy NGC 5746 shown from the side 272
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The disk of a spiral galaxy is not completely flat. Near the core is a widening called the central bulge. It consists mainly of very old stars. New stars rarely form here because of the lack of dust and gases between the stars. Surrounding the central bulge and most of the disk is the galactic halo. The halo is also made up of individual stars.
Elliptical Galaxies An ellipsoid is a shape like a flattened sphere. Elliptical galaxies are those whose shape ranges from almost spherical to football-shaped (Figure 7.24) or long and cylindrical, like a pencil. Such galaxies are thought to result when other galaxies, such as spiral galaxies, merge. The largest galaxies in the universe are elliptical. Elliptical galaxies contain very little dust. This means they have fewer young stars than spiral galaxies do. Many of the stars in elliptical galaxies are extremely old.
Figure 7.24 The bright patch at the upper centre of this image shows the giant elliptical galaxy ESO 325-G004.
Irregular Galaxies Some galaxies are neither spiral nor elliptical. Those without a regular shape are called irregular galaxies (Figure 7.25). The distorted form of an irregular galaxy may result because the galaxy collided with another one or got close enough that the gravitational force from the other galaxy drew stars away. Figure 7.25 The irregular galaxy known as NGC 1427A
Learning Checkpoint 1. What is a galaxy? 2. What is thought to be at the very centre of all galaxies? 3. What is dark matter? 4. Sketch the general shape of a spiral galaxy as viewed from the side and then as viewed from above. 5. State one possible way that elliptical galaxies form.
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Take It Further As better telescopes are developed, we continue to discover galaxies that are farther and farther away. The most distant galaxy discovered so far is called 10K-1. It was spotted by the Subaru telescope in Hawaii in 2008. It is 12.8 billion ly away. Find out more about this galaxy, the oldest one yet discovered. Begin your research at ScienceSource.
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Galaxy Clusters Many of us have played the game of writing out our full address, from the street name and number to the city or town, province, country, Earth, and finally Milky Way. In fact, your universe address does not end there. If you could get out beyond our own galaxy and look back at it, you would see that the Milky Way is part of a group of about 20 galaxies. Such a group is called a galaxy cluster, and the one containing the Milky Way is known as the Local Group (Figure 7.26). More than 2000 billion stars lie inside the cluster. The Local Group is part of the Local Cluster of galaxies, and that in turn is part of the Local Supercluster.
Local Supercluster Solar System
Local Cluster
Milky Way Galaxy
Local Group
Figure 7.26 Galaxies tend to occur in groups called galaxy clusters. Galaxy clusters in turn form groups called superclusters. According to astronomers, there may be more than 100 billion galaxies in the universe.
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Mapping the Visible Universe Gone are the days when astronomers had to count stars or galaxies one by one. Now, a great wedge of sky can be surveyed and galaxies counted by computer. Figure 7.27 shows two wedges from a recent galactic survey. At the centre is the Milky Way galaxy. Studies such as this do more than just make a map of places we can never expect to travel. It is from the study of galaxies and their motions that astronomers have been able to find answers to questions about the origin of the universe.
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Figure 7.27 Two wedges of sky showing the positions of nearly 107 000 galaxies out to a distance of 5 billion ly
Just-in-Time Math
Math Scaling A mathematical scale is a ratio between units of measure. Scales are used to show something in larger or smaller form, but in the same proportions as the original thing is. If you wanted to map your neighbourhood on a page in your notebook, you would have to create a scale to show the relative distances between streets and buildings accurately. For instance, you might choose to set your scale at 1 cm = 50 m or 1 cm = 200 m.
Step 2: Simplify the left side by cancelling the units and doing the division.
Because distances in space are so vast, they can only be represented by scaling.
The model scale distance is 5 m.
Example: Imagine you are building a scale model to show the distance from Earth to the Andromeda galaxy and Magellanic galaxy NGC 2366. Say you know the real distance to the Andromeda galaxy is 2.5 million ly and its model distance is 1 m. You want to determine the model distance x for the Magellanic galaxy whose real distance is 12.5 million ly. Step 1: Write an equation that compares the real distances on the left side with the model scale distances on the right side. x 12.5 million ly = 1m 2.5 million ly
5.0 =
x 1m
Step 3: Multiply both sides by 1 m. 5.0 × 1 m = x 5.0 = x
Solve the following scale distances (x): 1. The distance from your home to a store is 2 km. The scale distance is 10 cm. The distance from your home to a library is 3 km. What is the scale distance to the library? 2. The distance from the Sun to Earth is 1 AU and from the Sun to Jupiter is 5.2 AU. The scale distance from the Sun to Earth is 8 cm. What is the scale distance to Jupiter from the Sun? 3. The scale distance between the Milky Way galaxy and the Andromeda galaxy is 20 cm = 12.5 million ly. What is the scale distance to the Sombrero galaxy, 29 million ly away?
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Quick Lab
Modelling the Distances to Galaxies The distance from the Milky Way to even its nearest neighbouring galaxy, Andromeda, is vast: 2.5 million ly. Yet, compared with the distances to other galaxies in the universe, Andromeda seems right next door to us. In this activity, you will create a scale and plot the distance to several galaxies on a local map, setting the distance from the Milky Way to Andromeda at 1 m.
Table 7.1 Seven Galaxies and Their Real and Model Distances from the Milky Way
Appearance
Distance (ly)
Model Distance (m)
Andromeda galaxy
2.5 million
1
Magellanic galaxy NGC 2366
12.5 million
5
Sombrero galaxy
38 million
15
Antennae galaxies
90 million
?
Seyfert’s Sextet
190 million
?
Cartwheel galaxy
620 million
?
Galaxies in Hubble Deep Field
10 000 million
?
Galaxy
Purpose To create a model that shows the distance from the Milky Way to seven other galaxies
Materials & Equipment • paper or notebook • photocopy of a map of the local area around your school • calculator • ruler • markers
Procedure 1. Copy the data from Table 7.1 onto a piece of paper. 2. Using the data provided in the first three rows, estimate the model distance for the remaining four galaxies and record these distances in the table. 3. Mark an X at any point on the map of the school area to represent Earth (or the Milky Way galaxy). Label it. 4. Following the map’s scale, measure 1 m on the map in any direction and plot this second point. Label it Andromeda galaxy. 5. Continue plotting all but the galaxies shown in the Hubble Deep Field photograph. The direction to each galaxy is not important for this activity, just the distance.
Question 6. Estimate how far your map would have to extend to include the galaxies in the Hubble Deep Field. 276
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CHECK and REFLECT
Key Concept Review 1. Why do galaxies with more dust than other galaxies generally produce more new stars?
12. Explain why our night sky would not be dark if the Sun were located inside a star cluster such as that one shown in the image below.
2. What is the diameter and thickness of the Milky Way in light-years? 3. Earth is estimated to be about 35 000 ly from the black hole at the centre of the Milky Way. Several stars have been observed to orbit the black hole. How long would it take light from these stars to reach Earth? 4. (a) What is a black hole? (b) Are they rare or common? Explain your answer.
Question 12
5. What do astronomers speculate makes up at least 90 percent of the matter in the universe?
Reflection
6. Name the four main types of galaxy according to shape.
13. How have your ideas about the size and structure of galaxies been changed by what you read in this section? Explain.
7. Make a simple diagram to show the relationship between the Milky Way galaxy and the Local Supercluster of galaxies.
Connect Your Understanding
14. Think of a way you could visually model what you have learned about the extent of the Milky Way galaxy to educate someone who knows little about it. For more questions, go to ScienceSource.
8. Even when two galaxies collide, why do very few of their stars collide with each other as well? 9. How is it possible to detect the black hole at the centre of the Milky Way if the black hole itself is invisible? 10. The stars are held together in our galaxy by gravity. List three main sources of this gravity. 11. Spiral galaxies may be younger than other types of galaxies, still spinning from the time of their formation. How might an irregular galaxy or an elliptical galaxy form from one or more spiral galaxies? Scientific evidence suggests that the universe began expanding from a single point about 13.7 billion years ago.
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The Expanding Universe
Here is a summary of what you will learn in this section: • Evidence suggests that the universe began 13.7 billion years ago at a single point and has been expanding since. • The red shift of spectral lines in the light we see from galaxies shows that the light’s wavelengths are getting longer. This indicates that the galaxies are moving away from us. • The Big Bang theory of the formation and expansion of the universe is consistent with known laws of the universe. • The cosmic background radiation in the universe, now mapped, is thought to be leftover energy from the moment the universe first formed.
Figure 7.28 The Hubble Space Telescope was named for astronomer Edwin Hubble.
Hubble’s Ideas Edwin Hubble was an American astronomer who was one of the first scientists to study galaxies (Figures 7.28 and 7.29). Between 1918 and 1929, two of his major findings changed astronomy. First, he confirmed that many other galaxies existed beyond the Milky Way. Second, he found that almost all galaxies are moving away from each other. These observations helped to support the proposal made in 1927 by Belgian priest and physicist Georges Lemaître that the universe is expanding. The evidence Hubble used to reach his conclusions came from measuring the distance from Earth of 46 galaxies and the speed of their movement. After collecting the light from these galaxies, Hubble closely examined each one’s light spectrum. The visible light spectrum is the rainbow band of colours into which white light separates when it passes through a prism.
Figure 7.29 American astronomer Edwin Hubble (1889–1953) using the 100-inch (250-cm) telescope at the Mount Wilson Observatory, Los Angeles, California, in 1937
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In the years since Hubble’s first measurements, evidence from observations of thousands of galaxies has confirmed his early findings. Hubble’s work and ideas remain the foundation of modern understanding of the nature and origin of the universe.
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A “spectrum” in science refers to the separation of radiation, such as light into different wavelengths. When this happens in our sky, we call it a rainbow. This is pluralized as spectra, or sometimes as spectrums.
Quick Lab
Comparing Light Spectra Each kind of light source has its own unique spectrum. By studying different light spectra, it is possible to tell a lot about the properties of the sources that produced them, even if those sources are extremely far away. A device called a spectroscope enables us to split a light sample into its spectral colours. We can then record and analyze the spectrum’s pattern.
Purpose To use a spectroscope to observe and compare the spectra of a variety of light and gas sources
Materials & Equipment • spectroscopes • variety of light sources (for example, incandescent, fluorescent, holiday lights, sunlight) • gas discharge tubes (for example, hydrogen, mercury, sodium) • notebook and pencil
3. Next, take turns observing the spectrum of each element in the various gas discharge tubes. Record what you observe about each spectrum for each tube source you view.
Questions 4. What differences did you notice about the spectra for the different light sources? 5. (a) Which kind of light source produced the most distinct spectrum of all the sources? (b) Explain why you think that was the case. 6. How did the spectra from the gas discharge tubes differ from the spectra displayed by the light sources? 7. How could knowledge of the spectra of light created by particular elements help an astronomer determine the composition of a distant star or galaxy?
CAUTION: Never touch the ends of a spectroscope’s power supply when it is in use. Tubes can become extremely hot when in use.
Procedure 1. Your teacher will set up a number of light sources and spectroscopes in the lab or classroom. 2. In small groups, take turns observing the spectrum of each light source. Record what you observe about each spectrum for each light source you view. Figure 7.30 This student is using a spectroscope to observe the spectrum of the element hydrogen.
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During Reading Connecting the Known to the New As you read the text under each subheading, write in your notebook one thing you already know about the topic, two pieces of information that are new to you, and one question you still have about the topic.
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Evidence for the Big Bang Theory From the light spectrum of each galaxy he studied, Hubble was able to figure out the speed at which each galaxy was moving away from our own. Then, for those same galaxies, he separately determined the distance between each one and the Milky Way. Plotting both the speed and the distance measurements together, Hubble discovered a clear relationship between the two. The farther away a galaxy was, the faster it was moving away. These findings, along with observations of many other scientists of the time, gave further support to Lemaître’s idea that the universe is expanding. Out of this and the work of many other physicists, mathematicians, and other scientists of the day developed one of the most remarkable theories of the 20th century. The theory, which came to be called the Big Bang theory, states that the universe formed when an infinitely dense point suddenly and rapidly expanded in a single moment. All the matter and energy that exists today was created during the early minutes of that hot, rapid expansion. Credit for the Big Bang theory goes mostly to Russian-American physicist George Gamow and American mathematician Ralph Alpher. It is now commonly accepted by scientists that the universe formed 13.7 billion years ago. That moment marks the beginning of the universe and also the beginning of time. Today, at several research facilities around the world, scientists are trying to re-create, in a small way, various aspects of the conditions that might have existed in the early moments of the universe (Figure 7.31). In this way, they hope to gain a better understanding of the origin of everything
Geneva
CERN research offices Figure 7.31 At CERN in Switzerland, scientists are trying to break down particles of matter inside a 27-km long “supercollider” (shown here in blue), located deep in the ground. These experiments may reveal how the smallest particles of matter were created when the universe first formed.
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small colliding ring access tunnels
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The Wave Nature of Light Light is a form of energy that travels in waves. This kind of energy is also called electromagnetic radiation. Visible light is electromagnetic radiation that we can see with our eyes. There are other forms of electromagnetic radiation as well, including radio waves, microwaves, ultraviolet radiation, and X-rays. When visible light rays are split into a rainbow of colours, the result is called the visible spectrum. Figure 7.32 shows the full electromagnetic spectrum, from radio waves with very long wavelengths, through visible light, to gamma rays with very short wavelengths.
Spectral Colour and Spectral Lines Each of the different colours of the visible light spectrum, from red through to yellow and green and on to violet, varies in wavelength. The wavelength of red light, for instance, is longer than the wavelength for blue light. This distinctive characteristic gives astronomers an important way to analyze star light. A spectroscope helps in this analysis. A spectroscope is an optical instrument that, like a prism, separates light into its spectral colours.
Figure 7.32 The electromagnetic spectrum. Objects in space emit a great variety of electromagnetic energy. Although humans can see only the energy in the visible light part of the spectrum, technology enables us to detect other forms of electromagnetic radiation.
Wavelength (µm) 108
107
Wavelength (µm) 106 radio
105
104
103
microwave
102 infrared
10
1 visible
10–1
10–2 ultraviolet
10–3
10–4
10–5 X-ray
10–6
10–7
gamma rays
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In addition to colour, another characteristic of star or galaxy light that astronomers analyze is spectral pattern. Across a star’s band of colour appears a series of dark lines. These are called spectral lines, and they look a little like the bar code you see on retail products. Spectral lines are created as each gas that makes up a star absorbs some of the light energy. Each element does this in a different way, creating its own particular pattern of spectral lines (Figure 7.33). Because astronomers can see the spectral lines of hydrogen in the spectra of nearly all celestial objects, it is clear that hydrogen is present throughout the universe. Figure 7.33 Analyzing spectral lines in a star’s spectrum indicates what elements are present in the star.
(a) hydrogen
H
(b) helium
He
(c) sodium
Na
(d) calcium
Ca
(e) iron
Fe
Sun
Red-Shifted Spectral Lines While Edwin Hubble was observing the 46 galaxies in his study, he and other astronomers began making careful measurements of the spectra he was collecting. Their knowledge of spectral patterns allowed them to determine that galaxies were moving apart. This conclusion was based on an important property of light called spectral shifting. Spectral shifting is the change in position of spectral lines to the left or the right of where they normally are in the spectrum of a light source that is not moving. The astronomers noticed that in all of the galaxies Hubble was studying, the spectral lines were shifted toward the red end of the colour band. The only way for spectral lines to shift this way is if the light source and the observer are moving away from each other at very high speed. Analyzing the Movement of Light Waves To understand how this happens, remember that light waves move like waves on the surface of water. Picture a duck floating on a small, calm lake. Gentle movements of the duck create
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ripples on the water surface that spread out evenly all around the duck (Figure 7.34a). The wavelength of these ripples is measured as the distance from the crest of one wave to the crest of the next. As the duck begins to swim, the ripples compress and the wavelength shortens in front of the duck. At the same time, the ripples behind the duck stretch out and the wavelength gets longer (Figure 7.34b). So, even if you could not see the duck directly and could only see the ripples on the water, you would still be able to tell whether the duck was moving toward you or away from you. In a similar way, someone observing the light emitted by a galaxy can measure the light’s wavelengths to determine whether the galaxy is moving and, if it is, in which direction. Light Wavelength and Colour When Hubble did his work and saw that the spectra of his sample galaxies were “red-shifted,” he knew this meant that the wavelengths were stretched out. Remember, as Figure 7.32 shows, that red light has a longer wavelength than blue and violet at the other end of the specturm. Hubble therefore concluded that the galaxies were moving away from the Milky Way (Figure 7.35). Had Hubble instead found that the spectral lines were shifted to the blue end of the galaxies’ light spectra, he would have had to conclude that the wavelengths were shorter and more compressed. Just as with the duck example, shorter wavelengths between the observer and the moving object would have meant that the galaxies were moving toward us, not away.
(a) a)
(b) b)
Figure 7.34 Light energy travels in waves, just as sound and other forms of energy do. By observing the pattern made by the waves, we can tell whether an object is moving and, if it is, whether it is moving toward or away from us. This phenomenon is called the Doppler effect. (a) When an object is hardly moving (stationary), its waves radiate out evenly in all directions. The distance between each wave, or wavelength, is the same. (b) When the object is moving, the waves in front of it become compressed (the wavelength shortens) and the waves behind it stretch out (the wavelength lengthens).
spectral lines
star is stationary
star is approaching
star is moving away
no shift
blue shift
red shift
Figure 7.35 If the spectral lines in the light from a star or galaxy occur toward the blue end of the light spectrum, it means the observer is seeing short wavelengths. This “blue shift” indicates that the star or galaxy is approaching the observer. On the other hand, if the spectral lines occur toward the red end of the light spectrum, it means the observer is seeing long wavelengths. This “red shift” indicates that the star or galaxy is moving away from the observer.
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When Hubble and other astronomers found this red-shift pattern in an increasing number of galaxies, it lent support to the idea that space was expanding. Since then, much more evidence has been collected. The Keck telescope in Hawaii is one of the largest optical telescopes in the world (Figure 7.36). Astronomers recently used the Keck telescope to conduct a red-shift survey of galaxies, repeating Hubble’s work. However, this newer survey, called DEEP2, measured the light from 60 000 galaxies instead of 46. The results of the DEEP2 survey supported and added to Hubble’s original work.
Figure 7.36 The Keck telescope in Hawaii
Learning Checkpoint 1. What is a spectrum? 2. What is the name given to the generally accepted scientific theory that describes the origin and evolution of the universe? 3. How is it possible to know that the element hydrogen exists throughout the universe? 4. How does the idea that space itself is expanding relate to the observation that the spectra from distant galaxies are red-shifted?
Using Microwaves to Map Cosmic Background Radiation Until 1965, a critical question related to the Big Bang theory remained unanswered. The theory stated that the very early universe was extremely hot, filled with short-wave gamma ray radiation. Then, as the universe rapidly expanded, it cooled and the wavelength of the radiation lengthened. The radiation became lower energy types, including Xrays, ultraviolet, visible light, infrared, and microwaves. So, asked scientists, if the theory describing this series of events was reasonable, then where was the energy that should have been left over from the very early moments of the formation of the universe? Their prediction was that all of space should contain evidence of this radiation. 284
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In 1965, as the scientists who predicted the presence of this energy set about to look for it, two other researchers, Arno Penzias and Robert Wilson, made the big discovery — a discovery they were not even looking for (Figure 7.37). Their new microwave antenna, intended for use in telecommunications, detected that the entire sky was bathed with microwave energy. It came from every direction, not just from individual stars. This energy is often called cosmic background radiation. It is believed to be the energy left over from the massive and split-second expansion of the universe from a single point some 13.7 billion years ago.
Radiation Maps: Evidence for the Big Bang Theory In 1992, the Cosmic Background Explorer satellite (COBE) made detailed maps of the background radiation collected from the most distant parts of the visible universe. This was followed in 2006 when the Wilkinson Microwave Anisotropy Probe (WMAP) took even more precise measurements of the radiation and created a much enhanced map (Figure 7.38). Both the COBE and the WMAP results showed that the spectrum of the background radiation precisely fits the predictions consistent with the Big Bang theory. In science, although evidence can support a theory, a theory is never considered to be proven correct. On the other hand, if new evidence conflicts with a theory, the theory can be proven incorrect. In this way, the COBE and WMAP surveys not only back up the Big Bang theory, but they also show that other theories of the formation of the universe cannot be supported. One of these not supported is the Steady State theory, which suggests that the universe is infinitely old and that matter and energy constantly enter and leave the universe at equal rates. To date, the Big Bang theory continues to be the only theory for the universe’s formation that is supported by the entire body of scientific information gathered so far.
Figure 7.37 It was while using the Horn Antenna, located in New Jersey in the United States, that radio astronomers Penzias and Wilson unexpectedly discovered the microwave background radiation present in every part of the sky.
Figure 7.38 The universe’s cosmic background radiation, mapped by the Wilkinson Microwave Anisotropy Probe (WMAP). The tiny variations in the radiation are thought to indicate hot regions that are now mostly empty space, and cooler regions where matter could collect to form the first galaxies. Scientific evidence suggests that the universe began expanding from a single point about 13.7 billion years ago.
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Take It Further While the Big Bang theory is now the one generally accepted to explain how the universe formed, others have been proposed in the past as well. These include the Steady State theory, the Big Crunch theory, and the Multiverse theory. The first two of these have been shown to be inconsistent with modern observational data. The third one may still be a possibility. Pick one of these theories and find out about its strengths and weaknesses. Begin your research at ScienceSource.
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An Ever Faster Expanding Universe Many scientists have likened the expansion of space to the expanding surface of a balloon when it is inflated. Just as the dots drawn on the balloon would separate from each other as the balloon expands, so clusters of galaxies move away from each other as space opens up between them. This does not mean that you are slowly getting larger or that Earth is moving farther from the Sun. The effects of the expansion of space are so small that even our Milky Way galaxy is not moving away noticeably from our nearest galaxies, such as Andromeda. Gravity and other forces are strong enough to keep these objects together. However, between clusters of galaxies there is an immense amount of empty space, and the tiny effects of the expansion of space add up. In the last 20 years, data from the most distant galaxies show that the rate at which the most distant galaxies are receding from our view is increasing. In other words, not only are galaxies moving away from us, but they are doing so at an ever-faster rate.
STSE Science, Technology, Society, and the Environment
The Power of Observation Our understanding of space and the universe is directly connected to the technology we use to make observations. Consider the Milky Way. Our ancestors, looking at the night sky with only their unaided eyes, saw the galaxy as a long smudge of light. They could not know that the light came from billions of stars. Over centuries, telescopes improved our ability to see, eventually enabling us to observe details of individual stars lying far outside our solar system. By the 1990s, very powerful telescopes allowed us to peer even greater distances into space, all the way into the centre of the Milky Way.
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To put that in perspective, an astronomer being able to see a star moving at the galactic core is like a person in Ottawa being able to see the wagging tail of a small dog in Vancouver. 1. Read the following statements with a partner or in a small group. Discuss what each statement means, and give at least three astronomy examples to support your ideas. (a) As our ability to see gets better, so does our understanding. (b) As technology improves, so does our ability to find answers to our questions.
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C10 Quick Lab Modelling the Expansion of the Universe (Teacher Demonstration) Edwin Hubble was the first to propose that all of the universe’s galaxies are moving away from each other. Not only that, but he proposed that the galaxies already the most distant from our perspective are moving away faster than the nearer ones. Space, he concluded, is expanding. This activity will help you visualize these ideas. It is presented here as a teacher demonstration but may be done as a group project by students who have access to a photocopier that can make enlargements.
4. The teacher will repeat step 3, once so that the two dots marked B overlap exactly, and then again so that the two dots marked C overlap.
Purpose To model the way that the universe is expanding
Materials & Equipment • paper and black marker • access to photocopier with zoom function
Figure 7.39 Step 1
• two sheets of acetate • acetate marker • overhead projector
Questions 5. (a) What does each dot represent?
• ruler
(b) What does each sheet of acetate represent?
Procedure 1. Before class, your teacher will mark about 30 dots on a sheet of paper. Three dots that are fairly far apart will be labelled A, B, and C. 2. Using a photocopier with a zoom function, the teacher will copy the marked-up paper, enlarging it by about 5 percent. The teacher will then copy each of the two pages onto sheets of acetate to use on an overhead projector. 3. In class, the teacher will lay one sheet of acetate over the other so that the two dots marked A overlap exactly. Note the appearance of all the dots on the overlapped sheets.
6. How do the dots appear to have moved from the viewpoint of dot A? 7. How do the dots appear to have moved from the viewpoints of B and C? 8. Using the ruler, measure the actual change in the distance between dots A, B, and C from one sheet of acetate to the other. 9. Does the changing position of the dots represent galaxies moving through space, or does it represent galaxies being carried with space as it expands? Explain your answer. 10. Describe some of the weaknesses in this method of modelling the universe.
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CHECK and REFLECT
Key Concept Review 1. List the two main discoveries by American astronomer Edwin Hubble that changed astronomy. 2. According to the Big Bang theory, how did the universe originate? 3. What does the visible light spectrum refer to? 4. Define the term spectral shifting. 5. Explain how the discovery and mapping of cosmic background radiation gave scientists evidence in support of the Big Bang theory.
Connect Your Understanding 6. Imagine there is an invisible duck swimming on a calm pond. For each example (a) and (b) shown below, state whether the duck is swimming toward you or away from you. Explain how you know the direction of movement. (a)
(b)
8. If the universe is expanding, is Earth getting bigger? Explain why or why not. 9. How does discovery of cosmic background radiation give support to the Big Bang theory? 10. Sometimes the expansion of the universe is described as being like the surface of a balloon that is slowly inflating. Dots on the balloon are like galaxies. Explain how this model predicts that our own galaxy is not the centre of the universe. 11. Science is based on the idea that a theory cannot be proven correct. It can only be proven incorrect. Imagine that the Cosmic Background Explorer (COBE) survey of background radiation in space had found that the spectrum of background radiation did not match the predictions of the Big Bang theory. In your opinion, what would such evidence have indicated about the theory?
Reflection 12. For each of the following topics, describe three facts that you learned in this section that you did not know before. (a) formation of the universe (b) structure of the universe (c) evolution of the universe
Question 6
For more questions, go to ScienceSource. 7. Explain how the examples in question 6 above are similar to the way in which astronomers can tell the direction galaxies are moving relative to Earth.
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S C I E N Ceverywhere E Hunting
Black Holes
This view of the Milky Way (left), taken using visible light wavelengths, shows how difficult it was for astronomers to see into the galaxy’s centre through the surrounding cloud of gas, dust, and other debris. Only by using telescopes capable of seeing in the infrared did astronomers finally gain a clearer view through the gas and dust lanes and into the galactic core. What they have discovered is evidence of a supermassive black hole.
Night-vision goggles enable a person to “see in the dark.” They do this by detecting light in the infrared part of the electromagnetic spectrum and converting it to visible light. Telescopes can be designed to do the same thing. This is good news for astronomers because such telescopes are especially useful in helping scientists detect the presence of black holes in the universe. This image of the Milky Way (left) shows the same portion of the galaxy as the image above does, but this picture was taken using infrared telescopes. All the dust seems to be absent because it is invisible in the infrared.
The image on the right was taken with today’s advanced telescopes. Views such as this have enabled astronomers to observe that some stars near the centre of the Milky Way are in tight and rapid orbit around something that is not visible. That “something,” astronomers speculate, is a supermassive black hole. One of the orbiting stars is estimated to be moving at a speed of more than 15 million km/h.
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CHAPTER REVIEW
ACHIEVEMENT CHART CATEGORIES k Knowledge and understanding t Thinking and investigation c Communication
a Application
Key Concept Review 1. What is astronomy?
7. (a) What did Edwin Hubble discover about the motion of the 46 galaxies he first studied? k (b) How did Hubble’s discovery provide evidence for what Georges Lemaître had proposed about the universe? k
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2. (a) What type of celestial object orbits our planet? k (b) What type of celestial object does our planet orbit? k 3. What two units do astronomers use to measure the distances between celestial objects? k 4. (a) Explain the difference between a star and a galaxy. k (b) What is the name of the galaxy we live in? k 5. Galaxies are typically classified into four basic types. Name the four types. k 6. Identify the type of galaxy shown in each image below. k
8. How old is the universe thought to be?
9. Does red light in the visible light spectrum have a longer or a shorter wavelength than blue light? 10. (a) Make a sketch to illustrate what astronomers mean when they say that light from a distant galaxy is “redshifted.” c (b) What does a large red shift indicate about a galaxy’s motion? k 11. Explain how cosmic background radiation supports the Big Bang theory of how the universe formed. k 12. (a) Astronomers have learned in recent decades that the most distant galaxies from the Milky Way are moving away from us. At what rate are they moving away? k (b) What does the answer to (a) suggest about how the universe is evolving?
(a) Question 6
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Connect Your Understanding
Reflection
13. Astronomers are able to observe distant regions of space and identify many kinds of celestial objects. Why, then, is it unlikely that we will ever be able to travel even across our own galaxy? t
18. Think about the activities in this chapter that you carried out. Make a list of the ones you did or observed your teacher demonstrating. Beside each activity, write down two points you learned from it that have helped you better understand the concepts presented in the text. c
14. Some galaxies are thought to produce many more new stars than others. What characteristics do galaxies with a high rate of production of stars have in common? t 15. Earth is located towards the edge of the Milky Way, in one of its spiral arms. How would the appearance of the night sky be different if Earth were much closer to the centre of the galaxy? t 16. Astronomy is in an interesting position right now. Most evidence collected by scientists supports the Big Bang theory of the origin and formation of the universe. All other scientific theories to explain the origin have so far largely been disproven by scientific evidence. Do you agree or disagree with the statement: “The Big Bang theory is correct because it is ‘the last theory standing’ ”? Explain the reason for your answer. t 17. Astronomers speculate that thousands of billions of years from now, galaxies will have moved away from ours faster than their light can reach us. Our region of space, like all other regions, will be left in the dark. Is this something we should plan for on Earth? Explain. t
After Reading Reflect and Evaluate How did making connections to your prior knowledge about space and the universe help you to understand new ideas and information? On your mind map, highlight at least five connections between your “old” knowledge and the “new” knowledge that you learned in this unit. Share these connections with a partner.
Unit Task Link Your imaginary trip to the stars in this chapter is meant to give you the “big picture” of Earth’s place in the universe. Given the enormous distances between even our closest planetary neighbours in the solar system, a journey by humans to these destinations would be very long. A one-way trip by spacecraft to Mars would, scientists estimate, take nearly a year. What value would there be in sending humans to Mars? Make a list of the values you think of.
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The solar system formed 5 billion years ago, in the same way other star-and-planet systems in the universe formed.
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Home Silhouetted against a red background of dust and gases is the distinctive Horsehead Nebula, surrounded by brilliant stars. Nebulae are often referred to as stellar nurseries because it is out of the dust and gases that new stars form.
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Skills You Will Use In this chapter, you will: • use star charts to determine the location, appearance, and motion of well-known stars visible in the night sky • plan and conduct a simulation to show the interrelationship between a star’s brightness and its distance from Earth • compare and contrast star size and spectral patterns • gather and record data to calculate the diameter of the Sun • compare the relative sizes of the major components of the solar system, using an appropriate format
Concepts You Will Learn In this chapter, you will: • describe the formation and life cycle of stars, including the Sun • describe and give evidence for the generally accepted theory of the formation of the solar system • describe the characteristics of the major components of the solar system, including the Sun, the planets, and the Moon • explain the causes of astronomical phenomena such as the aurora borealis, solar eclipses, and phases of the Moon
Why It Is Important Studying the formation and life cycles of stars helps us understand what we and everything around us are made of. Studying the motions of Earth and how the Moon and the Sun influence Earth helps us understand why, for example, solar and lunar eclipses occur, comets sometimes streak through the sky, and tides rise and fall.
Before Reading Determining Importance When information seems far beyond your experiences, you must determine its importance to you. Skim the bulleted items on this page and the next. Then, write two statements about how the solar system and the formation of stars are important to you.
Key Terms • aurora borealis • constellation • lunar eclipse • planet • protostar • revolution • rotation • solar eclipse • solar wind
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Stars
Here is a summary of what you will learn in this section: • A star is a huge ball of hot gas, or plasma. Nuclear reactions in its core turn matter into energy. • A star forms inside a nebula as gravity pulls dust and gas together, creating a spinning, contracting disk of material in which nuclear fusion begins. • Stars have life cycles during which they form and then evolve in one of three main ways. • Eventually, most stars cool down and slowly grow cold and dark. Some, however, expand into giants before then cooling down slowly or exploding as a supernova.
Figure 8.1 The Big Dipper seen at dusk over Lake Ontario
Stars: The View from Earth
W O R D S M AT T E R
“Constellation” is derived from the Latin words con, meaning with or together, and stella, meaning stars. “Asterism” is from the Greek word aster, meaning star.
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If you have ever spent time looking up at the sky on a clear night, you have probably noticed that some stars look as though they are grouped together into a distinct pattern. Perhaps the best-known star pattern in the northern hemisphere is the Big Dipper (Figure 8.1). Different cultures around the world refer to this collection of seven stars by other names, such as the Plough, the Ladle, and the Great Cart. The Big Dipper is part of a larger star pattern known as Ursa Major, which is Latin for Great Bear (Figure 8.2). Ursa Major is an example of a constellation. A constellation is a group of stars that, from Earth, resembles a recognizable form. Astronomers have officially listed a total of 88 constellations. Examples, along with Ursa Major, include Cassiopeia, Orion, Pegasus, Sagittarius, and Ursa Minor. Smaller recognizable star patterns within a larger constellation are known as asterisms. The Big Dipper is an asterism. Star patterns like these are just one kind of astronomical phenomenon, a term that refers to any observable occurrence relating to astronomy.
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It is easy to think that all the stars forming a constellation or asterism lie at the same distance from Earth, as though drawn on the ceiling in your classroom. In fact, the stars in the pattern vary greatly in their distances from Earth, with some being many times farther away than the others. They only appear to be twinkling from a flat surface because they are of similar brightness.
Suggested Activity • C12 Inquiry Activity on page 302
Figure 8.2 The constellation Ursa Major. To many cultures, this star pattern looked like a large bear.
C11 Quick Lab Reading Star Charts Star charts are maps that show some or all of the 88 constellations and key stars that are visible from Earth. Stargazers use star charts to orient themselves to the night sky, just like people use maps to find their way around new places on the ground. If someone told you about an interesting star cluster in the constellation of Aquarius, for example, knowing where to look on a star chart would allow you to see the star cluster too.
Purpose To use a star chart to determine the location and appearance of well-known stars, constellations, and asterisms visible in the the northern hemisphere
Procedure 1. Working on your own, turn to the star chart in Skills Reference 12 or use the handout that your teacher gives you.
Questions 2. Looking at the star chart, answer the following questions. (a) In which constellation is Polaris (the North Star) located? (b) What planet is shown in the constellation Capricornus? (c) Betelgeuse is a large star located in what constellation? (d) What is the name of the constellation that has three bright stars in a row? (e) What is the name of the star that seems to form the tail of the swan-shaped constellation known as Cygnus? (f) Is the star Aldebaran located east or west of Betelgeuse? (g) What is the name of the star cluster located midway between the constellations of Taurus and Perseus? (h) What large star seems to form the right foot of the constellation commonly referred to as Orion the Hunter?
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How a Star Is Born Compared with the life span of humans, the life span of stars is extremely long. All stars form inside a collapsing nebula, a cloud of dust and gases. A nebula’s collapse can be triggered by a disturbance such as the gravitational attraction of a nearby star or the shockwave from an exploding star. Inside a collapsing nebula, the region with the greatest amount of matter will start to draw material towards it through gravity. This is where the star will form (Figure 8.4a). Material falling inward to the core has excess energy. This energy causes the central ball of material to begin to spin (Figure 8.4b). Extremely high pressures build up inside the ball, which in turn causes the tightly packed atoms to heat up. As the temperature climbs, the core begins to glow. This is a protostar (Figure 8.4c). A protostar is a star in its first stage of formation. Eventually, the temperature of the spinning protostar rises to millions of degrees Celsius. This is hot enough for nuclear reactions to start. Over tens of thousands of years, the energy from the core gradually reaches the star’s outside. When that occurs, the fully formed star “switches on” and begins to shine.
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The Life Cycle of Stars A century ago, astronomers could tell that different kinds of stars existed. What they had not yet discovered was that stars have a predictable life cycle just like all living things do. It took the work of two researchers in the early 1900s to find the key to understanding star evolution.
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Figure 8.4 (a) As a region of a nebula collapses in on itself, gravity starts pulling dust and gas together into small masses. (b) As a mass grows, it begins a cycle of heating up, spinning, contracting (pulling inward), more heating, and so on. (c) The result of this process is a protostar.
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Figure 8.3 Stars are “born” in nebulae, such as the Eagle Nebula shown here, with its aptly named star-forming “Pillars of Creation” region (inset).
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Star Mass and Evolution
During Reading
How a star evolves in its lifetime depends on the mass it had when it originally formed. Astronomers describe stars in three general mass categories: low, medium, and high. A low mass star, for example, advances through different phases than a high mass star does. Low Mass Stars Low mass stars use their nuclear fuel much more slowly than more massive stars do. Low mass stars burn so slowly that they can last for 100 billion years — more than eight times the current life span of the universe. With less gravity and lower pressures than other stars, the nuclear reactions in the core of low mass stars happen at a relatively slow rate. The stars therefore exist a long time, shining weakly as small red stars called red dwarfs (Figure 8.5). Like the light from a flashlight whose batteries are almost dead, the light of a red dwarf starts dim and gradually grows dimmer. As red dwarf stars run out of fuel, they collapse under their own gravity. This causes the star to reheat, but not enough that nuclear fusion can begin again. Most of the stars in the universe are red dwarfs. Red dwarf stars eventually cool into smaller white dwarfs.
As you read about the evolution of stars, create a chart to compare the different types. Note the types of stars, their names, examples, and two important facts about each type. Which type of star has the longest life? Which type always comes to a violent end?
red dwarf
white dwarf black dwarf
Comparing Important Ideas
nebula
white dwarf protostars
black hole
red giant
main sequence star = 1 solar mass neutron star supernova
supergiant massive main sequence star = 100 solar masses
Figure 8.5 The three main life cycles of stars. What cycle a star goes through is determined by what mass the star first develops after its formation in a nebula. The solar system formed 5 billion years ago, in the same way other star-and-planet systems in the universe formed.
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Medium Mass Stars Medium mass stars burn their fuel faster than low mass stars do, using their hydrogen up in about 10 billion years. The Sun is a medium mass dwarf star. At the end of this long, stable period, the hydrogen fuel in a medium mass star begins to run out and the star slowly collapses under its own gravity. This process of collapsing raises the temperature and pressure again inside the star. This is enough to start the fusion of helium, which has been accumulating in the core. The star reignites. As the core heats up this time, the star expands rapidly into a red giant (Figure 8.5). Aldebaran, for example, is a red giant. Eventually, even the helium fuel burns out and the star collapses again and slowly burns out.
Figure 8.6 Polaris, the North Star, is a supergiant. It is more massive than the Sun and 1000 times brighter. Unlike the Sun, however, Polaris is very unstable.
High Mass Stars High mass stars are those that are more than 10 times the mass of the Sun. In a high mass star, as gravity pulls matter into the centre of the star and squeezes the core, the nuclear reactions accelerate. As a result, a high mass star is hotter, brighter, and bluer than other stars (Figure 8.5). High mass stars always come to a violent end. After using up its hydrogen fuel, typically in less than about 7 billion years, such a star collapses just like a low or medium mass star does. The heating and compression cause helium to begin to fuse. During this process, tremendously high temperatures result, causing the star to expand into a supergiant. Examples of supergiants are Polaris (Figure 8.6) and Betelgeuse (Figure 8.7). When the helium fuel runs out, the core again collapses into itself. The star continues to go through many cycles of collapse and expansion, as new elements, including iron, are formed in its core.
Figure 8.7 Betelgeuse is a red supergiant. It is so huge that if it were in the solar system where the Sun is, it would reach nearly all the way to Jupiter’s orbit.
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Supernovas: The Violent End of High Mass Stars When iron fuses, it does not do so in a way that releases energy. If too much of the core of a high mass star is made up of iron, the star — which may have been shining continuously for more than 7 billion years — will “turn off” in minutes. With no fuel left to keep it producing heat energy, the star collapses one final time. So fast and intense is the collapse that the core of the star heats up to many hundreds of millions of degrees and explodes. As noted in section 7.1, an exploding star is called a supernova. The explosion releases enough energy to cause the iron and other elements to fuse in various combinations (Figure 8.8). In this way, all the elements of the periodic table have been formed. The blast sends these heavy elements far out into space. Some of the debris and elements from the old star create new nebulae out of which new star-and-planet systems may begin to form. The star’s remaining core after a supernova explosion faces one of two outcomes, depending on the mass of the original star:
Figure 8.8 Are you wearing jewellery that contains silver or gold, or do you have a copper penny in your pocket? The atoms in all heavy elements were produced in a supernova.
• Neutron stars — If the star was between 10 and 40 times the mass of the Sun, it will become a neutron star. A supernova explosion is directed not only outward, but also inward. This force causes the atoms in the star’s core to compress and collapse. When an atom collapses, it forms neutrons, particles that are at the centre of most atoms already. When the star’s core becomes little more than a ball of neutrons only about 15 km across, it is called a neutron star. Neutron stars are made of the densest material known (Figure 8.9). • Black holes — If the star was more than 40 times the mass of the Sun, it will become a black hole. After exploding as a supernova, the star’s core is under so much gravitational force that nothing can stop its collapse, not even the formation of neutrons. In this case, the effect of gravity is so great that space, time, light, and other matter all start to fall into a single point. As noted in section 7.1, black holes grow with the more mass they pull in.
Figure 8.9 A neutron star. Imagine the dome at the Rogers Centre in Toronto being filled to the brim with steel and then that amount of steel being compressed to fit inside a 20-L fish tank. That is how dense the matter is in a typical neutron star.
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The Hertzsprung-Russell Diagram
Suggested Activity • C13 Design a Lab on page 303 C14 Quick Lab on page 304
As the life cycle of stars shows, stars occur in many varieties. The differences between them include what colour they are, how bright (or luminous) they are, and even what their surface temperature is (Figure 8.10). In 1919, two astronomers decided to sort and plot thousands of stars according to these three characteristics. Ejnar Hertzsprung and Henry Norris Russell wanted to find out whether any patterns might emerge that would tell us more about the nature of stars. The results of this survey and plotting work became one of the most important discoveries in astronomy in the 20th century. The plotted data revealed for the first time that very clear relationships existed between star properties. Figure 8.11 shows a version of what is called the Hertzsprung-Russell diagram. In it, the stars are arranged as follows: • by colour – Red stars are plotted on the right, and blue stars are plotted on the left. Other stars, such as the yellow Sun, are plotted in between. • by luminosity – The brightest stars are plotted at the top, and the dimmest stars are plotted at the bottom. A star with a luminosity of 100 is 100 times brighter than the Sun. • by surface temperature – The hottest stars are plotted on the left, and the coolest stars are plotted on the right.
Figure 8.10 The stars shown in this binary system differ in colour, luminosity (brightness) and surface temperature.
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Deneb
Betelgeuse
supergiants
Rigel
Polaris
10 000
Antares
Arcturus
red giants Procyon A
Vega
Luminosity (Sun = 1)
100
Spica
m
a
1
Aldebaran
i n
Sirius A
s e Sun q u 0.01
e
Sirius B
white dwarf 0.000 1
n
Procyon B
c
e Proxima Centauri
0.000 001 15 000
12 000
9 000
6 000
3 000
Surface Temperature of the Star (°C) Figure 8.11 The Hertzsprung-Russell diagram represents the plots of thousands of stars based on colour, luminosity (brightness), and surface temperature.
The Hertzsprung-Russell diagram shows many patterns based on the three star properties noted above. For example, the star data forms a distinct band that stretches from the top left of the diagram to the bottom right. This is called the main sequence. The Sun is a main sequence star. These stars are thought to be in the stable main part of their life cycle. They have evolved to this stage since formation but will gradually either cool and die out or expand before exploding. Groups of stars that do not appear along the main sequence are often near the end of their lives. At the bottom centre of the diagram are white dwarfs, such as the star Procyon B. They are white because they are hot, but dim because they are small. White dwarfs are cooling and will eventually become black. At the top right of the diagram are red giants such as Aldebaran and supergiants such as Betelgeuse and Antares. The outer layers of these stars are cool and appear red, but they are bright because they are so large. All of these giants will eventually explode.
Take It Further Many different approaches have been taken to graphically displaying the data of the Hertzsprung-Russell diagram. Find at least three other versions to the one shown here and analyze how effective you think they are. Begin your research at ScienceSource.
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C12 Inquiry Activity
Skills Reference 2
Using a Star Chart Your teacher will give you a simple star chart that can be used for early evening observations.
Question How is it possible to locate the positions of stars in the night sky?
Observing and recording observations Communicating ideas, procedures, and results in a variety of forms
3. After you find the Big Dipper, locate the two stars that make up the outside of the ladle. These are know as the “pointer stars” because they point to Polaris, the North Star. Follow the pointer stars until you see a reasonably bright star. This is Polaris. It is always in this position in the sky no matter what the season or the time. 4. Follow along an arc until you reach a group of five stars that forms a big W. (Depending on the time of night and the season, this may look more like an M.) This is the constellation Cassiopeia.
Materials & Equipment • star chart • flashlight with a red light (optional)
Procedure 1. While facing south, hold the chart over your head, with the chart facing you. Read the chart while looking up. Notice that east will be on your left and west will be on your right. This should match the labelling on the chart. A flashlight casting a red light will allow you to read your chart without having to let your eyes readjust to see the stars. 2. Locate the Big Dipper. Identify it first on your star chart. It is part of the constellation Ursa Major and has the shape shown below. Then, find the Big Dipper in the sky. You will see many more stars in the sky than appear on the chart, but the bright stars making up the Big Dipper should stand out.
5. Finally, go back to Polaris. It is part of the Little Dipper, forming the last star in the handle. The stars of the Little Dipper are not quite as bright as the stars of the Big Dipper, but they are still easily visible with the naked eye.
Analyzing and Interpreting 6. Describe how you used the Big Dipper to find Polaris, Cassiopeia, and the Little Dipper. 7. If you were unable to find any of these stars or groupings, explain what problems occurred that prevented you from locating them in the sky. 8. The star Sirius is brighter than Polaris. Would it make more sense to call Sirius the North Star, instead of Polaris? Explain your answer.
Skill Practice 9. Using your star chart, identify three other constellations in the northern sky.
Forming Conclusions Cassiopeia Little Dipper (Ursa Minor) Polaris (North Star)
Big Dipper (Ursa Major)
10. (a) If you were able to use the star chart effectively in this activity, write one guideline to add to the procedures that would help another student using a star chart for the first time. (b) If you were not able to use the star chart effectively, list one or more questions that you would need answered to help you find some or all of the identified objects. Figure 8.12 Three commonly observed constellations and Polaris
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C13 Design a Lab
Skills Reference 2
Planning for safe practices in investigations Drawing conclusions
Star Light, How Bright? Just as stars vary in mass, colour, and temperature, so they vary in brightness. The brightness of stars viewed from Earth depends on both their actual brightness (luminosity) and their distance from Earth. If, for example, all stars had the same brightness, then we could assume that the ones that look dimmer to us from Earth are farther away than those that look brighter. In a similar way, identical flashlights held at different distances from us will appear to vary in brightness, too. There are many aspects to the relationship between a light source’s actual brightness and its distance from a viewer that can be explored. For example, is it necessary to double the distance of a light source from a viewer before the brightness of the light source is cut in half? In this activity, you will have an opportunity to investigate the brightnessdistance relationship by using flashlights or LED penlights (but not laser sources of any kind) to assess changes in brightness related to distance.
Question How does the distance of a light source from an observation point affect the apparent brightness of the light source?
2. Determine how you will safely measure light intensity from your various sources. For example: Will the light be projected onto a screen and the light intensity of the reflection observed, or will one partner shine light into another partner’s eyes from different distances? How will the intensities of light be compared if they happen at different times or if different people make the observations? Can cameras be used? How will you make your measurements? 3 . Design a procedure to carry out the investigation. Include in it a list of materials and equipment you will need. As well, design a data table to collect information on your brightness observations. 4. Ask your teacher to check the design of your procedure and data table. 5. Perform your investigation. 6. Prepare a formal lab report to document how you conducted the investigation. At the end of the report, summarize the results of your investigation in one or more paragraphs. 7. Consider how you could refine your investigation if you were to repeat it. Discuss your suggestions with your teacher.
CAUTION: Laser pointers of any kind, including LED laser pointers, are potentially damaging to the eyes and are not appropriate for this experiment.
Design and Conduct Your Investigation 1. Select a variety of light sources to use in your investigation. Possible light sources include nonlaser light sources of different brightness such as penlight LEDs and flashlights with LED or incandescent bulbs.
Figure 8.13 Possible set-up for activity
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C14 Quick Lab Analyzing Stars by Their Spectral Patterns Spectral patterns in stars are a little like star “fingerprints.” By spreading a star’s light into its spectral colours and “reading” the black spectral lines that appear, we can identify the individual chemical elements making up the star. Knowing what elements are in a particular star gives us information about how the star formed, whether it is likely to be surrounded by rocky planets like Earth, and how it will probably come to an end someday. In this activity, you will analyze and compare spectral patterns to determine the chemical make-up of several stars.
Purpose To identify the make-up of two mystery stars by analyzing their spectral patterns
hydrogen
1. Looking at Figure 8.14, study the spectral patterns for the five elements shown. 2. Answer the questions below, recording your answers in your notebook.
Questions 3. Which three elements are visible iin mystery star A? 4. Which three elements are visible in mystery star B? 5. Which element listed in the spectral chart is not present in either mystery star? 6. Make a sketch of the spectrum that would be expected in a nebula that contains mainly hydrogen and lithium.
H
helium
He
lithium
Li
beryllium
Be
magnesium
Mg
mystery star A mystery star B Figure 8.14 Spectral patterns for analysis
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CHECK and REFLECT
Key Concept Review 1. (a) What is a constellation? (b) How many official constellations are there? 2. What is a star called during its earliest stage of formation? 3. What process must occur inside a forming star before it can “switch on,” creating its own light? 4. What main property of newly formed stars determines how the star will evolve?
10. Using the Big Dipper as a point of reference, explain how you would help someone identify Polaris, the North Star, in the night sky. 11. Organize the following list in correct order of evolution. (a) protostar (b) nebula (c) star (d) red giant 12. Explain how the colour of a star is related to its:
5. Most stars in the universe are what type?
(a) luminosity
6. Name the three characteristics by which stars are plotted on the Hertzsprung-Russell diagram.
(b) temperature
7. Explain the important concept about stars that was revealed by the HertzsprungRussell diagram. 8. Use the Hertzsprung-Russell diagram in Figure 8.11 on page 301 to answer the following questions.
13. Sirius is orbited by a white dwarf known as Sirius B. In the image below, Sirius B is the tiny white dot to the lower left of Sirius. Sirius B has a mass slightly less than the Sun’s mass. What inference can you make about the kind of star Sirius B will eventually become?
(a) Which star’s surface temperature is cooler, Antares or Vega? (b) How many times more luminous is Polaris than Procyon A? (c) The Sun is of too low a mass to explode in a supernova. As the Sun evolves and slowly dies out, on which part of the diagram would it be classified?
Connect Your Understanding 9. Describe how our view of constellations and asterisms in the sky and on star charts is misleading.
Question 13
Reflection 14. As you read in this section, newly formed stars evolve in one of three main ways. Think of a simple but creative method you could use to summarize and remember the stages in each of these life cycles. For more questions, go to ScienceSource.
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The Solar System
Here is a summary of what you will learn in this section: • The solar system refers to the eight planets, their moons, and all the other celestial objects that orbit the Sun. • The solar system formed from the leftover gas, dust, and other debris spinning around the newly formed star, our Sun. • The Sun ejects a steady stream of charged particles called the solar wind. Earth’s magnetic field deflects the wind, protecting life on the planet. • The four rocky planets in the inner solar system are Mercury, Venus, Earth, and Mars. The four gaseous planets in the outer solar system are Jupiter, Saturn, Uranus, and Neptune.
Figure 8.15 A solar flare erupting from the surface of the Sun
Our Solar Centre
Figure 8.16 A solar tornado, with a temperature of several million degrees Celsius
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The star at the heart of our solar system, the Sun, is the star we know better than any other in the universe. The Solar and Heliospheric Observatory (SOHO), a solar space telescope, has had a clear view of the Sun since 1995. The information it sends back to Earth, such as the image of the solar flare in Figure 8.15, shows us its fiery nature. The Sun even experiences tornadoes. Tornadoes are powerful and destructive wind events that occur in many parts of North America, including southern Ontario. Recently, scientists have learned that tornadoes also occur on the Sun. A tornado on Earth is a vertical funnel of air that is a few hundred metres in diameter and rotates at speeds up to 500 km/h. A tornado on the Sun is much more extreme. A solar tornado is a tall funnel of twisting plasma. The tornado shown in Figure 8.16 is more than 20 000 km in diameter, which would be large enough to contain Earth. It rotates at 500 000 km/h and has a temperature of several million degrees Celsius. While the Sun is a turbulent neighbour at times, Earth is the only planet in the solar system whose orbit is just the right distance away that a habitable environment for life is created.
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DI Key Activity
C15 Quick Lab Sizing Up the Solar System Showing the distance between planets and the size of the planets on the same scale in one diagram in a textbook is impossible. If all the planets were sized large enough to be visible on the page, showing the distances to the same scale would make the diagram wider than your classroom.
Purpose To explore the solar system by changing the scale of various objects inside and beyond it
Materials & Equipment • 4 diagrams, each showing the following objects as a 5-cm disk: Earth, the Sun, the solar system, and the distance from the Sun to the next nearest star • 1 diagram showing the Moon as a 1.5-cm disk • grain of sugar • metre stick or measuring tape
Procedure 1. Working in small groups, carry out each of the three tasks below. In each one, you are asked to predict the distance between two celestial objects at a particular scale. Use the hints provided, as well as what you may already know about the solar system. If necessary, make a “best guess.” 2. At the end of each task, share your results with the class. Your teacher will then give out the correct answer so that you can carry out the next task with an understanding of the scales so far. 3. Task 1: Imagine shrinking Earth to be 5.0 cm in diameter. At this scale, the Moon is 1.5 cm in diameter and the Sun is 5 m (the length of a small truck). The distance from Earth to the Sun at this scale is 500 m (about five soccer fields long). Your task: Using this model scale, predict how far apart Earth and the Moon would be and then set them that distance apart.
4. Task 2: Imagine shrinking the solar system until the Sun is 5 cm in diameter. At this scale, Earth is the size of a grain of sugar. The Moon is a speck of dust about 5 mm from Earth. The farthest planet, Neptune, is about 200 m (about two soccer fields long) from the Sun. The next nearest star is 1500 km away. Your task: Using this model scale, predict how far apart the Sun and Earth would be and then set them that distance apart. 5. Task 3: Imagine shrinking the solar system again until Neptune’s orbit around the Sun is 5 cm in diameter. At this scale, the Sun is smaller than the size of a “•” at the centre of the orbital disk and Earth lies about 1 mm from the Sun. Light from the Sun takes 8 min to reach Earth, 4 years to reach the next star, and 100 000 years to reach across the galaxy. Your tasks: Using this model scale, predict the following and then set the objects apart. (a) the distance between the solar system and the next nearest star (b) the size of the Milky Way galaxy
Questions 6. In this activity, you made a number of distance predictions based on different scales. (a) Which of your predictions were the most accurate? (b) Which of your predictions were the least accurate? (c) What can make predicting accurately a difficult thing to do? 7. The disk showing the solar system shows the eight planets roughly equally spaced in their distances from the Sun. In fact, the planets are not equally spaced. Suggest a reason why it was useful to show them spaced evenly.
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During Reading All Ideas Are Not Equal As you read, think about which information is most important to know and which is nice to know. In your notebook, draw a web showing the most important ideas in large circles and the “nice to know” ideas in smaller circles connected to the larger ones.
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The Nature of the Sun Our Sun is a good example of a typical star. Of medium size by star standards, it is composed mainly of hydrogen (73 percent by mass) and helium (25 percent by mass). The rest is made up of heavier elements including carbon, oxygen, and iron. It formed in the same way that all stars do, taking shape inside a nebula, the “stellar nurseries” of the universe. The Sun is believed to have first begun shining about 5 billion years ago and is expected to continue shining for about 5 billion years more before it runs out of fuel. The Sun emits radiation of almost all forms found in the electromagnetic spectrum. The most obvious are visible light and ultraviolet (UV) radiation. Some forms of UV cause sunburn when a person’s skin is exposed directly or indirectly to the Sun for too long. Astronomers have estimated the Sun’s mass by observing how fast the solar system’s planets and other celestial objects orbit around it. Understanding how the Sun uses its hydrogen comes from discoveries made in the last century about atomic energy. The nuclear reactions taking place in the Sun are thought to be the same ones that occur in the most powerful kind of atomic weapon, the hydrogen bomb. In both cases, the reaction involves a small amount of hydrogen being converted into helium, which causes a rapid release of tremendous amounts of energy.
The Sun’s Layers solar flames
The Sun has six main layers, as shown in Figure 8.17.
photosphere convective zone corona radiative zone
sunspots core
chromosphere
Figure 8.17 The layers and surface features of the Sun
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Core The inner part of the Sun is called its core. Here, pressures are high and temperatures are at least 15 million degrees Celcius. Nuclear fusion happens in the Sun’s core. As discussed in chapter 7, nuclear fusion is a process in which light atoms fuse (meaning combine) and become heavier ones. During fusion, a small amount of matter is turned into a huge amount of pure energy.
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The fusion reaction creates helium, which concentrates in the Sun’s core. The tremendous energy produced during fusion causes the surface of the Sun to swell outward, despite the tremendous pull from the Sun’s gravity that causes the Sun’s mass to collapse inward.
Suggested Activity • C16 Inquiry Activity on page 319
Radiative Zone and Convective Zone Surrounding the core are two layers. The layer outside the core is called the radiative zone. The plasma is very dense here. Light and other forms of radiation are continuously absorbed and re-emitted in all directions. This layer extends three-quarters of the way up to the surface of the Sun. Light takes at least 100 000 years to pass up and through it. This means that the solar radiation we receive today was generated in nuclear reactions in the Sun’s core more than 100 000 years ago. The layer outside the radiative zone is the convective zone. In this region, huge bubbles of hot plasma ooze up toward the surface, carrying energy. Slightly cooler regions of plasma sink from higher levels in the zone to lower levels, where they warm up again. This constant circulation of plasma between hotter and cooler regions is called convection, which gives this layer its name. Photosphere, Chromosphere, and Corona The Sun does not have distinct edges between its layers, but the photosphere is usually considered to be the boundary between the inside and the outside of the Sun. This is the part of the Sun we see from Earth. It has the lowest temperature of all the layers, about 5500°C. The Sun’s yellow colour originates in the photosphere. Above the photosphere is a thin layer called the chromosphere. “Chromos” means coloured, and this layer has a red cast to it. Because the yellow photosphere is so bright, however, we can see the chromosphere only during a total solar eclipse (Figure 8.18) as discussed in section 8.3. The corona is the outermost layer of the Sun and extends beyond the chromosphere for millions of kilometres. During a solar eclipse, when the corona is most clearly visible, Figure 8.18 The Sun’s thin red chromosphere. This zone has the astronomers are best able to make careful same composition as the photosphere but is several thousand degrees Celsius hotter. measurements of it.
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Surface Features of the Sun
Earth shown for size comparison
Figure 8.19 The magnetic field of the Sun is made visible by its effects on the plasma in the Sun’s atmosphere. The field lines exit the Sun at one end of the arc and re-enter the Sun at the other.
Both the Sun and Earth have magnetic fields. Earth’s magnetic field produces the North and South Magnetic Poles. If you have ever used a hand-held compass, you have seen the magnetic field at work spinning the needle. The magnetic field is caused by spinning molten (meaning melted) metal deep in Earth’s core. The Sun also has a magnetic field, generated by movement of the plasma deep in the Sun’s interior. The Sun’s magnetic field extends far out into space where it is carried by the solar wind (as shown in Figure 8.22 on page 313). It is extremely powerful and can be seen in the way the Sun’s plasma reacts (Figure 8.19). The four main features on the surface of the sun are sunspots, prominences, flares, and coronal mass ejections.
Sunspots A sunspot is a region on the Sun’s surface that is cooler than the surrounding areas. Although still very bright, by contrast it looks darker than the surrounding areas (Figure 8.20). Sunspots indicate regions where the magnetic field is extremely strong, slowing down convection. This prevents the plasma from mixing, therefore allowing the region to cool from about 6000°C to 4000°C. Sunspots come and go. The number of them reaches a maximum every 11 years, increasing when the magnetic field strength of the Sun also reaches a maximum level.
Figure 8.20 The dark zones surrounded by a lighter border are sunspots. Each is larger than Earth’s diameter.
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Prominences A prominence is a large, often curved, bright stream of particles extending outward from the photosphere into the corona. Frequently the curved shape forms a complete loop (Figure 8.21). The electrically charged plasma in the prominence allows the prominence to be shaped by the magnetic field. This makes part of the magnetic field visible. A prominence may last for many hours. Solar Flares A solar flare is a massive explosion at the surface of the Sun. It usually originates where the magnetic field breaks out of the Sun’s surface and interacts with the chromosphere and corona. This sudden release of magnetic energy flings hot plasma out into space, which we see as a Figure 8.21 A large prominence with Earth shown for size long bright filament extending out from comparison the Sun. Figure 8.15 at the start of this section shows a solar flare. An extremely powerful kind of flare is called a coronal mass ejection. When this occurs, a large amount of plasma is thrown out through the corona and into space at a speed of more than 1000 km/s. Sometimes, a coronal mass ejection may be pointed directly at Earth. When this plasma stream reaches Earth about three days later, it meets Earth’s magnetic field. Our magnetic field protects Earth by diverting much of the plasma away from the planet’s surface. This causes particularly vivid and active auroras, as described on the next page. It can also damage orbiting satellites and electrical transmission lines on the ground.
Learning Checkpoint 1. Which two elements make up more than 99 percent of the Sun? 2. Where in the Sun does nuclear fusion occur? 3. What is the difference between the radiative zone and the convection zone in terms of how energy is transferred up toward the outside of the Sun? 4. Name four types of surface features on the Sun. 5. How can a coronal mass ejection on the Sun cause damage on Earth?
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The Sun’s Effects on Earth As you have read, the Sun warms Earth and supports every form of life on the planet. In addition to these significant influences, there are many other ways the Sun affects our planet. The solar wind and aurora borealis are two of these ways.
The Solar Wind The tremendous amount of heat at the surface of the Sun produces a thin but steady stream of subatomic particles. This constant flow of particles, streaming out of the Sun’s surface in all directions, is called the solar wind (Figure 8.22). Early in the solar system’s history, the solar wind blew against the nebula from which it formed. This pushed the gas and dust away from the Sun. The material that was not blown away continued to swirl around the Sun. The swirling motion caused the dust, rocks, and gas that had not fallen into the protostar to form into a thin disk. It is from within this disk that all the other bodies in the solar system took shape. During turbulent solar times, electronic equipment and devices on Earth may be damaged by higher-than-normal blasts of charged particles from the Sun.
magnetosphere solar wind
Earth
Figure 8.22 The solar wind crosses space and strikes Earth. Earth’s protective magnetic field, the magnetosphere, deflects most of this solar wind.
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The Aurora Borealis The solar wind is responsible for creating the breathtaking displays of green, yellow, and red light in the skies near Earth’s northern and southern regions. In the northern hemisphere, these light displays are called the aurora borealis (the Northern Lights). In the southern hemisphere, they are called the aurora australis (the Southern Lights).
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The aurora borealis is produced when the charged particles of the solar wind collide with the atoms and molecules in Earth’s atmosphere. An aurora (meaning a glow) forms as particles from the solar wind are trapped by Earth’s magnetic field and are swept toward the North and South Poles (Figure 8.23).
How the Solar System Formed After the Sun formed, the leftover dust, gases, and other debris in the nebula continued to Figure 8.23 The aurora borealis spin, creating a disk around the new star. Small bodies began to form, growing into the planets, moons, asteroids, and comets that make up the solar system (Figure 8.24). This process, astronomers believe, is how other star-and-planet systems in the universe have formed as well. After the Sun, the next largest bodies in the solar system are the eight planets. A planet is a celestial object that orbits one or more stars and is capable of forming into a spherical shape as it melds under the weight of its own gravity. A planet does not create and radiate its own light like a star does. It only reflects the light of the star or stars that it orbits.
Swirling gas and dust
Remaining gas and dust form planets
Most gas and dust accumulate in the middle, forming a star.
Figure 8.24 The solar system formed when the gas and dust left over from the formation of the Sun continued to spin around the star. Gravity caused the material to clump together and contract, creating a range of celestial objects, from planets and moons to asteroids and comets. The solar system formed 5 billion years ago, in the same way other star-and-planet systems in the universe formed.
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The Rocky Inner Planets As the spinning particles of dust and gas slammed into each other during the early stages of the solar system’s formation, some of the particles began sticking together. Larger particles tended to grow faster than smaller ones because they were involved in more collisions. This is similar to a large snowball growing faster when you roll it in sticky snow than a small snowball does. As these objects got bigger in mass, gravity caused them to contract and bind together even more strongly. Objects orbiting too close to the Sun gradually fell into it, drawn by its gravitational force. They burned up. However, four large objects lasted and eventually formed into the four rocky planets, Mercury, Venus, Earth, and Mars (Figure 8.25; see the planet summaries on page 316). Earth’s Moon Within a few hundred million years after forming, the young Earth may have been struck by an object nearly the size of the planet Mars. In this enormous collision, both of the objects remelted and mixed. The metal core at the centre of the Mars-sized object shot through its melted crust and plunged deep into Earth where it merged with Earth’s metallic core. The rocky crusts of Earth and the Mars-sized object mixed, but the momentum of the collision destroyed much of the rest of the material. The larger object cooled down to become Earth as we know it today. The smaller object, likely formed from material torn from Earth after this collision, became trapped by Earth’s gravity. It existed first as debris and rubble, but eventually it compacted into a new object, the Moon. Mars is the only other of the rocky planets with a moon, and it has two, Phobos and Deimos.
