RBSE Class 8 Science Important Questions Chapter 18 Pollution of Air and Water

Rajasthan Board RBSE Class 8 Science Important Questions Chapter 18 Pollution of Air and Water Questions and Answers.

RBSE Class 8 Science Chapter 18 Important QuestionsPollution of Air and Water

Objective Questions

Question 1.    
The gas present in maximum amount in the atmosphere is:
(a) Oxygen 
(b) Nitrogen 
(c) Carbon - dioxide 
(d) Methane
Answer:
(b) Nitrogen 

Question 2.    
The gas which decreases the oxygen carrying capacity of blood is:
(a) Carbon di - oxide
(b) Carbon mono - oxide
(c) Water vapour
(d) Ozone gas
Answer:
(b) Carbon mono - oxide

Question 3.    
The factor responsible for depletion of ozone layer is:
(a) Chlorofluoro carbon
(b) Nitrogen dioxide
(c) Fluorene
(d) Carbon mono - oxide
Answer:
(a) Chlorofluoro carbon

Question 4.    
The chemical generally used for the purification of water is:
(a) Nitrogen gas 
(b) Bleaching Powder 
(c) Banking soda 
(d) Potash
Answer:
(b) Bleaching Powder 

Question 5.    
The disease which occurs due to use of polluted water is:
(a) Cholera 
(b) Typhoid 
(c) Jaundice 
(d) All of the above 
Answer:
(d) All of the above 

Fill in the blanks 

1. ........................... are the substances which contaminate air and water.
Answer:
pollutants

2. The increase in the average temperature of atmosphere is called ...........................
Answer:
global warming

3. The amount of .......................... is approximately 21% in air.
Answer:
oxygen 

True/False

Mark T for True and F for False in the following statements.

1. Pollutants are the substances which contaminate air and water.
Answer:
True

2. Clear and transparent water is always fit for drinking.
Answer:
False

3. Oxygen gas is responsible for green house effect.
Answer:
False

4. Gangotri glacier in the Himalayas has started melting because of global warming.
Answer:
True

Match the words given in 'Column-A' with 'Column-B'

Question 1.    

Column-A	Column-B
(i) Acid rain	(a) Carbon dioxide
(ii) Global wanning	(b) Nitrogen dioxide
(iii) Ozone depletion	(c) Chlorofluoro carbon
(iv) Water pollution	(d) Arsenic

Answer:

Column-A	Column-B
(i) Acid rain	(b) Nitrogen dioxide
(ii) Global wanning	(a) Carbon dioxide
(iii) Ozone depletion	(c) Chlorofluoro carbon
(iv) Water pollution	(d) Arsenic

Question 2.    

Column-A	Column-B
(i) Pollutant	(a) Rise in earth's average temperature
(ii) Chlorination	(b) Clean and drinking water
(iii) Potable water	(c) Contaminates air and water
(iv) Global warming	(d) Method of purifying water

Answer:

Column-A	Column-B
(i) Pollutant	(c) Contaminates air and water
(ii) Chlorination	(d) Method of purifying water
(iii) Potable water	(b) Clean and drinking water
(iv) Global warming	(a) Rise in earth's average temperature

Very Short Answer Type Questions

Question 1. 
How is the smog formed?
Answer:
Smog is made up of smoke and fog. Smoke contains oxides of nitrogen which combine with other air pollutants and fog to form smog. 

Question 2. 
Which pollutants are produced by the burning of fuel in automobiles?
Answer:
Carbon mono oxide, carbon dioxide and oxides of nitrogen are produced by the burning of fuel in automobiles.

Question 3. 
Which polluted particles are emitted by Mathura oil refinary?
Answer:
Soot particles are emitted by mathura oil refinery.

Question 4. 
What is the effect of soot particles on Taj Mahal?
Answer:
Soot particles have contributed towards yellowing the marble.

