Question 1. What is the composition of air?
Solution 1. The air is composed of oxygen, nitrogen, carbon dioxide, water vapour, dust and smoke.
Question 2. Which gas in the atmosphere is essential for respiration?
Solution 2. The gas which is essential for respiration in the atmosphere is oxygen.
Question 3. How will you prove that air supports burning?
Solution 3. Place two candles on a table both of the same length. Now light the candles and cover one of them with a glass tumbler. You will observe that after some time, the candle that was covered with the glass tumbler got vanished and the candle that was not covered continued burning. It shows that some components of air support burn which is why in the limited amount of air the covered candle extinguished because it consumed all the air while the other candle continued burning because of a sufficient amount of air. Oxygen is that component of air which supports burning.
Question 4. How will you show that air is dissolved in water?
Solution 4. Heat some water in a container. Before it begins to boil you will notice tiny bubbles inside the container. These bubbles are formed because of the air present in water. When you start heating up the water the air dissolved in it escapes. Thus, we conclude that air is present in the water.
Question 5. Why does a lump of cotton wool shrink in water?
Solution 5. There is air present inside the cotton lump which gets replaced by the water when it gets in the water and the water makes the layer of cotton stick together which makes the lump of cotton shrink in water.
Question 6. The layer of air around the earth is known as ___________.
Solution 6. The layer of air around the earth is known as the atmosphere.
Question 7. The component of air used by green plants to make their food is ___________.
Solution 7. The component of air used by green plants to make their food is carbon dioxide.
Question 8. List five activities that are possible due to the presence of air.
Solution 8. Following are the activities that are possible due to the presence of air:
- Photosynthesis
- Cloud formation
- Respiration
- Transpiration
- Winnowing
Question 9. How do plants and animals help each other in the exchange of gases in the atmosphere?
Solution: oxygen is consumed by both animals and plants from the air and carbon dioxide gas is released by them in the air during the process of respiration. During the process of photosynthesis, oxygen is also released by the plants and utilizes carbon dioxide. In this way, plants and animals help each other in the exchange of gases in the atmosphere.