NCERT Solutions for Class 8 Science Pollution of Air and Water

Ch-18 Pollution of air and water

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

Ans. Water gets contaminated due to the addition of substances harmful to health. Sewage, agricultural chemicals and industrial wastes are some of the major contaminants of water.

2. At an individual level, how can you help reduce air pollution?

Ans. At an individual level we can help in reducing air pollution by following methods:

(i) We can plant trees and nurture the ones already present in the neighborhood.

(ii) We can take part in Van Mahotsava actively and effectively every year and motivate people about the importance of plantation.

(iii) We can educate the people against burning the dried leaves and plant and advise them to put them in compost pit.

NCERT Solutions for Class 8 Science Pollution of Air and Water

3. Clear, transparent water is always fit for drinking. Comment.

Ans. No, clear and transparent water even without smell, may contain bacteria, viruses etc. which are not visible to eyes. Drinking such water can cause illness of various kinds. Therefore, we must drink purified and potable water after boiling.

NCERT Solutions for Class 8 Science Pollution of Air and Water

4. You are a member of the municipal body of your town.

Make a list of measures that would help your town to ensure the supply of clean water to all its residents.

Ans. The following steps could be taken:

(a) First of all, procurement of required amount of water for all residents should be ensured.

(b) Wastage of water by leakage at various places should be taken into account.

(c) Water treatment should be ensured.

(d) Must have sufficient water tanker to meet emergency situations.

5. Explain the differences between pure air and polluted air.

Ans. Pure air is free from any pollutant, has no smell, is soothing and not irritating to eyes. Whereas polluted air gives a filthy smell and people cannot breathe in it. If people inhale such air, they may suffer from various breathing, heart and lung problems. Even sometimes people die inhaling polluted air.

NCERT Solutions for Class 8 Science Pollution of Air and Water

6. Explain circumstances leading to acid rain. How does acid rain affect us?

Ans. Gases like sulphur dioxide and nitrogen dioxide react with water vapour present in atmosphere to form Sulphuric acid and nitric acid. These acids come down with rain water, making the rain acidic. This is known as acid rain.

Acid rain corrodes the marbles of the monuments. This phenomenon is known as Marble Cancer. It also kills the useful organism in agricultural soil.

NCERT Solutions for Class 8 Science Pollution of Air and Water

7. Which of the following is not a green gas?

(a) Carbon dioxide

(b) Sulphur dioxide

(c) Methane

(d) Nitrogen

Ans. (b) Sulphur dioxide.

8. Describe the ‘Green House Effect’ in your own words.

Ans. The Sun’s rays when fall on the earth’s surface, warm i. some of the Sun’s rays are trapped by the atmosphere and these and not allowed to go out of the earth’s atmosphere. These trapped heat cause warming of atmosphere called greenhouse effect. The gases like methane and carbon dioxide form a thick layer and prevent the escaping of heat to cause this effect. Due to greenhouse effect the global warming is happening.

NCERT Solutions for Class 8 Science Pollution of Air and Water

9. Prepare a brief speech on global warming. You have to deliver the speech in your class.

Ans. Today, global warming has appeared as one of the most sever threat to the human beings. One hand, carbon dioxide is added in the atmosphere due to human activities. On the other hand, the forest area are decreasing day by day. It leads to an increase in the amount of carbon dioxide in atmosphere. The accumulation of this gas causing greenhouse effect and global warming.

Global warming can create the melting of ice of icebergs, resulting in rise in the sea level causing the flooding of many coastal areas. So, we must be aware of this problem and take every possible step to tackle it.

NCERT Solutions for Class 8 Science Pollution of Air and Water

10. Describe the threat to the beauty of the ‘Taj Mahal’.

Ans. The Taj Mahal is made of white marble, which is getting affected adversely due to the industrial pollutants from Agra, Mathura etc. the sulphur dioxide gas along with nitrogen oxide gas released from these industries mix with rain water to form Sulphuric acid that fall on marble of this monument. The acid rain corrodes the marbles and makes it yellowish.

This is a matter of great concern that world famous monument like Taj Mahal may get damaged due to the pollutants emitted by factories around it.

NCERT Solutions for Class 8 Science Pollution of Air and Water

11. Why does the increased level of nutrients in the water affect the survival of aquatic organisms?

Ans. Agriculture relies on the use of chemical fertilizers to improve the crop yield. All these chemicals dissolve in water and run into water bodies from the fields. These seep into the ground and pollute the ground water. Lot of algae in the ponds grow and keep the ponds green. This is caused due to excessive quantities of chemicals like nitrates and phosphorous present in fertilsers. Excessive growth of algae decrease the oxygen level of water bodies and kills the other aquatic animals living inside it.

NCERT solutions for Class 8 Science

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