Unit 13 Food and TransportSubstances in food 2
Food tests 3
Functions of food 8
Balanced diet 13
Storing food 19
More about food chains and food webs 25
Teeth 27
Tooth decay 32
Digestion 36
Absorption of food 41
Digestive juices 43
A closer look at the digestive system 44
More about enzymes 45
Transport system in mammals 48
Pulse and pulse rate 56
Blood pressure 58
Water balance 58
The kidneys and their functions 61
Nutrients for plant growth 64
Absorption and transport of water in plants 68
Xylem and phloem 72
The main uses of water in plants 72
Summary 73
Difficult words 79
Unit 14 Materials from the EarthThe Earth 82
The soil 91
Building materials 96
Metals from the Earth's crust 101
The pollution problem 107
Coal 111
Crude oil or petroleum 117
Materials from the sea 124
Water pollution 129
More materials from the sea 131
Chalk,limestone and marble 135
Summary 137
Difficult words 142
Unit 15 Electricity and ElectronicsElectrostatics 144
The Van de Graaff generator 146
Looking at atoms-a revision 150
Pushing charges 152
Voltage and the voltmeter 154
Safety with the mains voltage 158
Dynamo effect 159
Alternating current and direct current 166
Transmitting electrical energy 166
Transformers 171
Power transmission 173
Using electricity 174
Power and energy 176
Current in gas 179
Lightning 180
Fluorescent lamps 185
Current in a vacuum 185
Diode 187
C.R.O.and TV 197
Some useful electronic components 197
Switches 205
Electronic logic 212
Applications of the AND gate 219
Summary 222
Difficult words 227
Index 228