CBSE Class 8 Science Chapter 18 Pollution of Air and Water

NCERT Solutions for Class 8 Science Chapter 18 Pollution of Air and Water Questions and Answers are prepared. Best Solutions, Video Classes, Worksheet, Test Exam Paper for Class 8 Science Chapter 18 Pollution of Air and Water.

Class 8 Science Chapter 18 Pollution of Air and Water Textbook Exercise Questions and Answers

Question 1. : What are the different ways in which water gets contaminated?
Answer: The different ways in which water gets contaminated are as follows:

  • Many industries discharge harmful chemicals into rivers and streams. Examples are oil refineries, paper factories, textile and sugar mills, etc.
  • The pesticides and weedicides used for the protection of crops get dissolved in water and are washed into water bodies from the fields.
  • Many times, untreated sewage is thrown directly into rivers.
  • Faecal matters of mammals get added into water bodies.
  • Practice of bathing and washing near a water body.
  • Practice of cremating the dead bodies near river banks.

CBSE Class 8 Science Chapter 18 Pollution of Air and Water
CBSE Class 8 Science Chapter 18

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

Answer: At an individual level, one can do the following things to reduce air pollution:

  • One can use vehicles consuming fuels like CNG and unleaded petrol, rather than those using fuels like diesel, petrol, etc.
  • One can avoid unnecessary usage of vehicles and try using public transport more.
  • One can avoid using crackers.
  • One can generate awareness about air pollution among friends and neighbors.
  • One can switch over to alternative fuels instead of the fossil fuels for energy requirements. These could be solar energy, hydro power and wind energy.
  • One can plant trees and nurture those trees already present in the neighborhood.
  • Dry leaves can be dumped in a compost pit rather than burning in open.

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

Answer: Clear, transparent water is not always fit for drinking. This is because the water which looks clean might contain disease-carrying microorganisms and dissolved impurities in it. These microorganisms and impurities could be harmful to us. Hence, it is essential to purify water before drinking.


Question 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.

Answer: Following is a list of measures that would help a town to ensure the supply of clean water to all its residents:

  • Implementation of strict laws for industrial units so that the polluted water is not disposed off directly into rivers and takes.
  • Treatment of water must be done to make it free from harmful germs, chemicals and impurities.
  • The water supply pipes must be properly maintained to avoid any corrosion, breakage and leakage.
  • Campaigns and awareness programmes should be organised to keep water resources clean and educate people to save water.

Question 5. Explain the differences between pure air and polluted air.
Answer: Following are the differences between pure air and polluted air:

Pure airPolluted air
1. Pure air contains around 78% nitrogen, 21 % oxygen, and 0.03% carbon dioxide, also small amounts of argon, methane, ozone, and water vapours.1. Polluted air includes gases like sulphur dioxide, nitrogen dioxide, carbon dioxide, etc., and other particulate matter.
2. Smog is not present.2. Smog can be present.
3. Not harmful for human beings.3. Harmful for human beings as it causes respiratory diseases like asthma.
Class 8 Science Chapter 18

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

Answer: Chemicals like sulphur dioxide and nitrogen dioxide are released into the air by the smoke of vehicles. These pollutants react with the water vapour present in the air and form sulphuric and nitric acid. When it rains, these acids get dissolved in rainwater making it acidic. Such kind of rain is called acid rain.

Following is the list which shows how acid rain affects us:

  • It can cause skin irritation.
  • It drains out nutrients like calcium from the soil.
  • It causes corrosion to bridges, buildings and other metallic objects.
  • It can destroy plants and aquatic life.

Question 7. Which of the following is not a greenhouse gas?
a. Carbon dioxide
b. Sulphur dioxide
c. Methane
d. Nitrogen

Answer: d. Nitrogen


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

Answer: The greenhouse effect is the trapping of sunlight in earth’s atmosphere due to increased concentration of greenhouse gases like carbon dioxide, methane and water vapour in the atmosphere. These gases trap solar radiations reflected back by the earth. This helps in keeping our planet warm and thus, helps in human survival. However, an increase in the amount of greenhouse gases can lead to an increase in the earth’s temperature leading to global warming.


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

Answer: Global warming is a serious concern of the modern times. We are using more cars and bikes than ever. We are also consuming products at a large scale which means more and more factories are coming up to satisfy our growing needs. Alt of this has resulted in an increased level of carbon dioxide in the atmosphere.

The increased level of carbon dioxide has resulted in global warming. Due to this, the summers have become hotter and winters have become much colder. We are observing increased instances of flash floods. Weather changes are drastic, and this is being attributed to global warming. Global warming might result in total disaster for us. A time will come when the temperature on the earth will finish the life. It is high time we stand up and take a pledge to fight against global warming.


Question 10. Describe the threat to the beauty of the Taj Mahal.
Answer: Acid rain is a major threat to the beauty of the Taj Mahal. When acid rain falls on the monument made of marble, they react with marble to form a powder-like substance that is then washed away by the rain.

