RBSE Solutions for Class 8 Science Chapter 18 Pollution of Air and Water

Rajasthan Board RBSE Solutions for Class 8 Science Chapter 18 Pollution of Air and Water Textbook Exercise Questions and Answers.

RBSE Class 8 Science Solutions Chapter 18 Pollution of Air and Water

RBSE Class 8 Science Pollution of Air and Water InText Questions and Answers

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Question 1. 
I am reminded of the chapter on crops. I wonder whether acid rain affects the soil and, plants also!
Answer:
Yes, acid rain affects the soil and plants. Soil is polluted by it and it shows many harmful effects on plants.

Question 2. 
But how does CO₂ content rise in the atmosphere and become excessive? 
Answer:
There are so many reasons for the increase in the amount of CO₂ in atmosphere. CO₂ is continuously being released inatmosphere due to human activities like industrialisation and smoke of vehicles, etc. On the other hand area under forest is decreasing so the number of trees which consume CO₂ is reduced so the CO₂ become excessive in atmosphere.

RBSE Class 8 Science Pollution of Air and Water Textbook Questions and Answers     

Question 1. 
What are the different ways in which water gets contaminated?
Answer:
Water is contaminated by following methods:

1. At the time of extracting oil, sea water is polluted by petroleum seeping into the sea and by the transportation of ships.
2. The waste released from nuclear reactors plants also pollute water.
3. Many industries discharge harmful chemicals into rivers and streams causing the pollution of water.
4. The pesticides used for the protection of crops dissolve in water and are washed into water bodies from the fields. So lots of algae grow in water bodies from the fields.
5. These chemicals are helpful for the growth of algae. When these algae die, the amount of bacteria increases, this results in a decrease in the oxygen level which may kill aquatic organism causing the water pollution.
6. The untreated sewage washed directly into water is also a cause of the water pollution.
7. The hot water released from power plants and industries is also the reason for contamination of water.

Question 2. 
At an individual level, how can you help reduce air pollution?
Or
Write any four suggestions to overcome the air pollution.
Answer:
At an individual level we can reduce the air pollution by the following solutions:

1. By planting trees near the houses.
2. By the use of public transport.
3. Less use of personal vehicles. Use of diesel CNG or unleaded petrol.
4. Inhibition of burning of tyres and garbage of the houses.

Question 3. 
Clear, transparent water is always fit for drinking. Comment.
Answer:
This statement is not correct that clear, transparent water is always fit for drinking, because it may have pathogenic microorganisms and dissolved impurities.

So drinking of this water may be the reason of illness. So we should always drink potable water. If complete knowledge of quality of water is not available, use it after boiling or filtering.

Question 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. 
Answer:
If I were the member of the municipal body of our town I would organise meeting with water board to ensure the supply of clean water and the sample of water would be tested in private labs also. I would persue for necessary action by writing the letter to water board if required.

In addition to this checking of potable water pipes would be performed from time to time so that contaminated water would not reach homes. Except this, water tanks of the area would be checked and cleaned from time to time.

Question 5. 
Explain the differences between pure air and polluted air.
Answer:

Question 6. 
Explain circumstances leading to acid rain. How does acid rain affect us?
Answer:
Acid Rain:
The gases like sulphur - dioxide and nitrogen dioxide released from different industries react with water vapour present in the atmosphere to form sulphuric acid and nitric acid. This acids drop down with rain making the rain acidic. It is called acid rain. 

Acid rain affects us in the following manner:

1. When this acid raindrops down on historical monuments, the acid present in these rain drops corrodes the marble of the monument by a chemical reaction to it. So the Taj Mahal made of marble is also being destroyed.
2. Acid rain increases the acidity of soil which destroys the fertility of soil and the growth of crops.
3. Acid rain also pollutes water.

Question 7. 
Which of the following is not a greenhouse gas?
(a) Carbon dioxide    
(b) Sulphur dioxide
(c) Methane    
(d) Nitrogen
Answer:
(d) Nitrogen

Question 8. 
Describe the 'Green house effect' in your own words.
Answer:
Ultra violet rays present in the sunlight reaches earth and warm the earth surface and other objects. A part of radiation is reflected back into space. A part of the reflected radiation is trapped by carbon dioxide present in the atmosphere.

The trapped radiations further warm the earth's atmosphere. The warming of earth's atmosphere by radiation is called green house effect.

Question 9. 
Prepare a brief speech on global warming. You have to deliver the speech in your class.
Answer:
Global Warming:
The average temperature of the atmosphere is gradually increasing. This is called global warming. The reason for this is gradual increase in the level of CO₂, methane gases, etc. Industrialisation, smoke released from vehicles and deforestation is mainly responsible for it.

Gangotri glacier in the Himalayas has started melting because of global warming and many areas of earth are submerged under water. According to a report temperature may increase upto 2°C in the end of century, which is a dangerous level.

Many countries have reached an agreement to reduce the emission of greenhouse gases. The Kyoto Protocol under the United Nations Organisation is one such agreement.

On the individual level we should plant more trees to limitise the effect of global warming. The unleaded petrol and alternative energy, etc. should be used and public awareness programmes should be demonstrated to inspire people.

Question 10. 
Describe the threat to the beauty of the Taj Mahal.
Answer:
The beauty of the Taj Mahal is unique in the world and it has a place in the seven wonders of the world but the increased pollution has created a problem for this precious monument.

The industries located around the Taj Mahal like rubber processing, automobile, chemicals and especially the Mathura oil refinery create acid rain by mixing polluted gases with rain water. 

Acid fain corrodes the marble of the Taj Mahal and contributes towards yellowing it. The Supreme Court has taken several steps to save the Taj.

It has ordered the industries to switch to cleaner fuels like CNG (Compressed Natural Gas) and- LPG (Liquified Petroleum Gas). Moreover the automobiles should switch over to unleaded petrol in the Taj Zone.

Question 11. 
Why does the increased level of nutrients in the water affect the survival of aquatic organisms ?
Answer:
The increased level of nutrients (Nitrate, Phosphate) in the water affects the survival of aquatic organisms in the following manner: 
Nitrate is good nutrient for algae to flourish. So in presence of nitrate in water bodies the amount of algae increase rapidly and due to it the amount of dissolved oxygen in water of rivers, ponds and springs becomes very low which may kill aquatic organisms.