RBSE Solutions Class 8 Science Chapter 16 Air and Water Pollution and its Control

Air and Water Pollution and its Control Textbook Questions Solved

I. Multiple Choice Questions

 

Question 1. Which of the following is not a greenhouse gas?
(a) Carbon dioxide
(b) Sulphur dioxide
(c) Methane
(d) Nitrogen
Answer: (b) Sulphur dioxide
In simple words: Sulphur dioxide is a pollutant, but it does not trap heat in the atmosphere like greenhouse gases do. Greenhouse gases keep our planet warm, but too much of them causes global warming.

🎯 Exam Tip: Remember the main greenhouse gases like carbon dioxide, methane, and nitrous oxide. Sulphur dioxide is known more for causing acid rain.

 

Question 2. Which of the following is a poisonous gas?
(a) Carbon monoxide
(b) Hydrogen
(c) Oxygen
(d) Nitrogen
Answer: (a) Carbon monoxide
In simple words: Carbon monoxide is a very dangerous gas because you cannot see or smell it, and it can make you very sick or even die if you breathe too much. It stops your blood from carrying oxygen properly.

🎯 Exam Tip: Know common poisonous gases and their effects. Carbon monoxide is particularly dangerous due to its odorless and colorless nature.

 

Question 3. It is used in the refrigerators:
(a) Hydrogen
(b) Chlorofluoro Carbon
(c) Nitrogen
(d) Oxygen
Answer: (b) Chlorofluoro Carbon
In simple words: Chlorofluorocarbons, or CFCs, were once widely used in fridges and aerosol cans. These chemicals are harmful because they damage the Earth's ozone layer, which protects us from harmful sun rays.

🎯 Exam Tip: Understand the role of CFCs in refrigerators and their negative impact on the environment, particularly the ozone layer. Look for current alternatives to CFCs.

 

Question 4. Holy river of India is:
(a) Ganga
(b) Bedach
(c) Banas
(d) Kosi
Answer: (a) Ganga
In simple words: The Ganga river is considered very sacred by many people in India. It is a very important river for both religious reasons and for supporting life along its banks.

🎯 Exam Tip: Identify important geographical features like major rivers, especially those with cultural or religious significance in India.

 

Question 3. is used in aerosol sprays.
Answer: C.F.C
In simple words: CFCs, or Chlorofluorocarbons, were once common in aerosol sprays. They were later found to harm the ozone layer, leading to their replacement with safer alternatives.

🎯 Exam Tip: Know the common uses of CFCs and why they are harmful to the environment. This helps understand efforts to protect the ozone layer.

 

Question 4. Clean drinking water is called
Answer: potable water
In simple words: Potable water is water that is safe and good for humans to drink. It means it has been cleaned and tested to remove anything harmful.

🎯 Exam Tip: Understand the term "potable water" and its importance for public health. Differentiate it from other types of water, such as tap water that might not be safe to drink without further purification.

 

Question 3. Match Column - A with Column - B

Answer:In simple words: This table links environmental terms and historical sites to their related concepts or problems. For example, "Marble Cancer" describes how acid rain damages marble, and the "Taj Mahal" is a famous historical building affected by pollution. "Save Ganga" is a plan for the Ganga river, and "Van Mahotsav" is about planting trees.

🎯 Exam Tip: When matching columns, read both columns carefully and identify direct relationships. Sometimes, the context of the terms can help you make the correct links.

Questions

 

Question 1. Mention the harmful effects of air pollution.
Answer: Harmful effects of air pollution include:
1. Incomplete burning of fuels like petrol and diesel releases carbon monoxide (CO), a poisonous gas that reduces the blood's ability to carry oxygen.
2. Tetraethyl lead in petrol is a dangerous substance that contributes to diseases like cancer and tuberculosis. This shows how tiny particles from fuel can have big impacts.
3. In winter, smog forms when fog mixes with smoke, containing nitrogen dioxide (NO2), which causes coughing and breathing problems.
4. Petrol refineries and power plants release harmful gases like NO2 and SO2. These pollutants are known to cause lung-related illnesses.
5. Chlorofluorocarbons (CFCs), used in refrigerators and air conditioners, damage the ozone layer, which protects Earth from harmful ultraviolet rays. An increased presence of CFCs has worsened the ozone depletion problem.
6. Industrial gases such as SO2, Cl2, NH3, and N2O can cause burning sensations in the eyes and throat.
7. Industries producing aluminum and superphosphate release toxic gases that lead to various health issues.
8. Air pollution also negatively affects plants, with SO2 even being capable of killing them.
In simple words: Air pollution makes it hard to breathe, causes many diseases like lung problems and cancer, and damages the ozone layer which protects us from the sun. It also harms plants and makes our environment unhealthy.

