Pollution of air and water explores the causes and effects of environmental contamination, focusing on sewage, industrial waste, and chemical runoff. This chapter provides multiple-choice questions, short-answer questions, and detailed explanations about water purification methods, the impact of pollutants like carbon monoxide and sulfur dioxide, and the concept of eutrophication. Ideal for students studying environmental science, it offers a comprehensive overview of pollution issues and solutions. Key topics include methods for making water potable, the dangers of acid rain, and strategies for conserving water resources.

Key Points

  • Explains the causes of water pollution, including sewage and industrial waste.
  • Discusses the effects of pollutants on human health and the environment.
  • Covers methods for purifying water, such as boiling and ultraviolet light.
  • Examines the concept of eutrophication and its impact on aquatic ecosystems.
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Chapter 19. Pollution of air and water Living science question with answer
A. MULTIPLE-CHOICE QUESTIONS: Choose the most appropriate answer.
1. Which of these causes water pollution?
a. sewage b. industrial waste c. fertilizers and pesticides d. all of these
2. Which of these processes cannot remove germs from water?
a. boiling b. filtration through porous pot c. reverse osmosis d. exposure to ultraviolet light
3. Which of these methods does not result in conservation of water?
a. using drip irrigation b. recycling of water
c. cutting vegetation so that less water is lost by transpiration d. planting more trees
4. Which of the following is not a pollutant unless present in excess?
a. sulphur dioxide b. carbon dioxide c. carbon monoxide d. nitrogen dioxide
5. Which of the following gases combines with the blood and prevents it from carrying oxygen?
a. carbon monoxide b. carbon dioxide c. nitrogen oxide d. nitrogen trioxide
6. Which of these can cause acid rain?
a. carbon monoxide b. carbon dioxide c. sulphur dioxide d. nitrogen
Ans : 1. d 2.b 3.c 4. b 5. a 6. c
B. VERY SHORT-ANSWER QUESTIONS: Give one-word answers.
1. Water is a renewable resource. By which process is water recycled in nature?
2. The substances that pollute water or air are called _________.
3. Sewage that is _____(treated/untreated) causes water pollution.
4. Hot water discharge into rivers from factories is also a pollutant. True or false?
5. Give one word for 'enrichment of water of a lake or pond by nutrients that leads to excessive plant growth'.
6. Can you safely drink potable water?
7. Name the kind of light that can kill germs.
8. Using less water and preventing water from getting polluted is called of water.
9. Which polluting gas prevents the blood from carrying oxygen?
10. Carbon dioxide is the only greenhouse gas. True or false?
11. Chlorofluorocarbons damage the layer in the atmosphere.
12. What is rain mixed with sulphuric acid or nitric acid called?
13. Which compound added to petrol to prevent engines from 'knocking' causes pollution of air?
14. Name one fuel that causes very little pollution.
Ans : 1. water cycle 2. pollutants 3. untreated 4. True 5. eutrophication 6. Yes
7. ultraviolet light 8. conservation 9. carbon monoxide 10. False 11. ozone 12. acid rain
13. lead 14. Compressed Natural Gas (CNG)
C. SHORT-ANSWER QUESTIONS (TYPE I): Answer in a sentence or two.
1. What harm can dumping of untreated sewage into a river cause?
Ans : Untreated sewage from homes is often disposed off into rivers. These wastes contain many harmful
microorganisms - bacteria, viruses, fungi and parasites that cause diseases such as diarrhoea, dysentery, cholera,
typhoid and jaundice.
2. Why is hot water discharge into rivers also considered as a cause of water pollution?
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Ans : The temperature of the waste water from factories that is discharged into rivers is often higher than the
temperature of the river water. The resultant increase in the river water temperature is itself a form of pollution as it
adversely affects aquatic plants and animals.
3. If water is filtered, it becomes free of all suspended impurities and hence potable. Do you agree? Give reasons.
Ans : I don't agree with statement that filtered water is potable because only solid impurities are filtered, it may still
have germs in it and hence, not potable.
4. Suggest two methods by which water can be made potable at home.
Ans : At home, water can be made potable by killing the germs in the following ways:
(i) Boiling: Boiling the water for 15-20 minutes kills all germs.
