NCERT Class 8 Science Pollution Of Air And Water

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NCERT Book for Class 8 Science Chapter 18 Pollution of Air and Water

Class 8 Science students should refer to the following NCERT Book Chapter 18 Pollution of Air and Water in Class 8. This NCERT Book for Class 8 Science will be very useful for exams and help you to score good marks

Chapter 18 Pollution of Air and Water NCERT Book Class 8

 

POLLUTIION OF AIIR AND WATER

Paheli and Boojho were very excited to hear the news that Taj Mahal in Agra is now one of the seven wonders of the world. But they were disappointed to hear that the beauty of this monument in white marble is being threatened by air pollution in the area surrounding the Taj. They were eager to know if something can be done to fight the air and water pollution.

We are all aware that our environment is not what it used to be. Our elders talk about the blue sky, clean water and fresh air that was available in their times. Now the media regularly reports on the falling quality of the environment. We ourselves feel the impact of the falling quality of air and water in our lives. The number of people suffering from diseases of the respiratory system, for example, is steadily rising. We dread to imagine a time when clean air and water may no longer be available! You have learnt about the importance of air and water in your previous classes. In this chapter, we will study about the harmful changes taking place in our surroundings and their effects on our lives.

18.1 Air Pollution

We can survive for some time without food, but we cannot survive even for a few minutes without air. This simple fact tells us how important clean air is to us. One of your observations in the above activity could be the differences in the amount of smoke in the atmosphere. Do you know where the smoke could have come from? Addition of such substances to the atmosphere modifies it. 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 air pollution.

18.2 How does Air Get Polluted?

The substances which contaminate the air are called air pollutants. Sometimes, such substances may come from natural sources like smoke and dust arising from forest fires or volcanic eruptions. Pollutants are also added to the atmosphere by human activities. The sources of air pollutants are factories (Fig. 18.2), power plants, automobile exhausts and burning of firewood and dung cakes. Many respiratory problems are caused by air pollution. Let us now try to find out the substances or pollutants which are present in the polluted air. Have you noticed how rapidly the number of vehicles is increasing in our cities? Vehicles produce high levels of pollutants like carbon monoxide, carbon dioxide, nitrogen oxides and smoke (Fig. 18.3). 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. Boojho remembers seeing a thick fog-like layer in the atmosphere, especially during winters. This is smo which is made up of smoke and fog. 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. Many industries are also responsible for causing air pollution. Petroleum refineries are a major source of gaseous pollutants like sulphur dioxide andnitrogen dioxide. Sulphur dioxide is produced by combustion of fuels like coal in power plants. It can cause respiratory problems, including permanent lung damage. You have already studied about the burning of fossil fuels in Chapter 5. Other kinds of pollutants are chlorofluorocarbons (CFCs) which are used in refrigerators, air conditioners and aerosol sprays. CFCs damage the ozone layer of the atmosphere. Recall that the ozone layer protects us from harmful ultraviolet rays of the sun. Have you heard of the ozone hole? Try to find out about it. Thankfully, less harmful chemicals are now being used in place of CFCs.  In addition to the above mentioned gases, automobiles which burn diesel and petrol, also produce tiny particles which remain suspended in air for long periods (Fig. 18.3). They reduce visibility. When inhaled, they cause diseases. Such particles are also produced during industrial processes like steel making and mining. Power plants give out tiny ash particles which also pollute the atmosphere.

Activity 18.3 

Prepare a table using the pollutants mentioned above. You may even add more data to the following Table. Table 18.1 Air Pollutants Sources Effects

18.3 Case Study : The Taj Mahal

Over the past 2 decades, India’s most famous tourist attraction, Taj Mahal located in Agra (Fig. 18.4), has become a matter of concern. Experts have warned that pollutants in air are discolouring its white marble. So, it is not only living organisms that get affected by polluted air but non-living things like buildings, monuments and statues also get affected. The industries located in and around Agra like rubber processing, automobile, chemicals and especially the Mathura oil refinery, have been responsible for producing pollutants like sulphur dioxide and nitrogen dioxide. These gases react with the water vapour presen 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. 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. The Supreme Court has taken several steps to save the Taj. It has

18.4 Greenhouse Effect

You know that the sun’s rays warm the earth’s surface. A part of the radiation that falls on the earth is absorbed by it the role of carbon dioxide in plants. But if there is excess of CO2 in the air, it acts as a pollutant. Can you help Paheli find out the answer to her question? 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 anincrease 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.

