POLLUTANTS AND THEIR EFFECTS ON THE ENVIRONMENT
Grade 8 Unit 4 Notes all short and long questions.
1. What are the natural sources of pollution?
Ans: Dust storms, rotting vegetation and volcanic eruption are three major natural sources of pollution.
2. Which human activities are causing pollution?
Ans: Burning of fuels, extensive use of vehicles, aerosols, fertilizers, insecticides, pesticides, and burning of fuels in houses and industries are major activities causing pollution.
3. What are air pollutants?
- Carbon monoxide (CO)
- Sulphur dioxide (SO2)
- Oxides of nitrogen (NO and NO2)
4. Write the sources of the following air pollutants. Or point out the sources of air pollutants you find in your locality.
Air Pollutants Sources
I) Air Pollutants: CO (Carbon monoxide)
- Incomplete combustion of fuel
- The smoke released from motor vehicles and industries
II) Air Pollutants: SO2 (Sulphur Dioxide)
- Burning of coal or oil in factories
- The smoke of thermal power stations.
- Volcanic eruption
III) Air Pollutants: NO and NO2 (Oxides of nitrogen)
- Burning of coal and oil at high temperature in industries and vehicles.
IV) Air Pollutants: CFCs (Chlorofluorocarbons)
Sources: On leakages from the refrigerator, air conditioner aerosol spray
5. Write properties of carbon monoxide.
Ans: Carbon monoxide is a colourless, odourless and poisonous gas. It is heavier than air.
6. What are the effects of carbon monoxide on the human organ system?
Ans: It causes headaches, brain damage and respiratory problems. It binds with
haemoglobin and reduces its oxygen-carrying capacity.
7. Write 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 of 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 heat reflected by the Earth and cause to increase in the atmospheric temperature. This phenomenon is called a greenhouse.
16. Why ozone layer is 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 serious 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 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 the 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 barks 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 as a result of 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.
- It changes to weather and climate.
- The rate of evaporation is reduced which results in less rain.
- Cutting of trees leads to soil erosion.
- 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 being disturbed.
29. Why are forests at risk from humans?
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: At least 25% of the total area of a country must be covered by forests.
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 much ratio of carbon dioxide has 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 cannot 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 the non-renewable resources?
Ans: The reasons for decreasing the non-renewable resources are here as under:
- Unwise use of natural resources
- A lot of energy is wasted by man.
- 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: There are three methods used for the conservation of resources.
This is a 3R strategy that is used for the conservation of resources.
- Reduce: It means minimum use of resources
- Reuse: It means the use of things again and again instead of throwing them after their first use.
- Recycle: It means that waste objects should be collected, cleaned, melted and remoulded into new objects.
38. What should our government do to control air pollution?
Ans: Government should shift the factories away from the urban areas.
CFCs-free products should be used. 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 in the 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 common methods which are used 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 remoulded 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 pieces 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: Factory owners should treat waste before throwing it. The smoke of factories must be treated before releasing 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.