The Free High School Science Texts: Textbooks for High School Students Chemistry

The Free High School Science Texts: Textbooks for High School Students Chemistry
FHSST Authors
The Free High School Science Texts:
Textbooks for High School Students
Studying the Sciences
Chemistry
Grades 10 - 12
Version 0
November 9, 2008
ii
Copyright 2007 “Free High School Science Texts”
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FHSST Core Team
Mark Horner ; Samuel Halliday ; Sarah Blyth ; Rory Adams ; Spencer Wheaton
FHSST Editors
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Whitfield
FHSST Contributors
Rory Adams ; Prashant Arora ; Richard Baxter ; Dr. Sarah Blyth ; Sebastian Bodenstein ;
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Daniels ; Sean Dobbs ; Fernando Durrell ; Dr. Dan Dwyer ; Frans van Eeden ; Giovanni
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Andrew Kubik ; Dr. Marco van Leeuwen ; Dr. Anton Machacek ; Dr. Komal Maheshwari ;
Kosma von Maltitz ; Nicole Masureik ; John Mathew ; JoEllen McBride ; Nikolai Meures ;
Riana Meyer ; Jenny Miller ; Abdul Mirza ; Asogan Moodaly ; Jothi Moodley ; Nolene Naidu ;
Tyrone Negus ; Thomas O’Donnell ; Dr. Markus Oldenburg ; Dr. Jaynie Padayachee ;
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iii
iv
Contents
I
II
Introduction
1
Matter and Materials
3
1 Classification of Matter - Grade 10
1.1
1.2
5
Mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5
1.1.1
Heterogeneous mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . .
6
1.1.2
Homogeneous mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . .
6
1.1.3
Separating mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7
Pure Substances: Elements and Compounds . . . . . . . . . . . . . . . . . . . .
9
1.2.1
Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
1.2.2
Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
1.3
Giving names and formulae to substances . . . . . . . . . . . . . . . . . . . . . 10
1.4
Metals, Semi-metals and Non-metals . . . . . . . . . . . . . . . . . . . . . . . . 13
1.4.1
Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.4.2
Non-metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.4.3
Semi-metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.5
Electrical conductors, semi-conductors and insulators . . . . . . . . . . . . . . . 14
1.6
Thermal Conductors and Insulators . . . . . . . . . . . . . . . . . . . . . . . . . 15
1.7
Magnetic and Non-magnetic Materials . . . . . . . . . . . . . . . . . . . . . . . 17
1.8
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2 What are the objects around us made of? - Grade 10
21
2.1
Introduction: The atom as the building block of matter . . . . . . . . . . . . . . 21
2.2
Molecules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.2.1
Representing molecules . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.3
Intramolecular and intermolecular forces . . . . . . . . . . . . . . . . . . . . . . 25
2.4
The Kinetic Theory of Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.5
The Properties of Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.6
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3 The Atom - Grade 10
3.1
35
Models of the Atom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.1.1
The Plum Pudding Model . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.1.2
Rutherford’s model of the atom
v
. . . . . . . . . . . . . . . . . . . . . . 36
CONTENTS
3.1.3
3.2
3.3
CONTENTS
The Bohr Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
How big is an atom? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.2.1
How heavy is an atom? . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.2.2
How big is an atom? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Atomic structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.3.1
The Electron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.3.2
The Nucleus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.4
Atomic number and atomic mass number . . . . . . . . . . . . . . . . . . . . . 40
3.5
Isotopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.6
3.7
3.8
3.9
3.5.1
What is an isotope? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.5.2
Relative atomic mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Energy quantisation and electron configuration . . . . . . . . . . . . . . . . . . 46
3.6.1
The energy of electrons . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.6.2
Energy quantisation and line emission spectra . . . . . . . . . . . . . . . 47
3.6.3
Electron configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.6.4
Core and valence electrons . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.6.5
The importance of understanding electron configuration . . . . . . . . . 51
Ionisation Energy and the Periodic Table . . . . . . . . . . . . . . . . . . . . . . 53
3.7.1
Ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.7.2
Ionisation Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
The Arrangement of Atoms in the Periodic Table . . . . . . . . . . . . . . . . . 56
3.8.1
Groups in the periodic table
. . . . . . . . . . . . . . . . . . . . . . . . 56
3.8.2
Periods in the periodic table . . . . . . . . . . . . . . . . . . . . . . . . 58
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
4 Atomic Combinations - Grade 11
63
4.1
Why do atoms bond? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.2
Energy and bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.3
What happens when atoms bond? . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.4
Covalent Bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.4.1
The nature of the covalent bond . . . . . . . . . . . . . . . . . . . . . . 65
4.5
Lewis notation and molecular structure . . . . . . . . . . . . . . . . . . . . . . . 69
4.6
Electronegativity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.7
4.8
4.6.1
Non-polar and polar covalent bonds . . . . . . . . . . . . . . . . . . . . 73
4.6.2
Polar molecules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Ionic Bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.7.1
The nature of the ionic bond . . . . . . . . . . . . . . . . . . . . . . . . 74
4.7.2
The crystal lattice structure of ionic compounds . . . . . . . . . . . . . . 76
4.7.3
Properties of Ionic Compounds . . . . . . . . . . . . . . . . . . . . . . . 76
Metallic bonds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
4.8.1
The nature of the metallic bond . . . . . . . . . . . . . . . . . . . . . . 76
4.8.2
The properties of metals . . . . . . . . . . . . . . . . . . . . . . . . . . 77
vi
CONTENTS
4.9
CONTENTS
Writing chemical formulae
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
4.9.1
The formulae of covalent compounds . . . . . . . . . . . . . . . . . . . . 78
4.9.2
The formulae of ionic compounds . . . . . . . . . . . . . . . . . . . . . 80
4.10 The Shape of Molecules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
4.10.1 Valence Shell Electron Pair Repulsion (VSEPR) theory . . . . . . . . . . 82
4.10.2 Determining the shape of a molecule . . . . . . . . . . . . . . . . . . . . 82
4.11 Oxidation numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
4.12 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
5 Intermolecular Forces - Grade 11
91
5.1
Types of Intermolecular Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.2
Understanding intermolecular forces . . . . . . . . . . . . . . . . . . . . . . . . 94
5.3
Intermolecular forces in liquids . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
5.4
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
6 Solutions and solubility - Grade 11
101
6.1
Types of solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
6.2
Forces and solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
6.3
Solubility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
6.4
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
7 Atomic Nuclei - Grade 11
107
7.1
Nuclear structure and stability . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
7.2
The Discovery of Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
7.3
Radioactivity and Types of Radiation . . . . . . . . . . . . . . . . . . . . . . . . 108
7.4
7.3.1
Alpha (α) particles and alpha decay . . . . . . . . . . . . . . . . . . . . 109
7.3.2
Beta (β) particles and beta decay . . . . . . . . . . . . . . . . . . . . . 109
7.3.3
Gamma (γ) rays and gamma decay . . . . . . . . . . . . . . . . . . . . . 110
Sources of radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
7.4.1
Natural background radiation . . . . . . . . . . . . . . . . . . . . . . . . 112
7.4.2
Man-made sources of radiation . . . . . . . . . . . . . . . . . . . . . . . 113
7.5
The ’half-life’ of an element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
7.6
The Dangers of Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
7.7
The Uses of Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
