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Class 8 Science Chapter 18 Extra Questions and Answers Pollution of Air and Water
Extra Questions for Class 8 Science Chapter 18 Pollution of Air and Water with Answers
Pollution of Air and Water Class 8 Extra Questions Very Short Answer Type
Question 1.
Which monument in India is now one of the seven wonders of the world?
Answer:
It is Taj Mahal.
Question 2.
Why is the beauty of Taj Mahal threatened?
Answer:
Because of the air pollution in the area surrounding the Taj.
Question 3.
Name two sources of air pollutants.
Answer:
Factories and vehicles are the two prominent sources of air pollution.
Question 4.
Which gas is most responsible for global warming?
Answer:
C02 is most responsible for global warming.
Question 5.
Name the greenhouse gases.
Answer:
Carbon dioxide, methane, nitrous oxide, water vapour, etc. are called greenhouse gases.
Question 6.
Name the ambitious plan to save the river?
Answer:
It is called Ganga Action Plan.
Question 7.
What does untreated sewage thrown directly into rivers contain?
Answer:
Untreated sewage contains food- wastes, detergents and microorganisms.
Question 8.
What does water contaminated with sewage may contain?
Answer:
It contains bacteria, viruses, fungi and parasites.
Question 9.
What is potable water?
Answer:
Water which is suitable for drinking is called potable water.
Pollution of Air and Water Class 8 Extra Questions Short Answer Type 1
Question 1.
What is the impact of reducing quality of air and water on our lives?
Answer:
There is a great impact of reducing quality of air and water on our lives. The number of people suffering from various pollution-borne diseases is rising day by day.
Question 2.
State the constituents of air.
Answer:
Air consists of a mixture of gases. By volume about 78% of thik mixture is nitrogen and about 21% is oxygen. Carbon dioxide, argon, methane, ozone, water vapour are also present in very small quantity.
Question 3.
What is meant by air pollution?
Answer:
When the air is contaminated by unwanted substances which cause harmful effects on both the living and non-living components, it is referred to as air pollution.
Question 4.
What reduces visibility in air?
Answer:
Automobiles which burn diesel and petrol, produce tiny particles which remain suspended in air for long periods. They reduce visibility in air.
Question 5.
Are non-living things also affected by air pollution?
Answer:
Yes, the air pollution is affecting not only living beings, but also the non-living things. An example of this is discolouring the white marble of Taj Mahal due to air pollution. Similarly, many other buildings, monuments and statues are also getting affected.
Question 6.
Which industries are responsible for the yellowing of Taj in Agra?
Answer:
The industries located in and around Agra are rubber processing, automobiles, chemicals and especially the Mathura oil refinery have been responsible for the yellowing of Taj in Agra.
Question 7.
What are the reasons of water scarcity?
Answer:
Water is becoming scarce day by day due to increase in population, industries and agricultural activities.
Question 8.
How is water getting polluted?
Answer:
Whenever substances such as sewage, toxic chemicals, silt, etc., which are harmful to life, get mixed with water, the water becomes polluted.
Question 9.
What is the impact of putting chemical fertilizers in water?
Answer:
Putting chemical fertilizers in water leads to algae bloom, which increase toxicity of water. Again when they die, they are fed by decomposers like bacteria, which uses dissolved oxygen of water. Thus, survival of organism living in water become tough and they die out of stress.
Pollution of Air and Water Class 8 Extra Questions Short Answer Type 2
Question 1.
What is the thick fog-like layer in the atmosphere during winter? How is it formed?
Answer:
The thick fog like layer seen in the atmosphere especially in winter is smog. The smog is made up of smoke and fog. Oxides of nitrogen combine with other air pollutants and fog contributing to the formation of smog. It causes breathing difficulties such as asthma, cough and wheezing in children.
Question 2.
What are the directives of supreme court to control air pollution to save Taj?
Answer:
The supreme court has taken several steps to save the Taj Mahal from getting damaged by toxic chemicals.
(i) It has ordered the industries to switch to cleaner fuels like CNG (Compressed Natural Gas) and LPG (Liquefied Petroleum Gas).
(ii) The automobiles should switch to unleaded petrol in the Taj zone.
Question 3.
What are the impacts of global warming on atmosphere?
Answer:
Global warming can cause sea-levels to rise dramatically. In many places, coastal areas have already been flooded. Global warming could result in wide-ranging effects on rainfall patterns, agriculture, forests, plants and animals. It also brings about climatic changes. It may bring about the rise in temperature to more than two degrees Celsius, a level considered dangerous.