(ii) Purifier with ultraviolet light: A special type of light called ultraviolet light kills germs. It is used in several water
purifiers available in the market today.
5. What are the main causes of water pollution?
Ans : The main causes of water pollution are: (i) Sewage (ii) Industrial waste (iii) Fertilizers and pesticides
6. The use of CNG instead of diesel is being encouraged these days in vehicles. Why?
Ans : CNG (Compressed Natural Gas) reduces the emission of carbon particles and harmful gases
such as carbon monoxide. It has now become compulsory for all commercial vehicles in Delhi to use CNG. This has
reduced the pollution in the city.
7. What is the function of a catalytic converter?
Ans : To prevent vehicular pollution, new cars are fitted with a special system called catalytic converter. It can change
harmful exhaust gases like carbon monoxide and nitrogen dioxide into harmless carbon dioxide, nitrogen and water.
8. Name three greenhouse gases.
Ans: Carbon dioxide, methane and nitrous oxide.
9. What should be done to reduce water pollution due to sewage and industrial waste?
Ans : Treating sewage and factory wastes before disposing them off so that water sources are not polluted.
SHORT-ANSWER QUESTIONS (TYPE II): Answer in about 30 words.
1. Rivers have always been used to dump waste. How is it that pollution of rivers is becoming more alarming now than
it was earlier?
Ans : With an ever increasing human population and an increasing number of industries, the amount of waste which
goes into the water is very high. Therefore, the natural process of decay of the wastes can not cope with the amount
of waste dumped.
2. What are the cause and effects of eutrophication?
Ans : Excessive run off of fertilizers into water sources results in an increase in nutrients in water. This though a chain
reaction leads to excessive plant growth and depletion of oxygen in water. The condition is known as eutrophication. It
adversely affects the water plants and animals.
3. Give four methods of conserving water.
Ans : Some of the methods of water conservation are as follows: (i) Using less water and avoiding wastage at home.
(ii) Using better methods of irrigation. (iii) Recycling of water in factories and using it several times before it is disposed
off. (iv) Treating sewage and factory wastes before disposing them off (v) Water harvesting of rainwater to raise the
groundwater level
4. What is SPM? What harm does SPM pollution cause?
Ans : Minute solid particles suspended in air are known as suspended particulate matter or SPM. Unburnt carbon
particles given out during the burning of fuels or from the exhausts of vehicles, and fine particles of cement given out
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from a cement factory are examples of SPM. The finer of these particles cannot be filtered by the hair in our noses
and hence are a major cause of lung diseases. They also settle on plants and interfere with photosynthesis.
5. Why is carbon monoxide considered to be such a dangerous pollutant?
Ans : Carbon monoxide is one of the most dangerous pollutants. It is extremely poisonous. It mixes with the blood and
prevents it from carrying oxygen. It can even cause death due to lack of oxygen.
6. Carbon dioxide in air is essential as plants use it to make food. When does it become a pollutant? What damage
does it cause?
Ans : Carbon dioxide is produced whenever any fuel is burnt in homes and factories, or by automobiles. Carbon
dioxide itself is not a pollutant. However, since so much fuel is being burnt today, the carbon dioxide content in the air
is increasing. Also deforestation reduces the number of trees, which utilize carbon dioxide from air during
photosynthesis. This also contributes to increasing the percentage of carbon dioxide in the air. Excess carbon dioxide
in the atmosphere traps the heat of the sun. This is called the greenhouse effect. This is believed to cause an increase
of the temperature of the earth, called global warming.
7. What is acid rain? What is it caused by?
Ans : Rain mixed with sulphuric acid is called acid rain. Sulphur is present in coal as an impurity. Therefore, when coal
is burnt in homes, factories or power plants, sulphur dioxide is given off. Sulphur dioxide is poisonous. It affects our
lungs. It combines with the oxygen in the air to form sulphur trioxide (SO
3
). This reacts with water in the clouds to form
sulphuric acid (H
2
SO4.).
8. Give four ways in which air can be conserved.
Ans : Some of the methods of air conservation are as follows: Planting of trees is important for reducing air pollution.
