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SEBA Class 8 General Science Chapter 9 Solution 2026 | Air and water pollution | Class 8 Science Chapter 9 Books Question Answer

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SEBA Class 8 General Science Chapter 9 Solution 2026 | Air and water pollution | Class 8 Science Chapter 9 Books Question Answer

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Chapter 18Air and water pollution&nbsp;

1. 1. What are the ways in which water&nbsp;can&nbsp;be polluted&nbsp;?

Answer:&nbsp;The causes of water pollution&nbsp;are&nbsp;:

(&nbsp;a)&nbsp;Water is polluted by&nbsp;bathing&nbsp;, washing clothes in rivers.

(&nbsp;b)&nbsp;Water is polluted by&nbsp;toxic chemicals discharged from industries into rivers&nbsp;,&nbsp;lakes&nbsp;and ponds.

(&nbsp;c)&nbsp;Water is polluted by pesticides and chemical fertilizers used in agriculture.

(&nbsp;d)&nbsp;Water is polluted by dumping&nbsp;of garbage&nbsp;, dead bodies etc. into the water.&nbsp;&nbsp;

2. 2. How can you personally reduce air pollution&nbsp;?

Answer:&nbsp;To reduce air pollution,&nbsp;&nbsp;&nbsp;we need to do the following:&nbsp;

(&nbsp;a)&nbsp;Trees shall be planted.

(&nbsp;b)&nbsp;We must reduce the use of cars as much as possible.

(&nbsp;c)&nbsp;We can reduce air pollution by using&nbsp;CNG&nbsp;and unleaded petrol&nbsp;instead of diesel petrol .&nbsp;

(&nbsp;d)&nbsp;Alternative fuels must be sought to replace fossil fuels.

(&nbsp;e)&nbsp;Awareness among the public about air pollution shall be increased.

3. 3.&nbsp;'&nbsp;Clean&nbsp;,&nbsp;clear (sparkling) water is safe to drink&nbsp;' -&nbsp;give your opinion.

Answer:&nbsp;It does not&nbsp;appear&nbsp;&nbsp;to&nbsp;be &nbsp; '&nbsp;useful to drink clean&nbsp;,&nbsp;clear (sparkling) water&nbsp;This is because clean-looking&nbsp;,&nbsp;transparent water can contain many disease germs&nbsp;,&nbsp;toxins&nbsp;,&nbsp;iron&nbsp;, and&nbsp;unnecessary substances. Therefore, this water&nbsp;can&nbsp;beif&nbsp;the water we drink is clean&nbsp;and&nbsp;transparent&nbsp;, we should always treat it.

4. The Suppose you are a member of the municipal corporation of your city.&nbsp;Make a list of&nbsp;the measures you will&nbsp;take to provide clean water to all the households in your city .

Answer:&nbsp;The&nbsp;measures taken to provide clean water&nbsp;are&nbsp;-&nbsp;&nbsp;&nbsp;&nbsp;

(&nbsp;a)&nbsp;Care shall be taken to ensure that water supply pipes do not come into contact with sewers.

(&nbsp;b)&nbsp;Water tanks shall be kept thoroughly clean.

(&nbsp;c)&nbsp;Chlorine tablets or bleaching powder should be used in water in a timely manner.

(&nbsp;d)&nbsp;Care shall be taken to ensure that there are no holes in the pipes used for water supply.

(&nbsp;e)&nbsp;Drinking water supply shall be ensured to every household through drinking water supply schemes.

5. 5. Explain the differences between clean air and polluted air.

Answer:&nbsp;A mixture of pure air by volume contains 78% nitrogen and 21% oxygen gas. It also contains very low levels of carbon dioxide&nbsp;,&nbsp;methane&nbsp;,&nbsp;argon and water vapor.Clean air strengthens human health.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In polluted air, on the other hand, the proportion of upper air varies. This air is harmful to health. This air enters the body through breathing and causes various diseases. Polluted air can cause asthma&nbsp;,&nbsp;phlegm and other diseases.

6. 6. Explain under what circumstances acid rain can occur. How has acid rain harmed us&nbsp;?