Mars
Sun
Earth
0
Saturn
Jupiter
Venus Mercury 5
10
15 Distance from Sun (astronomical units)
Uranus
20
Neptune
25
30
Figure 8.25 The solar system. The four rocky planets closest to the Sun were the first to form. The four gaseous planets in the outer solar system took shape later.
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The Asteroid Belt Past the orbit of Mars lies a huge band of rocks that is spread out in a vast ring circling the Sun (Figure 8.26). Some of the rocks are as large as asteroid belt 1000 km across, about the distance between Ottawa and Thunder Bay. Others are as small as grains of sand. This is the asteroid belt. Mars Sun Some scientists looking for Earth-like planets in other star systems are doing so by Earth looking for the presence of an asteroid belt around the star. If there is such a band, this might indicate that rocky planets are orbiting the star as well. Jupiter It is the analysis of asteroids that has given us the estimated age of the solar system. Occasionally, asteroids fall from their orbit Figure 8.26 The asteroid belt lies between the orbits of Mars and Jupiter. and crash to Earth. By the 1950s, scientists had found a way to determine the age of many asteroid specimens. The oldest ones were dated at 4.56 billion years old. Because Earth would have formed at the same time as the asteroids did, researchers have used this asteroid-dating technique to date Earth. As it took time for the asteroids to form, the Sun and solar system are currently estimated to be about 5 billion years old.
The Four Gaseous Outer Planets The solar wind blows gases away from the Sun, but this does not mean that all the gases escape the solar system completely. Just beyond the asteroid belt is the “snow line.” On the Sun side of this line, the Sun’s radiation keeps water in its gaseous phase. However, out past the snow line, water can cool to form droplets and then freeze. Astronomers believe that the four largest planets in the solar system may have grown as they did because ice acted as a kind of glue to cause gas and dust particles in the outer regions of the solar system to stick together. In fact, these planets grew much faster even than the rocky ones did. The result was the four gas giants: Jupiter, Saturn, Uranus, and Neptune (see the planet summaries on page 317). All of the gas giants are orbited by numerous moons. Jupiter and Saturn each have more than 60 moons (Figure 8.27).
Figure 8.27 Io, a moon of Jupiter, is shown here orbiting the large planet.
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Mass (Earth mass)
Average Surface Temperature (°C)
Period of Rotation (Earth day)
Period of Revolution (Earth year)
The Rocky Planets Average Distance from Sun (AU)
Planet
Radius (km)
Mercury
0.4
2400
0.1
180
60.00
0.2
Venus
0.7
6100
0.8
470
240.00
0.6
Earth
1.0
6400
1.0
17
1.00
1.0
Mars
1.5
3400
0.1
–60
1.03
1.7
Mercury
Most of what we know about Mercury has been determined from telescope and satellite data. Mercury is the planet closest to the Sun. Its surface is similar to that of the Moon. Mercury has no atmosphere and therefore no protection from being bombarded by asteroids and comets. The scars of millions of years of impacts show this. Other parts of Mercury’s surface are smooth, which is probably from lava flowing through cracks in the rocky crust. The temperatures on Mercury vary greatly, from over 400°C on the sunny side to –180°C on the dark side.
Venus
Venus is similar to Earth in diameter, mass, and gravity, and is often called Earth’s twin. However, Venus would be unfit for humans to visit. Surface temperatures are kept hot by a greenhouse effect caused by thick clouds. Temperatures can be over 450°C, hot enough to melt lead. The atmospheric pressure is about 90 times that on Earth. Venus’s surface cannot be seen by telescope because of its thick cloud cover. The permanent clouds, made of carbon dioxide, often rain sulphuric acid (the same acid found in a car battery). Russia landed a probe on Venus in 1982, but it stayed operational for only 57 min. In 1991, the spacecraft Magellan mapped Venus using radio waves (radar). The Venus Express orbiter arrived in 2006 and continues to make atmospheric studies. It has found huge canyons, extinct volcanoes, and ancient lava flows. Venus is one of only two planets in the solar system to rotate from east to west, the opposite direction to the other six.
Earth
Earth is unique in the solar system for several reasons. It is the only planet where water exists in all three states: solid, liquid, and gas. It is also the only planet that is at the appropriate distance from the Sun to support life as we know it. Earth is protected from solar and cosmic radiation by its atmosphere and its magnetic field. The ozone in the atmosphere screens life on Earth from ultraviolet (UV) radiation. The magnetic field makes most of the charged particles from the solar wind and cosmic rays stream around the planet, far outside the atmosphere. Water covers 70 percent of the planet’s surface. Earth is one of the few planets in the solar system that has active volcanism.
Mars
Mars has been studied by telescope for centuries. It is often referred to as the “red planet,” though it is actually more orange in colour. This appearance is caused by the iron oxides on the planet’s surface. Mars has two polar ice caps: one is made up of frozen carbon dioxide and water, and the other is made up of carbon dioxide only. The atmosphere is very thin and composed mainly of carbon dioxide. Although the average surface temperature is extremely cold, temperatures at Mars’s equator can reach 16°C in the summer. Like Venus and Earth, Mars has canyons, valleys, and extinct volcanoes. Mars has two small moons.
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The Gaseous Planets Planet
Average Distance from Sun (AU)
Radius (km)
Mass (Earth mass)
Average Surface Temperature (°C)
Period of Rotation (Earth day)
Period of Revolution (Earth year)
Jupiter
5.3
71 000
320
–150
0.41
12
Saturn
9.5
60 000
95
–170
0.45
30
Uranus
19.0
26 000
15
–215
0.72
84
Neptune
30.0
25 000
17
–215
0.67
165
Jupiter
Jupiter has been observed through telescopes since the 1600s. The Voyager probes visited Jupiter and many of its moons in 1979, followed by the Galileo probe in the mid1990s. Jupiter is the largest of all the planets in the solar system. It contains more than twice the mass of all the other planets combined. Jupiter is composed mainly of hydrogen and helium, and scientists speculate that if the planet were only 10 times larger than it is, it might have formed into a star. The Great Red Spot visible on Jupiter is a huge storm in its atmosphere. Jupiter has three very thin rings.
Saturn
Saturn is the second-largest planet in our solar system and has the most distinctive ring system of all the eight planets. Over a thousand rings exist, composed of pieces of ice and dust that range in size from grains of sand to house-sized blocks. The Italian astronomer Galileo saw Saturn’s rings with his primitive telescope in 1610, though he initially thought they were a group of planets. Voyager 1 and Voyager 2 flew by Saturn in 1980 and 1981, respectively. In late 2004, the Cassini spacecraft arrived at Saturn and dropped a probe onto Titan, the largest of the planet’s moons. Saturn, like Jupiter, is composed mostly of hydrogen and helium. Because of the planet’s quick rate of rotation, wind speeds at Saturn’s equator have been estimated at over 1800 km/h.
Uranus
Voyager 2 has given us most of our close-up information about Uranus, last sending data back to Earth in 1986 before it left the solar system. Satellite and telescope analyses have provided other interesting details. Uranus has one of the most unusual rotations in the solar system. Its axis of rotation is tilted toward the plane of its orbit, making it appear to roll during its orbit. Uranus is composed mainly of hydrogen and helium. Methane in its atmosphere gives the planet a distinctive blue colour. Uranus has a large ring system and 17 moons.
Neptune
When scientists observed the orbit of Uranus to be different from what they had calculated, they searched for an eighth planet. In 1846, they found Neptune. About a century and a half later, Voyager 2 flew to Neptune to collect more information. The composition and size of Neptune make it very similar in appearance to Uranus. Composed of hydrogen, helium, and methane, Neptune is bluish in colour as Uranus is. Very little of the Sun’s energy reaches Neptune, which gives off about three times more energy than it receives. This planet has the fastest wind speeds in the solar system, 2500 km/h. Like all the other gas giants, Neptune has its own ring system, as well as eight moons.
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The Minor Planets Beyond the gas giant planets, a number of very large balls of ice formed. These have come to be called minor, or dwarf, planets, the most famous of which is Pluto. Pluto is large enough to hold three icy moons. Nix and Hydra are tiny. Charon is about half the size of Pluto. There are millions of small objects besides Pluto and Charon orbiting the Sun. Some are larger than Pluto, but most are smaller. Together, they create a thin disk that, like the asteroid belt, forms a ring around the entire solar system. About 25 of these are large enough, however, to be considered minor planets.
Comets and Meteors Take It Further In 2000, the first space probe ever to orbit an asteroid reached Eros in the asteroid belt. Eros measures 33 km by 13 km. Find out the purpose of the mission to Eros and whether it succeeded in its task. Begin your research at ScienceSource.
The most distant region of the solar system is the Oort Cloud. It consists of billions of fragments of ice and dust, and is thus a major source of comets. A comet is a celestial object made of ice and dust. When a gravitational disturbance causes one to change its orbit and fall nearer the Sun, the Sun heats the comet, causing some of its ice particles to break away. Carried away from the Sun by the solar wind, these icy particles spread out into a tail millions of kilometres long, lit up by the Sun (Figure 8.28). Comets can sometimes be seen from Earth, passing slowly across the sky over several days. Also visible from Earth are meteors, which streak brightly through the sky in seconds. You may have heard these referred to by the colourful but incorrect nickname of “shooting star.” Meteoroids are small pieces of rock or metal that travel throughout the solar system with no fixed path. They are thought to be similar in origin to asteroids and comets. A meteor is a meteoroid that, upon entering Earth’s atmosphere, begins to burn up as a result of friction. If a meteor does not burn up completely and strikes Earth’s surface, it is called a meteorite.
Figure 8.28 Most comets have been orbiting the Sun in the Oort Cloud for billions of years. Because of their composition, they are often referred to as “dirty snowballs.”
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C16 Inquiry Activity
Skills References 2, 8
Conducting inquiries safely Identifying sources of error
Measuring the Sun’s Diameter The distance from Earth to the Sun has been measured to be about 150 million km. With this information, we can make a measurement of the Sun’s diameter without looking directly at the Sun. How we do this is by using an apparatus that takes advantage of the property of similar triangles. If each of the three angles in triangle A is the same as the corresponding angle in triangle B, then we know that the size of triangle A will be exactly proportional to the size of triangle B. For example, if you know the length of the sides of triangle A, even if it is only in centimetres, you can calculate the length of the sides of triangle B, even if it is many times larger than A.
Question How can the diameter of the Sun be measured safely and accurately?
Materials & Equipment
Procedure 1. Move outside. Hold the apparatus with the screen against your stomach to keep it steady. Move the metre stick until the image of the Sun’s disk appears on the white paper. 2. Mark the diameter of the Sun’s image on the paper. Repeat several times and average the result. 3. Calculate the Sun’s diameter in kilometres, using the average image diameter in centimetres (see Figure 8.30). Because the Sun’s diameter and Sun’s distance from the pinhole create a similar triangle to the triangle created by the Sun’s image and the image’s distance to the pinhole, the following formula can be used to calculate the diameter: D d = 100 cm 150 000 000 km where d = diameter (cm) and D = Sun’s diameter (km)
• Imaging apparatus (see Figure 8.29) • metre stick
Analyzing and Interpreting
• calculator
4. Your teacher will give you the accepted value. Compare yours with it. How did you do?
CAUTION: Never look directly at the Sun.
5. Suggest two ways to improve making the measurement.
Skill Practice
tape
metre stick
6. A student makes a measurement using an imaging apparatus that is 50 cm long. The image diameter is measured to be 1 cm. What value would be calculated for the diameter of the Sun?
to Sun
white paper to sketch on
hole in cardboard covered with foil
Forming Conclusions
Figure 8.29 Assembly of apparatus Sun’s image
pinhole
7. Compare your results with those of other members of the class to ensure that you have done the calculation properly.
Sun
d
D
100 cm
150 000 000 km
8. State your results for the diameter of the Sun. 9. At the end of your work, return the apparatus to your teacher.
Figure 8.30 Capturing the Sun’s image
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C17 Problem-Solving Activity
Skills References 3, 6
Defining and clarifying the inquiry problem Thinking critically and logically
A Model of the Solar System Recognize a Need You have been asked to generate a graphic representing the solar system with correct scales for planet diameters and distance of planets from the Sun. The graphic should be meaningful to younger students interested in astronomy.
Make a Drawing
Problem How can the scales for planet diameter and distance from the Sun be displayed on the same graphic?
Materials & Equipment • ruler
• note paper
• geometry compass • scissors
• 1 piece of flipchart paper
• coloured markers
• glue or tape
Criteria for Success • The planets are drawn to a correct scale by diameter and are labelled and coloured appropriately. • The planets are positioned to a correct scale to represent their distance from the Sun.
Brainstorm Ideas 1. Working with a partner, use the data from the planetary charts on pages 316–317 to determine what scale would give your solar system graphic the best and most accurate fit on a piece of flipchart paper. 2. The Sun will be too large to fit on your graphic. Just show a curved edge of the Sun on one side of the paper, or think of some other way to represent the Sun. 3. It will not be possible to use the same scale to represent the planet diameter and the planet distance from the Sun. Therefore, determine a different scale to show your solar system distances.
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4. Make a table showing each planet’s real diameter (km) and distance from the Sun (AU). Then, add two columns to the table and write in the model diameter (cm) and distance from the Sun (cm) that you will use in your solar system graphic.
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5. Draw each planet separately on a piece of paper according to your scale (in cm). Cut the sphere out. (Depending on your scale, your cut-out may have to be larger than the actual planet drawing.) Colour each planet based on information you read in section 8.2. 6. On the flipchart paper, draw the curve of the Sun as recommended in step 2. Then, measure the distance from the Sun each planet should be positioned in your model. Glue or tape each planet in place, ensuring it is labelled.
Test and Evaluate 7. Check that none of the planets overlap each other. If any do, you will need to modify your design so that they do not overlap. You may need to change the scales, but the relative distances from the Sun or diameter must still be correct.
Skill Practice 8. Explain how you converted the diameter or distance of the planet from the Sun in km or AU into units of cm.
Communicate 9. Check with your teacher about placing your graphic on the classroom wall.
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CHECK and REFLECT
Key Concept Review 1. The Sun is composed almost entirely of what element? 2. (a) How long has the Sun existed? (b) How much longer is it expected to shine?
9. In 2008, Canadian astronomers were the first to capture an image of three planets orbiting a star far from the solar system (see below). Make a sketch to illustrate the accepted theory of how a star-and-planet system such as this formed.
3. List the six layers of the Sun from the core out. 4. How many years ago was the radiation you see and feel from the Sun today produced by nuclear reactions inside the Sun? 5. Name the surface feature of the Sun shown in each image (a) and (b) below.
Question 9 The star around which these three planets
have been discovered in orbit lies 160 ly from Earth.
(a)
(b)
Question 5
6. Explain what causes the astronomical phenomenon known as the aurora borealis.
Connect Your Understanding 7. Compare and contrast the four inner planets with the four outer planets in terms of composition, size, shape, and position in the solar system. 8. The Moon does not have a dense metallic core as Earth does and instead appears to be composed only of the same materials as are found in Earth’s outer layers. Based on this information, what conclusion can be drawn about the formation of the Moon?
10. Explain why the presence of an asteroid belt around other stars besides the Sun might be evidence that Earth-like planets might exist. 11. What is the relationship between the position of the “snow line” in the solar system and the size of the planets on either side of it? 12. Why would it be unreasonable to expect Saturn-like rings around any of the inner planets in the solar system?
Reflection 13. In reading about the scale of the solar system and working through the related activities in this section, what did you learn that impressed you most about the relative size of the solar system objects and the distances between them? For more questions, go to ScienceSource.
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Earth, the Sun, and the Moon
Here is a summary of what you will learn in this section: • Earth rotating on its axis produces day and night. Earth revolving around the Sun once a year produces the seasons. • As the Moon revolves around Earth, the amount of the Sun’s light the Moon reflects back to Earth changes. These changes create the phases of the Moon. • In a solar eclipse, the Moon moves between Earth and the Sun, casting a shadow on part of Earth. In a lunar eclipse, Earth moves between the Moon and the Sun, casting a shadow on the Moon. • Tides result from the gravitational effects of the Moon and the Sun on Earth and its oceans. Figure 8.31 Midnight in the Arctic during the peak of summer
Earth in Motion If you lived in a region near Earth’s equator, you would notice little change from day to day throughout the year in the hours of daylight relative to the hours of darkness. Every day all year long, about 12 h of daytime would be followed by about 12 h of night. The farther north or south of the equator a person lives, however, the bigger the range he or she sees in daily hours of light over a year. In the northern hemisphere, we experience the hours of daylight changing in a non-stop cycle, lengthening as we move into summer and shortening as we move into winter. No matter where you live in Ontario, think how different it is at 5 p.m. on a December afternoon compared with 5 p.m. on a July afternoon. The greatest daylight extreme is in Arctic regions, where the Sun does not set some days at the peak of summer and does not rise some days at the peak of winter (Figure 8.31).
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The reason for this tremendous variation is that Earth spins like a top around a tilted axis, the imaginary line running through the planet. As it spins, Earth also revolves around the Sun. These two motions cause day and night, season changes, and what looks from Earth to be movement of the Sun and the stars across the sky.
C18 Quick Lab The Effects of Earth’s Motion on Our View of the Sky Early people were well aware that when they observed the position of the Sun and constellations shifting in the sky, a seasonal change was coming.
Purpose To simulate the relationship between Earth’s motion, the position of celestial objects as viewed from Earth, and the changing seasons
5. Earth slowly turns in a counter-clockwise direction until Earth’s front experiences midnight. Note which star pattern on the wall Earth can now see and how the Big Dipper is oriented. 6. Repeat steps 4 and 5 for the other seasons by having Earth stand south, east, and north of the Sun.
Questions Materials & Equipment • diagrams of Polaris (the North Star), Cassiopeia, Little Dipper, Big Dipper, Orion, Leo, Scorpius, and Pegasus • masking tape or thumb tacks
Procedure 1. Your teacher will tape the diagram of Polaris on the ceiling in the centre of the room and tape the diagrams of Cassiopeia, Little Dipper, and Big Dipper around Polaris in their correct orientation. 2. On each of the four walls in the room, tape the following diagrams: Orion (winter) on the west wall, Leo (spring) on the south wall, Scorpius (summer) on the east wall, and Pegasus (autumn) on the north wall. 3. Have one student be the Sun, standing in the middle of the room. 4. Have another student be Earth. Earth stands to the west of the Sun and facing the Sun. In this position, Earth’s northern hemisphere is in winter and the time of day on Earth’s front is noon. Earth cannot see any stars because the Sun’s light is outshining them.
7. What motion of the person playing Earth (a) represents the passing of 1 day on Earth? (b) represents the passing of 1 year on Earth? 8. With the person representing Earth rotating counter-clockwise, does the Sun rise on the left side or the right side of Earth’s face? 9. Explain why different constellations are visible in the evening in different seasons. 10. Why does the orientation of the Big Dipper change with the seasons?
April July Polaris (North Star)
February November
Figure 8.32 The Big Dipper changes its orientation in the sky throughout the year.
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During Reading Taking Notes A simple strategy for taking notes is to create a two-column chart. List important ideas, concepts, and terms in the lefthand column. Then write the key information or definitions related to those ideas, concepts, and terms in the right-hand column. A two-column chart provides a good study tool.
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Rotation: Creating Day and Night The North and South Poles mark the two ends of Earth’s axis on the planet’s surface. One complete spin of Earth on its axis is called a rotation. A rotation takes almost 24 h, with Earth moving at 1670 km/h towards the east at the equator. Earth’s axis is tilted at an angle of 23.5° relative to the imaginary flat surface, or plane, along which Earth orbits the Sun. This is shown in Figure 8.33. It is this daily rotation of Earth that creates day and night. On the side of Earth facing the Sun, it is daytime. Twelve hours later, that same point on Earth is pointing away from the Sun. This is midnight. Viewed from above the North Pole, Earth spins counterclockwise. This explains why the Sun always appears to rise in the east and set in the west no matter where you are in the world. Although it might feel as though the Sun is the object that is moving while we watch from a seemingly stationary Earth, really it us spinning like a top around Earth’s axis. Standing on Earth, we are carried eastward toward the Sun. We do not feel the motion of rotation because the rotation is relatively slow and the ground and air move with us. Instead, we see the Sun “rise.” As Earth continues to spin, we are carried past the Sun until, later in the rotation, the Sun appears to disappear below the horizon, or set.
4
1
Sun
3
2 Figure 8.33 Earth rotates on its axis and revolves in its orbit around the Sun. When Earth’s northern hemisphere is pointed away from the Sun, the season there is winter.
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Revolution and Tilted Axis: Creating Seasons Seasons occur in all parts of the world but differ from region to region. In the tropics near the equator, there are usually only two seasons: wet and dry. Other equatorial regions experience a monsoon season, hurricane season, hot season, or cool season. However, in northern and southern parts of the world, such as Canada and New Zealand, four seasons are generally recognized: spring, summer, autumn, and winter. When it is summer in Canada, it is winter in New Zealand. Six months later, it is New Zealand’s turn to have the long warm days and short nights of summer while Canada goes into the season of short days and cold weather (Figure 8.34). Changing seasons are the result of Earth’s tilted axis and the planet’s revolution around the Sun (Figure 8.33). A revolution is one complete orbit of Earth around the Sun, a journey of one year. The axis of Earth always stays at approximately the same tilt, regardless of the season. Earth’s North Pole points almost exactly toward the star Polaris. This means that for a period during Earth’s orbit around the Sun, the northern hemisphere is tilted toward the Sun. This creates summer in the northern hemisphere, with days lengthening as the Sun rises early and sets late. As Earth orbits to the far side of the Sun, the planet’s axis is still pointed at Polaris, but the northern hemisphere now tilts away from the Sun. This creates winter in the northern hemisphere, with days shortening as the Sun rises late and sets early. In spring and autumn, neither of Earth’s hemispheres is more directed at the Sun than the other. This means that, for a time, days and nights are 12 h long everywhere on Earth.
(a)
(b) Figure 8.34 Typical January weather in (a) Ontario, in the northern hemisphere; and (b) New Zealand, in the southern hemisphere
The Moon The Moon is about one-sixth the mass of Earth. The two bodies are bound together by gravity. Like Earth, the Moon rotates on an axis. Over time, the Moon’s period of rotation (the time to spin once) and period of revolution (the time to orbit once around Earth) have become equal. Every 27.3 days, the Moon rotates and revolves once. For this reason, the same side of the Moon always faces Earth.
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Phases of the Moon The Moon is bright because it is reflecting the Sun’s light. You know from seeing the Moon on different nights how the shape of its bright part changes daily. These various changes are referred to as the Moon’s “phases.” Although the changing appearance of the bright part of the Moon is a continuous process, eight main phases have been identified (Figure 8.35). It is the Moon’s revolution around Earth that creates the phases. One complete change of phases is called the lunar cycle. Many early cultures tracked time according to the lunar cycle. Some lunar calendars have 13 months in a year rather than 12 months. The full moon occurs when Earth lies between the Sun and the Moon (though not usually exactly between or that would cause an eclipse, described below). In this position, with the Moon on one side of Earth and the Sun on the other, the entire illuminated side of the Moon faces Earth. Two weeks later when the Moon lies between Earth and the Sun, none of the sunlight reflected by the Moon can reach Earth. This is called a new moon, because over the next two weeks the Moon will become newly illuminated again.
first quarter
waxing gibbous
waxing crescent
new
full
sunlight
Figure 8.35 The phases of the
Moon are shown as seen from Earth. The lunar cycle begins with a new moon, grows in size to a full moon two weeks later, and then gradually diminishes until the new moon begins again. 326
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waning gibbous
waning crescent
last quarter
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Learning Checkpoint 1. Earth rotates and revolves. Explain what each of these action means. 2. The axis of Earth is tilted. What is it tilted in relation to? 3. Explain why when it is summer in the northern hemisphere, it is winter in the southern hemisphere. 4. Why do we see only one side of the Moon at all times? 5. Sketch how the Sun, Earth, and the Moon are arranged on a night when we can see a full moon.
Eclipses Although the Sun is about 400 times the size of the Moon in diameter, both objects as seen from Earth appear to have the same size in the sky. The reason for this is that the Sun is also about 400 times farther from us than the Moon is. Because of this similar size appearance, when the Sun, the Moon, and Earth line up exactly, a partial or total shadow of one body is cast on another. Such overshadowing events are called “eclipses.”
WARNING: If you are ever lucky enough to view a solar eclipse in person, be sure to watch it through a suitable filter or by projecting the Sun’s image onto a screen. Never look at the Sun with the unprotected eye or you risk doing permanent damage to your vision.
Solar Eclipse A solar eclipse occurs when the Moon blocks the Sun’s light to viewers on Earth. For a few minutes, some or all of the Sun seems to disappear. This happens when the Moon lies directly between Earth and the Sun. As Figure 8.36 shows, with the Sun shining behind it, the Moon casts a shadow over a small part of Earth. Solar eclipses are of two main types. In a partial solar eclipse, the Sun is only partially blocked from our view by the Moon (Figure 8.37a). In a total solar eclipse, the Moon completely blocks out our view of the Sun (Figure 8.37b).
(a)
(
penumbra Moon Sun umbra
Earth (b)
Figure 8.36 For a total solar eclipse to occur, the Moon must be aligned exactly between the Sun and Earth.
Figure 8.37 (a) Partial solar eclipse (b) Total solar eclipse
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Lunar Eclipse A lunar eclipse occurs when Earth blocks out the Sun’s light shining on the Moon, making the Moon briefly disappear, fully or partially. This happens when Earth lies directly between the Moon and the Sun, as shown in Figure 8.38. Observers on Earth see the Moon pass under Earth’s shadow. The shadow cast across the Moon is circular because Earth is a sphere. (a)
penumbra
Moon
Sun Earth
umbra Figure 8.38 For a total lunar eclipse of the Moon, Earth must be aligned exactly between the Sun and the Moon.
(b) Figure 8.39 (a) Partial lunar eclipse. (b) Total lunar eclipse
As with solar eclipses, lunar eclipses are of two main types. In a partial lunar eclipse, the Moon is only partially blocked from our view by Earth’s shadow (Figure 8.39a). In a total lunar eclipse, Earth’s shadow darkens the entire Moon (Figure 8.39b).
Tides
tidal bulge created by Moon’s pull
to Moon
low tides
gravitational force
Earth’s oceans
high tides
Figure 8.40 The effects of the gravitational field of the Moon on Earth’s oceans causes a bulge on both sides of Earth, resulting in two tides per day.
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Some first-time visitors to an ocean learn about tidal action the hard way. If they leave their shoes or a beach towel on the shore unattended, within an hour or so the level of the water can rise enough to soak the shoes and towel completely. Tides are the alternate rising and falling of the level of the oceans every day. They are caused by the rotation of Earth in the presence of the Moon and, to a lesser extent, the Sun. The gravitational pull of the Moon and Sun on Earth’s oceans and Earth itself causes the water bodies to bulge. As the oceans rise higher in one part, they fall in another. The pattern then reverses. Figures 8.40 shows how the Moon causes a bulge in two places on Earth, both on the near side and on the far side. The bulge on the far side occurs because the Moon’s gravitational pull is not as strong there. Earth is being pulled toward the Moon more than the water on the far side is. This creates the bulge on both sides of Earth at once. The two bulges result in two high tides and two low tides in coastal areas of Earth almost every day.
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The Bay of Fundy on the east coast of Canada is famous for having the largest vertical tidal range (the difference between high tide and low tide levels) in the world. In the open ocean, where the rise and fall of the water level is not affected by land, the daily vertical tidal range averages less than 1 m. By comparison, the Bay of Fundy creates a narrow, funnel-like channel that constricts the incoming water as the tide rises. As a result, the vertical tidal range in the bay can be as much as 17 m a day. Figure 8.41 shows the effects of these changing tide levels along the Fundy coast.
(a)
Take It Further Earth has several other kinds of motion besides rotation and revolution. One is called precession, which is the changing angle of the axis of rotation. Like the axis of a spinning top changing angle as the top moves across a table, so Earth’s axis of rotation slowly changes angle. One complete cycle of precession takes 27 000 years. Find out more about Earth’s precession. Begin your research at ScienceSource.
(b)
Figure 8.41 New Brunswick’s Bay of Fundy is well known for its large range between (a) high tide levels and (b) low tide levels.
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STSE Science, Technology, Society, and the Environment
Space Weather The Sun’s energy heats Earth and supports all life on the planet. At the same time, however, the Sun poses many challenges for Earth’s inhabitants. The electrified gas that the Sun occasionally spews into space from its turbulent and explosive surface creates what astronomers call “space weather.” When solar storms occur, Earth is bombarded by showers of charged particles. Such events can destroy orbiting satellites (disrupting, for example, cellphone, television, and other communications systems) and burn out power grids that supply electricity to homes and
businesses. Even the top of Earth’s ozone layer, the part of the atmosphere that prevents harmful ultraviolet radiation from reaching the planet’s surface, is greatly reduced when Sun activity sends out a blast of streaming particles.
1. ScienceSource Use the links provided at ScienceSource to read more about space weather and how sunspot activity and solar storms can affect humans and equipment. Make a consequence map, or write a news article or weather alert.
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C20 Quick Lab The Phases of the Moon Have you ever noticed a full moon rising at sunset or setting at sunrise? Does it always happen this way for full moons? Why are there some times at night when the Moon is not visible and some times in the day when it is? Why does the Moon sometimes appear only as a crescent? In this activity, you will investigate these questions.
3. Standing in one spot, each student rotates to a noon position. Students may discuss what the correct position for this is. Then, find the correct position for sunrise, sunset, and midnight. Compare with other students until there is agreement as to what this looks like in your model.
Purpose
4. Stand so that it is midnight and hold up the model Moon at arm’s length, high enough so that your head does not cast a shadow on the sphere.
To investigate what causes the phases of the Moon
Materials & Equipment • bright light without a shade • white Styrofoam spheres stuck on the end of a pencil (one per student)
5. Experiment by moving the model Moon to different locations around your head, always at arm’s length. Observe the shadows that appear on the Moon. Discuss with other students what their observations are.
1. Students spread out, with enough room to hold their model Moon slightly overhead at arm’s length and be able to rotate with the sphere held out. Each student is Earth.
6. To model one month of the Moon’s movement, hold out the Moon and turn counter-clockwise. Note the continuous change of the shadow on the Moon as seen from Earth. Discuss your observations with another student until you agree on what you are seeing.
2. The teacher, as the Sun, will make the room dark and stand in a central position holding a very bright, unshaded light overhead (Figure 8.42).
7. One last time, follow the Moon through one month of phase changes, this time noting whether you are most likely to view each phase during the daytime or at night.
Procedure
Questions 8. Does a full moon always rise at sunset and set at sunrise? Explain. 9. Draw three phases of the Moon that are most likely to be seen (a) during the daytime and (b) at night. 10. Does the amount of sunlight striking the Moon change during the month (not counting eclipses)? Explain. 11. Why does the amount of sunlight reflected from the Moon to Earth change during a month? Figure 8.42 Step 2
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12. ScienceSource Research the names for the different phases.
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CHECK and REFLECT 7. Most coastal areas on Earth experience two high tides and two low tides a day.
Key Concept Review 1. How much time does one rotation of Earth take?
(a) Describe the function of the Moon in generating these tides.
2. How much time does one revolution of Earth take?
(b) Predict how the tides would be affected if the Moon orbited Earth closer than it does now.
3. From Earth, why does the Sun appear to be rising in the east and setting in the west?
8. When we view the nighttime sky, the positions of the stars constantly change except for Polaris, the North Star.
4. Referring to the figure below, identify in which position of Earth it would be:
(a) What causes the apparent motion of the stars in the night sky?
(a) summer in the northern hemisphere (b) winter in the southern hemisphere
(b) Why does Polaris appear to stay in a constant position in the sky?
(c) autumn in the northern hemisphere
9. Why is the Moon not shown on star charts?
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5. Define each of the following astronomical phenomena, and sketch the positions of Earth, the Sun, and the Moon to illustrate your definition. (a) solar eclipse (b) lunar eclipse
Connect Your Understanding 6. Do you agree or disagree with the statement “A total eclipse of the Moon by Earth can happen only during a full moon”? Justify your answer using a diagram.
10. Earth can completely eclipse the Moon, but the Moon cannot completely eclipse Earth. What conclusion can you draw from this fact about the relative sizes of two bodies? 11. “Eclipse chasers” are people who make a hobby of travelling around the world for the opportunity to watch solar eclipses firsthand, especially total solar eclipses. Explain: (a) how scientists are able to forecast when solar eclipses will occur and from what positions on Earth they can be seen (b) why no one observing a partial or total solar eclipse should ever do so by looking at the event directly
Reflection 12. Many aspects of the interrelationship between Earth, the Sun, and the Moon were discussed in this section. List two questions you still have about any of these aspects. For more questions, go to ScienceSource.
The solar system formed 5 billion years ago, in the same way other star-and-planet systems in the universe formed.
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Investigating
CAREERS
Great CANADIANS in Science
Figure 8.43 Canadian astronaut Julie Payette working aboard the International Space Station in 1999
Many Canadian travellers take maple syrup and crests of their favourite hockey teams with them to offer as gifts on a trip outside the country. So, when Julie Payette was packing for a trip she was about to make out of the country — in fact, off the planet and all the way to the International Space Station — she decided to take those gifts along, too. In May 1999, Payette was part of the crew on NASA’s space shuttle Discovery, which docked with the International Space Station. The space station was still in its early stages of assembly while it orbited Earth at 400 km. Working as a mission specialist, Payette had a range of duties to fulfill during the more than nine-day space flight. Chief among those Figure 8.44 Julie Payette in training to was helping to operate a robotic servicing system used on the International Space Station repair an
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in Science Julie Payette electrical system on the space station, coordinating and supervising an 8-h space walk, operating the robotic Canadarm, and doing maintenance on the space station’s photography and recording equipment. For the then 36-year-old astronaut, who is from Montreal, Quebec, the opportunity to go into space was something she had set her sights on since childhood. Payette credits a belief in hard work and a “Dare to dream” philosophy as helping her reach that goal. Payette’s list of achievements includes speaking two languages fluently (French and English), four languages conversationally (Russian, Italian, Spanish, and German), earning university degrees in electrical and computer engineering, being selected from among more than 5300 applicants in 1992 to become an astronaut with the Canadian Space Agency, and obtaining a commercial pilot licence and then certification as a jet pilot and as a deep-sea diving suit operator. As part of the Discovery mission, Payette became not only the first Canadian to participate in assembling the International Space Station but also the first Canadian to board the station — and, let it not be forgotten, the first astronaut to arrive at the space station bearing maple syrup and a Montreal Canadiens hockey crest.
Questions 1. What duties did Julie Payette have in her role as mission specialist during her flight to the International Space Station in 1999? 2. ScienceSource Use the Internet to find out about Julie Payette’s second mission to the International Space Station, aboard the space shuttle Endeavour in 2009.
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Robotics Engineer
Figure 8.45 Robotics engineers design and build many robotic systems for the space industry. Examples include Canadarm2 and Dextre, whose official title is the Special Purpose Dexterous Manipulator.
Dextre may not be able to play the piano or type text messages, but the “robotic handyman” at the International Space Station comes by its name honestly. Dextre (pronounced Dexter) is short for dexterous, which means having the ability to manipulate something manually. What Dextre does well is use its two long robotic arms and twofingered hands to make delicate repairs and installations on the outside of the space station. For this capability, Dextre — designed and built in Brampton, Ontario — has become famous. Canada is a leader in robotics technologies. The space industry employs many people who work in this field. Robotics are automated mechanical systems capable of performing many tasks that a person could. In space, which is an extremely high-hazard environment for people to work in, robotics are vital. This is where robotics engineers come in. Robotics engineers design, test, and build robotic systems to carry out specialized tasks in specific settings. In addition to having a thorough understanding of how mechanical systems work, a robotics engineer must have the knowledge to create computer programs that install and operate robotics systems. He or she must also excel at
problem-solving. Having a creative and imaginative mind is a beneficial quality, too. To become a robotics engineer, a person first requires a bachelor’s degree or higher in engineering. Robotics technologies used in the space industry draw from many different areas of engineering, including software, systems, mechanical, electrical, and electronics. Some universities and colleges have even developed robotics engineering degrees. Working closely with robotics engineers are robotics technologists and technicians. Many colleges and technical institutes offer one- to three-year programs that teach practical and applied skills in such jobs as robotics planning, testing, manufacturing, inspecting, and repairing.
Questions 1. Name three qualities that someone interested in becoming a robotics engineer would benefit from having. 2. ScienceSource Use the Internet to learn more about the education requirements to become a robotics enginer, technologist, or technician.
Figure 8.46 Demand for robotics engineers will continue to grow as demand for robotics systems onboard space craft grows.
The solar system formed 5 billion years ago, in the same way other star-and-planet systems in the universe formed.
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CHAPTER REVIEW
ACHIEVEMENT CHART CATEGORIES t Thinking and investigation k Knowledge and understanding c Communication
a Application
14. List the three key properties of stars used to construct a Hertzsprung-Russell diagram. k
Key Concept Review 1. Define a protostar.
Connect Your Understanding
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2. What is the relationship between the mass of a star at its birth and the life span of the star? k 3. In terms of mass, what kind of star is the Sun: low, medium, or high? k 4. Name the process occurring in the core of the Sun that gives it its ability to shine. k 5. High mass stars end their existence in an explosion that can produce one of two types of results. What are those two results? k 6. What is convection, and how does this process help the energy produced in the core of the Sun make it to the outside? k
15. Suppose you can see two stars of equal brightness in the night sky. One star appears to be yellow in colour, and the other star appears to be blue. Which star is closer to Earth? Explain your answer, making reference to the Hertzsprung-Russell diagram in Figure 8.11 on page 301. t 16. When an asteroid strikes Earth, it can cause great damage. A pair of asteroids simultaneously crashed into the Canadian Shield on the east side of Hudson Bay about 290 million years ago as shown in the image below. Suggest how it might have happened that the two asteroids crashed at the same time. t
7. Why does a prominence take on the shape of a huge arc on the surface of the Sun? k 8. What is the solar wind?
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9. How do astronomers believe the Moon was formed? k 10. How have astronomers used asteroids to estimate the age of the solar system? k 11. What is a comet?
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12. Explain the difference between the terms revolution and rotation in terms of Earth’s motion. k 13. (a) What causes the changing phases of the Moon? k (b) How many main phases of the Moon are there? k
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17. The four gaseous outer planets are by far the largest planets in the solar system. Why did they grow much larger than the four rocky inner planets? t 18. Explain how, if you see a comet, you would know in which direction the Sun lies. t
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19. Suppose a gaseous planet half the size of Saturn were discovered. Where in the solar system do you think it would be located? Give a reason for your answer. t 20. For decades, Pluto was classified as being the ninth planet in the solar system. It even has three moons, as shown in the image below. Today, Pluto is classified as a minor planet. Recall the characteristics of the eight planets, and list at least two reasons supporting Pluto’s reclassification as a minor planet and two reasons against its reclassification. a
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Reflection 23. The following words are often used in explanations and discussions about star formation and evolution: nursery, birth, life cycle, and death. Do you think that the use of these words provides a reasonable analogy or not? Explain your thoughts on this. c
After Reading Reflect and Evaluate Work with a partner to list all the strategies you know and have learned for determining or finding important ideas. Create a tip sheet for other students in the class on how to find important ideas. Exchange your tips with another pair of students and then post your sheet in the classroom, with the teacher’s permission.
Question 20 Pluto and its moons, Charon, Nix (in the middle), and Hydra (far right).
21. Does summer occur because Earth moves closer to the Sun or because the part of Earth experiencing summer receives more sunlight? Make a sketch to illustrate your answer. c 22. Compare the positions of the Sun, Earth, and the Moon during a solar eclipse to their positions during a lunar eclipse. t
Unit Task Link The solar system consists of four rocky planets, four gas giants, and many other objects, each following a path around the Sun and each travelling at a different speed. Millions of asteroids, comets, and meteoroids also travel through the solar system. Explain how the relative speeds of Mars and Earth, as well as the presence of so many other bodies moving between the two planets, pose a challenge for sending a space probe from Earth to Mars.
The solar system formed 5 billion years ago, in the same way other star-and-planet systems in the universe formed.
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Space exploration improves our knowledge and gives us beneficial technologies, but its hazards and costs are significant.
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Skills You Will Use Astronauts working at the International Space Station must learn to cope with the effects of microgravity in their home in space. In this image, a bag of fresh fruit floats between the astronauts.
In this chapter, you will: • use appropriate terminology related to the study of the universe, including orbital radius and satellite • gather and record data, using an inquiry or research process • compare and contrast properties of celestial objects visible in the night sky, drawing on information gathered through research and using an appropriate format
Concepts You Will Learn In this chapter, you will: • describe how humans throughout history have interpreted their observations of the universe and used that knowledge to aid them in everyday life • assess the contributions of Canada to space research, technology, and exploration • assess some of the benefits, costs, hazards, and issues of space exploration
Why It Is Important Exploring the universe gives us a greater understanding of its nature while also advancing the development of technologies for use on Earth. At the same time, the hazards and cost of space programs are significant and must be considered relative to the benefits.
Before Writing Signalling Organizational Patterns Good writers give signals to the reader about the way text is organized. They use dates and sequencing words (such as first, next, then) to indicate time order for a chronological or sequential account. Often, in scientific writing, writers will also use a problem-solution pattern, describing a problem and suggesting possible solutions. Skim section 9.1, and decide which type of organizational pattern is used.
Key Terms • artificial satellite • equinox • geostationary • microgravity • orbital radius • retrograde motion • solstice (summer and winter) • spinoff
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How Ideas of the Universe Have Changed over Time
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Here is a summary of what you will learn in this section: • Throughout history, humans have explained the universe based on what they are able to observe. • Early cultures and civilizations studied celestial patterns with their unaided eye and used their observations to develop calendars, plan hunting and farming activities, navigate across oceans and land, and inspire spiritual beliefs. • As telescopes and other technologies have advanced, humans have been able to see farther out into space and to capture images in the visible and invisible parts of the electromagnetic spectrum. Such observations change our understanding of the universe.
Figure 9.1 An artist’s concept of Pioneer 11 in flight against the backdrop of Saturn’s rings. Pioneer 11 is expected to be approaching a star in the constellation Aquila in about 4 million years.
Into the Frontier of Space In 1972, the space probe Pioneer 10 was launched by the National Aeronautics and Space Administration (NASA), the agency in the United States responsible for the country’s space program. The mission of this unpiloted spacecraft was to fly past Jupiter and then continue on to the outer solar system. Pioneer 10 transmitted images of Jupiter back to Earth that revealed details humans had never been able to see before. The probe continues to travel away, but no signals have been received from it since January 2003. By August 2009, Earth-based telescopes tracking Pioneer 10 saw that it was already more than 1000 times farther from the Sun than Earth is. If nothing interferes with its progress, it could pass the star Aldebaran in about 2 million years. In 1973, Pioneer 11 was sent off on a similar mission as its sister space probe, but with the added task of capturing images of Jupiter as well as Saturn (Figure 9.1). No communication has been received from the probe since 1995. Two similar space probes, Voyager 1 and Voyager 2, were launched in 1977 to continue the study of Jupiter, Saturn, and the outer solar system. Voyager 1 is the most distant human-made object in space (Figure 9.2). 338
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Both Pioneer craft have now left the solar system and are travelling like two Neptune Pioneer 10 Voyager 2 “ghost ships” into space. Uranus Pioneer 11 The two Voyager craft continue to transmit data to Saturn Earth, but their future will be like that of the Pioneer Voyager 1 probes. Still, the purpose of all four craft has not entirely Figure 9.2 The current location and direction of travel of the Pioneer 10 and 11 space ended. Aboard each Pioneer probes, as well as Voyager 1 and 2 probe is an engraved plaque showing a man and woman, the solar system, and other basic information to indicate where Earth is located (Figure 9.3). Aboard each Voyager probe is a “golden record,” with recorded sounds and pictures of Earth.
Figure 9.3 Peaceful greetings on the plaque aboard Pioneer 10 and Pioneer 11
C21
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Greetings from the People of Earth Each of the Pioneer space probes that have left the solar system carries the plaque shown in Figure 9.3. It is hoped that other planetary life forms that think enough like humans might find one of the probes and be able to use the plaque information, even millions of years from now, to locate Earth.
Purpose To think about the implications of sending information about humans into space
Procedure 1. Working in a small group, read through the questions below. Discuss each question within your group, and record your answers in point form. If there are differences of opinion within your group, be sure to note them down. 2. When you have discussed all the questions, your teacher will invite all groups to share their answers with the class.
Questions 3. What does our sending information like this out into space suggest about our own ideas of the universe? 4. What does the plaque information assume about the nature of any aliens who might acquire it? 5. If you were to design your own plaque, what would you put on it? Why? 6. If the plaque can last a million years, will it outlive the human race? Explain your answer. 7. Would aliens capable of finding the plaque already know about Earth because of our radio transmissions? 8. Is the most likely finder of the plaque going to be future human space travellers who have forgotten their early roots? Explain your answer.
Space exploration improves our knowledge and gives us beneficial technologies, but its hazards and costs are significant.
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Building on Past Knowledge The idea that humans could send spacecraft such as Pioneer 11 and 12 so far away to gather information about the universe would have been unimaginable a century ago. Still, today’s accomplishments in astronomy are built on the observations and scientific problem-solving of the past. People on Earth have watched and wondered at celestial Figure 9.4 The Aztec Sun calendar was events for thousands of years. Our ancestors followed used by people of Mexico hundreds of years ago. This wheel shows both a astronomical phenomena and used the patterns to mark the 365-day calendar cycle and a 260-day passage of time, foretell the changing seasons, and indicate ritual cycle. The two cycles together formed a 52-year “century.” direction during travels (Figure 9.4). Most early civilizations also have stories that are tied to the sky. An Iroquoian (Ongwehonweh) story, for example, tells of Earth having been started on a turtle’s back so that the Sky Woman could come down from Skyland to plant the seeds of trees, grass, and other life forms. A similar story about origins is that of the Haida on Canada’s West Coast (Figure 9.5). Such stories reflect our human need to try to make sense of our existence. As knowledge of the world around us gets passed on from generation to generation, cultural learning advances. In this way, for example, the Aztecs and Mayans developed accurate calendars over generations of observation and recording. European understanding of the universe during the Renaissance in the 15th century relied heavily on astronomical knowledge gathered by Islamic Figure 9.5 This carving by Haida artist Bill Reid depicts Raven coaxing the First People to emerge into the universe. astronomers for more than 800 years.
Solstices Suggested STSE Activity • C22 Quick Lab on page 349 W O R D S M AT T E R
The word “solstice” comes from the Latin sol, meaning sun, and stice, meaning stop.
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Two important annual events for our ancestors were the summer solstice and winter solstice. In the northern hemisphere, the summer solstice, occurring near June 21, marks the longest period of daylight in the year and represents the start of summer. The winter solstice, occurring near December 21, marks the shortest day of the year and represents the start of winter. In the southern hemisphere, the solstices are reversed: the summer solstice is near December 21, and the winter solstice is near June 21.
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Predicting the approaches of summer and winter was important to early peoples, and many ancient civilizations built huge monuments to honour beliefs they had related to seasonal changes. While they may have had only the power of the unaided eye to view astronomical phenomena, their observations of the position and path of the Sun throughout the year were highly accurate. More than 4500 years ago, for example, an early people erected the megaliths of Stonehenge, arranging them to mark the summer and winter solstices (Figure 9.6). Ancient African cultures also set large rock pillars into patterns that could be used to predict the timing of the solstices.
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Figure 9.6 Stonehenge in England is estimated to be about 4500 years old. Much of the structure still stands.
Equinoxes Another regular phenomenon honoured by early cultures was the twice-yearly equinox. An equinox is a day when the hours of W O R D S M AT T E R The word “equinox” comes from the daylight and the hours of night are of equal length. The vernal, or Latin equi, meaning equal, and nox, spring, equinox occurs about March 21. The autumnal, or meaning night. autumn, equinox occurs about September 22. The Mayans of Central America built an enormous cylinder-shaped tower at Chichén Itzá in about 1000 C.E. to celebrate the two annual equinoxes. The ancient Egyptians built many pyramids and other monuments to align with the seasonal position of certain stars. For example, the entrance passage of Khufu, the Great Pyramid at Giza, once lined up with Thuban, a star in the constellation Draco. At the time the pyramid was built, starting about 2700 B.C.E., Thuban was the closest star showing true north. First Nations in the western regions of what is now Canada also used large rocks to build “medicine wheels.” In these circles, key rocks were aligned with the bright stars that rose at dawn, such as Aldebaran, Rigel, and Sirius. As well, many First Nations built rock installations to predict when it was the right time in the year to plant or Figure 9.7 The Moose Mountain medicine wheel harvest crops or prepare for hunting and fishing (Figure in Saskatchewan is an example of many created by 9.7). These structures were remarkably accurate, as many the Plains Indians to predict the start of seasonal still show today. rites and migrations. This one is dated to 300 C.E.
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Figure 9.8 In the geocentric model, Earth was at the centre and stars were thought to be fixed to the inside of the “celestial sphere,” like stars glued on the unmoving ceiling of a dome. Over time, with improved observations, this model was shown to be wrong.
From our perspective on Earth, everything in the sky appears to be in motion. The Sun rises and sets. The Moon, in its ever-changing phases, travels across the sky. Planets shift against a background of stars. Even constellations appear to change position in the sky during the year. Just as today we use what technology and science we have to find answers to our questions about the world around us, so our ancestors used the knowledge and technology they had to make sense of the constant change they observed in the sky. Not surprisingly, then, it looked to early observers as though all celestial objects in the solar system revolved around Earth. Gradually, as more evidence was gathered and viewing technologies improved, that idea changed.
Geocentric Model
Figure 9.9 This composite image of Mars was taken in 2003 over the course of two months. It clearly shows the phases of the planet in retrograde motion.
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More than 2000 years ago, the widely held belief was that Earth sat at the centre of the universe. Building on the teachings and views of others, including the great Greek philosopher Plato, Aristotle was one of the first people to describe in detail a geocentric (Earth-centred) model to explain planetary motion. In the model, Aristotle showed Earth, with the Sun, Moon, and five known planets revolving around it (Figure 9.8). To explain why the distant stars did not move, Aristotle suggested they were attached to the outside sphere. The concept of the geocentric model continued to be developed by early scientists, including the Greek astronomer Ptolemy in the second century. Ptolemy’s model enabled the forecasting of many astronomical phenomena, such as the changing phases of the Moon. Still, some observations of planetary motion were puzzling. For example, Mars, Jupiter, and Saturn appeared to loop backward for a few months in their route across the sky (Figure 9.9). This apparent reversal of the planets’ path relative to the starry backdrop is called retrograde motion. Various astronomers proposed changes to the geocentric model to better account for planetary behaviour, but most of these adaptations were extremely complicated.
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Heliocentric Model The geocentric model of the solar system lasted for almost 2000 years. Gradually, however, new observations, helped by improvements in telescopes and other technologies, led to the rethinking of another model. The heliocentric (or Sun-centred) model had been proposed by the Ionian Greeks as far back as 500 B.C.E., but not until 1530 did it receive new attention. That was when Polish astronomer Nicholas Copernicus revived the idea that the Sun was at the centre of the universe and Earth and the planets orbited around it (Figure 9.10). Awareness of two key aspects about planetary orbits helped add support to the heliocentric model. One was the relationship between a planet’s orbital radius and the planet’s speed of orbit. The other was the fact that planetary orbits are elliptical and not circular.
Mercury Jupiter
Earth Moon
Sun Venus Mars
Saturn Figure 9.10 The heliocentric model of the solar system put the Sun at the centre of the universe. At the time, it was considered to be an outrageous idea.
Orbital Radius In the heliocentric model, each planet orbits the Sun at a different distance. A planet’s distance from the Sun is called the planet’s orbital radius. The shorter the orbital radius, the faster the planet moves in its orbit. Therefore, Earth, which is closer to the Sun than Mars is, orbits the Sun more quickly than Mars does. This occurs not just because the orbit of Earth is shorter than the orbit of Mars. Earth is also moving faster than Mars. In turn, Mars is moving faster than Jupiter, the next planet out from the Sun. This pattern is true for all the major planets, the minor planets, and even asteroids in the solar system. The reason is that the farther an object is from the Sun, the weaker is the effect of the Sun’s gravity on that object. The differences in orbital speeds explain why Mars, Jupiter, and Saturn display retrograde motion relative to Earth. In effect, Earth is speeding around its course faster than the other three planets are. It is as though you were in a track race and passing three other runners not only because you are moving faster, but also because you have the inside turn position, which gives you added advantage. When you pass the others this way, they appear to be moving backward relative to you.
Suggested Activity • C24 Quick Lab on page 350
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Figure 9.11 illustrates this for Mars. In the figure, both Earth and Mars are shown at five different times over a few 5 months. The line drawn from Earth 5 4 through Mars and out to the background 2 3 of stars shows how we see Mars in 3 4 relation to the backdrop. 2 1 Between positions 2 and 3, Mars 1 Mars Earth appears to go backward in the night sky. Position 3 in the figure also shows how, as they pass each other, Earth and Mars reach their closest proximity to one Figure 9.11 The effect of retrograde motion between Earth and Mars. Earth orbits faster and closer to the Sun than Mars does. About every another. two years, Earth catches Mars and passes it. This makes Mars appear to A little less than 100 years later, a lag for a while, tracing a backward path against the starry background. new generation of scientists provided solid evidence for Copernicus’s theory. They did this with the help of a major technological invention, the telescope. Notable among these scientists was the renowned Galileo Galilei of Italy. In the 1600s, using a telescope not much stronger than the standard binoculars you might use today, he was the first person to view mountains on the Moon, a “bump” on either side of Saturn (later found to be the outer edges of the planet’s rings), spots on the Sun, and moons orbiting Jupiter. Elliptical Orbits Even though Galileo’s discoveries added credibility to the Copernican ideas, the model could still not predict planetary motion very accurately. A German mathematician, Johannes Kepler, came up with the next piece of the puzzle. Using detailed observations of the movement of the planets (observations carefully recorded by the Planet’s path Danish astronomer, Tycho Brahe), Kepler discovered what was missing from the Copernican ideas. The orbits of the planets, Sun’s position he realized, were ellipses and not circles (Figure 9.12). An ellipse is somewhat like a slightly flattened circle. Today, all astronomical observations continue to support the heliocentric model of our solar system. It is also the guide we use when studying other star-and-planet systems. Figure 9.12 The planets orbit the Sun in elliptical, not circular, orbits. 344
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Learning Checkpoint 1. In the northern hemisphere, what is the: (a) summer solstice and when does it occur (b) winter solstice and when does it occur 2. What is the main difference between the geocentric model and the heliocentric model? 3. Define retrograde motion, and make a sketch to support the definition. 4. The orbits of the planets are not exactly circular. What shape are they?
The Evolution of Astronomers’ Tools Step by step, our understanding of space and Earth’s place in it has progressed, thanks in large part to the improvement of the tools available to observe, record, measure, and analyze what we see. Humans are very inventive and have worked hard over the centuries to develop tools to help them better understand the astronomical phenomena and their mysteries. Sundials, for example, have been used for more than 7000 years to measure the passage of time (Figure 9.13). Ancient Egyptians invented a device called a merkhet to chart astronomical positions and predict the movement of stars. About the second century C.E., Egyptian astronomers also designed a tool called a quadrant to measure a star’s height above the horizon (Figure 9.14). Arabian astronomers used the astrolabe for centuries to make accurate charts of star positions. In the 14th century, astronomer Levi ben Gerson invented the cross-staff to measure the angle between the Moon and any given star. With each of these innovations, astronomers made new discoveries and gained more knowledge about what they were seeing.
quadrant
astrolabe
cross-staff
Figure 9.13 The upright part of a sundial casts a shadow onto the face of the dial. The position and movement of the shadow provide an accurate way to track time, at least during sunny days.
Figure 9.14 The inventiveness of astronomers led them to develop many tools to help them observe, record, and measure celestial activity.
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Optical Telescopes The invention of the telescope in the late 16th century was a technological breakthrough that revolutionized astronomy. Suddenly, astronomers such as Galileo had a means of collecting light and magnifying the images it revealed. This way they could see more in the night sky than had ever been possible before. Telescopes detected exciting details about Earth’s closest planetary neighbours and revealed the existence of other celestial objects in the solar system. With the assistance of the telescope, astronomers learned that the size of what lay beyond Earth was much greater than ever they had imagined. The first telescope ever designed was a simple refracting telescope. Refracting telescopes use two lenses to gather and focus starlight, as shown in Figure 9.15. However, there is a limit to how large a refracting telescope can be. Any diameter over 1 m causes the glass in the lens to warp under its own weight. Trying to see through a lens when that happens is like trying to view details of the Moon by looking through the bottom of a pop bottle. Reflecting telescopes use mirrors instead of lenses to gather and focus the light from stars. At one end of a reflecting telescope is a large concave mirror (Figure 9.16). The mirror is made from glass-like material that is coated with a thin layer of metal. The metal, such as aluminum, is polished to a shiny finish so that it can reflect even the faintest light it receives. Reflecting telescopes are often located high on mountaintops to get the clearest view of the night sky possible.
eyepiece lens
primary light-gathering lens
Figure 9.15 A refracting telescope
eyepiece lens primary light-gathering mirror focus
secondary mirror
Figure 9.16 A reflecting telescope
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Ground-based Optical Telescopes An example of a ground-based (sometimes called Earth-based) telescope is the Canada-France-Hawaii Telescope, located on Mauna Kea in Hawaii (Figure 9.17). In 2007, it detected the most distant black hole yet discovered in the universe. This black hole is located nearly 13 billion ly away. It was detected because the telescope was able to view glowing gas falling into the hole. Space-based Optical Telescopes Although remote mountaintops make excellent sites for building and operating telescopes away from light pollution and air pollution, astronomers are still at the mercy of the weather. Clouds, humidity (moisture in the air), and even high winds can interfere with stargazing. For this reason, telescopes positioned high above Earth’s atmosphere have a tremendous advantage over ground-based telescopes. Canada’s space telescope MOST, launched in 2003, is the size of a suitcase and has a mirror only 15 cm across (Figure 9.18). MOST stands for Microvariability and Oscillations of Stars. Despite its tiny size, it has amazing capabilities. It can detect hidden features on the inside of stars by recording vibrations that occur on their surface. Its two-year mission was so successful that it has been used to analyze planets that are not visible to even the best ground-based telescopes. The Hubble Space Telescope, shown in Figure 7.28, is a reflecting telescope that orbits about 600 km above Earth. It uses a series of mirrors to focus light from extremely distant objects. Launched in 1990, the Hubble is a cylinder just over 13 m in length and 4.3 m in diameter at its widest point. Gradually, it will be phased out of service. By 2013, its replacement, the James Webb Space Telescope, will go into operation (Figure 9.19). Located 1.5 million km from Earth, the James Webb will get even clearer images of more remote objects than the Hubble.
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Figure 9.17 The Canada-France-Hawaii Telescope, located on Mauna Kea, Hawaii
Figure 9.18 Canada’s MOST space telescope can image planets in other solar systems.
Figure 9.19 Model of the James Webb Space Telescope, which dwarfs a crowd of visitors gathered to see it
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Radio Telescopes
During Writing Signal Words for a ProblemSolution or Cause-and-Effect Organization The presence of words such as when, if, however, although, only, and but may signal a problem-solution or cause-andeffect text pattern. Scan the pages on telescopes for signal words that might indicate whether they are written in one of these two patterns. Use these signal words to organize your findings for Quick Lab C22.
Optical telescopes collect only visible light. Studying radio waves emitted by objects in space gives astronomers data that are not available from the visible spectrum. The objects that emit radio waves include stars, galaxies, nebulae, the Sun, and even some planets, both in our own solar system and in other star-andplanet systems. With the development of radio telescopes, telescopes that detect and record radio waves, astronomers were given a way to collect these signals and focus them. Sophisticated electronics and computers then allow the collected information to be mapped. The radio telescope at the Arecibo Observatory in Puerto Rico is the largest in the world (Figure 9.20).
Figure 9.20 The world’s largest radio telescope, at the Arecibo Observatory in Puerto Rico. Its dish measures 305 m in diameter.
Take It Further The Sudbury Neutrino Observatory observes the Sun from a distance of 2300 m — from underground. Neutrinos are particles produced during the nuclear reactions in the Sun. They pass through solid rock easily but are difficult to detect. Placing the detector underground prevents radiation from other sources getting through. Find out about the neutrino detector, what it is filled with, and how many photo (light) detectors it uses. Begin your research at ScienceSource.
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Radio telescopes have several advantages over optical telescopes. Radio waves are less affected by weather and can be detected during the day and at night. They are also not distorted by clouds, pollution, or the atmosphere as light waves are. It was radio telescopes that also helped establish the Big Bang theory. They detected cosmic background radiation, the microwave radiation believed to be left over from that first massive and instantaneous expansion of the universe. Radio telescopes have also detected enormously powerful energy sources at the edge of the visible universe. These objects, called quasars, put out as much energy as an entire galaxy but may be no larger than a solar system. The nature of quasars is not yet understood, but astronomers continue to learn more about them by using radio telescopes.
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STSE Quick Lab
Human Time and the Sky Every culture and civilization in the past observed the sky closely, drawing knowledge and inspiration from the astronomical phenomena and celestial patterns there. Marking time from celestial motions was especially important. Using what they saw, early people developed various means of predicting seasonal changes and of planning annual activities, from planting and fishing to celebrating the solstices.
Purpose To research ways that early people learned to track time from celestial observation
Procedure 1. You will work in a small group. Your teacher will assign each group an ancient culture or civilization whose methods of telling time and keeping track of time you are to research. Examples will include cultures and civilizations from around the world.
2. ScienceSource You will do your research by using the Internet and library materials. 3. After your group has completed its research, summarize and organize your key findings and present them on a poster. Use diagrams, photographs, maps, and any other appropriate images to illustrate your findings. With your teacher’s permission, hang your poster up.
Questions 4. Read the posters presented by other groups. How was time-keeping similar across cultures and civilizations? How was it different? 5. Imagine all watches and calendars disappeared from our lives. What observations and cues from the world around you could you start to track to help mark the passage of: a day? a week? a month? a year? a decade?
C23 Just-in-Time Math Showing Different Types of Data on the Same Graph Displaying several kinds of information on the same graph enables you to compare related data in a useful way. For example, climate graphs plot temperature using a line and precipitation using bars together on the same graph. See Skills Reference 9 for guidance on graphing. Example: Create a graph to show the climate data for Pickering, Ontario. Plot the temperature data as a line graph and the precipitation data as a bar graph. Step 1: Use the vertical scale (y-axis) on the left side of the graph for the temperature data. Use the vertical scale (the second y-axis) on the right side of the graph for the precipitation data. Set the scale for each data set separately, keeping in mind that both must fit on the same graph. For temperature, a scale of –10°C to 25°C might be chosen. For precipitation, the scale might be 0 mm to 400 mm.
Table 9.1 Climate Data for Pickering, Ontario Season Spring
Average Daily Temperature (°C)
Average Total Precipitation (mm)
7
250
Summer
20
300
Autumn
10
270
Winter
–3
200
Step 2: Mark the four seasons, spaced evenly apart, along the horizontal edge (x-axis) of the bottom of the graph. Step 3: Plot the temperature data first, connecting the dots with a smooth line. Then, plot the precipitation data, creating narrow bars for each season. Step 4: Title the graph, and label the three axes clearly.
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DI Key Activity
C24 Quick Lab Plotting a Planet’s Orbital Radius and Its “Year” No other planet in the solar system revolves around the Sun in the same length of time as Earth. Earth’s “orbital period” (the time to complete one revolution of the Sun) is a year. The shorter the orbital radius a planet has, the faster the planet moves in its solar orbit and the faster it completes a revolution of the Sun. Therefore, measured in “Earth years,” a year on Venus is less than a year on Mars, and a year on Mars is less than a year on Jupiter.
Purpose
Materials & Equipment • pencil
Procedure 1. Refer to Skills Reference 9 for additional guidance in creating your graph. 2. Review the data in Table 9.2, and determine what scales for your graph will be appropriate. Remember that the scale for each y-axis must allow the largest values for those two data sets to fit on the same sheet of graph paper. Table 9.2 Orbital Radius and Orbital Period, by Planet Orbital Radius (AU)
Orbital Period (Earth year)
Mercury
0.39
0.24
Venus
0.72
0.62
Earth
1.00
1.00
Mars
1.50
1.88
Jupiter
5.30
11.9
Saturn
9.50
29.5
Uranus
19.0
84.0
Neptune
30.0
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5. How many revolutions of the Sun can Earth complete in the time it takes Jupiter to revolve once? 6. How does a planet’s orbital radius compare with its orbital period?
• sheet of graph paper
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4. Plot the figures from Table 9.2 onto the graph. Create a bar graph to show the orbital radius values. Create a scatterplot to show the orbital period values.
Questions
To make a combined bar graph and scatterplot to illustrate the relationship between a planet’s orbital radius and the planet’s orbital period
Planet
3. Draw the x-axis, and mark off the categories (the eight planets) at equal widths. Label this axis “Planets”. Draw the two y-axes. Label the left one “Orbital Radius” and the right one “Orbital Period.”
