8. Pollution class8 general science question answer maharshtra board

Class 8 Pollution exercise question answer 8th general science

8th class science all question answer Class 8 general science chapter 7 question answer Class 8 question answer pollution Pollution class 8 question answer maharshtra board

Q.1.Following are some statements about pollution. Which type of pollution do those express?

a. Fog seems to be appearing in Delhi during day hours.

Ans: Air pollution-Smog

 

b. Many times, vomiting and dysentery occurs after eating ‘pani puri’.

Ans: Water pollution-Contaminated food and water due to bacteria or virus.

 

c. Problem of sneezing occurs sometimes during visit to garden.

Ans: air pollution due to pollens

 

d. Crop does not grow up in some areas.

Ans: Soil pollution

 

e. People living in the busy squares face the problems like short breathing and other respiratory problems.

Ans: Air pollution due to traffic.

 

2. Read the passage and identify the sentences expressing types of pollution. Nilesh is a student of std. VIII and lives in urban area. It takes about an hour to go to the school by bus. He faces the heavy traffic of two wheelers, four wheelers, rickshaws, buses while going to school. He is facing the problem of asthma since last few days. Doctors recommended him to stay away from urban area. Since then, his mother sent him to the village of his maternal uncle. Nilesh saw the heaps of garbage at many places in village. Foul smell of human and animal wastes was present at many places. Blackish water with foul smell was flowing in a stream. He developed some abdominal disease within few days.

Ans:

1) It takes about an hour to go to the school. (Due to traffic jam, Nilesh is spending more time in polluted, contaminated air.)

2) He is facing the problem of asthama (Air pollution-Harmful to human health)

3) He faces the heavy traffic. ( large scale combustion of fossil fuel)

4) The heaps of garbage at many places (solid waste-land pollution.)

5) Foul smell of human and animal wastes. (Biological pollution, air pollution)

6) Blackish water with foul smell was flowing in a stream. (Improper sewage management-water pollution.)

7)He developed some abdominal disease within few days. (Water pollution-Effect on human health.)

 

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Q.3.Match the pairs from ‘A’ and ‘B’ columns and explain the effect of pollution on human health.

Column ‘A’	Column ‘B’
1. Water containing cobalt	a. Mental retardedness
2. Methane gas	b. Paralysis.
3. Water containing	c. Inflammation lead of lungs.
4. Sulphur dioxide	d. Skin cancer
5. Nitrogen dioxide	e. Irritation of eyes

Ans:

1. Water containing cobalt- Paralysis.

2. Methane gas – Skin cancer

3. Water containing – Mental retardation

4. Sulphur dioxide – Irritation of eyes

5. Nitrogen dioxide – Inflammation of lungs

 

Q.4. True or false 

a. Water does not get polluted by washing the cloths in running water of river.

Ans: False.

 

b. More the use of electric appliances, more will be the pollution

Ans: True

 

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Q.5. Answer the following.

a. What is pollution?

Ans:

            Contamination of natural environment that can harmfully affect the environment is called pollution.

 

b. What are pollutants?

Ans:

                The products which affect the normal functioning of ecosystem and have an adverse effect on plants, animals and humans are called pollutants.

 

c. What is acid rain?

Ans:

            (1) When rainwater contains harmful amounts of nitric and sulphuric acids , it is called acid rain .

            (2) Burning of fossil fuels such as coal, wood, petroleum, etc. releases nitrogen oxide and sulphur oxide into the atmospheric air.

            (3) Since these oxides are soluble in water, they dissolve in rainwater. Nitrogen and sulphur oxides dissolved in large quantities of water vapour form acids like nitric acid, nitrous acid, sulphurous acid and sulphuric acid.

            (4) These acids mix with mist, drops of rainwater and snow. They change their composition and fall back on the ground in the form of acid rain.

 

d. What is green house effect?

Ans:

        1.Greenhouse effect is the phenomenon due to which global warming and climate change occur.

        2.The earth receives solar energy in the form of heat from the sun. The surface of earth absorbs this heat and reflect it back to the atmosphere as infrared radiation. Some of this heat energy goes into space.

        3.But due to pollution there is an envelope of CO2, CH4 and water vapours in the atmosphere, some of these radiations are absorbed by these gases. This radiation is sent back to the earth surface in the form of heat energy.

        4.This causes warming of the earth which is called greenhouse effect. It later results in global warming.

        5.More and more burning of fossil fuels and allied activities by humans cause more and more greenhouse effect.

 

e. Which are visible pollutants known to  you?

Ans:

            The polluting substances that are seen easily with the naked eyes can be called as visible pollutants.