Question 5. 
Write the names of three green house effect gases.
Answer:

• Methane 
• Carbon dioxide 
• Nitrous oxide

Question 6. 
What is meant by water pollutants? 
Answer:
The substances which contaminate water are called water pollutants. Sewage disposal, poisonous chemicals are water pollutants.

Question 7. 
Which plan was launched to save the river Ganga?
Answer:
The Ganga action plan was launched in 1985 to save the river Ganga.

Question 8. 
What is the effect of releasing hot water in water bodies?
Answer:
Hot water raises the temperature of the water body which kills plants and animals present in it, creates water pollution.

Question 9. 
What is the main Mantra to save water? 
Answer:
Reduce, reuse and recycle is the main mantra to save water.

Question 10. 
Which metal pollutant is present in the smoke of automobiles?
Answer:
Lead.

Short Answer Type Questions

Question 1. 
When pesticides and weedicides used to protect crops, reach in pounds, how do they affect aquatic organisms? Explain.
Answer:
Pesticides and weedicides used to protect crops in fields, dissolve in water and are washed into water bodies from the fields. Due to this algae is grown because chemicals are present in pesticides and weedicides are helpful in the growth of algae. Once these algae die, then quantity of bacteria increases, which decrease the oxygen level which may kill aquatic organisms. So these show dangerous affect on aquatic organisms.

Question 2. 
Explain smog.
Answer:
Nitrogen oxide present in smoke forms smog by the combination of air pollutants and fog. It is present in the atmosphere in the form of thick layer. Smog causes breathing difficulties such as asthma, cough and wheezing in children.

Question 3. 
Write the complete name of C.F.C. Where is it used? Write one demerit of it. 
Answer:
The complete name of CFC is Chloro Fluoro Carbons. It is used in refrigerators, air conditioners and aerosol sprays. CFC damages the ozone layer of the atmosphere, which is called ozone depletion. More ultra violet rays are reached up to earth due to ozone depletion which cause skin cancer.

Question 4. 
Mention three human activities which help in air pollution?
Answer:
Reasons for Air Pollution:

• Unlimited cutting of trees.
• Establishment of industrial units.
• Excess use of fossil fuels (Petroleum products and coal)

Question 5. 
What do you mean by ozone depletion? What are the harmful effects of it?
Answer:
The atmosphere around our earth is covered with thick layer of ozone gas. Ozone layer stops the ultra violet rays of sun to reach on earth. These rays are harmful for our health. CFC used in refrigerators, air conditioners and aerosol sprays, damages the ozone layer which is called ozone depletion. More ultra violet rays are reached up to earth due to ozone depletion which cause skin cancer.

Question 6. 
What is acid rain? Mention the harmful effect of it?
Answer:
When the amount of oxides of nitrogen and sulphur is increased, these gases react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. The acids drop down with rain, making the rain acidic. This is called acid rain. Acid rain corrodes the hitorical monuments, buildings and statues. Soil also becomes acidic so fertility of 'soil decreases due to acid rain and ultimately it becomes useless.

Question 7. 
What are the main measures for the prevention of air pollution?
Answer:
The main measures for the prevention of air pollution are as follows:

1. Use of better stoves in which complete combustion occurs and form comparatively less harmful water vapours and less carbon - dioxide.
2. Use of alternate fuel like solar energy and water energy.
3. Maintenance of motor engines timely.
4. Planting more trees near roads and houses and Van Mahotsav should be meaningful.
5. Use of long chimney with filter.
6. Use of renewable energy source like unleaded petrol and CNG

Question 8. 
How does the nature balance between carbon dioxide and oxygen?
Answer:
Oxygen is used and carbon dioxide is released in atmosphere during respiration of plants and animals, decay of dead plants and animals and combustion of fuels. Although plants use carbon - dioxide and give oxygen dining photo synthesis. So due to natural process the oxygen and carbon - dioxide are balanced in the atmosphere.

Question 9. 
How does the sea level increase due to global warming?
Answer:
The increase in the temperature due to global warming melts the polar glaciers which leads to a rise in the sea level, causing floods in the coastal areas and it will harm cities and ecological system like marshy places.

