NCERT Exemplar Solution Class 8 Science Chapter 18

NCERT Exemplar Solution Class 8 Science Chapter 18

NCERT Exemplar Solution Class 8 Science Chapter 18 Pollution of Air and Water all Questions Answer Solution. NCERT Exemplar Class 8 Science Chapter 18 Solution PDF.

NCERT Exemplar Solution Class 8 Science Chapter 18: Overview

NCERT Exemplar Solution Class 8 Science Chapter 18

Board

NCERT

Topic

Exemplar Problem Solution
Class

                 8                   

Subject

Science
Chapter

18

Chapter Name

Pollution of Air and Water

NCERT Exemplar Solution Class 8 Science Chapter 18 Pollution of Air and Water   

Multiple Choice Questions

1) Air is a mixture of various gases. One of the gases is 21% part of the air and is essential for the survival of human beings. This gas is

a) Nitrogen

b) Oxygen

c) Ozone

d) Argon

Answer:- b) Oxygen

Oxygen is present 21% in the air. While the nitrogen is present 78% and other gases are only1%. Oxygen is very essential for human beings to breathe.

2) Which of the following is not a source of air Pollution?

a) Automobile exhaust

b) Burning of firewood

c) Windmill

d) Power plant

Answer:- c) Windmill

Windmill is used for formation of electricity by using the flowingwind. Therefore it is not a polluting source.

3) Boojho wishes to contribute in reducing air pollution. Which vehicle should he use for going to school?

a) Car

b) School bus

c) Auto rickshaw

d) Scooter

Answer:- b) School bus

Using common sources for the Transportation will be decrease in the air Pollution. School bus can be used by near about 50 students at a time. If they all use separate vehicle then air Pollution will be increased.

4) Which of the following is not a way to conserve water ?

a) Replace

b) Reduce

c) Reuse

d) Recycle

Answer:- a) Replace

We can conserve or save the water by reducing use, reusing it again, and Recycling the waste water. But replacing is the way of conservation of water.

5) The type of pollution which is likely to affect Taj Mahal in Agra to a greater extent is

a) Air Pollution

b) Water Pollution

c) Soil Pollution

d) Noise Pollution

Answer:- a) Air PollutionA

Air pollution increase the dangerous gases such as sulphur dioxide and nitrogen dioxide in the atmosphere which is responsible for the acid rain which is affecting the Taj Mahal in Agra to a greater extent.

6) Incomplete combustion of fuel such as petrol and diesel gives

a) Nitrogen oxide

b) Sulphur dioxide

c) Carbon monoxide

d) Carbon dioxide

Answer:- c) Carbon monoxide

A dangerous air pollutants Carbon monoxide gas is released due to the incomplete combustion of  fuels. Which is if inhaled by persons in major quantity can cause death.

7) The phenomenon of marble cancer is due to

a) Soot particles

b) Fig

c) CFCs

d) Acid rain

Answer:- d) Acid rain.

The phenomenon of marble cancer is due acid rain. Acid rain is the main reason for the corrosion of monuments made up of marbles. It is the raining of acid containing nitric acid and sulphuric acid.

8) Potable water is the water which is

a) Obtained from a river

b) Obtained from a lake.

c) Pure and fit for drinking

d)Used only for washing clothes.

Answer:- c) Pure and fit for drinking.

A useful drinking water is known as potable water. Potable water should be pure and fur for drinking.

9) Which of the following procedures will give you water free from all impurities?

a) Adding chlorine tablets

b) Distillation

c) Boiling

d) Filtration

Answer:- b) Distillation

Distillation is the process which water is obtained from the vapours. First the water is boiled and these vapours are stored as the distil water which does not have any type of impurities in it. While the other methods also remove some impurities but not all impurities.

10) A pond contains clean water. Which of the following activities will produce least pollution of water?

a) Washing clothes in the pond

b) Animals bathing in the pond

c) Washing motor vehicles in the pond

d) Swimming in the pond

Answer:- d) Swimming in the pond.

Swimming will produce least water Pollution. Rather washing clothes which are dirty, washing motor vehicles and bathing of animals in it.

11) Trees help in reducing the Pollution of our environment. Lakhs of trees are planted by people in the month of July every year. The occasion is called

a) Forest conservation day

b) Plantation month

c) Van mahotsav

d) Wildlife week

Answer:- c) Van mahotsav

Planting of trees in the month of jully has given the name of van mahotsav.

