Basic Science Solutions for Class 8 Science Chapter 16 Pollution Of Air And Water are provided here with simple step-by-step explanations. These solutions for Pollution Of Air And Water are extremely popular among Class 8 students for Science Pollution Of Air And Water Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Basic Science Book of Class 8 Science Chapter 16 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Basic Science Solutions. All Basic Science Solutions for class Class 8 Science are prepared by experts and are 100% accurate.

Page No 177:

Question A.1:

Answer:

Polluted air or water contains substance that are harmful for human beings and environment as well.

Page No 177:

Question A.2:

Polluted air or water contains substance that are harmful for human beings and environment as well.

Answer:

Following three observations indicate that a given sample of water is polluted.

(i) It has a bad taste.
(ii) It has a bad smell.
(iii) Usually, oil floats on it.

Page No 177:

Question A.3:

Following three observations indicate that a given sample of water is polluted.

(i) It has a bad taste.
(ii) It has a bad smell.
(iii) Usually, oil floats on it.

Answer:

Chemical pollution of water means pollution of a water body caused by addition of harmful chemical substances into it.



Page No 178:

Question A.4:

Chemical pollution of water means pollution of a water body caused by addition of harmful chemical substances into it.

Answer:

Main chemical pollutants of water are:

(i) Pesticides and fertilisers
(ii) Mineral acids
(iii) Grease and oil
(iv) Synthetic chemicals
(v) Phosphates from detergents
(vi) Metals and their compounds

Page No 178:

Question A.5:

Main chemical pollutants of water are:

(i) Pesticides and fertilisers
(ii) Mineral acids
(iii) Grease and oil
(iv) Synthetic chemicals
(v) Phosphates from detergents
(vi) Metals and their compounds

Answer:

Four water-borne diseases are:

(i) Typhoid
(ii) Dysentery
(iii) Cholera
(iv) Hepatitis

Page No 178:

Question A.6:

Four water-borne diseases are:

(i) Typhoid
(ii) Dysentery
(iii) Cholera
(iv) Hepatitis

Answer:

Potable water refers to the water that is fit for drinking.

Page No 178:

Question A.7:

Potable water refers to the water that is fit for drinking.

Answer:

Activated charcoal is made by heating ordinary charcoal in vacuum. It is used in filtration of water to remove the impurities.

Page No 178:

Question A.8:

Activated charcoal is made by heating ordinary charcoal in vacuum. It is used in filtration of water to remove the impurities.

Answer:

Bleaching powder is used in the purification of water, as it reacts with water and releases chlorine. Chlorine kills the germs present in water.

Page No 178:

Question B.1:

Bleaching powder is used in the purification of water, as it reacts with water and releases chlorine. Chlorine kills the germs present in water.

Answer:

Carbon monoxide is a poisonous gas and is very harmful for human beings. It combines with the haemoglobin of the blood and replaces oxygen. This causes the formation of carboxyhaemoglobin in place of oxyhaemoglobin. It stops the oxygen supply to the cells and can cause death.

Page No 178:

Question B.2:

Carbon monoxide is a poisonous gas and is very harmful for human beings. It combines with the haemoglobin of the blood and replaces oxygen. This causes the formation of carboxyhaemoglobin in place of oxyhaemoglobin. It stops the oxygen supply to the cells and can cause death.

Answer:

The main advantage of using CNG over petrol or diesel in automobiles is that it helps in reducing pollution. It contains methane, which releases lesser pollutants than coal, petrol, diesel etc.

Page No 178:

Question B.3:

The main advantage of using CNG over petrol or diesel in automobiles is that it helps in reducing pollution. It contains methane, which releases lesser pollutants than coal, petrol, diesel etc.

Answer:

Three methods of preventing water pollution:

(i) Sewage should be treated in sewage-treatment plants to allow only clean water to be discharged into river or lake.
(ii) Industrial waste should be treated to remove harmful chemicals.
(iii) Pesticides and fertilisers should be used in a limited amount.

Page No 178:

Question C.1:

Three methods of preventing water pollution:

(i) Sewage should be treated in sewage-treatment plants to allow only clean water to be discharged into river or lake.
(ii) Industrial waste should be treated to remove harmful chemicals.
(iii) Pesticides and fertilisers should be used in a limited amount.

Answer:

Three pollutants of air are as follows:

(i) Carbon monoxide:
The main source of carbon monoxide is the incomplete combustion of fuel in vehicles and coal in thermal power plants.

(ii) Chlorofluorocarbons (CFCs):
CFCs are released in air by leaking refrigerators and air conditioners. Spray cans also add to the CFCs in air.

