NCERT Solutions For Class 6 Science Chapter 15 Air Around Us

The component of air used by green plants to make their food, is carbon dioxide.

The layer of air around the earth is known as atmosphere.

A lump of cotton wool shrinks in water because when it is immersed in water, air present in it escapes and it reduces in size.

Oxygen is essential for respiration.

Air is a mixture of nitrogen, oxygen, small amount of carbon dioxide, water vapour and some other gases. Nitrogen constitutes 78% of the air. Oxygen constitutes 21% of the air. Carbon dioxide, water vapour and other gases constitute only 1% of the air.

To show that air is dissolved in water, take some water in a pan and heat it slowly. Just before the water begins to boil, look carefully at the bottom of the pan. Tiny air bubbles are seen at the bottom of the pan before the water actually boils. These air bubbles come from the air dissolved in water. When we heat the water, air dissolved in it escapes.

Activities that are possible due to the presence of air are:

1. Photosynthesis
2. Respiration
3. Flight of birds, bats and insects
4. Movement of sailing yachts, gliders, parachutes and aeroplanes
5. Generation of electricity by windmill

To prove that air supports burning, we will perform an activity.

To perform this activity, things required are candle, water, container and matchbox.

First of all take a container and fix a candle in the middle of the container. Fill the container with some water. Now, light the candle and then cover it with an inverted container.

After some time, it is observed that candle extinguishes.

Candle extinguishes because the amount of air is limited inside the inverted container. Hence, supply of oxygen is also limited.

Once oxygen is completely consumed, the candle blows off. This proves that oxygen is essential for burning.

During photosynthesis plants take carbon dioxide from atmosphere and make their own food and oxygen is produced in this process. Plants also consume oxygen during respiration but amount of oxygen released during photosynthesis is more than the amount of oxygen used during respiration. Animals inhale oxygen produced by plants and in turn, carbon dioxide is produced.

In this way, plants and animals help each other in the exchange of gases in the atmosphere.