12) Which of the following is not a green house gas ?

a) Nitrogen gas

b) Water vapour

c) Methane gas

d) Carbon dioxide

Answer:- a) Nitrogen gas

Nitrogen is not an green house gas. It is present 79% in the atmosphere. While the other water vapour, Methane gas, carbon dioxide and CFCs are green house gases which increases the temperature of the earth.

13) Name the chemicals which are used in refrigerators and air conditioners and damage ozone layer when released in air.

Answer:- chlorofluorocarbons are mainly Used in the refrigerator, aerosol sprays and air conditioners which is being responsible for the increasing the Global warming and finally damaging the ozone layer.

14) Name any two sources which cause air Pollution due to suspended particulate matter.

Answer:- The sources which are responsible for the air Pollution are –

1) Automobiles – Automobiles / vehicles which use petrol and diesel as fuel , produce small particles and leave them suspended in the air causing air Pollution.

2) Industries – Industrial activities such as steel production company and mining produces tiny particles responsible for air Pollution.

3) Power plants- Power plants also produces small particles and increase the Pollution.

15) Name two gases which are mainly responsible for acid rain?

Answer:-  The gases which are mainly responsible for the acid rain are nitrogen dioxide and sulphur dioxide. These two gases reacts with the water vapour in the atmosphere and forms nitric acid and sulphuric acid.

16) The quality of air at various locations is monitored regularly by government and other agencies? In what way can you use these data ?

Answer:- AQI or  Air quality index is the measuring of quality of air or Air pollution. These is measured from place to place at various different locations regularly. These AQI data shows that how polluted air is today. And due to these we can be aware about the increasing air Pollution. These is very helpful for increasing awareness among the people.

17) Combustion of fossil fuels generates a lot of air Pollution. Can you suggest any two alternative sources of energy which do not cause any pollution?

Answer:- Combustion of fossil fuels include the burning of wood, coal, petrol, diesel etc. Burning of these materials releases lots of air pollutants into the air. These also spreads smoke and fog. Which includes the dangerous gases such as Carbon monoxide, sulphur dioxide, Nitrogen dioxide. Etc. These gases can causes severe respiratory disorders or permanent lungs damage. Besides using these sources for the energy we can use solar energy and wind energy for various works.

18) Name any two water pollutants which are toxic for plants and animals.

Answer:- The water pollutants which are toxic for plants and animals are lead, fluorides and arsenic. These are mainly thrown out with water from the industries. These causes the chemical contamination of water.

Short Answer Questions

19) A lot of dry leaves are collected in a school garden and are burnt every day. Do you think that it is right to do so ? If not, what should be done to dispose off the dry leaves?

Answer:- No. It is not the right way to burn the dry leaves. These burning of dry leaves releases lots of gases and fumes into the atmosphere, which causes the air Pollution. Dry leaves of the trees can be converted into Manure or compost. These dry leaves should be disposed in the pit to form the Compost.

20) The level of air Pollution is higher at a busy traffic intersection. Why?

Answer:- At the traffic signals large number of vehicles stops for sometimes. Many of them do not switch off the vehicle they keep it in on position throughout the red signal. Therefore the burning of petrol or diesel continue over there. Release of high amount of gases increases the air pollution of that place in higher quantity.

21) Fill in the blanks with the help of words given in bracket after each sentence.

a) When air is contaminated by _____ substances which have a _______ Effect in both the _______ & _________. It is referred to as __________.

( Air Pollution, harmful, living, unwanted, non-living, pollutants)

Answer:- when air is contaminated by unwanted substances which have a harmful effect in both the living and non-living . It is referred to as Air Pollution.

b) Many _______ are responsible for causing _________ pollution. Petroleum _________ are a major source of ____________ pollutants like ________ and _________.

( Sulphur dioxide, refineries, industries, nitrogen dioxide, gaseous, liquid, people, air)

Answer:- Many industries are responsible for causing air Pollution. Petroleum refineries are a major source of gaseous pollutants like sulphur dioxide and nitrogen dioxide.

c) While _________ your teeth, leaving the ________ running may waste several _________ of water.

