Air is the invisible mixture of gases that surrounds planet Earth. Components of air form part of the life processes of all land-dwelling animals and plants: animals and plants take in oxygen during respiration and excrete carbon dioxide; and plants also use carbon dioxide during photosynthesis.
Air is also important for the physics of useful items such as aeroplanes, kites and gliders, and the flight of birds, bats and winged insects. Anything that soars above the earth relies on air to support it.
Currents in the air produce wind.
The gases that make up air, in order of prevalence, are:
- Carbon dioxide
- Water vapour
- Many other gases that are present in minute amounts, including argon and helium.
Nothing can burn in the absence of air, since oxygen plays a vital part in the chemistry of burning.
Air is required for sound to travel, and for musical instruments to make their sounds by vibrating the air that passes through them. In fact, a musical tune is sometimes referred to as an 'air', underlining air's vital importance.