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Page No 260:

Question 1:

Mark the following statements as true or false. Correct the false statements.
(a) Water pollution is caused by the smoke given out by factories.
(b) Pesticides and fertilisers cause both soil and water pollution.
(c) Breathing in suspended particulate matter is not as harmful as breathing in carbon dioxide.
(d) Fertilisers provide nutrients to the soil, therefore they cannot be replaced.
(e) There are no alternatives for fossil fuels.

Answer:

(a) False

Smoke given out by factories causes air pollution.
       
(b) True 

(c) False

Breathing in suspended particulate matter is as harmful as breathing in carbon dioxide. It may lead to various respiratory problems, such as asthma.

(d) False

Fertilisers can be replaced by natural, organic products called manure, which provides nutrients to the soil.

(e) False

Solar, wind, hydro and nuclear energy can be used as alternatives to fossil fuels.

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Question 2:

Name the gases that pollute the atmosphere.

Answer:

The gases that pollute the atmosphere are as follows:

  • Carbon monoxide
  • Sulphur dioxide
  • Nitrogen oxides
  • Methane
  • Chlorofluorocarbons
  • Although, carbon dioxide is not a pollutant and its presence in the atmosphere is must to maintain the temperature of the earth, excess of CO2 being released into the atmosphere makes it a pollutant as it contributes to global warming. 

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Question 3:

What is suspended particulate matter?
How does it harm us?

Answer:

Very minute solid particles present in the air are known as suspended particulate matter (SPM).
SPM can harm us in the following ways.
(a) They can cause lung cancer, because our nose hair is not able to filter them out because of their minute sizes.
(b) They get deposited on plants and restrict the process of photosynthesis.

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Question 4:

What is the cause of the depletion of the ozone layer? How does it affect us?

Answer:

The depletion of the ozone layer refers to the reduction in the concentration of the ozone layer. It is caused by ozone-depleting substances (ODSs), such as chlorofluorocarbons (CFCs), halons, methyl bromide, nitrogen oxides and chlorine.
Among the most important ozone-depleting substances are CFCs, which are rich in chlorine, fluorine and carbon (such as carbon tetrachloride and dichlorofluoromethane).  
Effects of the depletion of the ozone layer:
(i) It causes skin cancer because of excess exposure to UV radiation.
(ii) It damages the eyes and the immune system.
(iii) It affects plants and decreases crop yields.

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Question 5:

List some of the causes of air pollution.

Answer:

Some of the causes of air pollution are as follows.

  • Burning of fossil fuels
  • Forest fires, which add enormous amounts of carbon dioxide to the atmosphere
  • Rotting of organic matter and waste, which releases methane into the atmosphere
  • Refrigeration and air conditioning, which release CFCs into the atmosphere, causing the depletion of ozone
  • Breaking down of fertilisers, which releases oxides of nitrogen into the atmosphere

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Question 6:

What is acid rain? Discuss some of the harmful effects of acid rain.

Answer:

When rainwater in the clouds mixes with sulphur dioxide and oxygen present in the atmosphere, a mixture (i.e., sulphuric acid) called acid rain is formed.

The following are the harmful effects of acid rain.
  • It severely affects the growth of plants and animals.
  • It destroys buildings by eroding their stone- and brickwork.

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Question 7:

Differentiate between a point source and a non-point source of water pollution, why do you think non-point sources of pollution are difficult to control?

Answer:

 

Point source of water pollution Non-point source of water pollution
The waste from sources such as factories and sewage treatment plants enters a water body at a specific place. Such sources of water pollution are called point sources of water pollution. When the point for entry of pollutants in the water body cannot be specified, it is termed as non-point sources of water pollution. They include surface run-off, mining wastes, construction wastes, municipal wastes and acid rain. 

Non-point sources of pollution are difficult to control because the pollutants enter water bodies at various points and at different places.

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Question 8:

Define smog. What are the harmful effects of smog?

Answer:

Smog is a haze or smoky mist which is formed by smoke and fog. Smoke containing pollutants such as oxides of nitrogen, reacts with other pollutants and combines with fog to form smog.

The following are the harmful effects of smog:
(i) It reduces visibility.
(ii) It is highly suffocating and toxic.
(iii) It can cause irritation and infection to the eyes.
(iv) It harms agriculture and ecosystems in nearby areas.

Page No 260:

Question 9:

Write short notes on the following:
thermal pollution, soil pollution

Answer:

Thermal pollution:
Thermal pollution is a type of water pollution in which heated waste is released into large water bodies, causing a change in the overall temperature of the water. The main cause of thermal pollution is the use of water as a coolant in power plants and industries and its release in lakes and large water bodies. The sudden change in the temperature of water may kill fish and other organisms, which is the most important adverse effect of thermal pollution.
   
Soil pollution:
Soil pollution refers to the degradation of soil fertility by the removal of useful components and the addition of harmful substances. Soil pollution can be caused by solid wastes as well as chemicals.
Fly ash, which is a grey powdery residue of unburnt material, is produced by most industrial furnaces and thermal power stations.
Fly ash is deposited in the soil and causes pollution. It makes the soil infertile and kills the micro-organisms living in it. 

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Question 10:

As a student and a responsible citizen of the country, list some ways in which you can help to reduce the air and water pollution

Answer:

Some ways to reduce air pollution are as follows.

  • Use of solar cookers and biogas as smokeless sources of energy
  • Promotion of solar and wind power instead of power from thermal power plants
  • Use of public transport and car pooling
  • Planting of more trees

Some ways to reduce water pollution are as follows.
  • Recycling of waste instead of dumping it into rivers
  • Reduction of the use of harmful insecticides and pesticides
  • Use of organic, biodegradable detergents instead of chemical detergents
        



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