Air

Air is essential for our existence. Air is an extremely important natural resources. The organisms which live on land can get oxygen necessary for respiration only from air. A man respires about 22,000 times in a day and takes about 16 kilograms of air into his body during this process. Green plants take carbon dioxide for photosynthesis process. Air contains water vapour also.

Composition of air
Air is a mixture of gases. Air contains about 78% nitrogen, 21% oxygen and a very small amount of several gases like carbon dioxide, inert gases and other gases.
The various components of air according to volume are:

                         

In air, water vapour and impurities are present in small quantities. Besides, nitrogen, oxygen, carbon dioxide, water vapour, there are other gases like Helium, Neon, Argon, Krypton, Xenon etc. present in small quantities in the air. These gases are very inactive and hardly react with other chemicals.

        

 The composition of air is generally the same in the atmosphere near the surface of the earth. However, the percentage of water vapour varies from place to place. It is seen from the above table that nitrogen is more in atmosphere than any other gases. Through nitrogen is the most abundant of all the gases, plants and animals cannot takes directly. Plants and animals take nitrogen in the form of nitrates to make protein. Nitrogen is not reactive gas. Oxygen present in the atmosphere is used by plants and animals for respiration and for the ignition of fire. Carbon dioxide is used by plants to prepare carbohydrates during photosynthesis process