Pollution of Air and Water Class 8 Important Questions and Answers

Important questions of Class 8 Science Chapter 18 Pollution of Air and Water is given below. These important questions will help students while preparing for the exam.  Practising these important questions will analyse their performance and work on their weak points. Score well in exam of Class 8 Science by going through these important questions. Students of Class 8 can download important questions of Class 8 Science Chapter 18 Pollution of Air and Water PDF by clicking the link provided below.

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

Here you can get Class 8 Important Questions Science based on NCERT Text book for Class 8. Science Class 8 Important Questions are very helpful to score high marks in board exams. Here we have covered Important Questions on Pollution of Air and Water for Class 8 Science subject.

Very Short Answer Questions

1. What is the percentage of nitrogen in atmosphere?
Answer:
 78%

2. What is the percentage of oxygen in atmosphere?
Answer: 
21%

3. Which problem arises by air pollution?
Answer:
 Respiratory problem

4. What is smog?
Answer:
 A thick fog-like layer in the atmosphere is called smog.

5. Which gases are responsible for acid rain?
Answer:
 Sulphur dioxide and nitrogen dioxide.

6. Which gas is responsible for greenhouse effect?
Answer:
 CO2 (carbon dioxide)

7. What is global warming?
Answer:
 Increasing temperature in atmosphere is called global warming.

8. Which phenomenon causes global warming?
Answer:
 Greenhouse effect

9. What is air pollution?
Answer: 
Addition of pollution in air is called air pollution.

10. Which gas is responsible for depletion of ozone layer?
Answer:
 Chlorofluorocarbons (CFCs)

11. Which fuel are pollution free?
Answer:
 CNG and LPG

12. What pollutes Ganga?
Answer: 
Untreated sewage, dead bodies, garbage, etc.

13. What do you mean by potable water?
Answer:
 Water which is suitable for drinking is called potable water.

14. Which chemical is used to purify water?
Answer:
 Chlorine

15. What radiation is absorbed by CO2?
Answer:
 Infrared radiation

16. Which rays are harmful for us?
Answer:
Ultraviolet rays

17. Which gas is called greenhouse gas?
Answer:
 CO2, Methane

18. What are alternative renewable fuels?
Answer:
 Solar energy, hydropower and wind energy

19. What do you mean by ‘Van Mahotsav’?
Answer: 
When lakhs of trees are planted in July every year, this is called Van Mahotsav.

20. When was Ganga Action Plan launched?
Answer:
 In 1985

21. Name one of the poisonous elements present in the exhaust of automobiles.
Answer:
 Lead.

Short Answer Type Questions

1: Why it is dangerous to burn polymers?

Answer: When polymers such as plastics are burned carbon containing gases are released. During the burning process, the carbon combines with oxygen present in the atmosphere & forms oxides of carbon. These gases have been linked with global warming, depletion of the ozone layer, acid rain, etc.

2: What is the cause of acid rain?

Answer: Oxides of nitrogen, sulphur, carbon produced by combustion of coal, petroleum, etc. dissolve in atmospheric water vapour. They form their corresponding acids like nitric acid, sulphuric acid, etc., and reach the earth’s surface as acid rain.

3: How does industry pollute the environment?

Answer: Factories pollute the air by pumping out chemicals that are harmful for all living things. Factories can pollute the environment through thermal pollution, chemical pollution, air pollution, noise pollution.

4: What are factory fumes?

Answer: Nitrous Oxides (NO, NO2 and N2O), Sulphur Dioxide, Carbon Dioxide and Carbon Monoxide are the famous ones, depending on the reactions that are taking place in the factory.

5: What are the harmful effects of acid rain?

Answer: Harmful effects of acid rain are as follows:

  • It irritates eyes and skin of human beings.
  • It inhibits germination and growth of seedlings.
  • It changes the fertility of the soil, destroys plants and aquatic life.
  • It causes corrosion of many buildings, bridges, etc.

6: What are the causes of increasing amount of carbon dioxide in air?

Answer: Human activities are the main reason for increasing the amount of carbon dioxide (CO2) in the atmosphere. The major sources of human emissions are the burning of fossil fuels such as coal, oil and natural gas for industry, driving our transport, heating our homes and generating electricity. Another factor is deforestation which increases the amount of carbon dioxide in the atmosphere, because new trees are not allowed to replace those removed.

