CONTENTS
Preface iii
The world of chemistry:
Of molecules and materials
Objectives 1
1. 0 Why chemistry? 2
1.1 So, what is chemistry? 3
1.2 Chemistry in ancient India 6
2.0 Elements and symbols 8
2.1 Elements through the centuries 9
2.2 Elements and their symbols 10
3. 0 Mixtures and compounds 12
3.1 What is a mixture? 12
3.2 Separation of substances in a mixture 14
3.3 What is a compound? 15
4.0 Atoms and molecules 17
4.1 Dalton's observations of the atom 17
4.2 What is the atomic number of an element? 20
4.3 How do atoms exist in nature? 22
5. 0 States of matter 25
5.1 Properties of the different states of matter 2 5
5.2 Change of state 27
5.3 Types of physical changes 29
6.0 Water: the cradle of life on earth 33
6.1 Water - the unique liquid 34
6.2 Hard water 36
6.3 Decomposition of water 38
7. 0 Preparation and properties of some gases 39
7.1 Hydrogen: the most abundant element in the universe 39
7.2 Oxygen: the breath of life 42
7.3 Carbon dioxide: the source of food 46
7.4 Carbon monoxide 50
8.0 Acids, bases, salts and valence 52
8.1 What are acids? 52
8.2 Uses of acids 52
8.3 What are bases? 55
8.4 Examples of bases neutralising acids 56
8.5 How can we identify acids and bases? 57
8.6 Salts 59
8.7 Valence 60
9. 0 Carbon: the black rock that bums 62
9.1 Carbon - element with many forms 62
9.2 Diamond and graphite 63
9.3 Combustion 66
9.5 Anatomy of a flame 70
9.6 Carbon compounds 71 I
9.7 Carbon and fuel gases 72
9.8 Carbon: The backbone of polymers 76
9.9 The world of plastics and fibres 78
10.0 Man and metals 82
10.1 Where are metals found? 83
10.2 Difference between minerals and ores 83
10.3 Metallurgy: the science of extraction 84
10.4 Physical properties of metals 85
11.0 Man-made materials 89
11.1 Cement - the versatile building material 89
11.2 Glass through the ages 91
11.3 Ceramics or the potter's clay
11.4 Soap, the familiar cleansing agent
11.5 Chemical fertilizers
12.0Air Around Us 101
Objectives 101
12.1 What is air? 102
What is air made up of? 102
Finding the missing ingredient 103
The other missing ingredient 106
Composition of air: then and now 108
12.2 Properties of air 110
Air occupies space 110
Air exerts pressure 111
How does the air get heated? 113
12.3Air and life on earth 115
Nitrogen 115
The restless air 117
Pressure and wind 118
Air: the moving force around us 120
13.2 Nature's gift: The water cycle 141
Scientific understanding of the water cycle 141
Role of evaporation in the water cycle 142
Condensation: transition from gas to liquid 144
Back to earth: precipitation 146
13.3 Properties of water 148
Physical properties of water 148
Chemical properties of water 150
13.4 Salinity of water 153
Why is sea water salty? 153
13.5 Water pollution 156
Water pollution - what are the reasons? 156
Crude oil spills and pollution of the oceans 158
It is time that we stop polluting
our water sources 160
13.6 Purification of water 161
From water source to taps 162
Uses of water 163
Running water and energy 164
Conservation of water 166