7.8
Nuclear Fission
7.9
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
7.8.1
The Atomic bomb - an abuse of nuclear fission . . . . . . . . . . . . . . 119
7.8.2
Nuclear power - harnessing energy . . . . . . . . . . . . . . . . . . . . . 120
Nuclear Fusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
7.10 Nucleosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
7.10.1 Age of Nucleosynthesis (225 s - 103 s) . . . . . . . . . . . . . . . . . . . 121
7.10.2 Age of Ions (103 s - 1013 s) . . . . . . . . . . . . . . . . . . . . . . . . . 122
7.10.3 Age of Atoms (1013 s - 1015 s) . . . . . . . . . . . . . . . . . . . . . . . 122
7.10.4 Age of Stars and Galaxies (the universe today) . . . . . . . . . . . . . . 122
7.11 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
vii
CONTENTS
CONTENTS
8 Thermal Properties and Ideal Gases - Grade 11
125
8.1
A review of the kinetic theory of matter . . . . . . . . . . . . . . . . . . . . . . 125
8.2
Boyle’s Law: Pressure and volume of an enclosed gas . . . . . . . . . . . . . . . 126
8.3
Charles’s Law: Volume and Temperature of an enclosed gas . . . . . . . . . . . 132
8.4
The relationship between temperature and pressure . . . . . . . . . . . . . . . . 136
8.5
The general gas equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
8.6
The ideal gas equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
8.7
Molar volume of gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
8.8
Ideal gases and non-ideal gas behaviour . . . . . . . . . . . . . . . . . . . . . . 146
8.9
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
9 Organic Molecules - Grade 12
151
9.1
What is organic chemistry? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
9.2
Sources of carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
9.3
Unique properties of carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
9.4
Representing organic compounds . . . . . . . . . . . . . . . . . . . . . . . . . . 152
9.4.1
Molecular formula . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
9.4.2
Structural formula . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
9.4.3
Condensed structural formula . . . . . . . . . . . . . . . . . . . . . . . . 153
9.5
Isomerism in organic compounds . . . . . . . . . . . . . . . . . . . . . . . . . . 154
9.6
Functional groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
9.7
The Hydrocarbons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
9.7.1
The Alkanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
9.7.2
Naming the alkanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
9.7.3
Properties of the alkanes . . . . . . . . . . . . . . . . . . . . . . . . . . 163
9.7.4
Reactions of the alkanes . . . . . . . . . . . . . . . . . . . . . . . . . . 163
9.7.5
The alkenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
9.7.6
Naming the alkenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
9.7.7
The properties of the alkenes . . . . . . . . . . . . . . . . . . . . . . . . 169
9.7.8
Reactions of the alkenes
9.7.9
The Alkynes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
. . . . . . . . . . . . . . . . . . . . . . . . . . 169
9.7.10 Naming the alkynes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
9.8
9.9
The Alcohols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
9.8.1
Naming the alcohols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
9.8.2
Physical and chemical properties of the alcohols . . . . . . . . . . . . . . 175
Carboxylic Acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
9.9.1
Physical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
9.9.2
Derivatives of carboxylic acids: The esters . . . . . . . . . . . . . . . . . 178
9.10 The Amino Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
9.11 The Carbonyl Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
9.12 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
viii
CONTENTS
CONTENTS
10 Organic Macromolecules - Grade 12
185
10.1 Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
10.2 How do polymers form? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
10.2.1 Addition polymerisation . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
10.2.2 Condensation polymerisation . . . . . . . . . . . . . . . . . . . . . . . . 188
10.3 The chemical properties of polymers . . . . . . . . . . . . . . . . . . . . . . . . 190
10.4 Types of polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
10.5 Plastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
10.5.1 The uses of plastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
10.5.2 Thermoplastics and thermosetting plastics . . . . . . . . . . . . . . . . . 194
10.5.3 Plastics and the environment . . . . . . . . . . . . . . . . . . . . . . . . 195
10.6 Biological Macromolecules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
10.6.1 Carbohydrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
10.6.2 Proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
10.6.3 Nucleic Acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
10.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
III
Chemical Change
209
11 Physical and Chemical Change - Grade 10
211
11.1 Physical changes in matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
11.2 Chemical Changes in Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
11.2.1 Decomposition reactions . . . . . . . . . . . . . . . . . . . . . . . . . . 213
11.2.2 Synthesis reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
11.3 Energy changes in chemical reactions . . . . . . . . . . . . . . . . . . . . . . . . 217
11.4 Conservation of atoms and mass in reactions . . . . . . . . . . . . . . . . . . . . 217
11.5 Law of constant composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
11.6 Volume relationships in gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
11.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
12 Representing Chemical Change - Grade 10
223
12.1 Chemical symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
12.2 Writing chemical formulae
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
12.3 Balancing chemical equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
12.3.1 The law of conservation of mass . . . . . . . . . . . . . . . . . . . . . . 224
12.3.2 Steps to balance a chemical equation
. . . . . . . . . . . . . . . . . . . 226
12.4 State symbols and other information . . . . . . . . . . . . . . . . . . . . . . . . 230
12.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
13 Quantitative Aspects of Chemical Change - Grade 11
233
13.1 The Mole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
13.2 Molar Mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
13.3 An equation to calculate moles and mass in chemical reactions . . . . . . . . . . 237
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13.4 Molecules and compounds
CONTENTS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
13.5 The Composition of Substances . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
13.6 Molar Volumes of Gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246
13.7 Molar concentrations in liquids . . . . . . . . . . . . . . . . . . . . . . . . . . . 247
13.8 Stoichiometric calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
13.9 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
14 Energy Changes In Chemical Reactions - Grade 11
255
14.1 What causes the energy changes in chemical reactions? . . . . . . . . . . . . . . 255
14.2 Exothermic and endothermic reactions . . . . . . . . . . . . . . . . . . . . . . . 255
14.3 The heat of reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
14.4 Examples of endothermic and exothermic reactions . . . . . . . . . . . . . . . . 259
14.5 Spontaneous and non-spontaneous reactions . . . . . . . . . . . . . . . . . . . . 260
14.6 Activation energy and the activated complex . . . . . . . . . . . . . . . . . . . . 261
14.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
15 Types of Reactions - Grade 11
267
15.1 Acid-base reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
15.1.1 What are acids and bases? . . . . . . . . . . . . . . . . . . . . . . . . . 267
15.1.2 Defining acids and bases . . . . . . . . . . . . . . . . . . . . . . . . . . 267
15.1.3 Conjugate acid-base pairs . . . . . . . . . . . . . . . . . . . . . . . . . . 269
15.1.4 Acid-base reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270
15.1.5 Acid-carbonate reactions . . . . . . . . . . . . . . . . . . . . . . . . . . 274
15.2 Redox reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
15.2.1 Oxidation and reduction
. . . . . . . . . . . . . . . . . . . . . . . . . . 277
15.2.2 Redox reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278
15.3 Addition, substitution and elimination reactions . . . . . . . . . . . . . . . . . . 280
15.3.1 Addition reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280
