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Pollution of Air and Water - Class 8 Science Textbook Solution

Class 8 Science Chapter 18 Pollution of Air and Water
Pollution of Air and Water Textbook s and Answers

1. What are the different ways in which water gets contaminated?
Water gets contaminated in the following ways:
•    Water gets, contaminated when the sewage is disposed of in rivers.
•    Chemicals which are harmful and poisonous are thrown into water resources by various industrial units.
•    Harmful chemicals used in the agricultural process get mixed with groundwater making it unfit for consumption.
•    The breeding of microorganisms in water makes water polluted.
2. At an individual level, how can you help reduce air pollution?
To reduce air pollution:
•    We should use fuels like CNG etc. instead of petrol and diesel.
•    We should use solar energy, water energy, and wind energy instead of fossil fuels.
•    We can plant trees and nurture the ones already present in the neighbourhood.
•    We can take part in Van Mahotsava actively and effectively every year and motivate people about the importance of the plantation of trees.
•    We can also educate the people against burning dried leaves and plants and advise them to put them in a compost pit.
3. Clear, transparent water is always fit for drinking. Comment.
Clear, transparent water is not always fit for drinking water because it may have disease-carrying microorganisms and dissolved impurities. So, water must be purified before drinking by boiling or by the filter.
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.
Measures that would help our town to ensure the supply of water to all its residents are:
•    All residents must get water as per their needs. For this, I will have meetings with the officials of the Jal Board from time to time.
•    I will get the water tested so that all residents get clean water.
•    The pipes from where leakage of water takes place will be repaired immediately.
•    It will be ensured that drinking water pipes and wastewater pipes should be separate and not near each other.
•    The people who steal water will be punished.
•    Water tanks will be arrayed to meet any emergency.
5. Explain the differences between pure air and polluted air.

6. Explain circumstances leading to acid rain. How does acid rain affect us?
The industries like rubber processing, automobile, chemicals, Mathura oil refinery produce pollutants like sulphur dioxide and nitrogen dioxide. These gases react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. The acids drop down with rain, making the rain acidic. This is called acid rain. Acid rain affects us in the following ways:
•    It corrodes buildings and statues, specially made with marble and stone e.g., Taj Mahal in Agra.
•    It damages plants by destroying their leaves.
•    It causes extensive harm to the soil by making it acidic.
•    It causes harm to forests, wildlife, and other forms of life.
•    It contaminates the water lakes and streams thereby killing the aquatic life (fishes etc) in it.
•    It affects human health.
7. Which of the following is not a greenhouse gas?
(a) Carbon dioxide
(b) Sulphur dioxide
(c) Methane
(d) Nitrogen
(d) Nitrogen
8. Describe the ‘Green House Effect’ in your own words.
The greenhouse effect means warming the environment. When the rays of the sun reach the earth, some of the heat is absorbed by the earth. The rest of it is reflected back by the earth. Some of the heat is trapped by the environment of the earth. This causes warming of the environment, which is necessary for sustaining life. This trapping of the heat is called the greenhouse effect.
9. Prepare a brief speech on global warming. You have to deliver the speech to your class.
Industrialization, deforestation, various human activities, and the use of fossil fuels have to lead to an increase in the amount of CO2 in the air. CO2 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. This is called global warming.
Global warming can create the melting of icebergs, resulting in rising in the sea level causing the flooding of many coastal areas. Global warming can also bring about climatic changes. It could also result in wide-ranging effects ‘on rainfall patterns, agriculture, forests, plants, and animals.
The Gangotri glaciers in the Himalayas have started melting because of global warming. Global warming has become a major concern for governments worldwide. Many countries have reached an agreement to reduce the emission of greenhouse gases. The Kyoto Protocol is one such agreement.
10. Describe the threat to the beauty of the Taj Mahal.
The Taj Mahal is made of white marble; which is getting affected adversely due to industrial pollutants. Nearby Agra, the Mathura oil refinery is situated, which is emitting pollutants like sulphur dioxide and nitrogen dioxide. These gases react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. These acids come down with the rain, making the rain acidic. This is called acid rain. This acid rain has resulted in the corrosion of the marble of the Taj Mahal. The suspended particulate matter, emitted by the Mathura oil refinery, has also contributed to the yellowing of the marble of the Taj Mahal.
The supreme court has taken several steps to save the Taj. It has ordered industries to switch to cleaner fuels like CNG (Compressed Natural Gas) and LPG (Liquefied Petroleum Gas). Moreover, the automobiles should switch over to unleaded petrol in the Taj zone.
11. Why does the increased level of nutrients in the water affect the survival of aquatic organisms?
Agriculture relies on the use of chemical fertilizers to improve crop yields. All these chemicals dissolve in water and run into water bodies from the fields. These seep into the ground and pollute the groundwater. A lot of algae in the ponds grow and keep the ponds green. This is caused due to excessive quantities of chemicals like nitrates and phosphates which are present in fertilizers. These act as nutrients for algae to flourish.
When these algae die, they serve as food for decomposers as bacteria algae die, they serve as food for decomposers like bacteria. They use up a lot of oxygen. This results in a decrease in the oxygen level which is harmful to the survival of other aquatic organisms.

Pollution of Air and Water Additional s and Answers
1. What is air?
Air is a mixture of gases. By volume, about 78% of this mixture is nitrogen and about 21% is oxygen. Carbon dioxide, argon methane, ozone, and water vapour are also present in very small quantities.
2. What are air pollutants?
The substance which contaminates the air is called air pollutants.
3. How is air pollution caused?
Air pollution is caused by gases, such as sulphur dioxide, carbon monoxide, and nitrogen oxides which are released into the atmosphere by the burning of fossil fuel exhausts from automobiles and industries.
4. Why Taj Mahal in Agra has become a matter of concern?
Taj Mahal has become a matter of concern because pollutants in the air are discolouring its white colour. The industries located in and around Agra-like rubber processing automobile, chemicals, and especially the Mathura oil refinery are responsible for it.
5. What is acid rain?
Acid rain is the rain in which pollutants like sulphur dioxide and nitrogen oxide dissolve in the rainwater and forms sulphuric acid and nitric acid.
6. What is the Greenhouse effect?
The sun sends its rays to the earth. Some of these rays are absorbed by the earth and some radiations are reflected back by the earth. Thus reflected radiations are not allowed to leave the earth’s atmosphere completely. Some of these radiations are trapped by the earth’s atmosphere and this is called the greenhouse effect.
7. Why has the greenhouse effect become a threat to life?
The greenhouse effect has become a threat to life because the gas responsible for it i.e., CO2 is increasing due to this the average temperature of the atmosphere is increasing.
8. Would it be a better option to put them in a compost pit rather than burning them?
Yes, the burning of leaves produces a lot of smoke, which produces air pollution. But putting leaves in a compost pit does not cause air pollution. Instead, it produces manures which increase the fertility of the soil.
9. What are water pollutants?
Whenever, harmful substances such as sewage, toxic chemicals, silt, etc., get mixed with water, the water becomes polluted. The substances that pollute water are called water pollutants.
10. What is WWF?
WWF is World Wide Fund for nature.
11. What is Potable Water?
Water which is suitable for drinking is called potable water.
12. What is the mantra to save water?
‘Reduce’, ‘Reuse’ and Recycle is the mantra to save water.

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