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What are the pollutants and how they affect environment?

 POLLUTANTS AND THEIR EFFECTS ON THE ENVIRONMENT

Science Grade 8, Unit No. 4
What are the pollutants and how they affect environment?

1. What are the natural sources of pollution?

Answer:

 Dust storms, rotting vegetation, and volcanic eruption are three primary natural sources of pollution. 

2. Which human activities are causing pollution?

Ans: Burning fuels, extensive use of vehicles, aerosols, fertilizers, insecticides, and burning of fuels in houses and industries are significant activities causing pollution. 

3. What are air pollutants?

Ans:

 i. Carbon monoxide (CO)

 ii. Sulphur dioxide (SO2)

iii. Oxides of nitrogen (NO and NO2)

iv. Chlorofluorocarbons. 

4. Write the sources of the following air pollutants. Or point out the sources of air pollutants you find in your locality.

Answers.

Air Pollutants Sources

i. CO (Carbon monoxide) Incomplete combustion of fuel

ii. The smoke released from motor vehicles and industries

iii. SO2 (Sulphur Dioxide) Burning of coal or oil in factories

The smoke of thermal power stations

Volcanic eruption

v. NO and NO2 (Oxides of nitrogen) Burning of coal and oil at high 

The temperature in industries and vehicles.

vi. CFCs (Chlorofluorocarbons) On leakages from the refrigerator, air conditioner

 and aerosol spray

5. Write the properties of carbon monoxide. 

Ans: Carbon monoxide is a colorless, odourless, and poisonous gas.

6. What are the effects of carbon monoxide on the human organ system?

Ans: It causes a headache, brain damage and respiratory problems. It binds with hemoglobin and reduces its oxygen-carrying capacity. 

7. Write the properties of sulphur dioxide. 

Ans:  It is colourless with an irritating smell. It dissolves in water. 

8. What are the effects of sulphur dioxide on the human organ system?

Ans: Sulphur dioxide causes: 

Pneumonia, lung cancer, respiratory failure, asthma and heart diseases 

9. What are the effects of nitrogenous oxides on the human organ system?

Ans: They have severe effects on the lungs and damage them. 

10. What are the effects of nitrogenous oxides on plants?

Ans: They destroy the leaves and bark of the trees. 

11. What are the effects of sulphur dioxide on plants? 

Ans:  It destroys chloroplast in plants, and as a result, photosynthesis and plant growth are affected.

12. Which human activities are affecting the environment badly?

Ans: Burning fuels, extensive use of vehicles, aerosols, fertilizers, insecticides, pesticides and deforestation are affecting the environment badly. 

13. What is a greenhouse? 

Ans: A greenhouse is a big room made of glass or transparent plastic sheets. It provides a warm environment to the plants growing inside it. Plants can grow well during winter in it.

14. Write the names of greenhouse gases. 

Ans: Carbon dioxide, Methane, Oxides of nitrogen, Water vapours. 

15. What is the greenhouse effect? 

Ans: Greenhouse gases trap a part of the heat reflected by the Earth and cause to increase in the atmospheric temperature. This phenomenon is called a greenhouse. 

16. Why is the ozone layer important? 

Ans:  A layer of ozone (O3) in the upper atmosphere of the Earth stops the ultraviolet rays coming from the Sun to the Earth. In this way, it saves living things from the harmful effects of the ultraviolet radiation coming from the Sun. 

17. How is the ozone layer depleting? 

Ans: Chlorofluorocarbons react with ozone and cause its depletion. 

18. What are the effects of ozone depletion? 

Ans: Ultraviolet rays reach the Earth and cause severe diseases like skin cancer and eye problems. 

These rays also increase the temperature of the Earth. 

19. What is meant by global warming? 

Ans: The temperature of the Earth is increasing due to ozone depletion and the greenhouse effect. This phenomenon is called global warming. 

20. What are the effects of global warming? 

Ans:  The climate of the world is changing due to global warming. Global warming is a threat to life on Earth. 

21. What are the effects of global warming on life on Earth? 

Ans: Global warming is a threat to life on Earth. Glaciers are melting and the sea level is increasing. Thus, many cities are going to become a part of the sea. 

22. Name the acids which are present in acid rain. 

Ans: Sulphuric acid and Nitric acid

23 What is acid rain? 

Ans: Sulphuric acid and Nitric acid mix in water vapours and make the rainwater acidic. 

24. What are the effects of acid rain on living things? 

Ans: Acid rain kills the aquatic life in rivers, lakes and ponds. Microorganisms present in soil are also affected by acid rain. 

