Lakhmir Singh Manjit Kaur Class 8 Science 18th Chapter Pollution Of Air And Water

Lakhmir Singh and Manjit Kaur Science solution: Pollution Of Air And Water Chapter 18. Here you get easy solutions of Lakhmir Singh and Manjit Kaur Science solution Chapter 18 . Here we give Chapter 18 all solution of Class 8. Its help you to complete your homework.

Board – CBSE

Text Book – SCIENCE

Class – 8

Chapter – 18


1) Carbon dioxide

2) Sulpher Dioxide, Nitrogen.

3) Carbon monoxide, nitrogen, Sulpher,

4) carbon monoxide.

5) Carbon dioxide, carbon monoxide etc.

6) Ozone gas.

7) Cholera, Diarrhea.

8) Mercury, Lead, Arsenic etc.

9) Fertilizers, Pesticides.

10) Nitrogen and phosphorus.


11) Ganga action plan is an ambitious plan to cleanse the highly polluted river ganga and reduce the pollution level in the water of river ganga.

It was launched in 1985

12) Four pollutant are Untreated sewage from homes, pesticides, Fertilizers, Industrial wastages.

Three ways to controlling water pollution are pointout below :

  • Sewage should be treated properly at sewage treatment plants.
  • Farmers should use correct amounts of fertilizers and pesticides.
  • Garbage should not be thrown into open drains.

13) Industry create a lot of dangerous wastage and these wastages are dropped direct into the rivers. Thus Industries cause water pollution.

14) The ways to reduce air pollution are pointout below :

  • The air pollution can be controlled by using smokeless fuels.
  • The air pollution from motor vehicles can be reduced by using CNG.
  • Can be controlled by using non-polluting sources of energy.

15) The difference between Pure Air and Polluted air:- The mixture of gases containing Nitrogen, Oxygen, Carbon-di-oxide, Argon and water vapour gives us pure air which is good for us. In addition to the normal constituents the polluted air may also contain harmful substances such as Carbon monoxide, Sulphur-di-oxide, Nitrogen Oxide, Smoke and dust.

16) The warming up of the earth’s atmosphere due to the trapping of sun’s heat rays by carbon dioxide gas in the atmosphere is called greenhouse effect.

Importance of Greenhouse Effect:- The warming of the earth produced by greenhouse effect importance for us because it is due to the warming of earth by greenhouse effect that the earth has become a habitable planet having millions different life farms on it. If there were no warming up of the earth atmosphere due to greenhouse effect produce by carbon-di-oxide gas in the atmosphere the whole earth would have been covered into an extremely cold planet.

17) Two greenhouse gases are carbon dioxide and carbon monoxide.

Carbon dioxide produces the maximum greenhouse effect.

18) CFC depletes the ozone layer in the atmosphere.

The destruction of Ozone layer by CFC’s will allow the extremely harmful Ultraviolet radiation of the sun to reach the earth. This ultraviolet radiation can cause skin cancer, cataract and destruction of plants.

19) a> Burning of fossil fuel.  B> From Industry…. C> From vehicles .. d> From refrigerator.

20) Even clear, transparent and odourless water may not always be safe for drinking because it may still contain harmful micro organisms.

21) Hot water from the power plants and industries is released into the rivers. It raises the temperature of the water bodies, adversely effecting the animals and plants living in it. Hence, it is considered as a pollutant.

22) The farmers used large number of chemical fertilizers like Nitrates and Phosphates in the fields to increase the yield of crops. The excess fertilizers dissolved in water and run into water, river and ponds and pollute the water. This pollute water kill the aquatic organism like fish.

23) The farmers used toxic chemicals called pesticides on standing crops in the fields to protect them from pests and diseases. Some of the pesticides dissolved in rain water and run into rivers, lakes and ponds and pollute their water.

24) The Taj Mahal at Agra is a beautiful historical monument made of pure, white marbel. The experts have warned that air pollution around Taj Mahal is discolouring its white marbel and also corroding it slowly. The passes a threat to the beauty of Taj Mahal.

The two ways to controlling air pollution are following:

  • The air pollution can be controlled by smokeless fuel.
  • Using CNG gas.

25) (a) The water which is safe for drinking is called portable water.

Two methods to make water safe are : Boiling and Filter the water.


26) (a) The contamination of water , rivers, lakes and ponds with unwanted and harmful substances is called water pollution.

The different ways of water pollution are :

  • Untreated sewage from homes.
  • Fertilizers used in agriculture.
  • Pesticides used in agriculture.