7: Explain the three R principles to reduce pollution.

Answer: The three R principle includes recycle, reuse, and reduce of the available resources

8: Define water pollution.

Answer: Water pollution is the contamination of water bodies such as lakes, rivers, oceans, and groundwater caused by human activities, which can be harmful to organisms and plants which live in these water bodies.

9: List three major man-made source of air pollution.

Answer: Three major man-made source of air pollution are: Industrialisation, Urbanisation and Automobiles.

10: How does environment problem effect people health?

Answer: Air pollution is a significant risk factor for multiple health conditions including respiratory infections, heart disease, and lung cancer. The health effects caused by air pollution may include difficulty in breathing, wheezing, coughing and aggravation of existing respiratory and cardiac conditions.

11: How does burning of fossil fuels effects carbon dioxide level in the atmosphere?

Answer: Fossil fuels contain carbon, hydrogen, Nitrogen, Oxygen and some other elements. But the majority is Carbon. So when such fuels burn they combine with the Oxygen and Nitrogen in air to form Carbon dioxide, Nitrogen oxides etc. Even though Carbon monoxide is also formed, since they get converted to carbon dioxide when combustion gets completed. Any form of carbon when burns produce carbon dioxide.

12: What gastrointestinal problems may occur with antihistamine use?

Answer: Gastrointestinal problems include increased appetite, decreased appetite, nausea, vomiting, diarrhoea, and constipation.

13: Why acid rain and rust a harmful effect?

Answer: Acid rain and rust are harmful because it contains harmful gases like sulphuric acid etc. mainly sulphur gases because of these harmful gases when they reach the atmosphere when it rains it forms acid rain as the harmful gases mix with the atmosphere. These acid rain will affect plants, animals humans and all living organism. The acid mainly occurs at industrial areas because of these harmful gases which are released by the industrial effluents, they are definitely harmful to the atmosphere.

14: How does water get polluted?

Answer: It gets polluted by acid rain, oil spills, litter, insecticide mixing with fertilizers etc. The emission of waste heat from an electric generating station into a lake, causing common change through their stress. The discharge of nutrients containing sewer wastes, in a water body causing eutrophication.

15: How the disposal of garbage etc. would affects the living organisms in the river?

Answer: Disposal of garbage can affect badly the living organisms present in water, they will not be able to survive in water and may die.

16: What are the different ways in which water get contaminated?

Answer: Whenever harmful substances such as sewage, toxic chemicals, silt etc. get mixed with water, the water becomes polluted. Water get contaminated by the addition of agricultural chemicals like pesticides and fertilizers, these chemicals get carried away to the water bodies due to rains and flood which lead to water pollution, apart from these industrial wastes like harmful chemical wastes also causes water pollution. Sewage wastes like waste material from kitchens, toilets and laundry sources are also responsible for contaminating water.

17: Describe the threat to the beauty of Taj Mahal.

Answer: The major threat the beauty of Taj Mahal is the- “acid rain”. When acid rain falls on the monument that is made up of marble they react with marble to form a powder like substance that gets washed away by the rain, this phenomenon is known as marble cancer.

18: Explain some of the air pollutants.

Answer: Water pollutants refer to contaminants that enter a waterway from a single, identifiable source, such as a pipe or ditch. Examples of sources in this category include discharges from a sewage treatment plant, a factory, or a city storm drain, that altogether makes water unfit for drinking of human beings.

19: Differentiate between deforestation and van Mahotsav?

Answer: Deforestation refers to the removal of forest or stands of trees, but van Mahotsav is an annual pan-Indian tree planting festival, occupying a week in the month of July, during this week lakhs of trees are planted.

20: List some of the sources of air pollutions

Answer: Smoke released from the vehicles, dust and gases like carbon monoxide, carbon dioxide, nitrogen oxides and smokes that are released by industries and by burning of fossil fuels are the major air pollutants.

21: How chlorofluorocarbon is harmful to us?

Answer: Chlorofluorocarbons damage the ozone layer of atmosphere which protects us from harmful ultra violet radiation of sun.

22: How smog is harmful to us?

Answer: Smog causes breathing difficulties like asthma and cough in human beings and wheezing in children.

23: What do you mean by marble cancer?