7. (a) Using a calculator, take the orbital radius for Saturn and find the cube of this value (that is, t × t × t). Then, take the orbital period for Saturn and find the square of this value (that is, t × t). Compare the two numbers produced in the calculation. (b) Repeat the steps in (a) using values for Neptune. Note the result. (c) Use the results from steps (a) and (b) to form a hypothesis that shows the relationship between a planet’s orbital radius and its orbital period. Then, test your hypothesis using data for one or two other planets. 8. Describe how seeing data plotted on a graph rather than just presented in a table can make relationships easier to analyze.
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CHECK and REFLECT
Key Concept Review 1. List three reasons that early cultures had for observing and keeping track of celestial phenomenona.
8. Describe one discovery made by: (a) the ground-based Canada-FranceHawaii Telescope (b) Canada’s space-based MOST telescope
2. Name the day in the year with the: (a) greatest amount of daylight (b) shortest amount of daylight 3. What is equal about the two equinoxes that occur each year? 4. Describe the geocentric model of the universe in terms of the position and movement of the Sun, Earth, and the stars. 5. The diagram below shows a time-lapse image of a planet’s changing position in the night sky as viewed from Earth. What term describes this type of movement?
Connect Your Understanding 9. Early cultures and civilizations kept track of seasons by observing the changing position of celestial objects during both the day and night. List at least four ways in which early people would have applied this knowledge of season shifts in planning their daily lives. 10. Use a diagram to show why Mars appears brightest to us on Earth at a certain time of the year. 11. Why can radio astronomers make observations at any time during the day, but optical astronomers are limited mostly to making their observations at night?
Reflection
Question 5
6. Name three tools developed and used by early astronomers before the invention of the telescope.
12. This section included three activities, all of which differed from each other in purpose and skills focus. Comment on the difficulties and successes you experienced in carrying out each of the activities you completed. For more questions, go to ScienceSource.
7. Explain the main difference between a refracting telescope and a reflecting telescope.
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Benefits of Space Research and Exploration
Here is a summary of what you will learn in this section: • Space research and exploration expand our knowledge of the universe while also producing many technological spinoffs that have practical applications on Earth. • Artificial satellites in orbit around Earth serve a range of purposes, including communications, surveillance, and environmental monitoring. • Canadian organizations and individuals make significant contributions to space technology, research, and exploration.
Figure 9.21 This photograph, named “Earthrise,” was taken by astronaut William Anders during the historic Apollo 8 mission to orbit the Moon in 1968.
Earthrise Until 1968, we on Earth did not really have a good sense of what our home planet looked like from the viewpoint of far away. The image shown in Figure 9.21, however, changed humanity’s view of Earth. This picture was taken from the Apollo 8 spacecraft that orbited the Moon in 1968, carrying three astronauts. For the first time, humans saw their small blue-and-green planet against the darkness and depth of space. “Earthrise,” as the image came to be known, appeared around the world on newspaper front pages, magazine covers, and postage stamps. It was this picture that helped people realize that our planet does not have infinite resources and that even the seas and the atmosphere are finite. The main purpose of the Apollo 8 program was to advance our exploration of the Moon. Yet the true legacy of the mission was that it helped a whole generation of people gain a greater appreciation of their home, the planet Earth. 352
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C25 Quick Lab The Value of the View from High Above Earth Space exploration benefits us in many non–space use ways. Satellite imaging is one of those ways.
Questions 3. For the satellite images in Figure 9.22:
Purpose
(a) What are the main differences you see between the before and after images?
To analyze the information from satellite images taken of Earth and use it to guide decision-making
(b) What important information do the images reveal that would have helped emergency relief workers make plans to bring aid to the community?
Procedure 1. Study each set of satellite images in Figures 9.22 and 9.23. 2. Working with a partner, look for the differences revealed by each set of images in the two figures. Discuss what you interpret in each case.
(c) Suggest how these images could be used in long-term reconstruction efforts. 4. For the satellite images in Figure 9.23: (a) What are the main differences you see between the before and after images? (b) The forests surrounding the mountain are starting to decline because of water shortages. What evidence from the images can you find to explain what might be causing the forests to recede?
before
after
5. Suggest another location in the world where before and after satellite images could be useful. Explain what you think they might show.
Figure 9.22 Banda Aceh, a coastal town in Indonesia,
before and the day after it was devastated by a tsunami in December 2004
before
after
Figure 9.23 Mt. Kilimanjaro, the tallest mountain on the continent of Africa. The first image of the mountain was taken in 1976, and the second one was taken 30 years later.
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The Many Benefits of Space Research Space research and exploration are constantly revealing new details about the size and complexity of the universe. This knowledge helps improve our understanding of Earth, our solar system, and the origins of everything around us. At the same time, many of the technologies invented to advance space research and exploration are now aiding us in our everyday lives on Earth. From faster, safer airplane trips to the widespread availability of cellphone communication and improved fire-fighting equipment (Figure 9.24), we see the spinoffs of space research all around us. A spinoff is a secondary beneficial effect or product of a thing or an activity. Figure 9.24 The fire-resistant suits and compact breathing apparatus used today by firefighters are spinoffs from innovations developed for astronauts.
Space Transportation Technologies In the decades since the first simple satellites, the science of rocketry has sent humans on round trips to the Moon and sent robots to investigate our neighbouring planets. It has also launched the Hubble Space Telescope and, in 2013, will send the James Webb Space Telescope into space. There are currently four main types of spacecraft in use. • Rockets lift small capsules containing crew, equipment, or satellites into orbit and beyond. The new generation of human space flight spacecraft is the Orion crew explorarion vehicle (Figure 9.25). • Space shuttles transport personnel and equipment to orbiting spacecraft. • Space stations are orbiting spacecraft that have living quarters, work areas, and all the support systems needed to allow people to live and work in space for extended periods. • Space probes contain instrumentation for carrying out robotic exploration of space.
Figure 9.25 The first Orion crew exploration vehicle is due to begin servicing the International Space Station by 2015.
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The International Space Station The International Space Station, assembled in space in stages since 1998, orbits at 400 km above Earth. It is the largest spacecraft ever built. One of Canada’s most significant contributions to the space station has been the Canadarm2, shown on the opening pages of this unit. This robotic device, one of three designed and built in Canada by a Canadian company, can move astronauts around as they work outside the space station. It can also bend around corners and grasp objects with its computer-controlled “fingers.”
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Product Technologies Many items, materials, and systems first created for a space application have been put to practical use on Earth. For example, astronauts even in low orbit in space are at risk of receiving harmful levels of radiation emitted by the Sun. As a result of research into how to protect astronauts from such exposure, we now have better radiation detectors on Earth and better ways of shielding people during radiation-related medical treatments. From cancer treatments and pacemakers to mechanical insulin pumps and flat-screen televisions, the technological benefits created by space research are now everywhere in our daily lives. All of these innovations, many developed for use in the International Space Station, got their start fulfilling a purpose in space exploration. Table 9.3 lists some of the spinoff applications of space technology. Opportunities for the economic development of space resources are also being investigated today, including such ideas as offering tourist space flights, building hotels on the Moon, and mining minerals on asteroids.
Figure 9.26 Modern comforts such as padded bicycle seats are a spinoff of space research.
Figure 9.27 Modern thermometers are another space research spinoff.
Table 9.3 Spinoff Products Developed for Use in Space Exploration But Now Adapted for Use on Earth Product
Purpose for Space Exploration
Example of Spinoff Use on Earth
Dehydrated food
To provide astronauts with meals for long flights
Portable camping food; emergency food supply; food storage
Miniaturized computers and robotics
To build computer robotics for space vehicles and probes
Emergency response robots (e.g., to inspect explosive devices)
Scratch-resistant plastic coatings
To protect astronauts’ helmet visors
Coating for plastic eyeglass lenses (increases the scratch resistance 10 times)
Memory foam (an open-cell foam that evenly distributes the weight of a load)
To pad aircraft and spacecraft seats to buffer astronauts from the impact of landings
Motorcycle and bicycle seats (Figure 9.26); pillows and mattresses for bedridden patients to reduce bed sores
Antibacterial water filter
To prevent bacterial growth in water filters and so keep astronauts from becoming sick in space
Household water purification filters
Infrared thermometer
To measure the temperatures of stars
Medical thermometers that can take the body’s temperature faster and more accurately than before (Figure 9.27)
Ionization smoke detector
To detect possible fire outbreaks on board a spacecraft
Sensitive household smoke detectors
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Satellite Technologies
Figure 9.28 Sputnik 1, launched in 1957, had a radio transmitter on board which could be picked up by shortwave radios.
Perhaps the greatest single positive impact on global society has occurred with the development of artificial satellite technologies. An artificial satellite (or, simply, satellite) is a device placed in orbit around Earth or another celestial object. The first satellite was launched in 1957 by the former Soviet Union (Figure 9.28). It was only the size of a football, and its purpose was to demonstrate that sending a device into orbit was possible. Less than a month after the successful trial of Sputnik 1, Sputnik 2 was launched. This satellite was much larger, weighing 500 kg. All the world watched, partly because the success of this new technology introduced the concern that a nuclear weapon could be sent into orbit and then landed in another country. In response, the United States launched a satellite of its own in 1958, called Explorer 1.
Communications Canada was the third country in the world to launch a satellite. Called Alouette 1, it collected data about the extreme upper regions of the atmosphere, where many future satellites would be placed. Canada also launched a series of Anik satellites beginning in 1972. Anik 1 enabled the whole country to have telecommunications coverage. It transmitted 12 television channels to large ground stations across the country. The signals were then rebroadcast by regional ground-based transmitters already in place. The Anik satellites were particularly important in connecting Canada’s northern communities with the rest of the country. The use of these satellites was innovative and set a trend for future communications satellites worldwide. Today, communications satellites circle the globe. Anik F3 was launched by Telesat Canada in 2007 from a launch pad in French Guiana, South America (Figure 9.29). It occupies a geostationary orbit above Earth. A geostationary orbit is one in which a satellite orbits Earth at the same rate as Earth rotates. This makes the satellite appear stationary (staying still) when viewed from the ground, and enables receiving antennas to be permanently pointed to one spot in the sky. Anik F3 has a mass of 5900 kg, which is 10 times the size of the original Anik satellite. It provides broadcast and broadband Internet services across Figure 9.29 Anik F3, a Canadian communications satellite North America. launched in 2007 356
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Tracking Devices If a person, animal, or vehicle is fitted with a special transmitter, then someone with the right tracking device can know the position of that transmitter. Wildlife researchers, for example, often use tracking devices to study the movements of migrating animals such as caribou, whales, and hummingbirds. The Global Positioning System (commonly referred to as GPS) is the most widely available tracking system today. It relies on a group of satellites that transmit low-energy microwave signals (Figure 9.30). These signals are picked up by small receivers that people on Earth can easily carry by hand or even in a shirt pocket (Figure 9.31). The minicomputer in a GPS receiver can show you your location and, if you are walking or in a vehicle, show how fast you are moving and in what direction. Today, GPS has become widely adopted for commercial applications, map-making, surveying, and personal use. Many taxis and rental cars are also GPS-equipped so that the vehicles’ use and location can be monitored.
Figure 9.30 With more than two dozen satellites in orbit, there are at least three above the horizon, relative to a person’s location on Earth, at any one time.
Suggested Activity • C27 Quick Lab on page 362
Figure 9.31 The computer in a GPS receiver calculates your position and displays it on the receiver’s screen.
A recreational use of GPS is for geocaching, a popular outdoor treasure-hunting game. Participants use a GPS receiver to hide a waterproof container, or geocache, that contains a “treasure” (often a trinket of little value). Other players then use their own hand-held GPS receivers to try to find the cache (Figure 9.32). When one is found, it is opened and the treasure is removed. Geocaching enthusiasts estimate that at any one time, more than a million geocaches are in place around the world, on every continent including Antarctica.
Figure 9.32 Geocaching uses GPS technology to play a game of “hidden treasure.”
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During Writing Match Organization to the Purpose and Audience Once writers know their purpose and audience, they can choose an organizational pattern. Should it be cause and effect, problem-solution, or time order/sequential? Think about this as you carry out the writing task for Quick Lab C26.
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Remote Sensing and Digital Imaging When a series of clouds drift by on a sunny day, it is not possible from the ground to see that these clouds may be part of a weather pattern that covers half a continent. When waves lap ashore on the beaches of the Great Lakes or James Bay, it is not possible to notice decades-long patterns such as changes in average water level. On the other hand, one satellite image may show the changes in air quality right across a continent, or measure the effect of flooding or forest fire damage across a whole region. Only from the vantage point of space can the entire view of an 800 km hurricane be seen with its advancing storm front on the outside to the quiet centre of its eye. Satellite imaging can show changes over time. Many satellites remain operational for decades, allowing the collection and archiving of data for later analysis. Earth observation satellites already show us the results of the constant slashing and burning of the world’s rainforests, as shown in Figure 9.33, and the presence of a hole in the protective ozone layer. Long-term monitoring provides data to help us assess the impact of human populations on landscapes and oceans. In viewing Earth, satellite observation equipment must make a trade-off between how much of Earth it can observe at one time and the amount of detail in the image. A high-resolution image can show individual buildings, roads, cars, and even people. However, the higher the resolution, the longer it takes to cover a given area. For the assessment of natural disasters due to hurricanes, flooding, and volcanic activity, medium-resolution instruments covering a wide area are used.
(a)
(b)
Figure 9.33 The same area of rainforest shown (a) several years ago and (b) today. Note how the forest cover has changed.
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Envisat (for “environmental satellite”), launched by the European Space Agency, is part of a network of satellites operated by various nations around the world to observe Earth. Launched in 2002, the Envisat satellite is packed with an array of sensors for studying the atmosphere, the oceans, land surfaces, and ice (Figure 9.34).
Figure 9.34 Envisat image showing three of the Great Lakes
Real-Time Imaging Not all satellites observe the Earth by taking pictures. For example, the GOCE satellite (Gravity Field and SteadyState Ocean Circulation Explorer), launched in 2009 by the European Space Agency, makes measurements of the subtle variations in Earth’s gravity (Figure 9.35). The gravity sensed by a passing satellite is affected by the distribution of matter beneath it. For example, the existence of a mountain range below a satellite increases the gravity slightly. Similarly, a mountain located under the sea would also affect the gravity. It is expected that the GOCE satellite will advance human understanding of ocean circulation, sea-level change, climate change, volcanoes, and earthquakes.
Figure 9.35 The GOCE satellite in orbit
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Take It Further Complete coverage of Canada’s lands and oceans is being made by a group of satellites called the RADARSAT Constellation. Find out the role of these satellites in maritime surveillance, disaster management, and ecosystem monitoring. Begin your research at ScienceSource.
Image © 2008 Digital Globe. © 2008 Tele Atlas. © 2008 Google
Figure 9.36 Images like this of the Parliament Buildings in Ottawa are available free on the Internet.
As improvements are made to sensing technology, data integration software, and broadband speed, researchers expect that soon data from many different satellites can be combined at once. This will make it possible to view current and past conditions on Earth. Such data will likely be available directly from the Internet, and may even be a hybrid of direct photography as well as computer overlays of information. Several sources on the Internet provide imaging now, some of which is freely accessible, such as mapping information (Figure 9.36). Even today, the millions of images taken over several years can be combined to show the “full picture” of Earth. Examples of interpreted real-time images include those showing Earth without cloud cover or at night, with population centres, burning rainforests, and natural gas flares all visible (Figure 9.37).
Figure 9.37 Earth's population centres are clearly visible at night from space, as shown in this composite image.
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STSE Quick Lab
Canadian Contributions to Space Research, Technology, and Exploration For more than 150 years, Canada has been an active contributor in a range of ways to space research, technology, and exploration. Many individuals and organizations have been involved. The federal government not only sponsors the Canada Space Agency but also provides financial support to many projects related to space research. Also active are Canadian universities, research and development organizations, and private companies and industry working in a range of fields, including aeronautics, satellite technology, and telecommunications. Today, Canadian astronomers, astronauts, robotics engineers, and dozens of other science and technology specialists collaborate with colleagues around the world to advance human understanding of space. In this activity, you will research the extent of Canada’s contributions in one particular area and then prepare a presentation to the class to share your findings.
Procedure 1. You will work in a small group. Each group will be assigned one of the following categories to research and write a short report on:
3. ScienceSource Options for research sources include the Internet, library books, journals, documentaries, and interviews with people who have special knowledge. 4. Carry out your research, making notes and gathering relevant photographs, artwork, and other graphic materials to include in your report. Work with your partners to develop an outline for the report. Assemble your findings, and decide how best to summarize and report them. 5. Web 2.0 Develop your group's report as a Wiki presentation, a video, or a podcast. For support, go to ScienceSource. 6. Present your key findings to the class.
Questions 7. Based on your own group’s research findings, explain what most impressed you about that aspect of Canada’s contributions to space research, technology, and exploration. 8. Based on the research and reporting of other groups, explain what most impressed you about those aspects of Canada’s contributions.
• Canada and Satellite Technology • A Timeline of Canada’s Work with the International Space Station • The History of Canada’s Astronaut Program • Current Areas of Research by Canadian Astronomers • The David Florida Laboratory (Figure 9.38) Alternatively, you may suggest an area of Canadian contribution to space study that you would like to research. Ask your teacher for approval before you begin. 2. In class: Once you know your area of research, brainstorm with your group the questions you have about the topic and what sources you think would provide the best information for your purposes.
Figure 9.38 Work in progress at the David Florida Laboratory near Ottawa
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C27 Quick Lab On Location with GPS How can three satellite signals “triangulate” someone’s location?
Purpose To illustrate in a two-dimensional way how the Global Positioning System helps a person determine his or her position on the ground
Materials & Equipment • handout of map showing showing satellite locations
Questions 5. The spot where all three circles meet on the map indicates your position. How well did your circles intersect? 6. Suggest how satellites know where their position is in relation to Earth. Table 9.4 Distance from Satellites to GPS Receiver Satellite
Distance to GPS Receiver (km)
1
760
2
900
3
610
• pencil • geometry compass
Procedure 1. Your teacher will give you an enlarged copy of the map shown in Figure 9.39. Imagine that you are standing in a location somewhere on this map when you turn on your GPS receiver. 2. Satellite 1 transmits a radio signal to the receiver in your hand, and the GPS device calculates that you are 760 km from the satellite. Using the compass, measure 760 km on the scale provided on the handout.
Hudson Bay satellite 3
MANITOBA satellite 1
QUEBEC ONTARIO
3. Next, place the compass point on the position labelled Satellite 1 and draw a circle that has a radius equal to the distance from the satellite. 4. Repeat steps 2 and 3 for Satellites 2 and 3, using the information in Table 9.4.
Thunder Bay
Ottawa Toronto
UNITED STATES
N
satellite 2
0
Figure 9.39 Satellite locations
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1000 km
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CHECK and REFLECT
Key Concept Review 1. Explain the difference between a space shuttle and a space probe. 2. Name three spinoff products developed for space exploration but now adapted for use on Earth. 3. Define artificial satellite. 4. Which nation launched the first artificial satellite and when? 5. What became available in Canada for the first time with the launch of the Anik 1 satellite in 1972? 6. What is a geostationary orbit? 7. What information about Earth can be found by making sensitive measurements of variations in Earth’s gravity?
Connect Your Understanding 8. The satellite image below shows a river emptying into a coastal area. What information might be revealed if scientists were to observe this area from space over several decades?
9. Explain how real-time imaging might be used to help people respond to natural disasters. 10. How can digital images of Earth be used by computers to detect information beyond the photographs themselves? 11. Suppose that high-resolution colour images of the surface of Earth are made and stored electronically. Computer software can analyze each image pixel by pixel, as well as count pixels, such as those representing water instead of land. Suggest ways the data from these images could be used in: (a) monitoring the health of rainforests (b) surveying changing crop yields over time (c) converting usable agricultural land into cities 12. List five important ways in which Canada has contributed to, and participated in, space research, technology, and exploration.
Reflection 13. For the next week, keep a “Space Tech Spinoffs in My Life” record. In a notebook, make a list each day of all the products or technologies you use, read, or hear about that were developed first for use in space research or exploration. For more questions, go to ScienceSource.
Question 8
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Costs and Hazards of Space Research and Exploration
9.3
Here is a summary of what you will learn in this section: • Space research and exploration are very costly, and travel into space involves a high degree of risk. • While space exploration offers extensive benefits to humans, there are many ethical, political, and environmental issues to be assessed and balanced against the benefits. • Living in the microgravity of space poses special risks to human health. • Today, serious consideration is being given to establishing a space base on the Moon and to sending astronauts — not just robotic probes — on a mission to Mars.
Figure 9.40 When such enormous problems as poverty are affecting millions of people on Earth, can we justify spending billions of dollars on space research and exploration? This is just one aspect of space study that is up for debate.
Questions about Space Exploration
Figure 9.41 Before selling a piece of property, you must own it first. Who owns the land on other planets or moons?
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There is no doubt that space exploration is exciting. There is also no doubt that we on Earth benefit greatly from space research and technology spinoffs, in addition to gaining valuable knowledge about the universe. At the same time, however, there remain many hard questions to ask and debate given the enormous amounts of money, time, and resources that countries spend on studying celestial objects and sending equipment and people into space (Figure 9.40). In the United States and Canada alone, space research and exploration programs cost billions of dollars every year. As more countries become involved in exploring space, many issues and questions have arisen concerning the use and responsibility for space and its resources (Table 9.5). For example, who owns space? Who is entitled to claim its resources, such as land or the mineral deposits on the Moon (Figure 9.41)? Is it right to spend billions of dollars to send a few people into space when millions of people on Earth do not have clean drinking water? Who is responsible for cleaning up the space environment? All of these ethical, political, and environmental issues will grow as matters of debate in the coming decades as we expand our interest in space research, exploration, and development.
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Table 9.5 Examples of Issues Related to Space Research, Exploration, and Development Issue Ethical
Political
Environmental
• Is it right to spend money on space exploration rather than on solving problems on Earth?
• Is it responsible to send humans into a high-risk envrionment like space?
• Who is responsible for protecting space environments from alteration?
• Do we have a right to alter materials in space to meet our needs? • How can we ensure that space resources will be used for the good of humans and not to further the interests of only one nation or group?
• Who owns space and its various celestial bodies? • Who has the right to use the resources in space? • Who will determine how space will be used?
• Who is responsible for cleaning up “space junk” (the equipment no longer used in space but left there in orbit)? • Who should pay for space junk clean-up?
• Should weapons be allowed in space?
C28
STSE Quick Lab
Who Owns Space? Fifty years ago, only a few countries had the technology, resources, and expertise to establish their own space programs. Today, there are more than a dozen space agencies in the world, including those from China and India (Figure 9.42). As travelling into space gradually becomes more commonplace, questions arise about the nature of our journeys.
Purpose To brainstorm some of the ethical, political, environmental, and economic issues connected to the ownership of space
Procedure 1. Read each of the questions that follow related to the ownership of space, the celestial objects in it, and their resources. Take a moment to think about how you would answer each question. 2. Your teacher will then lead the class in a discussion of space ownership. Share your thoughts and opinions in response to the questions. 3. After the class discussion, take a moment to summarize in your notebook your answer to each question. Were any of the responses you originally had in step 1 changed by the ideas that others in
the class expressed? In turn, do you think that some of your ideas and opinions might have changed the views others in the class held originally?
Questions 4. Are the resources of a moon, planet, or asteroid the property of the first nation to land on it or claim it? 5. Should space resources be owned only by nations rich enough to be able to afford the costs of reaching the site of those resources? 6. If we journey to other planets, should we go as ecotourists, only to observe the planet, leaving it in the condition we found it, or as pioneers, to settle and change the planet to meet human needs?
Figure 9.42 The Indian Space Agency’s first mission to the Moon landed in October 2008. The task of the mission is to map the entire lunar surface, showing the minerals present.
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Hazards of Travelling to and from Space Space exploration is a very high-risk undertaking. The space environment is not “human friendly.” Many hazards lie beyond Earth’s protective atmosphere. For example, both people and equipment face exposure to damage from intense solar radiation (Figure 9.43). There is also the potential for damage or total destruction from colliding with a comet, asteroid, or other space debris. Humans have learned to live in very extreme and varied environments on Earth and even in the International Space Station orbiting Earth. Still, many unforeseen risks and hazards remain. Accidents related to space travel may result not only in loss of human life, but in immense economic loss and the loss of countless years of work. In 1967, the three-member crew aboard Apollo 1 died during a training exercise when fire broke out on board the spacecraft. In the same year, a Russian Figure 9.43 Crew members on board the International cosmonaut died on re-entry into Earth’s atmosphere Space Station wear Russian-made spacesuits to when the capsule’s parachute failed to open. Two space protect them from hazards such as radiation. shuttle disasters have occurred, one on launch in 1986 (Figure 9.44) and the other on returning from orbit in 2003. Seven crew members were killed in each incident. After each disaster, crewed space programs were suspended until the causes were found and fixed. Equipment such as satellites and space probes to other planets are expensive. Both the Russians and Americans lost Mars probes shortly before the craft arrived at the planet. In both of those cases, hundreds of millions of dollars and thousands of hours of labour were lost. Nevertheless, human curiosity in learning about space persists. Rather than back away from space Figure 9.44 The space shuttle Challenger broke up 1 min after launch because fuel leaked through exploration, space agencies around the world have faulty O-ring seals and ignited. Seven crew continued to fund new projects, balancing risks and costs members died, including Christa McAuliffe, an against potential benefits as best they can. elementary school teacher.
Challenges of Living in Space People travelling and working in space do not need an Earth-like environment simply for comfort. It is a matter of survival. Humans have orbited Earth, flown far into space, landed on the Moon, and returned safely home. We are now hoping to put a human — not just a robotic machine — on another planet for the first time. 366
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Scientists believe we now have the technology to send a group of astronauts to Mars and back. This would not be a typical weeklong mission for space shuttle astronauts, nor would it be a few months as many astronauts in the International Space Station currently experience. Astronauts going to Mars would be gone for two to three years. Such long missions would pose many challenges. The physical environment is harsh. Living in confined quarters for such a long period of time can be stressful for people. As well, the long-term effects of microgravity on humans are still unknown. Microgravity is the condition in which the gravitational forces that act on a mass are greatly reduced. This condition is often likened to a feeling of weightlessness, similar to what you may have felt briefly on an elevator or an amusement park ride that drops quickly.
During Writing Weighing the Evidence When researching to develop a position on challenging issues, writers often create lists of the pros and cons, comparing and contrasting factors for or against an idea. They usually discover that one list is longer than the other. The longer list helps them to arrive at a point of view on the issue.
Challenges of the Physical Environment Space is a vacuum, with no air or water. It also contains many hazards for the spacecraft and its occupants, including the damaging effects of cosmic rays and solar radiation and the risk of being hit by space debris (Figure 9.45). Furthermore, because there is no atmosphere in space, temperatures can range from unimaginably cold in shadows to extremely hot in the full sun. No atmosphere also means that the gases that keep us alive on Earth, such as oxygen, do not exist in space. Neither does the pressure of the atmosphere, which keeps our bodily fluids from boiling at room temperature.
Challenges of Confined Living Long trips in a confined living space may lead to psychological problems. Imagine spending every minute of every day with one or two people for two years. Now, imagine spending those two years in an enclosure not much bigger than your classroom. Stepping outside for a break is not an option.
Figure 9.45 Damage to a spacecraft window from colliding with a small piece of space debris
Challenges of Microgravity To stay in space for extended periods, the human body must adapt physically to a microgravity environment. On Earth, gravity gives us our feeling of weight. This feeling is greatly reduced when a person is in orbit. Even on Mars and the Moon, the force of gravity is weaker than on Earth. People standing on Mars would feel only one-third of their weight on Earth. On the Moon, they would feel only one-sixth their normal weight.
Suggested STSE Activity • C31 Decision-Making Analysis Case Study on page 372
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Microgravity’s Effects on the Body Over extended periods of living in a microgravity environment, changes in the human body can have a negative effect on a person’s health. For example:
• The heart, which is mostly muscle, does not have to pump as hard as it normally does to circulate blood. This causes the heart to weaken (Figure 9.46).
Figure 9.46 Experiencing microgravity looks like fun, as these astronauts in training show, but the effects can be damaging to the body.
Suggested Activity • C30 Problem-Solving Activity on page 371
• The muscles we use for walking and lifting are not put into action as much. As a result, when humans are in a microgravity environment for long periods, their muscles start to weaken. Studies aboard the International Space Station show that within a relatively short time a person can lose 40 percent of his or her muscle mass. • Bones in microgravity have much less pressure on them than normal. This causes them to lose minerals, which in turn leads to the bones weakening. Astronauts may lose bone mass at a rate of about two percent per month in microgravity. • Red blood cell production in the body declines and the body’s immune system weakens, increasing a person’s risk of becoming infected and decreasing his or her ability to fight the infection.
Figure 9.47 An astronaut exercising in the Destiny laboratory of the International Space Station
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Reducing the Effects of Microgravity Astronauts exercise in space to help keep fit (Figure 9.47). On board the International Space Station, crew members spend at least one hour each day doing cardiovascular training (exercising their heart and circulatory system), as well as an hour of resistance training (like weightlifting). During the first few space missions that lasted more than a month, it was discovered that astronauts and cosmonauts who did not exercise while in space could not stand up for a few days after returning to Earth. A number of the health conditions caused by exposure to microgravity appear to be similar to those that happen when humans age. Studies of negative health effects related to microgravity may lead to new treatments for the care of the elderly, such as improved treatment for osteoporosis, a common type of bone degeneration experienced by many people on Earth.
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Challenges of Living on the Moon The best place to start an interplanetary flight may be from the Moon. The new Orion spacecraft planned by NASA will first be used as a transport vehicle to the International Space Station. Then, NASA plans to use Orion to ferry astronauts to the Moon for the first time since 1972. The new spacecraft will be a state-ofthe-art vehicle, incorporating the most recent electronics, propulsion systems, and life-support systems needed to make a successful round trip for the crew. Learning to live on the Moon will involve setting up a permanent base and making use of materials found locally. Lunar soil contains metals as well as materials to make concrete, glass, and ceramics. Water is too heavy to launch in quantity from Earth. The amount of water available on the Moon is unknown. It might be present in craters that are permanently in shadow, carried there by comets that crashed on the Moon. As well, given that hydrogen and oxygen are present in lunar rock, it might be possible to extract the two elements individually and combine them to make water. Getting around on the Moon will require some sort of vehicle, such as the “Moon buggy” used by astronauts during the Apollo missions (Figure 9.48). A new spacesuit, to enable mission members to spend more time outside the base, is currently in design. It will have increased comfort over current models, including safety features to prevent depressurization, and provide Figure 9.48 A lunar rover, also called a “Moon astronauts with increased protection against the everbuggy,” carried Apollo 15 astronauts across the present radiation from space. Moon’s surface to perform experiments.
Challenges in Visiting Mars Getting spacecraft and astronauts safely to Mars, even starting from the Moon, will be a difficult task. The metal hull of spacecraft cannot effectively shield astronauts from solar radiation for a flight that will take years. Some plastics, such as those being developed for new spacesuits, have more than 10 times the shielding ability of metal. Without this protection, the crew would be at greatly increased risk of cancer. The atmosphere on Mars is only about 1/100th the pressure of Earth’s and does not contain oxygen. Sandstorms are also common on the planet. Space exploration improves our knowledge and gives us beneficial technologies, but its hazards and costs are significant.
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To investigate the effects of a small number of people living in cramped quarters for extended periods, NASA has commissioned several test habitation sites. For example, in 2007, it set up the Flashline Mars Arctic Research Station on Devon Island in Canada’s High Arctic (Figure 9.49). A crew of seven lived together there for four months. The only time they were allowed to leave the facility — dressed in in mock spacesuits — was to practise carrying out tasks related to geology. Because the atmosphere on Mars will not support life, a protective suit will be necessary for anyone leaving the controlled environment inside the landing craft. Current spacesuits will not do the job. They are bulky and heavy, making them very difficult to move around in. As well, they must be pressurized with air to protect the astronaut from the damaging effects of the vacuum in space or low-pressure atmosphere on Mars. Much material will have to be sent ahead as well. This will include a fuel source and a water source. A pre-made facility to live in will also have to be assembled and air, heating, cooling, and other systems to support life installed in the facility. Just as important as figuring out how to Figure 9.49 The Flashline Mars Arctic Research Station on build and ship all of this material will be Devon Island in Nunavut. The facility sits at the edge of a planning how to transport the astronauts on the 23-km diameter impact crater made when an asteroid return trip to Earth. struck Earth 39 million years ago.
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STSE Science, Technology, Society, and the Environment
Sharing a Small Place in Space In addition to the environmental hazards that humans face in space exploration are many psychological challenges in sharing confined quarters with fellow travellers for long periods of time. A trip to Mars, for example, would take about 12 months one way. 1. Using a piece of cord 16 m long, lay out a square on the floor that measures 4 m × 4 m. Imagine that this outlines the size of the spacecraft that will be your home for the next year as you travel to Mars.
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2. Stand in the square with five other classmates. For about 1 min, move around with your fellow astronauts as best you can in the space provided. 3. Return to your desks and, with your group, think about all the problems that could arise during a long trip in this type of confinement. List the potential problems you identify. Then, for each one, suggest a solution. 4. After you finish, compare your problems and solutions with those noted by other groups.
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C30 Problem-Solving Activity
Skills References 3, 6
The Effects of Space Travel on Human Health Recognize a Need Space travel puts humans in extreme environments where they experience everything from tremendous force exerted on them during the rocket launch to almost no force during their time in microgravity. Our ability to stay oriented is the result of visual cues our eyes pick up and balancing cues our inner ears detect. With the loss of gravity, the balance cues conflict with our visual cues, causing disorientation.
Problem You and two or three other classmates have been assigned as mission specialists to research the effects of extreme conditions on humans during space flight. Your Earth-based research, simulating changes that the human body may undergo during a flight, will be used to prepare astronauts for their first journey into space.
Materials & Equipment • measuring tapes
• cardboard
• timers
• glue
• felt pens
• oral thermometer
• tape
• heart rate monitor
Criteria for Success The research team must (1) present an approved plan for carrying out experiments and (2) show what observations they made to back up their conclusions about the effects of space flight on the body.
Brainstorm Ideas 1. As a class, brainstorm ideas on forces that the human body might feel and how it might respond to different phases of space flight, such as a high velocity launch, microgravity in orbit, and the loss of a sense of up or down. For example, will an astronaut shrink under microgravity? What might happen to an astronaut’s sense of balance after he or she floats upside down?
Observing and recording observations Communicating ideas, procedures, and results in a variety of forms
2. Working in small groups, brainstorm various experiments you could conduct to test the effects discussed in step 1. Examples include: measuring the diameter of a leg under different conditions such as standing or being upside down against a wall; measuring height first thing in the morning and at the end of the day; and simulating the effect of increased blood flow to a person’s head during launch by having him or her lie on an incline with feet higher than the head.
Plan a Test Procedure 3. Select three effects that might occur on the human body, and plan a procedure to test each one. Consult your teacher if you need ideas.
Test and Evaluate 4. Perform the tests approved by your teacher, and collect your data.
Skill Practice 5. Repeat experiments as time permits to get the most reliable data possible. As you work, you may discover ways to improve your testing procedures. Discuss these with your teacher, and seek approval as needed for these modifications.
Communicate 6. Report your results on an information poster, in a slide show presentation, or by other means.
Figure 9.50 An astronaut in microgravity having the diameter of her leg measured
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CASE STUDY
C31
STSE Decision-Making Analysis
SKILLS YOU WILL USE Skills References 4, 6
Our Mess in Space: The Growing Problem of Space Debris Issue It is an unfortunate legacy of humans venturing into space. Since we started sending rockets, satellites, and various craft into space, the problem of debris left behind in low orbit and geostationary orbit around Earth has risen dramatically. Like the garbage dumps we have created here at home, the whole outer envelope around the planet at an altitude of between 200 and 35 000 km has been slowly filling up with space debris (Figure 9.51). Space debris ranges from broken bits off old rockets and all types of spacecraft to non-operating satellites, abandoned nuclear power units, and even small tools and cameras dropped by astronauts working outside their spacecraft. Estimates put the total number of pieces of space debris of 10 cm diameter and larger at about 17,000. Smaller fragments number in the millions. This accumulation of debris is creating many problems, usually as a result of collisions. When debris in the space environment collides, it does so at such high velocity that even a tiny bolt or bit of broken antenna can pierce a spacecraft hull or crack a telescope mirror (Figure 9.52). Collisions are therefore enormously costly, create even more
Thinking critically and logically Communicating ideas, procedures, and results in a variety of forms
debris, and pose a threat to the life of humans in space. The issue is therefore this: What is the best solution for dealing with the growing space debris problem now and in the future? Working with a small group, read more about space debris in the background information. Then, discuss and evaluate the points raised, to form a conclusion about what should be done.
Background Information In February 2009, two satellites collided over Siberia. One was a communications satellite owned by a company in the United States. The other was an old Russian satellite no longer in use. The collision destroyed both units, creating a “debris field” of more than 600 pieces scattered in the region of the impact. Not all collisions of space debris (also called space junk) occur between two objects as large as these were. However, the number of collisions is increasing annually as the amount of debris “out there” increases. Since 1957, more than 4500 missions have been sent into space. Each one has left behind its own bits of debris.
Figure 9.51 This image shows vividly the cloud of trackable objects cluttering what was once a space free of human-made material.
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STSE Decision-Making Analysis (continued)
While small bits of debris are very hard to detect in space, they travel at lethal velocities. For example, a piece of metal less than 1 mm in diameter can move at more than 10 times the speed of a bullet. Thus, at speeds of tens of thousands of kilometres per hour, the impact of even a speck of debris can pierce the hull of a spacecraft or section of a satellite. The damage can result in equipment not working (for example, knocking out communications signals to Earth). The need for costly repairs is the result. Worse is the risk of catastrophic effects on human life if crewed spacecraft are seriously damaged. Both the space shuttle and International Space Station are constantly being bombarded by tiny pieces of space debris. Maintenance is done regularly to repair and patch the damage. More than 80 windows on the space shuttle have had to be replaced during its period of operation. While the space station is usually able to alter course to avoid colliding with large tracked objects, it is being struck constantly by smaller objects. Of course, every collision results in more debris, as larger parts break up into ever smaller bits. In turn, more debris results in more collisions. Over the last decade, several space and research agencies, including those in the United States and Russia, have been keeping track of space debris, 10 cm to 1 m in diameter, using radar and optical equipment. Maps produced by the German-based
European Space Operations Centre, an arm of the European Space Agency, show the extent of the debris.
Analyze and Evaluate 1. Working in small groups, read through the information presented here. Then, use the following questions to analyze the issue. At the end, you will summarize your conclusions and recommend what actions, if any, should be taken. • What do you think about the issue of space debris? How pressing a problem is this? • Who should take responsibility for the debris that exists in space today? Is it acceptable to just leave it in “graveyard orbits” in space? • What should be done to manage the hazards posed by the debris? • What solutions can you suggest for reducing the problem in future? 2. ScienceSource As a group, decide whether additional information would help you answer the questions above and evaluate the issue. If so, begin your research at ScienceSource. 3. Web 2.0 Organize and summarize your conclusions and recommendations in one of two formats: a short written report or a PowerPoint presentation. 4. Listen to other groups’ views in a class discussion. Re-evaluate your group’s conclusions and recommendations. Did any of the arguments made by others who held a different point of view persuade you to reconsider your view? Explain why or why not.
Skill Practice
Figure 9.52 Every nick, dent, and scratch on this old section of the Hubble Space Telescope is marked in yellow. Constant collisions with small space debris mean that repairs must be made regularly.
5. Good recommendations clearly describe an action and who is reponsible for taking that action and by when. Reread your group’s recommendations and revise them if necessary to be clearer.
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CHECK and REFLECT
Key Concept Review 1. Space research and exploration raise many concerns. For each of the broad categories below, write two questions that are being debated these days. (a) ethical (b) political (c) environmental 2. Define microgravity. 3. How is the lack of an Earth-like atmosphere in space a challenge for humans travelling there and exploring other celestial objects? 4. Adjusting to living in microgravity conditions poses many challenges for astronauts, as shown in the image below. Describe some of the more serious negative effects on health for humans living for extended periods in a microgravity environment.
Connect Your Understanding 5. What is the best way for astronauts to counteract the effects of microgravity while they are in space? 6. Why might the metal hull of a spacecraft to Mars not be able to shield astronauts effectively enough to prevent them from getting an increased risk for cancer? 7. (a) What advantages are there to sending robotic probes into space rather than people? (b) What advantages are there to sending people into space rather than robotic probes? 8. Explain why the availability of water is a major concern during space exploration to the Moon or to Mars. Why can’t we just bring it with us? 9. Make a list of questions that need to be answered to guide humans in using space ethically. One such question might be: does landing on the Moon mean that you own it? 10. Although it might be possible to find volunteers to make a one-way trip to Mars, serious plans to visit the planet are usually challenged for ethical reasons. Explain.
Reflection 11. In this section, several of the activities encourage you to assess the pros and cons of space research and exploration. Did you change your opinion about any of the issues as you discussed them with others in your class? If so, in what way was your opinion changed and what arguments persuaded you to change? For more questions, go to ScienceSource. Question 4
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COOL IDEAS f r o m J AY I N G R A M
Save the Stars ... with Dark-Night Preserves
Jay Ingram is an experienced science journalist, author of The Daily Planet Book of Cool Ideas, and host of the Daily Planet on Discovery Channel Canada.
Light pollution hinders our ability to see the stars in the night sky. The more removed we are from the natural world, the more likely we are to ignore it, take it for granted, or even abuse it.
Thanks to the Hubble Space Telescope, we have hundreds of fabulous images of the universe. With even more powerful new telescopes in production, such as the European Extremely Large Telescope, we can expect to receive many additional images and in even greater detail than before. Yet, as our ability to explore space improves, here on Earth we are losing touch with our nearest and simplest connection with the universe: the night sky. The problem is that the artificial lights of our towns and cities are washing out the darkness of the night sky, making stars harder to see. A recent survey reported that about three of every four Canadians cannot see the Milky Way from where they live. That is an astonishing finding. The Milky Way galaxy, in which our Sun is just one of billions of stars, is our local neighbourhood in the universe. If you’re in the right place in midsummer on a clear night, you should easily be
The Cypress Hills Dark-Sky able to see the splash of brilliant white arcing Preserve is outlined above in yellow, straddling the across the sky. Not provincial border. The aim being able to see this there is to keep the area free from light pollution, thus is a serious loss. preserving the natural Fortunately, some darkness of the night sky. solutions to the problem are being found. Dark-sky preserves, places where night lighting is minimal, are being established all over the world. Other changes, such as not overlighting areas and ensuring that street lights point downward, not up, also help. Humans have marvelled at the night sky throughout history. It is important that we do not lose the ability to continue doing so.
Question 1. Does it matter to you that only a small fraction of Canadians are able to see the Milky Way? Explain your answer.
Space exploration improves our knowledge and gives us beneficial technologies, but its hazards and costs are significant.
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CHAPTER REVIEW
ACHIEVEMENT CHART CATEGORIES t Thinking and investigation k Knowledge and understanding c Communication
11. Define artificial satellite.
a Application
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12. What is the term used to describe a condition in which the gravitational forces that act on a mass are greatly reduced? k
Key Concept Review 1. Describe the summer and winter solstices in terms of the number of hours of daylight each receives on that day. k 2. Describe the equinoxes in terms of amount of daylight and night experienced on those days. k
13. Name four risks associated with space exploration. k
Connect Your Understanding 14. (a) How did the invention of the telescope help the science of astronomy? t
3. Make two sketches to show how the geocentric model and the heliocentric model of the universe differ from each other. c
(b) How has the invention of the nonoptical telescope further helped the science of astronomy? t
4. What does a refracting telescope use to collect and focus light? k
15. List five spinoffs from space-related research and exploration that benefit you in your daily life. a
5. What does a reflecting telescope use to collect and focus light? k
16. If a satellite has a geostationary orbit, does that mean it is staying still while Earth rotates? Explain your answer. t
6. What limits the size that a refracting telescope can be? k 7. Give three advantages of space-based optical telescopes over ground-based optical telescopes. t
17. Give three examples to explain what the following statment means: “Modern satellites have become excellent tools to help us better understand and manage Earth, its resources, and environment.” t
8. Name four types of spacecraft used to carry equipment or people into space. k 9. Give one example of a spinoff from spacerelated research or technology that now has: (a) an environmental use (b) a medical use
k
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(c) a domestic use
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10. (a) What is the name of one of Canada’s most significant contributions to the International Space Station? k (b) What does the item named in (a) do?
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Question 17
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18. What are some of the detrimental health effects associated with microgravity? k 19. Describe three challenges that would be faced by crew members living in a spacecraft making a long space flight to another planet, such as Mars. t 20. Why does it make sense to consider establishing a base on the Moon to help with efforts to send humans to Mars? t 21. The image below shows American astronaut Bruce McCandless making the first-ever untethered (meaning not connected) “spacewalk” in 1984. He manoeuvred more than 90 m out from the space shuttle Challenger. He was able to move about this way by releasing short bursts of compressed air. Compare the risks and benefits of spacewalking using compressed air rather than a tether. t
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Reflection 22. In this chapter, you read about many of Canada’s contributions to space research, technology, and exploration. Name an area of Canada’s contributions that you would like to find out more about. Explain why that area is of particular interest to you. c
After Writing Reflect and Evaluate The human brain likes to find patterns in the stars, the seasons, and even in textbook chapters. Types of patterns include time order, problemsolution, and cause and effect. Write a short paragraph explaining how knowing about patterns of text organization helped you in understanding what the writer was requesting in various activities in this chapter. Exchange your reflection with a partner and discuss.
Unit Task Link
Question 21
As you learned in this chapter, humans face an enormous number of hazards when they venture into space. The extreme environment beyond Earth and on other celestial bodies, including moons, asteroids, and planets, puts people at high risk of harm or even death. It also puts equipment at risk of damage or complete destruction. Furthermore, all of the work that goes into researching, planning, building, developing, and testing technologies, systems, and crews to go into space is very costly. Yet, between our desire to gain more knowledge about the universe and our ability to apply spacerelated technologies to improving life on Earth, the push to continue investing in space exploration remains strong. Thinking about all of the issues discussed in this chapter will assist you in carrying out the Unit Task.
Space exploration improves our knowledge and gives us beneficial technologies, but its hazards and costs are significant.
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Summary
KEY CONCEPTS
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Scientific evidence suggests that the universe began expanding from a single point
• Galaxies • Big Bang theory • Red-shifting in light spectra • Expanding universe
• An astronomical unit (AU) is a measure of distance equal to the average distance from the Sun to Earth. A light-year (ly) is a measure of distance equal to the distance light can travel in 1 year. (7.1) • Galaxies, which contain about 200 billion stars each, often occur in clusters, which in turn are often associated with other larger clusters. (7.2) • At least 90 percent of the universe is thought to be composed of dark matter. (7.2) • According to the Big Bang theory, the universe began 13.7 billion years ago at a single point and has been expanding since. (7.3) • The rate at which the universe is expanding is increasing. (7.3)
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The solar system formed 5 billion years ago, in the same way other star-and-planet
• Formation and life cycle of stars
• A star forms inside a nebula as gravity pulls dust and gas together, creating a spinning, contracting disk of material in which nuclear fusion begins. (8.1)
• Formation of the solar system • Solar system components
• Stars have life cycles during which they form and then evolve in one of three main ways. (8.1)
• Earth-Moon-Sun interactions
• The solar system refers to the eight planets, their moons, and all the other celestial objects that orbit the Sun. (8.2) • The solar system formed from the leftover gas, dust, and other debris spinning around the newly formed star, our Sun. (8.2) • Interactions between Earth, the Moon, and the Sun result in astronomical phenomena such as the auroras, solar and lunar eclipses, the phases of the Moon, and comets, as well as creating tides in the world’s oceans. (8.3)
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Space exploration improves our knowledge and gives us beneficial technologies,
• Early human views of the universe • Benefits of space exploration
• Early cultures and civilizations used their observations of celestial objects to develop calendars, plan hunting and farming activities, navigate across oceans and land, and inspire spiritual beliefs. (9.1)
• Canadian contributions to space exploration
• Space research, technology, and exploration advances our knowledge of the universe while producing many spinoffs that benefit people’s daily lives. (9.2)
• Costs and hazards of space exploration
• Canadian organizations and individuals make significant contributions to space technology, research, and exploration. (9.2) • Space research and exploration is very costly, travel into space involves a high degree of risk, and there are many ethical, political, and environmental issues associated with continued investment in space study. (9.3)
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VOCABULARY
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KEY VISUALS
about 13.7 billion years ago. • asteroid belt (p. 262)
• galaxy (p. 254)
• astronomer (p. 258)
• light-year (p. 261)
• astronomical unit (p. 261)
• nebula (p. 264)
• astronomy (p. 258)
• nuclear fusion (p. 261)
• Big Bang theory (p. 280)
• solar system (p. 260)
• binary system (p. 263)
• spectral lines (p. 282)
• black hole (p. 270)
• spectral shifting (p. 282)
• celestial objects (p. 258)
• spectroscope (p. 281)
• dark matter (p. 271)
• spectrum (p. 278)
• electromagnetic radiation (p. 281)
• star (p. 261)
• electromagnetic spectrum (p. 281)
• universe (p. 255)
• supernova (p. 263)
The Hubble Ultra Deep Field
systems in the universe formed. • asterisms (p. 294)
• photosphere (p. 309)
• astronomical phenomenon (p. 294)
• planet (p. 313)
• aurora borealis (p. 312)
• protostar (p. 296)
• chromosphere (p. 309)
• revolution (p. 325)
• comet (p. 318)
• rotation (p. 324)
• constellation (p. 294)
• solar eclipse (p. 327)
• corona (p. 309)
• solar flare (p. 311)
• coronal mass ejection (p. 311)
• solar wind (p. 312)
• lunar eclipse (p. 328)
• sunspot (p. 310)
• prominence (p. 311)
• meteor (p. 318)
Part of the Eagle Nebula
but its costs and hazards are significant. • artificial satellite (p. 356)
• retrograde motion (p. 342)
• equinox (p. 341)
• summer solstice (p. 340)
• geostationary (p. 356)
• spinoff (p. 354)
• microgravity (p. 367)
• winter solstice (p. 340)
• orbital radius (p. 343)
The Canada-Hawaii-France telescope
UNIT C
Task
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Mission to Mars: Humans or Robots? Getting Started Over the last few decades, we have learned much about Mars from data collected by ground-based and spacebased telescopes, satellites, and robotic probes landed on the planet’s surface. While a human mission to Mars has not yet been tried, NASA’s Constellation program is working to do just that. It hopes to send a piloted mission to the planet by 2030. As you have read in this unit, Mars is a long way from Earth. It is even a long way from the Moon, which has often been considered as the place to set up a base of operations for flights farther afield. A one-way journey to Mars from Earth or the Moon is expected to take about eight months. Add six months for on-the-ground exploration and another eight months to return home, and the total time Mars astronauts would be away is nearly two years. The technological problems in achieving such a mission would also be enormous. Nevertheless, aiming to set humans down on Mars seems like the next logical step in the progress of space exploration. Many people involved in space research argue that to really understand the nature of Mars, we need to see it for ourselves. They also point to all the technological advances we have already made in space research. Those in support of sending astronauts to Mars believe we will continue finding solutions to the many challenges of human space travel, including that of reaching a destination as far away as Mars.
Criteria for Success • Your group must include in its report references to at least eight different sources that collectively you consulted in doing your research. • Your final report must clearly present the pros and cons of each option (humans vs. robotic probes) for a Mars mission, followed by your group’s final conclusion about which option is the more reasonable and why. • As a group, you must demonstrate that you worked cooperatively in researching the topic and reaching consensus on your final conclusion.
Your Goal You will be researching the pros and cons of sending humans or robotic space probes to explore Mars. Your goal is to develop your own conclusion about the type of exploration you would support and justify that conclusion based on your research.
What You Need to Know Information about the nature of Mars and the challenges of reaching it is provided in several sections in this unit. See Skills Reference 4 for guidance in researching topics.
What You Need • ScienceSource Access to the Internet, library, and other sources of information. Consult with your teacher. • As a starting point, use the following questions to help guide and focus your research into the pros and cons of each option — that is, sending humans or robotic probes to Mars. • How effective would each option likely be in terms of data-gathering? • How does the cost of each option compare? • What safety concerns are posed by each option?
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• How does each option compare in terms of the ethical, political, economic, and environmental issues it raises?
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Procedure 1. Working in a small group, decide how you will approach the research assignment. You may opt to have each person in the group do research on all the aspects of the issue. Alternatively, you may opt to assign each individual a different aspect to research. 2. Individually, do your research using at least eight different sources. Make notes about what you found, and remember to record the details of each source you used. 3. Gather as a group, and discuss your findings. Explain to each other the preliminary conclusion you have formed based on your research. Listen to each other’s viewpoints and the research evidence. Attempt as a group to reach consensus about your conclusion as to which option is the more reasonable one for future explorations of Mars: continuing to use robotic systems or working to send humans there. Reaching consensus may be a difficult task. Be prepared to sort out differences in a fair and respectful way.
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constructive comment. Make sure the report’s overall conclusion is clearly stated and that all the findings presented in the report clearly support that conclusion. 5. Make a short presentation before the class, stating your conclusion and summarizing the key reasons for that conclusion.
Assessing Your Work 6. In a class discussion, share your thoughts on the following. (a) How did your research influence your opinions on each question? (b) How effective was the group decision-making process? How were disagreements resolved? (c) Did any of the other groups reach a different conclusion from the one your group did? If so, did hearing their arguments in support of their conclusion influence you to change your thinking? Explain your answer.
4. Write a group report. First, develop a report outline that all members of the group agree on. Then, have each person in the group pick a section of the report to write. Read each other’s sections, and offer
Weighing the pros and cons of sending humans rather than robots to Mars requires asking difficult questions, including those of an ethical and economic nature. Space exploration improves our knowledge and gives us beneficial technologies, but its hazards and costs are significant.
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ACHIEVEMENT CHART CATEGORIES k Knowledge and understanding t Thinking and investigation c Communication a Application
Key Terms Review
9. Where are stars “born”?
1. Create a concept map to organize all the terms in the list below. c • artificial satellite • astronomical unit • Big Bang theory • celestial objects • galaxy • light-year • nebula • nuclear fusion • planet • protostar
• revolution • rotation • solar system • solstice (summer, winter) • spectral shifting • spinoff • star • supernova
Scientific evidence suggests that the universe began expanding from a single point about 13.7 billion years ago.
2. Why does a star shine?
k
3. Explain what an astronomical unit is. 4. Explain what a light-year is.
k
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5. List four different types of galaxies, and sketch the general shape of each one. c
10. Sketch the three main stages in a star’s formation. c 11. Explain what has to happen inside a highmass star to cause it to turn into a supernova. k 12. What property is a neutron star noted for? k
13. The Hertzsprung-Russell diagram plots stars according to what three stellar properties? k
15. Why is the temperature of sunspots lower than that of the rest of the photosphere? 16. What causes the aurora borealis?
18. (a) Name the astronomical phenomenon shown in the image below. k (b) Explain what causes it to happen.
7. What is thought to make up more than 90 percent of the mass of the universe? k 8. Give two pieces of evidence that support the Big Bang theory of the formation of the universe. t UNIT C
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k
17. Describe the theory of how the solar system formed. k
6. Sketch the Milky Way galaxy as viewed from the side. Label the distance across the galaxy at its widest point and the distance through the galactic bulge. Give both distances in light-years. c
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14. Name two ways that the Sun’s energy interacts with Earth’s atmosphere. k
Key Concept Review
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The solar system formed 5 billion years ago, in the same way other star-andplanet systems in the universe formed.
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Question 18
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19. Explain why the Sun always appears to rise in the east and set in the west. k
27. What is the shape of the planets’ orbits in the solar system? k
20. Is it the rotation or the revolution of Earth that is part of the cause of the seasons? Explain. k
28. Explain the main way that a refracting telescope differs from a reflecting telescope. k
21. In a sketch, show how Earth, the Moon, and the Sun are aligned during:
29. What kind of optical telescope is the Hubble Space Telescope? k
(a) a full moon (b) a new moon
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30. Name the four main types of spacecraft currently in use. k
c
Space exploration improves our knowledge and gives us beneficial technologies, but its costs and hazards are significant.
22. Give three reasons that early people had for studying space. k 23. Explain the significance of the following in terms of hours of day and night. k
31. Describe how the Global Positioning System works. k 32. (a) What is the gravitational condition shown in the image below? k (b) Define that condition.
k
(c) Describe four ways that this gravitational condition affects the human body. k
(a) summer solstice (b) winter solstice (c) equinox 24. Define retrograde motion.
k
25. Does Mars or Saturn have the greater orbital radius than the other? Explain your answer. k 26. The telescope used by the 17th century astronomer Galileo had little more power of magnification than many binoculars do today. Still, what was Galileo able to observe for the first time that had not been clearly observed Question 26 before? k
Question 34
33. What physical hazards put a spacecraft at risk? k
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(continued)
Connect Your Understanding 34. Describe what we would see from Earth if the Sun were part of a binary star system. t 35. The image below shows galaxy NGC 4256. It has a supernova occurring inside it, not quite visible in the image here. Astronomers calculate that this exploding star lies 55 million ly from Earth. Even though the image was taken in 1994, how many years ago did the star actually explode? t
39. Describe the life cycle of: (a) a low mass star
k
(b) a medium mass star
k
40. What kind of technologies on Earth can a coronal mass ejection affect? t 41. Explain the role played by the solar wind in the formation of the solar system. k 42. If all of the asteroid belt’s material were combined, it could make a planet about the size of rocky Mercury. However, there is one main reason that such a development will never occur. With reference to the diagram below, suggest what that reason is. t asteroid belt
Earth
Sun
Mars
Jupiter
Question 35 Question 42
36. Explain why astronomers think that the farthest galaxies we can see may also be the oldest in the universe. t 37. Write out your full address in the universe, starting from the street name and ending with the Local Supercluster. a
43. Although Jupiter is a gas planet, the pressure at its centre is not enough to start nuclear reactions. Explain what might have been different about Jupiter had it been a little larger and the pressure in its core greater. t
38. Describe the relationship between luminosity and temperature for each of the following types of stars. Consult the Hertzsprung-Russell diagram in Figure 8.11 on page 301 for guidance. t
44. The light we see from the planets in the solar system is only light reflected from the Sun. If so, then why do the planets appear so much brighter than most of the stars we can see in the night sky? t
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45. Why is the length of a year on Earth not the same length as a year on all the planets in the solar system? t
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46. Name three astronomical phenomena observable from Earth for which early peoples would not have understood the scientific cause. k 47. The largest refracting telescope ever built and still in use has a large glass lens almost exactly 1 m in diameter (see image below). Suggest why larger refracting telescopes have not been built. t
49. Explain why the following statement is not correct: Until humans invented the telescope about 500 years ago, they had no tools or other means of studying celestial motion or celestial objects. t 50. (a) Optical telescopes collect visible light. What does a radio telescope detect and collect? k (b) What piece of evidence in support of the Big Bang theory did radio telescopes detect? k 51. Suppose you are a pilot flying a commercial aircraft. What useful information would you be able to obtain from your onboard GPS device? a 52. This image shows a firefighter wearing a fire-resistant suit and compact breathing apparatus, both spinoffs from space research. Explain why these technologies were originally developed. t
Question 47. Yerkes Observatory, Wisconsin, U.S.A.
48. List the following terms in the order they occur during a year, starting from January.
k
(a) autumnal equinox (b) summer solstice (c) winter solstice (d) vernal equinox
Question 52
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(continued)
53. Many countries now have their own space agency and are sending astronauts into space. One example is China, as shown in the image below. As more countries look to space and its resources as a new frontier, what issues arise? t
55. Use the Hertzsprung-Russell diagram in Figure 8.11 on page 301 to answer the following questions. a (a) What colour is each of the following stars? (i) Rigel (ii) the Sun (iii) Aldebaran (b) How many times brighter than the Sun is Betelgeuse? (c) What is the surface temperature of Procyon A? (d) Which stars have a higher surface temperature: yellow or red?
Question 53 Astronaut Zhai Zhigang making China’s first spacewalk. He was launched into space in 2008 on a Chinese-built rocket and spacecraft.
Skills Practice
(e) Red stars normally have low luminosity. Explain how a red star such as Betelgeuse can be one of the brightest stars in the sky. 56. How would you use the image below to help someone locate Polaris, the North Star? a
54. Write the following numbers in scientific notation. a (a) the distance from star A to star B: 90 000 000 000 000 km (b) the average distance from Earth to the Sun: 150 000 000 000 m (c) the distance from one side of galaxy A to the other: 24 800 000 ly
Question 56
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Revisit the Big Ideas and Fundamental Concepts 57. Describe how Edwin Hubble’s findings about the motion of galaxies helped support the Big Bang theory of the formation and evolution of the universe. k spectral lines
star is stationary
star is approaching
star is moving away
no shift
blue shift
red shift
Question 57
58. The solar system has an average-sized star, the Sun, around which eight planets and many other celestial objects orbit. How does the discovery of other star-and-planet systems in the universe help support the theory of how the solar system formed? t 59. Both the Sun and the Moon affect Earth. Identify which of the two has the greater influence on our planet, and provide the reasons that support your answer. t 60. Why is it important for society to consider and assess the range of benefits, costs, and hazards related to space research before making decisions to continue with space exploration? t
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Science, Technology, Society, and the Environment
61. Development of the Canadarm and Canadarm2 is one way that Canada has supported international efforts to explore and learn about space. Such undertakings require extensive co-operation and team work at the national level. The robotic Canadarm technology was developed by a private Canadian aerospace company, with the financial support of the federal government. Other partnerships in Canada between government, research institutes, universities, and industry continue to help advance space technologies, research, and exploration. (a) Why do you think it is advantageous for Canada to contribute space technologies to international projects rather than to pursue space exploration by itself? t (b) Can scientific knowledge and technologies related to the study of space develop and advance without the sharing of knowledge? t (c) Suggest an instance when not sharing scientific knowledge gained from research might be a better decision than sharing it. Explain your answer. t
Reflection 62. (a) Has your opinion about the value of space research and exploration changed since you began this unit? Explain your answer. c (b) This unit describes or refers to many different career areas in the field of space research and exploration. Have any of the areas you read about inspired you to find out more about what the work might involve? If so, ask your teacher for assistance in learning more Unit C
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Lightning flashes around transmission lines carrying electricity to communities. 388
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The Characteristics of Electricity
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Contents 10
Static charges collect on surfaces and remain there until given a path to escape. 10.1 Exploring the Nature of Static Electricity 10.2 The Transfer of Static Electric Charges
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10.3 Electrostatics in Our Lives
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Current electricity is the continuous flow of electrons in a closed circuit. 11.1 Current, Potential Difference, and Resistance 11.2 Series Circuits and Parallel Circuits 11.3 Ohm’s Law
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We can reduce our electrical energy consumption and use renewable energy resources to produce electrical energy. 12.1 Renewable and Non-Renewable Energy Resources for Generating Electricity 12.2 Reducing Our Electrical Energy Consumption
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Unit Task In your Unit Task, you will evaluate methods of local electricity generation that could be used as backup sources for the regional power grid. Your investigations into the characteristics of electricity, methods of conserving electrical energy, and methods of providing electrical energy will help prepare you for your task.
Essential Question How can we use local resources to generate electricity in a dependable, environmentally friendly way?
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Exploring
Toronto was one of many cities that were without electricity during the 2003 blackout. Some places in Ontario now celebrate Blackout Day on August 14 to remind people of how important it is to conserve energy.
Blackout!
Electrical generating stations from Ohio to Ontario shut down, leaving 50 million people in the dark. Why?
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Imagine what it would be like to live in a world without electricity. Now, count to nine. In a mere nine seconds, that scenario came true. On August 14, 2003, at 4:11 in the afternoon, 50 million people in Ontario and the northeastern United States were plunged into the largest electrical blackout in North American history. Elevators stuck between floors, subways were in blackness, traffic lights stopped working, and television screens and computer monitors went dark. Electricity is often generated far from cities and is distributed along a network that includes electrical generating stations, transmission lines, and distribution stations. This huge, interconnected system of electricity networks is called the “energy grid.” Ontario, New York, Michigan, and other northeastern provinces and states are part of the eastern interconnection grid. Electricity cannot be stored for long after it is generated, so all parts of the grid must maintain a balance of supply and demand. If a transmission line or generator is overloaded, that part of the
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energy grid is disconnected automatically and the electricity is sent along alternative paths. One cause of problems in an energy grid is transmission lines that touch trees so that the electricity moves through the trees into the ground instead of along the wire.
Preventing Future Blackouts On August 14, a series of events, including human error, high demand, lines touching trees, automatic shutdowns, and failures of alarm systems, resulted in a huge surge of electricity in the grid. Within seconds, 256 electrical generating stations from Ohio to New York to Ontario shut down as a protective control. It took almost two full days to get all the generating stations back in operation and electricity restored to all the affected areas. This blackout raised difficult questions that could only be solved by government and electrical industry experts from both Canada and the United States working together. How did the blackout happen? What can be done to prevent such a blackout from occurring again? These are very complex questions to investigate. By working cooperatively, groups from the two countries successfully figured out the answers to these questions. Now, because of their hard work, the electrical grid is safer and better able to deal with a similar situation. Smaller, local blackouts do occur from time to time. But the knowledge learned from the mistakes of previous large blackouts helps reduce the chances of such a large-scale blackout happening again.
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A transmission line is automatically disconnected from the grid when it touches treetops or other objects.
STSE Science, Technology, Society, and the Environment
Electricity Concept Map Electrical energy is often in the news. You have probably read or viewed reports about the costs and benefits of producing energy from renewable and non-renewable sources. You might be practising some ways to reduce electrical energy consumption and achieve electrical savings in your home. And you can probably describe the importance of electricity to your daily life.
Now is your opportunity to get a sense of how your pieces of knowledge about electricity fit together.
1. As a class, create a concept map about electricity. Start with the word “electricity” in the centre of a large piece of chart paper. 2. Add categories, terms, concepts, and sketches to the map, making links between the parts that are connected.
