Page 73 - Active Science 5 Ebook and Activity

C omponents of Air

Air is a mixture of various gases. These gases are useful for both plants and animals.
Oxygen, nitrogen and carbon dioxide are the main gases present in the air. The percentage
of these gases is – oxygen 21%, nitrogen 78%, and carbon dioxide and other gases 1%.

Per cent means ‘out of every one hundred’.

Oxygen

It is the most important gas for all living beings. Both plants and animals use atmospheric
oxygen in the process of respiration. We breathe in air rich in oxygen and give out air rich

in carbon dioxide. The oxygen from the air breathed in is absorbed by the blood in lungs.
The haemoglobin in blood carries oxygen to all the parts of body. This oxygen oxidizes the
food in the body tissues and provides us energy to do work. This process produces carbon
dioxide which is carried by blood to lungs and is thrown out in the air we breathe out.

Oxygen also supports in burning. Burning is not possible without oxygen.

Activity 6.1

People who travel to hilly areas often feel giddy or get headache. Surf the internet and find out
at least three ways to get rid of this problem. Also find out the reasons for this sickness.

Nitrogen 1 % Carbon Dioxide
and other gases
It is the most abundant gas in air. It neither
burns, nor helps in burning. Nitrogen is 21%
used in packaged food as it prevents the Oxygen
growth of micro-organisms. 78%
Nitrogen
Though both plants and animals need
nitrogen for their growth, they do not
use it directly from the air. The bacteria
present in soil provides nitrogen to plants. Composition of Air
Fertilizers are a major source of nitrogen for plants.

Humans get nitrogen from both plant and animal sources of food.

Carbon Dioxide

A very little amount of carbon dioxide is present in the atmosphere. Plants need carbon
dioxide to carry out the process of photosynthesis. On burning coal and wood, carbon
dioxide is produced. It does not help in burning, so it is used to put out fire. It is also

used in making soft drinks. It is naturally added to the atmosphere by the process of
breathing out by living beings.

73
Active Science-5