Answer: When acid rain falls on the monument that is made up of marble they react with marble to form a powder like substance that gets washed away by the rain, this phenomenon is known as marble cancer.

24. What do you mean by air pollution?
Answer:
 When air is contaminated by unwanted substances which have a harmful effect on both living and non-living things, it is referred to as air pollution.

25. Name the pollutants produced by vehicles.
Answer:
 Vehicles produce high levels of pollutants like carbon monoxide, carbon dioxide, nitrogen oxide and smoke.

26. What is smog?
Answer:
 A thick fog like layer in the atmosphere, especially during winters is known as smog.

27. What is acid rain?
 Answer:
 Sulphur dioxide and nitrogen dioxide react with water vapour and form sulphuric acid and nitric acid. This acid drops down with rain, making the rain acidic. This is called acid rain.

28. What do you mean by Marble cancer?
Answer:
 Acid rain corrodes the marble of monuments. This phenomenon is called Marble cancer.

29. Write full form of CNG and LPG.
Answer:
 CNG – Compressed Natural Gas LPG – Liquefied Petroleum Gas

30. What is Greenhouse effect?
Answer:
 The reflected sun rays are trapped by the earth atmosphere. The trapped radiation warms the earth. It also warms the green house. This is called Greenhouse effect.

31. Describe global warming.

Answer: The increasing population and human activities cause the increase in  the carbon dioxide in the atmosphere. CO2 is a warm gas, which increases the temperature of the earth’s atmosphere. This is called global warming.

32. Write some effects of global warming.

Answer: The Following are the effects of global warming:
(i) It affects the green house.
(ii) The Gangotri glacier in the Himalayas has started melting.
(iii) It causes flood on earth.
(iv) It increases the temperature in the atmosphere.

33. What is water pollution?
Answer:
 The mixing of harmful substances such as sewage, toxic, chemicals, salt, etc. with water is called water pollution.

34. Write the causes of air pollution.

Answer: Causes of air pollution:
(i) Emitting smoke by forest fire.
(ii) Poisonous gases expelled by the various industries.
(iii) Poisonous gases emitted by vehicles.
(iv) Smoke and dust arising due to human activities.

35. How is acid rain caused?

Answer: Different industries produce sulphur dioxide and nitrogen dioxide. Those gases react with water vapour and form sulphuric acid and nitric acids. These acids fall on earth with rain and cause acid rain.

36. What is ozone? How is it helpful for our environment?

Answer: Ozone is a layer of gases around the earth. It is tri-atom of oxygen atom. It protects the earth from the ultraviolet rays of the sun. The ultraviolet rays cause many disease and damage to our earth. Thus ozone layer is helpful for our environment.

37. How does water get polluted?

Answer: Water gets polluted when unwanted and harmful chemical substances are added to the water. Also, untreated sewage and garbage added to water resources to pollute water.

Long Answer Type Questions

1: Write short notes on greenhouse gases.

Answer: Greenhouse gases are, sulphur dioxide carbon dioxide, nitrous oxide, and methane. These are the gas in the atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth’s atmosphere are water vapour, carbon dioxide, methane, nitrous oxide, and ozone. Atmospheric concentrations of greenhouse gases are determined by the balance between sources (emissions of the gas from human activities and natural systems) and sinks (the removal of the gas from the atmosphere by conversion to a different chemical compound.

2: Describe greenhouse effects.
Or
Explain global warming.

Answer: The greenhouse effect is the process which leads to increase in average earth’s temperature. That is the global warming. It results because of the greenhouse gases like water vapour, carbon dioxide, nitrous oxide, and methane, trap energy from the sun. When solar radiation reaches earth some of these radiations are absorbed by earth and rest are released back to the atmosphere. Greenhouse gases trap these radiations and do not allow them to go back. This helps in keeping earth warm and in survival of human beings. However an increase in amount of greenhouse gases can lead to excessive increase in earth’s temperature leading to global warming.

3: What are the respiratory disorders caused by air pollution?

Answer: Asthma: Asthma is a disorder that causes the airways of the lungs to swell and narrow, leading to wheezing, shortness of breath, chest tightness, and coughing.
Chronic obstructive pulmonary disease (COPD), also known as chronic obstructive lung disease is a progressive disease that makes it hard to breathe.
Emphysema is a long-term, progressive disease of the lungs that primarily causes shortness of breath.
Bronchitis is inflammation of the mucous membranes of the bronchi, the airways that carry airflow from the trachea into the lungs.