(b) The harmful effect of water pollution are pointout below:

  • Drinking of water polluted with untreated sewage can cause disease such as cholera, typhoid etc.
  • Water of rivers and lakes polluted with pesticides can kill aquatic animals.
  • Water of rivers and lakes polluted with toxic industrial wastes kills the aquatic animals like fish, damages our nervous system and causes disease such as blood poisoning and cancer.

27) (a) Air is a mixture of gas. There are two types of air in the atmosphere i.e. Pure air and Polluted air.

The various constituents are Oxygen, Nitrogen, carbon dioxide etc.

(b) The contamination of air with harmful gases , smoke and dust is called air pollution.

The main sources of air pollution are – Carbon dioxide, carbon monoxide, sulphur dioxide etc.

28) Smog is a deadly air pollutant which is formed by the combination of smoke and smog.

Formation of Smog:

The atmospheric pollutants or gases that form smog are released in the air when fuels are burnt. When sunlight and its heat react with these gases and fine particles in the atmosphere, smog is formed.

The harmful effect of smog are Cough and aggravates asthma and other lung diseases.

29) Acid rain is that rain which contains small amounts of acids formed from acidic gases like sulphur dioxide and nitrogen oxides present in polluted air.

Formation of Acid Rain:

Acid rain is formed when rain water contains very dilute solution of Sulphuric Acid and Nitric Acid.

Harmful Effects Of Acid Rain

The harmful effects of Acid rain are – Destroys forests,

kill aquatic animals Corrodes the statues, buildings etc.

30) The undue rise in the temperature of earth atmosphere due to excessive Greenhouse effect produced by increasing amounts of carbon dioxide gas in the atmosphere is called global warming.

The Harmful effect of Global Warming:

The harmful effect of global warming are as follows:-

i) Global warming can cause sea level to rise dramatically. This happens as follows:-
The rise in temperature of atmosphere due to excessive greenhouse effect or global warming will melt the enamours amount of Ice lying on the poles of the earth. The huge amount of water produced by the melting of polar ice will raise the level of water in seas and ocean and flood the low live area of the earth.

(ii) Global warming can reduce rainfall in some areas of the earth leading to droughts.

Higher Order Thinking Skills (HOTS)


P = Fertilizer

Q = Algae

R = Bacteria

S = Oxygen

The farmers use a large amount of Fertilizer (P) in the field to increase the crop yield. The Excess of Fertilizer dissolves in water and runs into a lake. The Fertilizers causes rapid growth of algae (Q) in the lake which covers the whole lake like a green sheet. When the algae die the bacteria (R) decompose them by utilizing the oxygen (S) dissolved in lake water.  The amount of dissolved oxygen in water decreases too much due to which the fish living in the lake suffocate and die.


At many places the wastewater containing human excreta from homes and carried in big underground pipes is dumped into a river which pollutes the riverwater. The waste water is called sewage. It contains many harmful organisms like bacteria, protozoa, fungi, virus and parasites. These organisms can cause serious harm to the overall ecosystem. If someone drinks water contaminated by sewage water may fall seriously ill. Some common diseases occurred from drinking contaminated water are cholera, Typhoid, diarrhea, dysentery and jaundice.


The burning of fossil fuel like coal and oil in factories, thermal power plants and oil refineries and petrol and diesel in motor vehicle produce acidic gases like sulphur dioxide and nitrogen oxides which go into air and pollute it. The sulphur dioxide reacts with the water vapor in air and forms sulphuric acid .The nitric acid is formed by the reaction between nitrogen oxide and water vapor. This sulphuric acid and nitric acid dissolves in the rain water and fall to the earth in form of acid raid. Due to acid rain the water in ponds lake and river become more acidic and due to this the fish get killed.

Some farmers use excess amount of fertilizers for better yield. The excess fertilizers flow to the nearest water bodies and causes excess growth of algae. When these algae die the bacteria present in the water decomposes the dead bodies of the algae using oxygen dissolved in the water. This causes shortage of oxygen in the water body and living organisms like fish suffocates to death.


X = Carbon monoxide

Y = Hemoglobin

Z = Oxygen

The incomplete combustion of firewood in homes produces a very poisonous gas called Carbon monoxide (X). When inhaled, carbon monoxide gas combines with the hemoglobin (Y) present in blood and reduces the capacity of blood to carry oxygen (Z) causing respiratory problems and suffocation.

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Add a Comment
  1. Nice and short questins

  2. Some mistakes in of chap-18

    1. Thank Very Short Answer

  3. Wrong ans.of

  4. Questions no. 28 is write it’s not smoke it’s is correct it is smog

    1. You just do your work ok

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