Page 127 - Science Class 6 Times Publication

like soyabean, bean, gram, etc can absorb nitrogen directly by their
roots from air.

The protein prepared by the plants is used by animals too. Protein
is one of the main foods of plants and animals. Nitrogen is used by
human beings to prepare various types of chemicals like ammonia,

chemical fertilizers, etc. Nitrogen gas is used inside lament lamp.
Main Points to Remember

1. Air is the mixture of various gases.
2. Air contains mainly nitrogen (78.1%), oxygen (20.98%),
carbon dioxide (0.03%) and inert gases (0.95%).

3. Nitrogen is used by plants for the preparation of food.
4. Oxygen is used by living things for breathing. It is used for

burning rewood, petrol, diesel, etc.
5. Carbon dioxide is used by green plants for the preparation
of food during photosynthesis.

Exercise

1. Choose the best alternative in each case:

a. Which is the most abundant gas present in air?

i. Oxygen ii. Carbon dioxide

iii. Nitrogen iv. Argon

b. What is the percentage of carbon dioxide in the atmosphere?

i. 78% ii. 21% iii. 0.95% iv. 0.03%

c. The process of slow oxidation of iron due to the action of water
vapour and oxygen is called
i. Reaction ii. Burning

iii. Rusting iv. Humidity

Times' Crucial Science and Environment 123 Book 6