Chapter 20 | Pollution of Water | Class- 8 DAV Science Solutions

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In this post, we have discussed the solution of Science class 8 book Chapter 20 Pollution of Water.All the questions have been solved which may help students in their final and mid term examination.

DAV Class- 8 Pollution of Water Question and Answer

Something To Know

A. Fill in the blanks.

A. Fill in the blanks.

1. Chlorination is a chemical method of purifying water.

2. Fertilizers, and pesticides constitute agricultural waste.

3. The presence of domestic sewage, in water, promotes the growth of algae and bacteria which use up a lot of oxygen, present in the water.

4. Water, that is safe for drinking, is called potable water.

5. One of the purposes of purification of water is to remove the suspended impurities, present in it.


B. State True or False for the following statements.

1. A bad taste of water indicates the presence of pollutants in it.True
2. We should always bathe and wash clothes in rivers.
False
3. Potable water can cause water borne diseases.False
4. We should always wash and clean our vehicles with tap water using a pipe.False
5. The ‘waste water’ produced by the industrial units, must be (appropriately) treated before it is discharged into rivers.True


C. Tick (✓) the correct option.

1. Domestic sewage, released into rivers, causes— growth of algae survival of aquatic life increase in oxygen killing of bacteria

Ans. growth of algae

2. Water, which is safe for drinking, is known as— potable water rain water sea water pond water

Ans. potable water

3. One of the methods, that can help in destroying harmful germs in water, is— filtering chlorination addition of fertilizers loading

Ans. chlorination

4. Suspended particles are made heavier by adding alum. This process is known as loading decantation chlorination filtration

Ans. loading

5. A method, that can help in conservation of water, is— using shower water dripping from leaking tap half flush water running for rinsing

Ans. half flush


D. Answer the following questions in brief.

1.State any two ways which can lead to contamination of water.

Ans: Following can lead to contamination of water:

  • Discharge of untreated sewage in river.
  • Leakage in pipeline

2.Give the meaning of the term ‘water pollutants’.

Ans. The substances which pollute water are called water pollutants.

3.Name two of the main diseases that can be caused by drinking contaminated water. Ans. Cholera, Jaundice

4. Name two chemicals that may help in purifying water.

Ans. Alum, Bleaching powder

5. Name the kind of micro-organisms in water whose growth lead to a depletion of the oxygen dissolved in it.

Ans. Growth of algae and bacteria


E. Answer the following questions.

1. List the main parameters that need to be followed before water is supplied for drinking purposes.

Ans. The following parameters need to be followed before water is supplied for drinking purposes:

• It must be colourless and free from any odour.

• It must be free from suspended impurities.

• It should be tasteless.

• It must be free from microorganisms.

• It must be free from harmful chemicals.

2. Write, in brief, (i) one physical and (ii) one chemical method that can be used for ‘water purification’.

Ans. (i) Physical method: Filtration (ii) Chemical method: Chlorination

3. State the measures that must be taken to check water pollution by sewage.

Ans. Following measures must be taken to check water pollution by sewage: • Sewage must be churned by machines. • Treatment of water with alum. • Treatment of water by chlorination

4. Suggest some simple steps that can be taken to help in conserving water.

Ans. Following steps can be taken to conserve water: • Use bucket instead of shower for bathing. • Do not keep the tap running while brushing your teeth. • Immediately repair any leaking tap in the home. • Use water left after washing clothes and vegetables for mopping and for washing your vehicles.

Value-Based Questions

Ajay and Amit are good friends. One day when Ajay went to Amit’s home, he noticed that some of the taps, in the kitchen and bathroom were leaking. Ajay discussed this with Amit and explained to him the necessity of avoiding the wastage of water. He also talked to his father and gave Amit the mobile number of the plumber who could repair their leaking taps. Amit promised that he would request his parents to do the needful at the very earliest.

1. State the values displayed by Ajay.

Ans. Concern for the Environment.

Suggest some simple steps, that can be taken, to avoid wastage of water:

Ans. Following steps can be taken to avoid wastage of water: • Use bucket instead of shower for bathing. • Do not keep the tap running while brushing your teeth. • Immediately repair any leaking tap in the home. • Use left out water after washing clothes and vegetables for mopping and for washing your vehicles. 3. Suggest a simple method to make an estimate of the amount of water wasted through a (slightly) leaking tap over a month. Try to find out the extent to which such ‘leaked and wasted’ water can meet the ‘daily water requirements of a single person. Ans. Keep a bucket under a leaking tap and find out how many bucket are filled in a day. This will give the monthly amount of wasted water.

SOMETHING TO DO

1. Visit the office of your nearest ‘Jal Board’ and learn about the measures that are taken to ensure supply of clean drinking water to all the residents of the area. Prepare a project report on this.

Ans. Do it yourself

2. Survey your nearby locality and note down the details of the type of water purifiers, if any, used by different residents, for getting clean and safe drinking water. Present your findings on an appropriate bar chart.

Ans. Do it yourself

3. Visit your local doctor, or nearby health centre, to know about the common water borne diseases in the community. Find out the details of the steps, or measures, that are being taken by the government, as well as non-government organizations to minimize the occurrence of these diseases.

Ans. Do it yourself

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