Science In Everyday Life Solutions for Class 8 Science Chapter 18 Pollution Of Air And Water are provided here with simple step-by-step explanations. These solutions for Pollution Of Air And Water are extremely popular among class 8 students for Science Pollution Of Air And Water Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Science In Everyday Life Book of class 8 Science Chapter 18 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Science In Everyday Life Solutions. All Science In Everyday Life Solutions for class 8 Science are prepared by experts and are 100% accurate.

Page No 256:

Question 1:

Write two examples for each of the following.

1. Carbon-rich fuels .................... ....................
2. Fossil fuels .................... ....................
3. Acids that constitute acid rain .................... ....................
4. Respiratory diseases caused by air pollution .................... ....................
5. Chemicals that can be added to purify water .................... ....................

Answer:

1. Coal, Firewood
2. Coal, Petroleum
3. Nitric acid, Sulphuric acid
4. Asthma, Bronchitis
5. Chlorine, Potassium Permanganate

Page No 256:

Question 2:

Define/Explain the following.
1. Air pollution
2. Greenhouse effect
3. Eutrophication
4. Potable water

Answer:

1. Air pollution: The presence such amount of chemicals and undesirable material in air which has harmful effects on plants, animals, objects and the surroundings is called Air pollution.
2. Green house effect: The trapping of the solar radiation by the earth’s atmosphere due to the presence gases such as carbon dioxide, water vapour and methane is called Green house effect. These gases are called greenhouse gases.
3. Eutrophication: The addition of excessive amount of nutrients to water bodies which promotes excessive growth of plants in the water body is called Eutrophication.
4. Potable water: The water free from harmful chemical, which is transparent and odourless,  safe for consumption by human beings is called Potable water.

Page No 256:

Question 1:

20.95% of the air is
(a) carbon dioxide
(b) oxygen
(c) nitrogen
(d) sulphur

Answer:

(b) Oxygen
Air contains 20.95% of oxygen.

Page No 256:

Question 2:

A less-polluting fuel is
(a) petrol
(b) CNG
(c) diesel
(d) coal

Answer:

(b) CNG
Out of the given options CNG is the least polluting.

Page No 256:

Question 3:

Ground water is obtained from
(a) wells
(b) springs
(c) oceans
(d) seas

Answer:

(a) Wells
Wells are the source for ground water.

Page No 256:

Question 4:

A sample of water is considered fit for human consumption if the water is
(a) transparent, colourless, and odourless
(b) contains sufficient amount of dissolved oxygen and salts
(c) free from harmful chemicals and microorganisms
(d) all of these

Answer:

(d) all of these
A sample of water should be transparent and odourless, should contain adequate amounts of dissolved salts and oxygen and should be free from harmful chemicals and microorganisms to be considered fit for human consumption.

Page No 256:

Question 5:

Which of the following are the chemical methods of purifying water at home?
(a) Boiling and use of electric water filters
(b) Addition of chemical tablets and use of electric water filters
(c) Boiling and addition of chemical tablets
(d) Boiling and distillation

Answer:

(b) Addition of chemical tablets and use of electric water filters.
Water at home can be purified by chemical methods such as addition of chemical tablets and using electric water filters.

Page No 256:

Question 1:

Match the following.

Column A Column B
Nitrogen 20.95%
Oxygen CFC
Freons Coal
Particulate matter 78.08%
Fossil fuels Air pollution

Answer:

Sl.No Column A Column B
1. Nitrogen 78.08%
2. Oxygen 20.95%
3. Freons CFC
4. Particulate matter Air pollution
5. Fossil fuels Coal



Page No 257:

Question 1:

What are the various gases present in air and their percentage?

Answer:

The various gases present in air are:  

  • Oxygen, the percentage of oxygen in air is 20.95%
  • Nitrogen, the percentage of nitrogen in air is 78.08%
  • Other gases, the percentage of other gases in air is 0.97%
  • Other gases constitute CO2, H2O, He, Ne, Ar, Kr, CH4 , H2 etc.

Page No 257:

Question 2:

What does burning of fossil fuels result in?

