3rd Class Science Weather, Air and Water Air

   Air

Every empty space is filled with a mixture of gases, called air. Gasses present in air are nitrogen, carbon dioxide, oxygen, helium, argon and many more.

         Importance of Air

Air is essential for existence of life. Without air life cannot survive. We breathe in oxygen, without which we can't live even for a minute. Not only humans, all kinds of life, that is, cats, dogs, microorganisms, birds, snakes, lizards, frogs or even plants need oxygen to survive.

Look at the following picture of burning of wood which require oxygen:

Everything burns only in the presence of oxygen. Air becomes thinner and thinner, as we go up higher and higher. Therefore, astronauts and mountaineers carry oxygen cylinder with them. Air also consists of water vapor, smoke and the unburned particles.

When anything burns gases are produced, which is called smoke. Smoke is lighter, hence it rises up high in the sky. Along with smoke some unburned particles also rises up, called soot. Presence of soot in smoke gives it the black colour. Air contains 78% nitrogen, 21% of oxygen and 1% is contributed by other gases, including carbon dioxide.

Due to the gravity of the earth, gas particles remain in the atmosphere of the earth and do not escape into the space.    

     If we keep all the components of air in increasing order according to their percentage, which one of the following is correct?

(a) Carbon dioxide. Nitrogen, oxygen

(b) Nitrogen, Oxygen, Carbon dioxide

(c) Carbon dioxide, oxygen, nitrogen

(d) Oxygen, carbon dioxide, nitrogen

(e) None of these

Answer: (c)

Explanation

Nitrogen contributes 78%, oxygen contributes 21%, and carbon dioxide contributes 0.03%. Therefore, option C is correct and rest of the options is incorrect.

      The thick blanket of air, which surround the earth, is called

(a) Atmosphere

(b) Biosphere

(c) Hydrosphere

(d) All of these

(e) None of these

Answer: (a)

Explanation

The thick blanket of air which surrounds the earth is called atmosphere. Therefore, option (a) is correct and rest of the options is incorrect..