Exploring
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Static charges collect on surfaces and remain there until given a path to escape.
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Skills You Will Use In this chapter, you will: Sparks flash from the centre of a plasma ball to the point of contact where a hand touches the ball.
• investigate the transfer of static electric charges by friction, contact, and induction • predict the ability of different materials to hold or transfer electric charges • plan and carry out inquiries to determine and compare the conductivity of various materials • apply knowledge and understanding of the safe operation of electrical equipment
Concepts You Will Learn In this chapter, you will: • learn about the differences between electrical insulators and conductors • explain how materials allow static charges to build up or to discharge • analyze the design of technological devices that improve electrical efficiency or protect other devices by using or controlling static electricity
Why It Is Important Static electricity is part of our daily lives. By understanding how charges build up and discharge, we can avoid problems caused by sparks and make use of static electricity to improve our lives.
Before Reading Determining Importance Preview the subheadings and illustrations in Chapter 10. Which topics and illustrations are familiar? Which topics and illustrations are unfamiliar based on your background knowledge and experience? The unfamiliar topics and illustrations represent the information that is most important for you to learn. Create a list of learning goals for this chapter based on the information that represents new learning for you.
Key Terms • conduction • conductor • electrical discharge • electron • electron affinity • friction • induction • insulator • static electricity
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Exploring the Nature of Static Electricity
Here is a summary of what you will learn in this section: • Solid materials are charged by the transfer of electrons. • When an atom gains electrons, it becomes negatively charged. • When an atom loses electrons, it becomes positively charged. • Electrons can be removed from objects through friction. • Particles with unlike charges attract each other, and particles with like charges repel each other. • Electrical insulators and conductors are materials categorized by how freely they allow electrons to move.
Figure 10.1 Electric charges cause strands of hair to repel each other and be attracted to the balloon.
A Shocking Experience On a cold winter day, you have probably pulled a sweater off over your head or removed your hat and felt your hair flying up. Or maybe you have reached to touch a doorknob or the door handle of a car and received an electric shock. These examples and hairraising experiences like the one in Figure 10.1 are caused by electric charges. Electric charges are charged particles that exert an electric force on each other. These charged particles are very small. In fact, there are millions of them on each standing hair in the picture above. The accumulation or gathering of even larger numbers of electric charges can lead to some impressive electrical displays. Think back to the last time you observed a lightning storm. The large, bright flashes of lightning look like the small electric sparks you may have seen when touching the doorknob or taking off your sweater. In fact, they are the same thing, just different in size. These are all examples of static electricity.
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D2 Quick Lab Characteristics of Electric Charge A characteristic is a distinguishing trait or quality of a substance or object.
Purpose To observe the characteristics of electric charge
Materials & Equipment • confetti or gelatin powder • plastic drinking straw
4. Turn one balloon so that its rubbed surface faces away from the other balloon. Again bring the balloons together. Record your observations for steps 3 and 4. 5. If your classroom has a Van de Graaff generator, your teacher will demonstrate the following experiments by putting the materials for each experiment in place and then turning on the generator. Record your observations for each experiment. (a) Tape one end of the thin paper strips to the Van de Graaff generator.
• 2 balloons • Van de Graaff generator
(b) Place a stack of three aluminum pie plates on the Van de Graaff generator.
• thin paper strips • clear adhesive tape
(c) Place a clear plastic cup full of polystyrene “popcorn” on the Van de Graaff generator. Put a loose-fitting lid on top of the cup.
• 3 aluminum pie plates • clear plastic cup with lid
(d) Attach a metal rod to a lab stand, and place it close to the Van de Graaff generator.
• polystyrene “popcorn” • metal rod and lab stand
6. Return everything you used to the areas designated by your teacher.
Procedure 1. Read through the procedure steps, and make predictions about what you think will happen in each step. Record your predictions. 2. Sprinkle some confetti or gelatin powder in a small area on your desk. Push a plastic drinking straw through your hair several times, and bring it close to the confetti or gelatin powder. Record your observations. 3. Inflate two balloons, and knot the ends. Rub one side of each balloon on your hair or clothing. Hold the balloons by the knots, and bring the rubbed surfaces slowly together. Observe the results.
Questions 7. (a) Which objects were attracted to each other? (b) Which objects were repelled or pushed away from each other? 8. How did your observations compare with your predictions for each step? 9. What do you think caused the movements that you observed?
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Electrically Charged Particles You may recall from earlier studies that an element is a pure substance that cannot be broken down into simpler substances. An element is made up of tiny particles called atoms. An atom is the smallest part of an element with the element’s properties. Within an atom, there are three types of smaller particles: protons, neutrons, and electrons. Protons and electrons are electrically charged particles. Protons have a positive electric charge (+), and electrons have a negative electric charge (–). Neutrons have no electric charge, so they are neutral. The protons and neutrons are in the nucleus at the centre of the atom. The electrons are outside the nucleus (Figure 10.2). Although they contain electrically charged particles, atoms are neutral. The number of protons in the nucleus equals the number of electrons around the nucleus, so the number of positive and negative charges is equal. This makes an atom neutral. neutron
proton
nucleus
electron
Figure 10.2 Each atom is made up of protons and neutrons inside the nucleus and electrons in the area around the nucleus.
Static Charges W O R D S M AT T E R
“Static” is from the Greek word statikos, meaning causing to stand. The word “stationary,” which means not moving, is based on the same Greek word.
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Objects can become charged when electrons move from one object to another. The electric charge that builds up on the surface of the object is called a static charge or static electricity. The charges are “static” because they remain very nearly fixed in one location on the surface of the object until they are given a path to escape. An object that has more electrons than protons is negatively charged. An object that has more protons than electrons is positively charged. You can group objects according to three kinds of charge: positive, negative, and neutral. If a neutral object obtains extra electrons, the object becomes negatively charged. If a neutral object loses electrons, the object becomes positively charged.
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Friction and the Movement of Electrons All solid materials are charged by the transfer of electrons. How do atoms lose or gain electrons to become electrically charged? One common cause of electron transfer is friction, which occurs when objects rub against each other. Friction is the force resisting the relative motion of two surfaces in contact. When two objects rub together, the force of friction can remove electrons from one object and cause them to transfer to the other object. As one object loses electrons, the other object gains them, as shown by the amber and fur in Figure 10.4. If you count the electrons in Figure 10.4, you will notice that no electrons are lost during the process of charging. They are simply transferred. The position of the positive charges does not change during the process of charging.
W O R D S M AT T E R
“Electricity” comes from the Greek word elektron, meaning amber, which is fossilized tree resin (Figure 10.3). Amber has been used for thousands of years to study static electricity.
Figure 10.3 Amber is fossilized tree resin. This piece of amber contains bugs that were living on the tree and got caught in the amber.
electrons
neutral
(a)
neutral
negative
(b)
positive
(c)
Figure 10.4 The amber and the fur are electrically neutral (a). If you rub the amber with the fur, electrons transfer from the fur to the amber (b). As a result, the fur becomes positively charged and the amber becomes negatively charged (c).
It’s important to remember that the transfer of the charges from one object to another is possible because the two objects are rubbing against each other. Both objects are neutral before they are rubbed together. They become charged as a result of the rubbing. For any charging procedure, it’s important to keep in mind that new electric charges are not being created. The electrons in each object are just being rearranged within the object or transferred to another object.
Static charges collect on surfaces and remain there until given a path to escape.
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Electron Affinity
Table 10.1 A Triboelectric Series Tend to lose
Suggested Activity • D3 Inquiry Activity on page 402
(+)
Different substances have different electrons human hands (dry) abilities to hold on to electrons. glass The tendency of a substance to human hair hold on to the electrons is called electron affinity. nylon Table 10.1 lists a series of cat fur selected materials in order of silk their electron affinity. You will cotton notice that the higher the material steel is in the list, the greater the wood tendency for that material to lose electrons. amber This means that if you rub ebonite together two materials listed in plastic wrap Tend to the table, you can determine Teflon® gain which material will be positively electrons (–) charged and which material will be negatively charged. For example, if you rub nylon and steel together, the nylon will become positive and the steel will become negative. The nylon will lose electrons, because it is higher in the table. The electrons from the nylon are transferred to the steel, making the steel negative. This table is referred to as a “triboelectric” series. The term comes from tribos, a Greek word meaning to rub. Note that there can be a slightly different order for materials such as fur or wood depending on which type of animal the fur is from and which type of tree the wood is from.
Learning Checkpoint 1. Where are electrons in the atom? 2. What does “static” mean in “static electricity”? 3. What happens when two objects made out of different materials are rubbed together? 4. What term describes an atom’s tendency to hold on to electrons? 5. In each of the following pairs, state which one is more likely to give up electrons. (a) wood or human hair (b) plastic wrap or steel (c) cotton or silk 398
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Laws of Attraction and Repulsion
During Reading
You may have heard the expression “opposites attract” in discussions about people. This is definitely true for electric charges (Figure 10.5). Scientists studying the interaction of objects have observed that when a positively charged object is brought close to a negatively charged object, the two objects attract each other. When two objects with the same charge are placed close together, the objects repel each other.
Visualizing and Picture Mapping
Opposite charges attract.
Like charges repel.
Good readers use the strategy of visualizing to understand the important details of a large amount of complex information. One way to visualize is to create a picture map. Using the information about the laws of attraction and repulsion, begin drawing pictures to represent the information provided in this section. Add to your picture map as you read about electrical insulators and conductors.
Figure 10.5 If you increase the amount of charge on objects, the attraction or repulsion also increases.
As a result of many scientific investigations, scientists have established the following laws of static electric charges. • The law of attraction states that particles with opposite charges attract each other. • The law of repulsion states that particles with like charges repel each other.
Coulombs Charles-Augustin de Coulomb was a French physicist who worked with electric charges and made several important discoveries (Figure 10.6). He showed that when two charged objects are placed closer together, the attraction or repulsion increases. When the charged objects are moved farther apart, the attraction or repulsion decreases. In his honour, the metric unit for electric charge is named the coulomb (C). One coulomb equals 6.24 × 1018 electrons added to or removed from a neutral object.
Figure 10.6 Charles-Augustin de Coulomb (1736–1806)
Static charges collect on surfaces and remain there until given a path to escape.
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Electrical Insulators and Conductors Another way to group materials is by their conductivity. Conductivity is the ability of materials to allow electrons to move freely in them. Materials that hold onto their electrons and do not allow them to move easily are called electrical insulators. An electrical insulator is a solid, liquid, or gas that resists or blocks the movement of electrons, as shown in Figure 10.7. Dry wood, glass, and plastic are all examples of electrical insulators. An insulator can hold a static charge because static charges remain nearly fixed in place.
- + ++ + +- - +
+
+- -+ + + + - +-
(a) Insulator: The electrons (–) are bound tightly to the nuclei (+) so they resist movement.
-
+ + +
+
-
+
+ +
+
- + - +
(b) Conductor: The electrons are not as tightly bound to the nuclei. They can move away from the nuclei.
Figure 10.7 Electrons in an insulator cannot move freely. Electrons in a conductor can.
Materials that allow electrons to change positions are called conductors (Figure 10.8). Conduction is the movement or transmission of electrons through a substance. Examples of conductors include the metals copper and aluminum. Some materials allow only some movement of electrons. This is the category of materials called fair conductors. In a fair conductor, the electrons do not move as freely as in a conductor, but they are not held almost in place as they are in an insulator.
Figure 10.8 The metal wire in the electric fence allows electrons to move. The plastic insulator resists the movement of electrons.
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Table 10.2 gives some examples of conductors, fair conductors, and insulators. There are variations within each category, as some materials are better or poorer conductors than others. Table 10.2 Conductivity of Selected Materials Conductors
Fair Conductors
Insulators
copper
water with dissolved minerals
rubber
aluminum
moist air
wood
iron
human body
plastic
mercury
carbon
pure water
other metals
soil
metal oxides, such as rust
Water as a Conductor Notice in Table 10.2 that water is an insulator only if it is pure. However, most water has dissolved minerals in it, so its conductive properties change and it becomes a fair conductor. This is why you do not want to be in a lake during a thunderstorm. If lightning hits the water, the electric charges from the lightning will spread out through the water and cause you serious or fatal injury. This is also why you should not use water to try to put out an electrical fire (Figure 10.9). You also need to take care not to operate electrical appliances near water or with wet hands.
Learning Checkpoint
Figure 10.9 Use an all-purpose fire extinguisher for an electrical fire.
Take It Further
1. (a) What does the law of attraction state? (b) What does the law of repulsion state? 2. What is a coulomb? 3. Define “electrical insulator.” 4. What does “conduction” mean?
A Faraday cage is an enclosure made of conducting material that protects its contents from electric charges. Find out how airplanes, cars, and even some specially designed clothes can act as Faraday cages. Start your research at ScienceSource.
5. (a) Name two examples of good conductors. (b) Name two examples of fair conductors. (c) Name two examples of insulators.
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DI Key Activity
SKILLS YOU WILL USE
D3
Inquiry Activity
Skills Reference 2
Adapting or extending procedures Drawing conclusions
Investigating Static Electricity Question What is the effect of charged objects on each other and on neutral objects?
Materials & Equipment • 2 vinyl strips
• beaker
• clear adhesive tape
• watch glass
• ring stand
• wooden ruler or metre stick
• paper towel
4. Bring one of the charged vinyl strips close to the suspended acetate strip. Make sure the two strips do not touch each other. Record your observations. 5. Place the beaker upside down on the desk or table. Place the watch glass on top of the beaker as shown in Figure 10.10. Balance the ruler so it is lying flat and centred on the watch glass. Bring a charged vinyl strip near, but not touching, one end of the ruler. Record your observations.
• 2 acetate strips
Procedure 1. Copy the following table into your notebook to record your findings. Give your table a title. Hanging Object
Approaching Object
charged vinyl
charged vinyl
charged acetate
charged acetate
charged acetate
charged vinyl
ruler
charged vinyl
ruler
charged acetate
Predictions
Observations Figure 10.10 Balance the ruler on the watch glass on top of the beaker.
6. Bring a charged acetate strip near one end of the ruler. Record your observations.
Analyzing and Interpreting 7. Usually, charged vinyl is negative and charged acetate is positive. How does this information explain your observations?
Skill Practice 2. Tape one end of a vinyl strip to the ring stand so the strip hangs down. Rub the hanging vinyl strip with the paper towel to charge it. Then, rub the other vinyl strip with the paper towel, and bring that vinyl strip close to the suspended strip. Record your observations in your table. 3. Repeat step 2, using the two acetate strips and the paper towel. Record your observations.
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8. Describe how you would modify the procedure in this activity so that you could identify the type of charge on a charged object.
Forming Conclusions 9. Write three statements that summarize your observations.
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10.1 CHECK and REFLECT Key Concept Review 1. (a) Draw a diagram of an atom that has four protons, five neutrons, and four electrons. (b) Label each particle with its name and whether it is positive (+), negative (–), or neutral.
11. Copy this chart into your notebook. For each pair, predict which substance becomes more positively charged and which becomes more negatively charged when the two substances are rubbed together. Use Table 10.1, A Triboelectric Series on page 398, to help you make predictions. Charged Pairs
2. (a) What is friction? (b) Explain how friction can be used to transfer electrons. Use two substances from the triboelectric series in Table 10.1 on page 398 in your answer.
Pairs
cotton, silk human hair, human hands (dry)
4. State the two laws of static electric charges.
Teflon®, wood
5. Where are static charges held?
glass, plastic wrap
7. (a) What is the difference between a conductor and an insulator? (b) What is an example of a conductor? (c) What is an example of an insulator? 8. (a) What is the difference between a conductor and a fair conductor? (b) What is an example of a fair conductor? 9. Why can you not use water to put out an electrical fire?
Becomes More Negatively Charged
cotton, steel
3. Explain why this statement is false: “A neutral object contains no charge.”
6. Why might a plastic rod that contains a large number of electrons not have a static charge?
Becomes More Positively Charged
12. Make a list of five different ways in which you experience static electricity in your own life. 13. (a) While fishing in an aluminum boat in the middle of a lake, you notice storm clouds forming nearby. Why is it a good idea to get to shore as fast as possible? (b) Would your answer change if the lake somehow became filled with distilled water with no ions present in it? Explain why or why not.
Reflection Connect Your Understanding 10. Do two identical objects become statically charged when you rub them together? Explain why they do or do not.
14. What are two questions about static electricity that you would like to explore further? For more questions, go to ScienceSource.
Static charges collect on surfaces and remain there until given a path to escape.
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The Transfer of Static Electric Charges
Here is a summary of what you will learn in this section: • Electroscopes are instruments that detect static charge. • In charging by contact, an orginally neutral substance gains the same charge as the charged object that touched it. • In charging by induction, an originally neutral substance gains the opposite charge to the charged object. • Neutral objects are attracted to charged objects. • Grounding an object transfers electrons between the object and the ground, making the object neutral. • An electrical discharge occurs when charges are transferred quickly.
Figure 10.11 The bits of paper are attracted to the statically charged comb.
Charged Objects What does dust on a computer screen have in common with paper on a comb (Figure 10.11)? In both examples, there is attraction between objects with unlike charges. You may have noticed a similar effect when you unpack a box containing polystyrene packing foam and the little pieces of foam stick to your skin and clothes. Polystyrene is very low on the triboelectric series and becomes charged very easily. How do you know when an object is charged? Rather than testing whether the object sticks to something else, you can use an electroscope, which is an instrument that can detect static charge. The electroscope was first invented in 1748 by a French clergyman and physicist named Jean Nollet. A metal-leaf electroscope has two very thin metal pieces, called leaves, suspended from a metal rod (Figure 10.12 on the next page). The metal rod is attached to a top plate or metal knob. When a charge is transferred to the plate or knob, the charges spread out over the whole structure, including the leaves. The greater the charge, the greater the separation between the leaves. An electroscope is one of the devices that can be used to study static electricity. The study of static electric charges is called electrostatics.
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D4 Quick Lab Using an Electroscope Purpose To determine what happens to an electroscope when different charged objects are brought near it
4. Charge the glass, acrylic, or acetate rod by rubbing it with the silk fabric. Repeat steps 2 and 3 using this charged rod. Part 2 — Pith-Ball Electroscope
Materials & Equipment • plastic comb or straw or ebonite rod • metal-leaf and/or pith-ball electroscope
5. Charge the comb or straw by running it through your hair, or rub an ebonite rod on a wool sweater.
• glass, acrylic, or acetate rod
6. Bring the charged object near the pith ball but do not touch it (Figure 10.13). Record your observations.
• wool sweater • silk fabric
7. This time, touch the pith ball with the charged object. Then, touch it again. Record your observations.
Procedure Part 1 — Metal-Leaf Electroscope 1. Charge the comb or straw by running it through your hair, or rub an ebonite rod on a wool sweater. 2. Bring the charged object near, but not touching, the top of the electroscope (Figure 10.12). Observe the motion of the metal leaves. Then, move the object away and observe the leaves again. Record your observations. 3. This time, touch the charged object to the top of the electroscope. You can rub the object along the top of the electroscope if necessary. Observe the motion of the metal leaves. Then, move the object away and observe the leaves again. Record your observations.
Figure 10.12 Metal-leaf electroscope
8. Charge the glass, acrylic, or acetate rod by rubbing it with the silk fabric. Repeat steps 6 and 7 using this charged rod.
Questions 9. What role did friction play in this activity? 10. With your group, explain what happened in Part 1, using your knowledge about charges. Assume your object had a negative charge placed on it. 11. With your group, explain what happened in Part 2, using your knowledge about charges. Assume your object had a negative charge placed on it.
Figure 10.13 Pith-ball electroscope
Static charges collect on surfaces and remain there until given a path to escape.
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Detecting Static Charge In order to predict what charge is transferred to an electroscope, you can use a standard set of charged objects, such as ebonite and glass. Ebonite is a hard rubber material that is low on the triboelectric series and readily accepts electrons. When ebonite is rubbed with fur, it becomes negative (Figure 10.14). Glass is high on the triboelectric series and tends to give away electrons. When glass is rubbed with silk or plastic, it becomes positive, as shown in Figure 10.14.
Figure 10.14 To test unknown charges, you can use the known charges on an ebonite rod (a) and a glass rod (b).
Suggested Activity • D5 Quick Lab on page 412
When a negatively charged rod is brought near a neutral electroscope, the electrons in the electroscope are repelled by the rod. The electrons move down into the leaves of the electroscope. The leaves are now both negatively charged, so they repel each other and move apart (Figure 10.15). When the negatively charged rod is taken away, the negative charges in the electroscope are no longer repelled, so they move throughout the leaves, stem, and knob. The leaves drop down, and the electroscope is neutral again.
–++–+ –
–+ +– –+ –+ –+
++ +
–+
+ –
–+ –+ –+ –+
+ –+ –+ –+ – – (a)
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+ – – + –+ – + –+ – – (b)
Figure 10.15 The leaves are not separated in the neutral electroscope (a). The leaves repel each other when they are charged negatively or positively (b).
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Charging by Contact
During Reading
As you learned in section 10.1, electrons can be transferred through friction. Electrons can also be transferred through contact and conduction. You can charge a neutral object by contact when you touch it with a charged object. Charging by contact occurs when electrons transfer from the charged object to the neutral object that it touches. The neutral object gains the same type of charge as the object that touched it because the electrons move from one object to the other (Figure 10.16).
+++
–+ – –+ –
––+––+–+–
–+ – –+ – –+ –
+ +– –+ + +
(a) Figure 10.16 (a) When a negatively charged object touches a neutral object, electrons move to the neutral object, making it negative.
Understanding Terms and Concepts A Frayer quadrant can help you understand a term or the concept it represents. Divide a rectangle into four sections, and put the term or concept as the rectangle’s title above it (e.g., Charging by Contact). In the top left section, write a definition of the term using your own words and words from the text. In the top right section, write facts related to the term. In the lower left section, write examples of the term from the textbook. In the lower right section, write non-examples of the term.
(b) (b) When a positively charged object touches a neutral object, electrons move from the neutral object to the positive object and make the neutral object positive.
Suggested Activities • • D6 Inquiry Activity on page 413 • D7 Inquiry Activity on page 414
Induction Induction is the movement of electrons within a substance caused by a nearby charged object, without direct contact between the substance and the object. If you rub a rubber balloon on your hair, electrons will transfer from your hair to the balloon, making the balloon negative. The charges stay in a nearly fixed, or static, position on the balloon because rubber is an insulator. When you bring the negatively charged balloon near a neutral wall, the negatively charged electrons on the balloon repel the negative charges on the wall, making that part of the wall a positive surface. The balloon is said to induce a charge on the wall because it charges the wall without contacting it (Figure 10.17).
– + – + – – + – + – + – –
– + – + – + – – + – + – –
+ –
+ + + +
+ – –
+ –
– – + –
– –
+ – –
–
+
Figure 10.17 The negatively charged balloon has induced a positive charge on the wall’s surface without touching the wall.
Static charges collect on surfaces and remain there until given a path to escape.
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Charging by Induction When you charge an object by induction, you use a charged object to induce a charge in a neutral object and then ground the charged object so it retains the charge. This newly charged object has the opposite charge to the charge on the charging object. Grounding is the process of connecting a charged object to Earth’s surface. When you connect a charged object to the ground, you provide a path for charges to travel to or from the ground. Figures 10.18 and 10.19 show the process of charging by induction. Grounding occurs in diagram (b). electrons
+++
+++ –
+
+ + – – + – + + – –
+ – – + – –
+ – – + – –
Figure 10.18 (a) When a negatively charged object comes near a neutral electroscope, it repels the electrons in the neutral electroscope.
–
–
– – –
–
– ++ –+
+ –
+ + –
+
(b) When you ground the neutral electroscope, you provide its electrons with a path away from the repulsive influence. Some electrons leave the electroscope.
+
(c) When you remove the ground and the charged object, the electroscope is left with a positive charge because it has lost some electrons.
electrons
– – –+–+–+
–++–+ –
–
–
– – –
– – + + – –––+
– – – – + + + +
+
Figure 10.19 (a) When a positively charged object comes near a neutral electroscope, it attracts electrons in the neutral electroscope.
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– – + – + – –
– + – + – + –
(b) When you ground the neutral electroscope, you provide a path for electrons to go toward the positive influence.
– – – + – – + + – – –+ + – –
(c) When you remove the ground and the charged object, the electroscope is left with a negative charge because extra electrons are trapped on it.
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Learning Checkpoint 1. What does an electroscope detect? 2. In the contact method of charging, what charge does a neutral substance gain compared to the object that touched it? 3. In induction, what charge does a neutral substance gain compared to the object brought near it? 4. What is the difference between charging by contact and charging by induction in terms of electron transfer? 5. What is grounding?
Electrical Discharge Once an object is charged, the charges are trapped on it until they are given a path to escape. When electric charges are transferred very quickly, the process is called an electrical discharge. Sparks are an example of electrical discharge (Figure 10.20). Have you walked across a carpet and reached for a doorknob only to be shocked when you created a spark (Figure 10.21)? When you shuffle your feet in slippers or socks on a carpet, electrons are transferred through friction and you build up a static charge. When your hand reaches toward the neutral doorknob, the excess electrons transfer due to induction.
Figure 10.20 When a spark occurs, the air becomes a passage for the electrons to travel. Collisions between moving electrons and air particles release light and can also make a crackling sound.
Transfer of charge from girl to door
9G10.42
Transfer of charge from carpet to girl
Figure 10.21 When electrons jump between your hand and a doorknob, you can receive a surprising shock. Static charges collect on surfaces and remain there until given a path to escape.
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Lightning Lightning is an example of a very large electrical discharge caused by induction. In a thunderstorm, a charged area, usually negative, builds at the base of the cloud (Figure 10.22 (a)). The negative charge at the base of the cloud creates a temporary positive area on the ground through the induction process (Figure 10.22 (b)). When enough charge has built up, a path of charged particles forms (Figure 10.22 (c)). The cloud then discharges its excess electrons along the temporary path to the ground, creating a huge spark — lightning (Figure 10.22 (d)). This discharge creates a rapid expansion of the air around it, causing the sound of thunder.
electrons
(a)
(b)
(c)
electrons
(d)
Figure 10.22 Lightning is an atmospheric discharge of electricity.
It is interesting to note that air is normally an insulator. If it were not, lightning would occur every time that clouds formed. For lighting to occur, charges in the clouds must build up to the point where the air cannot keep the charges separated from the ground. At this point, the air stops being an insulator and becomes a fair conductor, resulting in a lightning strike. Earth is a donator or receiver of charge and is so large that overall it is not affected by the electron transfer of huge lightning strikes. As a result, the ground is always considered neutral.
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Electrostatic Generators
Take It Further
Scientists use several devices in the laboratory to study how static charges create lightning and other phenomena, such as the static that affects clothes coming out of the dryer. Early electrostatic generators were called “friction machines” because they used direct contact between different surfaces to create charged areas. A glass sphere or cylinder was rubbed mechanically by a pad to charge it up. More recent machines, such as the Van de Graaff generator, create charge through friction between the roller and belt and then transfer the charge to a large metal sphere, as shown in Figure 10.23.
Sometimes, lightning strikes start from the ground and go to a cloud. There are also cloud-tocloud lightning strikes. Find out more about different types of lightning. Create a visual display of your findings. Use ScienceSource as a starting point.
charge collector
metal sphere
Teflon™ roller
rubber belt
insulating support nylon roller motor-driven pulley
Figure 10.23 (b) The static charge on a Van de Graaff generator has a hair-raising effect on these students.
comb
Figure 10.23 (a) This Van de Graaff generator is set up so its dome is negatively charged. A Van de Graaff generator can also be charged positively by using different roller materials.
A Wimshurst machine creates charges on two slowly rotating disks with metal strips placed around the disks (Figure 10.24). The charge is built up using induction between the front and back plates as the disks turn in opposite directions. The excess charge is collected by metal combs with points near the turning disks.
Figure 10.24 The Wimshurst machine uses induction to build up charge and create sparks.
Static charges collect on surfaces and remain there until given a path to escape.
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D5 Quick Lab Charge Sorter Materials that tend to lose electrons are higher on a triboelectric series. Materials that tend to gain electrons are lower on a triboelectric series.
Purpose
4. Use a charged ebonite rod to test the charge on the electroscope by bringing it near the knob. Do not touch the rod to the electroscope (Figure 10.25). Observe the motion of the leaves. 5. Record the charge of material A.
To sort materials based on their ability to hold on to static charge
Materials & Equipment • materials such as fur, silk, aluminum, paper towel, leather, wood, amber, hard rubber, Styrofoam®, plastic wrap, vinyl (PVC) and Teflon® • metal-leaf electroscope • known charged object, such as an ebonite rod rubbed on fur to create a negative charge
6. Ground the electroscope by touching it with your hand. Then, charge the electroscope using material B. 7. Use a charged ebonite rod to test the charge on the electroscope by bringing it near the knob. Do not touch the rod to the electroscope. Observe the motion of the leaves. 8. Record the charge of material B. 9. Repeat steps 3–8 for each pair of materials.
CAUTION: Some people are allergic to fur.
Questions 10. Which materials were good electron receivers and would appear lower on a triboelectric series?
Procedure 1. Make a table like the one below to list your materials, predictions, and results. Give your chart a title. Record your predictions. Materials
Prediction of Charge
A
B
A
1.
fur
silk
2.
fur
aluminum
3.
silk
aluminum
4.
silk
paper
B
Actual Charge A
11. Which materials were good electron donors and would appear higher on a triboelectric series? 12. Create a triboelectric series by listing the materials you used in order, according to their electron affinity.
B
2. Record your predictions for what charge each material in each pair will have when the materials are rubbed together. 3. Rub together the first pair of materials, A and B. Then, touch material A to the knob of the electroscope to charge the electroscope. Figure 10.25 To test the charge on the electroscope, bring the charged ebonite rod near it. Do not touch it.
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Inquiry Activity
Skills Reference 2
Making predictions Observing, and recording observations
Charging by Contact Question What charge does the electroscope gain compared to the charging rod?
5. Charge the glass rod by rubbing it with silk. Bring the glass rod near, but not touching, the top of the electroscope. Record your observations using a labelled diagram.
Materials & Equipment • ebonite rod
• glass rod
• fur
• silk
6. Touch the top of the electroscope with your hand.
Trial B
• metal-leaf electroscope
7. Repeat steps 2–4 using a glass rod charged with silk. Use a charged ebonite rod in steps 5. Repeat step 6.
CAUTION: Some people are allergic to fur.
Procedure 1. Make a table like the following to record your predictions and observations. Give your table a title. Record your predictions. Motion of Leaves Trial Trial A
Predictions
Observations
8. Return all materials to the areas designated by your teacher.
Analyzing and Interpreting 9. (a) Explain why the leaves moved when the ebonite rod touched the electroscope in step 3. (b) What charge was left on the electroscope? 10. (a) Explain why the leaves moved when the glass rod touched the electroscope in step 5.
ebonite rod touching ebonite rod near
(b) What charge was left on the electroscope? 11. How do your predictions compare with your observations?
glass rod near Trial B
4. Rub the ebonite rod with the fur again. Bring it near, but not touching, the top of the electroscope. Record your observations using a labelled diagram.
12. In terms of charge movement, explain in words and diagrams the effect of:
glass rod touching
(a) an identically charged rod near the electroscope
glass rod near
(b) an oppositely charged rod near the electroscope
ebonite rod near
Skill Practice 13. Explain how you would find the charge of an unknown material.
Trial A 2. Charge the ebonite rod by rubbing it with the fur.
Forming Conclusions
3. Brush the ebonite rod against the top of the electroscope. Record your observations of the electroscope leaves using a labelled diagram.
14. Write a summary statement about the charge the electroscope gains and the charge of the influencing rod.
Static charges collect on surfaces and remain there until given a path to escape.
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Inquiry Activity
Skills Reference 2
Charging by Induction Question What charge does the electroscope get compared to the charging rod?
Gathering, organizing, and recording relevant data from inquiries Interpreting data/information to identify patterns or relationships
4. Remove your hand from the electroscope, and then move the ebonite rod away. Observe what happens to the leaves of the electroscope. Record your observations. 5. Bring a charged ebonite rod near the electroscope. Record what happens to the electroscope leaves.
Materials & Equipment
6. Bring a charged glass rod near the electroscope. Record what happens to the electroscope leaves.
• ebonite rod
• fur
• glass rod
• metal-leaf electroscope
• silk
7. Repeat steps 2–5 except start by charging a glass rod against silk in step 2. Use a charged ebonite rod for step 6.
CAUTION: Some people are allergic to fur.
Procedure
Analyzing and Interpreting
1. Make a table like the following. Give your table a title. Record your predictions. Motion of Leaves Trial Trial A
Predictions ebonite rod away
glass rod near glass rod away glass rod near ebonite rod near
Trial A 2. Charge the ebonite rod by rubbing it against the fur. 3. Bring the ebonite rod near the electroscope. Be careful not to touch the rod to the electroscope. While you hold the rod there, touch the top of the electroscope with your hand.
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8. (a) Compared to the original rod that was brought near the electroscope, what charge did the electroscope end up with? (b) How do you know?
Observations
ebonite rod near
Trial B
Trial B
9. Explain what happens to the electrons in the electroscope when your hand touches the electroscope. 10. (a) Why did you have to remove your hand first before you moved the rod away? (b) What would have happened if you had moved the rod away and then your hand?
Skill Practice 11. How else could you ground the electroscope?
Forming Conclusions 12. Summarize the method of charging by induction by using diagrams labelled with the motions of charges.
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10.2 CHECK and REFLECT Key Concept Review 1. How are lightning and a spark similar? 2. (a) How do objects become negatively charged using the contact method? (b) How do objects become positively charged using the contact method? 3. Explain how a substance becomes temporarily charged by induction when a charged object is brought near.
8. (a) Why do the leaves of the charged electroscope shown below move farther apart if a rod with the same charge is brought near? (b) Why would the leaves move closer together if the rod had the opposite charge to the electroscope? +
+
+
4. Explain how to charge an object permanently using induction. 5. Using a sequence of labelled diagrams, explain how a positive balloon will stick to a neutral wall. Under each diagram, describe the motion of the charges.
+ +
+ +
Connect Your Understanding Question 8
6. (a) How does the process of grounding occur when you receive a spark from touching a metal shopping cart? (b) How does the process of grounding occur during a lightning strike? 7. What would change about the way an electroscope worked if its metal knob were replaced with a plastic knob? metal knob
9. A person walks across a carpet, touches a metal doorknob, and receives a shock. If the same person were carrying a metal rod, she would not experience a shock when touching the doorknob. Why? 10. Suppose a five-year-old child asks you to explain why there is lightning. Write a simple explanation that you could share with the child. You may wish to include a diagram.
Reflection 11. What are two things about static electricity that you know now but you did not know before you started this chapter?
Question 7
For more questions, go to ScienceSource.
Static charges collect on surfaces and remain there until given a path to escape.
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Electrostatics in Our Lives
Here is a summary of what you will learn in this section: • Lightning rods are used to prevent damage to buildings. • Grounding static charges can help prevent sparks near flammable fuels. • Paint sprayers work better if the object and the paint have different charges. • Photocopiers use electrostatic principles in their operation. • Grounding wires prevent damage to electrical equipment. • Electrostatic precipitators work by creating charged waste particles and using electrostatic attraction to remove the particles.
Figure 10.26 Lightning can strike tall buildings repeatedly during a storm. The CN Tower (extreme right of photograph) is struck by lightning more than 70 times a year.
Lightning Storm Awareness On a hot and humid summer night, lightning strikes a building in Toronto (Figure 10.26). Along with the lightning, there would have been loud claps of thunder. You may have noticed that as a storm moves closer, the time between lightning and thunder decreases. This occurs because lightning travels very fast, at the speed of light. Thunder travels much more slowly, at the speed of sound. If you see lightning and hear thunder at the same time, the storm is right above you. Summer storms are common in Ontario and across Canada, but many people do not know what to do in these extreme weather conditions. Lightning storm safety begins by watching for towering cloud formations that signal developing storms. Lightning can strike up to 15 km from where it is raining. As a guideline, if you can hear thunder, you are in striking distance and should look for shelter. Safe shelter includes a large building because it will be properly grounded if there is a strike. Cars, school buses, and other vehicles are also safe places, provided that the windows are rolled up and you do not touch metal parts of the vehicle. 416
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If no safe shelters are available, you should avoid the highest point of land because lightning tends to hit these areas. Remain in a safe place for about 30 minutes after the last thunderclap. A dangerous place to take shelter during a lightning storm is under a tree, as the tree may be the highest point in the area. This makes it more likely to be struck by lightning. Also stay away from objects that conduct electricity, such as bicycles, lawnmowers, and golf clubs. Summertime presents a higher risk of being struck by lightning both because there are more lightning storms and because more people are outdoors participating in activities such as baseball, swimming, fishing, and boating. Lightning strikes cause about six deaths per year in Canada and result in injuries to about 60 people. All of these could be prevented if everyone follows the few careful steps just described as the storm approaches.
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STSE Quick Lab
Lightning: Facts and Fiction Purpose
Questions
To separate lightning facts from lightning fiction
Procedure 1. As a class, read the following true account of one man’s close encounter with a lightning strike. Then, discuss the questions that follow. A man was digging post holes in a large open field. One of the tools he was using was a 2 m steel bar, which he used to pry rocks from the ground. He was working in stormy weather and wanted to finish a bit more work before taking cover. Suddenly, he could feel the hairs on his arms and legs begin to stand up. He threw the steel bar as hard as he could and dove for the ground. Then, he heard a deafening blast of sound. The lightning strike missed him, and he ran for cover. Later, after the storm, he went back to the site. The ground around the bar was blackened, and one end of the bar appeared to have melted.
2. What was his hair standing up an indication of? 3. (a) Holding a steel bar when the lightning struck would almost certainly be lethal. Why? (b) Would it make any difference if the steel bar being held had one end in the ground when lightning struck? Explain why or why not. 4. Describe the path the lightning may have taken to result in blackened ground and a melted end of the steel bar. 5. What could the man have done differently in order to be safer during the storm? 6. Describe how to keep safe if you find yourself outside during a thunderstorm. 7. If you find yourself out in the open during a thunderstorm, you should crouch, keep your feet close together, and stay on your toes. (a) Why should you crouch on your toes? (b) Why should you keep your feet close together?
Static charges collect on surfaces and remain there until given a path to escape.
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Lightning Rods
Figure 10.27 A tree burned by lightning
When lightning strikes a tree, the sap inside the tree conducts the electricity down to the ground. In the process, the tree heats up and expands very rapidly, resulting in an explosion and fire (Figure 10.27). If the tree had been wet on the outside and dry on the inside, the electricity might have followed a different path to the ground and left the tree unharmed. Or if there had been a conductor, such as a metal rod, that was slightly taller than the tree and that was connected to the ground, the lightning strike could have followed the conductor safely to the ground and left the tree unharmed. A lightning rod is a metal pole with a wire attached to it that runs down to the ground. The main purpose of a lightning rod is to provide a point removed from the main structure of a building where a stream of electrically charged particles is more likely to form. The stream of electrically charged particles is highly conductive, so if lightning strikes in the area around the building, it is much more likely to strike the lightning rod (Figure 10.28). This decreases the total amount of electric charge in the building, which makes it less likely to be struck by lightning. If lightning hits the lightning rod, the flow of electrically charged particles is directed harmlessly down to the ground so the building is not damaged, as shown in Figure 10.29.
lightning rod
Figure 10.28 The point on top of this weather vane is a lightning rod.
Figure 10.29 The lightning rod redirects the electrical strike away from the barn and harmlessly into the ground.
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insulated grounding wire
ground rod
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Grounding Static Charges on Vehicles
During Reading
Friction occurs when two surfaces rub against each other. The surfaces may be solids, such as silk or glass, or they may be fluids, such as air or water. Automobiles and airplanes build up charge through friction between the vehicle’s outer surface and the air. A simple way to prevent static build-up on a car is to use a ground strap (Figure 10.30). However, dragging a strap along the ground would not be a practical solution for airplanes. Airplanes have needle-like projections located in various places on the wings and plane body, as shown in Figure 10.31. The force of repulsion between charges becomes so strong around a point that charges will disperse into the air from the point.
Determining the Key Idea
Figure 10.30 Some drivers use a grounding strap to prevent static charges from building up on their cars.
Good readers synthesize details from a text to determine the key idea. To do this, you make connections among the important ideas in the text, asking yourself the question “How does this information connect to that information?” As you read pages 418 to 420, ask yourself how the information on one page connects to the information on another page. What is the single key idea presented on these pages?
Figure 10.31 These needle-like rods on the wing of an airplane disperse static charges into the air.
Static Charges and Flammable Materials Static charge build-up is particularly dangerous when using flammable materials (Figure 10.32). When airplanes are fuelled, the very explosive fuel moving through the nozzle creates a build-up of static charges. If the nozzle comes too close to the plane’s body, a spark could ignite the fuel. In order to prevent this from occurring, the nozzle and fuel truck are connected to the ground. Sparks are also dangerous near the gas pumps at service stations. It is a good idea to ground yourself at a service station by touching a metal door handle before you slide across the seat to exit a vehicle.
Figure 10.32 The nozzle and fuel truck must be grounded before refuelling an airplane begins.
Static charges collect on surfaces and remain there until given a path to escape.
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Reducing Static Charges in the Home
Figure 10.33 You can reduce the build-up of static charges by drying only the same types of materials at one time.
You can use your knowledge of static charges to help you understand how to reduce charges. For example, static charges are built up when different types of insulators, such as nylon and polyester, rub together. This is why clothes made of different materials often stick together when they come out of a clothes dryer (Figure 10.33). More charges build up in dry air, such as during winter, because dry air acts as an insulator. Moist air is a fair conductor, so fewer charges build up on humid days. If you remove clothes from the dryer before they are completely dry, there will be fewer charges on them. Sometimes, people add an antistatic dryer sheet to a clothes dryer. The dryer sheet adds a thin layer of waxy chemicals to the surface of clothes so there is less friction between the surfaces and therefore fewer unlike charges to attract each other. Sparks caused by static charges can damage sensitive electronic equipment. People who work with this type of equipment take special care to reduce the risk of sparks. For example, carpets can cause static build-up. Ways to reduce the risk of static sparks from carpets include: • using an antistatic mat for your feet • increasing the moisture in the air by using a humidifier • spraying the carpet with antistatic spray • wearing an antistatic wrist strap (Figure 10.34) • removing the carpet from the computer room Figure 10.34 This computer technician wears an antistatic wrist strap to reduce the build-up of charges.
Learning Checkpoint 1. What is the function of a lightning rod? 2. How is charge build-up reduced on airplanes? 3. Why is a ground strap a necessary safety feature when transferring fuel? 4. What are three different methods for reducing charge build-up in clothes dryers? 5. What are four different methods for reducing charge build-up in a computer room with a carpet?
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Making Use of Static Charges Static electricity can be a nuisance when it causes flyaway hair or sparks in your living room. It can be extremely dangerous when it occurs near flammable materials or electronic equipment. However, static electricity can also be useful. Our ability to control and direct static electricity has allowed us to design technological devices that make use of it to improve our lives.
Spray Painting If you have ever tried spray painting, you may have found it to be a challenging job. The paint comes out in a mist, and you lose a lot of paint because it doesn’t all land on the object you’re trying to paint. The paint comes out of the spray gun at a high speed, so the paint particles bounce off the object being painted, wasting paint. Electrostatics can help! Figure 10.35 shows a worker making use of electrostatics to paint a car. The paint coming out of the nozzle gains a negative charge through friction. The surface of the car has been given a positive charge. Unlike charges attract, so the paint is attracted to the surface of the car. There is less waste due to bounce and overspray, and the finish is smooth and uniform.
Figure 10.35 Industrial sprayers such as those used to paint cars and boats take advantage of the laws of static charges. Static charges collect on surfaces and remain there until given a path to escape.
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Take It Further Laser printers make use of electrostatics in the printing process. Find out how a laser printer works. Start your research at ScienceSource.
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Photocopying The word “photocopy” means to copy using light. Figure 10.36 shows the typical steps involved in photocopying, including the role of electrostatics.
Step 1 A positive charge is created on the drum. The drum is an insulator, but it becomes a conductor when exposed to light. For this reason, it is called a photoconductor.
⫹ ⫹ ⫹ ⫹⫹ ⫹ ⫹⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫹⫹ ⫹ ⫹⫹ ⫹ ⫹⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫹
Suggested Activity • D10 Quick Lab on page 424
Step 3 Plastic particles and toner (ink) are sprayed onto the drum. As the particles come out of the sprayer, they get charged negatively. The negatively charged toner sticks to the positively charged areas on the drum, creating a copy of the original paper.
⫺
⫹
Step 2 The image on the paper to be photocopied is projected onto the drum. Where the light hits the drum, the area becomes conductive, loses its charge, and becomes neutral. The dark areas remain positively charged.
⫺ ⫺
⫺
⫹ ⫹
⫹
⫺
⫹
⫺
⫹
Step 4 A sheet of paper is pressed against the drum and heated. Heat and pressure cause the toner to fuse to the paper. In some photocopiers, the paper is also charged to help the toner stick to it.
page to be copied light source
lens
⫹⫹ ⫹⫹⫹ ⫹ ⫹⫹ ⫹ ⫹ ⫹ ⫹ ⫹⫹ ⫹ ⫹⫹ ⫹⫹ ⫹⫹⫹ ⫹
Figure 10.36 A model of a photocopying process
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Step 5 The paper is still charged and may be warm when it comes out of the photocopier.
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Environmental Applications An electrostatic precipitator makes use of the laws of static charges to clean air (Figure 10.37). The gas discharged from a factory can contain tiny particles of pollutants, called particulate matter. One way to clean the gas before it is released is to send it through pipes that charge the particulate matter negatively. The gas then moves through an area that has positively charged plates. The positive plates attract the negative particles and remove them from the gas. These collector plates are cleaned periodically to keep the system running efficiently. Industrial plants that produce cement, steel, lumber, and petrochemicals use similar techniques to remove dust from the air. We also use electrostatics in processes that purify and sort materials, such as ore separation in mining, plastics and paper recycling, and the settlement of fine particles suspended in water.
Suggested Activity • D11 Quick Lab on page 425
clean gas out Electrostatic Precipitator
conductors (metal plates) polluted gas in
grounding wire
solid waste collection
D9
Figure 10.37 An electrostatic precipitator uses static electricity to remove particulates from gases in buildings or industrial sites.
STSE Science, Technology, Society, and the Environment
Advertisements for Static Control Products If you have a problem with flyaway hair, clothes sticking together in the dryer, or dust that will not stick to a mop, chances are there is a consumer product that has been designed to help you. Discuss the following questions with your group and record your answers. 1. Give examples of products that help consumers with static control.
2. Are these products essential for everyday living? Why or why not? 3. (a) What do advertisers say about static in their messages to try to convince you to buy their products? Is this information accurate? (b) Do you think they are successful in convincing people? Explain your answer.
Static charges collect on surfaces and remain there until given a path to escape.
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D10 Quick Lab Make Your Own Photocopier Imagine painting your name on a piece of paper using a paint that attracts electrons. Suppose you then rubbed the paper with fur, causing your painted name to gain a negative charge. You could sprinkle cocoa or flour on the paper and the neutral cocoa or flour would be attracted to the charged paint. The cocoa or flour would stick to your name, spelling it out in black or white. This is basically how a photocopier works. In this activity, you will investigate a variation of this technique.
3. Add cocoa or flour to the dish. Jiggle the dish in order to spread the cocoa or flour evenly. 4. Using a minimum of tape, attach the edge of the circle to the outside of the lid. 5. Using the wool cloth, gently rub the lid area showing through the paper for about a minute, as shown in Figure 10.38.
Purpose To investigate the principles of photocopying
Materials & Equipment • paper and scissors
• clear adhesive tape
• plastic petri dish and lid
• cocoa or flour • wool cloth
CAUTION: Never eat anything in science class.
Figure 10.38 Rub the lid gently.
6. Carefully remove the stencil. Put the lid on the dish. 7. Turn the dish upside down while holding the lid. Then, turn it right side up. 8. Remove the lid. Record your observations.
Procedure 1. Cut a paper circle the size of the petri dish. 2. Turn the paper into a stencil by cutting out a simple symbol such as a diamond or your initial.
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Questions 9. What did you observe in step 8? 10. How would you explain your observations?
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D11 Quick Lab Make Your Own Precipitator An electrostatic precipitator uses static charges to separate particles in order to purify and sort materials.
Purpose To study how an electrostatic precipitator works
Materials & Equipment • paper towels Figure 10.39 Pull the paper towel across the table slowly.
• ground pepper • flour • salt
4. Clean the balloons and recharge them. Repeat step 3 with the remaining particles on the towel.
• lint • 3 balloons
5. Clean up your work area. Wash your hands thoroughly. CAUTION: Never eat anything in science class.
Questions Procedure
6. (a) Which particles were the easiest to pick up?
1. Lay a long piece of paper towel on a table. Sprinkle pepper, flour, salt, and bits of lint on the paper towel. 2. Inflate and tie off three balloons. Charge the balloons by rubbing them against your hair or a sweater. Hold the balloons above the table but not directly above or touching the paper towel. 3. Have a partner pull the paper towel across the table slowly under the balloons (Figure 10.39). Observe which materials are taken up and how much of the material is left.
(b) Which particles were difficult to pick up? Explain why. 7. What happened to the ability of the balloons to pick up particles as time went on? 8. Why do you think this method is used to remove particulate matter from the air? 9. What factors would affect the efficiency of a precipitator?
Static charges collect on surfaces and remain there until given a path to escape.
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10.3 CHECK and REFLECT Key Concept Review 1. Why is it not a good idea to take shelter under a tree in a thunderstorm? 2. (a) What are the three parts of a lightning protection system for a building? (b) What is the function of each part? 3. What causes the static build-up on moving vehicles such as cars and airplanes? 4. Large trucks that carry flammable liquids often have a metal wire or chain that drags on the ground. Why? 5. Sometimes, finished photocopied paper will stick to you. Explain why. 6. Name four applications that use electrostatic principles.
Connect Your Understanding 7. Why does Earth not become charged when many people in the world ground objects? 8. How can neutral pollutant particles be made attractive to the charged plate in an electrostatic precipitator? 9. The technician in this photo is using a tool that has insulated handles. Why is this important for working on electronic equipment?
10. When spray paint is applied to a car, the paint has a negative charge and the surface of the car has a positive charge. Some processes use a negatively charged paint and a grounded object. Explain why this also works. 11. Flowing fluids, such as water, oil, and air, produce static charge. Why is it not as important to create static charge safety rules for handling flowing water as for handling air or oil? 12. Suppose you have a static charge problem at home. Your clothes stick to your body, there are socks stuck to your sweater from the dryer, and you always get a shock from touching a doorknob after walking across your carpet. Suggest ways you can reduce or eliminate these and similar problems. 13. Explain the importance of protecting computer equipment from static discharge. 14. Explain how eliminating static electricity would hinder the performance of a spray painting device. 15. Suppose a building had a lightning rod that was not connected to a ground rod by a conducting wire. Would this set up still provide protection from lightning strikes? Explain.
Reflection 16. Which device that makes use of static electricity has the greatest effect on your life? Why?
For more questions, go to ScienceSource.
Question 9
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S C I E N Ceverywhere E
Deep Brain Stimulation This device is sometimes called a “pacemaker for the brain.” A pacemaker is an implanted device that supplies electric signals to the heart to help it beat regularly. A brain pacemaker causes deep brain stimulation. It stimulates the brain by sending electric impulses to target areas deep within the brain. These electric impulses interfere with naturally occurring electric impulses in the brain that cause uncontrolled shaking, called tremors, in a patient. Tremors are a symptom of several conditions, including Parkinson’s disease. Tremors can prevent people from walking, feeding themselves, or even just being able to sit still.
Before receiving the deep brain-stimulating device, this patient was unable to control his arms and was unable to speak clearly. With his new implants sending electric signals to his brain, he is able to use his steady hand to enjoy a hot cup of coffee without worrying about spilling it and burning himself.
This X-ray shows how deeply the two electrodes are placed inside the brain. The electric signals are generated by a small device implanted in the patient’s chest, near the shoulder. The electric circuits are programmed using a computer that contacts the device using radio signals. This means the electric impulses can be adjusted with the device implanted in the patient’s body. Using special magnets, patients or their doctor can even turn the deep brain stimulator on or off. 427
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10 CHAPTER REVIEW ACHIEVEMENT CHART CATEGORIES t Thinking and investigaion k Knowledge and understanding c Communication
a Application
5. (a) Describe how to leave an object positively charged using the induction method. k
Key Concept Review 1. (a) What are the possible interactions between two charged objects? k (b) How do a charged object and a neutral object interact? k
(b) Describe how to leave an object negatively charged using the induction method. k 6. How would you ground an electroscope? 7. (a) Define electrical discharge.
(b) What is a real-life example of an electrical discharge? k
2. Explain the role of friction in creating a charged object. k 3. (a) Two neutral objects, A and B, were rubbed together, resulting in object A being charged positively. What is now the charge on B? k (b) How do you know?
k
(c) Which object, A or B, is likely higher on the triboelectric series? k (d) How do you know?
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9. Describe a device that protects other devices by controlling static electric charges. Include a labelled diagram as part of your answer. c
Connect Your Understanding 10. Explain why a positively charged balloon will stick to a wall just as easily as a negatively charged balloon. t 11. Would the humidity (moisture content) of the air make a difference in the photocopying process? Explain. t
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12. Suppose you had a plastic lightning rod that was the same size and design as a metal lightning rod. Would the plastic lightning rod work better than, the same as, or not as well as a metal lightning rod? Explain your answer. t 13. Would a negatively charged balloon stick to a metal wall as easily as to a wooden wall? Explain why it would or would not. t 14. You have an unknown material that becomes charged when you rub it with silk. You also have a negative ebonite rod and a positive glass rod. How can you determine the charge of the unknown object? t
21. What materials could be woven into a polyester carpet to prevent a static charge from building up on a person walking across the carpet? Explain the reasons for your choice. a
Reflection 22. What information from this chapter surprised you or was not what you expected? Explain why. c 23. (a) How would you rate your participation in the labs you did in this chapter? c (b) How could you improve your participation? c
15. If lightning hits a car, the effect is minimal. Explain why. a 16. Two identical objects are both charged positively, but one object has about twice as much positive charge as the other object. What would happen to the charges when the two objects are brought together? Explain your answer. t 17. (a) How would using a humidifier in a home affect static charge build-up?
a
(b) Would you need to use a humidifier more in the summer or the winter? Explain. a 18. Explain two different actions that could cause static charges to build up on a computer. a 19. If you wrap plastic wrap on a glass bowl, the plastic wrap will cling to the bowl. Use your understanding of static charge to explain why. a 20. You run a brush through your hair and wonder if it has become statically charged. Design a test that allows you to determine if the brush has a charge. t
After Reading Reflect and Evaluate Revisit the key learning goals that you set in the Before Reading activity at the start of this chapter. How did the During Reading strategies help you to accomplish your goals? Write a paragraph that summarizes how the reading strategies assisted your learning. Compare your paragraph with a partner’s. Add any new insights you gained from reading your partner’s reflection.
Unit Task Link Storing large amounts of electricity is very difficult. This means that electricity is usually generated as it is being used. Generating facilities increase and decrease the amount of electricity they produce depending on how much electricity the community is using at any given time. Explain how an electrical grid connecting many different electrical generating sources and several communities provides a dependable source of electricity. Brainstorm a list of different ways of generating electricity. Sort them from most important to least important. Share your ideas with your class.
Static charges collect on surfaces and remain there until given a path to escape.
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Current electricity is the continuous flow of electrons in a closed circuit.
The Characteristics of Electricity
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Skills You Will Use Millions of light bulbs light up the Toronto skyline. Each light bulb is lit because of the movement of electrons through the wires that connect the bulbs.
In this chapter, you will: • design, draw, and construct series circuits and parallel circuits • analyze the effects of adding an identical load in series and in parallel • investigate the relationships between potential difference, current, and resistance • solve simple problems using the formula V = IR
Concepts You Will Learn In this chapter, you will: • describe the relationship between potential difference, current, and resistance • explain what different meters measure and how they measure electrical quantities • identify and explain the parts of a simple circuit • explain the characteristics of electric current, potential difference, and resistance and how they differ in series and parallel circuits • explain how different factors change the resistance of an electric circuit
Why It Is Important Every electrical appliance or device that you use includes one or more electric circuits. Understanding how electrical energy is produced, transferred, and converted into other forms of energy will help you handle electrical devices safely.
Before Reading Learning Vocabulary in Context This chapter contains many new terms related to electricity. Skim and scan section 11.1 for the ways that vocabulary is supported. Where can you find definitions? How are unfamiliar terms highlighted in the text? What special features explain terms or words? Begin a personal list of unfamiliar terms, adding definitions as you find them in the chapter.
Key Terms • ammeter • amperes • battery • electric current • fuse • load • ohms • potential difference • resistance • switch • volt • voltmeter
Current electricity is the continuous flow of electrons in a closed circuit.
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Current, Potential Difference, and Resistance
Here is a summary of what you will learn in this section: • An electrochemical cell generates a potential difference by creating an imbalance of charges between its terminals. • Potential difference is the difference in electric charge between two points that will cause current to flow in a closed circuit. • Current is the rate of movement of electrons through a conductor. • An electric circuit is a path along which electrons flow. • Resistance is the ability of a material to resist the flow of electrons. • Resistance in a wire depends on wire length, material, temperature, and crosssectional area. Figure 11.1 The elephantnose fish has tiny electric sensors in its nose that help it find
food.
Electric Fish, Eels, and Rays
Figure 11.2 The electric eel uses electricity to defend itself and to stun its prey.
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You probably know that when it comes to electrical safety, it is very important to keep electrical devices away from water. For some animals, this safety concern about electricity is not a problem. In fact, they survive because they can use electricity in the water. The elephantnose fish from central Africa has an extended nose that contains about 500 electric sensors (Figure 11.1) These sensors are used to help this tiny fish find food. The elephantnose fish hides for protection during the day and comes out to feed at night. The electric sensors help it find smaller living things crawling along the bottom of the river or swimming in the water. Research has shown that these electric sensors are so sensitive that they can detect chemical pollutants. Further research will determine if this type of sensor can be used to monitor the levels of pollutants in rivers.
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The electric eel in Figure 11.2 lives in the murky waterways of the Amazon and Orinoco river basins of South America. It’s really a fish and not an eel, but it really is electric — and dangerous. The eel’s electricity comes from a special organ in its long tail that contains thousands of muscle cells that work like tiny batteries. Each cell can produce only a small amount of electricity, but by working together all the cells can produce controlled bursts of electricity equal to five times the energy of a standard wall socket. These electrical bursts are used to stun prey when the electric eel is hunting for food. Some electric eels also generate an electric signal to attract a mate. The Pacific electric ray, found along the west coast of North America, has an electric organ located in its head (Figure 11.3). This organ can generate enough electricity to knock down a human. Other types of electric rays use these electric shocks for defense when they are attacked. Rays belong to a category of animals called Torpedo. The name for this category comes from the Latin word torpidus, which means numbness. This term describes what happens to a person who steps on an electric ray.
Figure 11.3 A Pacific electric ray can send out a powerful electric shock.
D12 Quick Lab Light the Lights In this activity, you will use a combination of wires, light bulbs, and an electrochemical cell to investigate how a steady, controlled flow of electrons can cause the bulbs to light up.
Procedure 1. Use wire and the dry cell to make one bulb light up. Record your arrangement. 2. Use wire and the dry cell to make two bulbs light up. Record your arrangement.
Purpose To discover how to make flashlight bulbs light up using a standard battery
3. If time allows, try other arrangements for step 1 and step 2.
Questions 4. Explain how to use wire and a dry cell to make one bulb light up. Include a labelled sketch in your answer.
Materials & Equipment • 1 D dry cell • 5 insulated copper wires with both ends bare
5. Explain how to use wire and a dry cell to make two bulbs light up. Include a labelled sketch in your answer.
• two 2.0 V-flashlight bulbs
CAUTION: Disconnect the wires if they get hot. Do not use dry cells if they show any sign of corrosion.
Current electricity is the continuous flow of electrons in a closed circuit.
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During Reading Illustrations Support Understanding of Vocabulary As you read the text, be aware of how the photos, diagrams, or other illustrations support your understanding of unfamiliar vocabulary. What term or concept is illustrated by the photo or diagram? How does the illustration make the concept easier to understand? If you get stuck on unfamiliar terminology, check the illustrations as one way to improve your understanding.
W O R D S M AT T E R
The word “circuit” comes from a Latin word meaning to go around. The word “circuit” can also be used to describe a complete journey of people or objects, such as the circuit of Earth around the Sun.
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Current Electricity The electricity of the electric eel and the electric ray is similar to the static charges you have felt from a sweater or the huge static charges of lightning. Unfortunately, static charges are not useful for operating electrical devices. They build up and discharge, but they do not flow continuously. To operate electrical devices, you need a steady flow of electrons. Unlike static electricity, a flow of electrons moves continuously as long as two conditions are met. First, the flow of electrons requires an energy source. Second, the electrons will not flow unless they have a complete path to flow through. This path is called an electrical c i rc u i t. The continuous flow of electrons in a circuit is called c u r re n t e l e c t r i c i t y.
Electric Circuits A circuit includes an energy source, a conductor, and a load. An electrical l o a d is a device that converts electrical energy to another form of energy. For example, in Figure 11.4, the light bulb is the load. It converts electrical energy to light and heat. Many electric circuits also include a switch. A s w i t c h is a device that turns the circuit on or off by closing or opening the circuit. When the switch is closed, the circuit is complete and electrons can flow. An open switch means there is a break in the path, so the electrons cannot flow through the circuit. The circuit is turned off when the switch is open.
energy source
+
electrical load
conducting wires
switch
Figure 11.4 An electric circuit
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Electrochemical Cells One simple and convenient energy source is a battery. A b a t t e r y is a combination of electrochemical cells. Each e l e c t ro c h e m i c a l c e l l is a package of chemicals that converts chemical energy into electrical energy that is stored in charged particles. A simple electrochemical cell includes an electrolyte and two electrodes. • An electrolyte is a liquid or paste that conducts electricity because it contains chemicals that form ions. An ion is an atom or a group of atoms that has become electrically charged by losing or gaining electrons. Citric acid is an example of an electrolyte. • Electrodes are metal strips that react with the electrolyte. Two different electrodes, such as zinc and copper, are used in a battery. As a result of the reaction between the electrolyte and electrodes, electrons collect on one of the electrodes, making it negatively charged. The other electrode has lost electrons, so it is positively charged (Figure 11.5). copper electrode (+)
zinc electrode (–)
F
D B
Figure 11.5 The citric acid in the grapefruit is the electrolyte. Electrons collect on the zinc
electrode, leaving positive charges on the copper electrode. The meter measures the flow of electrons.
C
A
E
Wet Cells and Dry Cells An electrochemical cell that has a liquid electrolyte is called a wet cell. Wet cells are often used as an energy source for cars and other motorized vehicles. An electrochemical cell that uses a paste instead of a liquid electrolyte is called a dry cell (Figure 11.6). You use dry cells in flashlights, hand-held video game devices, cameras, and watches. Each electrode in a dry cell or battery can also be called a terminal. Terminals are the end points in a cell or battery where we make a connection.
A – zinc powder and electrolyte, where electrons are released B – electron collecting rod C – separating fabric D – manganese dioxide and carbon, where electrons are absorbed E – negative terminal, where electrons leave F – positive terminal, where electrons return Figure 11.6 An alkaline dry cell
Current electricity is the continuous flow of electrons in a closed circuit.
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Recycling and Recharging Dry Cells Eventually, the chemicals in a dry cell are used up and can no longer separate charges. When you are finished using a dry cell, you should recycle it rather than discard it (Figure 11.7). Dry cells can contain toxic materials, such as the heavy metals nickel, cadmium, and lead. Household dry cells and batteries are responsible for over 50 percent of all the heavy metals found in landfills. Some dry cells are rechargeable cells. Chemical reactions in a rechargeable cell can be reversed by using an external energy source to run electricity back through the cell. The reversed flow of electrons restores the reactants that are used up when the cell produces electricity. Since rechargeable dry cells can be reused many times, they have less impact on the environment than non-rechargeable dry Figure 11.7 During recycling, the chemicals in a dry cell are separated and can be reused. cells.
Fuel Cells A fuel cell is an electrochemical cell that generates electricity directly from a chemical reaction with a fuel, such as hydrogen (Figure 11.8). The cell is not used up like an ordinary cell would be because as the electricity is produced, more fuel is added. Much of the energy produced by fuel cells is wasted as heat, but their design continues to be refined. Fuel cells are used in electric vehicles and may one day be used in smaller devices such as laptop computers.
Learning Checkpoint 1. How is current electricity different from static electricity? 2. What is an electric circuit? Figure 11.8 A fuel cell converts chemical energy into electrical energy. This fuel cell is slightly smaller than this textbook.
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3. List three components of an electric circuit. 4. What is the difference between an electrolyte and an electrode? 5. Why should dry cells be recycled rather than thrown in the trash?
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Potential Difference Each electron has electric potential energy. Potential energy is the energy stored in an object. Picture an apple hanging from a low branch on an apple tree (Figure 11.9). The apple has potential energy because of its position above the ground. If the apple falls down, it will convert its stored energy, or potential energy, into motion. Suppose an apple were on a higher branch. It would have even more potential energy to convert.
W O R D S M AT T E R
The electrochemical cell was first presented to the Royal Society of London in 1800 by the Italian physicist Alessandro Volta. The words “voltage and “volt” are named in his honour.
Figure 11.9 The greater the height of an apple above the ground, the greater its potential energy.
A battery has chemical potential energy in the electrolyte in its electrochemical cells. The chemicals in the electrolyte react with the electrodes. This causes a difference in the amount of electrons between the two terminals. One terminal in a battery has mainly negative charges (electrons). The other terminal has mainly positive charges (Figure 11.10). The negative charges are electrons, which can move. They are attracted to the positive charges at the positive terminal. If a conductor, such as a copper wire, is connected to both terminals, then the electrons flow from the negative terminal to the positive terminal. The difference in electric potential energy between two points in a circuit is called the potential difference or voltage (V). This difference causes current to flow in a closed circuit. The higher the potential difference in a circuit, the greater the potential energy of each electron.
