DAV Class 8 Science Chapter 19 Question Answer – Pollution of Air

The DAV Class 8 Science Solutions and DAV Class 8 Science Chapter 19 Question Answer – Pollution of Air are essential study tools for DAV public school students in Class 8.

DAV Class 8 Science Ch 19 Question Answer – Pollution of Air

DAV Class 8 Science Ch 19 Solutions – Pollution of Air

Something To Know

A. Fill in the blanks:

Question 1.
________ and ________ gases dissolve in water to form acid rain.
Answer:
Nitrogen oxide, sulphur oxide

Question 2.
The phenomenon of corrosion of marbles of the monument, by acid rain, is called ________ .
Answer:
marble cancer

Question 3.
________ and ________ are two of the main greenhouse gases.
Answer:
carbon dioxide, methane

Question 4.
The phenomenon, of likely increase in earth’s average temperature (due to increase in the amount of greenhouse gases), is known as ________ .
Answer:
global warming

B. State true or false for the following statements:

1. Burning of fossil fuels is one of the many causes of air pollution.
Answer:
True

2. High concentration of nitrogen dioxide, in the atmosphere, can result in respiratory problems.
Answer:
True

3. The ultraviolet rays of the sun get absorbed mainly by the oxygen present in the atmosphere.
Answer:
False

4. Acid rain does not corrode metals.
Answer:
False

5. Sulphur dioxide is one of the ‘greenhouse gases’.
Answer:
False

C. Tick (✓) the correct option:

Question 1.
Which of the following is responsible for depletion of ozone layer?
(a) Smog
(b) Nitrogen dioxide
(c) Carbon monoxide
(d) Chlorofluorocarbon
Answer:
(d) Chlorofluorocarbon

Question 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
Answer:
(b) Global warming

Question 3.
The main gases, that trap the solar heat radiations after their reflection from the earth, are-
(a) Methane, carbon monoxide, chlorofluorocarbon
(b) Carbon dioxide, methane, water vapours
(c) Carbon monoxide, nitrogen dioxide and chlorofluorocarbons, water vapours
(d) Carbon monoxide, methane, nitrogen dioxide, water vapours
Answer:
(b) Carbon dioxide, methane, water vapours

Question 4.
Taj Mahal, at Agra, may get damaged if its surrounding atmosphere contains more of-
(a) Sulphur dioxide
(b) Oxygen
(c) Nitrogen
(d) Hydrogen
Answer:
(a) Sulphur dioxide

Question 5.
Smoke combines with water vapours and dust particles, in the presence of sunlight, to form-
(a) Snow
(b) Fog
(c) Smog
(d) Dew
Answer:
(c) Smog

D. Answer the following questions in brief:

Question 1.
Define the term ‘pollutant’.
Answer:
Any substance, present in the environment in proportions greater than its natural abundance, and causing harmful effects, is called a pollutant.

Question 2.
State two causes of air pollution.
Answer:
Two causes of air pollution are as follows:

• Excessive burning of fossil fuels.
• Smoke from factories and vehicles.

Question 3.
How is carboxy haemoglobin formed?
Answer:
Carbon monoxide combines with haemoglobin to form carboxy haemoglobin.

Question 4.
State the harmful effects of chlorofluorocarbons.
Answer:
Depletion of ozone layer

Question 5.
Suggest any three measures that can help to check global warming.
Answer:
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:

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

Question 2.
Write a short note on ‘acid rain’.
Answer:
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.

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

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

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

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.

Question 1.
Do you agree with Ram’s suggestion that the policeman should wear a mask during his duty hours?
Answer:
Yes.

Question 2.
Name the main pollutant produced by combustion of petrol/gasoline in automobiles.
Answer:
Carbon dioxide, carbon monoxide

Question 3.
State the values exhibited by Ram.
Answer:
Concern for others

Something To Do

Question 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.
Answer:
Do it yourself.

Question 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.
Answer:
Do it yourself.

Question 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’.
Answer:
Do it yourself.

DAV Class 8 Science Chapter 19 Solutions – Pollution of Air Important Questions and Answers

I. Fill in the blanks:

Question 1.
Methane is a potential ________ gas.
Answer:
Greenhouse

Question 2.
Coal and petroleum are examples of ________ fuels.
Answer:
Fossil

Question 3.
Solar energy is an example of ________source of energy.
Answer:
Alternate

Question 4.
The stratosphere is composed of ________ gas.
Answer:
Ozone

Question 5.
Planting more trees can prevent ________ pollution.
Answer:
Air

II. Write ‘T’ for true and *F’ for false:

Question 1.
Carbon monoxide is less dangerous than carbon dioxide.
Answer:
False

2. Nitrogen oxide can result in acid rain.
Answer:
True

3. Taj Mahal has lost its sheen because of acid rain.
Answer:
True

4. Burning of biogas does not create air pollution.
Answer:
False

5. Nuclear energy is a clean energy.
Answer:
True

III. Answer the following questions:

Question 1.
What is air pollution?
Answer:
When air is contaminated by unwanted substances which have harmful effects on the living and non-living, it is called air pollution.

Question 2.
What are the harmful effects of carbon monoxide?
Answer:
Harmful effects of carbon monoxide:

• Carbon monoxide is a highly toxic gas. If it is inhaled, it can result in death of a person.
• A high concentration of carbon monoxide in air affects the growth of plants causing leaf drop.

Question 3.
What are the harmful effects of nitrogen dioxide?
Answer:
Harmful effects of nitrogen dioxide:

• High concentration of nitrogen dioxide results in retardation of photosynthetic activity in plants and thus causes retardation of plants.
• It causes respiratory problems in human beings.

Question 4.
What is the full form of CFC?
Answer:
Chlorofluorocarbon

Question 5.
What are the various causes of greenhouse effect?
Answer:
Causes of Greenhouse Effect:

• Burning of fossil fuels release carbon dioxide gas into the atmosphere.
• Increased deforestation causes imbalance in the concentration of carbon dioxide in the atmosphere.

.

Question 6.
What are the consequences of global warming?
Answer:
Consequences of global warming:
Glaciers will melt at a higher rate and this will lead to rise in the sea level; resulting in floods and loss of life.
Warming of atmosphere often leads to forest fires which have become very common over the years.

IV. Projects:

Question 1.
Make a poster on ‘AIR POLLUTION’ and display it in your classroom.
Answer:
Do it yourself

Question 2.
Make a list of changes in your lifestyle which you can make to prevent air pollution.
Answer:
Some of the changes can be as follows:
Use bicycle to go to school.
Ask your parents to buy a solar cooker.
For short distance commute, prefer walking than using an automobile.