Air around us
Air:- Air occupies space. It is present everywhere around us. Air has no colour and it is transparent.
Wind:- Air in motion is called wind.
Atmosphere:- Our earth is surrounded by a thin layer of air. This layer extends up to many kilometres above the surface of the earth and is called the Atmosphere. As we move higher in the atmosphere, the air gets rarer.
Air is a mixture of many gases:-
- Water vapour:- when air comes in contact with a cool surface, it condenses and drops of water appear on the cooled surfaces. The presence of water vapour in air is important for the water cycle in nature.
- Oxygen
- Nitrogen:- The major part of air is Nitrogen.
- Carbon dioxide:- Carbon dioxide makes up a small component of the air around us. Plants and animals consume oxygen for respiration and produce carbon dioxide.
- Dust and Smoke:- The burning of fuel also produces smoke. Smoke contains a few gases and fine dust particles and is often harmful.
Note:- Plants also consume oxygen for respiration, but they produce more of it than they consume. That is why we say plants produce oxygen.
Role of Air:-
- Air helps in the movements of sailing yachts, gliders, parachutes and aeroplanes. Birds, bats and insects can fly due to the presence of air.
- Air also helps in the dispersal of seeds and pollen of flowers of several plants.
- Air plays an important role in the water cycle.
- Plants and animals depend on each other for exchange of oxygen and carbon dioxide from air.
- Aquatic animals use dissolved air in water for respiration.
Windmill:- The wind makes the windmill rotate. The windmill is used to draw water from tube wells and to run flour mills. Windmills are also used to generate electricity.