Answer:

Burning of fossil fuels such as petroleum and coal results in air pollution. This is because burning of fuels in thermal power plants and automobiles releases harmful chemicals such as oxides of sulphur and nitrogen into the air.

Page No 257:

Question 3:

Differentiate between global warming and acid rain.

Answer:

Sl.No. Global warming Acid rain
1. The rise in the temperature on the surface of the earth is called global warming. It might be due to phenomena like green house effect. The reaction of air pollutants such as oxides of sulphur and nitrogen with water vapour and oxygen of the earth’s atmosphere results in the formation of dilute sulphuric and nitric acids. When these acids mix with rain water, they pour down as Acid rain.
2. Carbon dioxide and methane are the gases  mainly responsible for global warming. Oxides of sulphur and nitrogen contribute to the formation of acid rain on earth.

Page No 257:

Question 4:

List some causes and possible effects of global warming.

Answer:

The rise in temperature of earth’s surface due to the increased amounts of green house gases in the atmosphere is called global warming. The causes and possible effects of global warming are :

  • Deforestation: This results in the increase of the temperature on the surface of the Earth, since not enough trees are available to absorb carbon dioxide from the air which ultimately leads to increase in the amount of CO2 in the atmosphere.
  • Burning of fossil fuels: This results in the release of carbon dioxide that contributes to global warming.
  • Release of methane: The breakdown of organic matter releases methane which causes the global sea levels to rise submerging the low lying coastal regions because it is a green house gas.

Page No 257:

Question 5:

How does ozone layer protect life on Earth?

Answer:

The ozone layer absorbs harmful ultraviolet rays emitted by the sun and prevents them from reaching the surface of the earth. If excess ultraviolet rays reach the surface of the earth, it can kill plants and animals and prove very harmful to life on earth.

Page No 257:

Question 6:

What are the main types of water sources?

Answer:

Water is a precious natural resource covering about 75% of the earth’s surface. The three main sources of water are:

  • Surface water: Lakes, rivers, waterfalls and streams, fed by rains or melt ice from mountains, hills or glaciers, are sources for surface water.
  • Ground water: Wells are a source for ground water.
  • Salty water: Seas and Oceans are sources for salty water.

Page No 257:

Question 7:

How do oil leaks affect marine life?

Answer:

Oil leaks cause water pollution. When oil spills on water bodies such as rivers and seas, it floats in the water reducing the oxygen absorption of the water by cutting off the oxygen supply to water surface. Reduced oxygen absorption and limited photosynthetic activities gradually lead to the destruction of the marine plants. This in turn leads to the death of marine animals.

Page No 257:

Question 8:

How can we prevent water from getting polluted?

Answer:

Water is very essential for life but most of our water bodies such as rivers, lakes and seas are getting polluted at an alarming rate. We can prevent water from being polluted by:

  • Stopping the discharge of industrial and household waste into water bodies
  • Avoid washing clothes, bathing animals near the rivers, lakes and streams.
  • Prevent oil spills in water bodies which would otherwise lead to destruction of marine habitat.

Page No 257:

Question 9:

List some common methods of purifying water.

Answer:

Purification of water before consumption is necessary because water supplied to homes contains many impurities such as sand, clay and salts. Some of the common methods to purify water are filtration, distillation and sedimentation.

Page No 257:

Question 1:

Describe common air pollutants and their main sources.

Answer:

Air pollution is the introduction of excessive amounts of chemicals in air which are harmful to the plants, animals and surroundings. Common air pollutants and their sources are found below:

Sl.No. Air pollutant Sources
1. Particulate matter (tiny particles suspended in air) Forest fires, dust storms, burning of fossil fuels and dust storms
2. Carbon dioxide and carbon monoxide Burning of carbon rich fuels such as firewood coal and petroleum
3. Oxides of Sulphur and Nitrogen Burning of fossil fuels such as coal and petroleum in automobiles and thermal power plants
4. Chlorofluorocarbons Aerosol sprays, paints, thrown away metallic cans, Plastic foams, coolants and cleaning solvents

Page No 257:

Question 2:

Explain global warming and effect of greenhouse gases.