15.3.2 Elimination reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281
15.3.3 Substitution reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282
15.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
16 Reaction Rates - Grade 12
287
16.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287
16.2 Factors affecting reaction rates . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
16.3 Reaction rates and collision theory . . . . . . . . . . . . . . . . . . . . . . . . . 293
16.4 Measuring Rates of Reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
16.5 Mechanism of reaction and catalysis . . . . . . . . . . . . . . . . . . . . . . . . 297
16.6 Chemical equilibrium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
16.6.1 Open and closed systems . . . . . . . . . . . . . . . . . . . . . . . . . . 302
16.6.2 Reversible reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302
16.6.3 Chemical equilibrium . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
16.7 The equilibrium constant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
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CONTENTS
16.7.1 Calculating the equilibrium constant . . . . . . . . . . . . . . . . . . . . 305
16.7.2 The meaning of kc values . . . . . . . . . . . . . . . . . . . . . . . . . . 306
16.8 Le Chatelier’s principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
16.8.1 The effect of concentration on equilibrium . . . . . . . . . . . . . . . . . 310
16.8.2 The effect of temperature on equilibrium . . . . . . . . . . . . . . . . . . 310
16.8.3 The effect of pressure on equilibrium . . . . . . . . . . . . . . . . . . . . 312
16.9 Industrial applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
16.10Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316
17 Electrochemical Reactions - Grade 12
319
17.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
17.2 The Galvanic Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
17.2.1 Half-cell reactions in the Zn-Cu cell . . . . . . . . . . . . . . . . . . . . 321
17.2.2 Components of the Zn-Cu cell . . . . . . . . . . . . . . . . . . . . . . . 322
17.2.3 The Galvanic cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
17.2.4 Uses and applications of the galvanic cell . . . . . . . . . . . . . . . . . 324
17.3 The Electrolytic cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
17.3.1 The electrolysis of copper sulphate . . . . . . . . . . . . . . . . . . . . . 326
17.3.2 The electrolysis of water . . . . . . . . . . . . . . . . . . . . . . . . . . 327
17.3.3 A comparison of galvanic and electrolytic cells . . . . . . . . . . . . . . . 328
17.4 Standard Electrode Potentials . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
17.4.1 The different reactivities of metals . . . . . . . . . . . . . . . . . . . . . 329
17.4.2 Equilibrium reactions in half cells . . . . . . . . . . . . . . . . . . . . . . 329
17.4.3 Measuring electrode potential . . . . . . . . . . . . . . . . . . . . . . . . 330
17.4.4 The standard hydrogen electrode . . . . . . . . . . . . . . . . . . . . . . 330
17.4.5 Standard electrode potentials . . . . . . . . . . . . . . . . . . . . . . . . 333
17.4.6 Combining half cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
17.4.7 Uses of standard electrode potential . . . . . . . . . . . . . . . . . . . . 338
17.5 Balancing redox reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
17.6 Applications of electrochemistry . . . . . . . . . . . . . . . . . . . . . . . . . . 347
17.6.1 Electroplating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347
17.6.2 The production of chlorine . . . . . . . . . . . . . . . . . . . . . . . . . 348
17.6.3 Extraction of aluminium
. . . . . . . . . . . . . . . . . . . . . . . . . . 349
17.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
IV
Chemical Systems
353
18 The Water Cycle - Grade 10
355
18.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
18.2 The importance of water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
18.3 The movement of water through the water cycle . . . . . . . . . . . . . . . . . . 356
18.4 The microscopic structure of water . . . . . . . . . . . . . . . . . . . . . . . . . 359
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18.4.1 The polar nature of water . . . . . . . . . . . . . . . . . . . . . . . . . . 359
18.4.2 Hydrogen bonding in water molecules . . . . . . . . . . . . . . . . . . . 359
18.5 The unique properties of water . . . . . . . . . . . . . . . . . . . . . . . . . . . 360
18.6 Water conservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363
18.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
19 Global Cycles: The Nitrogen Cycle - Grade 10
369
19.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
19.2 Nitrogen fixation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
19.3 Nitrification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371
19.4 Denitrification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372
19.5 Human Influences on the Nitrogen Cycle . . . . . . . . . . . . . . . . . . . . . . 372
19.6 The industrial fixation of nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . 373
19.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374
20 The Hydrosphere - Grade 10
377
20.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377
20.2 Interactions of the hydrosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . 377
20.3 Exploring the Hydrosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378
20.4 The Importance of the Hydrosphere . . . . . . . . . . . . . . . . . . . . . . . . 379
20.5 Ions in aqueous solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
20.5.1 Dissociation in water . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380
20.5.2 Ions and water hardness . . . . . . . . . . . . . . . . . . . . . . . . . . . 382
20.5.3 The pH scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382
20.5.4 Acid rain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384
20.6 Electrolytes, ionisation and conductivity . . . . . . . . . . . . . . . . . . . . . . 386
20.6.1 Electrolytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386
20.6.2 Non-electrolytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387
20.6.3 Factors that affect the conductivity of water . . . . . . . . . . . . . . . . 387
20.7 Precipitation reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389
20.8 Testing for common anions in solution . . . . . . . . . . . . . . . . . . . . . . . 391
20.8.1 Test for a chloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391
20.8.2 Test for a sulphate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391
20.8.3 Test for a carbonate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392
20.8.4 Test for bromides and iodides . . . . . . . . . . . . . . . . . . . . . . . . 392
20.9 Threats to the Hydrosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393
20.10Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394
21 The Lithosphere - Grade 11
397
21.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397
21.2 The chemistry of the earth’s crust . . . . . . . . . . . . . . . . . . . . . . . . . 398
21.3 A brief history of mineral use . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399
21.4 Energy resources and their uses . . . . . . . . . . . . . . . . . . . . . . . . . . . 400
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21.5 Mining and Mineral Processing: Gold . . . . . . . . . . . . . . . . . . . . . . . . 401
21.5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401
21.5.2 Mining the Gold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401
21.5.3 Processing the gold ore . . . . . . . . . . . . . . . . . . . . . . . . . . . 401
21.5.4 Characteristics and uses of gold . . . . . . . . . . . . . . . . . . . . . . . 402
21.5.5 Environmental impacts of gold mining . . . . . . . . . . . . . . . . . . . 404
21.6 Mining and mineral processing: Iron . . . . . . . . . . . . . . . . . . . . . . . . 406
21.6.1 Iron mining and iron ore processing . . . . . . . . . . . . . . . . . . . . . 406
21.6.2 Types of iron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407
21.6.3 Iron in South Africa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408
21.7 Mining and mineral processing: Phosphates . . . . . . . . . . . . . . . . . . . . 409
21.7.1 Mining phosphates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409
21.7.2 Uses of phosphates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409
21.8 Energy resources and their uses: Coal . . . . . . . . . . . . . . . . . . . . . . . 411
21.8.1 The formation of coal . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411
21.8.2 How coal is removed from the ground . . . . . . . . . . . . . . . . . . . 411
21.8.3 The uses of coal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412
21.8.4 Coal and the South African economy . . . . . . . . . . . . . . . . . . . . 412