–– + – + ––– – + ++ ++
Figure 11.10 An electrochemical cell or battery gives electrons electric potential energy.
Current electricity is the continuous flow of electrons in a closed circuit.
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Measuring Potential Difference The potential difference between two locations in a circuit is measured with a voltmeter. For example, you could place the connecting wires of the voltmeter across the positive and negative terminals of a battery like the rectangular yellow box shown in Figure 11.11. The voltmeter would then display the potential difference of the battery. The SI unit for measuring potential difference is the volt (V).
How Electrons Transfer Energy in a Circuit
Figure 11.11 The orange device is a voltmeter. It is showing a reading of 1.50 V. The yellow device is a battery.
When you turn on the light switch on a wall, you close the circuit and immediately the light comes on. How do the electrons get from the switch to the light bulb so fast? It may surprise you to learn that electrons do not travel from the switch to the bulb. You can picture electrons in a wire as being like water in a hose. If a hose connected to a tap already has water in it and you turn the tap on, water comes out of the end of the hose immediately. Electrons in a wire work in a similar way. When an energy source is connected to a circuit, electrons in the conductor “push” or repel other electrons nearby. As soon as one electron starts to move at one end of the wire, it pushes the next one, which pushes the next one and so on. By pushing the first electron, you make the last electron move (Figure 11.12). That is why when you flip the switch, the light goes on instantly even though the electrons themselves have not moved from the switch to the light bulb.
Figure 11.12 Electrons in a wire are like marbles in a tube. If you push a marble at one end of the tube, the energy is transmitted through all the marbles. When electrons in a wire are “pushed” from one end, energy is transmitted all along the electrons in the wire.
Learning Checkpoint 1. What is another name for stored energy? 2. How is an apple falling from a tree like the potential difference in a battery? 3. What does potential difference measure? 4. What is another name for potential difference? 5. When you walk into a dark room and turn the light on, do the electrons travel all the way from the switch to the light? Explain your answer.
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Current Electric current is a measure of the amount of electric charge that passes by a point in an electrical circuit each second. Think of the continuous flow of electric current as being like water flowing in a stream. The water keeps on flowing unless its source dries up. As long as the battery continues to separate charges on its terminals, the electrons continue to flow. Because the current flows in only one direction it is called direct current (DC). The flow of current from batteries is DC, but the current that flows through cords plugged into the wall sockets in your home is called alternating current. Alternating current (AC) flows back and forth at regular intervals called cycles. This is the current that comes from generators and is carried by the big power lines to your home.
Measuring Current
W O R D S M AT T E R
Current in a circuit is measured using an ammeter, as shown in Figure 11.13. The unit of electric current is the ampere (A). An ampere is a measure of the amount of charge moving past a point in the circuit every second.
“Ampere” and “ammeter” are named in honour of André-Marie Ampère (1775–1836), a French physicist who studied electricity and magnetism.
Figure 11.13 These ammeters show a reading of 0.50 A. The meter on the right has amperes on the scale below the black curved line.
Current Electricity and Static Electricity Current electricity is different from static electricity because current electricity is the flow of electrons in a circuit through a conductor. Static electricity is the electric charge that builds up on the surface of an object. Static electricity discharges when it is given a path, but it does not continue to flow. Current electricity is the continuous flow of electrons in a closed circuit.
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Electron Flow and Conventional Current Throughout this unit, we refer to current in terms of electrons flowing from a negative terminal to a positive terminal in a battery. However, when scientists studied electricity several hundred years ago, they did not yet know about electrons. They inferred that when electric current flowed from one object to another, it did so because one object had a greater amount of electricity, so the electricity flowed from the higher or more positive source to the lesser or more negative source. The mathematical equations and conventions developed afterward followed this assumption. This view is called conventional current, and it is a different way of describing the movement of electrons in a circuit (Figure 11.14).
(c) – (d)
(b)
+ (a)
Figure 11.14 Conventional current describes current as leaving the source from the positive
terminal (a) and entering the meter at its positive terminal (b). Then, the current is described as passing through the meter and leaving through the negative terminal (c). It then returns to the negative terminal of the source (d).
When you connect an ammeter or voltmeter to a circuit, you need to think in terms of conventional current rather than electron flow (Figure 11.15). There are two terminals on a meter that you use to connect to a circuit. The negative (–) terminal is often black, and the positive (+) terminal is often red. Always connect the positive terminal of the meter to the positive terminal of the electrical source. Connect the negative terminal of the meter to the negative terminal of the electrical source. Figure 11.15 When you connect an electrical meter, follow the rule “positive to positive, and negative to negative.” The positive red terminal of the meter is connected to the circuit. The positive red terminal of the battery is also connected to the circuit. The negative black terminals of the meter and the battery are connected directly.
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Resistance Resistance is the degree to which a substance opposes the flow of electric current through it. All substances resist electron flow to some extent. Conductors, such as metals, allow electrons to flow freely through them and have low resistance values. Insulators resist electron flow greatly and have high resistance values. Resistance is measured in ohms (⍀) using an ohmmeter. An ohmmeter is a device for measuring resistance. An ohmmeter is usually part of a multifunctional meter called a multimeter (Figure 11.16). When a substance resists the flow of electrons, it slows down the current and converts the electrical energy into other forms of energy. The more resistance a substance has, the more energy it gains from the electrons that pass through it. The energy gained by the substance is radiated to its surroundings as heat and/or light energy (Figure 11.17).
Figure 11.16 Multimeters can be used to measure potential difference, current, or resistance.
W O R D S M AT T E R Figure 11.17 When electrons pass through a resistor, such as the element on this electric
The symbol for ohm, ⍀, is the Greek letter omega.
heater, their electrical energy is converted to heat and to light.
Resistance in a Circuit The more resistance a component has, the smaller its conductivity. For example, current in a circuit might pass through the filament in a light bulb (Figure 11.18). The filament is a resistor, which is any material that can slow current flow. The filament’s high resistance to the electron’s electrical energy causes it to heat up and produce light. filament
Figure 11.18 The filament in a light bulb is an example of a resistor. Current electricity is the continuous flow of electrons in a closed circuit.
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Resistors and Potential Difference high potential energy
potential energy converted to another form of energy Figure 11.19 An electron entering a resistor is similar to a ball at the high end of a ramp, where potential energy is greater.
Figure 11.20 Resistors come in many shapes and sizes. The type of material the resistor is made from affects its resistance.
Resistors can be used to control current or potential difference in a circuit. When you work with resistors, you should always be aware that they can heat up and cause burns. Use caution when handling them. In a circuit, electrons have a higher potential difference as they enter a resistor compared to when they leave the resistor because they use up some energy in passing through the resistor. You can picture electrons entering a resistor as being at the high end of a ramp, where they have a lot of potential energy. In this analogy, electrons leaving the resistor are at the bottom end of the ramp, where their potential energy has been converted to another form of energy (Figure 11.19). Types of Resistors A wide variety of resistors are made for different applications, especially in electronics (Figure 11.20). For example, televisions contain dozens of different resistors. Resistors can be made with a number of techniques and materials, but the two most common types are wire-wound and carbon-composition. A wire-wound resistor has a wire made of heat-resistant metal wrapped around an insulating core. The longer and thinner the wire, the higher the resistance. Wire-wound resistors are available with values from 0.1 ⍀ up to 200 k⍀. The wire for a 200-k⍀ resistor is very thin. Carbon-composition resistors are made of carbon mixed with other materials. The carbon mixture is moulded into a cylinder with a wire at each end. By varying the size and composition of the cylinder, manufacturers produce resistances from 10 ⍀ to 20 M⍀. Moulded carbon resistors are cheaper to make than wirewound resistors but less precise.
Learning Checkpoint 1. What is electric current? 2. What does “resistance” refer to in terms of electron flow? 3. Copy and complete the following table in your notebook. Some answers are provided for you. Quantity
Suggested Activities • D13 Quick Lab on page 444 D14 Quick Lab on page 445 D15 Design a Lab on page 446
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Abbreviation
Unit
Symbol
Potential difference ampere ⍀
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Resistance in a Wire
Take It Further
The flow of water in pipes is another useful model of electricity (Figure 11.21). Not all pipes transport water equally well. The longer and thinner a pipe is, the more resistance it has to the flow of water. A pipe with a bigger diameter has less resistance, which allows a greater flow of water. Similarly, the amount of resistance in a circuit affects the electrical current. For any given potential difference, current decreases if you add resistance. As with water flow, you get the least resistance with a short, wide path with no obstructions. The shorter and thicker the wire, the less resistance it creates for electrons. Other factors affecting the resistance of a wire include the material it is made from and its temperature, as shown in Table 11.1.
A number of rechargeable dry cells are available, such as NiCd, NiMH, and lithium ion. Research the different types of rechargeable dry cells. Compare their composition, lifetime, cost, and ability to hold charges. Begin your research at ScienceSource.
Figure 11.21 Resistance in a pipe reduces the flow of water. The smaller the pipe, the greater the resistance, so the flow is less. Resistance in a conductor reduces the flow of electrons.
Table 11.1 Factors Affecting the Resistance of a Wire Factor
How Factor Affects Resistance
Material
Silver has the least resistance but is very expensive to use in wires. Most conducting wires are made from copper.
Temperature
As the temperature of the wire increases, its resistance increases and its conductivity decreases. In other words, a colder wire is less resistant than a warmer wire.
Length
Longer wires offer more resistance than shorter wires. If the wire doubles in length, it doubles in resistance.
Cross-sectional area
Wider wires offer less resistance than thinner wires. If the wire doubles in width, its resistance is half as great. Conducting wires that carry large currents need large diameters to lessen their resistance.
Current electricity is the continuous flow of electrons in a closed circuit.
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D13 Quick Lab Make Your Own Dimmer Switch Some homes have dimmer switches on their lights. A dimmer switch allows you to adjust light levels in a room from nearly dark to very bright by moving a lever or turning a knob.
Purpose To use resistance to control the amount of current flowing through a light bulb
Materials & Equipment • battery • connecting wires with alligator clips • flashlight bulb (2.5 W) and socket • 40-cm of 32-gauge Nichrome™ wire • piece of wood with screws (see Figure 11.22)
Procedure 1. Connect the battery to the light bulb, and set up the Nichrome™ wire on the board as shown in Figure 11.22. Make sure the Nichrome™ wire is connected at one end but not the other, leaving your circuit open. Have your teacher approve your set-up before you proceed further. 2. Close your circuit by connecting the other end of the Nichrome™ wire, maximizing the length of the wire in the circuit. Note the brightness of the bulb (Figure 11.22(a)). 3. Move the alligator clips on the Nichrome™ wire closer together (Figure 11.22(b)). Note the brightness of the bulb. 4. Continue to observe the brightness of the bulb as you move one of the alligator clips along the Nichrome™ wire.
Questions 5. (a) How did the brightness of the bulb change as you moved the alligator clips? (b) Explain why the brightness changed as the length of wire changed. 6. How do your observations in this activity help explain how a dimmer switch works?
(b)
(a)
Figure 11.22 The brightness of the bulb changes, depending on whether the space between the clips on the wire is (a) larger or (b) smaller.
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D14 Quick Lab Modelling Potential Difference, Current, and Resistance A model in science can help you picture a process or object that may be hidden from view or that may be too large or too small to view directly. You can also use a scientific model to help you communicate your ideas.
Purpose To model interactions among potential difference, current, and resistance using water flowing in a hose
6. While the water is running, pinch the end of the tubing slightly. Observe what happens to the flow. Empty the bucket (if using) when you have finished timing. 7. Record the time it takes to fill the beaker or bucket using the slightly pinched length of tubing. Empty the container when you have finished timing. 8. Record the time it takes to fill the beaker or bucket using an open length of tubing.
Materials & Equipment • 50-cm or longer length of rubber tubing
• 1000-mL beaker or bucket
• water tap and sink or bucket
• stopwatch
10. Follow your teacher’s instructions for cleaning up.
Procedure
Questions
1. Create a data table with headings like the ones shown below. Give your data table a title. 2. Attach one end of the tubing to a tap. Place the other end of the tubing in a bucket or sink as far from the tap as the tubing will reach without bending. 3. Turn on the cold water to a medium flow. Record the time it takes for water to exit the tubing. 4. Pinch the end of the tubing, and then turn off the water. Keep the end pinched. Empty the bucket (if using) when you have finished timing. 5. Turn on the cold water to a midway point, and release the end of the tubing at the same time. Record the time it takes for water to exit the tubing into the sink or bucket. Time to Exit Empty Tube (s)
9. Record the time it takes to fill the beaker or bucket using an open length of tubing and the water turned on full. Empty the container when you have finished timing.
Time to Exit Pinched Tube (s)
11. (a) How did the exit times compare for the tubes in step 3 and step 5? (b) How would you explain any difference in times? 12. What part of this activity modelled electric current in a circuit? 13. (a) How does the size of the opening in the tubing affect water flow? (b) Relate the size of the opening of the tubing to resistance in wires. 14. (a) How does how far a tap is opened affect water flow through the tubing? (b) Relate how far a tap is opened to potential difference in a circuit.
Time to Fill Beaker or Bucket with Pinched Tube (s)
Time to Fill Beaker or Bucket with Open Tube (s)
Time to Fill Beaker or Bucket with Water on Full (s)
Current electricity is the continuous flow of electrons in a closed circuit.
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D15 Design a Lab
Skills Reference 2
Investigating Conductivity Question How does the conductivity of different solutions compare?
Materials & Equipment • 100-mL graduated cylinder • 250-mL beaker • distilled water • conductivity tester • tap water
• vinegar • copper(II) sulphate solution • other solutions provided by your teacher
• salt water
Using equipment, materials, and technology accurately and safely Adapting or extending procedures
4. Place the metal tips of the conductivity tester in the distilled water (Figure 11.23). Record the conductivity reading of the distilled water in your table. If your conductivity tester is a light bulb, describe the brightness of the bulb. 5. Repeat steps 3 and 4 with 50-mL samples of tap water, salt water, vinegar, copper(II) sulphate solution, and any other solutions your teacher provides for you to use. After each conductivity measurement, empty the beaker as directed by your teacher and rinse it with distilled water. Also, wipe off the tips of the conductivity tester. Make sure that you insert the tips to the same depth in each solution. 6. Clean up your work area. Make sure to follow your teacher’s directions for safe disposal of materials. Wash your hands thoroughly.
Part 2 7. Plan an investigation to compare the conductivity of other solutions. Have your teacher approve your plan, and then conduct your investigation.
Analyzing and Interpreting
Figure 11.23 Conductivity tester
9. Rank the substances in order of high conductivity to low conductivity.
Procedure Part 1
10. How did your results compare with your predictions?
1. Read through the procedure. Then, design a data table to record your predictions and your conductivity readings of the solutions you will test. Give your table a title. 2. Predict which solutions will be the best conductors and which will be the poorest conductors. Record your predictions and the characteristics on which you are basing your predictions. 3. Put 50 mL of distilled water into a 250-mL beaker.
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8. How did you determine whether there were differences in conductivity between the solutions you tested?
The Characteristics of Electricity
Skill Practice 11. Make an hypothesis about why there were differences in conductivity between the solutions.
Forming Conclusions 12. Write a summary of your results that answers the question “How does the conductivity of different solutions compare?”
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11.1 CHECK and REFLECT 13. Make a list of similarities between the flow of water and an electric circuit.
Key Concept Review 1. (a) Describe the two main components of an electrochemical cell. (b) How does a wet cell produce electricity? 2. What direction do electrons flow in a circuit? 3. (a) What device measures potential difference?
14. A student is planning to test several different electrode combinations to see which would produce the greatest potential difference in a wet cell. State whether each of her choices will work. Explain why or why not. Her choices for electrodes are as follows: (a) both zinc (b) zinc and copper
(b) What are the units for measuring potential difference?
(c) both copper 15. The illustration below shows a design for a dry cell. How does this design differ from the dry cell shown in Figure 11.6 on page 435?
4. (a) What device measures current? (b) What are the units for measuring current? 5. What is the difference between potential difference and current?
zinc can (negative electrode)
insulated casing
insulator
positive terminal
6. What is the difference between DC electricity and AC electricity? 7. (a) What is the function of an electrical load in a circuit? (b) List four examples of electrical loads. 8. What does resistance refer to in a circuit? 9. What is the role of a resistor in a circuit? 10. What are four factors affecting resistance in a wire?
electrolyte paste
negative terminal
carbon electrode
insulator
Question 15
Reflection
Connect Your Understanding 11. Why must a circuit be closed in order for a current to flow?
16. What do you now understand about current electricity that you did not know before reading this chapter?
12. Use a three-circle Venn diagram to compare and contrast alternating current, direct current, and static electricity.
For more questions, go to ScienceSource.
Current electricity is the continuous flow of electrons in a closed circuit.
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Series Circuits and Parallel Circuits
Here is a summary of what you will learn in this section: • A circuit diagram represents an electric circuit. • An ammeter is hooked up in series to measure current. • A voltmeter is hooked up in parallel to measure voltage. • In a series circuit, the current is constant and the voltages across resistors add up to the total voltage. • In a parallel circuit, the voltages are constant and the currents on each path add up to the total current.
Figure 11.24 These toy robot dogs are controlled by electric circuits.
Designing Circuits Computers and the toy robots in Figure 11.24 have complex circuits. Other electrical devices such as a flashlight or a hair dryer have much simpler circuits. The simplest circuit is a loop. An ordinary flashlight can be designed this way. If you take a flashlight apart, you will probably find a light bulb, some wire, a couple of batteries, and a plastic casing to hold and protect the electrical parts. This design works very well for providing light when it is dark. It also works well in terms of cost. Flashlights are easy to build with readily available materials and can be assembled efficiently. A simple loop isn’t always the best design when there are a variety of different components in the circuit. Designers have to ensure that one component does not depend on another. For example, it would be very frustrating to the user if the toy robot stopped working because one of its light bulbs went out. You would probably be upset if your computer at school stopped working because an LED indicator burnt out. In these devices, multiple electrical loops are used so that if one component stops working, the rest of the device will continue to function.
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Tiny Circuits Conventional switches and other electrical components are practical and convenient for homes or simple electrical devices. But for the miniature circuits in advanced electronic devices such as computers, transistors must be used instead. A transistor is a tiny device that acts as a switch or amplifier in a circuit. Transistors are often referred to as solid-state components because they are made of solid material with no moving parts. Most transistors are constructed with three layers of specially treated silicon. These layers are arranged so that a small potential difference through the middle layer controls a current between the outer layers. In this way, transistors can act as switches. Microcircuits (also called integrated circuits) are made up of microscopic transistors and other electrical devices. A microcircuit is exactly what its name suggests: a circuit on an extremely small scale. Microcircuits regularly contain more than a million components per square centimetre (Figure 11.25).
Figure 11.25 A microcircuit is usually called a “chip” or a “microchip.”
D16 Quick Lab Keep the Lights On Current flows when a circuit is complete. If there is a break in a circuit, due to a burned-out bulb, for example, the current cannot continue. In this activity, you will investigate how to keep current flowing through a circuit even though one bulb may be burned out or missing.
Purpose To compare the flow of electrons in two different circuits
Procedure 1. Circuit A: Using any of the materials, hook up three bulbs in a row so they all light up. Make a labelled diagram of your set-up. 2. Circuit B: Hook up all three bulbs so that you can remove one bulb without disconnecting the wires and still have the other bulbs stay on. Make a labelled drawing of your set-up.
Questions 3. (a) What would happen to the other two bulbs if you removed one bulb in Circuit A?
Materials & Equipment • 1 D dry cell • 5 insulated copper wires with both ends bare • three 2.0-V flashlight bulbs CAUTION: Open the circuit if the wires get hot.
(b) Why would this happen? 4. Why did the other two bulbs stay lit when you removed one bulb in Circuit B? 5. Draw a circuit that would allow you to remove two bulbs and yet have the third bulb stay lit. Have your teacher approve your drawing. If time allows, test your ideas by building the circuit.
Current electricity is the continuous flow of electrons in a closed circuit.
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Circuit Diagrams
load
switch conducting wire
electrical source
Figure 11.26 The four basic parts of
a circuit
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Engineers and designers of electrical circuits use special symbols that show the components and connections in a circuit. These symbols make it easier to plan and analyze a circuit before you build it. A drawing made with these symbols is called a c i rc ui t d i agra m. You can use the symbols in Table 11.2 to draw and interpret circuit diagrams (Figure 11.26). Knowing the basic circuit symbols can help you analyze existing circuits and make it easier to understand where the current flows and how a device functions. Follow these rules when you draw circuit diagrams. • Always use a ruler to draw straight lines for the conducting wires. • Make right-angle corners so that your finished diagram is a rectangle. Table 11.2 Circuit Symbols Symbol
Component
Function
wire
conductor; allows electrons to flow
cell, battery
electrical source; longer side is the positive terminal, shorter side is the negative terminal
lamp (light bulb)
specific load; converts electricity to light and heat
resistor
general load; converts electricity to heat
switch
opens and closes the circuit
ammeter
measures current through a device, connected in series
voltmeter
measures voltage across a device, connected in parallel
Learning Checkpoint 1. What is a circuit diagram? 2. What are two rules you should follow when you draw a circuit diagram? 3. Draw the circuit symbol for: (a) a light bulb (b) an ammeter (c) a voltmeter 4. Draw a circuit diagram for a circuit that includes a resistor, a switch, conducting wires, and a battery.
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Series Circuits A s e r i e s c i rc u i t is an electric circuit in which the components are arranged one after another in series (Figure 11.27). A series circuit has only one path along which electrons can flow. If that pathway is interrupted, the whole circuit cannot function. The amount of current is the same in all parts of a series circuit. However, if you add more resistors, you increase the total resistance of the circuit. This decreases the current. Adding an extra bulb to a series string of lights makes all the bulbs dimmer. Electrons use up all their potential difference going around a series circuit no matter how many loads are in the circuit. For example, the electrons that leave a 12-V battery will “lose” all 12 V before they return to the battery. Each load will use part of the total potential difference, depending on how much it resists the flow of electrons.
Figure 11.27 A series circuit has only one path along which current can flow.
junction point
Parallel Circuits A p a ra l l e l c i rc u i t is an electric circuit in which the parts are arranged so that electrons can flow along more than one path (Figure 11.28). The points where a circuit divides into different paths or where paths combine are called junction points. An interruption or break in one pathway does not affect the other pathways in the circuit. Similarly, adding a new pathway with more resistors does not affect the resistance in any of the other pathways. In fact, adding extra resistors in parallel decreases the total resistance of the circuit. This might seem strange, but think about how much less resistance there is when you drink through two straws instead of one. Most electrons will follow the path with the smallest resistance values. Therefore, the amount of current is greater on the paths with the smaller resistances (Figure 11.29). Each electron has the same amount of energy, and electrons must expend all their energy on the path they are on. This is why the potential difference across parallel resistors will always be the same, even though the resistors themselves are of different values. Table 11.3 on the next page summarizes the characteristics of current and potential difference in series and parallel circuits.
Figure 11.28 In a parallel circuit, each component has its own path for current.
3.0 A
2.0 A
1.0 A
6.0 A
Figure 11.29 Loads of different resistance that are connected in parallel have different currents.
Current electricity is the continuous flow of electrons in a closed circuit.
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Table 11.3 Potential Difference, Current, and Resistance in Series and Parallel Circuits Circuit
Potential Difference
Current
Resistance
Series circuit
Each load uses a portion of the total potential difference supplied by the battery.
The current is the same throughout a series circuit.
The current decreases when more resistors are added.
Parallel circuit
Each load uses all the potential difference supplied by the battery.
The current divides into different paths. A pathway with less resistance will have a greater current.
Adding resistors in parallel decreases the total resistance of the circuit.
Two Types of Circuits Suggested Activities • D17 Quick Lab on page 453 D19 Inquiry Activity on page 455 D20 Inquiry Activity on page 456
Figure 11.30 A combination circuit. The switch in this circuit can turn all the bulbs on or off.
What happens when one light bulb burns out in a long string of decorative lights? If the set of lights is wired in series, the current must flow through one light before it gets to another light. When one light burns out, all lights go out because the current cannot flow past a burned-out bulb. If the set of lights is wired in parallel, the current takes several different paths. If a light on one path goes out, current does not flow on that path. However, there are other paths where the current does flow and lights on those paths remain lit. Series circuits and parallel circuits make up the circuits in your home and school. Some circuits are combinations of series circuits and parallel circuits (Figure 11.30). These combinations help prevent problems such as the refrigerator turning off because a light bulb burned out in a bedroom. It is an important safety feature in a combination circuit to have some switches wired in series, because it is sometimes necessary to turn off the electricity in part or all of a home (Figure 11.31).
Figure 11.31 A typical home has many parallel circuits.
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Learning Checkpoint
Take It Further
1. Draw a circuit diagram of a series circuit with a battery, connecting wires, and one light bulb. 2. Draw a circuit diagram of a parallel circuit with a battery, connecting wires and two light bulbs. 3. What happens to the voltage in a series circuit when more loads are added?
A microcircuit is an extremely small circuit that may contain more than a million parts in a square centimetre. Find out how these tiny circuits are controlled and used. Begin your research at ScienceSource.
4. What happens to the current in a parallel circuit when more loads are added? 5. How do combination circuits help prevent problems in circuits in a home?
D17 Quick Lab Off and On Suppose that all the lights in your home were connected in one simple circuit. When you closed a switch, every light would come on. When you opened the switch, every light would turn off. This arrangement would not be very practical for most uses. Instead, lights can be connected in a circuit in such a way that some can be turned on while others are turned off. In this activity, you will investigate how to create such a circuit.
Purpose To design and build a circuit that can have lights turned on and off individually
Procedure 1. Circuit A: Design and draw a circuit diagram where the three bulbs can be either all on or all off. 2. Circuit B: Design and draw a circuit diagram where each of the three bulbs in the circuit can be turned off and on individually. 3. Circuit C: Design and draw a circuit diagram where two bulbs can be turned off while one stays on. 4. Have your teacher approve your three circuit diagrams. Then, hook up the circuits and test whether they work. 5. Clean up your work area.
Materials & Equipment
Questions
• 3 or more flashlight bulbs with holders • connecting wires • 3 D dry cells • switches for each light CAUTION: Open the circuit if the wires get hot.
6. For each circuit, describe whether the lights were hooked up in series, in parallel, or in a combination. 7. Was the brightness of the lights affected by changing how the bulbs were hooked up? Explain.
Current electricity is the continuous flow of electrons in a closed circuit.
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D18 Skill Builder Activity Using Equipment Accurately and Safely Part 1 — Measuring Current Measuring current involves measuring the amount of charge passing a given point per second. The current is fed directly into the ammeter or multimeter where it is counted and then let back out into the circuit. The ammeter is hooked in series into the circuit, then the circuit is reconnected and the measurement is taken. Follow these steps to hook up the ammeter. 1. Attach a battery and three resistors in series. Open the circuit. 2. Hook your ammeter in series next to the positive side of the battery. Be sure to connect the positive (red) terminal of the ammeter to the positive (+) terminal of the battery. Connect the negative (black) terminal of the ammeter to the negative (–) terminal of the battery. 3. Set the meter on the highest setting, and then lower the setting until you have the highest possible reading. Record the reading. 4. Open the circuit and move the ammeter to immediately beyond the first resistor. Repeat steps 2 and 3. 5. Repeat step 4 for each resistor. CAUTION: Open the circuit if the wires and resistors get hot.
Part 2 — Measuring Voltage 6. To insert a voltmeter in a circuit, simply connect the two wires from the terminals of the voltmeter to opposite sides of the component for which you want to measure the voltage (Figure 11.32). 7. To find the voltage across an electrical source, connect the meter by attaching the red lead to the positive terminal and the black lead to the negative terminal. This allows you to take a reading on both sides of the source. The meter indicates the change in voltage. 8. To find the voltage across a resistor or load in a circuit, connect a lead to each side of the resistor. Connect the black lead closest to the negative side of the source and the red lead closest to the positive side of the source. This method of connection is called connecting in parallel. By measuring voltage across the resistor, you are measuring the voltage drop as the current moves through the resistor. 9. Your teacher will provide you with various types of dry cells and batteries. Use the voltmeter to test and report on the voltage of each cell and battery. Compare your readings with the voltage numbers that are written on their labels. If a multimeter is available, use it to repeat your measurements and then compare the results. 10. Hook two or three dry cells in series. Do this by placing them end to end with the positive end of one dry cell touching the negative end of the other dry cell. Predict the voltage reading, and then use the voltmeter to see if your prediction was correct. 11. Clean up your work area.
Figure 11.32 A voltmeter connected across a resistor
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D19 Inquiry Activity
Skills Reference 2
Series Circuit Analysis Question
3. Record the voltage across each resistor and the power supply.
What are the properties of a series circuit?
4. Open the switch, and move the ammeter to a position between the first two resistors. Close the switch, and record the current coming out of resistor 1.
Materials & Equipment • 6.0-V battery
• multimeter (or voltmeter and ammeter)
• three 100-⍀ resistors • switch
5. Open the switch, and move the ammeter to a position between the second and third resistors. Close the switch, and record the current coming out of resistor 2.
• connecting wires CAUTION: Open the circuit if the wires and resistors get hot.
Procedure Part 1 — Measuring Voltage and Current 1. Create a data table similar to the one below. Give your table a title. Power Supply
Resistor 1
Planning for safe practices in investigations Gathering, organizing, and recording relevent data from inquiries
Resistor 2
Resistor 3
Part 1: Current
6. Open the switch, and move the ammeter to a position between the third resistor and the source. Close the switch, and record the current coming out of resistor 3.
Part 2 — Changing Resistance 7. Open the switch, and remove one resistor. Close the switch. Measure and record the current. 8. Measure and record the voltage across the power supply and across each of the two resistors.
Analyzing and Interpreting 9. State what you noticed in Part 1 about the:
Voltage
(a) current across the resistors in all cases
Part 2: Current
(b) sum of all voltages across the resistors 10. State what happened in Part 2 to:
Voltage
(a) the current 2. Construct the circuit shown in Figure 11.33. Keep the switch open until your teacher approves your circuit. Then close the switch and record the current coming out of the power supply. A
(c) the sum of the voltages across the resistors 11. What is the effect of adding an identical load in series in a simple circuit?
Skill Practice 12. Did the voltages across any resistors equal the total voltage provided by the source? Explain why they did or did not.
6.0 V
V
resistor 1
(b) the voltages across each resistor
resistor 2
resistor 3
Figure 11.33 Construct this circuit in step 2.
Forming Conclusions 13. In a paragraph, summarize the properties of a series circuit. Current electricity is the continuous flow of electrons in a closed circuit.
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D20 Inquiry Activity
Skills Reference 2
Parallel Circuit Analysis Question
3. Record the voltage across each resistor and the power supply.
What are the properties of a parallel circuit?
4. Open the switch, and move the ammeter to a position between the first two resistors. Close the switch, and record the current coming out of resistor 1.
Materials & Equipment • multimeter (or voltmeter and ammeter)
• 6.0-V dry cell • three 100-⍀ resistors • connecting wires
5. Open the switch, and move the ammeter to a position between the second and third resistors. Close the switch, and record the current coming out of resistor 2.
• switch CAUTION: Open the circuit if the wires and resistors get hot.
Procedure Part 1 — Potential Difference and Current Measurements
Resistor 1
Resistor 2
6. Open the switch, and move the ammeter to a position between the third resistor and the source. Close the switch, and record the current coming out of resistor 3.
Part 2 — Changing Resistance 7. Open the switch, and remove one resistor. Close the switch. Measure and record the current.
1. Create a data table similar to the one below. Give your table a title. Power Supply
Selecting instruments and materials Observing, and recording observations
Resistor 3
Part 1: Current
8. Measure and record the voltage across the power supply and across each of the two resistors.
Analyzing and Interpreting 9. State what you noticed in Part 1 about the: (a) current across the resistors in all cases
Voltage
(b) sum of all voltages across the resistors
Part 2: Current
10. State what happened in Part 2 to: (a) the current
Voltage
2. Construct the circuit shown in Figure 11.34. Keep the switch open until your teacher approves your circuit. Then, close the switch and record the current coming out of the power supply.
(b) the voltages across each resistor (c) the sum of the voltages across the resistors 11. What is the effect of adding an identical load in parallel in a simple circuit?
Skill Practice resistor 3
V
resistor 2
6.0 V
resistor 1
A
12. Did the voltages across any resistors equal the total voltage provided by the source? Explain why they did or did not.
Forming Conclusions Figure 11.34 Construct this circuit in step 2.
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13. In a paragraph, summarize the properties of a parallel circuit.
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11.2 CHECK and REFLECT 4. (a) Draw a circuit diagram that shows three resistors in series.
Key Concept Review 1. Copy and complete the following chart in your notebook. Voltage and Current in Circuits In a Series Circuit
In a Parallel Circuit
Voltage
2. (a) Draw a circuit diagram of the circuit shown here.
Connect Your Understanding 6. You have three light bulbs, each with a different resistor. The amount of current through a bulb will affect how much light it emits.
(b)
(c) –
(c) Draw a circuit diagram that shows one resistor in series and two resistors in parallel. 5. Suppose two pathways in a parallel circuit have different resistances. Will the current in each pathway be the same? Explain.
Current
+
(a) Will the order in which you hook up the light bulbs in series affect the intensity of light each emits? Explain.
(a)
(d)
(b) Draw a circuit diagram that shows three resistors in parallel.
(b) What happens when you hook up the bulbs in parallel?
Question 2
(b) Is this a series circuit or a parallel circuit? (c) How do you know? 3. What is the voltage across the source in each of these circuits?
7. Electrons in a circuit can be compared to a group of shoppers who go out to spend money in shops. Use this analogy or create one of your own to explain the following. Include a labelled diagram as part of your answer for each one. (a) potential difference, current, and resistance in a series circuit
(a)
(b) potential difference, current, and resistance in a parallel circuit 2.0 V
4.0 V
6.0 V
Reflection (b)
12 V
12 V
12 V
8. What images or memory aids help you remember the differences between series and parallel circuits? For more questions, go to ScienceSource.
Current electricity is the continuous flow of electrons in a closed circuit.
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Ohm’s Law
Here is a summary of what you will learn in this section: • Ohm’s law, V = IR, describes the relationship between potential difference, current, and resistance. • In a short circuit, the current does not take the intended path back to its source. • Fuses and circuit breakers are safety devices.
Figure 11.35 Potential difference, current, and resistance have the same relationship in microcircuits in a computer circuit board like this one as they do in the wiring in homes and offices.
A Fascination with Electricity
Figure 11.36 Georg Ohm (1789–1854)
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The circuit boards in the computers you use work because of the relationships between potential difference, current, and resistance (Figure 11.35). These relationships have been understood for about 200 years because of the work of Georg Ohm. Georg Simon Ohm (Fig 11.36) was like any German boy in the early 1800s. At the local high school, he studied physics, chemistry, math, and philosophy. He spent most of his free time playing billiards, ice skating, and dancing with his friends. No one imagined that one day he would be a famous name in science. His journey to discovering a scientific law began after graduation when he went to a private school in Switzerland to teach. Here Ohm taught mathematics, but secretly he dreamed of studying with great mathematicians at an important university. To achieve his dream, he continued to study mathematics and teach. One day, he was asked to instruct in the electricity labs. This day was a turning point in Georg Ohm’s life. Fascinated by electricity, he immersed himself in the study of the characteristics of potential difference, current, and resistance.
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Ohm’s passion and commitment to his studies led to a deep understanding of how these different electrical concepts were related. Much of what he discovered you have already learned in this unit. He stated these discoveries in what is today called Ohm’s law. A law in science is a generalization based on collection of observable evidence. It is the conclusion of this evidence and can be defended by repeating a variety of experiments over many years. A scientific law becomes accepted by the scientific community as a description of our natural world. Ohm’s law established the relationships between potential difference (V ), current (I), and resistance (R). The symbol for resistance is called the ohm (⍀) in honour of Georg Ohm’s work in this field.
W O R D S M AT T E R
The symbol “I ” is used for current because it stands for “intensity.”
D21 Quick Lab Potential Difference, Current, and Resistance Using the equipment available in your science class, you can investigate the same relationships between potential difference, current, and resistance that Georg Ohm did over 200 years ago.
Purpose To observe how potential difference, current, and resistance are related
Procedure 1. Create a table like the one below to record the data you will collect. Give your table a title. 2. Connect one resistor into a simple circuit. If you are using a voltmeter and ammeter, connect these devices as well. Keep your circuit open until your teacher has approved your set-up. 3. Close your circuit. 4. Measure and record the voltage across the resistor.
Materials & Equipment
5. Measure and record the current through the resistor.
• 1.5 V dry cell • resistors, any values from 15 ⍀ to 50 ⍀ • connecting wires
6. Record the resistance of the resistor you used.
• switch
7. Repeat steps 2 to 6.
• multimeter or voltmeter and ammeter
Trial
1.
Resistance (⍀)
Current (A)
Potential Difference (V)
8. Clean up your work area. Resistance ⴛ Current
Question 9. Multiply the resistance by the current for each of the trials you completed. What can you infer from your answers?
2.
Current electricity is the continuous flow of electrons in a closed circuit.
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Potential Difference, Current, and Resistance I V V
R V = IR
Figure 11.37 Ohm’s law states that potential difference (V) equals current (I) times resistance (R).
Suggested Activities • D23 Inquiry Activity on page 465 D24 Inquiry Activity on page 466
Practice Problems
1. A current of 1.5 A flows through a 30-⍀ resistor that is connected across a battery. What is the battery’s voltage? 2. If the resistance of a car headlight is 15 ⍀ and the current through it is 0.60 A, what is the voltage across the headlight? 3. The current in a circuit is 0.50 A. The circuit has two resistors connected in series: one is 110 ⍀ and the other is 130 ⍀. What is the voltage in the circuit?
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Georg Ohm described how potential difference and current are affected when one of the values is changed. He realized that the potential difference (V) in a circuit is equal to the current (I) multiplied by the resistance (R). Ohm’s law states that, as long as temperature stays the same, V = IR (Figure 11.37). In other words: • the resistance of a conductor remains constant • the current is directly proportional to the potential difference Table 11.4 and the following examples show how to use Ohm’s law to calculate unknown quantities. Table 11.4 Ohm’s Law
Known Quantity
Symbol
Unknown Quantity
Symbol
Unit
Equation
Current, resistance
IR
potential difference
V
V
V = IR
Potential difference, resistance
VR
current
I
A
I=V R
Potential difference, current
VI
resistance
R
⍀
R=V I
Example Problem 11.1 A current of 4.0 A flows through a 40-⍀ resistor in a circuit. What is the voltage? Given Current I = 4.0 A Resistance R = 40 ⍀ Required Voltage V = ? Analysis and Solution The correct equation is V = IR. Substitute the values and their units, and solve the problem. V = IR = (4.0 A)(40 ⍀) = 160 V Paraphrase The voltage in the circuit is 160 V.
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Example Problem 11.2
Practice Problems
A 30-V battery generates a current through a 15-⍀ resistor. How much current does the battery generate? Given Voltage V = 30 V Resistance R = 15 ⍀ Required Current I = ?
1. A firetruck has a searchlight with a resistance of 60 ⍀ that is placed across a 24-V battery. What is the current in this circuit? 2. A bulb of 15-⍀ resistance is in a circuit powered by a 3-V battery. What is the current in this circuit?
Analysis and Solution The correct equation is I = V . R Substitute the values and their units, and then solve the problem. I=V R
3. What would the current be in question 2 if you changed to a 45-⍀ bulb?
= 30 V = 2 A 15 ⍀ Paraphrase A current of 2 A is generated.
Example Problem 11.3
Practice Problems
An electric stove is connected to a 240-V outlet. If the current flowing through the stove is 20 A, what is the resistance of the heating element? Given Voltage V = 240 V Current I = 20 A
1. A current of 0.75 passes through a flashlight bulb that is connected to a 3.0-V battery. What is the bulb’s resistance? 2. A current of 625 mA runs through a bulb that is connected to a 120-V power supply. What is the resistance of the bulb?
Required Resistance R = ? Analysis and Solution V The correct equation is R = . I Substitute the values and their units, and then solve the problem. R=V I = 240 V = 12 ⍀ 20 A
3. A table lamp draws a current of 200 mA when it is connected to a 120-V source. What is the resistance for the table lamp?
Paraphrase The resistance of the heating element is 12 ⍀. Current electricity is the continuous flow of electrons in a closed circuit.
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During Reading Definitions in Context Often, unfamiliar terms are defined right in the text that you are reading. You don’t need to look them up in a glossary or dictionary. Look for the boldfaced words, and then find the definition in the sentence either before or after the term. Add words and definitions to your personal list of terms.
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Ohm’s Law and Temperature Ohm’s law works for most circuits. However, temperature affects resistance. Generally, resistance is lower when a conductor is cooler. As the temperature increases, resistance increases. For example, a filament in an incandescent light bulb often has 10 times its normal current flowing through it at the instant it is switched on. This current heats the filament white-hot in a fraction of a second. The huge rise in temperature greatly increases the filament’s resistance, which reduces the current flowing through it. Light bulb filaments sometimes burn out when they are switched on because of the sudden temperature change and other forces caused by the large initial current.
Short Circuits short circuit
Figure 11.38 Current can flow more easily through the wire path than through the light bulb. This creates a short circuit, which could be dangerous.
Sometimes a wire’s insulation breaks down or another problem develops that allows electrons to flow through a device along a different path than the one intended. The device develops a short circuit. A short circuit is an accidental low-resistance connection between two points in a circuit, often causing excess current flow (Figure 11.38). Not only do short circuits mean that your electrical device will not work, they can also be dangerous. The conducting wires can quickly become hot and can start a fire. One danger from short circuits occurs when a transmission line has been knocked down in a storm. Without a complete path, the electricity cannot flow. However, if you come in contact with the wire, the electricity will take a path through your body to the ground and seriously injure or kill you. The driver shown in Figure 11.39 is safe as long as he is inside the truck. If he has to leave, he would need to jump free, not step out. He has to jump so he does not provide a path for the electricity to flow through him to the ground. There are times when a technician must short out part of a circuit intentionally by connecting a wire across a load in parallel. The low-resistance wire causes the current to flow through it rather than through the higher resistance device. This allows the technician to work on the device without interrupting the rest of the circuit.
Figure 11.39 The driver should stay in the truck and wait for help.
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Electrical Safety All electrical appliances present a risk of electric shock. Always handle electrical appliances properly and observe all safety precautions. Be careful to disconnect the plug before handling an appliance. Some electronic devices, such as computers, retain electric charge even when they are unplugged (Figure 11.40). This is why many electrical devices have a “Do Not Open” warning printed on them. Take the warning seriously, and do not attempt to repair the device yourself. Instead, contact a repair technician.
Fuses and Circuit Breakers In electric circuits in your home, fuses and circuit breakers act as a first line of defence if something goes wrong. A fuse is a safety device in an electric circuit that has a metallic conductor with a low melting point compared to the circuit’s wires (Figure 11.41). If the current gets too high, the metal in the fuse melts and the current flow stops. This prevents further problems, such as damage to your electrical components or a possible fire. A blown fuse must be physically replaced as it can work only once. The symbol represents a fuse in a circuit diagram. A circuit breaker does the same job as a fuse except that the wire inside does not melt. Instead, the wire heats up and bends, which triggers a spring mechanism that turns off the flow of electricity. Once the breaker has cooled, it can be reset. Older homes and apartment buildings tend to have fuse panels, whereas modern buildings have breaker panels (Figure 11.42).
Figure 11.40 Some electronic devices, such as this computer, store electrical energy even when the device is not plugged in.
Figure 11.41 Examples of fuses. A normal current can pass through a fuse, but a higher than normal current or short circuit will melt the metal in the fuse.
Figure 11.42 Circuit breakers help prevent electric overloads. Current electricity is the continuous flow of electrons in a closed circuit.
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Three-Prong Plug Another safety feature is the three-prong electrical plug shown in Figure 11.43. The third prong of a three-prong electrical plug connects the device to the ground wire of the building. The ground wire sends any unwanted current flow directly to the ground. Instead of electricity travelling to the metal body of the device and shocking a person using the device, the current is directed to the ground.
Ground Fault Circuit Interrupter Take It Further Diodes are devices that allow electric current to flow in one direction but not in the opposite direction. Find out how diodes are used in microcircuits and other circuits. Start your research at ScienceSource.
Some appliances and devices have an added safety feature. A ground fault circuit interrupter (GFCI) or residual current device is a device that detects a change in current and opens the circuit, stopping current flow (Figure 11.44). For example, if an appliance gets wet while you are handling it and some current starts to flow through the water, the GFCI opens the circuit so there is less chance of injury to you. Remember, it is extremely dangerous to use any electrical device around water, including radios or televisions.
Figure 11.43 One prong in a three-prong plug carried the current to the load, another prong returns the current to the source, and the third prong directs the current to the ground in the case of a short circuit.
D22
Figure 11.44 Ground fault circuit interrupters are part of some electric sockets.
STSE Science, Technology, Society, and the Environment
Electrical Safety Imagine you have just been hired as a consultant by the Electrical Safety Authority of Ontario to help create awareness of electrical safety for kindergarten students.
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1. Work alone, with a partner, or in a small
group to create an electrical safety poster or brochure that can be shared with a kindergarten class. Be sure to choose electrical safety points that are relevant to young children and to communicate them in an engaging way.
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D23 Inquiry Activity
Skills References 2, 10
Interpreting data/information to identify patterns or relationships Drawing conclusions
Investigating Ohm’s Law Question How are potential difference, current, and resistance related?
3. Have your teacher approve your circuit, and then close the switch. Quickly measure and record current and voltage. Open the switch. 4. Replace resistor 1 with resistor 2. Repeat step 3. 5. Connect a second 1.5-V dry cell in series with the first cell in the circuit. Repeat steps 3 and 4, measuring current and voltage for each resistor.
Materials & Equipment • four 1.5-V dry cells
• switch
• connecting wires
• 2 different resistors between 100 ⍀ and 300 ⍀
• voltmeter, ammeter
CAUTION: Disconnect the circuit if the wires or resistors get hot.
6. Connect a third 1.5-V dry cell into the circuit. Repeat steps 3 and 4. 7. Connect a fourth 1.5-V dry cell. Repeat steps 3 and 4. 8. Calculate your measured resistance for each . resistor using R = V I
Procedure 1. Set up a data table like the following. Fill in the resistor value for the two resistors you will be using. Examples below are 100 ⍀ and 200 ⍀. Give your table a title. Resistor (⍀) 1.5 V
3.0 V
4.5 V
6.0 V
Voltage (V)
Current (A)
Calculated Resistance
Analyzing and Interpreting 9. (a) How did your calculated values for resistors compare with their actual values? (b) Explain possible reasons for any difference between the two values. 10. Compare your data for all resistor 1 trials. When voltage is increased across a resistor, what happens to the current?
1. 100 2. 200 1. 100
11. Compare your data for all resistor 2 trials. When voltage is increased across the resistor, what happens to the current?
2. 200 1. 100 2. 200
Skill Practice
1. 100
12. What would happen to the current values if you used a resistor with double the value of resistor 2?
2. 200
2. Construct the following circuit using resistor 1 and one 1.5 V dry cell (Figure 11.45).
Forming Conclusions 13. Describe the relationship between potential difference, current, and resistance.
A
V
Figure 11.45 Construct this circuit in step 5.
Current electricity is the continuous flow of electrons in a closed circuit.
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DI Key Activity
SKILLS YOU WILL USE
D24 Inquiry Activity
Skills Reference 2
Justifying conclusions Identifying sources of error
Resisting the Flow Question Do different materials have different values of electrical resistance?
Materials & Equipment • connecting wires • D cell and holder • voltmeter • ammeter or current sensor • 10-cm length of solid graphite (pencil lead) • 10-cm length of copper wire
• 10-cm length of Nichrome™ wire • 10-cm length of rubber tubing • optional: 10-cm lengths of various other materials • calculator
CAUTION: Open the circuit if the wires or the resistors get hot.
6. Repeat steps 4 and 5 for the copper wire, Nichrome™ wire, rubber tubing, and the other materials. 7. Clean up your work area.
Analyzing and Interpreting
Procedure 1. Make a table for recording your data (Figure 11.46). The table should include these headings: Substance, Length Connected (10 cm or 1 cm), Voltage (from step 2), Current, and Resistance. In the “Resistance” column, you will calculate the resistance for each observation. Give your table a title. 2. Use connecting wires to connect each end of a D cell to a terminal on the voltmeter. Record the voltmeter reading in your table. Disconnect the voltmeter.
V to calculate the I resistance for each current recorded in your table.
8. Use Ohm’s law R =
9. (a) Which substance had the greatest resistance? (b) Explain any differences in resistance among the materials. 10. What was the effect of moving the connecting wires so that the current travelled through a shorter length of the conductor? Explain.
Skill Practice
3. Connect one wire from the D cell to a terminal of the ammeter (or current sensor). Attach another connecting wire to the other terminal of the ammeter.
11. (a) How precise were your measurements?
4. Clip the free ends of the connecting wires onto the ends of a 10-cm length of solid graphite. Record the reading on the ammeter.
Forming Conclusions
5. Move the clips on the graphite so that they are 1.0 cm apart. Record any change in the reading. 466
Figure 11.46 Determining resistance
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(b) What sources of error could have affected the accuracy of your results?
12. Write a summary that answers the question: Do different materials have different values of electrical resistance? Use your data to support your answer.
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11.3 CHECK and REFLECT Key Concept Review
Connect Your Understanding
1. (a) How is current related to potential difference in a circuit?
8. What is the resistance in the circuit shown here?
(b) How is current related to resistance in a circuit?
3.0 A
2. What does Ohm’s law state? 6.0 V
3. Copy this table into your notebook, and complete the values for potential difference, current, and resistance in an electric circuit. Question 8
Potential Difference, Current, and Resistance V
I
50 ⍀
0.5 V 20 A 6.0 V
9. A 12-⍀ light bulb is in a series circuit powered by a 6.0-V battery.
R
(a) What is the current in the circuit?
100 ⍀
(b) If you changed the 12-⍀ bulb to a 24-⍀ bulb, what current would be drawn from the battery?
4.0 A
4. What is each of these meters called?
10. (a) If a 36-⍀ bulb is added in series in the circuit in question 9(a), what is the current in the circuit?
(a)
(b) What is the potential difference across each bulb? 11. In a circuit where voltage is kept constant, state what happens to current if resistance is:
(b)
(a) doubled (b) quadrupled 12. (a) Why is a ground fault circuit interrupter necessary for electrical devices that are used around water?
5. What does each meter in question 4 measure? 6. Draw labelled circuit diagrams to show how each meter in question 4 is connected in a: (a) series circuit
(b) List three devices that should include a ground fault circuit interrupter.
Reflection
(b) parallel circuit
13. What questions about electricity would you like to have answered?
7. (a) What is a fuse? (b) What is a fuse used for? (c) If a fuse melts, does it create an open circuit, a closed circuit, or a short circuit?
For more questions, go to ScienceSource.
Current electricity is the continuous flow of electrons in a closed circuit.
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CAREERS
in Science
Great CANADIANS in Science
Max Donelan
Investigating
Award-winning Canadian scientist Dr. Max Donelan walks down many different scientific paths. In fact, walking is something he would like to help more people be able to do. While most healthy people find walking a simple matter, many individuals who suffer from paralysis due to a stroke find that any kind of walking can be one step too far. A stroke is a medical condition that occurs when a blood vessel in the brain leaks. This leakage of blood causes brain and nerve damage. For example, the damage can make it difficult to use the muscles on one side of the body while the other side is not affected at all. A person who has had a stroke may be able to walk but may find that he or she needs to use much more energy than a healthy person to do the same amount of walking. Dr. Donelan is working to find out why. Dr. Donelan and his colleagues at Simon Fraser University in British Columbia are studying the science behind the way healthy people walk. They will use the results of their studies to design devices and strategies to help patients use energy efficiently and regain as much mobility as possible. Even healthy people may benefit from his research. In studying the energy requirements involved with walking, Dr. Donelan’s team has come up with a device that is able to capture energy that is generated when a person walks (Figure 11.47). His device assists the movement of leg muscles while generating electricity at the same time. This is called “harvesting” energy. Harvesting usually refers to gathering in crops like grains or vegetables when they are ripe. In this case, the crop is energy!
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Figure 11.47 Dr. Donelan watches his device in use. It is strapped to the knee of this walker. For every minute of walking you do, the device harvests enough electrical energy to power a cell phone for about 30 minutes.
Dr. Donelan’s team is working to design an energy harvester that is lightweight, slim, and barely noticeable when worn. Being able to produce your own electricity is useful to people in locations where a constant electrical power supply is not available, such as hikers and emergency crews. In the field of energy efficiency, Dr. Donelan is clearly a step ahead.
Questions 1. What does it mean to “harvest” energy? 2. ScienceSource Research to find out what possible applications a human-powered energy harvesting device could have in one of the following fields: • medicine • public safety • the military
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Science in My FUTURE
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Line Installers and Repairers
Are you ready for a career challenge? Suppose your job description included climbing a telephone pole at night during a snowstorm when the power was out — in fact, you would be climbing the pole because the power was out? Electrical energy is an essential part of our society, and waiting for a storm to end is not usually an option when the power grid goes down. Line installers and repairers are sent out often during a summer lightning storm or a winter freeze-up to keep electricity flowing to homes and businesses (Figure 11.48). As a line installer, you would do more than make sure the lines were properly connected and repaired. Line installing and repair includes working with electronics and telecommunications, such as telephone, Internet, and cable television lines. New construction, which involves putting up poles or burying cables, means you are likely to use a variety of equipment, such as diggers, trench makers and tunnelling machines. Although machines would help you lift and carry, you would need to be strong and physically fit. Climbing to high places and working with high voltage carry a definite risk, so an attitude of being careful and working safely is essential. You might set up service in homes for customers, so good people skills are also an asset. For a career as a line installer and repairer, high school completion that includes algebra and trigonometry is an asset, as are the kinds of practical skills learned in shop classes. Community colleges and technical schools often offer programs in electricity, electronics, and telecommunications. These programs frequently partner with companies in the local community to offer hands-on field work.
Figure 11.48 A line installer needs a good understanding of electrical safety.
Even our increasingly wirelessly connected world, we will still need tough, smart, cautious, and strong individuals to keep the grid working properly.
Questions 1. List four qualities that would be an asset for a person interested in work as a line installer or repairer. 2. ScienceSource There are many careers related to electrical technologies, including electricians, power plant operators, and radio and telecommunications equipment installers and repairers. Select one of these or another related field, and summarize what the job involves, the education and training needed, and one aspect of the job that is particularly interesting to you.
Current electricity is the continuous flow of electrons in a closed circuit.
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11 CHAPTER REVIEW ACHIEVEMENT CHART CATEGORIES t Thinking and investigation k Knowledge and understanding c Communication
7. Assume that each resistor in a circuit is of a different value. What type of circuit does each of the following statements describe: series or parallel? k
a Application
Key Concept Review
(a) The voltage is the same across every resistor.
3.0 A
(b) The voltage varies across each resistor.
4.0 V
(c) The current varies through each resistor. (d) The current remains constant throughout the whole circuit.
V1
9.0 V A1
8. A current of 1.5 A flows through a 30-⍀ resistor that is connected across a battery. Find the voltage of the battery. a
Question 1
1. (a) Is the circuit above a series circuit or a parallel circuit? k (b) List all the parts of the circuit above.
9. A 120-V outlet has an appliance that draws 10 A connected to it. What is the resistance of the appliance? a
k
(c) What is the voltage at V1 in the circuit above? k (d) What is the current at A1 in the circuit above? k 2. Draw a circuit diagram of a circuit that includes a battery, an ammeter, and a light bulb with a voltmeter, all properly connected together. c
(c) 650 mA = ____ A 11. (a) What is the value of a resistor that transforms 2.0 mA of current when it is connected to a 6.0-V battery? a (b) Reformulate question (a) twice. In the first question, make voltage the unknown. In the second question, make current the unknown. a
4. (a) What happens to all light bulbs in a series circuit when one burns out? k (b) How does the situation change when the lights are hooked up in parallel? k
Connect Your Understanding
5. Are circuits in a home connected in series, in parallel, or in combinations? Explain your answer, using examples of actual rooms in your home. k
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(a) 1.6 MV = ____ V (b) 1500 W = ____ kW
3. How is a parallel circuit different from a series circuit? k
6. What is the difference between an open circuit, a closed circuit, and a short circuit?
10. Copy and convert each of the following units in your notebook: a
12. The word “circuit” means a complete path. Draw and label a real-life, non-electric example of: c (a) a series circuit
k
(b) a parallel circuit
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13. Explain the reasons for each of these safety rules. a (a) Do not poke a knife into a plugged-in toaster to clear out bread crumbs.
15. What are two ways you could increase current in a circuit? t 16. Why does an electrical cord on a lamp not heat up when the light bulb filament does?
(b) Avoid using an extension cord that is thinner than the cord you are attaching to it. (c) When disconnecting an appliance, pull the plug, not the cord. (d) Do not plug many electrical cords into one outlet.
t
17. You want to find the value of an unlabelled resistor. You have a voltmeter, an ammeter, wires, and a battery. How could you find the value of the resistor accurately? t
Reflection 18. (a) What do you think is the most useful information you learned in Chapter 11? Why? c
(e) Do not use a kite, stick, pole, etc. close to an overhead wire. (f) Make sure your hands are dry before touching any electrical device, cord, plug, or socket.
(b) How might you put your understanding of this information to practical use? c
(g) Never use a frayed electrical cord.
After Reading
14. (a) What is dangerous about the situation shown in the picture below? a (b) What should the worker do to be safer?
Reflect and Evaluate a
(c) The drill is plugged into the wall with a three-prong plug. How does the third prong on the plug act as a safety mechanism? k
With a partner, list all the ways that this chapter supports understanding of unfamiliar terms. Revisit your personal list of terms and definitions. Which terms are now more familiar to you? Which terms might you need to review? What strategies will best help you to review those terms? Create two study goals for this chapter based on your understanding of terms.
Unit Task Link In this chapter, you set up series and parallel electric circuits that could light one or more light bulbs. An electrical grid composed of several generating stations and a number of communities is a complex electrical circuit. However, many of the basic principles you have learned about simple circuits apply to it. Consider how series and parallel circuits might be used to supply electricity from two generating stations to three communities. Sketch a simple circuit that would connect all three communities to both generating stations so that each community has a reliable source of electricity. Question 14 Current electricity is the continuous flow of electrons in a closed circuit.
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We can reduce our electrical energy consumption and use renewable energy resources to produce electrical energy.
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Skills You Will Use Wind turbines can share the land with crops or grazing animals. A number of wind turbines are often connected together in “wind farms” to produce electrical energy.
In this chapter, you will: • determine the energy consumption and operating costs of various appliances • calculate the efficiency of an energy converter
Concepts You Will Learn In this chapter, you will: • assess social, economic, and environmental effects of producing electricity from renewable and non-renewable sources • produce a plan of action to reduce electrical energy consumption at home and outline the responsibilities of various groups in this project
Why It Is Important We are using up non-renewable resources more rapidly than ever before to generate electricity. Now is the time to change this cycle. Your knowledge of electricity can help you make intelligent choices and understand complicated debates about global energy issues.
Before Writing Get Your Reader’s Attention Good writers want you to be interested in what they have to say. They often use the opening sentence in a paragraph as a hook to get you reading further. Survey the first paragraph under each main subheading in chapter 12, and decide which one best grabs your attention.
Key Terms • efficiency • hydroelectricity • kilowatt-hours • non-renewable resources • renewable resources • sustainability • thermoelectric generating plant • thermonuclear
We can reduce our electrical energy consumption and use renewable energy resources to produce electrical energy.
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Renewable and Non-Renewable Energy Resources for Generating Electricity
12.1
Here is a summary of what you will learn in this section: • Electrical generators transform the energy of motion into an electric current. • Most electricity generated in Canada is from hydroelectric or thermoelectric sources. • Other energy sources include biomass, geothermal energy, sunlight, wind, and tides. • There are both renewable and non-renewable energy sources. • Every energy source has both pros and cons. • We need to move toward sustainability in our use of resources. Figure 12.1 Students in Elliot Lake helped install solar energy panels on their school for generating electricity.
Local Solutions to Generating Electricity
N
Elliot Lake
Thunder Bay
0
50 100 km
Sudbury
Sault Ste. Marie
Ottawa Toronto
Windsor
Figure 12.2 Location of the town of
Elliot Lake
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When you turn on the light in your bedroom, you are using electricity that was generated far from your home. A large hydroelectric dam, a coal-burning generating plant, or a nuclear generating plant is probably the source of your electricity. In some areas of Ontario, the source is wind farms made up of giant wind turbines. To build a hydroelectric dam or enough wind turbines to generate electrical energy for a large number of people requires a huge investment in money, people, and equipment. Usually, governments and businesses build these large-scale projects. Coal and oil are non-renewable resources. A non-renewable resource is one that cannot be replaced once it is used up. However, in the past 10 years, governments have invested small-scale projects that use other sources of energy, such as the Sun, to generate electrical energy. The Sun and the wind are renewable resources. A renewable resource is one that can be reused or replaced. In some parts of Ontario and elsewhere in Canada, renewable energy sources can be a practical alternative to non-renewable
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resources for generating electrical energy to meet specific needs in communities. Elliot Lake Secondary School is one example of a small renewable energy project (Figure 12.1). Students at the school proposed to the government that they would place 12 solar panels and a wind turbine on the roof of their school. They pointed out that the electricity generated from these two energy sources would help provide electricity to the school. The project also supported the community of Elliot Lake’s program to reduce its dependence on nonrenewable energy sources such as coal and oil (Figure 12.2). Impressed with the students’ ideas, the government of Ontario awarded them a $50 000 grant. Figure 12.1 shows students at the school installing solar panels at the school. Now the students also have work experience related to installing solar panels and wind turbines. All over Ontario and Canada, communities are developing small-scale projects to produce electrical energy using renewable energy methods (Figure 12.3).
Figure 12.3 The GreenWorks Building at the Kortright Conservation Centre in Toronto generates electricity using solar energy. (© Toronto and Region Conservation, all rights reserved)
D25 Quick Lab Renewable Energy Projects in Your Community Renewable energy projects can be found all over Ontario. Using print and electronic resources, you and your classmates will learn about examples of these projects in your community.
Purpose To identify and describe the function of renewable energy projects in your community
Materials & Equipment • information summaries about renewable energy projects
2. With a partner or small group, select one project to work on. 3. Create a summary of the key features of the project — type of technology used, reason for the project, costs, and value to users and the community. 4. Present your findings to the class.
Questions 5. How many different kinds of renewable methods for generating electricity did you discover?
Procedure
6. Are some methods of generating electricity more common than others? Why do you think this is the case?
1. Your teacher will provide summaries of projects using renewable resources for generating electrical energy in your area or elsewhere in the province.
7. What do you think is one reason there are not more renewable energy projects in your community?
We can reduce our electrical energy consumption and use renewable energy resources to produce electrical energy.
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Generating Electricity
Figure 12.4 Michael Faraday (1791–1867)
W O R D S M AT T E R
A turbine converts steam or moving water to mechanical energy using paddles or fins or even buckets. The word “turbine” comes from the Latin turbo, meaning spinning top or whirlwind.
In 1831, an English chemist and physicist named Michael Faraday made an electrical discovery that changed the world (Figure 12.4). Faraday introduced a way to generate a steady supply of large amounts of electricity. He demonstrated that an electric current can be generated by moving a conducting wire through a magnetic field, a process called electromagnetic induction. We use electromagnetic induction today to generate electricity in large-scale generators (Figure 12.5). Most generators do the same job: they transform the energy of motion into an electric current. The magnets inside a generator are rotated by a turbine, which is a machine that uses the flow of a fluid to turn a shaft. The magnets spin coils of copper wire. This pulls electrons away from their atoms and creates a current flowing in the copper wire. The current is sent through transmission lines to reach cities and towns. The web of interconnections between generating stations, substations, and users is called an energy grid or a distribution grid (Figure 12.6). Generating electricity starts with a spinning turbine and ends up at your wall socket. But where does the energy come from to spin the turbine?
Figure 12.5 The electricity we use in our homes and schools is produced by massive coils of wire rotating between magnets in huge generators, like this one in Nanticoke, Ontario.
transmission line
generating station
underground power wires substation
Figure 12.6 An electric power grid transfers energy from the generating stations to the users. The whole grid is a complete circuit.
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Using Water Power to Generate Electricity Most electricity generated in Canada is hydroelectricity, which means it is generated by harnessing the power of flowing water. Some hydroelectric stations in smaller communities use fast-flowing rivers to turn their turbines. Other hydroelectric stations, such as the ones at Niagara Falls, use the flow from a waterfall to turn their turbines (Figure 12.7). Most communities do not have a waterfall, so a dam may be built across a river to store water in a reservoir. The water is then directed through a channel called a penstock to a turbine with ridges around it (Figure 12.8). The water turns the turbine, which is connected to a generator.
During Writing Show What You Know As a writer, you want to convince a reader that you know your topic. Add details, use facts, and present evidence to demonstrate your knowledge. W O R D S M AT T E R
The prefix “hydro-” comes from the Greek word hudor, which means water.
Figure 12.7 The Sir Adam Beck Generating Station at Niagara Falls generator transformer
water flow
penstock
turbine
Figure 12.8 In a hydroelectric generating station, water flows through a penstock. As it flows past the turbine, it causes the turbine to turn. The turning turbine is connected to the generator. The generator converts the energy from the turning motion of the turbine to electrical energy. We can reduce our electrical energy consumption and use renewable energy resources to produce electrical energy.
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The combining forms “therm-” and “thermo-” are from the Greek word for heat.