( Tap, litres, brushing, washing, drops)

Answer:- while brushing your teeth, leaving the tap running may waste several litres of water.

d) Water which is suitable for ________ is called ________ water.

(Washing, bathing, drinking, potable, soft).

Answer:- water which is suitable for drinking is called potable water.

e) Water which looks clean still has disease carrying __________ and _____________ impurities.

( Insects, microorganism, particles, dissolved, harmful)

Answer:- water which looks clean still has disease carrying microorganisms and dissolved impurities.

22) Match the items of Column A with those Column B.

Column A Column B

a)          Sulphur dioxide

i)                          Damage ozone layer
b)         Carbon dioxide

ii)                      Reduces oxygen – carrying capacity of blood

c)           Carbon monoxide

iii)                 Acid rain.

 

d)         Chlorofluorocarbons

iv)                  Green house gas.

 

 

Answer:-

A) Sulphur dioxide→ iii) Acid rain

B) Carbon dioxide → iv) Green house gas

C) carbon monoxide → ii) reduce oxygen Carrying capacity of Blood .

D) chlorofluorocarbons →i) Damage ozone Layer

23) Find out the wrong statements and write them in their correct form.

a) We can survive for some time without air but we cannot survive even for a few minutes without food.

Answer:- false

We cannot survive without air for some minutes but we can survive without food.

b) A brick kiln emits lot of smoke and other harmful gases causing air Pollution.

Answer:- true

c) Carbon monoxide is produced by complete burning of fuels such as coal, petrol, deiseal.

Answer:- false

The incomplete burning of fuels such as coal, petrol, diesel produces the carbon monoxide gas.

d) Chlorination is a commonly used chemical method for killing germs in water.

Answer:- true

e) Water which is suitable for drinking is called soft water.

Answer:- false

Potable water is known as the water which is suitable for drinking.

24) In the following statements, the underlined words are jumbled up. Write them in their correct form.

a) Air contains 78% ginrotenand 21% gonexy.

Answer:-  Air contains 78% nitrogen and 21% oxygen.

b) Vehicles produce high level of pollutants like carbon dioxide, nitrogen oxides, nobracmoondexi and mosek.

Answer:-  Vehicles produce high level of pollutants like carbon dioxide, nitrogen oxides, Carbon monoxide and smoke.

c) Carbon dioxide, thaneme, nitrous oxide and water vapour are known as heengrousesesga.

Answer:-  Carbon dioxide, Methane, nitrous oxide and water vapour are known as greenhouse gases.

d) Gangotriglacier in Himalaya has started melting because of lablogringwarm.

Answer:- Gangotriglacier in Himalaya has started melting because of global warming.

e) Whenever harmful substances such as wagese, toxic chemicals, slit, etc. Get mixed with water, the water becomes potdulle.

Answer:-  whenever harmful substances such as sewage, toxic chemicals, slit etc. Get mixed with water, the water becomes polluted.

Long Answer Questions

25) What do CFCs stand for ? Name some devices where CFCs are used. Why CFCs are considered as pollutants ?

Answer:- CFCs stands for Chlorofluorocarbons . CFCs are used in the refrigerators , air pollutants, and aerosol sprays. CFCs are considered as pollutants because it damage the ozone layer of the atmosphere. Ozone layer is the Protective layer of atmosphere which protects the earth from thedangerous ultraviolet rays of the sun. Ozone layer traps the ultraviolet rays. These CFCs gases goes to the ozone layer and damage the layer. It is responsible for the ozone hole.

26) Why is it advised that Industries should switch over to cleaner fuels such as CNG and LPG in the Taj Mahal Zone in Agra ?

Answer:-

Agra’s Taj Mahal is one of the famous tourist place in India. But now a days it’s white marble is discoloured. There is industrial area located near Agra. Which throw-out the dangerous gases  in the atmosphere which contains sulphur dioxide and nitrogen dioxide in it. These two gases reacts with he water vapour and forms sulphuric acid and nitric acid. Which comes down on earth with the water droplets. These rain of acids is known as acid rain. These acid rain helps in the corrosion of marble of Taj Mahal. These is known as, “ Marble Cancer”. These causes the yellowish colours over the white marble. Therefore  it is advised to the industries andvehicles near Agra to use cleaner fuels such as CNG and LPG so that there will not be any Pollution of air and emitting of any  dangerous gases which causes harm to Taj Mahal and environment. These cleaner fuels burn effectively and do not left over any pollutants.