21.8.5 The environmental impacts of coal mining . . . . . . . . . . . . . . . . . 413
21.9 Energy resources and their uses: Oil . . . . . . . . . . . . . . . . . . . . . . . . 414
21.9.1 How oil is formed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414
21.9.2 Extracting oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414
21.9.3 Other oil products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415
21.9.4 The environmental impacts of oil extraction and use . . . . . . . . . . . 415
21.10Alternative energy resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415
21.11Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417
22 The Atmosphere - Grade 11
421
22.1 The composition of the atmosphere . . . . . . . . . . . . . . . . . . . . . . . . 421
22.2 The structure of the atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . 422
22.2.1 The troposphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
22.2.2 The stratosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
22.2.3 The mesosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424
22.2.4 The thermosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424
22.3 Greenhouse gases and global warming . . . . . . . . . . . . . . . . . . . . . . . 426
22.3.1 The heating of the atmosphere . . . . . . . . . . . . . . . . . . . . . . . 426
22.3.2 The greenhouse gases and global warming . . . . . . . . . . . . . . . . . 426
22.3.3 The consequences of global warming . . . . . . . . . . . . . . . . . . . . 429
22.3.4 Taking action to combat global warming . . . . . . . . . . . . . . . . . . 430
22.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431
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23 The Chemical Industry - Grade 12
435
23.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435
23.2 Sasol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435
23.2.1 Sasol today: Technology and production . . . . . . . . . . . . . . . . . . 436
23.2.2 Sasol and the environment . . . . . . . . . . . . . . . . . . . . . . . . . 440
23.3 The Chloralkali Industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442
23.3.1 The Industrial Production of Chlorine and Sodium Hydroxide . . . . . . . 442
23.3.2 Soaps and Detergents . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446
23.4 The Fertiliser Industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450
23.4.1 The value of nutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450
23.4.2 The Role of fertilisers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450
23.4.3 The Industrial Production of Fertilisers . . . . . . . . . . . . . . . . . . . 451
23.4.4 Fertilisers and the Environment: Eutrophication . . . . . . . . . . . . . . 454
23.5 Electrochemistry and batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . 456
23.5.1 How batteries work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456
23.5.2 Battery capacity and energy . . . . . . . . . . . . . . . . . . . . . . . . 457
23.5.3 Lead-acid batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457
23.5.4 The zinc-carbon dry cell . . . . . . . . . . . . . . . . . . . . . . . . . . . 459
23.5.5 Environmental considerations . . . . . . . . . . . . . . . . . . . . . . . . 460
23.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461
A GNU Free Documentation License
467
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Chapter 22
The Atmosphere - Grade 11
Our earth is truly an amazing planet! Not only is it exactly the right distance from the sun to
have temperatures that will support life, but it is also one of the only planets to have liquid water
on its surface. In addition, our earth has an atmosphere that has just the right composition to
allow life to exist. The atmosphere is the layer of gases that surrounds the earth. We may not
always be aware of them, but without these gases, life on earth would definitely not be possible.
The atmosphere provides the gases that animals and plants need for respiration (breathing) and
photosynthesis (the production of food), it helps to keep temperatures on earth constant and
also protects us from the sun’s harmful radiation.
In this chapter, we are going to take a closer look at the chemistry of the earth’s atmosphere
and at some of the human activities that threaten the delicate balance that exists in this part of
our planet.
22.1
The composition of the atmosphere
Earth’s atmosphere is a mixture of gases. Two important gases are nitrogen and oxygen, which
make up about 78.1% and 20.9% of the atmosphere respectively. A third gas, Argon, contributes
about 0.9%, and a number of other gases such as carbon dioxide, methane, water vapour, helium
and ozone make up the remaining 0.1%. In an earlier chapter, we discussed the importance of
nitrogen as a component of proteins, the building blocks of life. Similarly, oxygen is essential for
life because it is the gas we need for respiration. We will discuss the importance of some of the
other gases later in this chapter.
teresting
Interesting
Fact
Fact
The earth’s early atmosphere was very different from what it is today. When the earth
formed around 4.5 billion years ago, there was probably no atmosphere. Some scientists
believe that the earliest atmosphere contained gases such as water vapour, carbon dioxide,
nitrogen and sulfur which were released from inside the planet as a result of volcanic activity.
Many scientists also believe that the first stage in the evolution of life, around 4 billion
years ago, needed an oxygen-free environment. At a later stage, these primitive forms of
plant life began to release small amounts of oxygen into the atmosphere as a product of
photosynthesis. During photosynthesis, plants use carbon dioxide, water and sunlight to
produce simple sugars. Oxygen is also released in the process.
6CO2 + 6H2 O + sunlight → C6 H12 O6 + 6O2
This build-up of oxygen in the atmosphere eventually led to the formation of the ozone layer,
which helped to filter the sun’s harmful UV radiation so that plants were able to flourish
421
22.2
CHAPTER 22. THE ATMOSPHERE - GRADE 11
in different environments. As plants became more widespread and photosythesis increased,
so did the production of oxygen. The increase in the amount of oxygen in the atmosphere
would have allowed more forms of life to exist.
If you have ever had to climb to a very high altitude (altitude means the ’height’ in the atmosphere), you will have noticed that it becomes very difficult to breathe, and many climbers suffer
from ’altitude sickness’ before they reach their destination. This is because the density of gases
becomes less as you move higher in the atmosphere. It is gravity that holds the atmosphere
close to the earth. As you move higher, this force weakens slightly and so the gas particles
become more spread out. In effect, when you are at a high altitude, the gases in the atmosphere
haven’t changed, but there are fewer oxygen molecules in the same amount of air that you are
able to breathe.
Definition: Earth’s atmosphere
The Earth’s atmosphere is a layer of gases that surround the planet, and which are held there
by the Earth’s gravity. The atmosphere contains roughly 78.1% nitrogen, 20.9% oxygen,
0.9% argon, 0.038% carbon dioxide, trace amounts of other gases, and a variable amount of
water vapour. This mixture of gases is commonly known as air. The atmosphere protects
life on Earth by absorbing ultraviolet solar radiation and reducing temperature extremes
between day and night.
22.2
The structure of the atmosphere
The earth’s atmosphere is divided into different layers, each with its own particular characteristics
(figure 22.1).
22.2.1
The troposphere
The troposphere is the lowest level in the atmosphere, and it is the part in which we live. The
troposphere varies in thickness, and extends from the ground to a height of about 7km at the
poles and about 18km at the equator. An important characteristic of the troposphere is that its
temperature decreases with an increase in altitude. In other words, as you climb higher, it will
get colder. You will have noticed this if you have climbed a mountain, or if you have moved
from a city at a high altitude to one which is lower; the average temperature is often lower where
the altitude is higher. This is because the troposphere is heated from the ’bottom up’. In other
words, places that are closer to the Earth’s surface will be warmer than those at higher altitudes.
The heating of the atmosphere will be discussed in more detail later in this chapter.
The word troposphere comes from the Greek tropos, meaning turning or mixing. The troposphere is the most turbulent part of the atmosphere and is the part where our weather takes
place. Weather is the state of the air at a particular place and time e.g. if it is warm or cold,
wet or dry, and how cloudy or windy it is. Generally, jet aircraft fly just above the troposphere
to avoid all this turbulence.
