Answer
Air contains some gases mainly nitrogen, oxygen, small amount of carbon dioxide, water vapour and dust particles.
2. Which gas in the atmosphere is essential for respiration?
Answer
Oxygen gas in the atmosphere is essential for respiration.
3. How will you prove that air supports burning?
Answer
Step I: Two shallow containers are taken and burning candles are fitted into it.
Step II: Now, water is filled in the container at two different levels.
Step III: Both the candles are then covered with glass.
Step IV: After sometimes, we observed that the candles having less water in its container lights off.
This happened because the container having more water contains more oxygen and therefore it burnt for more time. Thus, it is proved that air supports burning.
4. How will you show that air is dissolved in water?
Answer
Step I: Water in a pan is taken.
Step II: It is now boiled on stove.
Step III: We will observe tiny bubbles of water visible coming out from the bottom of the pan.
These tiny bubbles are coming due to the air dissolved in water. Thus, this proves that air is dissolved in water.
5. Why does a lump of cotton wool shrink in water?
Answer
The lump of cotton contains air in it. When it comes in contact with water, the air pushed out from the vacant space and dissolved in water and thus a lump of cotton wool shrink in water.
6. The layer of air around the earth is known as ___________.
Answer
The layer of air around the earth is known as atmosphere.
7. The component of air used by green plants to make their food, is ___________.
Answer
The component of air used by green plants to make their food, is carbon dioxide.
8. List five activities that are possible due to the presence of air.
Answer
Five activities that are possible due to the presence of air:
(i) Helps in seed dispersal and pollination.
(ii) Sailing of ships.
(iii) Flying of the birds and kites.
(iv) Gives us oxygen to respire.
(v) Helps in the rotation of windmill.
9. How do plants and animals help each other in the exchange of gases in the atmosphere?
Answer
Plants take in carbon dioxide in during photosynthesis give out oxygen in the atmosphere while animals take in oxygen and breathe out carbon dioxide during respiration. In this way, plants and animals help each other in the exchange of gases in the atmosphere.