4: How acid rain does effects the environment?

Answer: Acid rain affects the environment in several ways:
1. It can leach nutrients from the soil making then unavailable to plant life.
2. It can affect the growth of plants as many plants have a specific soil pH for optimum growth
3. Acid precipitation can change the ionic balance in clayey soils affecting their structure.
4. In some soil acid precipitation may free up metals (e.g. lead) in the soil that can be taken up by the plants and contaminate the associated seeds or fruit.
5. It can affect fish and amphibians by reducing the pH of the water impacting their health and breeding success.

5: How acid rain does effects water ecosystem?

Answer: Together biological organisms and the environment in which they live are called an ecosystem. The plants and animals living within an ecosystem are highly interdependent. For example, frogs may tolerate relatively high levels of acidity, but if they eat insects like the mayfly, they may be affected because part of their food supply may disappear. Because of the connections between the many fish, plants, and other organisms living in an aquatic ecosystem, changes in pH or aluminium levels affect biodiversity as well. Thus, as lakes and streams become more acidic, the numbers and types of fish and other aquatic plants and animals that live in these waters decrease.

6: Explain Ganga Action Plan.

Answer: The Ganga action plan was, launched by Sri Rajeev Gandhi, the then Prime Minister of India on 14 Jan. 1985 with the main objective of pollution abatement, to improve the water quality by Interception, Diversion and treatment of domestic sewage and present toxic and industrial chemical wastes from identified grossly polluting units entering in to the river. The other objectives of the Ganga Action Plan are as under.

  • Control of non-point pollution from agricultural runoff, human defecation, cattle wallowing and throwing of unburnt and half burnt bodies into the river.
  • Research and Development to conserve the biotic, diversity of the river to augment its productivity.
  • New technology of sewage treatment like Up-flow Anaerobic Sludge Blanket (UASB) and sewage treatment through afforestation has been successfully developed.
  • Rehabilitation of soft-shelled turtles for pollution abatement of river have been demonstrated and found useful.
  • Resource recovery options like production of methane for energy generation and use of aquaculture for revenue generation have been demonstrated.
  • To act as trend setter for taking up similar action plans in other grossly polluted stretches in other rivers.

7: Clear transparent water is always fit for drinking, do you agree?

Answer: No, clear and transparent water is not always fit for the purpose of drinking. There are possibilities of disease causing microbes and dissolved impurities in the clear and transparent water. So, it is important to purify water before drinking , water can be purified by using water purifiers, by chlorination and by boiling.

8: Explain air pollution and its harmful effects. Also list some important measures to reduce air pollution.

Answer: Air pollution cab be reduced by adopting following ways:

  1. Reduce the use of car and other vehicles as these are the significant source of air pollution, so switching to a more gas-efficient vehicle will be a big help. Taking public transport to work rather than driving will reduces the number of carbon dioxide into the air. Using eco-friendly fuels in vehicles like CNG can also be beneficial.
  2. Reduce Waste: Manufacturing of unnecessary or disposable goods often produces air pollution, so reduced purchasing of disposables will help. In general, follow the solid waste mantra – “Reduce, Reuse, Repair, And Recycle” – and this will reduce air pollution as well from transporting, treating, or disposing of unnecessary wastes.
  3. Eliminate Toxic Chemical Use at Home – A surprising number of household or home shop chemicals are toxic and volatile. Many release vapours into the air, inside the home and out. This can be serious health threat to your family, and contributes to community-wide levels of air pollutants.
  4. Plant leafy trees and shrubs – Deciduous trees and shrubs (the kinds that drop leaves in the fall) are excellent air filters to help reduce smog and cool the air on hot summer days.

Air pollution is a significant risk factor for multiple health conditions including respiratory infections, heart disease, and lung cancer. The health effects caused by air pollution may include difficulty in breathing, wheezing, coughing and aggravation of existing respiratory and cardiac conditions.

9: What is air pollution? Write its causes.

Answer: When air is contaminated by unwanted substances which have a harmful effect on both the living and non-living, it is called air pollution. 