22.2.2
The stratosphere
Above the troposphere is another layer called the stratosphere, where most long distance aircraft fly. The stratosphere extends from altitudes of 10 to 50km. If you have ever been in an
aeroplane and have looked out the window once you are well into the flight, you will have noticed
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CHAPTER 22. THE ATMOSPHERE - GRADE 11
22.2
120
110
Thermosphere
100
90
80
70
Mesosphere
Height (km)
60
50
40
Stratosphere
30
20
Troposphere
10
0
-100
-90
-80
-70
-60
-50
-40
-30
-20
Temperature (◦ C)
-10
0
10
20
Figure 22.1: A generalised diagram showing the structure of the atmosphere to a height of 110
km
that you are actually flying above the level of the clouds. As we have already mentioned, clouds
and weather occur in the troposphere, whereas the stratosphere has very stable atmospheric
conditions and very little turbulence. It is easy to understand why aircraft choose to fly here!
The stratosphere is different from the troposphere because its temperature increases as altitude
increases. This is because the stratosphere absorbs solar radiation directly, meaning that the
upper layers closer to the sun will be warmer. The upper layers of the stratosphere are also
warmer because of the presence of the ozone layer. Ozone (O3 ) is formed when solar radiation
splits an oxygen molecule (O2 ) into two atoms of oxygen. Each individual atom is then able to
combine with an oxygen molecule to form ozone. The two reactions are shown below:
O2 → O + O
O + O2 → O3
The change from one type of molecule to another produces energy, and this contributes to higher
temperatures in the upper part of the stratosphere. An important function of the ozone layer
is to absorb UV radiation and reduce the amount of harmful radiation that reaches the Earth’s
surface.
Extension: CFCs and the ozone layer
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CHAPTER 22. THE ATMOSPHERE - GRADE 11
You may have heard people talking about ’the hole in the ozone layer’. What do
they mean by this and do we need to be worried about it?
Most of the earth’s ozone is found in the stratosphere and this limits the amount
of UV radiation that reaches the earth. However, human activities have once again
disrupted the chemistry of the atmosphere. Chlorofluorocarbons (CFC’s) are compounds found in aerosol cans, fridges and airconditioners. In aerosol cans, it is the
CFC’s that cause the substance to be sprayed outwards. The bad side of CFC’s is
that, when they are released into the atmosphere, they break down ozone molecules
so that the ozone is no longer able to protect us as much from UV rays. The ’ozone
hole’ is actually a thinning of the ozone layer approximately above Antarctica. Let’s
take a closer look at the chemical reactions that are involved in breaking down ozone:
1. When CFC’s react with UV radiation, a carbon-chlorine bond in the chlorofluorocarbon breaks and a new compound is formed, with a chlorine atom.
CF Cl3 + U V → CF Cl2 + Cl
2. The single chlorine atom reacts with ozone to form a molecule of chlorine
monoxide and oxygen gas. In the process, ozone is destroyed.
Cl + O3 → ClO + O2
3. The chlorine monoxide then reacts with a free oxygen atom (UV radiation
breaks O2 down into single oxygen atoms) to form oxygen gas and a single
chlorine atom.
ClO + O → Cl + O2
4. The chlorine atom is then free to attack more ozone molecules, and the process
continues. A single CFC molecule can destroy 100 000 ozone molecules.
One possible consequence of ozone depletion is an increase in the incidence
of skin cancer because there is more UV radiation reaching earth’s surface. CFC
replacements are now being used to reduce emissions, and scientists are trying to
find ways to restore ozone levels in the atmosphere.
22.2.3
The mesosphere
The mesosphere is located about 50-80/85km above Earth’s surface. Within this layer, temperature decreases with increasing altitude. Temperatures in the upper mesosphere can fall as
low as -100◦C in some areas. Millions of meteors burn up daily in the mesosphere because of
collisions with the gas particles that are present in this layer. This leads to a high concentration
of iron and other metal atoms.
22.2.4
The thermosphere
The thermosphere exists at altitudes above 80 km. In this part of the atmosphere, ultraviolet
(UV) and shorter X-Ray radiation from the sun cause neutral gas atoms to be ionised. At these
radiation frequencies, photons from the solar radiation are able to dislodge electrons from neutral atoms and molecules during a collision. A plasma is formed, which consists of negative free
electrons and positive ions. This part of the atmosphere is called the ionosphere. At the same
time that ionisation takes place however, an opposing process called recombination also begins.
Some of the free electrons are drawn to the positive ions, and combine again with them if they
are in close enough contact. Since the gas density increases at lower altitudes, the recombination process occurs more often here because the gas molecules and ions are closer together. The
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CHAPTER 22. THE ATMOSPHERE - GRADE 11
22.2
ionisation process produces energy which means that the upper parts of the thermosphere, which
are dominated by ionisation, have a higher temperature than the lower layers where recombination takes place. Overall, temperature in the thermosphere increases with an increase in altitude.
Extension: The ionosphere and radio waves
The ionosphere is of practical importance because it allows radio waves to be transmitted. A radio wave is a type of electromagnetic radiation that humans use to
transmit information without wires. When using high-frequency bands, the ionosphere is used to reflect the transmitted radio beam. When a radio wave reaches
the ionosphere, the electric field in the wave forces the electrons in the ionosphere
into oscillation at the same frequency as the radio wave. Some of the radio wave
energy is given up to this mechanical oscillation. The oscillating electron will then
either recombine with a positive ion, or will re-radiate the original wave energy back
downward again. The beam returns to the Earth’s surface, and may then be reflected
back into the ionosphere for a second bounce.
teresting
Interesting
Fact
Fact
The ionosphere is also home to the auroras. Auroras are caused by the collision of charged
particles (e.g. electrons) with atoms in the earth’s upper atmosphere. Charged particles are
energised and so, when they collide with atoms, the atoms also become energised. Shortly
afterwards, the atoms emit the energy they have gained, as light. Often these emissions
are from oxygen atoms, resulting in a greenish glow (wavelength 557.7 nm) and, at lower
energy levels or higher altitudes, a dark red glow (wavelength 630 nm). Many other colours
can also be observed. For example, emissions from atomic nitrogen are blue, and emissions
from molecular nitrogen are purple. Auroras emit visible light (as described above), and
also infra-red, ultraviolet and x-rays, which can be observed from space.
Exercise: The composition of the atmosphere
1. Complete the following summary table by providing the missing information for
each layer in the atmosphere.
Atmospheric
Height (km)
Gas composition General characlayer
teristics
Troposphere
0-18
Turbulent; part
of
atmosphere
where weather
occurs
Ozone reduces
harmful radiation
reaching Earth
Mesosphere
High
concentration of metal
atoms
more than 80
km
2. Use your knowledge of the atmosphere to explain the following statements:
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CHAPTER 22. THE ATMOSPHERE - GRADE 11
(a) Athletes who live in coastal areas need to acclimatise if they are competing
at high altitudes.
(b) Higher incidences of skin cancer have been recorded in areas where the
ozone layer in the atmosphere is thin.
(c) During a flight, turbulence generally decreases above a certain altitude.
22.3
Greenhouse gases and global warming
22.3.1
The heating of the atmosphere
As we mentioned earlier, the distance of the earth from the sun is not the only reason that
temperatures on earth are within a range that is suitable to support life. The composition of the
atmosphere is also critically important.
The earth receives electromagnetic energy from the sun in the visible spectrum. There are also
small amounts of infrared and ultraviolet radiation in this incoming solar energy. Most of the
radiation is shortwave radiation, and it passes easily through the atmosphere towards the earth’s
surface, with some being reflected before reaching the surface. At the surface, some of the energy is absorbed, and this heats up the earth’s surface. But the situation is a little more complex
than this.