E.g. solid wastes, plastic articles, plastic bags, the suspended things in the water, metal refuse, etc.     

 

f. Which are invisible pollutants?

Ans:

                    The pollutants which are completely dissolved in water or mixed in the air, cannot be seen and hence they can be called invisible pollutants, since they are not seen, we remain unaware about the presence of these pollutants. E.g. the insecticides spread on the crops. Aerosols, many hazardous gases in the air, toxic compounds that are totally soluble in water, etc.

 

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Q.6. Answer the following

a. Give two examples of each of water, soil and air pollution from your residential area.

Ans:

I ) Air pollution :

(1) New buildings are constructed . Old structures are demolished. This is creating lots of dust pollution. The air is full of particulate matter.

(2) The number of vehicles on the road has tremendously increased this cause smoky environment.

 

(II) Water pollution:

(1) The sea shows lots of floating plastic and decaying flowers , etc. When beaches are visited is a common sight.

(2) Many fishes are seen dying in great numbers and are washed off to the shore .

 

(III) Soil pollution:

(1) Everywhere garbage heaps are seen . In that plastic bags , needles , old medicine vials and cartons are seen in abundance .

 

b. How does the pollution occur due to vehicles? Give the names of vehicles causing least pollution.

Ans:

(1) More than 50 % of the air pollution is caused by vehicular traffic.

(2) Particulate matter, unburnt hydrocarbons, CO , nitrogen oxides and carcinogenic hydrocarbons are present in the automobile exhausts .

(3) Fossil fuels like petrol, diesel, natural gas, gasoline , etc. which are burnt to run the automobiles lead to the emission of CO₂ and other gases.

(4) Therefore , vehicles are said to be the major contributors to air pollution .

(5) The only vehicle which is non-polluting is bicycle. The four – wheelers which are battery operated are also manufactured recently. These two types of vehicles are eco – friendly. The cars that run on C.N.G. are also said to be lesser polluting.

 

c. What are natural reasons for water pollution?

Ans:

( 1 ) If organic pollutants are added to the water there is overgrowth of weeds such as Eichhornia . The growth of algae also makes the water unsuitable for consumption . These aquatic plants release oxygen during day time but by night they require oxygen thus depleting the dissolved oxygen level . The natural characters of water are then changed .

( 2 ) The decomposing matter when added to the water make it polluted and stinking .

( 3 ) Due to deposition of sludge or eroded soil , the rivers change their path and divert from original flow . The currents are also changed . Deposition of sludge makes the water polluted .

( 4 ) Due to soil erosion , surrounding the water bodies , the microbes , bacteria , protozoans and the worms and larvae of nematodes enter the water causing severe biological pollution . Many inorganic pollutants are also added to the water . The fungi and bacteria present in the water make it non – potable . Such water spreads the water borne diseases .

d. Suggest four preventive measures for air pollution.

Ans:

The following methods are adopted to control air pollution from the industries :

(1) The source discharge is diluted by tall chimneys .

(2) There are source correction methods like changing the raw material , equipment modification , process modification , etc.

(3) Effective pollution equipment like dust collectors , electrostatic controlling precipitators , wet scrubbers , etc. should be used .

(4) There should be ban and control over atomic tests and chemical weapons on the international level .

 

e. Explain relation between green house effect and global warming.

Ans:

The following methods are adopted to control air pollution from the industries :

(1) The source discharge is diluted by tall chimneys .

(2) There are source correction methods like changing the raw material , equipment modification , process modification , etc.

(3) Effective pollution equipment like dust collectors , electrostatic controlling precipitators , wet scrubbers , etc. should be used .

(4) There should be ban and control over atomic tests and chemical weapons on the international level .

 

f. Construct two slogans each on air, water and soil pollution.

Ans:

Air pollution :

( 1 ) Be a part of the solution and not part of pollution .

( 2 ) Show your care , clean your air .

 

Water pollution :

( 1 ) Water , water everywhere , Not a drop to drink . The pollution is making all the water stink .

( 2 ) Save the fish and the little turtle . Don’t throw plastic or it will encircle.

 

Soil Pollution :

( 1 ) Don’t be mean , keep environment clean .

( 2 ) Let’s keep land clean , together only we can win .

 

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Q.7. Classify the following pollutants into natural and manmade categories.Sewage, dust, pollen grains, chemical fertilizers, vehicular smoke, algae, pesticides, waste of animals and birds.

 Ans:

Man-made	Natural
Sewage	Dust (natural)
Dust (Construction related)	Pollen grains
Chemical Fertilizers	Algae
Vehicular smoke	Waste (excreta) of animals and birds
Pesticides

 

         

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