Page 107 - ICSE Chemistry 6

Take a Break!

Write/Choose the correct answer.
1. Air is a __________ of gases.

2. The chemist who proved that air is a mixture of gases was __________.
3. Nitrogen is needed by plants for their growth. (True/False)

4. All animals and plants need oxygen for excre on. (True/False)
5. Oxygen cons tutes about __________ of the air.
6. The level of __________ in the atmosphere also play a role in determining the global temperature.

7. Water vapour are formed due to mel ng and boiling of water. (True/False)
8. Dust par cles are only some mes present in the atmosphere. (True/False)

IMPORTANCE OF AIR

Air is important for all living organisms. It is essen al for our survival as it contains oxygen. Oxygen is
considered to be the most important component of air as it helps in two important processes: respira on
and combus on.

Respiration

All living organisms require oxygen for respira on. The oxygen which we inhale during breathing is
transported to the cells of the body. These cells then u lize the oxygen to breakdown food in order
to release energy that can be used to perform various life processes. This en re process is known as
respira on and can be defi ned as the process in which oxygen is used to release energy by breaking down
food. During respira on, carbon dioxide and water are also given out as by-products. We exhale carbon
dioxide. We can summarize respira on by the following equa on.

Food + Oxygen  Energy + Water + Carbon dioxide

Plants also respire in a similar way to release energy and give out carbon dioxide and water as by-products.
All living organisms respire throughout day and night.

Activity 5.7

Aim: To show that soil contains trapped air which is used by the organisms living in soil and by the roots
of plants to respire
Materials required: A beaker, some soil, some water

Procedure: Take some water in a beaker and add a handful of soil into the beaker.
Observa on: You will observe that small bubbles of air are formed.

Conclusion: This shows that air is present in the spaces between soil par cles. This air
present in the soil is used by the organisms such as earthworms to respire. The roots of plants also respire
using the air trapped in the soil.

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