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Using Heat to Generate Electricity If there are no waterfalls or rivers in your area, what mechanical force can be used to turn the turbines? One answer is steam. In many areas, thermoelectric generating plants use a fuel such as coal or biomass to heat water to create high-pressure steam.
Fossil Fuels Coal, oil, and natural gas are fossil fuels, which means they were produced from the organic matter of organisms that lived millions of years ago. A fossil fuel, usually coal, is burned in a generator to boil water. The steam is kept under great pressure in pipes, which allows it to reach higher temperatures than normal. The high-pressure steam strikes and pushes the blades on the turbine (Figure 12.9).
coal in combustion chamber
cooling tower
condenser
water exhaust steam high-pressure steam
turbine
generator
transformer
Figure 12.9 A coal-fired generating station
Biomass
Figure 12.10 Corn husks are an example of biomass that is burned to boil water to make steam to turn a turbine.
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Biomass is organic material made up of plant and animal waste. Examples of biomass include wood, peat, straw, nut shells, sewage, and corn husks (Figure 12.10). In a biomass system, the organic waste decomposes to produce a gas called methane. The methane gas can be burned to boil water to make steam. The most common biomass material used today is wood waste from lumber and from pulp and paper industries.
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Nuclear Energy Ontario requires a huge amount of electrical energy. We have a large population and are a major centre of manufacturing. Our electrical energy needs far surpass what hydroelectric and thermoelectric generators supply. Fiftyone percent of our electricity in Ontario is thermonuclear, which means it is produced by heat in nuclear power stations (Figure 12.11). In a nuclear reactor, atoms of a heavy Figure 12.11 The Pickering Nuclear Power Plant is one of three nuclear generating stations in Ontario. element, usually uranium, are split in a chain reaction. This splitting, called nuclear fission, releases an enormous amount of energy. The nuclear fission of just 1 kg of uranium is equivalent to burning about 50 000 kg of coal. The energy released by the fission process is used to heat water to produce steam to turn a turbine.
Geothermal Energy In some places in the world, water is naturally heated by hot rock deep in Earth’s crust and rises to the surface as hot water and steam (Figure 12.12). The energy from this hot water and steam is called geothermal energy. Geothermal energy sources at or near Earth’s surface are hot enough to heat homes and other buildings. For generating electricity, hotter sources are needed. High-temperature geothermal sources are found deep in areas where there is volcanic activity. Iceland has active volcanoes and many hot springs. It uses geothermal energy to produce 19 percent of its electricity. In Canada, geothermal sources hot enough to be used to drive turbines for electricity generation are located in British Columbia. Tests are under way there to determine how to use geothermal sources cost effectively.
Figure 12.12 A hot spring is an example of geothermal energy.
Learning Checkpoint 1. What is a non-renewable resource? 2. What does a generator do? 3. What is a turbine? 4. What source does most of Canada’s electricity come from? 5. What is a fossil fuel?
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Other Energy Sources There are other energy sources that can be used to generate electricity. As different technologies continue to be developed and refined, our ability to use these sources economically increases.
Solar Energy Many people think solar cells are a new technology, but the roots of this invention go back to 1839, when French scientist Edmond Becquerel soaked two metal plates in an electricity-conducting solution. When Becquerel exposed one of the plates to sunlight, he could detect a small potential difference between the plates. He had invented the first solar cell. Scientists now make solar cells using silicon (Figure 12.13). sunlight
A
A Protective cover glass B
B Antireflective coating to let light in and trap it
C D
C Metal contact grid to collect electrons for circuit
E
D Silicon layer to release electrons F
Figure 12.13 A solar cell has
E Silicon layer to absorb electrons F Metal contact grid to collect electrons from circuit
specially treated layers that create current when exposed to sunlight.
Solar modules (several cells connected together) and arrays (several modules) have many uses, including powering calculators, lights in telephone booths, and the International Space Station. A solar farm includes arrays of mirrors that focus sunlight onto a liquid that is heated and used to turn water into steam to drive the turbines (Figure 12.14). One of the world’s largest solar energy projects includes solar farms in Sarnia and Sault Ste. Marie and aims to produce enough electricity for about 9000 homes.
Figure 12.14 The mirrors in this solar array focus heat from the Sun on a container that is part of a system to turn water into steam.
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Wind Energy Wind turbines use the energy of moving air to spin their blades, which are connected to a generator (Figure 12.15). The amount of energy a wind turbine generates depends on how fast the wind is blowing, with approximately 10 km per hour being the minimum for power generation. In Ontario, the wind blows strongly enough, on average, about 20 percent of the time, but in some areas of Canada and the world, winds are stronger and more consistent. Wind energy currently provides about 1 percent of Ontario’s electricity, but it is one of the fastest-growing energy sources in the world.
Tidal Energy Tidal energy uses the energy of the gravitational pull of the Moon. North America’s only tidal power generating station is in Annapolis Royal, in Nova Scotia, where the powerful tides of the Bay of Fundy spin its turbines (Figure 12.16). The station provides enough electricity for about 4500 homes. Tests are under way in British Columbia and Nova Scotia for a promising new technology called a tidal stream generator, which works like an underwater windmill. Other marine energy sources that are being tested include ocean wave energy and ocean thermal energy.
Figure 12.15 A wind farm near Shelburne, Ontario
Figure 12.16 This tidal power station in Nova Scotia generates electricity by using the
energy of the water as it rises and falls in the daily cycle of tides.
We can reduce our electrical energy consumption and use renewable energy resources to produce electrical energy.
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Comparing Methods of Generating Electricity Relative Costs of Electricity Generation Technologies (Canadian cents per kilowatt hour, 2003) 80 70 60 50 40 30 20
wave and marine
geothermal
wind
solar photovoltaic
large hydro
small hydro
micro hydro
landfill gas
biomass
gas
nuclear
0
coal
10
SOURCE: CERI, Relative Costs of Electricity Generation Technologies, September 2006
Figure 12.17 Relative costs of electricity generation technologies
Energy sources for generating electricity can be grouped into two broad categories. Nonrenewable energy sources are sources that are limited and cannot be renewed naturally. Fossil fuels (natural gas, propane, coal, and petroleum) are non-renewable sources, as is uranium. Once these materials are used up, they cannot be replaced. Renewable energy sources are sources that can be replenished by natural processes in a relatively short time, such as sunlight, wind, tides, and waves. Biomass is a renewable source if the trees or other plants that produce it are properly managed. A few of the advantages and disadvantages of using different energy sources are summarized in Table 12.1 and Table 12.2. A comparison of the approximate costs of using each source is shown in Figure 12.17.
Table 12.1 Some Advantages and Disadvantages of Non-Renewable Sources for Electricity Generation
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Source
Some Advantages
Some Disadvantages
Fossil fuels
– Fossil fuel generating stations can quickly adjust to changes in electricity demand. – The technology for using these fuels is already in place.
– The burning of fossil fuels releases pollutants into the atmosphere and directly contributes to global warming. – Mining coal is hazardous to workers and damages the environment.
Nuclear
– Nuclear power is inexpensive to produce. – Nuclear power produces enormous amounts of energy from very little fuel.
– Nuclear waste is poisonous and radioactive and needs to be stored very carefully for hundreds or thousands of years. – Nuclear plants are very costly to construct and to maintain.
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Table 12.2 Some Advantages and Disadvantages of Using Renewable Sources for Electricity Generation Source
Some Advantages
Some Disadvantages
Flowing water (hydroelectricity)
– Large hydroelectric generating stations produce electricity inexpensively. – Reservoirs may be used for flood control, irrigation, drinking water, and recreation. – Small-scale hydroelectric plants using local rivers can be practical for some communities (Figure 12.18).
– There is a huge environmental impact when a dam is constructed, including flooding large areas of land, disruption or destruction of wildlife and fish habitat and migration routes, and displacement of Aboriginal and other communities. – Hydroelectric stations are very expensive to build.
Sunlight
– Solar cell energy is a convenient source of energy for small appliances, such as calculators. – Solar energy is useful in remote areas.
– Solar cell efficiency is low, so many photoelectric cells have to be used, which takes up large areas of land. – Solar energy is the most expensive energy source at present.
Tides
– Once tidal generating stations are built, tidal energy is very inexpensive. – Tides are more predictable than wind or sunlight.
– The environmental impact on marine life in area can be significant, due to changes in water level and water quality. – Tidal energy is suitable for few areas as it requires very high tides.
– Wind energy production does not produce greenhouse gases that contribute to global warming. – Farming and grazing can continue on land where wind turbines are located.
– The wind does not always blow or remain constant. – Wind turbines can present barriers to bird movement, cause bird fatalities due to collisions with turbine blades, and can disturb breeding, wintering, and staging sites.
Wind
Figure 12.18 Small-scale hydroelectric generating stations can be a local source of electrical energy.
Suggested STSE Activity • D26 Decision-Making Analysis Case Study on page 486
Learning Checkpoint 1. What are three applications of solar cells? 2. What does a wind turbine do? 3. What is one of the fastest-growing energy sources in the world? 4. How is electricity generated from tides? 5. How is a renewable energy source different from a non-renewable energy source?
We can reduce our electrical energy consumption and use renewable energy resources to produce electrical energy.
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Electrical Energy Production in Canada
Take It Further Hydrogen may be our fuel of choice in the future. It can be burned like other fuels or converted into electricity in fuel cells. Find out how the most abundant element in the universe can be put to use for our electrical needs. Start your research at ScienceSource.
Canada is the world’s largest producer of hydroelectricity, the fifth-largest producer of electricity in general, and the second-largest exporter of electricity. However, we need to be aware of the environmental implications of using non-renewable resources. As Figure 12.19 shows, a large part of our electricity is generated using non-renewable resources. These resources include coal, uranium (for nuclear energy), oil, and gas. We must decide how to make a transition to using more renewable resources. We need electricity, but we also need to generate it wisely. All of our energy sources are important to Canada because they provide us with flexibility and energy security and help us to become self-sufficient. For example, at one time, Prince Edward Island was completely dependent on outside sources for electricity because it does not have fossil fuels, hydroelectricity, or nuclear power. However, the island now produces 18 percent of its electricity from wind energy and has become the first place in North America to offer a guaranteed price to anyone — even a homeowner — who produces electricity from wind power. In Ontario and across Canada, renewable energy projects for generating electricity are under way or being planned. However, as you can see in Figure 12.19, this type of electricity generation produced only 0.6 percent of our electricity in 2007. It cannot replace our use of non-renewable energy resources for now. To reduce our use of non-renewable resources, we have to find ways to use less electricity through technology and changing our usage habits. Electricity Generated in Canada 2007 14.6
4.0
0.6 60.1
20.7
hydro
nuclear
coal
oil and gas
Figure 12.19 Methods of electricity generation in Canada
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A Sustainable Choice Choosing the right methods for generating electricity means finding sustainable solutions. Sustainability means using resources at a rate that can be maintained indefinitely. If we do not achieve sustainable energy use, future generations in Ontario may not be able to support themselves. A sustainable approach sometimes requires a different way of using resources. Sustainability may mean no longer using nonrenewable resources because they cannot be maintained indefinitely. In the past, fossil fuels were used up as quickly as possible to earn money and satisfy consumer demand. We need to use our resources in a way that makes them available over a longer period of time. With renewable energy methods, resources such as solar energy and wind are available indefinitely. Figure 12.20 shows the main methods worldwide for generating electricity in 2007. Coal, oil, and gas account for 66.6 percent of electricity production. These three methods are using non-renewable resources. The other three methods, hydro, nuclear, and other account, for 33.4 percent of the production. Hydro and other methods use renewable energy sources. We may never be able to achieve complete sustainability, but the decisions we make personally and as a society can move us closer to this goal. An example of a personal decision would be to turn off the lights in your bedroom or classroom if you are the last person out of the room. This small action would save on electrical use. As you get older, you may make bigger decisions such as adding solar panels to a house you live in (Figure 12.21). Decisions such as these demonstrate you are keeping the goal of sustainability in mind.
Suggested Activity • D27 Decision-Making Analysis on page 488
Figure 12.21 The people who live in this house are using solar panels to heat their water. This reduces their electricity use.
Electricity Generated Worldwide in 2007 2.2 19.7
16.0
40.3
6.6
15.2 hydro
nuclear
gas
coal
oil
other
Figure 12.20 How the world generates electricity. This graph could become very different during your lifetime. We can reduce our electrical energy consumption and use renewable energy resources to produce electrical energy.
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CASE STUDY
D26
STSE Decision-Making Analysis
SKILLS YOU WILL USE Skills Reference 4
■ ■
Drawing conclusions Justifying conclusions
Three Gorges: Potential Disaster or Good Choice? Issue The Three Gorges Dam on the Yangtze River in China is the world’s largest hydroelectric generating station (Figure 12.22). The dam is 2.3 km long and 101 m high, with a reservoir that floods 632 km2 of land. The dam provides electricity to nine provinces in China. Is the electricity the dam provides worth the problems it causes?
Background Information Two students, Bassim and Kara, have been researching the Three Gorges Dam to find out the costs and benefits of this huge hydroelectric project. The more they have learned about the dam, the more they are convinced of their own viewpoints. Kara’s Viewpoint: In Favour of the Dam The Three Gorges Dam is a good example of China’s commitment to using renewable resources to increase its production of electricity. • Until recently, 82 percent of China’s electricity was generated in coal-burning stations. Three Gorges could allow China to reduce coal consumption by 31 million tonnes per year,
so millions of tonnes of greenhouse gases and pollutants will not be created. • China plans to increase electricity from renewable resources from 7.2 percent to 15 percent by 2020. A series of smaller dams being built on the Yangtze will reduce silt and help to maximize the efficiency of the Three Gorges Dam. • China is taking steps to minimize environmental damage. Billions of dollars already have been spent in water clean-up projects and in preventing landslides. • The potential of the dam to prevent or reduce flooding for the millions of residents downstream means that far more lives and property can be saved than were lost due to the building of the dam. • As well as providing flood control, the dam has improved navigation so that large ships can travel farther upriver, improving the economy of the area. • The people of China need more electricity, and they have made a good choice in using renewable sources.
Figure 12.22 The Three Gorges Dam provides electricity to nine Chinese provinces. However, it has negatively affected
millions of people who used to live where its reservoir now lies.
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STSE Decision-Making Analysis (continued)
Bassim’s Viewpoint: Opposed to the Dam The Three Gorges Dam is a social and environmental disaster and should not have been built. Millions of people live downstream from the dam and are in danger if the dam should ever fail. • Over 1.2 million people were forced out of their homes so that their land could be flooded by the reservoir. Many of these people have had to move a second time due to an increase in landslides caused by filling the reservoir. Four million people are being encouraged to move before 2020. • As well as submerging homes and more than 1300 archaeological sites, the reservoir also submerged factories, mines, and waste dumps. All the chemicals and other waste at those sites now contribute to the pollution of the reservoir. Also, only about 65 percent of the water flowing into the reservoir is treated, adding to the pollution and the possibility of diseases carried by water. • The dam sits on a seismic fault, and there is danger of increased earthquakes and landslides. Much of the silt that the river used to carry all the way down to the coast now settles in the reservoir and reduces the effectiveness of the dam. Cities such as Shanghai that are far downstream no longer have silt deposited to help build up their banks and may soon suffer from huge erosion problems.
Figure 12.24 The Yangtze River dolphin has become extinct since the construction of the dam.
• The changes in water flow affect downstream fish populations. These changes have resulted in the extinction of the Yangtze River dolphin and may be harming the populations of critically endangered Siberian cranes (Figures 12.23 and 12.24).
Analyze and Evaluate 1. Read both students’ viewpoints. Which student do you think presents a stronger case? Why? 2. Choose one of the following roles. Prepare a presentation from that perspective, defending a possible course of action for an international energy conference. • relocated villager • wildlife expert • government official • industrialist • Shanghai citizen • geologist • citizen of province receiving electricity from the dam
Skill Practice 3. What is your conclusion about whether the electricity the dam provides is worth the problems it causes? Explain and justify your conclusion. Figure 12.23 Siberian cranes are endangered birds that have been negatively affected by the dam’s construction.
We can reduce our electrical energy consumption and use renewable energy resources to produce electrical energy.
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D27 Decision-Making Analysis
Skills Reference 4
Producing Electricity in an Ontario Community Issue Environmentally, it makes sense to close coalburning generating stations. Open-pit mining of coal scars the landscape. Burning coal releases pollutants into the air that cause acid rain. However, it does not make sense economically for now. The huge amount of power lost to the grid would have to be replaced. The job losses would have a devastating effect on local economies. What recommendations would you make to a community that relies on burning coal for electricity generation?
Background Information Every method of electricity generation has advantages and disadvantages. For example, the operation of wind farms along Lake Huron produces electricity from a renewable source (Figure 12.25). This reduces dependence on non-renewable sources of electricity. However, the wind farms produce noise and visual pollution, affect local animal life, and reduce the amount of land available for agriculture. Your goal is to identify some of the social, economic, and environmental implications of electricity production in a community in Ontario. You will research the social, economic, and environmental effects of one method of electricity generation that is different from the main method
■
■
Gathering, organizing, and recording relevant information from research Using appropriate formats to communicate results
being used now in the community. You will also compare your proposed method to the present method. Then, you will make a presentation in support of your choice.
Analyze and Evaluate 1. Meet with your group members to discuss the role each member will play in researching, formatting, and presenting your information. Create a list of questions and key words that will help direct your research. 2. Web 2.0 Work together to decide on a format for presenting your research. Develop your group’s research as a Wiki, a presentation, a video, or a podcast. For support, go to ScienceSource. 3. ScienceSource Conduct your research online. Copy and complete the chart below as part of your research. Present Method
Proposed Method
Economic - cost of producing electricity per kW•h Environmental - hazardous substances used or produced and their effects on surrounding ecosystem Social - effects of emissions on human health
4. What percentage of the energy produced should come from your proposed method? Explain.
Skill Practice 5. (a) What challenges did you have in researching the information you needed? (b) How did you overcome the challenges? Figure 12.25 Wind farms have to be placed where the wind is strong and steady enough to generate electricity cost effectively.
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12.1 CHECK and REFLECT Key Concept Review
Connect Your Understanding
1. What is the function of a generator? 2. What does “hydroelectricity” mean? 3. What are four methods of generating electricity that use heat? 4. Explain how a solar cell produces electricity. 5. What are two different ways to make use of the tides to generate electricity? 6. (a) What is the difference between renewable and non-renewable sources of energy? (b) Create a chart that categorizes different energy sources as either renewable or non-renewable. 7. (a) What is the source of most of the electricity generated in Ontario? (b) What is the source of most of the electricity generated in Canada? 8. The photos below show the type of solar cells that are installed on the “wings” of the International Space Station. Why are solar cells used to generate electricity on spacecraft?
9. Compare the generation of electricity using coal with hydroelectric generation. (a) How are the two methods similar? (b) How are the two methods different? 10. Why does an electrical generating station not use batteries to generate electricity? 11. Suppose that residents of a remote community in northern Ontario decide to use wood as their primary energy source for heating the boiler of the community’s electrical generator. They cut down all the trees nearby and stockpile the wood, ready for use. (a) What are the advantages and disadvantages of their solution for their energy needs? (b) What recommendations would you make to ensure that this community has a reliable long-term energy supply?
Reflection 12. (a) What information about electricity generation did you learn in this section that you did not know before? (b) What are two questions that you have about electricity generation in Canada? For more questions, go to ScienceSource.
(a)
Question 8 (b)
The International Space Station (a) uses 2500 m2 of solar cells (b) to generate its electricity.
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Reducing Our Electrical Energy Consumption
Here is a summary of what you will learn in this section: • Electrical energy consumption is usually measured in kilowatthours (kW•h). • Efficiency is the ratio of useful energy that comes out of a device to the total energy that went in. • The EnerGuide label shows how much energy an appliance will use in a month of average use. • Energy Star appliances are the most efficient appliances in their class. • Energy conservation begins at home.
Figure 12.26 Consider how many times a day and how many different ways you use electricity.
The Cost of Electricity Every method of generating electricity comes at a cost. There is an environmental cost, which affects the world you live in, and there is an economic cost, which gets passed on to you, the consumer. Each time you plug in an appliance, turn on a switch, or use electricity in any way, you are using precious resources and spending money (Figure 12.26). You can take steps to make better choices about how you use electricity. The first step is to understand where, when, and how you use electricity. Most homes and apartment buildings have an electricity meter that tracks how much electricity is drawn from the energy grid. Older models of electricity meters have a turning disk with a black band (Figure 12.27). The more electricity you have turned on in the house, the faster the disk turns. The energy used is calculated monthly or bi-monthly by reading a set of dials above the disk.
Figure 12.27 Older-style meters have to be read manually.
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Newer digital meters, called smart meters, are being installed across Ontario as part of a major energy conservation effort. The smart meters record electricity consumption hour by hour and send the information directly to the utility or electric company (Figure 12.28). Electricity costs are then calculated according to time of use, which includes time of day, weekdays versus weekends, and season. The cost of electricity is higher during peak times, which are the busiest times of the day. You can save money on your electricity bill by moving activities that are energy-intensive to off-peak hours. You can help save resources by reducing your use of electricity at all times of the day.
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Figure 12.28 Smart meters use wireless and other technologies to send information directly to the utility.
D28 Quick Lab Analyzing Home Electrical Use Purpose
Clock radio
Dishwasher
Number of devices
3
1
Time of day
all
all
1. Create a list of all devices in your home that use electricity provided by the electric company or a home generator. Do not include anything powered by batteries, but do include battery chargers.
Day(s) of week
all
all
Season
all
all
2. Make a table using the rows shown on the right but without including the example devices. Add enough columns for all the electrical devices in your home. Give your table a title.
Weekly usage (h) per device
168
7
Total weekly usage of devices (h)
504
7
3. Complete the table by estimating average usage and predicting the electricity requirements.
Electricity requirements per use (low, medium, high)
low
high
To categorize the use of electrical devices in your home
Procedure
Questions 4. Which device usages do you think you could reduce? 5. What did this activity show you about your electricity usage that you did not realize before?
We can reduce our electrical energy consumption and use renewable energy resources to produce electrical energy.
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Electrical Energy Consumption The electrical energy consumption for a household is the amount of electrical energy used, usually measured in kilowatt-hours. A kilowatt-hour (kW•h) is equivalent to the use of one kilowatt in one hour. For example, if the energy (E) used by a microwave oven is 0.8 kW and the oven is turned on for half an hour, the electrical energy used is: E = 0.8 kW × 0.5 h = 0.4 kW•h
Figure 12.29 A utility bill shows the amount of electricity used in kilowatt-hours.
W O R D S M AT T E R
The watt is named in honour of the Scottish inventor and engineer James Watt (1736–1819), whose improvements to the steam engine changed the world. The joule is named in honour of English physicist James Prescott Joule (1818–1889), who studied the nature of heat and current through a resistor.
One kilowatt (kW) equals 1000 watts (W). A watt is equal to one joule per second. It does not take long for common electrical devices to consume a large number of joules. For this reason, the kilowatt-hour is often used as a unit for energy. To calculate the cost of using an electrical device, you can multiply the energy consumed in kW•h by the cost per kW•h. In the microwave example above, the consumption of 0.4 kW•h at a cost of 8 cents per kW•h equals 3.2 cents. It may not sound like much, but remember that this was only one event over a half-hour time period. There is also an electricity delivery charge and taxes on top of the actual energy charge (Figure 12.29).
Learning Checkpoint 1. Copy and complete this chart in your notebook. Give your chart a title. Calculate the cost of using each appliance over the course of a year. Use a utility charge of 8.5 cents per kW•h.
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Annual Energy Consumption (kW•h)
Appliance
Average Use (hours per day)
Vacuum cleaner
0.1
38
Hair dryer
0.25
100
Computer
4.0
520
Central air conditioning
12 (60 days/year)
1500
Annual Cost ($ per year)
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Calculating Percent Efficiency
During Writing
If you have ever accidentally touched a light bulb when it was lit, you know that it gets very hot (Figure 12.30). An incandescent light bulb uses only about 5 percent of its input energy to create light and converts over 95 percent of its input energy into heat. Compact fluorescent lights transform about 20 percent of their energy input into light, so they are more efficient than incandescent light bulbs.
Organize for Impact
5 J light energy
95 J heat
100 J electric energy
Figure 12.30 Most of the energy transformed by a light bulb is radiated as heat.
The efficiency of a device is the ratio of the useful energy that comes out of the device to the total energy that went in. The more input energy that a device converts into usable output energy, the more efficient the device is. Efficiency is usually calculated as a percentage. percent efficiency =
Suggested Activities • D30 Quick Lab on page 496 D31 Quick Lab on page 497
Eout × 100% Ein
Example Problem 12.1 Suppose a light bulb uses 780 J of input energy to produce 31 J of light energy. What is its percent efficiency? Given Input energy = 780 J Output energy = 31 J Required Percent efficiency = ? Analysis and Solution Choose the correct equation. Percent efficiency = Eout × 100% Ein
Substitute the values and their units. Solve the problem. Percent efficiency = 31 J × 100% Paraphrase
When persuasion is the goal, good writers like to create impact at the beginning and end of their piece of writing or presentation. Watch television commercials, especially public service announcements, and note the methods for creating a powerful opener and a convincing closer for your presentation.
780 J
% = 4.0%
The efficiency of the light bulb is 4.0 percent.
Practice Problems
1. A car produces 27.5 kJ of useful output energy from 125 kJ of fuel. What is the car’s percent efficiency? 2. A fluorescent light produces 3.6 kJ of useful light energy from 21 kJ of input energy. What is its percent efficiency? 3. A new high-efficiency brushless motor designed for electric-powered vehicles has an input energy of 75 kJ and an output energy of 72 kJ. What is its percent efficiency?
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Comparing Efficiency By comparing the efficiency of different devices, we can judge both their energy cost and their environmental impact. For example, a front-loading clothes washing machine uses much less electricity, washes more clothes per load, and uses less water than a top-loading washer. This reduces the energy needed to pump and heat water for laundry. Another example of improved efficiency is the refrigerator shown in Figure 12.31.
thin fiberglass insulation
thick polystyrene insulation
low-efficiency compressor motor
high-efficiency compressor motor 1970s mini-refrigerator
Modern full-size refrigerator
Figure 12.31 The energy used to run a mini-refrigerator in the 1970s can run a full-size refrigerator today. In the last 25 years, refrigerator efficiency has increased 300 percent.
Read the Label Sometimes, older equipment can be modified or adjusted to increase efficiency. But when it is time to buy a new appliance, there are labels that can help you make an informed choice. All large appliances such as stoves, dishwashers, refrigerators, washers, and dryers have an EnerGuide label. This label states how much energy that appliance will use in a month or year of average use, as shown at (a) in Figure 12.32. It allows you to compare the energy consumption of different brands and models. The arrow (b) on the long shaded bar on the label below the rating shows the efficiency range of the appliance. If an appliance displays the Energy Star symbol (c), it is one of the most efficient appliances in its class.
(a) (b)
(c)
Figure 12.32 You can use the EnerGuide label to compare appliances and
determine which are more efficient. For example, you could compare refrigerators that have the same volume but are made by different manufacturers. 494
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How Off Is Off? Suppose you finish using your computer and turn it off before leaving your room. As you walk by the living room, you notice the television has been left on even though no one is watching it, so you turn it off as well. These are good, energy-conserving actions, but have you really turned those appliances off? If you look more closely, you may notice little lights still glowing on transformers and other devices (Figure 12.33). These machines are in a “standby” mode so that they will restart quickly when you switch them on. Many small appliances, such as computers, stereos, televisions, DVD players, and answering machines, still use electrical energy even when they are turned off.
Figure 12.33 If the standby light is on, electricity is being consumed.
Energy Conservation Begins at Home You can make a plan to reduce the use of electricity in your home. Asking questions is an excellent start. For example: • Are lights being left on in rooms that are not being used? • Is the clothes dryer being used for small loads like one shirt? • Is the hot water running continuously while the dishes are being done? • Is a lot of hot water being used for long showers? • Are incandescent light bulbs being used instead of compact fluorescent bulbs? If we lower our energy demands, we reduce the need to build more generating stations and we avoid greater impact on the environment and major construction costs. Your own personal action plan to reduce energy consumption will make a difference. Reusing and recycling materials, conserving energy, and learning to live responsibly in harmony with our environment are key actions for living in a sustainable way.
Take It Further Many people have contributed to our understanding of electricity. Research one of the following names to find out when these people lived and what they contributed: Benjamin Franklin, Luigi Galvani, Charles-Augustin de Coulomb, Alessandro Volta, James Watt, André-Marie Ampère, Georg Ohm, Robert Millikan, Michael Faraday, Thomas Edison, Nikola Tesla, George Westinghouse. Begin your research at ScienceSource.
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STSE Science, Technology, Society, and the Environment
A Self-Sufficient Energy Community The 4300 people of Freiamt, a community in the southern part of Germany, decided that they wanted to own and control their own electricity generation. The community added rooftop solar systems to homes, barns, and garages and installed wind turbines. The community also has small-scale hydro and biomass generating stations. Some of the generators are jointly owned; others are privately owned.
The community’s electricity generation has been so successful that each year there is a surplus of about three million kilowatt hours of energy that is sold to Germany’s national energy grid.
1. How could you adapt the community’s plan to make it suit your community? 2. What do you think are the main points about Freiamt’s plan that you could use to gain community support?
D30 Quick Lab Electricity in Your Home Purpose To discover the pattern of electrical energy consumption in your home
Materials & Equipment • 1 year’s worth of electrical bills for your home or sample bills supplied by your teacher
Procedure 1. Before starting, predict what months are the peak periods of electrical energy consumption in your home. 2. Create a table with the following column headings. Give your table a title. Actual Electricity Usage (kW•h) Adjusted Usage (kW•h) Cost of Electricity ($) Delivery Charge ($) Other Charges ($) Total Charges
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3. For each bill, break down the different costs and add them to your chart. 4. Total the charges.
Questions 5. (a) What does the category “Other Charges ($)” include? (b) What does “Adjusted Usage (kW•h)” mean? 6. (a) During which time periods is your household using electricity the most? (b) Why might this be? (c) How does this time period compare with your prediction from step 1? 7. How would you change the bill to make it easier to understand? 8. Write a summary paragraph explaining the pattern of electricity usage in your household.
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DI Key Activity
D31 Quick Lab Marketing Compact Fluorescent Light Bulbs As part of an effort to reduce energy use, the province of Ontario has banned the sale of inefficient incandescent bulbs, beginning in 2012.
Purpose To create an effective marketing tool for compact fluorescent light bulbs
Procedure 1. You and your partner have been hired by a public relations firm to help with the marketing campaign for compact fluorescent light bulbs (Figure 12.34). 2. Decide on the format you will use as part of the marketing campaign. You might design a brochure, make a poster, create a Web page, prepare computer slides, perform a rap song, create a skit, or choose another format as approved by your teacher. 3. Read the following summary of points about both incandescent and compact fluorescent light bulbs. Consider both the pros and the cons in deciding how to reach your audience. Bulb
Pros
Cons
Compact fluorescent
- produces about four times more light than incandescent using the same amount of energy
- much more expensive to make than incandescent - contains mercury
Incandescent
- less expensive to make than fluorescent
- does not last as long as fluorescent - is much less efficient than compact fluorescent bulbs
4. ScienceSource Conduct research so you can make a strong case in favour of compact fluorescent light bulbs. You may want to research Ontario Power Generation, the Ontario Ministry of the Environment, Natural Resources Canada, and environmental groups such as the Pembina Institute or the Sierra Club. 5. Outline the roles and responsibilities of various groups, such as government, businesses, and family members, in making a success of the marketing campaign. 6. Look in print materials such as magazines, newspapers, and books for information on the real costs of using various lighting options. 7. Prepare and refine your presentation. You may wish to present your information to friends or family members and ask for their feedback. 8. Share your presentation with the class.
Questions 9. On the basis of your research, what do you think is the most important advantage of compact fluorescent bulbs? 10. On the basis of your research, what do you think is the greatest disadvantage of compact fluorescent light bulbs?
Figure 12.34 Compact fluorescent bulbs (left) are replacing incandescent bulbs (right) because they use less energy.
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12.2 CHECK and REFLECT Key Concept Review
10. What does an Energy Star symbol on an appliance indicate?
1. What does a smart meter measure? 2. (a) What is electrical energy consumption a measure of? (b) What units are usually used to measure electrical energy consumption? (c) How is electrical energy consumption calculated? Question 10
3. (a) How many watts are in a kilowatt? (b) What does one thousand joules equal? 4. (a) A microwave oven that draws 0.8 kW•h is used for one hour. At a cost of 7.5 cents per kW•h, what is the cost of the microwave’s electrical energy consumption? (b) What is the cost for the microwave if it is used one day for 20 min? (c) What is the cost of using the microwave for 20 min a day for a month of 30 days? 5. What is the term for the ratio of useful energy that comes out of a device to the total energy that went in? 6. What is the formula for calculating percent efficiency? 7. What is the percent efficiency of a light source that uses 12.8 kJ of energy and delivers 4.3 kJ of useful light energy? 8. What information is included on an EnerGuide label? 9. Suppose the standby light on your printer is on even though you have turned the printer off. What does the standby light indicate?
Connect Your Understanding 11. Describe how a smart meter is an improvement over older types of electricity meters. 12. The costs for electricity are higher during peak times. Why do you think this is so? 13. Why are incandescent bulbs regarded as inefficient? 14. Create an EnerGuide label for an appliance with an Energy Star rating. You can use hypothetical values and names of companies. 15. Why should you compare the efficiencies of appliances before making a purchase? 16. How can we reduce the need to build more generating stations?
Reflection 17. (a) How has the information in this section helped to make you a better consumer? (b) How could you use this information to help you decide which electronic device to purchase? For more questions, go to ScienceSource.
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COOL IDEAS f r o m J AY I N G R A M
A Light Show in Your Mouth
Jay Ingram is an experienced science journalist, author of The Daily Planet Book of Cool Ideas, and host of the Daily Planet on Discovery Channel Canada.
Have you ever experienced a chemical light show in your mouth? You might have if you have chewed a wintergreen candy. You can observe the effect if you get some wintergreen candies and a pair of pliers, and sit in a very dark place, like the inside of a closet. Wait about five minutes until your eyes adjust to the darkness, and then crush one of the candies with the pliers (Figure 12.35). You will see an amazing flash of blue-green light! The flash of blue-green light was first described in 17th century Italy. However, the mechanism at work was not understood until several hundred years later. The candy is made of sugar crystals, which are mostly empty space, with the atoms in them rigidly attached to each other. When you bite into the candy, the positive and negative charges in the crystals are separated, and this separation generates an electric potential difference. When enough charge has accumulated, the negatively charged electrons jump across the gaps in the crystals to reunite with the positively charged protons. As the electrons move, some of them collide with the nitrogen atoms in the air. The nitrogen atoms absorb the tremendous energy of the collisions, and then emit blue-green light as they release their energy. All sugar candy emits some light when you crush it. If there is only sugar, the blue light is harder to see, because much of the energy is released as ultraviolet light, which is not visible to humans. That is where the wintergreen comes in. Oil of wintergreen is very good at absorbing ultraviolet light and emitting it as visible blue-green light.
Question 1. Write a summary of this feature. Include a main idea and one relevant point that supports it.
Figure 12.35 A wintergreen candy crushed by pliers in the dark.
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12 CHAPTER REVIEW ACHIEVEMENT CHART CATEGORIES t Thinking and investigation k Knowledge and understanding c Communication
9. How can choosing to use a more efficient appliance benefit the environment? k
a Application
10. Answer the following questions by referring to the EnerGuide label shown below. k
Key Concept Review 1. (a) List two non-renewable sources of energy. k (b) Name an advantage and a disadvantage of using each source. k 2. (a) List four renewable sources of energy. k
(b) Name an advantage and a disadvantage of using each source. k 3. Describe what happens in nuclear fission. k 4. What is sustainability?
k
5. (a) How do you convert watts to kilowatts? k
(b) How do you convert kilojoules to joules? k (c) How many joules are in a watt?
Question 10
k
6. Suppose you bake a potato in a toaster oven that uses 1.2 kW. The oven is turned on for 25 min. How many kilowatt hours did it use? a 7. (a) If a motor uses 22 000 J while converting it to 13 400 J of useful energy, what is its percent efficiency? (b) If a diesel truck produces 47.5 kJ of useful output energy from 125 kJ of diesel fuel, what is its percent efficiency? a 8. Give two reasons for reducing energy waste. k
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(a) What is the energy usage of the rated appliance? (b) Among similar appliances, which is rated most efficient? (c) Is the rated appliance efficient? How do you know? (d) List models similar to the one that is being rated. 11. What does it mean if an appliance has an Energy Star rating? k
Connect Your Understanding 12. Explain why you agree or disagree with the following statement: “A nuclear power plant provides energy using a radioactive source, so a turbine is not needed.” t
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13. A group of Ontario farmers form a cooperative group and build a factory that turns corn into a fuel for generators and cars. Would this energy source be renewable or non-renewable? Explain. t 14. Make a labelled pie chart or circle graph showing how electricity is used in your home. c 15. Is it always a good idea to discard lowefficiency devices? Explain your answer.
Question 20
t
16. (a) If you have a house in the country with a large property, what might you do to help reduce your dependence on the energy grid? t (b) If you live in a mid-size house in the suburbs, what could you do to reduce your utility bill? t (c) If you live in a small apartment in the centre of a city, what could you do to reduce your utility bill? t 17. Choose an electrical device that you use daily. Identify changes you would make to the design of the device to maximize energy savings. Explain the reasons for your choices. Use a labelled diagram as part of your answer. c 18. (a) Create a cartoon that shows at least seven ways that a home loses energy needlessly. c (b) For each example shown, list a way to reduce that energy loss. t 19. What are seven practical ways to reduce electrical energy consumption in your school? t 20. Write a paragraph about the photograph shown at the top of the next column. Include your personal response to the photograph, and explain what the photograph shows about electricity generation. c
Reflection 21. How could you improve the results of your work in the problem-solving and inquiry activities you did in this unit? c
After Writing Reflect and Evaluate With your partner, meet with another pair who made a marketing presentation for fluorescent light bulbs. Provide positive feedback and helpful suggestions about the others’ presentation. How did it hook the audience? Which details, facts, or evidence were most effective in demonstrating knowledge? What were the points that created the greatest impact?
Unit Task Link In this chapter, you have studied different methods of generating electricity and their social, economic, and environmental effects. Your knowledge of electricity can help you work within your community to decide on the best methods of power generation for your region. Think about the sources of energy for your community and whether they are reliable and sustainable. Suggest one form of energy production not being used now that might be an appropriate method for your community. Explain your choice.
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Summary
KEY CONCEPTS
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CHAPTER SUMMARY
Static charges accumulate on surfaces and remain there until given a path to escape.
• Static electric charges • Law of attraction and law of repulsion • Conductors and insulators • Charging by friction • Charging by contact and induction • Using and reducing static charges
• Objects that gain electrons become negatively charged. Objects that lose electrons become positively charged. (10.1) • Objects with like charges repel each other. Objects with unlike charges attract each other. (10.1) • When an object is charged by contact, it takes the same charge as the charging object. (10.2) • When an object is charged by induction, it takes the opposite charge to the charging object. (10.2) • Charged objects attract neutral objects through the process of induction. (10.2) • The principles of electrostatics are used in applications such as photocopying, spray painting, and filtering air. (10.3)
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Current electricity is the continuous flow of electrons in a closed circuit.
• Current electricity
• Electrical circuits provide a complete path for electrons to flow. (11.1)
• Electrical circuits
• Current electricity is the flow of electrons through a conductor in a circuit. (11.1)
• Potential difference • Electric current • Direct current • Alternating current • Resistance • Series circuits and parallel circuits • Ohm’s law (V = IR) • Electrical safety
• Potential difference or voltage (V ) is the difference in electric potential energy between two points in a circuit. (11.1) • Electric current (I ) is a measure of the amount of electric charge that passes by a point in an electric circuit each second. (11.1) • In direct current, electrons flow in one direction. In alternating current, electrons flow back and forth at regular intervals called cycles. (11.1) • Resistance (R ) is the degree to which a substance opposes the flow of electric current through it. (11.1) • Series circuits provide one path for electrons to flow. Parallel circuits provide more than one path for electrons to flow. (11.2) • Ohm’s law states that as long as temperature stays the same, V = IR. (11.3)
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We can reduce our electrical energy consumption and use renewable energy resources.
• Generating electricity • Renewable and non-renewable sources of energy • Advantages and disadvantages of energy sources E • Percent efficiency = out × 100% Ein
• Non-renewable sources used for generating electricity include fossil fuels and nuclear energy. (12.1) • Renewable sources used for generating electricity include water, sunlight, wind, tides, and geothermal energy. (12.1) • There are both costs and benefits from producing electricity from renewable and non-renewable sources. (12.2) • Electrical savings can be achieved through the design of technological devices and practices in the home. (12.2)
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VOCABULARY
• charging by contact (p. 407) • conduction (p. 400) • conductivity (p. 400) • conductor (p. 400) • coulomb (C) (p. 399) • electric charge (p. 394) • electrical discharge (p. 411)
KEY VISUALS
• electron (p. 396) • electron affinity (p. 398) • electroscope (p. 404) • electrostatics (p. 404) • friction (p. 399) • grounding (p. 408) • induction (p. 407) • insulator (p. 400) • law of attraction (p. 399)
• law of repulsion (p. 399) • lightning rod (p. 418) • neutron (p. 396) • nucleus (p. 396) • proton (p. 396) • static charge (p. 396) • static electricity (p. 396)
• alternating current (AC) (p. 439)
• electric current (l ) (p. 439)
• potential difference (p. 437)
• ammeter (p. 439) • ampere (A) (p. 439)
• electrochemical cell, (p. 435)
• potential energy (p. 437)
• battery (p. 435)
• electrode (p. 435)
• resistance (R) (p. 441)
• circuit breaker (p. 463)
• electrolyte (p. 435)
• resistor (p. 441)
• circuit diagram (p. 450)
• fuel cell (p. 486)
• series circuit (p. 451)
• current electricity (p. 434)
• fuse (p. 463)
• short circuit (p. 462)
• ground fault circuit interrupter (p. 464)
• switch (p. 434)
• ohm (Ω) (p. 441)
• volt (V) (p. 438)
• direct current (DC) (p. 439)
Lightning strike
• transistor (p. 449)
• dry cell (p. 435)
• ohmmeter (p. 441)
• voltage (V ) (p. 437)
• electrical circuit (p. 434)
• Ohm’s law (p. 463)
• voltmeter (p. 438)
• parallel circuit (p. 451)
• wet cell (p. 435)
• electrical load (p. 434)
Microcircuits
• biomass (p. 478) • efficiency (p. 493) • EnerGuide (p. 494) • energy grid (p. 476) • Energy Star (p. 494) • fossil fuels (p. 478) • generators (p. 476)
• geothermal energy, (p. 479)
• renewable energy sources (p. 474)
• hydroelectricity (p. 477)
• thermoelectric generating plant (p. 478)
• kilowatt-hour (kW•h) (p. 492) • non-renewable energy sources (p. 474)
• thermonuclear (p. 470) • turbine (p. 476) Solar panels on rooftop
UNIT D
Summary
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Bringing Electrical Energy to a Community Criteria for Success • Your plans for generating electricity must be environmentally responsible. For example, a plan to build a new dam across a river will need to consider the effect of creating a new lake, as well as the effect on migrating species of fish. • Your plans for power generation must align with the other groups so that two groups are not competing to use the same natural resource, such as having two dams very close together. Solar cells can be used to generate electricity for individual buildings.
Getting Started You are an electrical energy consultant working on a plan to add additional electrical energy generating sources in an area prone to blackouts. Suppose your electricity has a main supply source, such as a coal power plant or a nuclear power plant. However, a number of environmental factors have led to frequent blackouts. These factors include high winds and icing problems with transmission lines. Your job includes developing new, smaller electricity generation sources. Each of these sources can connect to the regional electrical grid when the main source goes off-line or when main transmission lines to the grid fail. These new, smaller-scale sources will help provide a consistent supply of electrical energy to the region, even if the main electrical supply becomes unavailable.
• The types of generating methods your groups research must not all be the same. For example, if all groups plan a solar power generating station, this will be of little use if a blackout occurred at night. • Your plans must be supported by references to existing examples of electrical generation sources. You will need to research your example enough to know what will be necessary to adapt it to your particular location. For example, if an oil-fired generating source is needed, will you be able to use a technology that captures and stores carbon dioxide emissions? • Each group will submit a plan in order to create a class report that solves the problem of using backup generators to maintain consistent production of energy to the electrical grid.
Your Goal Your group will be in charge of planning a backup electrical generating station by researching existing examples of generating stations or technologies that can be used to generate electricity. Low-cost and environmentally friendly technologies are preferred. As a class, you will be required to propose a wide variety of technologies. Wind turbines can be used individually for small-scale electricity generation. They can also be grouped in wind farms for larger-scale generation. 504
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What You Need to Know A century ago, energy was generated in the same location that it was used or only a few kilometres away. Over the past 100 years, extensive electrical grids have been developed that are powered mainly by large generating stations. In many cases, smaller generating stations were discouraged or even prohibited from adding energy to the electrical grid. This is beginning to change as many smaller, more efficient, and often more environmentally friendly ways of generating power are being encouraged. For this task, you need to research one or more of these newer technologies for generating electricity by finding existing examples of where they are being used. You will then determine ways to adapt them to your local region.
What You Need • a large map of your region showing population centres, useful geographical features, and main lines of the power grid • Internet access for researching examples of methods of electrical power generation
Procedure 1. As a class, decide on the number of new generating stations that can be planned. Do this by dividing the size of the class by the size of each planning group. 2. As a class, brainstorm the specific geographical features that may be of use for electrical power generation in your community. This may involve using only real features in your area, or you may agree to include features not actually present but which will be useful for the purpose of this activity. Examples of features could include a fast-flowing river or waterfall, a high ridge that is usually windy, a large water supply useful for construction of cooling towers, or geothermal energy. You may wish to estimate the average annual hours of sunshine to determine whether to include solar energy.
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3. Form groups, and within your group brainstorm ideas for electrical generation methods. Agree on several options to bring back to the class for discussion. 4. As a class, share the ideas of each group. Remember that methods of electrical generation must be varied and must not conflict with each other or represent a threat to the environment. Agree as a class on what type of power generating source each group will investigate and where on the regional map each generating station will be located. 5. ScienceSource Research a plan for your generating station by examining existing stations or technologies already. 6. Design your generating station. Use clearly labelled diagrams. 7. Present your plan for the generating station. Describe how it fits into the overall regional plan with all of the groups’ plans.
Assessing Your Work 8. (a) Think about your role in the work your group accomplished. What do you think was the strongest contribution you made to your group’s work? (b) How could you improve your contribution to group work in future activities? 9. (a) What do you feel was the most effective aspect of your group’s plan? (b) How could your group’s design have been improved? 10. Write an evaluation of your approach to solving this problem. Did it work well? What would you have done differently and why?
UNIT D
Task
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Review
ACHIEVEMENT CHART CATEGORIES k Knowledge and understanding t Thinking and investigation c Communication a Application
7. Suppose you know that balloon A below is negatively charged but you do not know the charge on balloon B.
Key Terms Review 1. Create a mind map using the following terms. You may add more terms if you wish. c
• ammeter • ampere • battery • current • fuse • kilowatt-hour • load
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• ohm • potential difference • resistance • switch • voltmeter • volt
Static charges accumulate on surfaces and remain there until given a path to escape.
2. (a) Suppose you walk across the carpet, touch a metal doorknob, and get a shock. What charge do the particles causing the charge have: negative or positive? t (b) Use the structure of the atom to explain why these particles have the charge you identified in part (a). k 3. (a) State the law of attraction.
k
(b) State the law of repulsion.
k
4. Explain the steps you would take to tell the difference between a positively charged object and a negatively charged object. k 5. Use a series of diagrams to explain how a charged object attracts a neutral object. c 6. Suppose two different materials are rubbed together. Each one is brought near a charged electroscope with no effect on the electroscope. Explain what may be the reason that there is no effect. k
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+ –
–
–
+ –
?
– A
B Question 7
(a) When you bring the two balloons together, they repel each other. What is the charge on balloon B? k (b) Suppose that when you bring the two balloons together they attract each other. Does this observation prove that balloon B is positive? Explain why or why not. k 8. Object C is rubbed on object D. The leaves of a negatively charged electroscope temporarily move closer together when object D is brought near. (a) What charge does object D have?
k
(b) What charge does object C have?
k
9. Use a Venn diagram to compare and contrast charging by contact and charging by induction. k 10. Use labelled diagrams to explain how lightning occurs. c 11. (a) When clothes come out of a clothes dryer, they sometimes stick to each other. Explain why. k (b) Name three different ways to reduce this effect. k
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12. Explain the function of the metal rods in the photograph below. k
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18. Why does a light bulb light up immediately after you turn on a switch, even if the switch is a long way from the bulb? k 19. (a) Draw a circuit diagram that includes a battery, connecting wires, and a resistor. a
(b) Add a voltmeter to the circuit diagram to measure the potential difference across the resistor. a Question 12
13. How have static electricity controls helped in developing new technologies? k 14. (a) Name one device that would function better if static electricity were eliminated. k (b) Name one device that would not function as well if static electricity were eliminated. k
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Current electricity is the continuous flow of electrons in a closed circuit.
15. (a) What are the two main components of an electrochemical cell? k (b) What is the function of each component? k 16. Copy and complete the following chart in your notebook. k Definition
Abbreviation
Unit
Potential difference
a
20. (a) Use circuit symbols to draw a series circuit with a battery, connecting wires, and two light bulbs. a (b) Draw a parallel circuit using the same components as (a). a (c) Describe the difference in current flowing in the two circuits (a) and (b).
a
(d) What will happen to the brightness of the bulbs in circuit (a) if one of the bulbs is unscrewed? a (e) What will happen to the brightness of the bulbs in circuit (b) if one of the light bulbs is unscrewed? a 21. (a) What is the voltage at V1 in the circuit below? a (b) What is the current at A1 in the circuit below? a
Potential Difference, Current, and Resistance Quantity
(c) Add an ammeter to the circuit diagram to measure current through the resistor.
Symbol
(c) Is this circuit a series circuit or a parallel circuit? k
Current
2.0 A
Resistance
V1
9.0 V
17. (a) What are four factors affecting resistance in a wire? k (b) Describe how each factor affects resistance. k
3.0 V
A1
Question 21 Unit D
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22. (a) What is the voltage at V1 in the circuit below? a (b) What is the current at A1 in the circuit below? a (c) Is this circuit a series circuit or a parallel circuit? k
V1
30. What are three different electricity generating systems you could use on your property to provide electrical energy if you lived on a small farm? k 31. What effects do the following electricity generation methods have on surrounding ecosystems?
3.0 A
2.0 A
29. How is steam used in the generation of electricity? k
A1
(a) wind farms
3.0 V
k
(b) hydroelectric dams Question 22
23. Draw a circuit that keeps two lights on at all times and can switch two other light bulbs on and off independently. a 24. What does Ohm’s law state?
k
25. If the resistance of a load becomes larger, does current also become larger? Explain your answer. k 26. Most homes in Ontario are built to meet regulations that ensure safety and dependability of electrical systems. What are some ways in which the electrical system in your home has been made as safe as possible? k
k
32. What types of hazardous substances are used or created in the production of nuclear power? k 33. State some disadvantages of: (a) solar power
k
(b) tidal power
k
34. What is the price difference between electricity produced from solar power and by coal-burning plants? k 35. In what units is electrical energy consumption usually measured? k 36. The efficiency of a device is a ratio. What is it a ratio of? k
27. Why is it a good idea to use fused safety power bars for televisions, computers, and other sensitive electrical equipment? k
37. What information does an EnerGuide label provide? k
We can reduce our electrical energy consumption and use renewable energy resources to produce electrical energy.
39. How could you use the EnerGuide and Energy Star labels to help you decide when purchasing appliances or electronics? k
12
28. (a) Describe the difference between renewable and non-renewable energy sources. k (b) Give two examples of each type of source. k 508
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38. What does an Energy Star label indicate?
k
40. What causes the difference in energy consumption between a conventional and a front-loading washing machine? k
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41. List five appliances found in the home that consume electrical energy even when they are not in use? k
47. How does the charge on a charged electroscope compare with the charge in a functioning circuit? t
42. What are three benefits of lowering our energy demands? k
48. Explain why a cow that touches an electric fence gets a mild shock. A bird sitting on the same wire does not receive a shock. Why? a
Connect Your Understanding 43. (a) When lightning hits a car, is it safer to be in the car or outside the car but touching it? Explain why. a (b) You are standing close to a tall tree when you suddenly see lightning and hear thunder. Should you take shelter under the tree, run across the field to the nearest building, or do something else? Explain why. a 44. How are a lightning bolt and a spark similar? t 45. You have just combed your hair, and you bring the comb near some bits of paper. The paper is attracted to the comb, but as soon as the paper touches the comb, it is immediately deflected away. Explain what is happening in terms of charge motion, charging methods, and the triboelectric series. t 46. Some machines have a grounding screw connected to a wire or cable as shown in this photograph. (a) Explain what grounding a charged object does. k
49. The voltmeter and the ammeter are electrical loads. Each has an internal resistance. Relative to the resistors in the circuit, would their internal resistances be large or small? Explain. t 50. Why do lights dim in the house when certain appliances, such as an oven, hair dryer, or table saw, are used? t 51. For the following situations, explain the safety concern. a (a) A worker carries a large aluminum ladder near overhead hydro lines. (b) Someone takes the third prong out of a plug in order to use it with a two-prong extension cord. (c) The washing machine electrical cord is frayed. (d) You run out of fuses and put a piece of aluminum in place of the fuse. 52. A friend replaces a cord on a kettle with a new cord that is much thinner than the original. When the kettle is plugged in, the new cord gets much hotter than the old one did. Explain why. t
Question 46
(b) Explain why some objects need to be grounded. k (c) Give two examples of machines or devices that need to be grounded. t
53. Could a thermal generating plant be effective without a turbine? Explain.
t
54. (a) What is meant by a “non-thermal” method of generating electricity? t (b) Describe an example of such a method. t Unit D
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55. Suppose a more efficient appliance costs more than a regular appliance. Does it make sense to spend the extra money? Explain. t 56. Create a sketch, paragraph, or skit using electrical terms in a humorous manner. You should get a “charge” from doing this “potentially” fun exercise at “ohm” or at school. c
61. The graph below shows the relationship between voltage and current that emerged in tests for a particular resistor. Does this resistor work according to Ohm’s law? Explain. t Current vs. Voltage
Skills Practice
c u rre n t
57. What is the value of a resistor that transforms 2.0 mA of current when it is connected to a 6.0-V battery? a v o lt a g e
58. (a) What voltage is applied to a 5.0-Ω resistor if the current is 1.5 A? a (b) A voltage of 80 V is applied across a 20-Ω resistor. What is the current through the resistor? a (c) The current running through a starter motor in a car is 240 A. If this motor is connected to a 12-V battery, what is the resistance of the motor? a 59. Copy and complete the following chart in your notebook. Use Ohm’s law to create a set of data given that there are three resistors in series and each one has a resistance of 40 Ω. a
Voltage and Current Voltage (V)
Current (A)
2.0 4.0
(b) 1500 Ω = ____ kΩ (c) 650 mA = ____ A
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62. Copy and complete the following chart in your notebook. a Percent Efficiency Device
Input Energy (kJ)
Output Energy (kJ)
Gaspowered SUV
675
81
Gas-electric hybrid car
675
195
Natural gas furnace
110 000
85 000
Electric baseboard heater
9.5
6.0
Alkaline dry cell
84.52
74.38
6.0 8.0 10.0
60. Copy and convert each of the following units in your notebook. a (a) 1.6 MV = ____ V
Question 61
Percent Efficiency
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Revisit the Big Ideas and Fundamental Concepts 63. Create a poster on your opinion of one of the following topics. c (a) Why we should use renewable sources to generate electricity (b) Why we should conserve energy 64. Nuclear energy is one of the most efficient ways to produce electrical energy. Why are not all power plants nuclear? a 65. Choose a renewable source for generating electricity. Explain possible solutions to its disadvantages. t 66. Create a timeline that begins with this year and extends 30 years into the future. On the timeline, detail the steps your community could take to become energy self-sufficient. Include: c •
•
the new technologies for generating electricity that could be installed, including where you recommend installing them the energy-conserving methods that could be implemented
67. Write a three-paragraph essay in answer to the following question: “How can we improve our lives by controlling, using, and conserving electricity in an environmentally friendly way?” c
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Science, Technology, Society, and the Environment
68. Create a graphic representation, such as a mind map or other chart, to answer the following questions. Include labelled diagrams if you wish. c (a) What are the costs and benefits associated with the production of electrical energy from renewable and non-renewable sources? (b) How can electrical efficiencies and savings be achieved through the design of technological devices and practices in the home? 69. Based on the activities you have done in this unit, answer the following questions. Include your personal observations. You may wish to include labelled diagrams and/or refer to specific activities as part of your answer. c (a) What are the properties of static electricity and current electricity? (b) What is the relationship between potential difference, current, and resistance in an electrical circuit?
Reflection 70. (a) After completing this unit, how have you changed your attitude toward how you use electrical energy? c (b) What changes are you thinking of implementing? c
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Skills References Contents Skills Reference 1
Safety Symbols
Skills Reference 2
The Inquiry Process of Science
Skills Reference 3
The Problem-Solving Process for Technological Development
Skills Reference 4
The Decision-Making Process for Social and Environmental Issues • Researching Topics
Skills Reference 5
Reading in Science
Skills Reference 6
Communicating in Science • Diagrams
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Skills Reference 7
Graphic Organizers
Skills Reference 8
Measurement
Skills Reference 9
Graphing
Skills Reference 10
Using a Microscope
Skills Reference 11
Chemistry Backgrounder
Skills Reference 12
Using a Star Chart
Skills Reference 13
Electricity Backgrounder
Skills References
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Safety Symbols Safety symbols identify potential hazards. When you see any of the following symbols, either in this book or on a product, take extra care.
classrooms. They may also be on other manufactured products bought for home use. A container may have one or more of the symbols shown below.
Safety Symbols in This Book Some activities in this book have symbols to help you conduct the activity safely. Look for these symbols at the beginning of activities. When you see this symbol, wear goggles or safety glasses while doing the activity. This symbol tells you that you will be using glassware during the activity. Take extra care when handling it.
compressed gas
biohazardous infectious material
dangerously reactive material
corrosive material
oxidizing material
flammable and combustible material
poisonous and infectious causing immediate and serious toxic effects
poisonous and infectious causing other toxic effects
When you see this symbol, wear an apron while doing the activity. When you see this symbol, wear insulated gloves to protect your hands from heat. This symbol tells you that you will be working with sharp objects. Take extra care when handling them. When you see this symbol, wear gloves while doing the activity. This symbol tells you that you will be working with wires and power sources. Take extra care when handling them. This symbol tells you that you will be working with fire. Make sure to tie back loose hair. Take extra care around flames.
WHMIS Symbols Here are symbols you might see on the materials you use in your classroom. You will see them occasionally in the Materials and Equipment lists for activities when a substance that needs a warning is used. These symbols are called Workplace Hazardous Materials Information System (WHMIS) symbols. They are placed on hazardous materials used at job sites and in science
Hazard Symbols for Home Products You have probably seen some of these hazard symbols on products at home. They are a warning that the products can be harmful or dangerous if handled improperly. These hazard symbols have two shapes: a triangle or an octagon. A triangle means that the container is dangerous. An octagon means that the contents of the container are dangerous. Here are four of the most common symbols. Flammable Hazard: The product could ignite (catch on fire) if exposed to flames, sparks, friction, or even heat. Toxic Hazard: The product is very poisonous and could have immediate and serious effects, including death, if eaten or drunk. Smelling or tasting some products can also cause serious harm. Corrosive Hazard: The product will corrode clothing, skin, or other materials and will burn eyes on contact. Explosive Hazard: The container can explode if it is heated or punctured.
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Safety Symbols
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The Inquiry Process of Science Scientists are always asking a lot of questions. They are always inquiring. They want to understand why the things they observe, and wonder about, happen. Experiments are important tools that scientists use to help them answer their questions. When scientists plan experiments, they usually follow a simple set of steps. Step 1
Step 3
Step 4
Step 5
Step 6
Step 7
Hint Answers may lead to additional questions. New questions often lead to new hypotheses and experiments. Don’t be afraid to ask questions, or to rethink the ones you’ve already asked.
Skills Reference 2
Asking questions is easy. Asking questions that lead to reliable answers is more challenging. That’s the reason scientists usually ask cause-and-effect questions. Here are a few examples. • How does the concentration of laundry detergent in wash water affect the cleanliness of clothing? • How do different temperatures affect the growth of seedlings? • How does the amount of moisture affect the growth of mould on bread? Notice how the causes — the detergent, temperature, and moisture — are things that are changeable. For example, you can have different concentrations of detergent, different temperatures, and different amounts of moisture. Causes are manipulated, usually called independent variables. They are factors that you change when you investigate a cause-and-effect question. The results are changeable, too. For example, some clothes may become cleaner than others or not clean at all. Some seedlings may grow better than others or some might not grow at all. Some bread samples may have lots of mould, some may have less, and some might not have any. Results are responding variables usually called dependent variables. They change because of the independent variable. When you ask a cause-and-effect question, you should include only one independent variable in your question. This allows you to see the effect of that variable on the dependent variable.
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STEP 1 Ask a cause-and-effect question.
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STEP 2 Restate the question in the form of a hypothesis.
STEP 3 Develop a procedure to test the hypothesis fairly.
A hypothesis is a way of restating a cause-and-effect question so that it gives a reasonable, possible answer. Basically, a hypothesis is an intelligent guess at the solution to a problem or question. It is usually in the form of an “If ... then” statement and states the relationship between the independent and dependent variables. Here are hypotheses for the questions outlined in Step 1.
When you develop a procedure, you need to ask yourself some questions. Your answers to these questions will help you plan a fair and safe experiment. Here are some questions you should think about. These questions are answered for the seedling experiment.
• If the concentration of the detergent is high, then clothing will become cleaner. • If the temperature is decreased, then the seedlings will not grow as well. • If the amount of moisture is increased, then the bread will get mouldier.
Hint A hypothesis is an early step in the experimentplanning process. Your hypothesis can turn out to be “right,” but it doesn’t always. That’s what the experiment is for — to test the hypothesis.
• Which independent variable do you want to investigate? The independent variable is temperature. • How will you measure this variable (if it is measurable)? You can measure temperature with a thermometer. • How will you keep all other variables constant (the same) so they don’t affect your results? In other words, how will you control your experiment so it is a fair test? To control the experiment, these variables should be kept constant: the amount of light the seedlings receive; the amount and temperature of water applied to the seedlings; the kind of soil the seedlings are planted in. • What materials and equipment will you need for the experiment? The materials would include seedlings, soil, growing pots or containers (same size), water and a watering can, a light source, a thermometer, and a ruler or other measuring device. • How will you conduct the experiment safely? What safety factors should you consider? Some of the safety factors to consider include putting the seedling pots in a place where they would not be disturbed, washing your hands after handling the materials, and making sure you don’t have any allergies to the soil or seedlings you use. • How will you set up the procedure to get the data you need to test your hypothesis? You could divide your seedlings into groups (e.g., three seedlings for each temperature) and grow each group at a certain temperature. You would keep track of how much each seedling in a group grew over a specified amount of time (e.g., four weeks) and calculate the average for the group.
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STEP 4 Carry out the procedure, and collect data. Depending on the kind of experiment you have planned, you may choose to record the data you collect in the form of a chart or table, a labelled sketch, notes, or a combination of these. For example, a good way to record the seedling data would be in a table (one for each week of the experiment). Week 1: Height of Seedlings Grown at Different Temperatures Temperature seedlings grown at (°C)
Height of Height of Height of Average seedling 1 seedling 2 seedling 3 height (cm) (cm) (cm) (cm)
20 15 10
Hint Analyzing the data you collect is the only way you have to assess your hypothesis. It’s important that your record keeping be organized and neat.
STEP 5 Analyze and interpret the data. Scientists look for patterns and relationships in their data. Often, making a graph can help them see patterns and relationships more easily. (Refer to Skills Reference 9 for more about graphing.) A graph of the seedling data would show you if there is a relationship between temperature and growth rate.
Hint If you have access to a computer, find out if it has the software to help you make charts or graphs.
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Sources of Error Analysis of the results usually includes the sources of error. One source of error is the variation that always occurs when an experiment is repeated, even though the experimenter follows a well-designed procedure carefully and works with properly functioning equipment. This error is mainly due to the limits in the precision (reproducibility) of the particular instrument used to take the measurements and in its readability. Scientists always repeat an experiment several times, which helps to reduce the effect of this source of error. In the science classroom, you may not always be able to repeat your experiment. However, you can get a sense of the accuracy of your results by comparing your data with those of your classmates or with theoretical values. Another source of error can occur when a measuring instrument has not been properly calibrated. Calibration is the process of comparing the measurements given by the instrument against known standards and ensuring that the two values match. If an instrument is not properly calibrated, the measurements taken with that instrument will always contain an error. Professional scientists therefore calibrate their instruments regularly. These sources of error can be avoided. Finally, error may result if there is a flaw in the design of the experiment or in how the procedure was carried out. When an experiment is affected by this source of error, the relationship between the independent and dependent variables will be unclear. If this occurs, reexamine the procedure and ensure that there were no unidentified variables that may have affected the results.
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STEP 6 Form conclusions based on the data, and compare them with the hypothesis.
STEP 7 Communicate the procedure and results of the experiment.
Usually, forming a conclusion is fairly straightforward. Either your data will support your hypothesis or they won’t. Either way, however, you aren’t finished answering your cause-and-effect question. For example, if the seedlings did not grow as well in cooler temperatures, you can conclude that your data support your hypothesis. But you will still need to repeat your experiment several times to see if you get the same results over and over again. Doing your experiment successfully many times is the only way you and other scientists can have faith in your data and your conclusions. If your data don’t support your hypothesis, there are two possible reasons why.
