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1.Question. What is the composition of air?
Answer. Air comprises of water vapor, Oxygen, Nitrogen, Carbon dioxide, dust and smoke.

2.Question. which gas in the atmosphere is essential for respiration ?
Answer. Oxygen.

3.Question. How will you prove that air support burning?
Answer. Two lighted candles are taken. one candle is covered a fixed in a tumbler containing water. This candle is covered by an inverted glass. After sometime, the covered candle gets extinguished and water rises upto 1/5th is oxygen. The candle extinguished as soon as all the oxygen was used up in burning. Therefore, water occupies that space. This shows that air supports burning.

4.Question. How will you so that air is dissolved in water?
Answer.When a tumbler containing water heated, tiny bubles appear on the inner side. These bubles appear before the water starts boiling. So, these must be air bubles. This experiment  shows that water contains air.

5.Question. Why does a lump of cotton wool shrink in water?
Answer.A lump of cotton wool shrink in water because the air inside wool cotton is driven out by water. They layer stic together and hence the lump shrinks.

6.Question. The layer of  air around the earth is known as:-
Answer. Atmosphere.

7.Question. The comppnent of used by green plants to make their food, is :
Answer. Carbon doxide.

8.question. List five activities that are possible due to the presenmce of air.


(1) Winnowing.
(2) Formation of clouds.
(3) Respiration.
(4) Photosynthesis.
(5) Transpiration.
(6) Flying of birds.

9. How do plants and animals help each other in the exchange of gases in the atmosphere?

Answer: Plants take carbon dioxide to give out oxygen. This oxygen is used by animals for respiration to expel out carbon dioxide. This carbon dioxide is used by plants to prepare food. This way, plants and animals help each other in the exchange of gases in the atmosphere




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