 It destroys the leaves and bark of the trees. Crops do not grow well in acidic soil.

25. What are the effects of acid rain on non-living things?

Ans:  Acid rain corrodes metals. Acid rain corrodes the stonework in buildings. 

26. What is meant by deforestation?

Ans: The destruction of forests due to human activities is called deforestation. 

27. What type of climate change appears by deforestation? What are the effects of deforestation on the environment? (Give any three effects of deforestation on the environment. V4 2016)

Ans: 

Effects of Deforestation

  1.   It changes to weather and climate.
  2. The rate of evaporation is reduced, which results in less rain. 
  3. Cutting of trees leads to soil erosion.
  4. Deforestation leads to global warming.

28. What are the effects of deforestation on wildlife?

Ans: Deforestation destroys the habitats of wildlife. The extinction risk of wildlife is increased. The natural balance or ecosystem is disturbed. 

29. Why are forests at risk from humans? (V4 2016)

Ans:  Human is cutting trees to meet the demand for timber. He is destroying forests to gain firewood. Man is cutting trees to obtain land for housing and agriculture. 

30. How much area of a country should be covered with forests? 

Ans: Forests must cover at least 25% of a country’s total area. 

31. How much area of Pakistan is covered by forests? 

Ans: Only 5% of the total area of Pakistan is covered by forests. 

32. How many ratios of carbon dioxide have increased in the air? What is its cause? 

Ans: The ratio of carbon dioxide has increased from 0.03% to 0.04% in about 100 years. 

It is increased due to human activities. 

33. What are natural resources?

Ans: Fossil fuels (coal, natural gas and oil), minerals, trees, animals, and water are natural resources. 

34. What are non-renewable resources?

Ans: Fossil fuels and minerals can not be regenerated quickly. These are called non-renewable resources. 

35. What should we do to control pollution? What is our responsibility to control air pollution? 

Ans:  We should not throw garbage in open spaces. We should grow more and more trees. We should create awareness among people to save our Earth. 

36. What are the reasons for decreasing non-renewable resources? 

Ans: The reasons for decreasing the non-renewable resources are here as under: 

  1. Unwise use of natural resources
  2. A lot of energy is wasted by man. 
  3. Personal vehicles are used instead of public transport. 

37. Write the methods for the conservation of resources? What is meant by the 3R strategy? 

Ans: 

3R Strategy

There are three methods used for the conservation of resources. 

  1. Reduce
  2. Reuse 
  3. Recycle 

Reduce, Reuse and Recycle is a 3R strategy that is used for the conservation of resources. 

  1. Reduce: It means minimum use of resources
  2. Reuse: It means the use of things again and again instead of throwing them after their first use. 
  3. Recycling means waste objects should be collected, cleaned, melted and remolded into new objects.

38. What should our government do to control air pollution?

Ans: 

Suggestions to Control Air Pollution

i. Government should shift the factories away from the urban areas.

ii. We should use CFCs-free products in houses.  

ii. Trees should be grown along the roads.

39. Suggest ways to reduce pollution.

Ans: We should not throw garbage in open places. We should avoid cutting trees. 

We should use public transport instead of personal cars. 

40. What can students do to reduce air pollution? 

Ans: Students should take part in planting trees. 

Students should create awareness among people about throwing garbage. 

Students should not throw garbage open in school and at home. 

41. What should farmers do to reduce air pollution? 

Ans: Farmers should grow more and more trees. Farmers should avoid using insecticides. 

42.  Name standard methods which are used for solid waste management. 

Ans:

Standard Methods for Solid Waste management

Landfill: In this method, solid wastes are buried in landfills. 
Incineration: In this method, solid wastes are burned.

Recycling: In this method, solid wastes should be collected, cleaned, melted and remolded into new objects.

43. Write down the names of three such products which can be recycled.

Ans: Plastic bottles, steel cans, copper wires and glass can be recycled. 

 

44. How does ozone depletion contribute to global warming?

Ans: The temperature of the Earth is increasing due to ozone depletion. 

As a result of ozone depletion, the Earth is getting warmer. 

45. What should factory owners do to reduce air pollution?

Ans:  

i. Factory owners should treat waste before throwing it.

ii. Factory owners should treat the smoke of factories before releasing it into the air. 

46. What should scientists do to reduce air pollution?  

Ans: Scientists should invent pollution-free products. They should prepare pollution-free insecticides and fertilizers.  

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