Answer:&nbsp;&nbsp;There are various types of industries around us like rubber industry&nbsp;,&nbsp;transportation industry&nbsp;,

chemical industries etc. gases such as sulfur dioxide and nitrogen dioxide

They are releasing pollutants into the air and increasing the amount of air pollutants in the atmosphere. These gases are water in the atmosphere

They react chemically with steam to produce sulfuric acid and nitric acid. This is

Acids acidify rainwater. Such rain is called acid rain&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;Acid rain harms us in various ways. such as-&nbsp;

(&nbsp;a)&nbsp;Acid rain increases the acidity of agricultural soils&nbsp;,&nbsp;resulting in reduced yields.

(&nbsp;b)&nbsp;Acid rain increases the acidity of water in reservoirs which&nbsp;destroys the eggs of&nbsp;fish and frogs.

(&nbsp;c)&nbsp;The leaves ,&nbsp;fruits&nbsp;, and flowers&nbsp;of plants&nbsp;fall off quickly and the buds wither.

(&nbsp;d)&nbsp;Acid rain causes damage to marble which leads to damage to buildings and ancient monuments.

(&nbsp;e)&nbsp;Acid rain increases the corrosion of metals.

7. 7. Which of the following gases are not greenhouse gases&nbsp;?&nbsp;

(&nbsp;a) Carbon dioxide.

(&nbsp;b) Sulfur-dioxide.

(&nbsp;c) Methane.

(&nbsp;d) No&nbsp;'&nbsp;Trojan.

Answer:&nbsp;(&nbsp;d) No&nbsp;'&nbsp;Trojan.

8. 8.&nbsp;Describe the&nbsp;'&nbsp;greenhouse effect&nbsp;'&nbsp;in your own words .

Answer:&nbsp;We know that the sun's rays keep the Earth's surface warm. Part of the sun's radiated rays are absorbed by the Earth and another part is reflected back into space.&nbsp;Part of&nbsp;this reflected radiation&nbsp;is retained by the atmosphere, which pollutes the air and keeps the Earth warm. This is called the greenhouse effect. Without this phenomenon, it is impossible for organisms to survive but now it is a threat to organisms due to&nbsp;the&nbsp;increase in the amount of carbon dioxide in greenhouses and pollution of the atmosphere.&nbsp;Carbon dioxide gas absorbs heat and does not release this heat upwards. As a result, the Earth's temperature is slowly rising. This is called global warming.&nbsp;Global warming is causing sea levels to rise unexpectedly. Global warming&nbsp;affects&nbsp;rainfall&nbsp;,&nbsp;&nbsp;agricultural fields&nbsp;,&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

10. 10. Describe the threat to the beauty of the Taj Mahal.

Answer:&nbsp;Experts believe that air pollutants have tarnished and discolored the marble of the Taj Mahal. Especially various types of industries around Agra like rubber industry&nbsp;,&nbsp;automotive industry&nbsp;,&nbsp;chemical industry etc. have increased the air pollutants in the atmosphere by releasing air pollutants like sulfur dioxide and nitrogen dioxide etc. into the air. These gases react chemically with water vapor in the atmosphere to form sulfuric acid and nitric acid. These acids acidify rainwater and cause acid rain. This acid rain has caused particular damage to marble. The Supreme Court has directed the industry to use refined gases like CNG and LPG to protect the Taj Mahal. In addition, the beauty of the Taj Mahal has been damaged by vehicles traveling around it.

11. 11. Discuss how an increase in nutrients in water affects the survival of aquatic organisms.

Answer:&nbsp;&nbsp;Chemicals used in agriculture go into the water and pollute it. These act as algae nutrients and increase the amount of algae. When these algae die, they help in the breakdown of bacteria. These bacteria use the oxygen in the water and this reduces the amount of oxygen in the water. Aquatic organisms in the water can die due to low oxygen levels in the water. Thus, the increase in nutrients in water affects the survival of aquatic organisms.

Additional Questions:&nbsp;

(&nbsp;a) Name the greenhouse gases.

Answer:&nbsp;&nbsp;Carbon dioxide&nbsp;,&nbsp;sulfur dioxide&nbsp;,&nbsp;methane&nbsp;,&nbsp;nitrous oxide, etc.

(&nbsp;b) What is meant by water pollutant&nbsp;?

Answer:&nbsp;&nbsp;Water is polluted by&nbsp;various harmful substances like waste&nbsp;,&nbsp;toxic chemicals&nbsp;,&nbsp;sediment etc. These substances that pollute water are called water pollutants.

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