Pollution of Air and Water (NCERT Solutions, Class 8)

(1) What are the different ways in which water gets contaminated?

Ans- The different ways to contaminate water are listed below:-

(a) Throwing garbage into rivers.

(b) Throwing dead bodies into rivers.

(c) Untreated sewage directly flows in the Ganga.

(d) Industries discharge also goes into the river. Examples are oil refineries, paper factories, textiles and sugar mills, etc.

(e) Pesticides and the weedicides are used for the protection of the crops. These chemicals dissolve in water and washed into water bodies from the fields. They also seep into the ground to pollute ground water.

 (2) At an individual level, how can you help reduce air pollution?

Ans- Steps to control air pollution by an individual are listed below:-

(i) Use CNG or unleaded petrol for vehicles.

(ii) The solar energy, hydropower and wind energy should be used in place of fossil fuel.

(iii) More plants should be planted to lower the carbon dioxide in the atmosphere.

(3) Clear, transparent water is always fit for drinking. Comment.

Ans-  No, clear and transparent water is not always fit for drinking. It may possible that water has some water dissolving impurities and disease causing microorganisms. Therefore, it is always good to purify water before drinking.

(4) You are a member of the municipal body of your town.

Make a list of measures that would help your town to ensure supply of clean water to all its residents.

Ans- A list of measures that would help our town to ensure supply of clean water to all its residents is given below-

(a) Laws should be implemented strictly for the dispose off industrial water.

(b) Water treatment plant should be installed in all industrial areas.

(c) We should save water. Reduce, Reuse and recycle should be our Mantra.

(d)  Filtered water should be supply to all residents.

(e) Chlorination should be done regular basis.

(5) Explain the differences between pure and polluted air.

Ans- Differences between pure and polluted air are tabulated below:-

Pure air Polluted Air
Do not contain dangerous gases. Contains dangerous gases.
Do not cause diseases to humans. Cause diseases to humans.
Greenhouse effect works properly. Green house effet works adversely.
Do not cause global warming. Cause global warming.

(6) Explain circumstances leading to acid rain. How does acid rain affect us?

Ans- Pollutants like sulphur dioxide and nitrogen dioxide react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. The acid is drop down with rain. This process is known as acidic rain.

Effects of acid rain –

(i) The acidic rain corrodes marble.

(ii) The acid rain damages the crop.

(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”Greenhouse effect” in your own words.

Ans- Greenhouse effect is a natural process in which radiation from the sun rays fall on the atmosphere of the Earth and a part of it is radiated back to space as heat by atmosphere. But, other part is absorbed by the earth’s surface. Now, earth heats up and released back radiation into atmosphere and space. The greenhouse gases which are present in the atmosphere absorbed reflected back radiation (heat). Less part of it emitted back to space and large part is absorbed by the greenhouse gases. These gases do not allow the absorbed heat to go back in space. The trapped radiation or absorbed radiation is good for human life because it keeps earth warm and makes life possible on the earth. Hence, the trapping of radiations by the Earth’s atmosphere is known as greenhouse effect. It is very necessary for life on the Earth.

(9) Prepare a brief speech on global warming. You have to deliver the speech in your class.

Ans- The temperature of earth‘s atmosphere is gradually increasing, this is called global warming. It happens because of the increase of co2 in the atmosphere   and greenhouse effect. The co2 is released by the humans in breathing, burning coal and other fuels. Plants used carbon dioxide in photosynthesis. But co2  is increasing in atmosphere because of deforestation.Global warming affect atmosphere adversely. It can cause sea levels to rise. Glaciers are melting because of the global warming.

(10) Describe the threat to the beauty of the Taj Mahal.

Ans- The only threat of the Taj Mahal  is that the whiteness of Taj is going pale. Because the air pollutants produced by the industries located in and around Agra like rubber processing, automobile, chemicals and Mathura oil refinery. These are producing 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 acid is drop down with rain. This process is known as acidic rain. This acidic rain corrodes marble.

(11) Why does the increased level of nutrients in the water affect the survival of aquatic organisms?

Ans- The chemicals used in the fields and washed into ponds or water bodies from the fields are nutrients for the algae grow in water bodies. Once these algae die, they serve as food for decomposers like bacteria. A lot of oxygen in the water body gets used up. It results in a decrease in the oxygen level which may kill aquatic organisms.

Helping Topics

Pollution of air and water

Practice sheet, class 8

Wastewater Story


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