1. Air is a mixture of gases containing nitrogen (78%), oxygen (21%), and water vapour, dust particles and other gases (1 %).
2. Air occupies space. It also has weight.
3. Air exerts pressure in all directions.
4. Air can be compressed.
5. One-fifth of the air is oxygen. Oxygen is necessary for combustion and respiration.
6. Photosynthesis in plants is possible because of carbon dioxide in the air.
7. Nitrogen present in the air is necessary for the growth of plants.
8. The ozone layer protects us from the harmful ultraviolet rays of the sun.
9. Burning of fuels and factory wastes are the main causes of air pollution. Cutting down of trees has also led to an increase in air pollution.
10. Planting trees, taking measures to reduce smoke and pollutants in factories, and using catalytic converters and unleaded petrol in automobiles, are some ways of reducing air pollution