What is Air?

Air is everywhere around you. Evey crack, hole and space that is not already filled with something else is filled with something else is filled with air. Every time you breathe, your lungs are filled with air. Event though you cannot see air, nor, taste it, nor fell it (unless the wind is blowing), air is "something".

It is a substance or material which scientists call "mater". Matter may be a solid, a liquid, or a gas. The matter called "air" is almost always gas. In fact, air is made up of certain gases. Two of these, nitrogen and oxygen, make up 99 per cent of the air. They are always found in the same proportion of about 78 per cent nitrogen and about 21 per cent oxygen.

There is also a small amount of carbon dioxide in the air which is added to it by livings things. Thee remaining part of 1 per cent is made up of what are called rare gases: argon, neon, helium, krypton, and xenon. The great ocean of air extends for many miles above the surface of the earth. Because air is something, gravity attracts, or holds it, to the earth. Thus air has weight the weight of the air exerts pressure.

The air presses on your whole body from all directions, just as water would if you were at the bottom of the sea. If you climb high mountain or go up in an aeroplane, there is less air above you, so the pressure is less as you go up. About eight miles up, the pressure is only one-eighth of that at sea level. At 62 miles, there is almost no pressure. 

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