NCERT Solutions for Class 8 Science Chapter 18-Pollution of Air and Water, contains solutions to various questions in Exercise for Chapter 18. At the end of the Solutions, all the keywords and Notes which are important to understand Science Chapter 18-Pollution of Air and Water, have been explained in a simple and easy to understand manner. NCERT Solutions for Class 8 help to check the concept you have learnt from detailed classroom sessions and the application of your knowledge.
| Category | NCERT Solutions for Class 8 |
| Subject | Science |
| Chapter | Chapter 18 – Pollution of Air and Water |
Download NCERT Solutions for Class 8 Science Chapter Chapter 18-Pollution of Air and Water
NCERT Solutions for Class 8 Science Chapter Chapter 18 Pollution of Air and Water– NCERT Exercises
Question 1
What are the different ways in which water gets contaminated ?
Answer 1
The different ways in which water gets contaminated are:
- Many harmful chemicals are discharged into rivers and streams by the industries. These are untreated wastes and thus pollute the water bodies.
- Many people take dips and bathe themselves and their clothes in rivers as an act of tradition or worship. This serves in polluting the river.
- The weedicides and the chemical fertilizers used by the farmers are washed down by rainfall or floods from the soil and get mixed with the rivers.
- Many a times untreated sewage wastes like food, canned substances etc. are thrown into the rivers contaminating the water.
Question 2
At an individual level, how can you help reduce air pollution?
Answer 2.
At an individual level we can help reduce air pollution by the following measures:
- We should make use of bicycles for non-remote transportations
- Car pools and public transport can be used instead of individual cars
- We should avoid burning leaves, trash and other materials.
- We can plant trees and saplings in order to reduce air pollution
- We should use CNG based vehicles as they help to minimize the pollution
Question 3
Clear, transparent water is always fit for drinking. Comment.
Answer 3.
Clean transparent water is always not fit for drinking because most of the microorganism which reside in water are microscopic in nature and cannot be seen with the unaided eye. Therefore, even if we see the water as clean and clear, it can contain many harmful microbes present in it. Therefore, drinkable water should be boiled to kill off the harmful microbes from water.
Question 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.
Answer 4.
The list of measures to be taken include-
- Establishment of a water treatment plant in the area.
- Chlorine tablets should be made available to purify the water.
- The defecation in water and the discharge of wastes in water should be strictly prohibited.
- The industries and factories which openly discharge chemical and toxic wastes into the nearby water bodies should be reprimanded for doing so.
- General awareness amongst the masses about the conservation and purification of water should be conveyed.
Question 5
Explain the differences between pure air and polluted air.
Answer 5.
| Pure Air | Polluted Air |
|---|---|
| It is clean and healthy for the lungs | It is harmful to the lungs and can cause respiratory diseases. |
| It has a definite composition of gases such as 78-79% nitrogen, 21% Oxygen and some traces. | It does not have any fixed composition of gases. |
| It is free of smog. | It is not free of smog. |
| It is the air that is free for breathing | It is the air that is not fit for breathing. |
Question 6
Explain circumstances leading to acid rain. How does acid rain affect us?
Answer 6.
Acid rain can be caused due to various factors. These include burning of the coal, petroleum, incineration of the garbage and decomposition of the sewage wastes and many other factors which result in the release of the oxides of nitrogen and sulphur which in turn combine with the water vapour present in the atmosphere causing acidic perspiration.
- It can cause damage to the buildings made of marbles and many other national monuments.
- It can harm the aquatic life by making the water of the rivers, ponds and oceans acidic in nature.
- It can also cause damage to the crops and reduce crop production and yield.
Question 7
Which of the following is not a greenhouse gas?
(a) Carbon dioxide
(b) Sulphur dioxide
(c) Methane
(d Nitrogen
Answer 7.
(d) Nitrogen is not a greenhouse gas
Question 8
Describe the ‘Green House Effect’ in your own words.
Answer 8.
