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

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


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

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

Answer:-  The different ways in which water gets contaminated are following:-

  1. Practice of bathing and washing near a river.
  2. Industrial waste
  3. Sewage waste
  4. Agricultural chemicals
  5. cremating of dead bodies near river banks



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

Answer:- I can do the following things to reduce air pollution:

  1. I will use public transport whenever possible.
  2. I will raise awareness among people to reduce air pollution.
  3. I will plant as much trees as possible.
  4. I will properly dispose of the garbage and will never burn it.
  5. I will avoid vehicles for shorter distance.
  6. I will replace our vehicle fuel, diesel and petrol to LPG and CNG.


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

Answer:- No, it is not always true that clear, clean water is fit for drinking. It’s possible that they’re carrying disease-causing microbes. As a result, purifying water before consuming is a good idea.


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 measures would help us to ensure the supply of clean water to all its residents:-

  1. Cleaning the water tank properly on a regular basis.
  2. The area around the water pipes should be cleaned.
  3. The sewage lines should not come into contact with the water supply pipes.
  4. To purify water, chemical procedures such as chlorination must be done.



Question:- 5. Explain the differences between pure air and polluted air.

Answer:- Pure air is composed of 78 percent nitrogen, 21% oxygen, and 0.03 percent carbon dioxide. Other gases like argon, methane, neon, water vapour, and others are found in very small amounts. This air is considered to be polluted when it is contaminated by undesired substances such as nitrogen oxide, sulphur oxide, carbon monoxide, and other pollutants.


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

Answer:- Nitric acid and sulphuric acid are formed when sulphur dioxide and nitrogen dioxide react with water vapours in the atmosphere. Acid rain is formed when these acids fall to the ground as a result of precipitation.

Effects of acid rain are following:-

  1. It destroy the crops.
  2. It is harmful for historical monuments.
  3. It harms plants.
  4. It is harmful for animals and humans’ skin
  5. It harms the basic nutrients such as calcium from the soil.



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 ‘Green House Effect’ in your own words.

Answer:- The greenhouse effect is a term that refers to the warming of the earth’s environment. When the sun’s rays strike the earth, a portion of the radiation is absorbed by it, while the rest is reflected back into space. Greenhouse gases in the atmosphere trap these rays and prevent heat from escaping. This helps in the preservation of our planet by keeping it warm. The gases that cause this effect are CO2, methane, and CO.


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

Answer:- Good Morning,

Respected teachers and dear friends,

Global warming is defined as an increase in the average temperature of the Earth’s surface. Global warming is mostly caused by air pollution, which traps excessive heat captured by greenhouse gases. Global warming is a life-threatening concern because it creates plenty of health issues. We should take proper and immediate actions to stop this.

Friends, that’s all there is to it. Thank you for taking the time to read this. Have a wonderful day.


Question:- 10. Describe the threat to the beauty of the Taj Mahal.

Answer:- Acid rain is the most serious threat to the Taj Mahal, which is causing Marble cancer to it. Acid rain reacts with marble to generate a powdery substance that is washed away by the rain as it falls on the Taj, which is entirely composed of marble.  In addition, unburned hydrocarbons generated from the Mathura oil refinery in Agra are causing the Taj Mahal marble to yellow.


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

 Answer:- Increased levels of nutrients in the water have an effect on aquatic organisms’ survival because they act as nutrients for algae to flourish, and once these algae die, they serve as food for decomposers like bacteria, exhausting a large amount of oxygen in the water body. As a result, the oxygen content in the water, possibly killing aquatic organisms.