Scientists always share the results of their experiments with other people. They do this by summarizing how they performed the first six steps. Sometimes, they will write out a formal report stating their purpose, hypothesis, procedure, observations, and conclusions. Other times, they share their experimental results verbally, using drawings, charts, or graphs. (See Skills References 6 and 9 for help on how to prepare your results.) When you have finished your experiment, ask your teacher how he or she would like you to prepare your results so you can share them with the other students in your class.
• Perhaps your experimental plan was flawed and needs to be reassessed and possibly planned again. • Perhaps your hypothesis was incorrect and needs to be reassessed and modified. For example, if the seedlings grew better in the lower temperatures, you would have to rethink your hypothesis or look at your experiment for flaws. You would need to ask questions to help you evaluate and change either your hypothesis or plan. For example, you could ask: Do certain seedlings grow better at lower temperatures than others? Do different types of soil have more of an effect on growth than temperature? Every experiment is different and will result in its own set of questions and conclusions.
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The Problem-Solving Process for Technological Development When you plan an experiment to answer a cause-and-effect question, you follow an orderly set of steps. The same is true for designing a model or prototype that solves a practical problem. When people try to solve practical problems, they usually follow a simple set of steps.
Step 1
Step 2
STEP 1 Recognize a human need. This involves recognizing what the problem is. For example, suppose you observe that a rope bridge across a ravine at a local park is very unstable and swings back and forth when crossed. You find that most people are not comfortable crossing the bridge and don’t get to enjoy one of the nicer areas of the park. You wish there were a way to make the bridge more stable so more people would use it. That is the situation or context of the problem.
STEP 2 Identify the specific problem to be solved. When you understand a situation, you can then define the problem more exactly. This means identifying a specific task to carry out. In the situation with the bridge, the task might be to build a new bridge or add support to the existing bridge.
Step 3
STEP 3 Identify criteria for a successful solution to a problem. Step 4
Step 5
Step 6
Step 7
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You have defined the problem but before you start looking for solutions, you need to establish your criteria for determining what a successful solution will be. One of your criteria for success in the bridge example would be the completion of a stable bridge. The criteria you choose do not depend on which solution you select — whether to reinforce the old bridge or build a new bridge. In this case, whatever the solution, it must result in a stable bridge. When you are setting your criteria for success, you must consider limits to your possible solutions. For example, the bridge may have to be built within a certain time, so rebuilding completely may not be possible. Other limitations could include availability of materials, cost, number of workers needed, and safety. If you are building a product or device for yourself, you may set the criteria for success and the limitations yourself. In class, your teacher will usually outline them.
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Hint Always consider safety. This includes safe handling and use of materials and equipment, as well as being aware of possible environmental impacts of your ideas. Discuss with your teacher and fellow students how your solution might affect the environment.
STEP 4 Generate a list of ideas, possible solutions, materials, and equipment. Brainstorming and conducting research are key components of this step. When you brainstorm, remember to relax and let your imagination go. Brainstorming is all about generating as many ideas as possible without judging them. Record your ideas in the form of words, mind maps, sketches — whatever helps you best. Conducting research may involve reading books and magazines, searching the Internet, interviewing people, or visiting stores. It all depends on what you are going to design. One idea for the rope bridge would be to anchor the bridge with strong rope or thick metal wire to large rocks or to the hillside at either end of the bridge. Sketches and diagrams would help to generate different ideas for the bridge design.
Hint Humans have been inventors for tens of thousands of years — so take advantage of what has already been developed. When you’re solving a problem, see how others have solved the same problem before and use their efforts as inspiration. You can also look for ways to improve on their ideas.
STEP 5 Plan and construct a working model or prototype. Choose one possible solution to develop. Start by making a list of the materials and equipment you will use. Then, make a working diagram, or series of diagrams, on paper. This lets you explore and troubleshoot your ideas
Skills Reference 3
early on. Your labels should be detailed enough so that other people could build your design. Show your plans to your teacher before you begin construction work. A simple model of the bridge could be made to show how and where components such as stabilizing wires could be added.
Hint If things aren’t working as you planned or imagined, be prepared to modify your plans as you construct your model or prototype.
STEP 6 Test, evaluate, and modify (if necessary) the model or prototype. Testing lets you see how well your solution works. Testing also lets you know if you need to make modifications. Does your model or prototype meet all the established criteria? Does it solve the problem you designed it for? Invite your classmates to try your product. Their feedback can help you decide what is and isn’t working and how to fix anything that needs fixing. Perhaps the stabilizing wires on the bridge model could be anchored elsewhere. Maybe more wires could be added.
Hint For every successful invention or product, there are thousands of unsuccessful ones. Sometimes, it’s better to start over from scratch than to follow a design that doesn’t meet its performance criteria.
STEP 7 Communicate the procedure and results of your design. Inventors and engineers create things to meet people’s needs. When they make something new, they like to show it to other people and explain to them how it works. Sometimes, they will use a carefully drawn diagram of the new device and write about how they performed the first six steps. Other times, they will show the device to people and explain verbally how it works and how they built it. Your teacher will tell you how to prepare your results so you can exhibit the new device you make. The Problem-Solving Process for Technological Development
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The Decision-Making Process for Social and Environmental Issues People can have many different viewpoints or perspectives about social and environmental issues. This usually means that an issue has more than one possible solution. Scientific and technological information can be used to increase our understanding of an issue and help resolve it. When people try to make a decision or reach a consensus about an issue, they need to use a decision-making process. Here are the steps in one possible process.
••••
Step 1
••••
Step 2
Step 3
STEP 1 Recognize the issue needing a decision. This involves recognizing that an issue exists. An issue is a controversy that needs to be resolved. It may have more than one possible solution, but the chosen one is usually the one that satisfies the most people. For example, suppose you and your friends want to have some trees in a public park cut down in order to make space for a playing field. Some members of your community feel that the trees should be preserved for the birds that nest there. The local environmental specialist says that when it rains, the trees protect a nearby stream by reducing run-off, so they should be left standing. Other people say that your idea of building a playing field is too expensive.
STEP 2 Identify the viewpoints related to the issue. The viewpoints expressed in the example in Step 1 are recreational, ecological, and economic. People often evaluate issues using one or more viewpoints. Some of these viewpoints are:
•••
Different Viewpoints
•••
Step 4
Viewpoints
Interested in
Cultural
Customs and practices of a particular group of people
Ecological
Protection of the natural environment
Economic
Financial aspects of the situation
Educational
Acquiring and sharing knowledge and skills
Esthetical
Beauty of art and nature
Ethical
Beliefs about what is right and wrong
Health and safety
Physical and mental well-being
Historical
Knowledge in dealing with past events
Political
Effect of the issues on governments, politicians, political parties
Recreational
Leisure activities
Scientific
Knowledge based on the inquiry process of science
Social
Human relationships, public welfare, or society
Technological
Design and use of tools and processes that solve practical problems to satisfy people’s wants and needs
••••
Step 5
•••
Step 6
Step 7
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STEP 3 Conduct research on the issue and the different viewpoints.
STEP 5 Analyze the consequences for each alternative.
You will be able to suggest an appropriate solution to an issue only if you understand the issue and the different viewpoints. It’s important to gather unbiased information about the issue itself and then consider the information provided by people with different viewpoints. Develop specific questions that will help to guide your research. Questions for the playing field issue might be:
Decide how you will measure the risks and benefits for the consequences of each alternative solution. The importance of the consequence and the likelihood of its occurrence can be ranked high (3), moderate (2), low (1), or none (0). Duration is considered short term (S) if it is less than 50 years or long term (L) if it is longer than 50 years. Ask how many people will benefit from the alternative and how many will be affected negatively. Make sure to consider health and safety. For the playing field example, you could analyze the consequences of each alternative solution in a table like the one shown below.
• How many people will use the playing field? • Is there another more suitable site for the playing field? • What kind of birds nest in these trees? Could they nest elsewhere in the area? • What is run-off, and why is it a problem? • What would be the full cost of building the playing field (including the cost of removing the trees)? Conducting research may involve interviewing people, reading books and magazines, searching the Internet, or making a field trip. It is important to evaluate your sources of information to determine if there is a bias and to separate fact from opinion. In this step, you are trying to gain a better understanding of the background of the issue, the viewpoints of different groups, the alternative solutions, and the consequences of each alternative. You will find tips on how to conduct research in the following section on researching topics.
Examine the background of the issue and the viewpoints in order to generate a list of alternative solutions. Brainstorming can be a useful component of this step. Use your research to help guide your thinking. Examples of possible alternatives for the issue in Step 1 might be as follows: Cut the trees and build the playing field. Leave the park as it is. Find another more suitable location. Modify the plan in the existing park.
Skills Reference 4
Consequence
Importance (3, 2, 1, 0)
Likelihood of occurrence (3, 2, 1, 0)
Duration (S, L)
Trees cut
2
3
L
Run-off
3
3
S
Birds move
2 to 1
3
L
Playing field well used
2
2
possibly L
Development and maintenance cost
2 to 1
3
L
STEP 6 Reflect and decide on the best course of action.
STEP 4 Generate a list of alternative solutions.
• • • •
Build the Playing Field in the Park
Evaluate your decision-making process to ensure that each step is completed as fully as possible. Consider the consequences of the alternative solutions and how people will respond to each one. Then, decide on what you think is the best course of action.
STEP 7 Communicate your findings. Communicate your findings in an appropriate way. For example, you may prepare a written report, a verbal presentation, or a position for a debate or a public hearing role-play. Defend your position by clearly stating your case and presenting supporting evidence from a variety of sources.
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Researching Topics Research involves finding out something about a topic or subject. That means going to certain resources that will give you accurate information. Information can be found just about anywhere: from your home bookshelves to the public library, from asking experts to looking on the Internet. Here is the process you should follow when you do your research.
Choosing a Topic In some situations, your teacher may give you the topic to research. Other times, you will select one of your own, such as the issue described in this Skills Reference. If you have trouble coming up with a topic, try brainstorming ideas either by yourself or with a group. Remember, when you brainstorm, there are no right or wrong answers, just ideas. Here are some brainstorming suggestions to get you started: • List two or three general topics about science that interest you. • For each topic, spend a few minutes writing down as many words or ideas that relate to that topic as you can. They don’t have to be directly connected to science. • Share your list with others, and ask them to suggest other possibilities. • Now you have to reduce your idea list to find a topic to research. In other words, go through your ideas until you find two or three that interest you. To help you narrow your idea list, try grouping similar words or ideas, modifying what
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you’ve written, or even writing down a new idea. Sometimes, working with other people will help to focus your thoughts. • When you settle on an idea for your topic, write it down. Try to explain it in a couple of sentences or a short paragraph. Do that for each of your two or three topic ideas. • Have your teacher approve your topics. Now you’re ready to go! Which Topic Should I Choose? How does product design help sell a product?
How do gears improve the performance of a bicycle?
The next thing you have to do is settle on one topic. (Remember, you should start your research with two or three topic ideas.) One way to help you decide is to determine how easy it will be to find information on your topic.
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• Use some of the resources listed under “Finding Information” to do your preliminary research. • If you can’t easily find at least four good references for a topic, consider dropping it and going on to the next idea.
Once you’ve finally chosen your topic, you might want to work with other students and your teacher to:
Hint
Finding Information
Sometimes, topics are too broad in scope or too general to make good research reports (for example, “transportation” instead of just “bicycles”). Try rewriting your topic to narrow its focus.
If all the topics are easy to research, then you’ll need some other criteria to help you decide. Think about: • which topic interests you the most • which topic is not being researched by many students in your class • which topic interests you the least
• finalize its wording • make sure it matches the project or assignment you are doing
There are many resources that you can use to look up information. You’ll find some of these resources: • in your school • in your community (such as your public library) • on the Internet • in CD-ROM encyclopedias and databases Here is a suggested list of resources. Types of Resources Resource
Details
Books
How Hard Will It Be to Find Information?
CD-ROMs Community professionals or experts
How camera lenses are manufactured
Encyclopedias Films Government agencies (local, provincial, and federal) Internet sites Journals Library catalogue Newspapers
How mirrors are used in some optical devices
Non-profit organizations Posters DVDs and videos
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Searching Tips
Hints
Finding Information at Your Library Library computer catalogues are a fast way to find books on the subjects you are researching. Most of these electronic catalogues have four ways to search: subject, author, title, and key words. If you know the author or title of a book, just type it in. Otherwise, use the subject and key words searches to find books on your topic.
• If you’re doing a subject search, type in the main topic you are researching. For example, if you’re searching for information on solar energy, type in “solar energy.” If there are no books on that topic, try again using a more general category, like “renewable resources,” or just “energy.” • If you’re doing a key words search, type in any combination of words that have to do with your topic. For the solar energy example, you could type in words such as: “renewable energy sun solar panels.” Using several key words will give you a more specific search. Using only one or two key words, like “sun” and “energy,” will give you a more general search. 524
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• The library may also have a way to search for magazine articles. This is called a periodical search. It’s especially useful for searching for information on events and/or discoveries that have taken place recently. Ask your librarian how to do a periodical search. • Your library will probably have a reference section where all the encyclopedias are kept. There you may find science and technology, environmental, or even animal encyclopedias, as well as other reference books.
Finding Information on the Internet On the Internet, you can use searching programs, called search engines, to search the Internet on just about any subject. To find a search engine, ask your teacher or click on the search icon found at the top of your Internet browser. Here are some suggestions on how to search the Internet: • Once you reach a search engine Web page, type in key words or phrases that have to do with your topic. For solar energy, you could type in “solar energy,” “solar panels,” “renewable resources,” or any combination of these and other similar words.
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• The search engine will display a list of Web pages it has found that have these words or phrases somewhere in them. Click on any Web page on the list that looks interesting. • Quite often, you will get a long list of possible Web pages to look at. You may need to make your search more specific. This can be done by adding other key words to your search. For example, if you were looking for solar energy examples in Canada and used the key word “solar energy,” you may want to do a second search of these results with the key word “Canada” added. • Don’t forget to record the addresses of any interesting Web pages you find. Work with a friend. One person can record the addresses of Web pages while the other person searches on the computer. Or you can save any Web page as a bookmark for easy future access. Check with your teacher or librarian to find out how to save and organize your bookmarks.
BEFORE YOU START! Check with your teacher to find out what your school’s policy is about acceptable use of the Internet. Remember to follow this policy whenever you use the Internet at school. Be aware as you use the Internet that some websites may be strongly biased toward a specific point of view. If you are looking for scientific or technical information, educational or government websites are generally reliable.
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Recording Your Information Sources An important part of researching a topic is keeping track of where you obtain information. As you do your research, you are reading through or viewing a variety of different sources. Some may be in print, such as magazines and books. Others may be electronic, such as websites and CD-ROMs. And others may be visual, such as videos and photos. No matter what sources you use, you should keep track of them. With this information, you can easily go back and check details. You can also use it to help you respond to any questions about the accuracy or completeness of your information. Your record of sources should include at least the following basic information: • title or name of the source (e.g., if you read a chapter of a book, you would write down the book’s title; for a website, you would include the address) • author’s name, if known • publisher (e.g., for a website, this would be the name of the person or the organization that has put up the site) • date of publication • pages consulted Your teacher may want you to list your information sources in a specific format. Check what this format will be before you begin your research so that you can collect the details you need to complete your reference list later. You may want to do your own research on formats for such reference lists or bibliographies.
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Reading in Science You use different skills and strategies when reading different materials such as a novel or a textbook. In a novel, you are mainly reading to enjoy the story. In a science textbook, you are reading for information. A science textbook has terms and concepts that you need to understand. Investigating Science 9 helps you with your non-fiction reading by giving you opportunities to use different reading strategies. You will find these reading strategies in the following literacy activities: • Before Reading at the beginning of each chapter • During Reading in each section • After Reading at the end of each chapter
Using Reading Strategies You can use the following strategies to help you better understand the information presented in this book. Before Reading • Skim the section you are going to read. Look at the headings, subheadings, visuals, and boldfaced words to determine the topic. • Look at how the information is organized. Ask yourself: Is it a causeand-effect passage? Is it a contrast-andcompare passage? Think about how the organization can help you access the information. • Think about what you already know about the topic. • Predict what you will learn.
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• List questions that you have about the topic. This will help you to set a purpose for reading. During Reading • Rewrite the section headings and subheadings as questions. Look for the answers to the questions as you read. • Use your answers to the questions to decide on the main idea in each section or subsection. • Look carefully at any visuals — photographs, illustrations, charts, or graphs. Read the captions and labels that go with the illustrations and photographs, and the titles of any charts or graphs. Think about the information the visuals give you and how this information helps you understand the ideas presented in the text. • Notice the terms that are boldfaced (dark and heavy type). These are important words that will help you understand and write about the information in the section. Make sure you understand the terms and how they are used. Check the terms in the Glossary to confirm their meanings. • Use different strategies to help remember what you read. For example, you can make mental pictures, make connections to what you know, or draw a sketch.
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After Reading • Find the information to answer any review questions. Use the headings and boldfaced terms to locate the information needed. Even if you are sure of the answer, reread to confirm that your answer is correct. • Write brief notes to synthesize what you have learned, or organize the information in a graphic organizer. You will find information about graphic organizers in Skills Reference 7. • Personalize the information. Think about opinions you have on what you’ve read. Consider if the new information you have learned has changed any previous ideas. List questions you still have about the topic. Note-Taking Chart A note-taking chart helps you understand how the material you are reading is organized. It also helps you keep track of information as you read. Your teacher will assign several pages for you to read. Before you begin reading, look at each heading and turn it into a question. Try to use “how,” “what,” or “why” to begin each question. Write your questions in the lefthand column of your chart. Leave enough space between each question so that you can record information from your reading that answers your question.
For example, you may be assigned several pages about the scientific meaning of work. These pages contain the following headings: • The Meaning of Work • Calculating Work • Energy and Work You can see an example of a note-taking chart below.
Questions from Headings
Answers from Reading
What is the meaning of the word “work”?
– work is done when a force acts on an object to make the object move – If there’s no movement, no work is done – just trying to push something isn’t work—it’s only work if the object moves
How do you calculate work? How are energy and work related?
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Communicating in Science In science, you use your communication skills to clearly show your knowledge, ideas, and understanding. You can use words and visuals, such as diagrams, charts, and tables, to communicate what you know. Some communication may be short, as in answering questions, or long, as in reports.
Give your report or project a title. Write a brief title on the top of the first page of your report. Your title can be one or two words that describe a product you designed and made, or it can be a short sentence that summarizes an experiment you performed, or it can state the topic of an issue you explored.
Writing Reports
Tell readers why you did the work. Use a heading such as “Introduction” or “Purpose” for this section. Here, you give your reasons for doing a particular experiment, designing and making a particular product, or considering a specific issue. If you are writing about an experiment, tell readers what your cause-and-effect question is. If you designed a product, explain why this product is needed, what it will do, who might use it, and who might benefit from its use. If you were considering an issue, state what the issue is and why you have prepared this report about it.
Skills Reference 2 shows you how to plan a science experiment. Skills Reference 3 shows you how to do technological design, and Skills Reference 4 shows you how to use a decisionmaking process for social and environmental issues. Here you will learn how to write a report so you can communicate the procedure and results of your work. Here is a list of things you should try to do when writing your science reports. • Give your report or project a title. • Tell readers why you did the work. • State your hypothesis, or describe the design challenge. • List the materials and equipment you used. • Describe the steps you took when you did your experiment, designed and made your product, or considered an issue. • Show your experimental data, the results of testing your product, or the background information on the issue. • Interpret and analyze the results of your experiment. • Make conclusions based on the outcome of the experiment, the success of the product you designed, or the research you did on an issue. 528
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State your hypothesis, or describe the design challenge. If you are writing about an experiment, use a heading such as “Hypothesis.” Under this heading you will state your hypothesis. Your hypothesis is your guess at the solution to a problem or question. It makes a prediction that your experiment will test. Your hypothesis must indicate the relationship between the independent and dependent variables. If you are writing about a product you designed, use a heading such as “Design Challenge.” Under this heading, you will describe why you decided to design your product the way you did. Explain how and why you chose your design over other possible designs.
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List the materials and equipment you used. This section can come under a heading called “Materials and Equipment.” List all the materials and equipment you used for your experiment or design project. Your list can be in point form or set up as a table or chart. Remember to include the exact amounts of materials used, when possible (for example, the number of nails used in building a model or the volumes and masses of substances tested in an experiment). Include the exact measurements and proper units for all materials used. Also include diagrams to show how you set up your equipment or how you prepared your materials. Remember to label the important features on your diagrams. (See the next few pages on diagrams for drawing tips.) Describe the steps you took when you did your experiment, designed and made your product, or researched the issue. Under a heading called “Procedure” or “Method,” describe, in detail, the steps you followed when doing your experiment, designing and making your product, or considering an issue. If you made a product, describe how you tested it. If you had to alter your design, describe in detail how you did this. Show your experimental data, the results of testing your product, or the background information on the issue. Give this section a heading such as “Data,” “Observations,” or “Background Information.” In this section, you should show the data or information you collected while performing the experiment, testing your product, or researching an issue. In reporting
about an issue, use only a summary of the essential information needed for a reader to understand the issue and different viewpoints about it. Use tables, diagrams, and any other visual aids that show the results of your tests. If you performed your experiment a few times, give results for each trial. If you tested different designs of your product, give results for each design. Interpret and analyze the results of your experiment. Interpret and analyze the data you collected in your experiment. Calculations, graphs, diagrams, charts, or other visual aids may be needed. (See Skills Reference 9 for graphing tips.) Explain any calculations or graphs that you used to help explain your results. Make conclusions based on the outcome of the experiment, the success of the product you designed, or the research you did on an issue. This last section of your report can be called “Conclusions.” In one or two paragraphs, explain what your tests and experiments showed or what decision you made as a result of your research. If you did an experiment, explain if your results were predicted by the hypothesis. Describe how you might adjust the hypothesis because of what you learned from doing the experiment and how you might test this new hypothesis. If you made a product, explain if your design did what it was supposed to do or worked the way it was supposed to work.
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If you changed the design of your product, explain why one design is better than another. Describe the practical applications your product or experiment might have for the world outside the classroom. If you considered an issue, explain why you made your decision. Briefly summarize your supporting evidence. If necessary, explain how you have responded to different viewpoints on the issue.
Diagrams In science, a carefully done diagram can help you express your ideas, record important information, and experiment with designs. Diagrams are an important tool in communicating what you know and your ideas. Four types of diagrams you can use are a simple sketch, an isometric diagram, an orthographic (perspective) diagram, and a computer-assisted diagram. Examples of these types of diagrams are shown on the next page. The photo on this page shows the set-up of an experiment. Practise drawing it using one or several of the diagram types presented on the next page.
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Tools of the Trade You will need the following equipment for each type of diagram. Hand-drawing tools • a sharp pencil or mechanical pencil • a pencil sharpener or extra leads • an eraser • a ruler For simple and isometric diagrams • blank white paper For computer-assisted diagrams • access to computer and software For orthographic drawings • blank orthographic graph paper Remember! • Give your diagram a title at the top of the page. • Use the whole page for your diagram. • Include only those details that are necessary, keep them simple, and identify them by name. • If you need labels, use lines, not arrows. Place your labels in line with the feature being labelled, and use a ruler to keep your lines straight. • Don’t use colour or shading unless your teacher asks you to. • Include notes and ideas if the sketch is a design for a structure or an invention.
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An Isometric Diagram
Hint If you’re going to use your diagram to help you design a structure, include a front, side, and top view.
A Simple Sketch (Front View) 10
cm
chimney splint 10
cm
18
cm
A Computer-Assisted Diagram candle box
A Simple Sketch (Side View)
An Orthographic (Perspective) Drawing
A Simple Sketch (Top View)
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Graphic Organizers Graphic organizers can be used to organize information that you read, and to display ideas visually. Type of Graphic Organizer
Purpose
Method
Concept map or web diagram
Used to clarify relationships and linkages between concepts, events, or ideas
Brainstorm ideas and link together from “big to small” with arrows or lines linking words. Cluster information around a central concept or idea.
Venn diagram
Used to visualize similarities and differences between two or more ideas, topics, or concepts
Brainstorm similarities, and list these in the overlapping section of the two circles. Then, brainstorm differences, and list these in the non-overlapping sections.
Flowchart or sequence chart
Used to map out your thinking about an issue or to organize ideas for an essay or report
Brainstorm aspects of the whole event or concept. Select important aspects, and put them into sequential order.
Ranking ladder
Used to rank ideas in order of importance
Brainstorm ideas, and rank them in order from most important (bottom rung) to least important (top rung).
Comparison matrix
Used to compare the characteristics or properties of a number of things
Brainstorm what you want to compare. Write the characteristics of the things that you will compare and how the things you compare are similar or different.
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same
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Purpose
Method
Used to analyze cause-and-effect relationships
List the effect at the head of the “fish.” Brainstorm possible causes, and list them in each “bone.” Rank the causes and circle the most probable ones, justifying your choice.
Right-angle diagram
Used to explore the consequences of an idea and the impact of its application
Briefly describe the idea you are exploring on the horizontal arrow. Brainstorm consequences of the idea, and list these to the right of the horizontal arrow. Expand on one consequence, and list details about it along the vertical arrow. Describe social impacts of that consequence below the vertical arrow.
Target diagram
Used to weigh the importance of facts and ideas
Brainstorm facts and ideas. Rank their importance and place the most important facts or ideas centrally and the least important toward the outer ring.
Agree/disagree chart
Used to organize data to support a position for or against an idea or decision
List a series of statements relating to a topic or issue. Survey agreement and disagreement before discussion. Survey again after discussion and research.
Used to summarize the negative (costs) and positive (benefits) aspects of a topic or issue
List ideas or information relating to the topic or issue. Sort the ideas or information in a chart that includes the headings “Costs” and “Benefits.”
Used to identify and sequence the concepts by placing the main concept at the top of the diagram and all the parts below it
Place the main concept at the top of the page. Then, consider the question “What concepts need to be understood before the concept above can be grasped?” The same question is then asked for each of the parts, and a hierarchy of connected concepts is created.
Fishbone diagram
Agree
Disagree
Cost/benefit chart Costs
Tree diagram
Benefits
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Measurement Observations from an experiment may be qualitative (descriptive) or quantitative (physical measurements). Quantitative observations help us to describe such things as how far away something is, how massive it is, and how much space it takes up. Quantitative observations require the use of accurate measurements.
Measurement and Accuracy
B
C
In this illustration, the centre of the dartboard is the true value of the measurement. Player A was neither precise nor accurate; the positions of the shots all differed and none hit the centre. Player B was precise but not accurate; all the darts hit the same area of the target, but they all were off the centre. Player C was both precise and accurate; all the darts are close to one another and in the centre of the target.
Significant Digits Significant digits are the specific number of digits used to communicate the degree of uncertainty in a measurement. The last digit indicates the uncertain (or estimated) digit. The measurement of 2.5 cm for the eraser taken with ruler A below has two significant digits, but the measurement of 2.35 cm taken using ruler B has three significant digits. When a measurement is on a division on a scale, indicate it by including a zero. For example, a length on the 3-cm mark would be recorded as 3.0 cm (two significant digits) on ruler A, and as 3.00 cm (three significant digits) on ruler B. m 1
A
2
cm 1
Whenever you take a measurement, you are making an estimate. There is always an amount of uncertainty in measured values. Counted and defined values are exact numbers and so have no uncertainty. For example, 32 students in a classroom is a counted number, and a length of 1 m is defined as exactly equal to 100 cm. There is no estimation in these values and so no uncertainty. Accuracy is the difference between a measurement and its true value. No matter how carefully you work, there will be a difference between a quantity you measure and its true value. The accuracy of any measurement is affected by the precision of the measurement. Precision refers to the degree of agreement among repeated measurements of the sample (the reproducibility). Precision is determined by your actions; how carefully you take measurements and control the variables in your experiment. The differences between precision and accuracy are illustrated using the example of a darts game.
A
3
2
cm
B
4
3
1
5
4
2
cm 1
5
3
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Example 8.1: Write 0.000 15 mm in scientific
Measuring in SI Most countries and scientific communities have agreed on the use of one system of measurement, making worldwide communication much more efficient. This system is called “le Système international d’unités” or SI for short. SI is based on the metric system. Base units are used, and prefixes are added to change the base units by multiples of ten. Conversion from one unit to another is relatively easy if you know the base units and the meaning of the prefixes. The table below shows the prefixes, their symbols, and their meanings. A kilometre, for example, is equal to 1000 m, and 1 millimetre is 0.001 m or 1 m ⫽ 1000 mm. Common Metric Prefixes
notation. In scientific notation, there must be one digit before the decimal place. So, you need to move the decimal four places to the right and then multiply by 10–4. 0.000 15 mm is written as 1.5 ⫻ 10–4 mm Example 8.2: Write 2.998 ⫻ 108 m/s in
common notation. The power term 108 tells you to move the decimal over 8 places to the right. 2.998 ⫻ 108 m/s is written as 299 800 000 m/s SI Base Units Measurement
Base Unit
Symbol
mass
kilogram
kg
Prefix
Symbol
Meaning
Exponential Form
length
metre
m
temperature
Kelvin
K
giga
G
billion
109
time
second
s
electric current
ampere
A
mega
M
million
106
kilo
k
thousand
103
amount of substance
mole
mol
hecto
h
hundred
102
intensity of light
candela
cd
deca
da
ten
10
deci
d
one tenth
10-1
centi
c
one hundredth
10-2
milli
m
one thousandth
10-3
micro
μ
one millionth
10-6
Scientific Notation Scientific notation is often used to express either very large or very small numbers. It is based on the use of exponents. A number between 1 and 10 is followed by 10 raised to a power.
Converting SI Units It is important to know how to convert from one SI unit to another. The following steps will help you convert between units. 1. Begin by writing the measurement that you want to convert. 2. Multiply by a factor that shows the relationship between the two units you are converting. Write this relationship as a fraction, putting the units you are converting to in the numerator. This will allow you to cancel the given units you started with. Skills Reference 8
Measurement
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3. The conversion may sometimes require two or more steps. (see Example 8.4). This method of solving problems is referred to as unit analysis. Example 8.3: Express 56 cm in metres.
Multiple the number by its conversion factor, and cancel out any repeated units: 56 cm ⫻ 1 m 100 cm When you use a measuring tool such as a ruler, look directly in line with the measurement point, not from an angle. This coin measures 28.0 mm or 2.80 cm.
= 56 m 100 = 0.56 m
Hint
Example 8.4: Express 3200 cm in kilometres.
Multiple the number by its conversion factor, and cancel out any repeated units: 3200 cm ⫻ 1 m ⫻ 1 km 100 cm 1000 m = 3200 km 100 ⫻ 1000 = 0. 3200 km
Length Length indicates the distance between two points. The metre is the base unit for measuring length. Long distances are measured in kilometres (km), and small distances are commonly measured in centimetres (cm) or millimetres (mm). The instrument that you use will determine the number of decimal places in your measurement. The last digit of any measurement is always uncertain.
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Measurement
When you use a ruler, tape measure, or metrestick, always start from the 0 measurement point, not the edge of the measuring tool.
Instant Practice For each of the following, choose the unit of measurement that you think would be used. Explain why you chose that unit of measurement in each case. 1. the height of a table 2. the depth of a lake 3. the width of a dime 4. the length of a skating rink 5. the distance from Ottawa, Ontario, to Victoria, British Columbia
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Volume
Mass and Weight
Volume indicates the amount of space that something takes up (occupies). Common units used to measure volume include litres (L) for liquids and cubic centimetres (cm3) for solids. Remember that 1 mL ⫽ 1 cm3. At home, you often use a measuring cup to determine the volume of something. At school, you usually use a graduated cylinder. Here, “graduated” means a container that has been marked with regular intervals for measuring. For example, a measuring cup, a beaker, and a thermometer are all graduated, but the accuracy of the measurement is different with each measuring instrument or tool.
The terms mass and weight do not mean the same thing, even though they are often used that way. The mass of something tells you the amount of matter it contains. The weight of an object is a measure of the force of gravity acting on it. Common units to measure mass include grams (g) and kilograms (kg). The mass of objects is often measured in grams using different types of balances. You may have a triple beam balance, an equal arm balance, or an electronic scale in your school. The equal arm balance and triple beam balance basically work in the same way. You compare the mass of the object you are measuring with standard or known masses (or their mass equivalent values on the triple beam). An equal arm balance has two pans. You place the object whose mass you want to know on one pan. On the other pan, you place standard (known) masses until the two pans are balanced (level). Then, you just add up the values of the standard masses. The total is the mass of the object you are measuring.
When you add a liquid to a graduated cylinder, the top of the liquid is curved near the sides of the cylinder. This curve is called a meniscus. To measure the liquid’s volume properly, you need to observe the liquid’s surface from eye level so you can see the flat, bottom portion of the curve. Ignore the sides.
Instant Practice 1. Each of the following objects takes up space. Estimate the volume of each, using appropriate units. (a) soccer ball (b) tissue box (c) Olympic swimming pool 2. Explain how you could accurately measure 53 mL of water in the school laboratory.
Equal arm balance
Skills Reference 8
Measurement
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A triple beam balance has a single pan. You place the object you are measuring on the pan. You adjust the masses on the beams until the beam assembly is level. Then, you add up the mass equivalent values of the beam masses from the scales on the beam.
Triple beam balance
Electronic balances allow you to tare (zero) the balance with an object on it. For example, this allows you to ignore the mass of a beaker and measure the mass directly. You do not have to subtract the mass of the beaker.
You can use a spring scale to measure weight, which is the force of gravity acting on an object. A spring scale is sometimes called a force meter and measures force in newtons. A spring scale has three main parts: a hook, a spring, and a measuring scale. The hook at the end is used to attach the object to the scale. The spring pulls on the object. As the spring pulls, the pointer moves along the measuring scale. To measure the weight of an object, first hang the spring scale from a clamp on a retort stand. Then, hang the object from the hook of the spring scale. Once the Spring scale pointer stops moving, record the measurement.
Instant Practice 1. The object on the triple beam balance is a water-filled beaker, so the balance is measuring the mass of the water plus the mass of the beaker. What if you wanted to measure just the mass of the water in the beaker? Describe, step-by-step, how you would do it. 2. How would you measure the mass of an apple? How would this be similar to and different from measuring the mass of a pile of salt?
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Temperature The Celsius temperature scale is commonly used in the metric system, even though the Kelvin degree is the base unit. You will use the Kelvin scale as you learn more about matter in higher grades. Water boils at 100°C and freezes at 0°C.
Estimating It is important to be able to estimate or guess the length, mass, or volume of various objects before you measure. This process will allow you to decide whether your measurements are accurate or if there is instrument error. It will also help you to decide which tool to use. Sometimes, you can estimate by comparing one object with another object that has known measurements. For example, if you are asked to estimate the volume of your drink, you could estimate by comparing it with a large jar of mayonnaise in your fridge, which has its volume marked on the label. For a large object or distance, you might divide it up into portions in your mind and guess the length, volume, or mass of one portion. You then multiply that guess by the number of imaginary portions to estimate the measurement of the whole.
Sometimes, it is useful to estimate the measurement of an object before you actually measure it. You might do this to help you decide which units of measurement and which measuring tool to use. In other cases, you might not be able to measure an object at all. In this case, an estimate of its length, volume, or mass might be the best you can do. Try to estimate the measurements of the items listed below. Include the measurement units that you think should go with your estimates. Then, measure them to see how close your estimates were to the real values. If you don’t have some of these items in your classroom, check at home. Estimating Length Object
Length estimate (cm)
actual value (cm)
pencil height of your teacher’s desk length of your classroom Estimating Mass Object
Mass estimate (g)
actual value (g)
this textbook banana from someone’s lunch piece of chalk Estimating Volume Object
Volume estimate (mL)
actual value (mL)
amount of water poured into an empty jar marker cap To estimate the volume of your drink, you can compare it with the known volume of a jar of mayonnaise.
drink thermos Skills Reference 8
Measurement
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Graphing Science and technology often involve collecting a lot of numerical data. It is important to record these data or observations in an organized, meaningful manner. Data tables are helpful tools for organizing information. Sometimes, however, it’s difficult to see if there are any patterns in the numbers. That’s when it’s useful to reorganize the data into graphs. Graphs help to interpret data collected during an experiment. A graph is similar to a picture or diagram that shows more easily how numbers are related to one another. You have probably drawn a lot of graphs over the years in your studies of mathematics, geography, and, of course, science and technology.
Bar Graphs Bar graphs are useful when you want to analyze the relationship between quantitative data in different categories. For example, the table shows the average monthly precipitation in a Canadian city. In this example, the independent variable is a category, a month, and the depenedent variable is the average precipitation. The graph is created from the data in the table. On a bar graph, the independent variable (e.g., the month) is plotted on the x-axis and the dependent variable (e.g., the average precipitation) is plotted on the y-axis. The x-axis is the horizontal axis, and the y-axis is the vertical axis. The maximum number on the scale of the y-axis is determined by the maximum value in the data set. If all the values in the data set are positive, the minimum number on the scale is usually zero. If the data set contains negative numbers,
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then the minimum value in the data set will be the minimum number on the y-axis. Each category in the data set is drawn as a bar of equal width on the x-axis. The height of each bar is determined by the value of the dependent variable, and it is drawn according to the scale of the y-axis. The graph is given a title, placed at the top of the graph, which describes the information presented. Bar graphs may be drawn by hand using paper and pencil, or using technology such as a graphing calculator or spreadsheet software. As you can see, the changes in the dependent variable are a lot easier to see on the graph than in the table. Average Precipitation per Month Month
Average Precipitation (mm)
Jan
31.1
Feb
17.4
Mar
15.7
Apr
21.2
May
28.6
June
49.9
July
56.2
Aug
50.6
Sept
37.0
Oct
30.9
Nov
28.2
Dec
26.8
Data Source: Environment Canada
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A circle graph is useful when you want to display data that are parts of a whole. For example, in this circle graph, the whole circle represents Earth’s atmosphere and the parts show the percentage of each specific gas. The graph is given a title that describes the information it contains, and each part of the circle is clearly labelled. Circle graphs may be drawn by hand using paper and pencil, or using technology such as a graphing calculator or spreadsheet software.
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Average Precipitation (mm)
Circle Graphs
40
30
20
10
Percentage of Gases in Earth’s Atmosphere 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month
0.97
20.95
78.08
Instant Practice 1. What type of information is a bar graph useful for displaying? 2. Which axis is used to display the independent variable? 3. Refer to the bar graph of Average Precipitation per Month (a) Which month received the greatest amount of precipitation? (b) In how many months did precipitation greater than 30 mm occur? (c) Which season is the wettest? (d) What is the least amount of precipitation that occured in any month of the year?
nitrogen
oxygen
other
Instant Practice 1. What type of information is a circle graph useful for displaying? 2. Refer to the circle graph of the Percentage of Gases in Earth’s Atmosphere. (a) Which gas is present in the greatest amount in the atmosphere? (b) What percentage of the atmosphere is composed of oxygen?
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Graphing
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Line Graphs Line graphs are good for exploring data collected for many types of experiments. Using line graphs is a good way to analyze the data of an experiment that are continually changing. The table shows data collected by a group of students investigating temperature changes. They poured hot water into a large container (container A) and cold water into a smaller container (container B). After recording the starting temperatures in each container, they placed Container B inside Container A and took measurements every 30 s until there were no more temperature changes.
Here are the data the students investigating temperature changes collected shown as a line graph. On the graph, they put the independent variable, time, on the x-axis, and the dependent variable, temperature, on the y-axis. Temperature of Water in Container A and Container B
container A
container B
Temperature of Water in Container A and Container B Time (s)
Temperature (˚C) of Water in Container A
Temperature (˚C) of Water in Container B
0
51
0
30
45
7
60
38
14
90
33
20
120
30
22
150
29
23
180
28
24
210
27
25
240
26
26
270
26
26
300
26
26
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On a line graph, the independent variable is plotted on the x-axis and the dependent variable is plotted on the y-axis. Each axis must be clearly marked with a scale, which must take into account the entire range of measurements to be plotted and use up at least half the size of the graph paper used. The maximum and minimum numbers of the data determine the maximum and minimum numbers on the scales of the axes. Each piece of data in the table is then plotted by moving over to the correct position on the x-axis and up to the correct position on the y-axis. A point is placed at the intersection of these two positions. If two or more sets of data are plotted on one graph, different colours or shapes are used to plot the different data sets and a legend is provided to explain the colours or shapes. When the line graph is completed, it is given a title that describes the information
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Combining Different Types of Graphs In some cases, two different types of data may be combined on one graph. There are two vertical axes, as shown in the graph. The vertical axis on the left presents the scale for the precipitation data, and the vertical axis on the right presents the scale for the temperature data.
40
15
35
10
30
5
25
0
20
-5
15
-10
10
-15
5
-20 -25
0
Instant Practice 1. The axes are the two number lines that run horizontally and vertically. Which is the x-axis, and which is the y-axis? Which axis is used for the independent variable? Which is used for the dependent variable? 2. How was the scale for each axis chosen? 3. How was each point on the graph plotted (placed on the graph)?
Average Temperature (°C)
Average Precipitation and Temperature per Month
Average Precipitation (mm)
presented. Line graphs may be drawn by hand using paper and pencil, or using technology such as a graphing calculator or spreadsheet software. Always look for a pattern on the graph after the individual points are plotted and before you connect the points. If you observe a pattern, draw a “line of best fit” with the points evenly located either on or around the line. This process is called interpolation. If there is more than one line on the graph, you will need a legend to explain what each line represents. Extrapolation is used in graphing to make predictions. When you extrapolate, you extend the line you obtained from your experimental data to show the relationship between the data for values that were not experimentally determined. This assumes that the trend that was observed will continue further, which is not always the case.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
average precipitation
average temperature
Source: Environment Canada
Instant Practice 1. Why is it useful to combine a precipitation graph and a temperature graph together? 2. In the combined graph of Average Precipitation and Temperature per Month, how do you determine whether the red line refers to precipitation or temperature?
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Graphing
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Using a Microscope A microscope allows us to see an image of an object that is too small to see with the unaided human eye. A light microscope functions by focussing a beam of light through the object into the lens of the microscope. A compound light microscope is any light microscope that contains more than one lens. The compound light microscope you will use in the science classroom contains an eyepiece lens and a number of objective lenses. Each objective lens is a combination of two lenses made of different kinds of glass.
The Parts of the Microscope It is important to know the location and function of the parts of the microscope in order to use it correctly. These are shown below.
Tube
Eyepiece or ocular lens
Using the Microscope 1. Carry the microscope with two hands, grasping the arm of the microscope with one hand and holding the base of the microscope with the other. Place the microscope on the table or bench so that the arm is facing you. 2. Plug in the microscope, and turn on the light. 3. Rotate the nosepiece until the objective lens with the lowest power is in place. 4. Place a microscope slide on the stage, and secure with the stage clips. 5. Watch the stage from one side of the microscope, and slowly raise the stage with the coarse adjustment until it is as close to the nosepiece as possible without touching it. Ensure the lens does not touch the slide. 6. Look through the eyepiece. Slowly turn the coarse adjustment so that you move the slide away from the lens. Stop when the image comes into view. 7. Use the fine adjustment to sharpen the focus of the image. 8. If you need to view the object under higher magnification, watch from the side of the microscope and rotate the nosepiece until the next higher power objective lens is in place. Ensure the lens does not touch the slide. Use only the fine adjustment knob to focus the image.
Revolving nosepiece Arm
Magnification and Field of View
Objective lenses
Stage clips Stage Diaphragm Condenser lens Lamp
Coarse adjustment knob Fine adjustment knob
Each lens on the compound microscope will magnify a sample to a different degree. Magnification is calculated by multiplying the power of the ocular lens (usually 10× power) by the magnification of the objective lens you are using. magnification = (power of ocular lens)(power of objective lens)
Base
A compound light microscope
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For example, if you are viewing a slide using a 4× power objective lens, the magnification of the image would be (10×)(4×) = 40×.
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The field of view is the entire area that you see when you look through the microscope. The diameter of the field of view varies with the particular objective lens you are using. The diameters of the field of view for low-power (4×) and medium-power (10×) objective lenses can be determined by the following steps: 1. Rotate the objective lens into position. 2. Place a small, transparent, metric ruler on the stage so that it covers about half the stage. The ruler must be small enough to fit on the stage. 3. Using the coarse adjustment knob, bring the ruler into focus. Adjust the placement of the ruler so that the scale crosses the centre of the circle (the diameter), as shown below. 4. Use the fine adjustment knob to get a clear, sharp image. If necessary, adjust the ruler so that one of the markings on the left side is exactly at the edge of the diameter.
view is less than 1 mm. However, you can estimate the diameter of the field of view of a high-power objective lens by using ratios. As you increase magnification by a certain amount, you decrease the diameter of the field of view by the inverse of that amount. Therefore, you can determine the diameter of the field of view of a high-power (HP) objective lens by using the following ratio: HP field diameter= LP magnification LP field diameter HP magnification
Example 10.1 A student measured the field diameter of a microscope using the 4× and 10× objective lenses. Objective Lens
Magnification of Objective Lens
Field Diameter (mm)
Field Diameter (µm)
low power
4×
4.5
4500 or 4.5 × 103
medium power
10×
1.1
1100 or 1.1 × 103
Calculate the field diameter of a high-power (40×) objective lens. HP field diameter LP magnification = LP field diameter HP magnification HP field diameter = LP field diameter × = 4500 µm ×
LP magnification HP magnification
(4×) (40×)
= 450 µm Step 4
5. Determine the diameter of the field of view in millimetres, using the scale on the ruler. Convert the millimetre reading to micrometres. This is the field of view for the magnification used.
You cannot measure the diameter of the field of view of a high-power (40×) objective lens using this method, because the field of
= 4.5 × 102 µm The field diameter of the high-power (40×) objective lens is 4.5 × 102 µm.
Note that when the magnification increases by a factor of 10, such as from 4× to 40×, the field diameter decreases by the same factor (10×), from 4500 µm to 450 µm. Skills Reference 10
Using a Microscope
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Once you have estimated the diameter of the field of view of an objective lens, you can estimate the size of any structure you are viewing with that lens. Compare the size of the structure with the diameter of the field of view.
Preparing a Wet Mount 1. Obtain a clean microscope slide and cover slip. In a wet mount, the cover slip serves three functions: it flattens the sample, it prevents the sample from drying out, and it protects the objective lens from contamination. 2. Place your sample in the centre of the slide. The specimen must be thin enough for light to pass through. 3. With an eyedropper, place a drop of water on the sample, as shown.
water droplet sample
slide
Step 3
4. Place the cover slip at an angle at one end of the drop of water. See below. Carefully lower the cover slip to cover the sample, being careful not to trap any air. It may be helpful to use a probe or toothpick to lower the cover slip. cover slip sample in water droplet
slide
Step 4
5. If you do get air bubbles, gently tap the slide with a probe to release them, see below.
1. Prepare a wet mount slide, as described at left. 2. Place a drop of stain at the edge of one side of the cover slip. 3. Obtain a small piece of paper towel or tissue paper. Place the paper against the edge of the cover slip on the side opposite to the stain, as shown below. paper drop of stain wet mount of sample
Step 3
4. Allow the paper to wick the fluid from under the cover slip and draw the stain into the sample, as shown below. paper stain pulled under cover slip
Step 4
cover slip sample in water droplet
slide
Skills Reference 10
The parts of a cell are composed of various substances, and the different cell components react differently to many chemicals. Stains are chemicals that react in specific ways to different cell components. Stains therefore make it easier to distinguish the components of a cell. Some stains will dye only certain parts of the cell. Others change colour depending on the substances that comprise the different cell components. There are many ways to stain cells, but one of the most common is the flow technique. This technique may be used to stain cells with, for example, iodine or methylene blue. The flow technique consists of the following steps:
wet mount of sample
probe
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Staining Samples
Using a Microscope
Step 5
5. Remove the paper when the stain has travelled to the other side of the cover slip. 6. If the stain is too dark, it may be diluted by repeating steps 2 to 5 with a drop of water.
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Drawing Scientific Diagrams To record what you observe under a microscope, you will often draw a scientific diagram. Scientific diagrams can also be used to record observations not made with a microscope. For example, they may also be used to show how equipment is set up for an experiment or to record objects observed with the unaided eye. A scientific diagram is a record of exactly what was observed, with all features accurately drawn and identified. Guidelines for Drawing Scientific Diagrams 1. Give a title for your diagram at the top of the page. The title should include information about the object shown. 2. Use pencil. Do not colour diagrams. Shade areas if necessary. 3. Draw only one diagram on a page unless otherwise instructed by your teacher. 4. Label the parts or structures of the object on the diagram. Use a ruler to draw lines to connect the label to the part or structure. 5. Record the scale of the drawing at the side of the diagram.
can be prepared as a cross-section (across the width) or as a longitudinal section (lengthwise), as below. Longitudinal Section of Plant Stem companion cell
This longitudinal view of a plant stem shows different features of the plant stem from those shown in a cross-section.
sieve tube cell
Diagrams may be drawn larger, smaller, or the same size as the actual object. The scale of a diagram is the difference between the size of the diagram and the size of the actual object. Scale is often expressed as a ratio, such as in the examples in the table. Actual Size, Diagram Size, and Scale Actual Size
Diagram Size
Scale
1.1 mm
11 cm (110 mm)
100:1 (or × 100)
2.6 m
2.6 cm
1:100 (or × 0.01)
Cross-Section of Plant Stem
epidermis
vascular bundle
ground tissue
xylem phloem scale 10:1
This example of a scientific diagram shows the features of a cross-sectional view of a plant stem.
When samples have been dissected (cut apart), it is important to note how they were prepared in the title of the diagram. A sample
When using a microscope, the actual size of the object is usually estimated by comparing it to the diameter of the field of view. To calculate actual size and scale for a scientific diagram, you must first measure the field diameter (if you are using a microscope) and the size of the finished diagram. Actual size and scale can then be calculated using the following relationships: actual size field diameter of object = number of objects estimated to fit across field scale =
diagram size of objects (units) actual size (units)
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Using a Microscope
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Chemistry Backgrounder The tables provided here are designed to help you in your study of chemistry. Common Elements and Compounds Common Name
Scientific Name
Chemical Formula
Main Uses
Acetic acid
ethanoic acid
CH3COOH(aq)
vinegar
Ammonia water
ammonia
NH3(aq)
cleansers, deodorizers, etching of aluminum
ASA
acetylsalicylic acid
CH3COOC6H4COOH(s)
pain reliever
Baking soda
sodium hydrogen carbonate
NaHCO3(s)
raising agent in food
Bath salt
magnesium sulphate
MgSO4(s)
improve cleaning
Battery acid
sulphuric acid
H2SO4(aq)
car batteries
Household bleach
sodium hypochlorite
NaOCl(aq)
laundry bleach
Glucose
glucose
C6H12O6(s)
energy source for organisms
Grain alcohol
ethanol
CH3CH2OH(ᐉ ) C2H5OH(ᐉ )
solvent, for manufacture of medicines, gasoline
Lime
calcium oxide
CaO(s)
mortar, steel and glass making, smokestack scrubbers
Limestone
calcium carbonate
CaCO3(s)
cement and mortar, chalk, marble
Milk of magnesia
magnesium hydroxide
Mg(OH)2(s)
antacid medication
MSG
monosodium glutamate
C5H8NO4Na(s)
flavour enhancer
Muriatic acid
hydrochloric acid
HCl(aq)
tile cleaner, etching of masonry and marble surfaces
Natural gas
methane
CH4(g)
fuel
PCBs
polychlorinated biphenyls
C12H10-nCln(ᐉ )
electrical transformers
Peroxide
hydrogen peroxide
H2O2(aq)
antiseptic, disinfectant, bleaching agent
Potash
potassium chloride
KCl(s)
fertilizer
Road salt
calcium chloride
CaCl2(s)
de-icing and dust control of roads
Silver nitrate
silver nitrate
AgNO3(s)
antiseptic, photography, treatment of warts
Soda ash
sodium carbonate
Na2CO3(s)
glass, paper, and detergent production
Sugar
sucrose
C12H22O11(s)
sweetener, preservative, food for yeast
Table salt
sodium chloride
NaCl(s)
flavour
Vitamin C
ascorbic acid
C6H8O6(s)
production of connective tissue, antioxidant
Water
water
H2O(ᐉ )
universal solvent, vital component of all organisms
Wood alcohol
methanol
CH3OH(ᐉ )
antifreeze
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Diagnostic Tests for Some Common Substances Substance Detected
Description of Test
oxygen gas
Collect a small amount of gas in a test tube. Insert a glowing wooden splint into the test tube. If oxygen gas is present, the splint will ignite and you will see a flame.
hydrogen gas
Collect a small amount of gas in a test tube. Insert a burning wooden splint into the test tube. If hydrogen gas is present, you will hear a popping sound.
carbon dioxide gas
Collect a small amount of gas in a test tube. Insert a burning wooden splint into the test tube. If carbon dioxide gas is present, the flame will be extinguished (go out). Since other gases can also extinguish the flame, the presence of carbon dioxide must be confirmed by testing it with limewater (a solution of calcium hydroxide). Place a few drops of limewater into the test tube. If the gas is carbon dioxide, the limewater will turn milky.
bases
Dip a piece of red litmus paper into the solution. If the solution is a base (i.e., it has a pH > 7), the litmus paper will turn blue.
acids
Dip a piece of blue litmus paper into the solution. If the solution is an acid (i.e., it has a pH < 7), the litmus paper will turn red. Alternatively, add a drop of phenolphthalein indicator. If the solution is acidic, the indicator will be colourless or red. If the solution is not acidic, the indicator will be pink.
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Chemistry Backgrounder
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Common Polyatomic Ions
Electron Arrangements of the First 20 Elements
Polyatomic Ion
Formula
acetate
CH3COO–
ammonium
NH4+
borate
BO33–
carbonate
CO32–
hydrogen carbonate (bicarbonate)
HCO3
chlorate
ClO3–
chlorite
ClO2–
hypochlorite
ClO–
–
2–
chromate
CrO4
dichromate
Cr2O72–
Atoms H
He Li
1p
2p 3p
Ions H+
1p
0
H–
1p
2
2
He
does not form an ion
2, 1
Li+
3p
2
4p
2
1
Be
4p
2, 2
Be2+
B
5p
2, 3
B3+
5p
2
C
6p
2, 4
C4–
6p
2, 8
N
7p
2, 5
N3–
7p
2, 8
O
8p
2, 6
O2–
8p
2, 8
F
9p
2, 7
F–
9p
2, 8
Ne
10 p
2, 8
Ne
does not form an ion
2, 8, 1
Na+
11 p
2, 8
12 p
2, 8
Na
11 p
cyanide
CN–
Mg
12 p
2, 8, 2
Mg2+
hydroxide
OH–
Al
13 p
2, 8, 3
Al3+
13 p
2, 8
nitrate
NO3–
Si
14 p
2, 8, 4
Si4–
14 p
2, 8, 8
nitrite
NO2–
P
15 p
2, 8, 5
P3–
15 p
2, 8, 8
perchlorate
ClO4–
S
16 p
2, 8, 6
S2–
16 p
2, 8, 8
MnO4–
17 p
2, 8, 8
permanganate peroxide
O22–
phosphate
PO43–
17 p
2, 8, 7
Ar
18 p
2, 8, 8
Ar
does not form an ion
2, 8, 8, 1
K+
19 p
2, 8, 8
2, 8, 8, 2
Ca2+
20 p
2, 8, 8
K Ca
3–
phosphite
PO3
silicate
SiO32–
sulphate
SO42–
hydrogen sulphate
HSO4–
sulphite
SO32–
hydrogen sulphite
HSO3–
hydrogen sulphide
HS–
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Cl
Cl–
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Chemistry Backgrounder
19 p 20 p
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Using a Star Chart The Star Chart shown here will help you identify stars in the night sky.
NORTH The Big Dipper
Mizar & Alcor
SA UR OR J MA
Thuban M1
3
N
W
CO LA
E
PO
DRA
“ TO
N
RI S”
URSA MINOR
n
H
AR
am i
ST
CU
ν
H
ER
M81
M82
RT
LE
S
2
O E N
M9
TH
LY N X
Et
NCP
CA
ME
LO
CASSIOPEIA
le ub r Do uste Cl
61
η
N
AQUILA
A
Algol
D ED A
U
γ S
Enif
IE
M15
S SU
R
es
GA
A
l ma Ha
Hy a d
n
σ
PE
s
bara
Alde
S
Pleiade
RU
η
M
M31
RO
γ
TA Cr 69
ORION
Betelgeuse
OS
Sq ua re G re at su s of Pe ga
WEST
M27
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M1
2244
3
γ
Altair
IS
PE
M38 M36
M37
Cr 399
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9
δ
M3
eo Albir
AL
μ
ape lla
GA
C
RI
M35
2264
DELPHINUS
RD
AU
NI
CYGN
US
PA
EM I
M5
7
β
CEPHEUS
G
IC
β
PT
LY
ε
yr RL
RA
g Ve
a
Polaris
LI
G De emin c 1 id 3– s 14
x
ast or
C
Pol lu
EC
M42
M2
PISCES
rc
US
le
t
el Rig
PU
TU
09 70
UA
CE
AQ
LE
Mir a
RI
Ci
S
S
ER O
S IC
93
us
Symbols
PR
72
Ve n
U
RN
N
U
A
S
ID
Diphda
CA
S E
FO
SCULPTOR
RN
AX
al Fom
W
253
α
t hau
S
2232 β
MONOCER
EAST
M3
IS S SC NU PI TRI S AU
θ PHOENIX
SOUTH
Galaxy Double Star Variable Star Diffuse Nebula Planetary Nebula Open Star Cluster Globular Star Cluster
Star Magnitudes
Skills Reference 12
-1
0
Using a Star Chart
1
2
3
551
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Electricity Backgrounder The table below is a handy reference for drawing electrical circuits. Remember that
electricity is dangerous — be very careful when you use electricity at home or in the lab.
Symbols Used in Circuit Diagrams Symbol
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Represents
Description
ammeter
measures amount of current in circuit
battery
combination of cells
capacitor
stores electricity and regulates current
cell
stores electricity (long bar is positive)
conductor (wire)
conducts electricity through circuit
connection
shows connection between wires in a circuit
diode
converts alternating current (AC) to direct current (DC); only allows current to flow in one direction
fuse
melts if current is too high
lamp
converts electricity to light
LED (light emitting diode)
diode that emits light (usually red) when current flows
motor
converts electricity to mechanical energy
photoconductor
allows current to flow when exposed to radiant energy (e.g., light, infrared)
resistor
reduces the amount of current in the circuit
rheostat
variable resistor
speaker
converts electrical energy into sound energy
switch
opens and closes circuit; allows current to flow
voltmeter
measures voltage across a device in circuit
Electricity Backgrounder
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Skills Reference 13
Electrical Safety in the Lab • Handle batteries carefully because they contain acids or bases that can cause corrosive burns. • Do not connect the two battery terminals with a wire or you will create a short circuit. • Do not use bare connecting wires. • Have your teacher check the circuit before you close the switch or connect the power source. • Disconnect or turn off the power source before you connect wires in a circuit. • Wear safety goggles when working with liquid electrolytes.
Measuring Current and Voltage Current is measured using an ammeter while voltage is measured with a voltmeter. These devices are either digital display or analog display. Digital display meters show measurements as numbers, just as in a digital clock. Digital meters that combine both voltage and current measurements into one device are called multimeters. Analog meters use one or more dials and a pointing needle.
Reading an Ammeter Before an ammeter can be used, it must be correctly connected to the circuit. Since an ammeter measures the flow of electric current, it must be made part of the circuit so that the electric current will pass through it. To connect the ammeter, disconnect the circuit at the point where you wish to make a measurement and attach the wires so that the (+) side of the power source connects to the red terminal on the meter and the (–) side of the power source connects to the black terminal on the meter. Reading a digital ammeter is straightforward, as the display will show the values directly. It may be possible to adjust the display to give more or fewer decimal places as desired. Reading an analog display ammeter involves noting the position of a pointer on a dial and reading the values from it. Many ammeters have two or even three scales. The choice of which scale is used is usually determined by which terminals on the ammeter are used to connect it into the circuit.
.2 1
.4 2
.6 3
.8 4 5
0
0
1
Amperes D.C.
Analog ammeters and voltmeters use a pointer and a set of different scales.
500 mA
1A
100 mA
5A
10 mA
10 A
The ammeter above is connected using the 100-mA scale. This means that a full scale deflection of the pointer is 100 mA. Use the scale that has a full scale deflection of 1. This is 100 mA. Since the pointer is at 0.72, the reading is 0.72 mA. Skills Reference 13
Electricity Backgrounder
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Skills Reference 13
Reading a Voltmeter
Instant Practice 1. Read the following meters and write their readings. (a) .6 .4 .2 1 0 0
500 mA
1A
100 mA
5A
10 mA
10 A
(b) .2 1 0
Amperes D.C.
0
500 mA
1A
100 mA
5A
10 mA
10 A
(c) .2 1
0 0
1V
The voltmeter above is connected using the 5-V scale. This means that a full scale deflection of the pointer is 5 V. Use the scale that has a full scale deflection of 5. Since the pointer is at 3.9, the reading is 3.9 V. 554
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Electricity Backgrounder
.8 4
0
VOLTS D.C.
0
10 V
50 V
5V
100 V
1V
(d) .2 1
.4 2
.6 3
.8 4
0
VOLTS D.C.
0
5
100 V
.6 3
1
50 V
5V
.4 2
5
5
10 V
.8 4
1
1
VOLTS D.C.
.6 3
5
.8 4
.4 2
1
.6 3
.8 4
5
.4 2
3
Amperes D.C.
10 V
50 V
5V
100 V
1V
.2 1
2
1
Before a voltmeter can be used, it must be correctly connected to the circuit. A voltmeter is used to detect the change in voltage across a device inside a circuit such as a resistor, light bulb, or dry cell. Do not disconnect any part of the circuit in order to connect a voltmeter. Connect two wires from the voltmeter to either side of the dry cell or other device where the voltage measurement is to be taken. Attach the wires so that the (+) side of the power source is closest to the wire from the red terminal on the meter and the (–) side of the power source is closest to the wire from the black terminal on the meter. Reading a digital voltmeter is straightforward, as the display will show the values directly. It may be possible to adjust the display to give more or fewer decimal places as desired. Reading an analog display voltmeter involves noting the position of a pointer on a dial and reading the values from it. Like ammeters, many voltmeters have two or even three scales. The choice of scale used is usually determined by which terminals on the voltmeter are used to connect it into the circuit. Sometimes, a dial is used to select the appropriate scale, as in the example below.