Greenhouse Effect refers to the warming of the Earth’s atmosphere. When the rays of the sun reach the surface of the Earth then a part of the sun’s rays is absorbed by the surface and the remaining part of it is reflected back into the atmosphere. When these reflected rays are traversing back their paths, the greenhouse gases like carbon dioxide, CFC’s etc. form a thick blanket of gases and absorb these reflected rays raising the temperature of the atmosphere.
Question 9
Prepare a brief speech on global warming that you have to make in your class.
Answer 9.
Global warming is a direct consequence of the greenhouse effect. When the reflected rays of the sun are trapped by the gases present in the atmosphere then there is an average increase in the temperature of the earth’s atmosphere. This is referred to as global warming. It is a highly drastic effect which is mainly caused due to man’s activities. Global warming can lead to melting of the ice glaciers thereby increasing the sea level causing many lands to be submerged into the sea. Deforestation is one of the main reasons causing an increase in the rate of global warming. The depletion of the Ozone layer and the Ozone Hole in the atmosphere all are the result of global warming. Therefore, it should be reduced at all costs.
Question 10
Describe the threat to the beauty of the Taj Mahal.
Answer 10.
Taj Mahal is a very famous ancient monument and one of the seven wonders of the world. Acid rain is a major threat to it. When rain that is acidic in nature falls on the monument made out of pure marble, then it causes the calcium carbonate present in the marble to convert into a powdery-substances which when washes off due to the rain causing the yellowing of the marble. This is also termed as marble cancer.
Question 11
Why does the increased level of nutrients in the water affect the survival of aquatic organisms?
Answer 11.
When the level of the nutrients increase in the water, then it promotes the growth of the small green plants in the water bodies known as algae. When these algae die off, they are consumed by the bacteria which use the dissolved oxygen present in the water bodies to decompose them. This reduces the oxygen available for the aquatic and marine organisms thus affecting their survival.
Topics Covered in Chapter 18 Pollution of Air and Water System Class 8 Science :-
- Air Pollution
- How does Air Get Polluted?
- Case Study : The Taj Mahal
- Greenhouse Effect
- What can be Done?
- Water Pollution
- How does Water Get Polluted?
- What is Potable Water and How is Water Purified ?
- What can be Done?
Important Terms Relevant to understand NCERT Solutions for Class 8 Science Chapter 18 Pollution of Air and Water
Air pollution: The unwanted contamination of the air due to the introduction of the harmful substances into the atmosphere which could damage both the living and the non-living creatures is known as air pollution.
Air pollutants: The substances which contaminate the air are known as the air pollutants.
Smog: The culmination of the smoke and fog results into the formation of a smoky like fog also known as smog. It is usually seen in winters.
Acid rain: Acid rain is form of precipitation that is acidic in nature meaning it has a low pH. It can cause damage to the marbles, floors etc.
Greenhouse effect: Greenhouse effect refers to the warming of the earth’s atmosphere due to the back-reflection of the radiation emitted from the surface of the earth.
Global warming: Global warming refers to the average increase in the temperature of the atmosphere of the earth due to capture of the greenhouse gases like CO2 etc.
Water pollutants: Water pollutants are the harmful chemicals or microorganism that serve the purpose of contaminating the water and making it unfit to be used as a natural resource.
Ganga Action Plan: Ganga Action Plan was an effort launched by the government of India 1985 aiming to reduce the pollution in the river Ganga. However, the river had already been damaged beyond repair.
Potable water: The water which is safe for the purpose of drinking is known as potable water.
NCERT Solutions for Class 8 Science
- Crop Production and Management
- Microorganisms: Friend and Foe
- Synthetic Fibres and Plastics
- Materials : Metals and Non-Metals
- Coal and Petroleum
- Combustion and Flame
- Conservation of Plants and Animals
- Cell Structure and Functions
- Reproduction in Animals
- Reaching the Age of Adolescence
- Force and Pressure
- Friction
- Sound
- Chemical Effects of Electric Current
- Some Natural Phenomena
- Light
- Stars and The Solar System
- Pollution of Air and Water