Exercises

1. What are the different ways in which water gets contaminated ?

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

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

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.

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

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

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

(a) Carbon dioxide

(b) Sulphur dioxide

(c) Methane

(d Nitrogen

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

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

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

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


Please refer to attached file for NCERT Class 8 Science Pollution Of Air And Water

Chapter 01 Crop Production and Management
NCERT Class 8 Science Crop Production And Management
Chapter 02 Microorganisms: Friend or Foe
NCERT Class 8 Science Microorganisms Friend And Foe
Chapter 03 Synthetic Fibres and Plastics
NCERT Class 8 Science Synthetic Fibres And Plastics
Chapter 04 Materials Metals and Non-Metals
NCERT Class 8 Science Materials Metals And Non Metals
Chapter 05 Coal and Petroleum
NCERT Class 8 Science Coal And Petroleum
Chapter 06 Combustion and Flame
NCERT Class 8 Science Combustion And Flame
Chapter 07 Conservation of Plants and Animals
NCERT Class 8 Science Conservation Of Plants And Animals
Chapter 08 Cell Structure and Functions
NCERT Class 8 Science Cell Structure And Functions
Chapter 09 Reproduction in Animals
NCERT Class 8 Science Reproduction In Animals
Chapter 10 Reaching the Age of Adolescence
NCERT Class 8 Science Reaching The Age Of Adolescence
Chapter 11 Force and Pressure
NCERT Class 8 Science Force And Pressure
Chapter 12 Friction
NCERT Class 8 Science Friction
Chapter 14 Chemical Effects of Electric Current
NCERT Class 8 Science Chemical Effects Of Electric Current
Chapter 15 Some Natural Phenomena
NCERT Class 8 Science Some Natural Phenomena
Chapter 17 Stars and the Solar System
NCERT Class 8 Science Stars And The Solar System
Chapter 18 Pollution of Air and Water
NCERT Class 8 Science Pollution Of Air And Water
Other Topics Class 8 Science
CBSE Class 8 Science Activity A Forseful Story
CBSE Class 8 Science Activity A Friend Indeed
CBSE Class 8 Science Activity A Mouldy Party
CBSE Class 8 Science Activity A Surprising Fact
CBSE Class 8 Science Activity A Tree Study
CBSE Class 8 Science Activity Back to the Earth
CBSE Class 8 Science Activity Bring Back The Shine
CBSE Class 8 Science Activity Delightful Daydreams
CBSE Class 8 Science Activity Egg Pops Into a Bottle
CBSE Class 8 Science Activity Growing Up
CBSE Class 8 Science Activity How Does Sound Travel
CBSE Class 8 Science Activity I Can See it
CBSE Class 8 Science Activity I Can See My Sound
CBSE Class 8 Science Activity Inside Story
CBSE Class 8 Science Activity Interview
CBSE Class 8 Science Activity Is The Moon Growing
CBSE Class 8 Science Activity Its CO2 Again
CBSE Class 8 Science Activity Just for Fun
CBSE Class 8 Science Activity Lets Make Music
CBSE Class 8 Science Activity Lighter or Heavier
CBSE Class 8 Science Activity Make A Periscope
CBSE Class 8 Science Activity Make Your Little Movie
CBSE Class 8 Science Activity Making a Solar System Model
CBSE Class 8 Science Activity Mysterious Forces
CBSE Class 8 Science Activity Pitcher Power
CBSE Class 8 Science Activity Please Hear
CBSE Class 8 Science Activity Spore Magic
CBSE Class 8 Science Activity Stages of Human Reproduction
CBSE Class 8 Science Activity Story of Granny
CBSE Class 8 Science Activity Suno Suno
CBSE Class 8 Science Activity The Ball Bearing
CBSE Class 8 Science Activity The Puzzling Letters
CBSE Class 8 Science Activity The Story of Magdeberg Hemisphere
CBSE Class 8 Science Activity The Tug of War
CBSE Class 8 Science Activity Want to be a Snake Charmer
CBSE Class 8 Science Activity What Makes Water
CBSE Class 8 Science Activity Wndow to our Rish BioDiversity
CBSE Class 8 Science Poster Making

NCERT Book Class 8 Science Chapter 18 Pollution of Air and Water

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