A large amount of the sun’s energy is re-radiated from the surface back into the atmosphere as
infrared radiation, which is invisible. As this radiation passes through the atmosphere, some of
it is absorbed by greenhouse gases such as carbon dioxide, water vapour and methane. These
gases are very important because they re-emit the energy back towards the surface. By doing
this, they help to warm the lower layers of the atmosphere even further. It is this ’re-emission’ of
heat by greenhouse gases, combined with surface heating and other processes (e.g. conduction
and advection) that maintain temperatures at exactly the right level to support life. Without
the presence of greenhouse gases, most of the sun’s energy would be lost and the Earth would
be a lot colder than it is! A simplified diagram of the heating of the atmosphere is shown in
figure 22.2.
22.3.2
The greenhouse gases and global warming
Many of the greenhouse gases occur naturally in small quantities in the atmosphere. However,
human activities have greatly increased their concentration, and this has led to a lot of concern
about the impact that this could have in increasing global temperatures. This phenomenon is
known as global warming. Because the natural concentrations of these gases are low, even a
small increase in their concentration as a result of human emissions, could have a big effect on
temperature. But before we go on, let’s look at where some of these human gas emissions come
from.
• Carbon dioxide (CO2 )
Carbon dioxide enters the atmosphere through the burning of fossil fuels (oil, natural gas,
and coal), solid waste, trees and wood products, and also as a result of other chemical
reactions (e.g. the manufacture of cement). Carbon dioxide can also be removed from
the atmosphere when it is absorbed by plants during photosynthesis.
• Methane (CH4 )
Methane is emitted when coal, natural gas and oil are produced and transported. Methane
emissions can also come from livestock and other agricultural practices and from the decay
of organic waste.
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CHAPTER 22. THE ATMOSPHERE - GRADE 11
22.3
sun
Outgoing long-wave
infrared radiation
Incoming
short-wave
solar radiation
atmosphere
infrared radiation
is absorbed and
re-emitted by
greenhouse gases
in the atmosphere
earth’s surface
Figure 22.2: The heating of the Earth’s atmosphere
• Nitrous oxide (N2 O)
Nitrous oxide is emitted by agriculture and industry, and when fossil fuels and solid waste
are burned.
• Fluorinated gases (e.g. hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride)
These gases are all synthetic, in other words they are man-made. They are emitted from a
variety of industrial processes. Fluorinated gases are sometimes used in the place of other
ozone-depleting substances (e.g. CFC’s). These are very powerful greenhouse gases, and
are sometimes referred to as High Global Warming Potential gases (’High GWP gases’).
Overpopulation is a major problem in reducing greenhouse gas emissions, and in slowing down
global warming. As populations grow, their demands on resources (e.g. energy) increase, and
so does their production of greenhouse gases.
Extension: Ice core drilling - Taking a look at earth’s past climate
Global warming is a very controversial issue. While many people are convinced
that the increase in average global temperatures is directly related to the increase in
atmospheric concentrations of carbon dioxide, others argue that the climatic changes
we are seeing are part of a natural pattern. One way in which scientists are able to
understand what is happening at present, is to understand the earth’s past atmosphere, and the factors that affected its temperature.
So how, you may be asking, do we know what the earth’s past climate was like?
One method that is used is ice core drilling. Antarctica is the coldest continent
on earth, and because of this there is very little melting that takes place. Over
thousands of years, ice has accumulated in layers and has become more and more
compacted as new ice is added. This is partly why Antarctica is also on average one
of the highest continents! On average, the ice sheet that covers Antarctica is 2500
m thick, and at its deepest location, is 4700 m thick.
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CHAPTER 22. THE ATMOSPHERE - GRADE 11
As the snow is deposited on top of the ice sheet each year, it traps different
chemicals and impurities which are dissolved in the ice. The ice and impurities hold
information about the Earth’s environment and climate at the time that the ice was
deposited. Drilling an ice core from the surface down, is like taking a journey back
in time. The deeper into the ice you venture, the older the layer of ice. By analysing
the gases and oxygen isotopes that are present (along with many other techniques)
in the ice at various points in the earth’s history, scientists can start to piece together
a picture of what the earth’s climate must have been like.
Top layers are the most
recently deposited
Increasing age
Bottom layers are
the oldest
One of the most well known ice cores was the one drilled at a Russian station
called Vostok in central Antarctica. So far, data has been gathered for dates as far
back as 160 000 years!
Activity :: Case Study : Looking at past climatic trends
Make sure that you have read the ’Information box’ on ice core drilling before
you try this activity.
The values in the table below were extrapolated from data obtained by scientists
studying the Vostok ice core. ’Local temperature change’ means by how much the
temperature at that time was different from what it is today. For example, if the
local temperature change 160 000 years ago was -9◦ C, this means that atmospheric
temperatures at that time were 9◦ C lower than what they are today. ’ppm’ means
’parts per million’ and is a unit of measurement for gas concentrations.
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CHAPTER 22. THE ATMOSPHERE - GRADE 11
Years before present
(x 1000)
Local temperature
change (◦ C)
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0 (1850)
Present
-9
-10
-10
-3
+1
-4
-8
-5
-6
-8
-9
-7
-8
-7
-9
-2
-0.5
22.3
Carbon
dioxide
(ppm)
190
205
240
280
278
240
225
230
220
250
190
220
180
225
200
260
280
371
Questions
1. On the same set of axes, draw graphs to show how temperature and carbon
dioxide concentrations have changed over the last 160 000 years. Hint: ’Years
before present’ will go on the x-axis, and should be given negative values.
2. Compare the graphs that you have drawn. What do you notice?
3. Is there a relationship between temperature and the atmospheric concentration
of carbon dioxide?
4. Do these graphs prove that temperature changes are determined by the concentration of gases such as carbon dioxide in the atmosphere? Explain your
answer.
5. What other factors might you need to consider when analysing climatic trends?
22.3.3
The consequences of global warming
Activity :: Group Discussion : The impacts of global warming
In groups of 3-4, read the following extracts and then answer the questions that
follow.
By 2050 Warming to Doom Million Species, Study Says
By 2050, rising temperatures exacerbated by human-induced belches of
carbon dioxide and other greenhouse gases could send more than a million
of Earth’s land-dwelling plants and animals down the road to extinction,
according to a recent study. ”Climate change now represents at least
as great a threat to the number of species surviving on Earth as habitatdestruction and modification,” said Chris Thomas, a conservation biologist
at the University of Leeds in the United Kingdom.
The researchers worked independently in six biodiversity-rich regions around
the world, from Australia to South Africa, plugging field data on species
distribution and regional climate into computer models that simulated the
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CHAPTER 22. THE ATMOSPHERE - GRADE 11
ways species’ ranges are expected to move in response to temperature and
climate changes. According to the researchers’ collective results, the predicted range of climate change by 2050 will place 15 to 35 percent of the
1 103 species studied at risk of extinction.
National Geographic News, 12 July 2004
Global Warming May Dry Up Africa’s Rivers, Study Suggests
Many climate scientists already predict that less rain will fall annually in
parts of Africa within 50 years due to global warming. Now new research
suggests that even a small decrease in rainfall on the continent could
cause a drastic reduction in river water, the lifeblood for rural populations
in Africa.
