Living Things and Air
7.1 What Is Air Made Up of?
7.3 How Does Man Obtain Energy?
7.4 How Does Green Plants Obtain Energy?
7.5 Gaseous Exchange in Animals and Plants
7.6 Balance of Carbon Dioxide and Oxygen in Nature
7.7 Effects of Smoking and Polluted Air on Our Respiratory System
Making Use of Electricity
8.1 Closed Circuit
8.2 Electrical Conductors and Insulators
8.3 Electric Current
8.6 Circuit Symbols
8.7 Series and Parallel Circuits
8.9 Household Electricity
8.10 Power of an Electrical Appliance
8.11 Cost of electricity
8.12 The Magnetic Effect of an Electric Current
8.13 Working Principles of Common Electrical Appliances