Goa Board Class 6 Solutions for Science – Air Around Us (English Medium)
Page No. 153:
Question 1:
What is the composition of air?
Solution:
Air is a mixture of many gases. It consists of water vapour, oxygen, nitrogen, carbon dioxide, helium etc. It also contains dust particles and smoke.
Question 2:
Which gas in the atmosphere is essential for respiration?
Solution:
Oxygen is essential for respiration.
Question 3:
How will you prove that air supports burning?
Solution:
To prove that air (oxygen) supports burning, we would be requiring the following things:
Two shallow beakers, two candles and two glasses of unequal size.
Procedure:
i. Take two shallow beakers.
ii. Fix burning candles in each and label them as A and B.
iii. Fill both the beakers with a small amount of water.
iv. Cover Candle A with small glass and candle B with long glass.
Observation:
Candle A will blow out first in comparison to candle B because the content of air in small glass was less in comparison to long glass. Also water level will rise in both the glasses.
Conclusion:
This proves that air (oxygen) is necessary for burning.
Question 4:
How will you show that air is dissolved in water?
Solution:
To show the presence of air in water, take some water in a pan and boil. Well before the boiling of water, if we look carefully at the inner surface of beaker, tiny air bubbles are visible on the inside of the beaker. These bubbles come from the air dissolved in water. This proves that water has dissolved air in it.
Question 5:
Why does a lump of cotton wool shrink in water?
Solution:
A cotton lump contains air in it. Infact, there are various spaces in the lump in which air is filled. When it is put into water, air present in these vacant spaces gets dissolved in water and the cotton lump sinks.
Page No. 154:
Question 6:
The layer of air around the earth is known as ___________.
Solution:
Atmosphere.
Question 7:
The component of air used by green plants to make their food, is ___________.
Solution:
Carbon dioxide
Question 8:
List five activities that are possible due to the presence of air.
Solution:
The five activities possible due to air are:
i.The wind makes windmill rotate which is used to produce electricity.
ii.Birds, insects and bats fly due to the presence of air.
iii.Air helps in dispersal of seeds and pollen grains of several plants.
iv.Air plays an important role in water cycle.
v.We need air (oxygen) to breathe.
Question 9:
How do plants and animals help each other in the exchange of gases in the atmosphere?
Solution:
Plants and animals help each other in exchange of gases in the following manner:
i.Plants take in carbon dioxide and give out oxygen.
ii.Animals take in oxygen and give out carbon dioxide.