🎯 Exam Tip: When listing harmful effects, categorize them into human health, environmental, and material impacts to ensure comprehensive coverage. Provide specific examples of pollutants and their effects.

 

Question 2. What is global warming?
Answer: Global warming happens when too much carbon dioxide (CO2) builds up in the atmosphere. This excess CO2 acts like a blanket, trapping heat from the sun and preventing it from escaping back into space. As a result, the average temperature of the Earth's atmosphere is steadily increasing. This rise in global temperatures has far-reaching effects on our climate and ecosystems.
In simple words: Global warming means the Earth is getting hotter because too much carbon dioxide is trapping heat in the air, like a blanket, causing the planet's average temperature to rise.

🎯 Exam Tip: Define global warming clearly by explaining the role of carbon dioxide as a pollutant and its effect on trapping heat, leading to rising average temperatures. Mention the "greenhouse effect" implicitly.

 

Question 3. What is acid rain? How does it effect us?
Answer: Acid rain forms when gases like nitrogen, sulfur, and carbon dioxide mix with water in the atmosphere. These gases react to create acids such as sulfuric acid, nitric acid, nitrous acid, sulfurous acid, and carbonic acid. When rain falls, it carries these acids down to Earth, resulting in acid rain. This natural process is impacted heavily by industrial emissions.
Acid rain has several harmful effects: it damages buildings and monuments, especially those made of marble, making them corrode and lose their beauty. It also harms plants by damaging their leaves and changing the soil's composition, making it difficult for them to grow. Acid rain can also make lakes and rivers acidic, harming fish and other aquatic life. For humans, it can lead to respiratory problems when fine acid particles are inhaled.
In simple words: Acid rain happens when pollution from factories mixes with clouds, making the rain acidic. It damages buildings, harms plants and animals, and can cause breathing problems for people.

🎯 Exam Tip: Explain the formation of acid rain by naming the key gases (sulfur dioxide, nitrogen oxides) and their reaction with water. Detail its impacts on the environment (plants, water bodies), infrastructure (buildings), and human health.

 

Question 4. Write the methods to prevent air pollution.
Answer: Steps for controlling air pollution include:
1. Industrial chimneys should be fitted with gas absorbers to trap harmful gases before they are released. These devices are crucial for reducing factory emissions.
2. Pollutant particles should be removed from industrial exhausts using filters.
3. Combustion engines in vehicles should be regularly checked to ensure they are working efficiently and not emitting excessive pollutants.
4. Use cleaner, ideal fuels that produce less smoke and fewer harmful gases.
5. Waste gases and smoke should be treated (oxidized) before release to reduce pollution levels.
6. Industries should be located far away from residential areas to minimize exposure to pollutants.
7. Deforestation should be stopped, and more trees should be planted to absorb carbon dioxide and produce oxygen.
8. More and more trees should be planted through initiatives like afforestation drives.
9. Public awareness campaigns should be conducted to educate people about environmental cleanliness and the importance of reducing pollution.
10. Vehicles should use lead-free petrol, Compressed Natural Gas (CNG), and Liquefied Petroleum Gas (LPG) to reduce emissions. These cleaner fuels burn more completely.
11. Firecrackers should be banned during festivals like Diwali to lessen air pollution from smoke and toxic chemicals.
12. The government should regularly monitor air quality to keep track of pollution levels and implement necessary controls.
13. Alternative energy sources like wind, solar, and hydropower should be used to reduce dependence on fossil fuels. These sources are renewable and produce little to no pollution.
14. Large-scale tree planting events, like Van Mahotsav in July, should be encouraged.
15. Using personal vehicles less and opting for bicycles or public transport helps reduce vehicular pollution.
16. Garbage should be properly managed by composting organic waste instead of burning it, which releases harmful smoke.
In simple words: To stop air pollution, we should use cleaner fuels, check car engines, plant more trees, avoid burning garbage, and make sure factories clean their smoke before releasing it. We can also use clean energy sources like solar and wind power.

🎯 Exam Tip: Organize your answer by categorizing methods into technological solutions, behavioral changes, policy measures, and ecological approaches. Provide specific examples for each category.

