BASIC SCIENCE SOLUTION CLASS 8 CHAPTER 16 Pollution of Air and Water

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Exercise

 

A. Answer the following in not more than 20 words. 

1. What do you mean by polluted air or water? 

2. Mention any three observations that indicate that a given sample of water is polluted. 

3. What is chemical pollution of water?

4. Name six chemical pollutants of water. 

5. Name four water-borne diseases.

6. What do you mean by potable water? 

7. How is activated charcoal made and what is its role in the purification of water? 

8. What is bleaching powder used for in the purification of water?

B. Answer the following in not more than 40 words.

1. How does carbon monoxide affect us?

2. What is the advantage of using CNG in preference to petrol or diesel in automobiles 

3. Discuss three methods of preventing water pollution.

C. Answer the following in not more than 100 words.

1. Name three pollutants (except dust and soot) of air and mention their sources. 

2. Describe eutrophication. 

3. Describe an activity to show that alum helps the suspended particles of water to settle

D. Complete the following.

1....... is formed by the complete combustion of carbon.

2. Acid rain contains mainly and..... acids.

3. An increase in the CO, level in the air causes the...... effect. 4. Sculptures, monuments and buildings are...... by acid rain.

5. Ozonisation of water kills the...... in it and makes it rich in dissolved........

E. Choose the correct option in each of the following.

1. Which of the following affect(s) the ozone layer? 

(a) Carbon dioxide

(b) CFCs

(c) Soot

 (d) Dust

2. The ozone layer in our atmosphere protects us from the bad effects of

(a) the sun's ultraviolet rays

(b) carbon dioxide

(c) CFCs

(d) all of these

3. Which of the following is an oxygen-demanding waste?

(a) Pesticides

(b) Oil

(c) Grease 

(d) Domestic sewage

4. Which of the following is/are used for disinfecting water?

(a) Chlorine 

(b) Ozone

(c) Ultraviolet rays

(d) All of these

5. Reverse osmosis is used for the purification of

(a) air

(b) Ozone 

(c) air as well as water

(d) All of these

F. Match the columns.

A

(a) Oil spill

(b) Ceramic candles

(c) Alum

(d) Bleaching powder

(e) Typhoid

B

(i) helps the sedimentation of suspended particles 

(ii) a water-borne disease

(iii) reduces the transmission of light through water 

(iv) water filter

(v) disinfects water

Answer

A. 

1. Polluted air or water contains harmful substances beyond acceptable levels. 

2. Three observations indicating water pollution: foul smell, oil films, and discolored water. 

3. Chemical pollution of water is contamination by harmful chemicals such as pesticides, heavy metals, and solvents. 

4. Chemical pollutants of water include lead, mercury, pesticides, herbicides, solvents, and industrial chemicals. 

5. Water-borne diseases include cholera, typhoid, dysentery, and hepatitis A. 

6. Potable water is safe for human consumption. 

7. Activated charcoal is made by heating carbon-rich material and is used to remove impurities from water by adsorption. 

8. Bleaching powder is used to disinfect water by releasing chlorine. 

B. 

1. Carbon monoxide reduces the oxygen-carrying capacity of blood, leading to headaches, dizziness, and even death. 

2. CNG emits fewer pollutants and is more efficient than petrol or diesel. 

3. Methods of preventing water pollution include reducing chemical use, treating wastewater before discharge, and using eco-friendly products. 

C. 

1. Pollutants of air: Carbon monoxide (vehicles), sulfur dioxide (fossil fuels), nitrogen oxides (power plants and vehicles). 

2. Eutrophication is an increase in nutrients in water that leads to excessive plant growth, oxygen depletion, and fish die-offs. 

3. To show that alum helps suspended particles settle, mix dirty water with alum, stir, and observe the particles settling to the bottom. 

D. 

1. Carbon dioxide is formed by the complete combustion of carbon. 

2. Acid rain contains mainly sulfuric and nitric acids. 

3. An increase in the CO2 level in the air causes the greenhouse effect. 

4. Sculptures, monuments, and buildings are corroded by acid rain. 

5. Ozonisation of water kills the microorganisms in it and makes it rich in dissolved oxygen. 

E. 

1. (b) CFCs. 

2. (a) The sun's ultraviolet rays. 

3. (d) Domestic sewage. 

4. (d) All of these. 

5. (b) Water. 

F. 

(a) - (iv), (b) - (v), (c) - (i), (d) - (iii), (e) - (ii).

ThankYou


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