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Learning objectives: Students will be able to know about air and its components.

Air

Air is all around us. We cannot see it but we can feel it. For example, rustling of leaves, cool
breeze, wet clothes moving when hanged to dry. All these prove that air is all around us. We
use air for a lot of things including breathing. Without air, living things would be unable to
survive, including plants, animals, and human beings. The earth is covered by a layer of air
called atmosphere. Above atmosphere is a vast empty space. There is no air in the space.

Components of Air

Air contains many gases, water vapour and dust.

Gases: Air is a mixture of many gases. It primarily contains nitrogen, carbon dioxide, oxygen
and small quantities of other gases. The major part of air contains nitrogen (i.e. 78%) and
oxygen (i.e. 21%) and various other gases like carbon dioxide and argon (i.e. less than 1%).

Water vapour: Air also contains water vapour. We must have seen a layer of water droplets
on the outer surface of a glass filled with cold drinks. This is because of the water vapour
present in the air. Water vapour on cooling changes into tiny water droplets.

Dust: Air contains a lot of dust particles and germs too. If you touch an object at home or at
school which has not been wiped for a few days, you will notice a layer of dust. Where did
the dust come from? This dust is in air.

Learning outcome: Students learned about air and its components.