CBSE – 8th Standard Science


Question Bank – Chapter 18 – Pollution of Air & Water

Chapter 18 

Pollution of air and water


Q1. What are pollutants?

Ans. Pollutants are the substances which contaminate air and water. Harmful gases, chemicals, sewage are the major pollutants of air and water.


Q2. What kind of health problem are found due to air pollutants on road ?

Ans. Vehicles produce high levels of pollutants like carbon monoxide, carbon dioxide, nitrogen oxides ,Carbon monoxide is a poisonous gas it reduces the oxygen-carrying capacity of the blood and causes respiratory trouble.


Q3. What are the major source of  Air pollutant?

Ans. Air gets polluted from natural sources like smoke and dust arising from forest fires or volcanic eruptions, the sources of air pollutants are factories, power plants, automobile exhausts and burning of firewood and dung cakes.


Q4. What are the different ways in which water gets contaminated ?

Ans. Industrial waste is thrown to rivers, it contaminates water and Sewage, agricultural chemicals, detergents seep into ground and contaminate water.


 Q5. What should be done to reduce air pollution at individual level ?

Ans. Use of Cleaner fuels like CNG and LPG, alternative fuels like solar energy, hydropower and wind energy. More use of bicycles, travelling by public trnasport  and  planting more trees can help us to reduce air pollution.


Q6. Explain circumstances leading to acid rain. How does acid rain affect us?

Ans. Air polluting gases like sulphur dioxide and nitrogen dioxide react with the water vapour and form sulphuric acid and nitric acid. These acids drop down with rain which is called acid rain.


Q7. Describe the threat to Beauty of the Taj?

Ans. The industries located in and around Agra like rubber processing, automobile and oil refinery, produce pollutants which causes acidic rain, it corrodes the marble of the Taj and has become threat for its beauty .


Q8. What is Green house effect ?

Ans. Sun rays warm the earth’s surface. A part of the radiation  that falls on the earth is absorbed by it and a part is reflected back into space. A part of the reflected radiation is trapped by the atmosphere this trapping of radiations by the atmosphere is called the greenhouse effect.


Q9. What is Global warming ?

Ans. Global warming has become a major concern for us, Gases like carbon dioxide, methane, nitrous oxide and water vapour traps heat and does not allow it to escape into space. As a result, the average temperature of the earth’s atmosphere is gradually increasing that is  called global warming.



Q10. What kind of pollutants are responsible for hole in ozone layer?

Ans. CFCs damage the ozone layer of the atmosphere. chlorofluorocarbons (CFCs) which are used in refrigerators, air conditioners and aerosol sprays are pollutant that are responsible for damage in ozone layer


Q11. Why does the increased level of nutrients in the water affect the survival of aquatic organisms?

Ans. The increased level of nutrients are used by algae to flourish, When algae die, they serve as food for bacteria, they use a lot of oxygen in water thus oxygen level decreases which may kill aquatic organisms.


Q12. Is hot water a pollutant?

Ans. Hot water can also be a pollutant .This is usually released from power plants and industries. It is released into the rivers and  raises the temperature of the waterbody, adversely affecting the animals and plants living in it



Try these :- 

Match the column :-

Pollutant                                          Impact on health

  1. Nitrogen oxide i) unconsciousness
  2. Sulphur dioxide  ii) chest pain
  3. Carbon monoxide iii) heart diseases
  4. Lead  iv) reduced visibility
  5. Flyash  v) decreased Hemoglobin


Differentiate between effect of ozone in different layers of atmosphere?

Name any four greenhouse gases and measures to reduce them.

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