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Air Composition

The air around us is composed of many gases. Air
includes 78% Nitrogen, 21% Oxygen and 1%
other gases.
The other gases that constitute 1% are carbon
dioxide, argon, hydrogen, helium and neon.
Besides these, air also contains water vapours
and dust particles.

Oxygen is the most important gas. All living things require oxygen to breathe. It is also
essential for combustion or burning.
Carbon dioxide is essential for the plants for photosynthesis to make their food.
Water vapours determine the condition of weather in an area. Excess of water
vapours in air is called humidity.

Aim: To study that air exerts pressure.
Materials Required: Gas jar, trough, water, covering lid of glass jar.
Method: Take a gas jar and a trough. Fill both of them with water. Cover the gas jar
carefully with lid so that no air is left inside. Invert the jar over the water in the trough
and then remove the lid. The water does not come out into the trough, the level of
water in both is different.
Result: Air exerts pressure on the surface of water in the trough and this pressure
keeps the water high in the jar.

Learn More

A helicopter is an aircraft which has revolving wings. These wings are called rotors. The
rotors rotate with fast speed to reduce the air pressure above them and the craft is lifted
upwards. Helicopters can rise and land vertically and can also hover in the air.

Air has Weight and Exerts Pressure

Air is a real substance and it has weight and exerts pressure. Air pressure on the
Earth’s surface is equal in all directions so we cannot feel pressure. The pressure
exerted by air upon the Earth is known as atmospheric pressure.

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