This phenomenon is known as marble cancer. Also, the soot particles emitted from the Mathura oil refinery located near Agra are leading to the yellowing of the marble.


Question 11. Why does the increased level of nutrients in the water affect the survival of aquatic organisms?
Answer: The pesticides and weedicides used for the protection of crops get dissolved in water and are washed into water bodies from the fields. These act as nutrients for algae to flourish.

Once these algae die, they serve as food for decomposes like bacteria. In this process, a lot of oxygen in these ponds gets used up. This results in a decrease in the oxygen level of water which kills the aquatic organisms.


NCERT Class 8 Science Chapter 18 Extended Learning Activities and Projects

Question 1. In some cities, a pollution check has been made compulsory for vehicles. Visit a petrol pump in order to learn about the process of conducting a pollution check. You may systematically record your findings in the following areas:

  • Average number of vehicles checked per month.
  • Time taken to check each vehicle.
  • Pollutants checked for.
  • The process of testing
  • Permissible levels of emission of various gases.
  • Measures taken if the emitted gases are above the permissible limits.
  • How frequently is a pollution check required?

Hint:
Do it yourself.


Question 2. Conduct a survey in your school to investigate various environment related activities that have been undertaken. The class can divide itself into two groups, with each group looking at a different area. For example, one group can find out whether there is an environment club in the school. What are its objectives? What is its calendar of events? How can you become a member?

If your school does not have such a club, you even think of starting one along with a few of your friends.
Hint:
Do it yourself.


Question 3. Organise a field visit to a river in or around your town with the help of your teachers. Observations followed by discussion could focus on

  • the history of the river.
  • cultural traditions.
  • role of the river in meeting the town’s water needs.
  • pollution concerns.
  • sources of pollution.
  • effects of pollution on the people living by the riverside as well as those living far away.

Hint:
Do it yourself.


Question 4. Find out with the help of your teachers and the internet (if possible), whether there are any international agreements to control global warming. Which are the gases covered under these agreements?

Hint:
Following are the international agreements aimed at controlling global warming:
The Kyoto Protocol is an international agreement on climate change, developed under the United Nations Framework Convention on Climate Change (UNFCCC). The Protocol encourages 192 parties to reduce their greenhouse gas emissions, with many developed nations having binding emissions reduction targets.

The Paris Agreement was agreed in 2015 by 175 parties. The aim of the agreement is to keep global warming to ‘well below’ 2°C, and strive to limit warming to 1.5°C.

The Montreal Protocol on ozone-damaging gases does not directly address climate change, but ozone-damaging gases contribute to global warming. The 1987 Montreal Protocol binds 196 nations to reduce the emission of ozone-damaging gases, commonly used in fridges, foam and industrial applications.



Class 8 Science Chapter 18 Pollution of Air and Water Additional Important Questions and Answers

What is air pollution?

Contamination of air which makes it harmful for living beings is called air pollution.

How is carbon monoxide produced?

Carbon monoxide is produced from the incomplete burning of fuels like petrol and diesel.

What is the full form of CFC?

Chlorofluorocarbon.

Name some cleaner fuels.

CNG, LPG, unleaded petrol, etc.

What is smog?

A mixture of smoke and fog is called smog.

What is acid rain?

When rainwater becomes acidic due to dissolution of the oxides of sulphur and nitrogen, it is called acid rain.

What is global warming?

Overall increase in the temperature of the earth’s atmosphere is called global warming.

What is water pollution?

Contamination of water which makes it harmful for living beings is called water pollution.

Name some water pollutants.

Sewage, toxic chemicals, silts, etc.

Name some greenhouses gases.

Methane, carbon dioxide, nitrous oxide and water vapour.

What is chlorination?

Chlorination is the chemical method for purifying water, by adding chlorine tablets or bleaching powder to it.

What are the harmful effects of smog?

The smog causes breathing difficulties like asthma, cough and wheezing in human beings and also reduces visibility.

Which gas is mainly responsible for global warming?

CO2 gas is mainly responsible for global warming.

When was Ganga Action Plain implemented?

In 1985, Ganga Action Plan was implemented.

In which state is Ganga river most polluted?

Ganga river is most polluted in Kanpur.

How are dust particles added in air?

There are many sources of dust particles, e.g., stone quarries, mines, power plants, construction sites, etc.

How is carbon monoxide produced?

Carbon monoxide is produced by incomplete burning of fuels petrol and diesel.

What are the natural causes of air pollution?

Smoke and dust from forest fires and volcanic eruptions pollute the air and are the natural causes of air pollution.

How does boiling purify water?

Boiling purifies water by killing the germs present in it.

What is the full form of three R?

Reduce, Reuse and Recycle.

Class 8 Science Chapter 18 Pollution of Air and Water

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