Causes of air pollution:
(i) Vehicles: Vehicles produce high level of pollutants like carbon dioxide, carbon monoxide, nitrogen oxides and smoke. Carbon monoxide is produced from incomplete burning of fuels such as petrol and diesel. It is a poisonous gas. It reduces the oxygen carrying capacity of the blood. 

(ii) Industrial emissions: Different poisonous and dangerous gases are emitted by factories. Industries use coal and petroleum products as fuel. These fuels emit various poisonous gases.

(iii) Natural pollutants: Natural sources like forest fire, and volcanic eruptions produce smoke and dust particles.

(iv) Human activities: Uses of fuels like cow dung, coal, wood produce air pollution. Agricultural practices like burning chaff after cultivation also pollute air.

10: What are CFCs? How do they create pollution?

Answer: CFCs stands for chlorofluorocarbons. These compounds also create air pollution. These compounds are used in refrigerators, air conditioners and aerosol sprays. They damage the ozone layer of the atmosphere. Ozone layer protects us from harmful effects of ultraviolet rays coming from the sun. These compounds cause depletion of ozone layer and form the ozone hole. If ultraviolet rays come on earth, they cause sun burn and skin cancer. We can reduce the harmful effects of CFCs by using less harmful chemicals in place of CFCs.

11: What is acid rain? How does it affect the Taj Mahal?

Answer: The industries located in and around Agra like rubber processing, automobile, chemicals and especially Mathura Oil Refinery produce pollutants like sulphur dioxide and nitrogen dioxide. These gases react with water vapours present in the atmosphere to form sulphuric and nitric acids. These acids mix with rain water. Such type of rain is called acid rain. Acid rain corrodes the marble of the Taj Mahal. This phenomenon is also called marble cancer.

12: What is greenhouse effect? How does it cause global warming?

Answer: The process of trapping of radiation by the earth’s atmosphere is called greenhouse effect. By this process the warming of the earth takes place. Without this process life would not have been possible on earth. But now it threatens life. CO2, methane, nitrous oxide, and water vapour are called greenhouse gases because they all contribute towards this effect.
CO2 is one of the components of air. As the amount of CO2 increases in the atmosphere due to which more greenhouse effect takes place. As a result, the average temperature of the earth’s atmosphere is gradually increasing. This is called global warming.

13: What is water pollution? How is water pollution caused?

Answer: The mixing of harmful substances such as sewage, toxic chemicals, slit, etc. in water is called water pollution.
Causes of water pollution: 

(i) Domestic discharges: The sewage from homes is collected and disposed off in rivers which cause water pollution.

(ii) Industrial discharges: Various harmful and toxic chemicals are discharged by various industries directly into the water. These chemicals spoil the water and make it unfit for drinking.

(iii) Religious rituals: Various religious rituals also cause the water pollution. Dispersion of dead bodies or remains in river causes water pollution.

(iv) Human activities: The bathing, washing and other human activities also cause water pollution.

14: Explain Ganga Action Plan.

Answer: An ambitious plan to save the river is called Ganga Action Plan. It was launched in 1985 to reduce the pollution level in the river. However, the increasing population and industrialisation have already damaged this mighty river beyond repair.

Ganga at Kanpur in Uttar Pradesh has one of the most polluted stretches of the river. Kanpur is one of the most populated town in U.P. People can be seen bathing, washing clothes and defecating in the river. They also throw garbage, flowers, idols of gods and goddesses and non-biodegradable polythene bags into the river. The industrial units discharge toxic chemicals and wastes into the river. Due to these activities the water in Ganga is polluted. Ganga Action Plan is related to reduce pollution in Ganga.

15: What is potable water? Write its properties.

Answer: The water which is suitable for drinking is called potable water.
Properties: 
(i) It is colourless.
(ii) It is odourless.
(iii) It is transparent.
(iv) It is germless.

16: Explain the process of water treatment to make it drinkable.

Answer: The water obtained from various sources is not safe for drinking. It requires purification before being supplied for drinking. Water is pumped from a source such as river or lake and is collected in a tank. The water is then cleaned in water works by allowing it to filter through layers of gravel and sand. It removes the dirt from water. Then water is treated with some chemicals like chlorine to kill the germs. The water is then supplied to the localities where it is to be used for drinking purposes.


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