CBSE Class 8 Science Exemplar Chapter 18: Pollution of Air and Water NCERT Solutions

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NCERT Solutions PDF Class 8 PDF

This chapter delves into the critical environmental issues of air and water pollution, providing students with a comprehensive understanding of their causes, effects, and prevention methods. The NCERT Solutions for Class 8 Science Exemplar Chapter 18 cover key concepts such as the composition of air, sources of air pollution, and the impact of human activities on air quality. It also addresses water pollution, its consequences, and the importance of water conservation. The solutions explain various types of pollution, including the phenomenon of 'marble cancer' affecting historical monuments like the Taj Mahal, and the role of incomplete combustion in producing harmful gases like carbon monoxide. These solutions are designed to help students grasp the scientific principles behind pollution and encourage responsible environmental practices, aiding in their exam preparation.

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Quick info

BoardCBSE
ClassClass 8
SubjectScience Exemplar
Session2026
LanguageEnglish
TypeNCERT Solutions
ChapterChapter 18

Chapter summary

Chapter 18 of the Class 8 Science Exemplar focuses on Pollution of Air and Water. The NCERT Solutions provide clear explanations for multiple-choice questions covering the composition of air, sources of air pollution, methods to reduce pollution, and water conservation techniques. It highlights the environmental impact of industrial activities and vehicular emissions, explaining concepts like acid rain and its effect on monuments. The solutions aim to build a strong foundation in environmental science for students.

Learning outcomes

  • Identify the main components of air and their percentages.
  • Distinguish between sources and non-sources of air pollution.
  • Understand the role of vehicles and public transport in air pollution.
  • Recognize the 'Reduce, Reuse, Recycle' principle for resource conservation.
  • Explain the causes and effects of air pollution on monuments like the Taj Mahal.
  • Identify the products of incomplete fuel combustion.
  • Understand the concept of acid rain and its impact.

Topics covered

Paper topics

  • Air Composition
  • Oxygen
  • Air Pollution Sources
  • Vehicular Pollution
  • Public Transport Benefits
  • Water Conservation
  • Reduce, Reuse, Recycle
  • Marble Cancer
  • Acid Rain
  • Incomplete Combustion
  • Carbon Monoxide
  • Environmental Protection

Important topics

  • Sources of Air Pollution
  • Water Conservation Strategies
  • Impact of Pollution on Monuments
  • Acid Rain and its Causes
  • Harmful Gases from Incomplete Combustion

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Questions and Solutions

Multiple Choice Questions - 1

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
  1. nitrogen
  2. oxygen
  3. ozone
  4. argon
Solution: The correct option is (b) oxygen. Air is primarily composed of nitrogen (about 78%) and oxygen (about 21%), with smaller amounts of other gases like argon (about 0.93%) and trace amounts of others, including ozone. Oxygen is indispensable for respiration in humans and most living organisms.

Multiple Choice Questions - 2

2. Which of the following is not a source of air pollution?
  1. automobile exhaust
  2. burning of firewood
  3. windmill
  4. power plant
Solution: The correct option is (c) windmill. A windmill is a device that harnesses wind energy and does not release any harmful gases or pollutants into the atmosphere. In contrast, automobile exhausts, burning firewood, and power plants are significant sources of air pollution.

Multiple Choice Questions - 3

3. Boojho wishes to contribute in reducing air pollution. Which vehicle should he use for going to school?
  1. car
  2. school bus
  3. autorickshaw
  4. scooter
Solution: The most environmentally friendly option for Boojho is (b) school bus. A school bus carries many students at once, which significantly reduces the number of individual vehicles on the road. This collective transport method helps decrease overall fuel consumption and emissions, thereby contributing to the reduction of air pollution.

Multiple Choice Questions - 4

4. Which of the following is not a way to conserve water?
  1. replace
  2. reduce
  3. reuse
  4. recycle
Solution: The correct option is (a) replace. The widely accepted principles for conserving natural resources, including water, are 'Reduce', 'Reuse', and 'Recycle'. These strategies aim to minimize waste and maximize the efficient use of resources. 'Replace' does not fit into this framework of conservation.