Question 4.
How does water becomes impure? How will you know that water is impure?
Answer:
Water becomes dirty after using it for washing clothes, bathing, etc. This means that we are adding such materials to water, which degrade its quality. These materials come from human sources, but, they could also be from natural sources. By the smell, colour, acidity and turbidity of the water we can know that water is impure.
Question 5.
How is Ganga one of the ten endangered rivers of the world?
Answer:
A study by the World Wide Fund for Nature found that Ganga is one of the ten endangered rivers in the world. It is because towns and cities, through which this river flows, dispose off large quantities of garbage, untreated sewage, dead bodies, and many other harmful things, directly into the river. In fact, the river is “dead” at many places where the pollution levels are so high that aquatic life cannot survive.
Question 6.
What is Ganga Action Plan? What is its aim?
Answer:
The Ganga Action Plan is an ambitious plan which was launched to save the river Ganga in 1985. It aims to reduce pollution levels by treating domestic sewage, building electric crematories and reducing industrial waste. Apart from this water treatment plant are installed for physical, chemical and biological treatment of water.
Question 7.
Radha saw her grandmother using oil and vinegar while preserving vegetables and fruits. Why oil and vinegar has been, used for preservation?
Answer:
Preservation by oil and vinegar: The layer of oil on “top of food prevents oxygen from entering the food. Some microbes do not survive in absence of oxygen. Some microbes cannot survive in acidic environment and thus vinegar is an effective food preservative.
Question 8.
Is hot water also a pollutant?
Answer:
Yes, hot water too is a pollutant. This is usually the water from power plants and industries that is released into the rivers. It can raise the temperature of the water bodies, in turn, depleting oxygen content, adversely affecting the aquatic animals and plants.
Pollution of Air and Water Class 8 Extra Questions Long Answer Type
Question 1.
What are the ways in which atmospheric air gets polluted? Discuss.
Answer:
The ways in which atmospheric air gets polluted are :
- Many industries like petroleum refineries and automobile produce gaseous pollutants like sulphur dioxide and nitrogen dioxide.
- Sulphur dioxide is produced by combustion of fuels like coal in power plants, which causes respiratory problems including permanent lung damage.
- CFGs used in refineries, AC’s and aerosol sprays damage in ozone layer of atmosphere, which protect us from harmful UV rays of the Sun.
- Automobile which burn diesel and petrol, produce tiny particles, that reduce visibility.
- Industrial processes like steelmaking and mining involves such processes which release a lot of harmful gases, solid particles, dust, etc. which contribute in polluting air.
Question 2.
Describe greenhouse effect and its side effects as global warming.
Answer:
The sun rays that pass through the atmosphere, warms the earth’s surface. Apart of these radiation that falls on the earth is absorbed by it and a part is reflected back j into space. Some of the reflected radiations are trapped by the atmosphere and are not allowed to go out of the earth’s atmosphere.
These trapped radiations further warm the earth. This resembles a greenhouse in a nursery where sun’s heat is allowed to get in but is not allowed to go out. The trapped heat warms the greenhouse. The trapping of radiation by the earth’s atmosphere performs a similar function. That is why, it is called the greenhouse effect.
As a result of greenhouse effect, the average temperature of the earth’s atmosphere is gradually increasing. This is known as global warming.
Global warming has become a Serious threat to the survival of life on earth, because:
(i) It has already started melting the icebergs, due to which level of water in the sea has increased and many cities at coastal areas are threatened to be submerged completely.
(ii) It will too result in change in climate and rainfall pattern.
Question 3.
Differentiate between manure and fertilizers.
Answer:
| Fertilizer | Manure |
| 1. Fertilizer is a synthetic substance or an inorganic compound. | 1. Manure is a natural substance obtained by the decomposition of cattle dung, human waste and plant residues. |
| 2. A fertilizer is prepared in factories. | 2. Manure can be prepared in the fields. |
| 3. A fertilizer does not provide any humus to the soil. | 3. Manure provides a lot of humus to the soil. |
| 4. Fertilisers are very rich in plant nutrients like nitrogen, phosphorus and potassium. | 4. Manure is relatively less rich in plant nutrients. |
| 5. Chemicals in fertilisers are washed away to the nearby water bodies, causing soil, and water pollution. | 5. No side effects of manure are absorbed. |