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SEBA Class 8 Science Chapter 9 Pollution of Air And Water
Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. SEBA Class 8 General Science Textual Solutions in English are part of All Subject Solutions. Here we have given Class 8 Science Textbook Question Answer, SEBA Class 8 Science English Medium Textbook Solutions for All Chapters, You can practice these here.
Pollution of Air And Water
Chapter: 9
PART – I
EXERCISE
1. What are the different ways in which water gets contaminated?
Ans: Water gets contaminated by:
(i) Discharge of untreated sewage into water bodies.
(ii) Disposal of industrial waste into rivers and lakes.
(iii) Agricultural runoff containing fertilizers and pesticides.
(iv) Oil spills and other chemical pollutants.
2. At an individual level, how can you help reduce air pollution?
Ans: As individuals, we can help reduce air pollution by:
(i) Using public transport or carpooling.
(ii) Avoiding the use of vehicles for short distances.
(iii) Planting trees and avoiding burning garbage or leaves.
(iv) Using clean fuels like CNG and electricity.
3. Clear, transparent water is always fit for drinking. Comment.
Ans: This statement is incorrect. Clear and transparent water may still contain harmful microorganisms or dissolved chemicals that are not visible but can make the water unfit for drinking. Proper testing and purification are required.
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.
Ans: Measures may include:
(i) Regular testing and monitoring of water quality.
(ii) Proper treatment of water before distribution.
(iii) Repairing leaking pipelines to avoid contamination.
(iv) Spreading awareness about water conservation.
(v) Setting up sewage treatment plants.
5. Explain the differences between pure air and polluted air.
Ans: (i) Pure air contains 78% nitrogen, 21% oxygen, and 1% other gases. It is free from harmful substances.
(ii) Polluted air contains harmful gases like carbon monoxide, sulphur dioxide, and particulate matter, which can cause health problems.
6. Explain circumstances leading to acid rain. How does acid rain affect us?
Ans: Acid rain is caused when pollutants like sulphur dioxide (SO₂) and nitrogen dioxide (NO₂) released from burning fossil fuels mix with rainwater to form acids.
It damages buildings, affects soil fertility, harms aquatic life, and irritates eyes and skin.
7. Which of the following is not a greenhouse gas?
(a) Carbon dioxide.
(b) Sulphur dioxide.
(c) Methane.
(d) Nitrogen.
Ans: (d) Nitrogen.
8. Describe the ‘Green House Effect’ in your own words.
Ans: The greenhouse effect is the process by which greenhouse gases like CO₂ and methane trap heat from the sun in the Earth’s atmosphere. This helps keep the Earth warm, but excess greenhouse gases lead to global warming.
9. Prepare a brief speech on global warming. You have to deliver the speech in your class.
Ans: “Good morning everyone,
Global warming is the increase in the Earth’s average temperature due to the buildup of greenhouse gases. It is caused mainly by human activities such as burning fossil fuels and deforestation. Global warming leads to melting glaciers, rising sea levels, and extreme weather. We must reduce pollution, conserve energy, and plant more trees to fight this threat. Let us all do our part to protect our planet.
Thank you!”
10. Describe the threat to the beauty of the Taj Mahal.
Ans: The Taj Mahal, made of white marble, is one of the most beautiful monuments in the world. However, its beauty is being damaged by air pollution. Smoke released from nearby factories and vehicles contains harmful gases like sulphur dioxide. When this gas mixes with rainwater, it forms acid rain. Acid rain reacts with the marble and causes it to lose its shine and turn yellow. This slowly corrodes the surface of the Taj Mahal and affects its appearance. If pollution is not controlled, the monument may suffer permanent damage.
11. Why does the increased level of nutrients in the water affect the survival of aquatic organisms?
Ans: When there are too many nutrients like nitrates and phosphates in water (often from fertilizers or sewage), it causes too much algae to grow on the surface of the water. This is called eutrophication. The thick layer of algae blocks sunlight and uses up a lot of oxygen in the water. As a result, other aquatic plants and animals, especially fish, do not get enough oxygen to survive. This reduces biodiversity and can lead to the death of many aquatic organisms.
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