27) It is said, “ CO2 contributes to global warming.” Explain.

Answer:- Carbon dioxide along with the other gases such as methane, water vapours and Chlorofluorocarbons causes global warming. Carbon dioxide traps the heat which is responsible for the increasing the temperature of the earth. Carbon dioxide gas is some what important in maintaining the temperature of the earth’s surface and of atmosphere, As earth’s temperature is naturally very low but carbon dioxide traps the heat of sun-light and does not allow it to pass in further. Thus earth’s temperature Becomes suitable for leaving. But now a days due to Pollution the amount of carbon dioxide is increased in the atmosphere which is also increasing the amount trapping the heat. As these trapped heat is  does not escaped in the outer space  these  increased the heat of earth’s temperature  causes the global warming.

28) We should plant trees and nurture the once already present in the neighbourhood. Why?

Answer:- Tree plantation is important For environment. Planting trees reduces the air Pollution. Trees takes in the carbon dioxide and use it to make its food and gives out the oxygen gas which is very much important for living being. Thus trees also helps in reducing the global warming by taking in the carbon dioxide from the atmosphere. Planting trees and nurturing the present trees is important for the nature cycle also. Trees protect the soil and  the surface earth from the heat and thus helps in reducing the temperature of the earth.

29) Explain the traditional way of purifying water to make it fit for drinking.

Answer:- The traditional ways to make the water fit for drinking or potable are as follows-

1) Boiling:- Boiling the water at higher temperature kills the germs and microorganisms present in the water. Thus the water becomes potable. These is the easy method which is used in the homes for drinking water.

2) Chlorination:- Using Chlorine powder or Chlorine tablets to disinfect water is also a method. It is a chemical method to purify water. We can also add bleaching powder in the water to disinfect it.

3) Filtration:- Filtering the water is also a method which is used in homes. Filtering the water removes the impurities and clean the water. But these does not kills the germs and microorganisms. Household water filters are candle type of water filters.

30) How can we reduce, reuse and recycle water ?

Answer:- We can Reduce, Reuse, and Recycle the water as follows:-

Reduce of water :-

We can reduce the water uses by maintaining disciplinesand stopping wastage of water. Some works we can do by using less water. Bathing, washing clothes and utensils can be done by using less amount of water. Closing the open tabs will also reduce the wastage of water.

Reuse of water :-

Reusing the water is also the saving of water. the water used for washing vegetables can be re-used for household works, washing vehicles, washing clothes and utensils, or can give it to plants. Outlet of water purifier waste lots of water, that can be easily reused for the other household works.

Recycling of water :-

Recycling of water is very much important. We can recycle sewage water in sewage treatment plant. Industrial waste water should be recycled first before leaving in the rivers. We can also use recycled water for some works.

31) Read the paragraph and answer the questions following it.

Ans: Water is essential for life. Without water there would be no life. We usually take water as granted for its purity, but we must ensure the quality of water. Pollution of water originates from human activities. Through different paths, pollution reaches to ground water. Easily identified source or place of pollution is called as point source, e.g. – municipal and industrial discharge pipes, where pollutants enter the water source. Non- point sources of pollution are those where a source of pollution can not be easily identified, e.g.- agricultural run off, acid rain etc.

i) how do you classify the various sources of water Pollution?

Answer:-  the sources of water Pollution is classified as point sources And  non point sources.

ii) what are the point sources of water Pollution ?

Answer:-point sources are those water pollution sources or places whichcan be easily identified.

iii) name any two non- point sources of water Pollution?

Answer:- some Non- point sources are acid rain and agricultural chemicals.

32) Complete the crossword puzzle with the help of clues given below:

Fig. 18.1

Across-

1) Pollutant which was used in refrigerators and air conditioners. (18)

3) produced on incomplete combustion of fuels . (14)

6) this chemical protects our crop and is washed into water bodies from the field. (9)

Down-

2) this layer protects us from harmful ultraviolet rays. (5)

4) it is essential for combustion. (6)

5) Disease which is caused by drinking contaminated water (7) .

7) River which is famous in India and sustains most of the northern, central and eastern Indian Population. (5)

Answer:-

Updated: April 28, 2021 — 1:30 pm

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