Multiple Choice Questions - 5

5. The type of pollution which is likely to affect Taj Mahal in Agra to a greater extent is
  1. air pollution
  2. water pollution
  3. soil pollution
  4. noise pollution
Solution: The correct option is (a) air pollution. Air pollution, particularly from industrial emissions and vehicular exhaust in the vicinity of Agra, releases pollutants like sulfur dioxide and particulate matter. These pollutants react with the marble of the Taj Mahal, causing it to lose its luster and turn yellow, a phenomenon often referred to as 'marble cancer'.

Multiple Choice Questions - 6

6. Incomplete combustion of fuel such as petrol and diesel gives
  1. nitrogen oxide
  2. sulphur dioxide
  3. carbon monoxide
  4. carbon dioxide
Solution: The correct option is (c) carbon monoxide. When fuels like petrol and diesel do not burn completely due to insufficient oxygen, they produce carbon monoxide (CO) instead of carbon dioxide (CO2). Carbon monoxide is a poisonous gas that reduces the oxygen-carrying capacity of the blood.

Multiple Choice Questions - 7

7. The phenomenon of marble cancer is due to
  1. soot particles
  2. CFCs
  3. fog
  4. acid rain
Solution: The correct option is (d) acid rain. Acid rain is formed when pollutants like sulfur dioxide and nitrogen oxides in the atmosphere react with water, oxygen, and other chemicals to form sulfuric and nitric acids. These acids fall to the earth as acid rain, which corrodes materials like marble, causing damage to historical monuments. This process is termed 'marble cancer'.

Common mistakes

  • Confusing components of air with pollutants.
  • Not recognizing sustainable practices like using public transport.
  • Misunderstanding the 'Reduce, Reuse, Recycle' mantra.
  • Failing to connect specific pollutants to their environmental effects.

Revision tips

  • Review the percentages of gases in the air and their importance.
  • List common sources of air and water pollution discussed in the chapter.
  • Understand the 'Reduce, Reuse, Recycle' principle for water conservation.
  • Memorize the explanation for 'marble cancer' and acid rain.
  • Focus on the environmental impact of incomplete fuel combustion.

Practice MCQs

Q1. Which gas constitutes approximately 21% of the Earth's atmosphere and is vital for human respiration?

Q2. Identify the option that is NOT a source of air pollution.

Q3. To minimize his contribution to air pollution, which mode of transport should Boojho choose for his daily commute to school?

Q4. Which of the following is NOT considered a strategy for conserving water resources?

Q5. The significant deterioration of the Taj Mahal's white marble, causing it to turn yellow, is primarily attributed to which type of pollution?

Q6. Incomplete combustion of fuels like petrol and diesel primarily results in the formation of which harmful gas?

Q7. The phenomenon known as 'marble cancer', which affects historical monuments, is caused by:

Frequently asked questions

What is the main focus of CBSE Class 8 Science Exemplar Chapter 18?

Chapter 18 focuses on the critical environmental issues of air and water pollution, including their causes, effects, and methods for conservation and prevention.

Which gas makes up about 21% of the air and is essential for life?

Oxygen is the gas that constitutes approximately 21% of the air and is essential for the survival of human beings and most other living organisms.

What are the recommended ways to conserve water?

The key principles for conserving water and other natural resources are to Reduce consumption, Reuse materials, and Recycle them. 'Replace' is not a standard conservation method.

What causes 'marble cancer' affecting historical monuments?

'Marble cancer' is caused by acid rain, which results from air pollutants like sulfur dioxide and nitrogen oxides reacting with atmospheric moisture, leading to the deterioration of marble.

Why is using a school bus a better option for reducing air pollution?

A school bus carries many students, thus reducing the total number of vehicles on the road and consequently lowering overall emissions and air pollution compared to individual car usage.

What harmful gas is produced from the incomplete burning of fuels?

Incomplete combustion of fuels like petrol and diesel produces carbon monoxide (CO), a toxic gas, instead of carbon dioxide (CO2).

Important links

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