(iii) Oxides of nitrogen:
Main source of these pollutants are the combustion of fuels like petrol, diesel, kerosene and coal.

Page No 178:

Question C.2:

Three pollutants of air are as follows:

(i) Carbon monoxide:
The main source of carbon monoxide is the incomplete combustion of fuel in vehicles and coal in thermal power plants.

(ii) Chlorofluorocarbons (CFCs):
CFCs are released in air by leaking refrigerators and air conditioners. Spray cans also add to the CFCs in air.

(iii) Oxides of nitrogen:
Main source of these pollutants are the combustion of fuels like petrol, diesel, kerosene and coal.

Answer:

Eutrophication: Extreme depletion of dissolved oxygen in a water body due to the overgrowth of aquatic weeds, causing damage to aquatic life, is called eutrophication. It occurs when fertilisers are discharged into water bodies with the run-off from agricultural land. These fertilisers promote the fast growth of aquatic weeds. As a result, the weeds utilise more dissolved oxygen from the water body and make it oxygen deficient. This harms the life of other aquatic animals, as they do not get enough oxygen and ultimately die.

Page No 178:

Question C.3:

Eutrophication: Extreme depletion of dissolved oxygen in a water body due to the overgrowth of aquatic weeds, causing damage to aquatic life, is called eutrophication. It occurs when fertilisers are discharged into water bodies with the run-off from agricultural land. These fertilisers promote the fast growth of aquatic weeds. As a result, the weeds utilise more dissolved oxygen from the water body and make it oxygen deficient. This harms the life of other aquatic animals, as they do not get enough oxygen and ultimately die.

Answer:

Alum helps in purification of muddy water by settling down the suspended particles present in it. This can be shown by the following activity:
Take two beakers having equal volumes of muddy water and mark them as A and B. Now, crush few crystals of alum and add it to beaker A. Stir the water in both the beakers and let them stay. After some time, we find that the mud in beaker A has settled down and there is clear water in it. On the other hand, water in beaker B is still muddy.

Page No 178:

Question D:

Alum helps in purification of muddy water by settling down the suspended particles present in it. This can be shown by the following activity:
Take two beakers having equal volumes of muddy water and mark them as A and B. Now, crush few crystals of alum and add it to beaker A. Stir the water in both the beakers and let them stay. After some time, we find that the mud in beaker A has settled down and there is clear water in it. On the other hand, water in beaker B is still muddy.

Answer:

1. Carbon dioxide is formed by the complete combustion of carbon.
2. Acid rain contains mainly sulphuric and nitric acids.
3. An increase in the CO2 level in the air causes the greenhouse effect.
4. Sculptures, monuments and buildings are eroded by acid rain.
5. Ozonisation of water kills the microorganisms in it and makes it rich in dissolved oxygen.

Page No 178:

Question E.1:

1. Carbon dioxide is formed by the complete combustion of carbon.
2. Acid rain contains mainly sulphuric and nitric acids.
3. An increase in the CO2 level in the air causes the greenhouse effect.
4. Sculptures, monuments and buildings are eroded by acid rain.
5. Ozonisation of water kills the microorganisms in it and makes it rich in dissolved oxygen.

Answer:

(b) CFCs

CFCs are the main cause of ozone depletion; they convert ozone into oxygen.

Page No 178:

Question E.2:

(b) CFCs

CFCs are the main cause of ozone depletion; they convert ozone into oxygen.

Answer:

(a) the sun's ultraviolet rays

The ozone layer of atmosphere protects earth from the ultraviolet rays of the sun.

Page No 178:

Question E.3:

(a) the sun's ultraviolet rays

The ozone layer of atmosphere protects earth from the ultraviolet rays of the sun.

Answer:

(d) Domestic sewage

Domestic sewage is an oxygen-demanding waste.

Page No 178:

Question E.4:

(d) Domestic sewage

Domestic sewage is an oxygen-demanding waste.

Answer:

(d) all of these

All the given options, i.e., chlorine, ozone and ultraviolet rays, are used for disinfecting water.

Page No 178:

Question E.5:

(d) all of these

All the given options, i.e., chlorine, ozone and ultraviolet rays, are used for disinfecting water.

Answer:

(b) water

Reverse osmosis is used for the purification of water.

Page No 178:

Question F:

(b) water

Reverse osmosis is used for the purification of water.

Answer:

A B
(a) Oil spills (iii) reduces the transmission of light through water
(b) Ceramic candles (iv) water filter
(c) Alum (i) helps the sedimentation of suspended particles in water
(d) Bleaching powder (v) disinfects water
(e) Typhoid (ii) a water-borne disease



View NCERT Solutions for all chapters of Class 8