Class-8 Science Chapter-18 Pollution of Air and Water

EVENTS CONVENT H. SCHOOL

23/02/2021          Class-8                 SLOT-2
SCIENCE
Chapter-18
POLLUTION OF AIR AND WATER
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A. Short Answer Type Questions

 Question 1.What are the different sources responsible for the depletion of atmospheric oxygen?

Answer:The sources are:

Burning of fuel which consume oxygen gas.

Excessive use of various pesticides like DDT.

 

Question 2.What was the aim of the Ganga Action Plan?

Answer:Its aim was to reduce the pollution level in the Ganga river.

 

Question 3.How would the disposal of garbage, etc., affect the living organisms in the river?

Answer:Disposal of garbage into the rivers pollute the river water. When garbage rots, it produces poisonous and toxic gases so that living organisms cannot breathe and die ultimately.

 

Question 4.What will happen if we drink polluted water?

Answer:If we drink polluted water, we may suffer from the water borne diseases such as jaundice, dysentery, hepatitis, cholera, etc.

 

Question 5.How can water be made fit for drinking?

Answer:Drinking water can be boiled before drinking. It kills the harmful bacteria present in it.

It can also be. purified by adding potassium permanganate (Lai Dawai) or bleaching powder.

In cities alum and chlorine gas is added to purify water.

 

B. Long Answer Type Questions

 

Question 6.What is atmosphere?

Answer:The atmosphere is the protective blanket of gases surrounding the earth. It is a mixture of gases. The composition is very important for the survival of living things on the earth. The atmosphere contains N2, O2, CO2, noble gases, water vapour and dust particles. The composition of atmosphere depends upon place, season and altitude, etc.

 

Question 7.What are the major pollutants of air? Name these.

Answer:The major air pollutants are:

Carbon monoxide (CO)

Carbon dioxide (CO2)

Suspended Particulate Matter (SPM)

Chlorofluorocarbons (CFCs)

 

Question 8.What is global warming? How is it caused?

Answer:Increasing temperature of the earth is called global warming. The radiation of the sun, reaching the earth is not being consumed. This is due to the deforestation. The level of CO2 has increased and thus global warming has also increased. CO2 is absorbed by the plants for photosynthesis. So reduced number of plants increases the amount of carbon dioxide in the environment. This cuases accumulation of carbondioxide and increases temperature.

Question 9.What are the different ways in which water gets contaminated?

Answer:Different ways of water contamination:

Discharge or dumping of domestic wastes and sewage into water bodies.

Surface runoff by water after rains.

Faulty drainage system.

Discharge from chemical factories directly into the river.

Discharge from laboratories and hospitals into the river.

Disposal of dead bodies of animals and human beings into the rivers.

 

Question 10.At an individual level, how can you help to reduce air pollution?

Answer:Air pollution can be reduced by

planting more and more trees.

using smokeless stoves and LPG.

using smokeless fuel like CNG in vehicles.

avoiding the use of fossil fuels like coal and petroleum.

saying ‘No’ to plastic bags.

avoiding smoking.

not burning dry leaves etc., but putting them in compost pits to make manure.

 

Question 11.Explain the differences between pure air and polluted air.

Answer:Pure air has about 78% nitrogen, 21% oxygen and 0.03% carbon dioxide. It does not contain dust particles and smoke in it.

Polluted air has pollutants like dust and carbon particles, smoke and harmful gases like sulphur dioxide, nitrogen dioxide, excess carbon dioxide and carbon monoxide in it.

 

Question 12. How does acid rain affect us?

Answer:Harmful effects of Acid Rain:Acid rain results in the corrosion of the marble of the buildings, monuments and statues made of marble, slate or limestone.

It increases the corrosion of metals.

It is harmful to aquatic life.

It damages the leaves of plants and trees.

It affects adversely the vegetation and reduces reproduction.