Page 210 - Science Class 08

v Water can be filtered by using filters. It is a purifying water. It is a chemical method for
physical method for removing impuri es. purifying water. It is done by adding
In many households candle type filters are chlorine tablets or bleaching powder to the
very popular. water. But, you should remember that the

v If there are germs present in water, you quan ty of chlorine tablets must not be
should boil it for about 20 minutes to kill more than the specified quan ty.
the germs. v Nowadays, UV (Ultraviolet) filters are

v Clorinisa on is an important method of a ached to the tap. The ultraviolet rays kill
the germs present in water

1. Write any two causes of water pollu on.
2. How agricultural discharge causes water pollu on?
3. What is Minomata disease?
4. What is Ganga Ac on Plan?
5. How can we purify water for drinking?

Pollution : An undesirable change in the physical, chemical or biological
characteristics of air, water or land
Pollutants : The agents or substances that cause pollution
SPM : Tiny solid particles suspended in air are known as Suspended
Particulate Matter (SPM)

Pesticides : Chemicals used to kill pests and germs
Acid rain : Rain drops that contain harmful chemicals
Green House Effect : The increase in average temperature because of trapping of heat by
some gases called green house gases

Ozone hole : Damage in ozone layer of the atmospheres
Electric Precipitator : A device used to separate SPM from gas
Effluent : Untreated liquid wastes released by industries

Eutrophication : Excessive growth of algae in water bodies due to excessive
accumulation of nutrients in them

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i Air pollution is the presence of foreign substances in the atmosphere that may harm living
organisms directly or indirectly.
i Water is polluted by natural as well as man-made sources.

210 Science-8