 

Question 5. What is green house effect? Write its effect.
Answer: The greenhouse effect happens when certain gases in Earth's atmosphere trap heat. When carbon dioxide (CO2) increases in the atmosphere, it acts as a pollutant. This CO2 absorbs heat and prevents it from escaping into space, leading to a rise in the Earth's average temperature. This phenomenon is known as Global Warming, which is a significant environmental challenge. Besides CO2, other gases like methane, nitrous oxide, and water vapor are also greenhouse gases.
The main effect of the greenhouse effect is global warming, which causes the melting of glaciers worldwide. This melting leads to a rise in sea levels, potentially submerging coastal regions and islands. The far-reaching consequences include changes in rainfall patterns, affecting agriculture, forests, and overall ecosystems. This continuous rise in temperature creates an imbalance in natural systems. It affects weather patterns, leading to more extreme events like severe droughts or heavy floods. The shift in climate impacts animal habitats and the growth cycles of plants, threatening biodiversity.

🎯 Exam Tip: Explain the greenhouse effect clearly by describing how gases trap heat. Then, detail its primary effect (global warming) and its significant consequences, such as rising sea levels, changes in weather, and impacts on ecosystems.

Air and Water Pollution and its Control Long Answer Type Questions

 

Question 1. What is water pollution? What are the harms caused by water pollution? Write the methods to prevent water pollution.
Answer:
Water Pollution: Water pollution is the contamination of water with harmful substances that make it unsafe for living organisms. These harmful substances can come from various sources and disrupt natural aquatic ecosystems.
Causes of water pollution:
(a) Water becomes polluted when industrial waste, garbage, polythene, and other waste materials mix with it.
(b) Dirty water from rural drains often flows into ponds and rivers, adding to their pollution.
(c) Activities like washing clothes, bathing, washing utensils, dumping garbage, bathing animals, disposing of solid and liquid waste, and cleaning vehicles in ponds and rivers directly pollute the water.
(d) Pesticides and chemical fertilizers used in agriculture to boost crop growth can run off into rivers with rainwater, causing pollution.
(e) Polluted water also affects oceanic ecosystems, particularly from domestic atomic test explosions which contaminate the oceans with radiation.
Effect of water pollution:
Solid waste deposited in water bodies makes the water polluted. This polluted water contains various harmful microbes, fungi, and parasites. Drinking or using such water can lead to infections and diseases like cholera, diarrhea, and skin ailments. Additionally, polluted water reduces the amount of oxygen available for aquatic plants and animals, negatively impacting their growth and survival. This decrease in oxygen levels can lead to a reduction in their numbers over time. Polluted water also contaminates soil, reducing its fertility. Chemicals from oil refineries, paper, textile, and sugar industries, containing poisonous substances like lead, arsenic, and fluoride, mix with soil and water, making them toxic for animals and plants. Hot water released by electric plants and industries can increase the temperature of ponds, negatively affecting aquatic life by reducing dissolved oxygen. Pesticides and insecticides dissolved in water can also seep into underground water sources, contaminating them.
Measures to control water pollution:
(e) Solid and liquid waste should not be dumped near riverbanks and ponds.
(f) Water supply sources should be regularly checked and cleaned to ensure water quality.
(g) Domestic waste should be properly disposed of in designated areas, not into water bodies.
(h) Water purification plants should be installed at every rural and tehsil level to remove pollutants from water before it is supplied for use. This ensures a clean water supply for communities.
In simple words: Water pollution is when harmful things mix with water. This happens from factory waste, dirty drains, and chemicals from farms. It makes people sick, hurts fish and plants, and makes the soil bad. To stop it, we must not throw waste in rivers, clean water sources, and set up water cleaning plants.

🎯 Exam Tip: Structure your answer clearly into definition, causes, effects, and preventive measures. For causes and effects, provide specific examples of pollutants and their impact on different aspects like health, environment, and ecosystems.

 

Question 2. Write in detail about the danger over river Ganga.
Answer: The Ganga is considered one of India's holiest and most famous rivers. It is often referred to as Gangamata (Mother Ganga). Its water is traditionally believed to remain pure (potable) for extended periods. The river sustains a large population in North and East India, providing water for various needs. However, a study by the WWF (World Wildlife Federation) highlighted that the Ganga is among the ten rivers globally whose existence is currently at risk. Cities along the Ganga's banks contribute to its pollution by directly dumping garbage, untreated sewage, dead bodies, flowers, puja materials, and polythene. This continuous dumping is severely polluting the river daily. To address this crisis, the Ganga River Plan was launched in 1985. Despite these efforts, increasing population and industrialization have further harmed the river. Currently, the government has initiated an integrated plan called 'Namami Ganga' for its conservation. For this plan to be truly successful, it requires the active participation of all government departments and the general public. Everyone needs to work together to restore its purity. This collective effort is vital because the river holds immense cultural, environmental, and economic importance for millions of people.