(ii) Use of efficiently designed smokeless stoves. (iii) Use of smokeless fuels such as LPG and CNG. v) Fitting cars
with a special system called catalytic converter to prevent vehicular pollution. (v) Using electrostatic precipitators to
remove particles of solid such as carbon from waste gases before they are let out into the atmosphere.
E. LONG-ANSWER QUESTIONS: Answer in about 60 words.
1. How does the use of excess of fertilizers and pesticides affect water bodies?
Ans : Fertilizers and pesticides get washed off by rain into water sources. They also seep into the ground to pollute
groundwater. When fertilizers run off into water sources, they cause an increase in the growth of algae in water which
use up the dissolved oxygen from the water. When algae die, they become food for decomposers such as bacteria —
these also use the dissolved oxygen, thus reducing oxygen content even further. Their thick growth also stops sunlight
from reaching the water. This adversely affects the water plants and animals.
2. Discuss the different methods available to us for making water potable by killing germs.
Ans : Water can be made potable by any of the following methods:
(i) Boiling: Boiling the water for 15 - 20 minutes kills all germs.
(ii) Ultraviolet light: A special type of light called ultraviolet light kills germs.
(iii) Reverse osmosis: Water is passed through a semi-permeable membrane. It has fine pores through which water
can pass but not the solid impurities and the germs.
(iv) Chlorination: Chlorine added to water in the form of chlorine tablets or bleaching powder kills germs.
3. How is water treated at the waterworks to make it potable?
Ans : ap water supplied to our homes is made potable in the waterworks.
The, processes used are as follows:
(i) Sedimentation and decantation is first done to remove larger particles of solid impurities.
(ii) Alum is then added to the water to separate the smaller particles by making them heavier so that they settle down,
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FAQs

What are the main causes of water pollution?
The primary causes of water pollution include untreated sewage, industrial waste, and agricultural runoff containing fertilizers and pesticides. These pollutants introduce harmful microorganisms and chemicals into water bodies, leading to health risks for humans and wildlife. Sewage can carry diseases, while industrial waste may contain toxic substances that disrupt aquatic ecosystems. Understanding these causes is crucial for developing effective pollution control measures.
How does acid rain form and what are its effects?
Acid rain forms when sulfur dioxide and nitrogen oxides are released into the atmosphere, often from burning fossil fuels. These gases react with water vapor to create sulfuric and nitric acids, which then fall as precipitation. Acid rain can harm aquatic life by lowering the pH of water bodies, damaging fish populations and disrupting ecosystems. It also affects soil quality and can harm vegetation, leading to decreased agricultural productivity.
What methods can be used to purify water at home?
Water can be purified at home using several methods to ensure it is safe for drinking. Boiling water for 15-20 minutes effectively kills most germs and pathogens. Another method is using ultraviolet light, which can eliminate bacteria and viruses without altering the water's chemical composition. Additionally, reverse osmosis systems can filter out impurities, making water safe for consumption.
What is eutrophication and how does it affect water bodies?
Eutrophication is the process by which water bodies become enriched with nutrients, often due to runoff containing fertilizers. This nutrient overload leads to excessive growth of algae, which depletes oxygen levels in the water as the algae die and decompose. The resulting hypoxic conditions can kill fish and other aquatic organisms, disrupting the ecosystem and reducing biodiversity. Managing nutrient inputs is essential to prevent eutrophication.
What role do catalytic converters play in reducing air pollution?
Catalytic converters are devices installed in vehicles to reduce harmful emissions from exhaust gases. They convert toxic pollutants like carbon monoxide and nitrogen oxides into less harmful substances such as carbon dioxide and nitrogen. By facilitating these chemical reactions, catalytic converters significantly lower the amount of air pollution produced by vehicles, contributing to improved air quality in urban areas.
What are the health effects of carbon monoxide exposure?
Carbon monoxide is a colorless, odorless gas that can be extremely harmful when inhaled. It binds to hemoglobin in the blood, preventing oxygen from being transported effectively throughout the body. Symptoms of carbon monoxide poisoning include headaches, dizziness, confusion, and in severe cases, can lead to unconsciousness or death. Understanding the dangers of carbon monoxide is crucial for preventing exposure, especially in enclosed spaces.

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