Current Affairs 3rd Class

Category : 3rd Class

Air and Water

1. Air and water are necessary for our living. Without them all plants and animals would die.

2. Our earth is surrounded by a layer of air called atmosphere. Atmosphere contains oxygen. Oxygen helps to burn the food in our body and give energy.

3. As we go higher from the earth, air decreases. On the mountains, the air is thinner.

4. We all need water. We use water for drinking, bathing, cooking, washing our clothes, etc. Plants and animals too need water. Without water all the living things would die.

5. The water we see is in liquid form. It can be poured into a vessel. Water takes the shape of the vessel it is in. It has no fixed shape.

6. We cannot see or feel the water in the air because it is in the form of gas. This gas is called water vapour. When water is kept in a refrigerator it changes into ice. Ice is the solid form of water.

7. Water can be found in three forms-solid ice, liquid form of water and gaseous form of water vapour.

8. Seas, ocean, rivers, ponds and lakes are big resources of water. Polar ice caps and mountain peaks contain ice.

9. When we heat a solid it becomes liquid. Ice which is a solid when heated becomes water which is a liquid. This process of heating ice to change it into water is called melting.

10. When a liquid is heated it it becomes a gas. When liquid water is heated in a kettle we can observe steam coming out of it. Steam is nothing but water vapour. Heating water to change it into water vapour is called boiling or evaporation.

11. When a gas is cooled it becomes liquid. When we cool the water vapour it becomes liquid water. This process of changing water vapour into water by cooling is called condensation.

12. When liquid water is further cooled, it becomes ice. This process is called freezing. The refrigerator in our home freezes water into ice.
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14. Rain gauge is an instrument used to measure how much rain has fallen. It is a tall round metal. Can Inside this can a large collecting funnel which empties rain water into a narrow centimeters of rain has fallen.