Chapter 19 | Pollution Of Air | Class- 8 DAV Science Solutions

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DAV Class- 8 Pollution of Air Question and Answer

Something To Know

A. Fill in the blanks.

Nitrogen_oxide and sulphur oxide gases dissolve in water to form acid rain.
The phenomenon of corrosion of marbles of the monument, by acid rain, is called marble cancer.
carbon dioxide and methane are two of the main greenhouse gases.
The phenomenon, of likely increase in earth’s average temperature (due to increase in the amount of greenhouse gases), is known as global_warming.

B. State True or False for the following statements.

Burning of fossil fuels is one of the many causes of air pollution.	True
High concentration of nitrogen dioxide, in the atmosphere, can result in respiratory problems.	True
The ultraviolet rays of the sun get absorbed mainly by the oxygen present in the atmosphere.	False
Acid rain does not corrode metals.	False
Sulphur dioxide is one of the ‘greenhouse gases’.	False

C. Tick (✓) the correct option.

1. Which of the following is responsible for depletion of ozone layer?

A.Smog B.Nitrogen dioxide C.Carbon monoxide D.Chlorofluorocarbon

Ans. Chlorofluorocarbon

2. An increase, in the amount of carbon dioxide and methane in the atmosphere, is likely to lead to—

A. Ozone depletion B.Global warming C. Acid rain D.Formation of more glaciers

Ans. Global warming

3. The main gases, that trap the solar heat radiations after their reflection from the earth, are—

Ans. Carbon dioxide, methane, water vapours

4. Taj Mahal, at Agra, may get damaged if its surrounding atmosphere contains more of— Sulphur dioxide Oxygen Nitrogen Hydrogen

Ans. Sulphur dioxide

5. Smoke combines with water vapours and dust particles, in the presence of sunlight, to form— Snow Fog Smog Dew

Ans. Smog

D. Answer the following questions in brief.

1.Define the term ‘pollutant’.

Ans. Any substance, present in the environment in proportions greater than its natural abundance, and causing harmful effects, is called a pollutant.

2. State two causes of air pollution.

Ans. Two causes of air pollution are as follows: • Excessive burning of fossil fuels. • Smoke from factories and vehicles.

3. How is carboxy haemoglobin formed? Ans. Carbon monoxide combines with haemoglobin to form carboxy haemoglobin.

4. State the harmful effects of chlorofluorocarbons.

Ans. Depletion of ozone layer

Suggest any three measures that can help to check global warming. Ans. Following measures can help to check global warming: • Reducing the use of fossil fuels. • Switching to cleaner fuels; like CNG. • Using public transport.

E. Answer the following questions.

1.Give the meaning of the term ‘smog’. List its harmful effects.

Ans. When smoke (containing oxides of nitrogen) combines with other air pollutants and fog, it forms smog. Following are the harmful effects of smog: • Respiratory diseases. • Poor visibility for pilots and for drivers. • Affects the normal functioning of plants.

2. Write a short note on ‘acid rain’.

Ans. Oxides of nitrogen and sulphur mix with water form acid rain. Acid rain is harmful for living beings. It also corrodes the outer layer of buildings and monuments. Taj Mahal has become pale due to acid rain.

3. List the main causes of increase in concentration of greenhouse gases in the atmosphere.

Ans. Following are the main causes of increase in concentration of greenhouse gases in the atmosphere: • Excess use of fossil fuels • Increase in cattle population • Large scale deforestation

4. State the likely consequences of an increase in the ‘greenhouse effect’.

Ans. Following are the consequences of increase in greenhouse effect: • Global warming results in increase in temperature on earth. • Melting of glaciers which may result in a rise in sea level around the world. • Warming of atmosphere often results in forest fires.

5. Write any five methods that can help to control air pollution.

Ans. Following methods can help to control air pollution: • Reduce the use of fossil fuels. • Switch over to cleaner fuels; like CNG and PNG. • Increase the use of solar energy and wind energy. • Increase the use of hydel energy. • Plant more trees. • Stop deforestation.

Value-Based Questions

1.Ram was walking to his home after school. He noticed that the traffic policeman, on duty at a congested crossing, was not wearing a mask. He immediately went near him and advised the traffic policeman to wear the mask preferably throughout his duty hours but definitely during the peak hours of traffic. The policeman thanked him for his suggestion. 1. Do you agree with Ram’s suggestion that the policeman should wear a mask during his duty hours?

Ans. Yes.

2.Name the main pollutant produced by combustion of petrol/gasoline in automobiles. Ans. Carbon dioxide, carbon monoxide 3. State the values exhibited by Ram.

Ans. Concern for others

SOMETHING TO DO

1. Visit your nearby petrol pump and observe the process of conducting ‘pollution check’ for the petrol and diesel cars. Make a project report, on the basis of your observations, highlighting following points: (a) Average number of vehicles checked per month. (b) Pollutants checked for. (c) Permissible level of emission of different polluting gases. (d) The pollutants from vehicles, that act as major source of air pollution.

Ans. Do it yourself.

2. Organise a trip to an industrial area. Talk to the people residing near that area regarding the practical problems they face due to the smoke and emissions by the factories. Ans. Do it yourself. 3. Global warming is a matter of worldwide concern. Countries have joined together to find solutions to this problem. Collect information about any two international measures that aim at addressing the issue of ‘global warming’.