Pollution of Air and Water NCERT Solutions - Class 8 Science

NCERT Solutions for Class 8 Science Chapter 18 - Free PDF Download

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Access NCERT Solutions for Science Chapter 18 – Pollution of air and water part-1

Access NCERT Solutions for Science Chapter 18 – Pollution of air and water

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

Ans: Water gets contaminated by: 

1. Dumping Agricultural chemicals and wastes.

2. Industrial chemicals waste and oil spill.

3. Sewage wastes.

4. Throwing plastics and chemical wastes in water.

5. Washing vehicles and clothes.

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

Ans: To reduce air pollution,

1. One can use public transport. Use bicycles instead of vehicles for short distances which also maintains physical health.

2. Use clean fuels such as LPG and CNG instead of diesel and petrol.

3. Dispose garbage in a proper way instead of burning it which causes pollution.

4. Control the emissions from vehicles and household chimneys.


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

Ans: No, clear, transparent water is not always fit for drinking because it contains microorganisms causing harmful diseases. Hence, we need to purify water before drinking. Water can be purified with the help of a water purifier or we can boil it.

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: To ensure the supply of clean water to all residents the following steps must be taken: 

(i) Water should be treated properly before use to make it free from harmful microorganisms.

(ii) Chemical methods such as chlorination should be used to purify water.

(iii) Water pipes must be maintained properly to avoid leakages and wastage of water.

(iv) Water must be maintained by building it in a clean surrounding.

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

Ans:  Difference between pure and polluted air:

1. Pure air: It is a mixture of nitrogen, oxygen and carbon dioxide with other traces of gases like ozone, methane water vapour and it is free from harmful gases.

2. Polluted air: When the composition of air is altered by addition of harmful gases like Sulphur dioxide, carbon monoxide, nitrogen dioxide and CFCs, then the air is said to be polluted. 

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

Ans: Circumstances leading to acid rain are:

(i) Burning of fossil fuels contains traces of Sulphur and trapped impurities.

(ii) These traces and trapped impurities release gases like Sulphur dioxide and nitrogen dioxide. 

(iii) Sulphur dioxide and nitrogen dioxide reacts with water vapour of the atmosphere forming respective acids like sulphurous acid. Which results in acid rain.

Effects of acid rain:

(i) Acid rains damage plants, trees and crops.

(ii) Acid rain removes minerals and nutrients from the soil.

(iii) Acid rain causes corrosion of buildings and structures. Example: Taj Mahal, Eiffel Tower are maintained in a span of time. 

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

(a) Carbon dioxide

(b) Sulphur dioxide 

(c) Methane 

(d) Nitrogen 

Ans: (d) Nitrogen

8. Describe the ‘Greenhouse Effect’ in your own words.

Ans: Greenhouse effect:

(a) Greenhouse effect is caused by greenhouse gases which include carbon dioxide, methane, CFCs which are released into the atmosphere.

(b) The gases increase the temperature of the atmosphere by trapping radiation (i.e. not allowing the dissipation of heat). 

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

Ans: Global warming:

(i) Global warming is the increase in temperature of the earth’s Atmosphere due to human activities. 

(ii) Pollutants like methane, carbon dioxide, CFC's increases the temperature of the atmosphere, by trapping the radiation from the sun and reflecting back to the earth’s surface.  

(iii) This increase in temperature will result in melting of ice in the glaciers in Arctic and Antarctic regions. 

(iv) The increased sea level due to the melting of glaciers will result in floods in low coastal area regions. 

(v) The main constituent causing global warming is the pollution from industries and automobiles.

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

Ans: Threat to the beauty of Taj Mahal:

1. Acid rain which causes marble cancer and corrosion of buildings is the major threat to the beauty of the Taj Mahal. 

2. Acid rain is a mixture of acids and water Vapour which reacts with marble forming a powder mass removed by the rain. This phenomenon is known as marble cancer. 

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

Ans: The increased level of nutrients in the water affect the survival of aquatic organisms: 

(i) Increase in the growth of microorganisms such as algae is because of the increase in level of nutrients in the water.

(ii) When the algae die, the decomposition of algae by decomposers require huge amount of oxygen. 

(iii) The oxygen in water is utilized for decomposition which decreases the oxygen content in water, leading to the shortage of oxygen for living organisms in water. Which might result in death of living organisms.

NCERT Solutions for Class 8 Science Chapter 18 - Pollution of Air and Water

NCERT Grade 8 Science Chapter 18, Pollution of Air and Water deals with a grave subject and its effects. The chapter also address the solution to the hazardous phenomenon of Pollution and how can one contribute to its reduction on the individual level. Air Pollution, How does Air Get Polluted? Case Study— The Taj Mahal,  Greenhouse Effect, What can be Done? Water Pollution, How does Water Get Polluted? What is Potable Water and How is Water Purified ? What Can be Done? are some of the major topics discussed in this chapter.

Examples and pictorial representation help to understand the effect of Air and Water Pollution in a better way. The learning experience of the students will inspire them to act towards the eradication of pollution. Activities and Project Work, prove to be an eye-opener to the students. Case Studies help the students to understand the current condition caused due to unattended levels of Air and Water Pollution. Technical terms learnt throughout the chapter, summarising points and exercises given at the end of the chapter help to glance through the chapter and self-assessment.This chapter will take the students through the harmful world of Pollution. It will help them to not only develop a grip of the topic but also master the concepts that will help them to perform better. 

Get 100 percent accurate NCERT Solutions for Class 8 Science Chapter 18 (Pollution of Air and Water) explained by expert Science teachers. We provide solutions for the questions given in Class 8 Science textbook as per CBSE Board guidelines from the latest NCERT book for Class 8 Science. The topics and sub-topics in Chapter 18 Pollution of Air and Water are given below.

Ex 18.1 - Air Pollution

Ex 18.2 - How does Air Get Polluted

Ex 18.3 - Case Study - The Taj Mahal

Ex 18.4 -  Greenhouse Effect

Ex 18.5 - What can be Done?

Ex 18.6 - Water Pollution

Ex 18.7 - How does Water Get Polluted

Ex 18.8 - What is Potable Water and How is Water Purified?

Ex 18.9 - What can be Done?.

We cover all exercises in the chapter given below:- 

Chapter 18 - 11 Questions with Solutions. 

Other than given exercises, you should also practice all the solved examples given in the book to clear your concepts on Pollution of Air and Water. Download the free PDF of Chapter 18 Pollution of Air and Water take the print out to keep it handy for your exam preparation.

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