Answer:

Global warming is the unnatural rise in the temperature of the earth’s surface due to increased amounts of green house gases in the earth’s atmosphere. Green house gases such as carbon dioxide, methane and water vapour trap the solar radiation and keep our planet warm without which Earth would have been too cold to support life. Green house effect becomes a cause of concern only when there is an increase in the amounts of these gases which leads to a rise in the earth’s surface temperature beyond normal levels. This can lead to the destruction of habitats and disturb life on earth.

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Question 3:

Discuss effects of air pollution on climate, plants, and animals.

Answer:

Air pollution has adverse effects on climate, plants and animals:

Effect on Climate:  The global climate changes drastically due to global warming making it difficult to sustain life on earth. The temperature of the earth rises due to increase in the amounts of gases such as carbon dioxide and methane in the earth’s atmosphere.
Effect on plants: Air pollution can have long-lasting effects on growth and development of plants. Photochemical smog, an air pollutant inhibits the photosynthetic activity in plants. Acid rains which contain sulphuric and nitric acids can also damage plants and can cause early leaf falls.
Effect on animals: Air pollutants such as carbon monoxide, sulphur dioxide and particulate matter released into atmosphere can lead to various respiratory and cardiovascular diseases in human beings. 

Page No 257:

Question 4:

Write a short note on prevention of air pollution.

Answer:

Air pollution can have adverse effects on human beings and the environment. It should be prevented to a maximum extent as possible. This can be done by:

  • Using less polluting fuels such as Compressed Natural Gas (CNG)
  • Encouraging the use of energy resources such as Nuclear and hydroelectric energies which are less polluting
  • Using low-sulphur coals for burning
  • Pollution check should be made mandatory for all vehicles on a regular basis.
  • Encouraging the use of unleaded petrol

Page No 257:

Question 5:

Explain effects of water pollution on living beings.

Answer:

The following are the harmful effects of water pollution on living beings:

  • The discharge of industrial waste into water bodies contains many toxic substances which make water unsuitable for consumption and domestic purposes.
  • The discharge of human wastes into the water bodies leads to many water-borne diseases.
  • Oil leaks from ships deplete the water bodies by cutting off the oxygen supply of the water body. This causes a severe damage and destruction to the marine habitat.

Page No 257:

Question 6:

Describe different methods of purifying water in the city.

Answer:

Water supplied to our homes contains several impurities such as sand, salt and clay. Therefore, it is essential to purify water to be made suitable for consumption. The three main process involving purification of water in cities are:

  • Sedimentation: In this process, water from the rivers is collected in large tanks so that the suspended impurities settle down and later removed.
  • Filtration: In this process, all the other insoluble impurities are removed by passing the water through filter beds.
  • Chlorination: In this process, chlorine it added to the water to kill the microorganisms present if any. This water is further filtered and stored and finally supplied to homes via water mains.
  • Distillation: In distillation, water is first heated to convert into vapours. As vapours rise, they leave behind the impurities, and then they are condensed into a separate container by passing through a condenser.

Page No 257:

Question 7:

Explain the various ways of purifying water and removing soluble and insoluble impurities.

Answer:

The different methods to purify impure water are:

  • Filtration: This method involves passing the impure water through a filter paper to remove the insoluble impurities.
  • Sedimentation and Decantation: In sedimentation, water is left undisturbed in a container such that insoluble impurities like mud settle down. This is further transferred into a clean container through decantation process.
  • Distillation: This method involves converting impure water to steam by heating due to which impurities are left behind in a container. The steam is then passed on to a condenser where it cools and changes to pure water.

Page No 257:

Question 8:

Describe the different means of purification of water at home.

Answer:

Water supplied to our homes via water mains may not be completely free of impurities. Therefore, it is essential to purify the water at homes. It can be done by the following methods.

  • Boiling: Boiling point of water is 100°C. Water is boiled to this temperature to kill all the harmful germs and microorganisms.
  • Addition of chemical tablets: In this method chemicals such as potassium permanganate and chlorine tablets are added to destroy the microorganisms and germs.
  • Use of electric water filters: Electric water filters use electricity, micro-porous filters, carbon and ultraviolet radiation to destroy the germs and microorganisms, bad odour and taste from the water.
 



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