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Answers to Numerical Questions page 127, Unit A Review 35. (a) 520 000 kJ/m2 (b) 520 kJ/m2 page 177, 5.1 Check and Reflect 11. (a) 9 (b) 9 page 183, Learning Checkpoint 4. (a) N (b) Ni (c) Pb page 187, 5.2 Check and Reflect 2. (a) mercury, Hg and bromine, Br (b) metal (mercury) and nonmetal (bromine) 3. (a) germanium, Ge (b) rubidium, Rb (c) helium, He (d) iodine, I (e) hydrogen, H (f) oxygen, O (g) carbon, C (h) chromium, Cr (i) mercury, Hg (j) fluorine, F 4. (a) sodium, Na (b) iron, Fe (c) silver, Ag (d) lead, Pb 5. (a) for example, Cl, C, Ca, Cr, Cu (b) for example, germanium, magnesium, copper (c) He, Ne, Ar, Cl, Br 6. S, Si, Ag 8. (a) for example, iron and carbon (b) hydrogen and oxygen (c) sodium and chlorine page 190, Learning Checkpoint 1. (a) 6 (b) 8 (c) 11 (d) 14 (e) 16 (f) 17 (g) 26
2. (a) 3 (b) 7 (c) 9 (d) 13 (e) 29 (f) 79 3. (a) hydrogen (b) helium (c) neon (d) potassium (e) calcium (f) gallium (g) silver page 193, Learning Checkpoint 1. (a) 1.01 amu (b) 4.00 amu (c) 14.01 amu (d) 19.00 amu (e) 32.07 amu (f) 40.08 amu (g) 107.87 amu 2. (a) carbon (b) oxygen (c) potassium (d) krypton 3. (a) 1+ (b) 2+ (c) 3– (d) 2– (e) 3+ (f) 1– page 195, Learning Checkpoint 1. (a) sodium, Na (b) boron, B (c) copper, Cu (d) iodine, I 2. (a) Period 3, Group 2 (b) Period 3, Group 14 (c) Period 3, Group 17 (d) Period 1, Group 18 (e) Period 6, Group 11 (f) Period 6, Group 14 page 199, Learning Checkpoint 1. (a) 1 (b) 3 (c) 4 (d) 6 (e) 7
2. (a) 1 (b) 2 (c) 5 (d) 8 page 204, 5.3 Check and Reflect 1. (a) Na (b) mercury (c) silicon (d) potassium 4. halogens 7. (a) F (d) S 10. (a) helium (b) 2 (c) 2 (d) Group 18, noble gases 11. (b) gallium and germanium 12. Group 1, alkali metals page 206, Chapter 5 Review 2. Relative Particle Charge Location Mass electron 1– shells tiny (1) neutron 0 nucleus large (1837) 3. 2, 8, 8 5. (a) plumbum (b) Pb 6. for example, carbon, phosphorus, sulphur, selenium 8. (a) technetium (b) dysprosium 9. (a) 4 (b) 2 (c) helium 16. (d) germanium page 213, Learning Checkpoint 2. metal and non-metal page 217, 6.1 Check and Reflect 6. (a) 3 (b) 2 9. (a) Bohr diagram (b) ionic compound (c) magnesium and oxygen
Answers to Numerical Questions
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Answers to Numerical Questions page 220, Learning Checkpoint 3. (a) 2+, Ca2+, calcium ion (b) 1–, Cl–, chloride (c) 3–, P3–, phosphide (d) 3+, Au3+, gold(III) and 1+, Au+, gold(I) (e) 4+, Sn4+, tin (IV) and 2+, Sn2+, tin (II) page 221, Practice Problems 1. sodium fluoride 2. potassium iodide 3. magnesium chloride 4. aluminum chloride 5. calcium phosphide page 222, Practice Problems 1. iron(III) chloride 2. lead(IV) oxide 3. nickel(III) sulphide 4. copper(II) fluoride 5. chromium(III) sulphide page 223, Practice Problems 1. potassium hydroxide 2. zinc carbonate 3. magnesium phosphate 4. calcium sulphate 5. aluminum carbonate page 224, Practice Problems 1. LiBr 2. MgF2 3. Ag3N 4. FeCl3 5. Cr2S3 page 225, Practice Problems 1. Al(OH)3 2. CaSO4 3. Na2CO3 4. Fe2(CO3)3 5. CuSO4 page 226, Practice Problems 1. carbon monoxide 2. carbon tetraiodide 3. oxygen difluoride 4. dinitrogen tetraoxide 5. phosphorus trichloride
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page 227, Practice Problems 1. CO2 2. OF2 3. NF3 4. PF5 5. N2O3 page 229, 6.2 Check and Reflect 1. (a) atom (b) molecular compound (c) ion (d) atom (e) molecular compound (f) ionic compound (g) molecular compound 2. (a) Li+ (b) Sr2+ (c) V4+, V5+ (d) Cl– (e) S2– 3. (a) lithium oxide (b) calcium fluoride (c) potassium fluoride (d) sodium nitride (e) magnesium hydroxide (f) iron(II) chloride (g) aluminum sulphate 4. (a) MgCl2 (b) Na2S (c) Ca3P2 (d) K3N (e) CaF2 (f) Al 2O3 5. (a) NI3 (b) CO2 (c) SF6 (d) CH4 (e) C12H22O11 6. (a) carbon tetrabromide (b) nitrogen monoxide (c) oxygen difluoride (d) iodine dibromide (e) phosphorus trichloride (f) dinitrogen trioxide 9. (c) hydrogen peroxide page 240, Chapter 6 Review 2. (a) hydrogen and oxygen, 1:1 (b) molecular compound
3. (a) N3– (b) Li+ (c) Al3+ (d) O2– (e) Cl– (f) Na+ (g) does not form ions (h) Cu2+, Cu3+ 4. (a) potassium iodide (b) calcium chloride (c) aluminum bromide 5. (a) Li3N (b) FeCl2 (c) NaOH 6. (a) phosphorus pentafluoride (b) dichlorine trioxide (c) carbon tetrafluoride 7. (a) NO (b) CS2 (c) PBr3 10. (a) Mg(OH)2 (b) Na2CO3 (c) Al2(SO4)3 (d) cesium hydrogen carbonate (e) barium carbonate (f) potassium sulphate page 246, Unit B Review 16. (a) 1 (b) 3 (c) 4 (d) 6 (e) 7 17. (a) calcium (b) Group 2, alkaline earth metals (c) 2+ (d) 20 21. (a) lithium and chlorine, 1:1 (b) aluminum and sulphur, 2:3 (c) silver and fluorine, 1:1 (d) zinc and oxygen, 1:1 (e) nitrogen and sulphur, 2:3 (f) bromine 22. (a) ionic compound (b) ionic compound (c) ionic compound (d) ionic compound (e) molecular compound (f) neither (element)
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Answers to Numerical Questions 33. (a) does not normally form ions (b) Ba2+ (c) Be2+ (d) does not form ions (e) Pb2+ or Pb4+ (f) Se2– 38. (a) potassium chloride (d) MgO 57. (a) magnesium bromide (b) barium nitride (c) calcium phosphide (d) aluminum oxide (e) sodium iodide (f) calcium chloride (g) potassium carbonate (h) magnesium sulphate (i) cesium hydrogen carbonate 58. (a) ionic, Mg3P2 (b) ionic, Li3N (c) molecular, PCl5 (d) ionic, AlBr3 (e) ionic, CaS (f) molecular, SO2 (g) ionic, KI (h) ionic, Na2O (i) ionic, Ca(OH)2 (j) ionic, Al(HCO3)3 (k) molecular, NCl3 59. See answer at bottom of page. page 265, C3 Just-in-Time Math 1. 4 ⫻ 1013 2. 1.5 ⫻ 1011 3. 1.3 ⫻ 1010 4. 1.525 ⫻ 105 5. 1.99 ⫻ 1030 6. 4.55 ⫻ 109
page 267, 7.1 Check and Reflect 12. (a) 17.1 years (b) 513 years 13. 130 years page 275, C6 Just-in-Time Math 1. 15 cm 2. 41.6 cm 3. 46.4 cm page 277, 7.2 Check and Reflect 2. 100 000 ly in diameter; 2000 ly thick 3. about 35 000 years page 321, 8.2 Check and Reflect 2. (a) 5 billion years (b) 5 billion years 4. 100 000 years page 331, 8.3 Check and Reflect 1. 1 day 2. 1 year page 382, Unit C Review 56. (a) 9 ⫻ 1013 (b) 1.5 ⫻ 1011 (c) 2.48 ⫻ 107 57. (b) 10 000 times (c) 6000°C
page 461 (top), Practice Problems 1. 2.5 A 2. 0.2 A 3. 0.067 A page 461 (bottom), Practice Problems 1. 4 ⍀ 2. 192 ⍀ 3. 600 ⍀ page 467, 11.3 Check and Reflect 3. V I R 0.5 V 0.01 A 50 ⍀ 2000 V 20 A 100 ⍀ 6.0 V 4.0 A 1.5 ⍀ 8. 2 ⍀ 9. (a) 0.5 A (b) 0.25 A 10. (a) 0.125 A (b) 1.5 V across the 12-⍀ bulb and 4.5 V across the 36-⍀ bulb page 470, Chapter 11 Review 1. (c) 5.0 V (d) 3.0 A 8. 45 V 9. 12 ⍀ 10. (a) 1 600 000 V (b) 1.5 kW (c) 0.650 A 11. (a) 3000 ⍀
page 460, Practice Problems 1. 45 V 2. 9.0 V 3. 120 V
Answer to question 59, page 246 Symbol
Name
Atomic Mass
Protons in Atom
Electrons in Atom
H
hydrogen
1.01
1
1
Cl
chlorine
35.45
17
17
Ca
calcium
40.08
20
20
Ag
silver
107.87
47
47
Ne
neon
U
uranium
20.18
10
10
238.03
92
92 Answers to Numerical Questions
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Answers to Numerical Questions page 492, Learning Checkpoint 1.
Average Use
kW•h
Cost
Appliance
hours (per day)
(per year)
($)
Vacuum cleaner
0.1
38
3.23
Hair dryer
0.25
100
8.50
Computer
4.0
520
44.20
Central air conditioning
12 (60 days/year)
1500
127.50
page 493, Practice Problems 1. 22% 2. 22% 3. 88% page 500, 12.2 Check and Reflect 4. (a) $0.06 (b) $0.02 (c) $0.60 7. 34% page 502, Chapter 12 Review 6. 0.5 kW•h 7. (a) 61% (b) 38% 10. (a) 900 kW•h/y (b) 898 kW•h
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page 507, Unit D Review 21. (a) 6.0 V (b) 2.0 A 22. (a) 3.0 V (b) 1 A 57. 3000 ⍀ 58. (a) 7.5 V (b) 4 A (c) 0.05 ⍀ 59. Voltage Current (V) (A) 2.0 0.017 4.0 0.033 6.0 0.050 8.0 0.067 10.0 0.083
60. (a) 1 600 000 V (b) 1.5 kV (c) 0.65 A 62. Device
Input Output Energy Energy (kJ) (kJ)
Gaspowered SUV 675 81 Gaselectric hybrid car 675 195 Natural gas furnace 110 000 85 000 Electric baseboard heater 9.5 6.0 Alkaline dry cell 84.52 74.38
Percent Efficiency
12%
29%
77%
63% 88%
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Notes: The numbers in parentheses at the end of each definition indicates the page number in this book where the term is defined. A pronunciation guide, using the key below, appears in square brackets after selected words. Stressed syllables are capitalized.
atom smallest part of an element that has all of the element’s properties (168)
a = cat, back ae = day, lake ah = barn, large aw = lawn, not e = wet, ten ee = tree, steam ih = mine, light
atomic number number of protons in an atom of an element (190)
i = ditch, mitt oh = go, phone oo = room, true u = fun, done uh = taken, sun uhr = fur, burn
A abiotic [ae-bih-AW-tik] non-living; physical things, such as rocks, air, and water, or things that are measured, such as air temperature, hours of daylight, and salt concentration in seawater (13) acid rain rain that contains acids formed from nitrogen- and sulphur-containing emissions (70) acidity abiotic factor that is connected to the chemical environment of soil (74) adhesion property of sticking to other substances; a physical property of water (150) alternating current (AC) electric current that flows back and forth at regular intervals called cycles (439) ammeter [A-mee-tuhr] device used to measure the current in a circuit (439) ampere (A) [AM-per] unit of electric current; a measure of the amount of charge moving past a point in the circuit every second (439) aquatic water-based (17) aquifer large underground lake (25) artificial satellite a device placed in orbit around Earth or other celestial object (356) asterisms [A-stu-riz-ums] smaller recognizable star patterns within a larger constellation (294) asteroid belt region of rocky debris that forms a ring all the way around the Sun at a distance of about 3 AU (262)
atomic mass average mass of an element’s atoms (192) atomic mass units (amu) measure of an atom’s mass (192)
atomic theory study of the nature of atoms and how they combine to form all types of matter (170) aurora borealis [uh-ROR-uh bor-ee-A-luhs] display of green, yellow, and red light in the night sky near Earth’s northern regions, produced when the charged particles of the solar wind collide with the atoms and molecules in Earth’s atmosphere (312)
B battery combination of electrochemical cells (435) bedrock solid rock layer under the subsoil (72) Big Bang theory theory that the universe formed when an infinitely dense point suddenly and rapidly expanded in a single moment 13.7 billion years ago (280) binary system star system with two stars (263) bioaccumulation [bih-oh-a-kyoo-myoo-LAE-shuhn] gradual build-up of chemicals in an organism’s body (79) biodiversity [bih-o-di-VUHR-si-tee] number of different types of organisms in an area (9) biological oxygen demand (BOD) measure of how quickly oxygen is used up by micro-organisms in a given body of water (77) biomagnification increase in concentration of a harmful substance at each link in the food chain as one animal eats many contaminated animals (79) biomass [BIH-oh-mas] organic material made up of plant and animal waste (478) biome [BIH-ohm] large geographical region that contains similar ecosystems (16) biosphere part of our planet, including water, land, and air, where life exists. Biomes combine to form the biosphere. (18)
astronomer person who studies astronomy (258)
biotic [bih-AW-tik] living, biotic factors are organisms such as animals, plants, mushrooms, bacteria, and algae (13)
astronomical phenomenon [AS-troh-NAWM-i-kul fen-AWMe-nun] any observable occurrence relating to astronomy (294)
black hole region of space where gravity is so strong that nothing, not even light, can escape (270)
astronomical unit (AU) distance measure; 1 AU equals the average distance between the Sun and Earth, about 150 million km (261)
boiling point temperature at which a liquid turns to a gas (139)
astronomy study of the universe and the objects in it (258) at risk in danger of becoming extinct or disappearing from a region (94)
bond connection between atoms or ions (213) boreal forest biome that has trees, such as spruce and fir, that have cones and needles (17)
atmosphere layer of gases that surrounds Earth (19) Glossary
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Glossary C carnivores organisms that eat mostly meat, for example, wolves (30)
combustibility ability of a substance to react quickly with oxygen to produce heat and light (153) comet celestial object made of ice and dust (318)
carrying capacity maximum number of individuals that an ecosystem can support without reducing its ability to support future generations of the same species (40)
commensalism [kuh-MEN-suhl-iz-uhm] type of symbiosis in which one species benefits from the relationship without harming or helping the other species (40)
celestial object object we can see in the sky, including the Sun, the Moon, Earth, other planets, and comets (258)
community populations of different species that live and interact in the same area (14)
cellular respiration process organisms use to obtain energy from glucose and other carbohydrates (29)
competition interaction between two or more organisms competing for the same resource in a given habitat (38)
charging by contact charging process in which electrons transfer from the charged object to the neutral object that it touches (407)
components parts of a system (11)
chemical change change in matter that results in the formation of a new substance or substances (152)
condensation change of state from a gas to a liquid (138)
chemical family group of elements with certain shared physical and chemical properties; represented by one of the 18 vertical columns in the periodic table of the elements (193) chemical formula combination of symbols that identifies which elements, and how much of each, are in a compound (219) chemical property ability of a substance to change into a new substance or substances; e.g., how a substance interacts with other substances, such as acids, or how it reacts to heat or light (152)
compound pure substance made from two or more elements that are combined together chemically (141)
conduction movement or transmission of electric charges through a substance (400) conductivity ability of materials to allow electrons to move freely in them (400) conductor material that allows electrons to change positions (400) conservation biology modern science that seeks to understand and protect biodiversity (94) constellation group of stars that, from Earth, resembles a recognizable form (294)
chemical reaction process in which a chemical change occurs; produces a new substance or substances (152)
consumer organism that eats other organisms to obtain energy because it cannot produce its own food (30)
chlorophyll substance in plants that absorbs sunlight and causes leaves to be green (28)
corona [kuh-ROH-nuh] outermost layer of the Sun, extending beyond the chromosphere for millions of kilometres (309)
chromosphere [KROH-muhs-feer] thin layer of the Sun, lying above the photosphere, and with a red cast to it (309)
coronal mass ejection extremely powerful kind of solar flare that causes a large amount of plasma to be thrown out through the corona and into space (311)
circuit path for electrons to flow; includes energy source, electrical load, and conducting wires (434) circuit breaker safety device in which a wire heats up and bends when there is excess current in the circuit; this triggers a spring mechanism that turns off the flow of electricity (463) circuit diagram drawing made with symbols that shows the components and connections in a circuit (450) clay soil soil that contains small rock particles that pack tightly together (73) clearcutting removing all trees, regardless of size, in an area at one time (62) climate average weather conditions that occur in a region over a span of 30 years or more (60) climate change change of climate characteristics in a region, such as a rise or fall in average temperatures or an increase or decrease in rainfall (60) cohesion property of sticking together; a physical property of water (150) 560
Glossary
coulomb (C) [KOO-lawm] metric unit of electric charge; one coulomb equals 6.24 × 1018 electrons added to or removed from a neutral object (399) crop rotation practice of planting a different type of crop in a particular field each year (75) current electricity continuous flow of electrons in a circuit (434)
D dark matter matter in the universe that is invisible because it does not interact with light or any other kind of radiation; at least 90 percent of the universe may be composed of dark matter (271) deciduous forest biome that has trees, such as maples and oaks, that lose their leaves in the winter (17) decomposer consumer that breaks down organic matter and releases the nutrients back into the ecosystem; for example, fungi and bacteria (30)
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Glossary denitrifying bacteria [dee-NIH-tri-fih-ing] bacteria that convert nitrates into nitrogen gas (26)
electrostatics [e-LEK-truh-STA-tiks] study of static electric charges (404)
deposition change of state from a gas directly into a solid (138)
element pure substance that cannot be broken down into a simpler substance (24, 141)
detritivore [de-TRI-ti-vor] consumer that feeds on organic matter; for example, earthworms (30)
endangered species facing extinction or extirpation (94)
direct current (DC) electric current flowing in one direction (439) dissolved oxygen the level of oxygen present in water (77) dry cell electrochemical cell that uses a paste instead of a liquid electrolyte (435)
E ecological footprint estimate of how much land and water is needed to support a person’s lifestyle (106) ecology [ee-KAWL-uh-jee] study of how organisms interact with each other as well as with their environment in a system (12) ecosystem [EE-koh-sis-tuhm] complex, self-regulating system in which living things interact with each other and with nonliving things (13) efficiency ratio of the useful energy that comes out of a device to the total energy that went in (493) electric charges charged particles that exert an electric force on each other (394) electric current measure of the amount of electric charge that passes by a point in an electrical circuit each second (439) electrical discharge rapid transfer of electric charges (409) electrochemical cell package of chemicals that converts chemical energy into electrical energy that is stored in charged particles (435) electrode metal strip that reacts with the electrolyte in an electrochemical cell (435) electrolyte [e-LEK-truh-liht] liquid or paste that conducts electricity because it contains chemicals that lose or gain electrons to form ions (435) electromagnetic radiation energy that travels in waves of varying lengths; visible light is one form of electromagnetic radiation (281) electromagnetic spectrum full range of electromagnetic radiation, organized by wavelength from very long to very short; examples include radio waves, microwaves, infrared, visible light, ultraviolet radiation, and X-rays (281) electron negatively charged particle in an atom; located outside the nucleus of the atom (172, 396) electron affinity [e-LEK-trawn a-FIN-i-tee] tendency of a substance to hold on to the electrons (398) electroscope instrument that can detect static charge (404)
EnerGuide label that states how much energy an appliance will use in a month or year of average use (494) energy grid web of interconnections between generating stations, substations, and users; also called a distribution grid (476) energy pyramid diagram that shows the amount of available energy producers and consumers contain as energy flows through an ecosystem (32) Energy Star symbol identifying the most efficient appliances in each class (494) environment all the living and non-living things that exist on Earth (8) environmental steward someone who manages resources wisely, ensuring that they are used in sustainable ways for current and future generations (107) equilibrium in a population, a state where the number of births equals the number of deaths, so that the number of individuals stays the same over time (40) equinox [E-kwi-nawks] day when the hours of daylight and the hours of night are of equal length (341) eutrophication [yoo-tri-fi-KAE-shuhn] addition of nutrients to an aquatic ecosystem causing increased growth of plants such as algae (78) evaporation change of state from a liquid to a gas; also known as vaporization (138) ex-situ conservation [eks-SI-too] protection of species by removing them from their natural habitat (96) extinction the death of every member of a species (54) extirpated species that no longer exists in a particular region but still occurs elsewhere (94)
F food chain diagram that shows the feeding relationships among organisms (31) food web diagram that shows complex feeding relationships among organisms that eat many different things; interconnected food chains (31) fossil fuel fuel formed from the organic matter of organisms that lived millions of years ago; includes coal, oil, and natural gas (478) freezing change of state from a liquid to a solid (138) freezing point temperature at which a liquid turns to a solid; same temperature as the melting point (139) Glossary
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Glossary freshwater biome water-based biome in which the water has a very low salt content (17)
hydroelectricity electricity generated by harnessing the power of falling water (477)
friction force resisting the relative motion of two surfaces in contact (397)
hydrosphere all the water on Earth (19)
fuel cell electrochemical cell that generates electricity directly from a chemical reaction with a fuel, such as hydrogen (436)
I
fuse safety device in an electric circuit that has a metal conductor with a low melting point; if the current gets too high, the metal in the fuse melts and the current flow stops (463)
induction movement of electrons within a substance, caused by a nearby charged object, without direct contact between the substance and the object (407) inert does not react easily with other chemicals (133) in-situ conservation [in-SI-too] protection of species in their natural surroundings (96)
G galaxy collection of hundreds of billions of stars held together by gravity (254)
insulator solid, liquid, or gas that resists or blocks the movement of electrons (400)
generator device that transforms the energy of motion into an electric current (476)
integrated pest management method of pest control that uses knowledge about a pest’s biology and habitats to keep the pest population under control rather than eradicating it (107)
genetic diversity differences among individuals of the same species (54)
invasive species non-native species that causes harm to the ecosystem into which it has been introduced (59)
geostationary [JEE-oh-STAE-shun-e-ree] orbit in which a satellite orbits Earth at the same rate as Earth rotates (356)
ion atom or group of atoms that has lost or gained electrons (192)
geothermal energy energy from water naturally heated by hot rock in the Earth’s crust (479)
ion charge electric charge that an atom or group of joined atoms takes on when it loses or gains electrons (192)
global warming increase in Earth’s average temperature (60)
ionic bond attraction between ions; e.g., bond in an ionic compound (213)
grassland biome that has few trees but is covered in various kinds of grasses and shrubs (17) ground fault circuit interrupter (GFCI) residual current device that detects a change in current and opens the circuit, stopping current flow (464) grounding process of connecting a charged object to Earth’s surface (408) group classification of elements with certain shared physical and chemical properties; represented by one of the 18 vertical columns in the periodic table of the elements; also known as a chemical family (193)
ionic compound pure substance consisting of at least one metal and one non-metal (212)
K kilowatt-hour (kW•h) commonly used unit of electrical energy, equal to a consumption of one kilowatt in one hour (492)
L law of attraction law stating that particles with opposite charges attract each other (399)
H habitat area where an organism lives (14) habitat change process in which habitats are altered enough by humans so that native species can no longer live there (55) habitat fragmentation alteration of small areas within a large region, creating a patchwork of altered and original habitats (56) heavy metal group of substances that have a density of 5 g/mL or higher; for example, mercury, lead, and cadmium (79)
law of repulsion law stating that particles with like charges repel each other (399) lightning rod metal pole with a wire attached to it that runs down to the ground with the purpose of allowing the electrons that build up on a building to spread out into the air (418) light-year (ly) distance measure; 1 ly equals the distance that a beam of light can travel through space in 1 year; it is equivalent to 63 000 AU or 9 000 billion km (261)
herbivore animal that eats only plants; for example, moose and deer (30)
limiting factor environmental factor that prevents an increase in the number of organisms in a population or prevents them from moving into new habitats (41)
holistic approach [hoh-LIS-tic] emphasizes an entire system (11)
lithosphere [LITH-oh-sfeer] Earth’s solid, outer layer (19)
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Glossary load device that converts electrical energy to another form of energy (434)
non-metal elements that are grouped together mainly because they do not resemble metals; e.g., carbon (180)
loam soil that has rock particles of many different sizes (73)
non-point source pollution pollution that enters bodies of water indirectly when rain or snow travels over land and picks up pollutants from many different sources before entering a stream or a lake; for example, fertilizer and pesticide run-off from farms (58)
lunar eclipse occurs when Earth blocks the Sun’s light shining on the Moon, making the Moon briefly disappear (328)
M marine biome water-based biome in which the water has a high salt content (17)
non-renewable resource resource that cannot be replaced once it is used up, such as coal or oil (474)
matter anything that has mass and volume (138)
nuclear fusion process in which the nuclei of atoms fuse together and form larger atoms; during this process, an enormous amount of energy is released (261)
mechanical mixture combination of pure substances in which the different substances are individually visible (142)
nucleus (atomic) centre of the atom, which contains the protons and neutrons (173, 396)
melting change of state from a solid to a liquid (138)
nutrient cycle the process of moving a nutrient from the abiotic part of an ecosystem to the biotic part and back again (24)
mass measure of the quantity of matter in an object (138)
melting point temperature at which a solid turns into a liquid; same temperature as the freezing point (139) metal element that is malleable and ductile and conducts electricity and heat; most elements are metals (180) metalloid element with metallic and non-metallic properties; e.g., silicon (181) meteor a meteoroid (a small piece of rock or metal) that enters Earth’s atmosphere and begins to burn up as a result of friction (318) microgravity condition in which the gravitational forces that act on a mass are greatly reduced (367) mimicry [MIM-uh-kree] copying the appearance of another species to avoid predators; for example, the viceroy butterfly looks very much like the foul-tasting monarch butterfly (39) molecular compound pure substance that is formed when non-metals combine chemically (214) molecule group of atoms that share electrons; molecular compounds contain molecules (214) mutualism type of symbiosis in which both species benefit from the symbiotic partnership (40)
nutrients substances that an organism uses to build and repair the cells of its body (22)
O ohm (⍀) SI unit for measuring resistance (441) Ohm’s law law stating that as long as temperature stays the same, V = IR, where V is potential difference, I is current, and R is resistance (460) ohmmeter device for measuring electrical resistance; usually part of a multifunctional meter called a multimeter (441) omnivore animal that eats both animals and plants; for example, bears and raccoons (30) orbital radius planet’s distance from the Sun (343) organic farming farming without the use of chemical fertilizers or pesticides (108) organic matter remains of dead organisms and animal wastes (30) overexploitation using a resource faster than it can be replaced (56)
N native species species that normally live in a habitat (55)
P
nebula [NEB-yoo-luh] large cloud of dust and gas (264)
parallel circuit electric circuit in which the parts are arranged so that electrons can flow along more than one path (451)
neutron particle that has no electric charge so is neutral; located in the nucleus of the atom (173, 396) niche [NEESH] all the interactions of a given species with its ecosystem (14) nitrifying bacteria bacteria that convert ammonia into nitrites and then nitrates (26) nitrogen fixation conversion of nitrogen gas into ammonia (25) nitrogen-fixing bacteria bacteria that convert nitrogen gas into ammonia (25)
parasitism type of symbiosis in which one species benefits from the relationship at the expense of the other species (40) particle theory of matter theory stating that all matter is composed of very tiny objects called particles; that all particles have spaces between them; that particles of matter are always in motion; that particles in a substance attract each other (139) parts per million (ppm) measurement of chemicals that occur in low concentrations; e.g., a sample having a mercury concentration of 1 ppm has 1 part mercury per million parts sample (232) Glossary
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Glossary period one of seven horizontal rows in the periodic table of the elements (193)
resistance degree to which a substance opposes the flow of electric current through it (441)
pesticides chemicals that kill unwanted organisms, usually ones that attack crops and reduce their yields (80)
resistor any material that can slow current flow in a circuit, such as the filament in a light bulb (441)
photosphere layer of the Sun usually considered to be the boundary between the inside and the outside of the Sun (309)
retrograde motion apparent reversal of a planet’s path relative to the starry backdrop (342)
photosynthesis [foh-toh-SIN-thuh-sis] process plants use to produce carbohydrates from carbon dioxide, water, and sunlight (28)
revolution one complete orbit of Earth around the Sun, a journey of one year (325)
physical property characteristic of a substance that can be observed or measured (150) planet celestial object that orbits one or more stars and is capable of forming into a spherical shape as it melds under the weight of its own gravity (313) point source pollution pollution that enters a body of water at a specific place from an identifiable source; for example, oil spills from tankers and wastewater from pulp and paper mills (58) pollution any substance added to the environment that produces a condition that is harmful to organisms (58) population group of members of the same species that live in the same area (14) potential difference or voltage (V ) difference in electric potential energy between two points that will cause current to flow in a closed circuit (437) potential energy energy stored in an object; each electric charge has electrical potential energy (437) predation [pred-AE-shuhn] one organism eating another organism to obtain food (39) predator animal that catches and feeds on other live animals (30) prey animals that predators hunt and catch (30) primary consumer organism that eats producers; for example, a caterpillar, which eats plants (30) producer organism that carries out photosynthesis (30) prominence large, often curved, bright stream of particles extending outward from the photosphere into the corona (313) property characteristic that describes a substance (141) proton positively charged particle in an atom, found in the nucleus (173, 396)
rotation one complete spin of Earth on its axis, which takes almost 24 hours (324) run-off water that runs off the ground into nearby streams or rivers (25)
S sandy soil soil that contains relatively large rock particles (73) scavenger carnivore that eats the remains of dead animals; for example, vultures (30) secondary consumer organism that feeds on primary consumers; for example, a robin, which eats caterpillars (30) series circuit electric circuit in which the components are arranged one after another in series (451) short circuit accidental low-resistance connection between two points in a circuit, often causing excess current flow (462) soil loose covering on the ground containing organic matter, minerals, and moisture (72) soil conservation use of farming methods that protect soil from erosion and loss of nutrients (108) soil erosion loss of soil when water or wind wash or blow it away (74) solar eclipse occurs when the Moon blocks the Sun’s light to viewers on Earth; this happens when the Moon lies directly between Earth and the Sun (327) solar flare massive explosion on the surface of the Sun (311) solar system the Sun together with all the planets and other celestial objects that are held by the Sun’s gravitational attraction and orbit around it (260)
protostar star in its first stage of formation (296)
solar wind thin but steady stream of subatomic particles flowing out of the Sun’s surface in all directions (312)
pure substance one kind of matter with a unique set of properties, such as colour, hardness, boiling point, and melting point; an element or compound (141)
solution combination of pure substances in which the different substances are not individually visible; a homogeneous mixture (142)
R
special concern has characteristics that make a species sensitive to human activities or natural events (94)
relative mass mass of an object in comparison to the mass of another object (175) renewable resources resource that can be reused or replaced, such as sunlight and wind (474) reservoir any place where matter accumulates (24) 564
Glossary
species [SPEE-sees] group of similar organisms that can reproduce with each other and their offspring can also reproduce (14) spectral lines series of dark lines that appears across a star’s light spectrum and indicates the chemical elements in the star’s composition (282)
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Glossary spectral shifting change in position of spectral lines to the left or the right of where they normally lie in the spectrum of a light source that is not moving (282) spectroscope optical instrument that, like a prism, separates light into its spectral colours (281)
terrestrial land-based (17) tertiary consumer [TUHR-shuh-ree] third level of consumer, which eats secondary consumers; for example, a hawk that feeds on small birds (30)
spectrum rainbow band of colours into which white light separates when it passes through a prism (278)
thermoelectric generating plant electricity-generating plant that uses a fuel such as coal or biomass to heat water to create high-pressure steam (478)
spinoff secondary beneficial effect or product of a thing or an activity (354)
thermonuclear term describing electrical energy produced by heat in nuclear power stations (479)
star hot ball of plasma, an electrically charged gas, that shines because nuclear fusion is taking place at its core (261)
threatened species at risk of becoming endangered if limiting factors are not reversed (94)
static charge or static electricity electric charge that builds up on the surface of an object (396)
topsoil uppermost layer in soil, composed chiefly of decaying organic matter, rock particles, and organisms (72)
stewardship way of acting that involves taking personal responsibility for the management and care of something (8)
transistor tiny device that acts as a switch or amplifier in a circuit (449)
subatomic particles particles that make up an atom, including protons, neutrons, and electrons (175)
tundra biome that has no trees but only small shrubs, hardy grasses, mosses, and lichens (17)
sublimation change of state from a solid directly into a gas (138)
turbine machine that uses the flow of a fluid to turn a shaft; used in generators to generate electricity (476)
subsoil layer below the topsoil (72) summer solstice day of the year with the longest period of daylight, representing the start of summer (340) sunspot region on the Sun’s surface that is cooler than the surrounding areas (310) supernova [SOO-puhr-NOH-vuh] star’s explosion, caused by the gradual build-up of heavy elements in the star’s centre, resulting in the core’s collapse (263) suspension cloudy mixture in which tiny particles of one substance are held within another; a type of heterogeneous mixture (142)
U universe everything that physically exists: the entirety of space and time, and all forms of matter and energy (255) urban sprawl unplanned, disorganized growth of urban and suburban development into the surrounding countryside (62)
V valence electron [VAE-luhns] electron in the valence shell of an atom (197)
sustainability the ability of populations of organisms to continue to live, to interact, and to reproduce indefinitely in an environment (9)
valence shell outermost shell or energy level of an atom that has electrons in it (197)
sustainable use using an ecosystem’s resources in a way that meets our current needs without compromising the ability of future generations to meet their needs (54)
voltage or potential difference difference in electrical potential energy between two points that will cause current to flow in a closed circuit (437)
switch device that turns a circuit on or off by closing or opening the circuit (434)
voltmeter device used to measure the potential difference between two locations in a circuit (438)
symbiosis [sim-bee-OH-sis] close interaction between two different species in which members of one species live in, on, or near members of another species (39)
volume measure of how big an object is or how much space a fluid takes up (138)
system group of individual parts that interact as a whole to accomplish a task (11)
W
T
wetland area in which the soil is saturated with water for at least part of the year (4)
temperate coniferous forest biome that has different types of needle- and cone-bearing trees than a boreal forest, such as Douglas fir, Sitka spruce, and western hemlock (17)
winter solstice [SAWL-stis] day of the year with the shortest period of daylight, representing the start of winter (340)
volt (V) SI unit for measuring potential differences (438)
wet cell electrochemical cell that has a liquid electrolyte (435)
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Index A Abiotic factors, 13, 15 Aboriginal people and astronomical phenomena, 264, 340, 341 and ecosystem interactions, 38 and environmental stewardship, 9 holistic approach of, 11–12 and medicine wheels, 341 and mercury in fish, 232 Acetate, 235 Acid rain, 70, 70–71, 488 Acidity, 74 of soils, 74 of water, 78 Adhesion, 150 Agriculture First Nations, 341 sustainable, 107–109 Air as conductor, 410 as insulator, 410 as mixture of chemicals, 210 pollution, 58, 184 Algae, 15, 29, 78, 79, 92 Algonquin Park, 99 Alkali metals, 194 Alkalinity, 74 Alloys, 178–179 Alpher, Ralph, 280 Alternating current (AC), 439 Aluminum, 136, 138 Ammeters, 439, 440, 454 Amperes, 439 Animals and cellular respiration, 29 and energy from food, 32 and nitrogen, 26 overgrazing by, 75 Aquaculture, 64–65 Aquatic biomes, 17 Aquifers, 25 Aral Sea, 57–58 Aristotle, 342 Artificial satellites, 356 Asterisms, 294 Asteroid belt, 262, 315, 318 Astrolabes, 345 566
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Astronauts, 8, 352 Astronomers, 258, 340 Astronomical phenomena, 294 Astronomical units (AU), 261 Astronomy, 258, 340–341 tools of, 345–348 At-risk species, 94, 94–95 Atmosphere, 19 Atomic mass, 192 Atomic mass units (amu), 192 Atomic number, 190, 190–191, 192 Atomic theory, 170, 170–176 196-199 Atom(s), 168 models of, 170–175 in molecule, 214 neutrality of, 396 particles of, 396 smallness of, 239 Aurora australis, 312 Aurora borealis, 312, 312–313
B Bacteria, 15, 30, 244. See also Nitrogen-fixing bacteria Batteries, 231, 435, 436, 437–438 Becquerel, Edmond, 480 Bedrock, 72 Bees, 10–11, 117 Benfey, Theodor, 199 Benzene, 235 Big Bang theory, 280, 284–285, 348 Binary systems, 263 Bioaccumulation, 79 Biodiversity, 9, 54–60, 96–97 conservation of, 94–97 “hot spots,” 98 increasing, 81 logging and, 62 stress and, 61 Biological oxygen demand (BOD), 77 Biomagnification, 79 Biomass, 478 Biomes, 15–17, 16, 18–19 Biosphere, 18, 18–19
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Biotic factors, 13, 15 Black holes, 270, 270–271, 289, 299 Blackouts, electrical, 390–391 Bohr, Niels, 174 Bohr diagrams, 174, 197, 198, 200, 214 Boiling, defined, 138 Boiling point, 139 Bonds, 213 Boreal forests, 16, 17, 62–63 Brahe, Tycho, 344 Brain pacemakers, 427 Breathing, 29 Butterflies Karner blue, 94 monarch, 39, 47, 59
C Calcium, 169 Calcium carbonate, 218, 223 Calcium chloride, 219, 228 Calcium sulphate, 218 Campfires. See Fires Carbohydrates, 28, 29 Carbon, 24, 184 compounds, 149 cycle, 26–27 and fires, 148, 149 reservoirs, 26–27 resistors, 442 trees and, 110 Carbon dioxide carbon and, 26 and climate change, 60 and fires, 149 and glucose, 28 nutrient cycle and, 24 plants and, 24, 26, 28–29 and pollution, 58 preparation of, 144–145 and soda pop, 149 and water, 27 Carnivores, 30 Carp, 4–5 Carrying capacity, 40, 40–41, 42 Cathode ray tubes, 172 Celestial objects, 258 Cellular respiration, 29
Centauri system, 263 Chadwick, James, 173 Charging by contact, 407, 413 Charon, 318 Chemical changes, 152, 153, 158–159 Chemical families, 193 Chemical formulas, 219 for ionic compounds, 223, 224–225 for molecular compounds, 227 Chemical properties, 152 Chemical reactions, 152 Chemicals, 210–211, 230–231 Chemistry art of, 163 backgrounder, 548–550 Chlorine, 183, 185, 196–197, 232–233 Chlorofluorocarbons (CFCs), 234 Chlorophyll, 28 Chromosphere, 309 Circuit breakers, 463 Circuit diagrams, 450 Circuits, 434 designing, 448 integrated, 449 resistance in, 441 tiny, 449 transfer of energy in, 438 Clay soil, 73 Clearcutting, 62 Climate, 60 Climate change, 60 Coal, 27, 184, 478, 488 Cohesion, 150 Combustibility, 153 Comets, 318 Commensalism, 40, 47 Communicating in science, 528–531 Communications satellites, 356 Communities, 14, 14–15 Competition, 38, 38–39 Components, 10–11, 11
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Index Compounds, 141, 170, 210–211 carbon, 149 naming, 219 Condensation, 138, 139 Conduction, 400 Conductivity, 400, 446 Conductors, 400, 400–401, 441, 462 metalloids as, 181 metals as, 180 sodium chloride as, 213 water as, 401, 432–433 Conservation biology, 94, 94–97 Constellations, 294, 294–295 Consumers, 30, 31, 32 Contact, charging by. See Charging by contact Convective zone, of Sun, 309 Convention on Biological Diversity, 95 Conventional current, 440 Cootes Paradise, 4–5 Copernicus, Nicholas, 343, 344 Copper, 168, 227 Coral reefs, 12 Corn, 155 Cornwall (Ontario), 99 Corona, 309 Coronal mass ejections, 311 Coulomb, Charles-Augustin de, 399 Coulombs, 399 Cowbirds, 117 Crocodiles, 22, 23 Crop rotation, 75, 108 Current electricity, 434, 439–440, 445. See also Electric current Cycles, 24, 33
D Dalton, John, 171 Dark matter, 271 DDT. See Dichloro-diphenyltrichloroethane (DDT) Deciduous forests, 16, 17 Decision making for environmental and social issues, 520–521
Decomposers, 30, 75, 106 Deforestation, 84 Denitrifying bacteria, 26 Deposition, 138 Detritivores, 30 Diamonds, 184, 205 Dichloro-diphenyltrichloroethane (DDT), 80, 236 Direct current (DC), 439 Dissolved oxygen, 77 Diversity. See also Biodiversity genetic, 54 Don River Valley, 104 Donelan, Max, 468 Dry cells, 435, 435–436
E Earth, 316 age of, 315 and asteroid belt, 315 axis of, 324, 325 coronal mass ejections and, 311 distance from Moon to, 259 distance to Milky Way, 260 habitable environment on, 306 magnetic field, 310 motion of, 322–323 as rocky inner planet, 314 rotation of, 324, 328 tornadoes on, 306 view of sky from, 323 view of stars from, 294–295 views of, from space, 353 “Earthrise,” 352 Easter Island, 52–53 Eclipses, 327–328 Eco-villages, 122–123 Ecological consultants, 87 Ecological footprints, 106, 106–107, 115 Ecology, 12 Ecosystems, 13 acid rain and, 70–71 assessment of impacts on, 71–85 birth of, 36–37
combinations of, 15–17 communities within, 14–15 elements of, 13–15 energy flows through, 28–29 freshwater, 57, 61 humans and, 54–60 interactions, 38–40 law and, 97 natural vs. artificial, 20 Ontario, 60–63 restoration of, 99–100 size of, 15 stress on, 61 sustainable use of, 54 Efficiency, 493, 493–494 Electric charges, 394, 395. See also Static charges Electric current, 439, 439–440, 454, 455, 456, 459–462. See also Current electricity Electric shocks, 394, 463, 464 Electrical discharges, 409, 409–411 Electricity. See also Energy backgrounder, 552–554 coal and, 184 consumption, 491 cost of, 490–491 environmentally friendly, 112 and fish, 432–433 generation of, 474–489 household consumption, 491, 492, 495 meters, 490–491 sources of, 474–475 use of, 490–491, 495 Electrochemical cells, 213, 435 Electrodes, 435 Electrolytes, 435 Electromagnetic induction, 476 Electromagnetic radiation, 281, 281 Electromagnetic spectrum, 281, 308 Electron affinity, 398
Electrons, 172, 173, 175, 396 of chlorine atom, 197 flow of, 434, 440, 441 friction and, 397 ion charge and, 192–193 patterns in arrangement of, 198 potential energy, 437 and quantum mechanical model, 174 and shells, 174 transfer of, 397, 438 in wire, 438 Electroscopes, 404, 405, 406 Electrostatic generators, 411 Electrostatic precipitators, 423, 425 Electrostatics, 404, 404–415. See also Static charges control products, 423 environmental applications, 423 and flammable materials, 419 in home, 420 and lightning, 416–418 and photocopying, 422 and spray painting, 421 and vehicles, 419 Elements, 24, 141, 178–187, 396 atoms and, 168, 170, 171 common, 183–185 Dalton’s table of, 171 and electrons, 172 multivalent, 222 patterns among, 188–189 symbols of, 181–182 toxic, 200 Elliot Lake Secondary School, 474, 475 Elliptical orbits, 344 Emissions, 70, 71, 106 Endangered Species Act, 97 EnerGuide, 494 Energy. See also Electricity from food, 22–23, 32 geothermal, 479 nuclear, 479 pyramids, 32, 34 self-sufficiency, 496
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Index solar, 480 tidal, 481 wind, 481, 484 Energy grid, 390–391, 476 Energy Star, 494 Environment, 8, 8–9 decision making and, 520–521 efficiency of devices and, 494 electrostatics and, 423 elements and compounds in, 232–236 holistic approach to, 11–12 renewable vs. non-renewable energy sources and, 484 sustainability and, 495 systems in, 10–13 toxic substances in, 231 Environmental Farm Plan (EFP), 107 Environmental stewards, 107 Environmental stewardship, 8–9, 105, 106, 107–114 Enzymes, 30 Equator, 322, 325 Equilibrium, 40 Equinoxes, 341 Erie, Lake, 92–93 Estimating, in measurement, 539 Eutrophication, 78, 112 Ex-situ conservation, 95–96, 96 Extinction(s), 54, 56, 94, 101
invasive, 66 mercury and, 79, 232, 233 shellfish, 66, 70 Fishing, 56. See also Overfishing of wild vs. farmed fish, 64–65 Flashlights, 448 Flowers, 10–11 Fluoride, 237, 244 Foam, 146 Food chains, 31–32 energy from, 22–23, 32 freeze-dried, 154 locally produced, 109, 114 webs, 31, 31–32 Forestry, 63, 110–111 Forests, 15–16, 17, 62–63. See also Deforestation carbon and, 26 rain, 55, 155 urban, 110–111 Formulas. See Chemical formulas Fossil fuels, 60, 478, 485 Freezing, 138, 150 Freezing point, 139 Freshwater biomes, 17 Freshwater ecosystems, 57, 61 Friction, 397, 407, 411 Fuel cells, 436 Fundy, Bay of, 329, 481 Fungi, 30 Fuses, 463
F
G
Faraday, Michael, 476 Fertilizers, 58, 78, 82–83, 92, 93, 107, 108 Feynman, Richard, 239 Fires, 148–149, 154 Fireworks, 136–137 First Nations. See Aboriginal people Fish coral reefs and, 12 electric, 432–433 heavy metals in, 201 ice and, 150
Galaxies, 254, 254–255, 265, 268–277 and black holes, 270–271 clusters, 274 Hubble and, 278–279, 280 mapping distances to, 276 properties of, 270–272, 278–279, 280, 282 shapes of, 272–273 Galileo Galilei, 344 Gamow, George, 280 Garbage. See Waste
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Gases, 138–139, 140 identifying, 144–145 Generators, 390–391, 476, 477. See also Electrostatic generators Genetic diversity, 54, 97 Geocentric model of planetary motion, 342–343 Geostationary orbits, 356 Geothermal energy, 479 Global Positioning System (GPS) technology, 357, 362 Global warming, 60 Glucose, 28, 29 Gold, 141, 178–179 Graphic organizers, 532–533 Graphite, 184 Graphs, 43, 349, 540–543 Grasslands, 16, 17 Gravity, 270. See also Microgravity and comets, 318 on Mars, 367 Moon and, 325 and real-time imaging, 359 and stars, 296, 298 and tides, 328 and weight, 367 Great Lakes Water Quality Agreement, 93 Griffith Smith, Neil, 117 Ground fault circuit interruptors (GFCI), 464 Grounding, 408, 419 Groups, 193, 193–195 Gyres, 68–69
H Habitat change, 55, 55–56 Habitat fragmentation, 56, 62–63 Habitats, 14. See also Ex-situ conservation; In-situ conservation loss of, 60 protection of, 97 restoration of, 100 Halogens, 194 Hamilton (Ontario), 4–5, 62
Heat and chemical change, 153 for electricity generation, 478–479 metals and, 180 particles and, 140 Heavy metals, 79, 201, 231 Heliocentric model of planetary motion, 343–344 Helium, 190, 193, 195, 198, 298, 309 Herbivores, 30 Hertzsprung, Ejnar, 300 Hertzsprung-Russell diagram, 300–301 Heterogeneous mixtures, 142, 143 Holistic approaches, 11, 11–12 Holland Marsh, Ontario, 73 Homogeneous mixtures, 142, 143 Hubbard Brook Experimental Forest, 84 Hubble, Edwin, 278–279, 280, 282, 283 Hubble Space Telescope, 254, 347, 375 Hund, Friedrich, 197 Hydrates, 224 Hydroelectricity, 477, 484, 486–487 Hydrogen, 24 atomic mass of, 192 atomic number of, 190 as element, 184 naming of molecular compounds containing, 226 preparation of, 145 spectral lines of, 282 and stars, 298 valence electrons of, 198 and water, 183 Hydrogen peroxide, 210–211, 214 Hydrosphere, 19
I Ice, 140, 150 Imaging, satellite, 358–360
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Index In-situ conservation, 96, 96–97 Induction, 407, 407–408, 414 Inert, defined, 133 Inquiry process of science, 514–517 Insulators, 400, 400–401, 441 Integrated pest management, 107, 107–108 Interactions biotic, 38–40 ecosystem, 38–40 within systems, 10–11 International Space Station, 255, 354, 355, 366, 367, 368, 480 Invasive species, 59, 66, 100–101 Ion charges, 192, 192–193, 220 Ionic bonds, 213 Ionic compounds, 212, 212–213 formulas for, 223, 224–225 naming, 221–223 Ions, 192 Iron, 141, 168, 183
J James Webb Space Telescope, 347 Jupiter, 259, 262, 315, 317, 338, 342, 343
K Kepler, Johannes, 344 Kilowatt-hours, 492
L Lakes, 57–58, 61, 70, 92–93 Landfills, 58, 231 Law of attraction, 399 Law of repulsion, 399 Laws, scientific, 459 Leadership in Energy and Environmental Design (LEED), 111–112 Legumes, 26, 75 Lemaître, Georges, 278 Length, measuring, 536 Levi ben Gerson, 345
Light. See also Spectra from Sun, 308 travelling time of, 258–259 wave nature of, 281–284 Light bulbs, 438, 441, 449, 451, 452, 493, 497 Light-years (ly), 261 Lightning, 25, 394, 410, 416–417 Lightning rods, 418 Limiting factors, 41, 41–42 Line installers and repairers, 468 Liquids, 138–139, 140 Lithium, 198 Lithosphere, 19 Load, electrical, 434 Loam soil, 73 Lunar cycle, 326 Lunar eclipses, 328 Lynxes, 42, 44
M Magnetic fields of Earth, 310 of Sun, 310 Malaria, 80, 236 Marine biomes. See Aquatic biomes Mars, 261, 314, 316 gravity on, 367 retrograde motion of, 342, 343, 344 travel to, 380–381 visiting, 369–370 Mass, 138. See also Relative mass measuring, 537–538 Material Safety Data Sheet (MSDS), xxii, xxiii Math scaling, 275 Matter, 138 changes in, 137 changes in states of, 138–139 classifying, 141–143 forms of, 138, 170 particle theory of, 139–140 physical properties of, 150–151 Measurement, 534–539
Mechanical mixtures, 142 Melting, defined, 138 Melting point(s), 139, 150 of gold, 178 of halogens, 194 Mendeleev, Dmitri, 188–189, 196 Mercury, 261, 314, 316 Mercury, 79, 180, 200, 231, 232–233 Merkhet, 345 Metalloids, 181 Metals, 141, 180 alkali, 194 Meteors, 318 Meteroids, 318 Methane, 478 Microcircuits, 449 Microgravity, 367, 367–368 Microscopes, 186, 544–547 Microwaves, 284–285, 348 Milky Way, 254, 265 black holes in, 270 dark matter and, 271 distance from Earth, 260 and galaxy clusters, 274 solar system and, 268–269 visibility of, 375 Mimicry, 39 Mixtures, 142, 143, 170 Molecular compounds, 214 formulas for, 227 naming, 226 Molecular models, 215–216 Molecules, 214 Moon, 260, 314 “buggy,” 369 distance from Earth to, 259 gravity on, 367 living on, 369 phases of, 326, 330 rotation of, 325–326 size of, 325, 327 spacecraft and, 352 and tides, 328 water on, 369 Moons, 314, 315, 318 MOST (Microvariability and Oscillations of Stars) telescope, 347 Multimeters, 454
Multivalent elements, 222 Mutualism, 40, 47
N Names and naming chemical vs. common, 218–219 compounds, 219 ionic compounds, 221–223 molecular compounds, 226 multivalent ions, 222 polyatomic ions, 223 salts, 218–219 National Aeronautics and Space Administration (NASA), 338, 369, 370 Native species, 55 Nebulae, 264, 299, 308, 312 Neptune, 262, 269, 315, 317 Neutrality, 74 Neutron stars, 299 Neutrons, 173, 175, 396 Niagara Escarpment, 62 Niches, 14, 14–15 Nitrifying bacteria, 26 Nitrogen, 24 cycle, 25–26 gas, 25, 26 Nitrogen fixation, 25–26 Nitrogen-fixing bacteria, 25–26, 75 Noble gases, 195 Nollet, Jean, 404 Non-metals, 180, 214 Non-point source pollution, 58, 58–59 Non-renewable resources, 474, 474–475, 482–483, 484 Nuclear fission, 479 Nuclear fusion, 261 Nuclear power. See Thermonuclear power Nuclear reactions and stars, 296 in Sun, 308 Nucleus, 396 of atom, 173 of chlorine atom, 196–197 Nutrient cycles, 24, 24–27 Nutrients, 22, 22–23, 75, 108
Index
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Index O Oceans as carbon reservoirs, 27 currents, 68–69 water cycle and, 25 Ohm, Georg Simon, 458–459 Ohmmeters, 441 Ohms, 441 Ohm’s law, 458–467, 460 Omnivores, 30 Orbital radius, 343, 343–344, 350 Organic farming, 108 Organic matter, 30 Overexploitation, 56, 56–57 Overfishing, 56–57 Oxygen, 24 algae and, 29 in atmosphere, 19 and breathing, 29 as element, 184–185 and fires, 148, 149 gas, 29, 184 in photosynthesis, 29 preparation of, 144 trees and, 29 and water, 77, 78, 183 Ozone, 19, 184–185, 234, 329
P Pacific Ocean, 68–69 Paints, 112–113, 230 Parallel circuits, 451, 456 Parasitism, 40, 47 Parks, 98–99 Particle theory of matter, 139, 139–140 Particles and art, 168 of atom, 172, 173, 396 Parts per million (ppm), 232 Payette, Julie, 332 Penzias, Arno, 285 Periodic table, 188–199, 200, 202–203, 220 Periods, 193 Persistent organic pollutants (POPs), 236 Pesticides, 5, 58, 80, 93, 107–108, 236 570
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PH scale, 74 Photocopying, 422, 424 Photosphere, 309 Photosynthesis, 27, 28, 28–29 Physical changes, 149, 158–159 Physical properties, 150, 150–151 Planetary stewardship, 8 Planets, 266, 313, 313–318, 342–344. See also Names of individual planets Plants and carbon dioxide, 26, 28–29 and cellular respiration, 29 nitrogen and, 75 transpiration, 25 Plastics, 69, 132–133, 155, 230 Plato, 342 Plugs, three-prong, 464 Pluto, 318 Point source pollution, 58 Pollution, 58, 58–59 air, 58 farms and, 107 water, 76–80, 108 Polyatomic ions, 223, 225 Polyethylene, 133, 155 Polystyrene, 404 Populations, 14, 37 characteristics of, 40–41 limiting factors, 41–42 sustainability of, 42, 52–53 Potential difference, 437, 437–438, 442, 445, 451–452, 456, 459–462 Potential energy, 437 Precipitation, 24 Predation, 39, 44 Predators, 30 Prey, 30, 39, 41–42, 44 Primary consumers, 30 Problem solving for technological development, 518–519 Producers, 30, 31, 32 Prominences, 311
Properties, 141. See also Chemical properties; Physical properties atoms and, 170 changes in, 149 of common substances, 160 in identifying pure substances, 156–157 Protected areas, 98–99 Protons, 173, 175, 190, 396 Protostars, 296 Ptolemy, 342 Pure substances, 141, 143, 156–157
Q Quadrants, 345 Quantum mechanical model of atom, 174 Quasars, 348
R Rabbits, 40–41 Radiation, cosmic background, 284–285 Radiative zone, of Sun, 309 Reading, 526–527 Recycling, 58, 102, 106, 112–113, 230–231, 436 Relative mass, 175 Remote sensing, 358–359 Renewable resources, 474, 474–475, 482–483, 484 Research, 522–525 Reservoirs, 24 carbon, 26–27 Resistance, 441, 441–443, 445, 451, 455, 456, 459–462, 466 Resistors, 441, 441–442, 451 Resources. See also Nonrenewable resources; Renewable resources sustainability of, 53, 54 Respiration, 27 Retrograde motion, 342, 343–344 Revolution of Earth, 324 of Moon, 325–326
Robotics engineers, 333 Rotation of Earth, 324, 328 of Moon, 325–326 Run-offs, 25, 58, 93, 110 Russell, Henry Norris, 300 Rutherford, Ernest, 173, 174
S Safety electrical, 463–464 procedures, xxii–xxv symbols, 513 Salts, 218–219, 228 table, 183, 185. See also Sodium chloride Sandy soil, 73 Satellites, 356–360 Saturn, 262, 315, 317, 338, 342, 343 Scavengers, 30 Scientific notation, 265, 535 Seasons, 322 Secondary consumers, 30 Seed banks, 96 Semiconductors, 181 Series circuits, 451, 455 Sewage, 92, 93 Shells, in atoms, 174, 197 Short circuits, 462 SI units, 535–536 Significant digits, 534 Silicon, 181 Silver, 178–179, 180, 181, 186 Snowshoe hares, 42, 44 Social issues, decision making for, 520–521 Sodium, 180, 183, 185, 198 Sodium carbonate, 158, 159 Sodium chloride, 212–213, 215, 219, 228 Sodium hydroxide, 223, 225 Soil conservation, 108 Soil erosion, 74, 74–75, 108, 111 Soil(s), 72 acidity levels of, 74 assessing, 72–75 fertilizers and, 82 human impact on, 74–75
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Index as mechanical mixture, 142 profile of, 72 types of, 73 Solar and Heliospheric Observatory (SOHO), 306 Solar eclipses, 327 Solar energy, 480 Solar flares, 311 Solar storms, 329 Solar system, 260, 260–262, 268–269, 306–321 age of, 315 formation of, 313–315 models of, 320 sizing of, 307 Solar winds, 312, 313, 315 Solids, 138–139 Solstices, 340–341 Solutions, 142 Solvents, 155 Space Canadian contributions and, 361 debris in, 372 distances in, 254–255 expansion of, 284 exploration of, 255, 364 living in, 366–370 measuring distances in, 261 ownership of, 364, 365 time and, 258–259 travelling in, 366 weather, 329 Space exploration cost of, 364 and health, 368, 371 physical environment, 367 product technologies from, 355 transportation technologies from, 354 Space research, 354–360 cost of, 364 spinoffs, 364 Spacecraft, 338–339, 352, 354, 369 Sparks, 409, 410 Species, 14 diversity within, 54 endangered, 97–101
invasive, 59, 66, 100–101 native, 55 at risk, 94–95 Species Survival Plans (SSPs), 96 Spectra, 278, 279, 281–282 Spectral lines, 282, 282–284 Spectral shifting, 282 Spectroscope, 279, 281 Spinoffs, 354, 364 Spray painting, 421 Squirrels, 14 St. Lawrence River, 99 Stars, 261, 263–265 artificial light and, 375 birth of, 296 brightness of, 303 charts, 295, 302, 551 clusters, 272 distance to, 263 exploding, 263–264, 270, 301 Hertzsprung-Russell diagram of, 300–301 life cycle of, 296–301 mass, 297–299 red dwarfs, 297 red giants, 301 spectral patterns of, 304 supergiants, 301 view from Earth of, 294–295 white dwarfs, 297, 301 Static charges, 396, 412. See also Electric charges; Electrostatics Static electricity, 394–403, 396 current electricity and, 439 Stewardship, 8, 8–9 Subatomic particles, 175 Sublimation, 138 Subsoil, 72 Sucrose, 215 Sulphur, 180, 181 Summer solstice, 340 Sun, 261, 306. See also Headings beginning solar age of, 315 diameter of, 319
and Earth’s revolution, 325 and Earth’s rotation, 324 formation of, 308 layers of, 308–309 magnetic field, 310 radiation, 308 size of, 327 and space weather, 329 as star, 298, 308 surface features of, 310–311 tornadoes on, 306 and water cycle, 24 Sundials, 345 Sunspots, 310 Supergiants, 298 Supernovas, 263, 263–264, 270, 299 Surtsey Island, 36–37 Suspension, 142 Sustainability, 9, 485, 495 of agriculture, 107–109 businesses and, 112–113 of communities, 122–123 of construction, 111–112 and Easter Island, 52–53 ecological footprints and, 106 of forestry, 63, 110–111 individuals and, 113 in resource use, 53 stress and, 61 Sustainable use, of resources, 54 Suzuki, David, 86 Switches, 434, 438, 444 Symbiosis, 39, 39–40, 47, 75 Systems, 11 components of, 10–11 ecological, 12–13 in environment, 10–13 holistic approach to, 11–12 interactions within, 10–11
T Technological development, problem solving for, 518–519 Telescopes, 264, 284, 306, 354, 375 optical, 346–347, 348
radio, 348 reflecting, 346 refracting, 346 Temperate coniferous forests, 16, 17 Temperature measuring, 539 and resistance, 462 Terrestrial biomes, 17 Tertiary consumers, 30 Thermoelectric generating plants, 478 Thermonuclear power, 479 Thomson, J.J., 172 Three Gorges Dam, 486–487 Tidal energy, 481 Tides, 328–329 Time astronomical phenomena and, 349 and space, 258–259 Toothpaste, 244 Topsoil, 72, 74–75 Tornadoes, 306 Toronto Evergreen Brick Works, 104–105 Toxicity, 200, 230–231 Tracking devices, 357 Transistors, 449 Transmission lines, 390–391, 462, 468, 476 Transpiration, 25 Treaties, 95 Trees, 29, 100 Triboelectric series, 398 Tundra, 16, 17 Turbines, 476, 477
U Ultraviolet (UV) light, 308 United Nations Environment Programme (UNEP), 69 Universe, 255. See also Space expansion of, 286–287 mapping of, 259, 275 Uranus, 262, 315, 317 Urban sprawl, 62
V Valence electrons, 197, 198 Valence shell, 197
Index
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Index Venus, 261, 314, 316 Voltage, 437, 454, 455 Voltmeters, 438, 440, 454 Volts, 438 Volume, 138 measuring, 537
W Wabigoon River system, 232–233 Waste. See also Sewage mercury in, 231 in Pacific Ocean, 68 plastics, 68, 69 solid, 58 Water. See also Aquatic biomes
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acidity, 78 Bohr diagram of, 214 calcium in, 169 carbon dioxide and, 27 as chemical, 210 as compound, 210–211, 214 as conductor, 401, 432–433 copper(II) sulphate and, 159 cycle, 24–25, 84 elements of, 183 erosion, 37 fertilizers and, 78 fluoridation of, 237 ground, 25, 72
heavy metals and, 79 melting point of, 139 on Moon, 369 neutrality of, 74 organisms in, 76 over-use of, 57–58 oxygen in, 77, 78 physical properties of, 150 pollution, 108 power. See Hydroelectricity pure, 74 quality of, 76–80 table, 72 vapour, 24, 25, 70 Watts, 492 Weight, measuring, 537–538 Weightlessness, 367
Wet cells, 435 Wetlands, 4, 4–5, 25, 93, 100 WHMIS symbols, 513, xxiii Wildebeest, 22–23 Wilson, Lee, 162 Wilson, Robert, 285 Wind energy, 481, 484 Winter solstice, 340 Wintergreen candy, 499 Word equations, 28
Z Zoos, 95, 96
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Periodic Table of the Elements
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1 1
H
1
1+
Li
2
lithium 6.94 11
Na
3
sodium 22.99 19
K
4
5
C
solid
metalloid
Br
liquid
8
atomic number
1+
2 4
non-metal
Be
ion charge (if more than one, first one is the most common)
oxygen 16.00
name atomic mass
gas
2–
O
symbol
hydrogen 1.01 3
metal
2+
beryllium 9.01 1 + 12 2+
Mg
magnesium 24.31 + 1 20 2 + 21
3
Ca
Sc
4 3+
22
Ti
5 4+ 3+
23
V
6 5+ 4+
24
Cr
7 3+ 2+
25
Mn
8 2+ 4+
26
Fe
9 3+ 2+
27
Co
2+ 3+
potassium calcium scandium titanium vanadium chromium manganese iron cobalt 39.10 40.08 44.96 47.87 50.94 52.00 54.94 55.85 58.93 + + + + + + + + 1 38 2 39 3 40 4 41 5 42 6 43 7 44 3 45 3+ 37 + +
Rb
Sr
Y
rubidium strontium 85.47 87.62 + 1 2+ 55 56
6
Cs
Ba
cesium 132.91
barium 137.33 1+
87
Fr
7
francium (223)
88
yttrium 88.91
Hf
radium (226)
6
7
Rf
89–103
La
Tc
Mo
Ta
hafnium 178.49 104
2+
Ra
Nb 3
Ru 4
Rh
zirconium niobium molybdenum technetium ruthenium rhodium 91.22 92.91 95.94 (98) 101.07 102.91 + + + + + 4 5 6 7 4 4+ 72 73 74 75 76 77
57–71
57
576
Zr
rutherfordium (261)
3+
58
Ce
3+
W
tantalum 180.95 105
Db
dubnium (262)
59
Pr
3+
Re
tungsten 183.84 106
Sg
osmium 190.23 108
bohrium (264)
hassium (277)
Bh
seaborgium (266)
60
Nd
3+
61
Pm
Ir
Os
rhenium 186.21 107
iridium 192.22 109
Hs
3+
62
Sm
Mt
meitnerium (268)
3+ 2+
63
Eu
3+ 2+
lanthanum cerium praseodymium neodymium promethium samarium europium 138.91 140.12 140.91 144.24 (145) 150.36 151.96 + + + + + + 3 4 5 6 5 4 3+ 89 90 91 92 93 94 95 + + + +
Ac
Th
actinium (227)
thorium 232.04
Periodic Table of the Elements
Pa 4
protactinium 231.04
U
uranium 238.03
4
Np
neptunium (237)
Pu 6 Am 4
plutonium (244)
americium (243)
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18 2
13 5
14 6
B
10 28
Ni
11 2+ 3+
29
nickel 58.69 46
Pd
Cu
12 2+ 1+
30
copper 63.55 2+ 4+
47
Ag
Zn
48
Cd
N
carbon 12.01 3+
14
16 3–
8
O
nitrogen 14.01 15
Si
P
2–
9
oxygen 16.00 3–
16
S
helium 4.00
17
F
1–
10
fluorine 19.00 2–
17
Cl
Ne neon 20.18
1–
18
Ar
aluminum silicon phosphorus sulphur chlorine argon 26.98 28.09 30.97 32.07 35.45 39.95 + + – – – 2 31 3 32 3 34 2 35 1 36 4 + 33
Ga
zinc 65.41 1+
Al
7
C
boron 10.81 13
15
He
gallium 69.72 2+
49
In
Ge
As
Se
Kr
Br
germanium arsenic selenium bromine krypton 72.64 74.92 78.96 79.90 83.80 + + – – + 3 50 4 51 2 53 1 54 3 52 + 2+
Sn
Sb 5
I
Te
Xe
palladium silver cadmium indium tin antimony tellurium iodine xenon 106.42 107.87 112.41 114.82 118.71 121.76 127.60 126.90 131.29 4 + 79 3 + 80 2 + 81 1 + 82 2 + 83 3 + 84 1 – 86 2 + 85 78 + 2+ 1+ 1+ 3+ 4+ 5+
Pt
Au
platinum 195.08 110
Hg
gold 196.97 111
Ds
mercury 200.59 112
Rg
64
Gd
3+
65
Tb
thallium 204.38
Uub
darmstadtium roentgenium (271) (272)
3+
ununbium (285)
66
Dy
Pb
Tl
3+
lead 207.21 114
113
ununtrium (284)
Ho
3+
At
Rn
astatine (210)
radon (222)
Po 4
bismuth 208.98
Uuq
Uut
67
Bi
polonium (209)
115
Uup
116
Uuh
117
118
Uus Uuo
ununquadium ununpentium ununhexium ununseptium ununoctium (289) (288) (293) (?) (294)
68
Er
3+
69
Tm
3+
70
Yb
3+ 2+
71
Lu
2+
dysprosium holmium erbium thulium ytterbium lutetium gadolinium terbium 162.50 164.93 167.26 168.93 173.04 174.97 157.25 158.93 + + + + + + + 3 3 3 3 3 2 2 3+ 98 99 100 101 102 103 96 97 + + +
Cm
Bk 4
curium (247)
berkelium (247)
Cf
Es
Fm
Md 3
californium (251)
einsteinium (252)
fermium (257)
mendelevium (258)
No 3
nobelium (259)
Lr
lawrencium (262)
Periodic Table of the Elements
577