NCERT Solutions for Class 6 Science Chapter 15 - Air Around Us

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.

Oxygen is essential for respiration.

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.

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.

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.

Atmosphere.

Carbon dioxide

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.

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.