DAV Class 8 Science Chapter 20 Question Answer – Pollution of Water

The DAV Class 8 Science Solutions and DAV Class 8 Science Chapter 20 Question Answer – Pollution of Water are essential study tools for DAV public school students in Class 8.

DAV Class 8 Science Ch 20 Question Answer – Pollution of Water

DAV Class 8 Science Ch 20 Solutions – Pollution of Water

Something To Know

A. Fill in the blanks:

Question 1.
________ is a chemical method of purifying water.
Answer:
Chlorination

Question 2.
________ and ________ constitute agricultural waste.
Answer:
Fertilizers, pesticides

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

Question 4.
Water, that is safe for drinking, is called ________ water.
Answer:
potable

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

B. State True or False for the following statements:

1. A bad taste of water indicates the presence of pollutants in it.
Answer:
True

2. We should always bathe and wash clothes in rivers.
Answer:
False

3. Potable water can cause water borne diseases.
Answer:
False

4. We should always wash and clean our vehicles with tap water using a pipe.
Answer:
False

5. The “waste water’ produced by the industrial units, must be (appropriately) treated before it is discharged into rivers.
Answer:
True

C. Tick (✓) the correct option:

Question 1.
Domestic sewage, released into rivers, causes-
(a) growth of algae
(b) survival of aquatic life
(c) increase in oxygen
(d) killing of bacteria
Answer:
(a) growth of algae

Question 2.
Water, which is safe for drinking, is known as-
(a) potable water
(b) rain water
(c) sea water
(d) pond water
Answer:
(a) potable water

Question 3.
One of the methods, that can help in destroying harmful germs in water, is-
(a) filtering
(b) chlorination
(c) addition of fertilizers
(d) loading
Answer:
(b) chlorination

Question 4.
Suspended particles are made heavier by adding alum. This process is known as
(a) loading
(b) decantation
(c) chlorination
(d) filtration
Answer:
(a) loading

Question 5.
A method, that can help in conservation of water, is-
(a) using shower
(b) water dripping from leaking tap
(c) half flush
(d) water running for rinsing
Answer:
(c) half flush

D. Answer the following questions in brief:

Question 1.
State any two ways which can lead to contamination of water.
Answer:
Following can lead to contamination of water:

• Discharge of untreated sewage in river
• Leakage in pipeline

Question 2.
Give the meaning of the term “water pollutants’.
Answer:
The substances which pollute water are called water pollutants.

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

Question 4.
Name two chemicals that may help in purifying water.
Answer:
Alum, Bleaching powder

Question 5.
Name the kind of micro-organisms in water whose growth lead to a depletion of the oxygen dissolved in it.
Answer:
Growth of algae and bacteria

E. Answer the following questions:

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

Question 2.
Write, in brief, (i) one physical and (ii) one chemical method that can be used for Water purification’.
Answer:
(i) Physical method: Filtration
(ii) Chemical method: Chlorination

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

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

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.

Question 1.
State the values displayed by Ajay.
Answer:
Concern for environment.

Question 2.
Suggest some simple steps, that can be taken, to avoid wastage of water:
Answer:
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.

Question 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.
Answer:
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

Question 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.
Answer:
Do it yourself

Question 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.
Answer:
Do it yourself

Question 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.
Answer:
Do it yourself

DAV Class 8 Science Chapter 20 Solutions – Pollution of Water Important Questions and Answers

I. Fill in the blanks:

Question 1.
Boiling kills most of the________ in water.
Answer:
germs

Question 2.
________ tablets are added to water to kill germs.
Answer:
chlorine

Question 3.
Wastewater from households is called ________ .
Answer:
sewage

Question 4.
Wastewater from industries is called ________ .
Answer:
effluent

Question 5.
Proliferation of algae and bacteria uses up most of the ________ in water.
Answer:
oxygen

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

1. Water from any freshwater reservoir is fit for drinking.
Ans.
False

2. Groundwater is usually free from germs.
Ans.
True

3. Filtration removes germs from water.
Ans.
False

4. Alum tablets are used for killing germs in water.
Ans.
False

5. Shower bath is better than bucket bath for water conservation.
Ans.
False

III. Answer the following questions:

Question 1.
What are the various signs of water pollution?
Answer:
Signs of Water Pollution:

• Bad taste of drinking water.
• Offensive odour from lakes, rivers, and ocean beaches.
• Unchecked growth of aquatic weeds in waterbodies.
• Decrease in number of fish in fresh water, river water, sea water, etc.
• Oil and grease floating on water surface.

Question 2.
How does domestic sewage pollute water?
Answer:
Domestic sewage is often released into rivers. The sewage promotes the growth of algae and bacteria which use up a large amount of oxygen dissolved in water. This causes depletion of oxygen in water. This leads to death of aquatic animals.

Question 3.
What do you understand by chlorination?
Answer:
Chlorine powder or tablets are added to water which kills the germs in water. Adding chlorine to purify water is called chlorination.

Question 4.
What can be the harms of drinking contaminated water?
Answer:
Drinking contaminated water can lead to many water borne diseases like cholera, typhoid, jaundice, etc.

IV. Projects:

Question 1.
Make a flow chart to show different steps in water purification in a water treatment plant.
Answer:
Do it yourself.

Question 2.
Make a poster on ‘SAVE WATER’ and display it in your classroom.
Answer:
Do it yourself.