Pollution of Air and Water Class 8 Worksheet Science

Q.1. What is Kyoto Protocol?

The Kyoto Protocol is an international agreement that aimed to reduce carbon dioxide (C₂O) emissions and the presence of greenhouse gases in the atmosphere.

Q.2. Describe the ‘Green House Effect’ in your own words.

The greenhouse effect is a warming of Earth's surface and the air above it. The sun’s rays warm the earth’s surface. A part of the radiation that falls on the earth is absorbed by it and a part is reflected back into space. A part of the reflected radiation is trapped by the atmosphere. The trapped radiations further warm the earth. This process is called the greenhouse effect. Without this process, life would not have been possible on the earth.

Q.3. Explain circumstances leading to acid rain. How does acid rain affect us?

Harmful gases such as sulphur dioxide and nitrogen dioxide react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. The acids drop down with rain, making the rain acidic. This is called acid rain.

Q.4. Prepare a brief speech on global warming that you have to make in your class.

CO₂ is one of the gases responsible for this effect. Carbon dioxide is needed by plants. But if there is excess of CO₂ in the air, it acts as a pollutant. On the one hand, CO₂ is continuously being released because of human activities. On the other hand, area under forests is decreasing. Plants utilise CO₂ from the atmosphere for photosynthesis, thereby decreasing the amount of CO₂ in the air. Deforestation leads to an increase in the amount of CO₂ in the air because the number of trees which consume CO2 is reduced. Human activities, thus, contribute to the accumulation of CO₂ in the atmosphere. CO₂ traps heat and does not allow it to escape into space. As a result, the average temperature of the earth’s atmosphere is gradually increasing. This is called global warming.

Q.5. Write one source and one harmful effect of sulphur dioxide.

Sulphur dioxide is produced by combustion of fuels like coal in power plants. It can cause respiratory problems, including permanent lung damage.

Q.6. Why does the increased level of nutrients in the water affect the survival of aquatic organisms?

Excessive quantities of chemicals (fertilizers, pesticides and weedicides) which get washed from the fields act as nutrients for algae to flourish. Once these algae die, they serve as food for decomposers like bacteria. A lot of oxygen in the water body gets used up. This results in a decrease in the oxygen level which may kill aquatic organisms.

Q.7. Describe the threat to the beauty of the Taj Mahal.

The beauty of the Taj Mahal in white marble is being threatened by air pollution in the area surrounding the Taj. Due to increase in pollutants like sulphur dioxide and nitrogen dioxide in air, acid rain take place. Acid rain corrodes the marble of the monument. The phenomenon is also called “Marble cancer”. Suspended particulate matter, such as the soot particles emitted by Mathura oil refinery, has contributed towards yellowing of the marble.

Q.8. What is Ganga Action Plan? When was it launched? What was its purpose?

An ambitious plan to save the river, called the Ganga Action Plan was launched in 1985. It aimed to reduce the pollution levels in the river. Recently a study by the World Wide Fund for Nature (WWF) found that Ganga is one of the ten most endangered rivers in the world. The pollution levels have been rising for many years. This stage is reached because the towns and cities, through which the river flows, throw 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.

Q.9. Write one source and one harmful effect of carbon monoxide.

Carbon monoxide is produced from incomplete burning of fuels such as petrol and diesel. It is a poisonous gas. It reduces the oxygen-carrying capacity of the blood.

Q.10. Explain the differences between pure air and polluted air.

Pure air consists of a mixture of gases. By volume, about 78% of this mixture is nitrogen and about 21% is oxygen. Carbon dioxide, argon, methane, ozone and water vapour are also present in very small quantities.
When air is contaminated by unwanted substances which have a harmful effect on both the living and the non-living, it is referred to as polluted air.

Q.11. How can we prevent wastage of water?

We can prevent wastage of water in the following ways:
(i) Reuse water for washing and for other household tasks. For example, water used for washing vegetables may be used to water plants in the garden.
(ii) Turn off the tap immediately after use.
(iii) Get the leaking taps repaired immediately.
(iv) Brush teeth by filling water in a mug.

Q.12. What are the main sources of air pollution?

Sources of air pollution
(i) Natural sources like smoke and dust arising from forest fires or volcanic eruptions causes air pollution.
(ii) Pollutants are also added to the atmosphere by human activities. The sources of air pollutants are factories, power plants, automobile exhausts and burning of firewood and dung cakes.
(iii) Pollutants like sulphur dioxide and nitrogen dioxide gases react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid and causes acid rain.
(iv) Carbon monoxide is produced from incomplete burning of fuels such as petrol and diesel. It is a poisonous gas.
(v) Chlorofluorocarbons (CFCs) which are used in refrigerators, air conditioners and aerosol sprays cause air pollution.

Q.13. What is air pollution?

Air pollution is the contamination of air by impurities which may have a harmful impact on the living organisms and the non-living components.

Q.14. What is smog? How is it formed? What are its harmful effects?

A thick fog-like layer in the atmosphere, especially during winters made up of smoke and fog is called smog. Smoke may contain oxides of nitrogen which combine with other air pollutants and fog to form smog. The smog causes breathing difficulties such as asthma, cough and wheezing in children.

Q.15. How can we prevent wastage of water?

We can prevent wastage of water in the following ways:
(i) Reuse water for washing and for other household tasks. For example, water used for washing vegetables may be used to water plants in the garden.
(ii) Turn off the tap immediately after use.
(iii) Get the leaking taps repaired immediately.
(iv) Brush teeth by filling water in a mug.