NCERT PRACTICE QUESTIONS
1. What is the composition of air?
Ans. - Air consist of water vapor, Oxygen, Nitrogen, Carbon dioxide, dust and smoke.
2. Which gas in the atmosphere is essential for respiration?
Ans. - Oxygen in the atmosphere is essential for respiration in humans while plants utilize carbon dioxide.
3. How will you prove that air supports burning?
Ans. - Cover the burning candle with glass cup, when air is blocked the candle goes off.
4. How will you show that air is dissolved in water?
Ans. - Heat the pan filled with water. Before they start boiling bubbles occur, these bubbles are due to air present in water. This experiment concludes air is present in the water.
5. Why does a lump of cotton wool shrink in water?
Ans. -The lump of cotton wool shrink in water because the air inside the cotton lumps are replaced by water which makes the layer stick together.
6. The layer of air around the earth is known as ___________.
Ans. - Atmosphere.
7. The component of air used by green plants to make their food, is ___________.
Ans. - Carbon dioxide.
8. List five activities that are possible due to the presence of air.
Ans. - 1.Photosynthesis 2.Cloud formation 3.Respiration 4.Transpiration 5.Winnowing
9. How do plants and animals help each other in the exchange of gases in the atmosphere?
Ans. - Plants in-take carbon dioxide to give out oxygen. This oxygen is used by animals for respiration, animals expel out carbon dioxide. This carbon dioxide is used by plants to prepare food.
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