Page 101 - ICSE Chemistry 6

is a mixture of gases. He also showed that the main cons tuents of
air nitrogen and oxygen make up only one-fourth of the total air by
oxygen
volume.
21%
Air is made up of nearly 78 per cent nitrogen, 21 per cent oxygen, others
1%
0.03–0.04 per cent carbon dioxide and the remaining are the other nitrogen
gases which are present in trace amount. Air also contains suspended 78%
dust par cles and smoke. The composi on of water vapour, dust
par cles and smoke varies from place to place.
Fig. 5.1: Composition of air
Table 5.1: Cons tuents of Air and their Uses

Constituents of air Percentage by volume Properties and uses

Nitrogen 78% It is a gas inert in nature which doesn’t support burning. It is
an important component of proteins in living things.
Oxygen 21% It is a chemically reactive gas, which supports burning. It is
essential for respiration.

Carbon dioxide 0.03–0.04% It is a chemically reactive gas, which doesn’t support
burning. It is essential for photosynthesis in plants.

Noble gases such as neon, 0.93% These gases are non-reactive. They are useful in our lives.
helium, oxygen and krypton

Water vapour Variable It is responsible for weather changes such as rain.
Suspended dust particles Variable These lead to problems like respiratory issues, skin diseases
and smoke and cancer.

Properties of Air

• Air occupies space.

• Air has mass.
• Air can be compressed.

• Air exerts equal pressure in all direc ons.
• Air is a mixture of gases.

Activity 5.1

Aim: To show that air is present everywhere
Materials required: Tub fi lled with water, a glass tumbler

Procedure
• Take an empty glass tumbler and turn it upside down in a big tub fi lled with water.

Observa on: You will observe that the water level is lower as compared to the water outside.
This happens because the air is trapped within the glass tumbler which does not allow the water level in
the tumbler to rise.

87