NCERT Solution For Class 8 Science, Chapter 18 – Pollution of Air & Water

NCERT Solutions is known as an extremely helpful resource for preparing for the exam. Takshila Learning provides its learners with access to a wealth of NCERT problems and their solutions. CBSE Class 8 Science NCERT Solutions are built by subject matter experts, so be sure to train learners for a good grade. The questions set out in the NCERT Books are prepared in compliance with the requirements of the CBSE.

NCERT Solution For Class 8 Science, Chapter 18 – Pollution of Air & Water provides us with all-inclusive information on all concepts. As students would have to learn the basics about the subject in class 8, this curriculum for class 8 is comprehensive study material, which explains the concepts in a great way.

Q.1.  What are the different ways in which water gets contaminated? Water gets contaminated by the following ways:

Ans.        (i) Many industries discharge chemicals harmful to rivers and drains.

(ii) At the time of disposal of sewage in rivers, water gets contaminated.

(iii) Pesticides, weeds and other chemicals also dissolve in water and become contaminated.

(iv) Water is polluted by breeding of microorganisms.

Q.2.  At an individual level, how can you help reduce air pollution?

Ans.  In this process we reduce air pollution:            (i) We can plant trees to reduce the level of carbon dioxide and air pollution.            (ii) By using CNG and unleaded petrol in our vehicle.            (iii) By using public transport as far as possible.            (iv) By giving general awareness about air pollution to our family and friends.

Q.3.  Clear, transparent water is always fit for drinking. Comment.

Ans.  Clean, transparent water is always fit for drinking. This is not true, as many microorganisms are present in it. So we boil it and clean it.

Q.4.  You are a member of the municipal body of your town. Make a list of measures that would help your town to ensure the supply of clean water to all its residents.

Ans.   A list of measures that will help our city to ensure clean water supply to all its residents        (i) Proper cleaning of the water tank.        (ii) Chlorine tablets should be made available.        (iii) To reach clean water in every house, it is necessary that the water reaching the houses is treated.

Q.5.  Explain the differences between pure air and polluted air.

Ans.  Pure air is free from germs and harmful gases. It contains 78% nitrogen, 21% oxygen and small amounts of other gases and dust particles.        Polluted air contains harmful gases and unwanted substances.

Q.6.  Explain circumstances leading to acid rain. How does acid rain affect us?

Ans.  Some pollutants such as sulfur dioxide and nitrogen dioxide react with the water vapor present in the atmosphere to form sulfuric acid and nitric acid. The acid drops down with the precipitation, making the rain acidic. This is called acid rain. Acid rain affects us in many ways.        (i) Acidic rain combines the marble of the monument.        (ii) Acid rain damages building and sculpture materials.iii) Fresh water also damages due to acid rain.        (iv) Acid rain also damages our crops and makes it poisonous.        (v) Acidic rain damages the leaves of plants.

Q.7.  Which of the following is not a greenhouse gas?

        (a) Carbon dioxide

(b) Sulphur dioxide

        (c) Methane

(d) Nitrogen.

Ans.   Nitrogen.

Q.8.  Describe the `Greenhouse Effect’ in your words:

Ans.   The greenhouse effect means warming the environment. When the sun’s rays reach the Earth, a part of the radiation that falls on the Earth is absorbed by it and a part is reflected back into space. A portion of the reflected radiation is trapped by the atmosphere. This trapped radiation further warms the Earth. This is called the carbon house effect. CO2 is one of the gases responsible for this effect.

Q.9.  Prepare a brief speech on global warming. You have to deliver the speech in your class.

Ans.  The constant increase in the temperature of the Earth is called global warming. There are many reasons for this. One of them is population growth. The increase in the number of vehicles is also a reason. Air pollution has also increased global warming. Cutting of trees, grazing of plants by animals increases global warming.

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

Ans.  In the last 2 decades, India’s most famous tourist attraction, the Taj Mahal in Agra, has become a matter of concern. Experts warn that air pollution is eroding its white marble.        Therefore it is not only living organisms that are affected by polluted air, but also non-living things like buildings, monuments and sculptures.        Industries located in and around Agra such as rubber processing, automobiles, chemicals and, in particular, the Mathura oil refinery sulfur Have been responsible for the production of pollutants such as dioxide and nitrogen dioxide. These gases react with the water vapor present in the atmosphere to form sulfuric acid and nitric acid. They come down with rain, making the rain acidic. This is called acid rain. Acid rain has caused the monument’s marble erosion. This phenomenon is also called marble cancer.The soot particles emitted by the Mathura Oil Refinery, such as suspended particulate matter, have contributed to yellowing of the marble. The Supreme Court has taken steps to save the Taj. It has ordered the industries to switch to cleaner fuels like CNG ( Compressed Natural Gas) and LPG (Liquefied Petroleum Gas). Moreover, the automobiles should switch over to unleaded petrol in the Taj zone.

Q.11.  Why does the increased level of nutrients in the water affect survival of aquatic organisms?

Ans.   An excessive amount of chemicals flow from the fields. These act as nutrients for algae to thrive. Once these algae die, they act as food for decomposers such as bacteria. Water uses a lot of oxygen in the body. This results in a decrease in oxygen level that can kill aquatic organisms.

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