NCERT Solutions for Class 8th Science Chapter 13 Pollution of Air and Water textual questions and answers based on the latest syllabus of CBSE and JKBOSE NCERT Books
Exercises
1. What are the different ways in which water gets contaminated?
- Water gets contaminated through various ways such as:
- Discharge of untreated industrial waste into water bodies.
- Dumping of domestic sewage and garbage.
- Runoff from agricultural fields carrying pesticides and fertilizers.
- Oil spills and leaks.
- Erosion of soil and siltation.
- Leakage from landfills and septic tanks.
2. At an individual level, how can you help reduce air pollution?
- As an individual, you can reduce air pollution by:
- Using public transport, carpooling, or biking instead of driving alone.
- Conserving energy at home and at work.
- Reducing, reusing, and recycling materials.
- Planting trees and maintaining greenery.
- Avoiding the burning of leaves, trash, and other materials.
- Using eco-friendly products and fuels.
3. Clear, transparent water is always fit for drinking. Comment.
- Clear, transparent water is not always fit for drinking. It may still contain harmful microorganisms, chemicals, and pollutants that are not visible to the naked eye. Therefore, water should be properly treated and tested before drinking to ensure it is safe.
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.
- To ensure clean water supply:
- Regularly monitor and treat water sources.
- Implement strict regulations for industrial discharge.
- Promote rainwater harvesting and groundwater recharge.
- Maintain and upgrade water treatment facilities.
- Educate residents on water conservation and pollution prevention.
- Ensure proper disposal and treatment of sewage and waste.
5. Explain the differences between pure air and polluted air.
- Pure Air: Contains 78% nitrogen, 21% oxygen, and small amounts of other gases like carbon dioxide, argon, and water vapor, free from harmful pollutants.
- Polluted Air: Contains harmful substances such as smoke, dust, chemicals, and biological materials, which can harm human health and the environment.
6. Explain circumstances leading to acid rain. How does acid rain affect us?
- Acid rain is caused by the release of sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) into the atmosphere from burning fossil fuels. These gases react with water vapor to form sulfuric and nitric acids, which fall to the ground as acid rain.
- Effects of acid rain include:
- Damage to buildings and monuments.
- Harm to aquatic life in rivers and lakes.
- Soil degradation affecting plant life.
- Respiratory problems in humans and animals.
Choose the correct option in Questions 7-8
7. Which of the following is not a greenhouse gas?
(a) Carbon dioxide (b) Sulfur dioxide (c) Methane (d) Nitrogen
- Correct answer: (d) Nitrogen
8. Describe the ‘Greenhouse Effect’ in your own words.
- The Greenhouse Effect is the process by which certain gases (greenhouse gases) in the Earth’s atmosphere trap heat from the sun, preventing it from escaping back into space. This trapped heat keeps the Earth warm enough to support life. However, excessive greenhouse gases due to human activities can lead to global warming and climate change.
9. Prepare a brief speech on global warming that you have to make in your class.
- “Global warming is a pressing issue that affects all of us. It refers to the rise in Earth’s average temperature due to the increased concentration of greenhouse gases in the atmosphere. These gases trap heat from the sun, leading to climate change, melting ice caps, rising sea levels, and extreme weather events. Human activities such as burning fossil fuels, deforestation, and industrial processes are major contributors. We must take immediate actions to reduce our carbon footprint, adopt renewable energy sources, and promote sustainable practices to combat global warming and protect our planet for future generations.”
10. Describe the threat to the beauty of the Taj Mahal.
- The Taj Mahal is threatened by air pollution from industrial and vehicular emissions. Sulfur dioxide and nitrogen oxides in the air react with moisture to form acid rain, which corrodes the marble. The deposition of particulate matter like soot and dust further discolors the monument, diminishing its beauty.
11. Why does the increased level of nutrients in the water affect the survival of aquatic organisms?
- Increased levels of nutrients, such as nitrogen and phosphorus, in water bodies can lead to eutrophication. This causes excessive growth of algae, which depletes oxygen in the water when they die and decompose, leading to hypoxic conditions. As a result, aquatic organisms, including fish, cannot survive due to the lack of oxygen.
Extended Learning – Activities and Projects
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?
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 can even think of starting one along with a few of your friends.
3. Organize 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.