A decrease in water availability could occur across about 25 percent of
the continent, according to the new study. Hardest hit would be areas in
northwestern and southern Africa, with some of the most serious effects
striking large areas of Botswana and South Africa.
To predict future rainfall, the scientists compared 21 of what they consider
to be the best climate change models developed by research teams around
the world. On average, the models forecast a 10 to 20% drop in rainfall
in northwestern and southern Africa by 2070. With a 20% decrease, Cape
Town would be left with just 42% of its river water, and ”Botswana would
completely dry up,” de Wit said. In parts of northern Africa, river water
levels would drop below 50%.
Less river water would have serious implications not just for people but
for the many animal species whose habitats rely on regular water supplies.
National Geographic News, 3 March 2006
Discussion questions
1. What is meant by ’biodiversity’ ?
2. Explain why global warming is likely to cause a loss of biodiversity.
3. Why do you think a loss of biodiversity is of such concern to conservationists?
4. Suggest some plant or animal species in South Africa that you think might be
particularly vulnerable to extinction if temperatures were to rise significantly.
Explain why you chose these species.
5. In what way do people, animals and plants rely on river water?
6. What effect do you think a 50% drop in river water level in some parts of Africa
would have on the people living in these countries?
7. Discuss some of the other likely impacts of global warming that we can expect
(e.g. sea level rise, melting of polar ice caps, changes in ocean currents).
22.3.4
Taking action to combat global warming
Global warming is a major concern at present. A number of organisations, panels and research
bodies have been working to gather accurate and relevant information so that a true picture of
our current situation can be painted. One important orgaisation that you may have heard of
is the Intergovernmental Panel on Climate Change (IPCC). The IPCC was established in
1988 by two United Nations organizations, the World Meteorological Organization (WMO) and
the United Nations Environment Programme (UNEP), to evaluate the risk of climate change
brought on by humans. You may also have heard of the Kyoto Protocol, which will be discussed
a little later.
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CHAPTER 22. THE ATMOSPHERE - GRADE 11
22.4
Activity :: Group Discussion : World carbon dioxide emissions
The data in the table below shows carbon dioxide emissions from the consumption
of fossil fuels (in million metric tons of carbon dioxide).
Region or Country
United States
Brazil
France
UK
Saudi Arabia
Botswana
South Africa
India
World Total
1980
4754
186
487
608
175
1.26
234
299
18333
1985
4585
187
394
588
179
1.45
298
439
19412
1990
5013
222
368
598
207
2.68
295
588
21426
1995
5292
288
372
555
233
3.44
344
867
22033
2000
5815
345
399
551
288
4.16
378
1000
23851
2004
5912
336
405
579
365
3.83
429
1112
27043
Questions
1. Using a coloured pen, highlight those countries that are ’developed’ and those
that are ’developing’.
2. Explain why CO2 emissions are so much higher in developed countries than in
developing countries.
3. How does South Africa compare to the other developing countries, and also to
the developed countries?
Carbon dioxide emissions are a major problem worldwide. The Kyoto Protocol
was signed in Kyoto, Japan in December 1997. Its main objective was to reduce
global greenhouse gas emissions by encouraging countries to become signatories to
the guidelines that had been laid out in the protocol. These guidelines set targets for
the world’s major producers to reduce their emissions within a certain time. However,
some of the worst contributors to greenhouse gas emissions (e.g. USA) were not
prepared to sign the protocol, partly because of the potential effect this would have on
the country’s economy, which relies on industry and other ’high emission’ activities.
Panel discussion
Form groups with 5 people in each. Each person in the group must adopt one
of the following roles during the discussion:
• the owner of a large industry
• an environmental scientist
• an economist
• a politician
• a chairperson for the discussion
In your group, you are going to discuss some of the economic and environmental
implications for a country that decides to sign the Kyoto Protocol. Each person will
have the opportunity to express the view of the character they have adopted. You
may ask questions of the other people, or challenge their ideas, provided that you
ask permission from the chairperson first.
22.4
Summary
• The atmosphere is the layer of gases that surrounds Earth. These gases are important in
sustaining life, regulating temperature and protecting Earth from harmful radiation.
• The gases that make up the atmosphere are nitrogen, oxygen, carbon dioxide and others
e.g. water vapour, methane.
• There are four layer in the atmosphere, each with their own characteristics.
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• The troposphere is the lowest layer and here, temperature decreases with an increase in
altitude. The troposphere is where weather occurs.
• The next layer is the stratosphere where temperature increases with an increase in altitude
because of the presence of ozone in this layer, and the direct heating from the sun.
• The depletion of the ozone layer is largely because of CFC’s, which break down ozone
through a series of chemical reactions.
• The mesosphere is characterised by very cold temperatures and meteor collisions. The
mesosphere contains high concentrations of metal atoms.
• In the thermosphere, neutral atoms are ionised by UV and X-ray radiation from the sun.
Temperature increases with an increase in altitude because of the energy that is released
during this ionisation process, which occurs mostly in the upper thermosphere.
• The thermosphere is also known as the ionosphere, and is the part of the atmosphere
where radio waves can be transmitted.
• The auroras are bright coloured skies that occur when charged particles collide with atoms
in the upper atmosphere. Depending on the type of atom, energy is released as light at
different wavelengths.
• The Earth is heated by radiation from the sun. Incoming radiation has a short wavelength
and some is absorbed directly by the Earth’s surface. However, a large amount of energy
is re-radiated as longwave infrared radiation.
• Greenhouse gases such as carbon dioxide, water vapour and methane absorb infrared
radiation and re-emit it back towards the Earth’s surface. In this way, the bottom layers
of the atmsophere are kept much warmer than they would be if all the infrared radiation
was lost.
• Human activities such as the burning of fossil fuels, increase the concentration of greenhouse gases in the atmosphere and may contribute towards global warming.
• Some of the impacts of global warming include changing climate patterns, rising sea levels and a loss of biodiversity, to name a few. Interventions are needed to reduce this
phenomenon.
Exercise: Summary Exercise
1. The atmosphere is a relatively thin layer of gases which support life and provide protection to living organisms. The force of gravity holds the atmosphere
against the earth. The diagram below shows the temperatures associated with
the various layers that make up the atmosphere and the altitude (height) from
the earth’s surface.
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CHAPTER 22. THE ATMOSPHERE - GRADE 11
22.4
120
E
110
100
D
90
80
70
C
Height (km) 60
50
40
B
30
20
10
0
-100
-90 -80 -70 -60 -50 -40 -30 -20 -10
Temperature (◦ C)
A
0
10 20
(a) Write down the names of the layers A, B and D of the atmosphere.
(b) In which one of the layers of the atmosphere is ozone found?
(c) Give an explanation for the decrease in temperature as altitude increases
in layer A.
(d) In layer B, there is a steady increase in temperature as the altitude increases. Write down an explanation for this trend.
2.
Planet Earth in Danger
It is now accepted that greenhouse gases are to blame for planet earth
getting warmer. The increase in the number of sudden floods in Asia
and droughts in Africa; the rising sea level and increasing average temperatures are global concerns. Without natural greenhouse gases,like
carbon dioxide and water vapour,life on earth is not possible. However, the increase in levels of carbon dioxide in the atmosphere since
the Industrial Revolution is of great concern. Greater disasters are to
come, which will create millions of climate refugees. It is our duty to
take action for the sake of future generations who will pay dearly for
the wait-and-see attitude of the current generation. Urgent action to
reduce waste is needed. Global warming is a global challenge and calls
for a global response now, not later.