Question 10. 
Mention four effects of polluted water.
Answer:

1. Excess of aquatic plants results decrease in the oxygen in water bodies at night. This results the death of small fishes and other aquatic animals.
2. Drinking of polluted water causes diseases of stomach, cholera, typhoid and jaundice.
3. Oil pollution decreases the oxygen level for fishes and they are killed in a large number.
4. Due to drinking of polluted water having viruses, bacteria and blue green algae cause many diseases in domesticated animals.

Question 11. 
Mention four measures to control the water pollution?
Answer:

1. Sewage disposal, detergents and water from houses should not be washed in rivers and ponds near the city but it should be washed away from population with the help of drainage system.
2. Poisonous residual substance and hot water should not be washed away in rivers and seas.
3. The residues of industries should be washed away in rivers only after treatment.
4. One should take care while using insectisides that the water of that agriculture land should not flow in water bodies, which is used for drinking.

Question 12. 
What are the three properties of potable water?
Answer:

• It should be transparent, colourless and odour less.
• Sufficient amount of oxygen should be dissolved in it.
• It should be free from chemicals and bacteria.

Question 13. 
How is the safe water prepared for drinking? Explain.
Answer:
The following processes should be followed to prepare safe water for drinking:

• Filter the water for which a popular house hold candle type filters is used nowadays.
• Water should be boiled for obtaining safe drinking water free from bacteria.
• Water should be purified by chlorination for which bleaching powder can be used.

Question 14. 
‘Water is an important natural resource’. What measures can be taken to save it?
Answer:
It is true that water is a precious natural resource. It should be conserved by using it wisely. For which following measures can be taken:

1. During the use of water in daily life a little alertness can control the wastages of water. While brushing teeth or bathing do not leave the tap running because it may waste thousand litres of water.
2. During the use of water we should always remember the main mantra which includes reduce, reuse and recycle.
3. The water used for washing of vegetables in homes can be reused for plants.
4. Rain water can be collected.

Essay Type Questions

Question 1. 
What do you mean by air pollution? Mention the Jiarmful effects of air pollution. 
Answer:
In air oxygen, nitrogen, carbon dioxide and other gases are present in a definite ratio. The imbalance position of ratio of these gases is called air pollution or when air is contaminated by unwanted substances which have a harmful effect on both the living and the non - living then it is called air pollution. The harmful effects of air pollution are as following:

1. Air pollution affects the respiratory system of animals and causes diseases like bronchitis asthma, lung cancer and pneumonia.
2. Ozone depletion occurs due to air pollution so ultraviolet rays of sun light reach the earth. They harm eyes and immune system and cause skin cancer.
3. Poisonous gas like carbon mono oxide reaches in our body and decreases the oxygen carrying capacity of blood.
4. Air pollution is also responsible for acid rain and global warming.

Question 2. 
Ganga is a sacred river but it is polluted, why? What measures can be taken to save the existence of it?
Answer:
We know that Ganga is one of the ten rivers of the world and existence of it is in danger. Because pollution of it is increasing continuously. The towns and cities through which the river flows, throws large quantity of garbage, untreated sewage, dead bodies and many other harmful things, are thrown directly into the river. In fact the river is ‘dead’ at many places where the pollution levels are so high that this water becomes poison for aquatic life.

Many industries discharge harmful chemicals into rivers and streams, causing pollution of water. Examples are oil refineries, paper factories, textile and sugar mills and chemical factories. These industries cause chemical contamination of water. The chemicals released include arsenic, lead and fluorides which lead to toxicity in plants and animals. These are also polluting the river Ganga.

Measures:
1. Regulations are made by government to prevent water pollution according to which industries are supposed to treat the waste product before discharging it into waters, but quite often the rules are not followed.

2. To save the river ganga, the Ganga action plan was launched in 1985. Under which it is banned to discharge undesirable substances into river. Actually every man should work with alertness to control the water pollution only then we can be in the capacity to stop it.