(Adapted from a speech by the French President, Jacques Chirac)
(a) How do greenhouse gases, such as carbon dioxide, heat up the earth’s
surface?
(b) Draw a Lewis structure for the carbon dioxide molecule
(c) The chemical bonds within the carbon dioxide molecule are polar. Support
this statement by performing a calculation using the table of electronegativities.
(d) Classify the carbon dioxide molecule as polar or non-polar. Give a reason
for your answer.
(e) Suggest ONE way in which YOU can help to reduce the emissions of
greenhouse gases.
3. Plants need carbon dioxide (CO2 ) to manufacture food. However, the engines of motor vehicles cause too much carbon dioxide to be released into the
atmosphere.
(a) State the possible consequence of having too much carbon dioxide in the
atmosphere.
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22.4
CHAPTER 22. THE ATMOSPHERE - GRADE 11
(b) Explain two possible effects on humans if the amount of carbon dioxide in
the atmosphere becomes too low.
(DoE Exemplar Paper Grade 11, 2007)
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must do these things in the Modified Version:
1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document,
and from those of previous versions (which should, if there were any, be listed in the History
section of the Document). You may use the same title as a previous version if the original
publisher of that version gives permission.
2. List on the Title Page, as authors, one or more persons or entities responsible for authorship
of the modifications in the Modified Version, together with at least five of the principal
authors of the Document (all of its principal authors, if it has fewer than five), unless they
release you from this requirement.
3. State on the Title page the name of the publisher of the Modified Version, as the publisher.
4. Preserve all the copyright notices of the Document.
5. Add an appropriate copyright notice for your modifications adjacent to the other copyright
notices.
6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the
Addendum below.
7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts
given in the Document’s license notice.
8. Include an unaltered copy of this License.
9. Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating
at least the title, year, new authors, and publisher of the Modified Version as given on the
Title Page. If there is no section Entitled “History” in the Document, create one stating
the title, year, authors, and publisher of the Document as given on its Title Page, then
add an item describing the Modified Version as stated in the previous sentence.
469
APPENDIX A. GNU FREE DOCUMENTATION LICENSE
10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document
for previous versions it was based on. These may be placed in the “History” section. You
may omit a network location for a work that was published at least four years before the
Document itself, or if the original publisher of the version it refers to gives permission.
11. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the
section, and preserve in the section all the substance and tone of each of the contributor
acknowledgements and/or dedications given therein.
12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their
titles. Section numbers or the equivalent are not considered part of the section titles.
13. Delete any section Entitled “Endorsements”. Such a section may not be included in the
Modified Version.
14. Do not re-title any existing section to be Entitled “Endorsements” or to conflict in title
with any Invariant Section.
15. Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or appendices that qualify as Secondary
Sections and contain no material copied from the Document, you may at your option designate
some or all of these sections as invariant. To do this, add their titles to the list of Invariant
Sections in the Modified Version’s license notice. These titles must be distinct from any other
section titles.
You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements
of your Modified Version by various parties–for example, statements of peer review or that the
text has been approved by an organisation as the authoritative definition of a standard.
You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25
words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only
one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through
arrangements made by) any one entity. If the Document already includes a cover text for the
same cover, previously added by you or by arrangement made by the same entity you are acting
on behalf of, you may not add another; but you may replace the old one, on explicit permission
from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this License give permission to use
their names for publicity for or to assert or imply endorsement of any Modified Version.
COMBINING DOCUMENTS
You may combine the Document with other documents released under this License, under the
terms defined in section A above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them
all as Invariant Sections of your combined work in its license notice, and that you preserve all
their Warranty Disclaimers.
The combined work need only contain one copy of this License, and multiple identical Invariant
Sections may be replaced with a single copy. If there are multiple Invariant Sections with the
same name but different contents, make the title of each such section unique by adding at the
end of it, in parentheses, the name of the original author or publisher of that section if known,
or else a unique number. Make the same adjustment to the section titles in the list of Invariant
Sections in the license notice of the combined work.
In the combination, you must combine any sections Entitled “History” in the various original
documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled
“Endorsements”.
470
APPENDIX A. GNU FREE DOCUMENTATION LICENSE
COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other documents released under
this License, and replace the individual copies of this License in the various documents with a
single copy that is included in the collection, provided that you follow the rules of this License
for verbatim copying of each of the documents in all other respects.
You may extract a single document from such a collection, and distribute it individually under
this License, provided you insert a copy of this License into the extracted document, and follow
this License in all other respects regarding verbatim copying of that document.
AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other separate and independent documents
or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the
copyright resulting from the compilation is not used to limit the legal rights of the compilation’s
users beyond what the individual works permit. When the Document is included an aggregate,
this License does not apply to the other works in the aggregate which are not themselves derivative
works of the Document.
If the Cover Text requirement of section A is applicable to these copies of the Document, then if
the Document is less than one half of the entire aggregate, the Document’s Cover Texts may be
placed on covers that bracket the Document within the aggregate, or the electronic equivalent
of covers if the Document is in electronic form. Otherwise they must appear on printed covers
that bracket the whole aggregate.
TRANSLATION
Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section A. Replacing Invariant Sections with translations requires
special permission from their copyright holders, but you may include translations of some or
all Invariant Sections in addition to the original versions of these Invariant Sections. You may
include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and
the original versions of those notices and disclaimers. In case of a disagreement between the
translation and the original version of this License or a notice or disclaimer, the original version
will prevail.
If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the
requirement (section A) to Preserve its Title (section A) will typically require changing the actual
title.
TERMINATION
You may not copy, modify, sub-license, or distribute the Document except as expressly provided
for under this License. Any other attempt to copy, modify, sub-license or distribute the Document
is void, and will automatically terminate your rights under this License. However, parties who
have received copies, or rights, from you under this License will not have their licenses terminated
so long as such parties remain in full compliance.
FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions of the GNU Free Documentation
License from time to time. Such new versions will be similar in spirit to the present version, but
may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.
471
APPENDIX A. GNU FREE DOCUMENTATION LICENSE
Each version of the License is given a distinguishing version number. If the Document specifies
that a particular numbered version of this License “or any later version” applies to it, you have the
option of following the terms and conditions either of that specified version or of any later version
that has been published (not as a draft) by the Free Software Foundation. If the Document does
not specify a version number of this License, you may choose any version ever published (not as
a draft) by the Free Software Foundation.
ADDENDUM: How to use this License for your documents
To use this License in a document you have written, include a copy of the License in the document
and put the following copyright and license notices just after the title page:
c YEAR YOUR NAME. Permission is granted to copy, distribute and/or
Copyright modify this document under the terms of the GNU Free Documentation License,
Version 1.2 or any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the
license is included in the section entitled “GNU Free Documentation License”.
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with...Texts.”
line with this:
with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST,
and with the Back-Cover Texts being LIST.
If you have Invariant Sections without Cover Texts, or some other combination of the three,
merge those two alternatives to suit the situation.
If your document contains nontrivial examples of program code, we recommend releasing these
examples in parallel under your choice of free software license, such as the GNU General Public
License, to permit their use in free software.
472
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