🎯 Exam Tip: Discuss the Ganga's significance (holy, life-sustaining) and then detail the threats (urban waste, industrialization, population growth). Mention past and present conservation efforts like the Ganga River Plan and Namami Ganga, emphasizing the need for public participation.

Air and Water Pollution and its Control Additional Questions Solved

I. Multiple Choice Questions

 

Question 1. Chlorofluoro carbons are used in:
(a) Air conditioners
(b) Aerosol sprays
(c) Refrigerators
(d) All of the options
Answer: (d) All of the options
In simple words: Chlorofluorocarbons (CFCs) were commonly used in air conditioners, aerosol sprays, and refrigerators because of their properties. However, their use has been largely phased out due to their damaging effects on the Earth's ozone layer.

🎯 Exam Tip: Remember that CFCs were versatile chemicals used in various products. Understanding their multiple applications helps explain their widespread environmental impact before they were regulated.

 

Question 2. In which year Ganga Action Plan was launched?
(a) 1980
(b) 1984
Answer: (d) 1985
In simple words: The Ganga Action Plan, a big government project, was started in 1985 to clean up the Ganga River. This plan aimed to reduce pollution in one of India's most important rivers.

🎯 Exam Tip: When dealing with historical events or government initiatives, knowing the specific year or period of their launch is often crucial for exams.

 

Question 4. Water containing high salt concentration can be purified by
(a) Boiling
(b) UV radiation
(c) Filtration
(d) Reverse osmosis
Answer: (d) Reverse osmosis
In simple words: Reverse osmosis is a special way to clean water with a lot of salt. It pushes the salty water through a very fine filter, leaving the salt behind and giving you clean water. Boiling, UV, and filtration don't remove dissolved salts.

🎯 Exam Tip: Understand different water purification methods and what kind of impurities each method targets. Reverse osmosis is particularly effective for removing dissolved salts and minerals.

 

Question 5. Which of the following is major source of water pollution?
(a) Industrial Waste
(b) Untreated sewage
(c) Use of fertilizers
(d) Toxic materials
Answer: (b) Untreated sewage
In simple words: Untreated sewage is the biggest source of water pollution because it contains many harmful bacteria and organic matter. When released into water bodies, it uses up a lot of oxygen, harming aquatic life and making the water unsafe.

🎯 Exam Tip: Recognize the most significant contributors to water pollution. While industrial waste and toxic materials are dangerous, untreated sewage often represents the largest volume of contamination, especially in densely populated areas.

 

Question 6. The Taj Mahal is being affected due to
(a) Air pollution?
(b) Water pollution
(c) Radioactive pollution
(d) None of these
Answer: (a) Air pollution?
In simple words: The beautiful white marble of the Taj Mahal is getting discolored because of air pollution, especially from harmful gases like sulfur dioxide. These gases cause acid rain, which slowly damages the monument.

🎯 Exam Tip: Connect specific environmental problems to their visible impacts. The discoloration of the Taj Mahal is a classic example of how air pollution, particularly acid rain, affects historical monuments.

 

Question 7. Which of the following is not a pollutant?
(a) H2
(b) CO
(c) NO2
(d) SO2
Answer: (a) H2
In simple words: Hydrogen gas (H2) is not usually seen as a pollutant; in fact, it is considered a clean fuel source that produces only water when burned. Carbon monoxide, nitrogen dioxide, and sulfur dioxide, however, are common air pollutants.

🎯 Exam Tip: Differentiate between common pollutants and non-pollutants. Familiarize yourself with the chemical formulas of common gases to identify them correctly.

 

Question 9. Acid rain is caused due to increase in concentration of:
(a) SO2
(b) CO and CO2
(c) CO and SO2
(d) Ozone and dust
Answer: (d) Ozone and dust
In simple words: Acid rain is mostly caused by too much sulfur dioxide (SO2) and nitrogen oxides (NOx) in the air. These gases mix with water in the clouds to form acids, which then fall as rain.

🎯 Exam Tip: The primary gases responsible for acid rain are sulfur dioxide (SO2) and nitrogen oxides (NOx). Ensure you identify these specific pollutants rather than other general air contaminants.

 

Question 10. Which of the following type of pollution causes the out break of jaundice?
(a) Air pollution
(b) Water pollution
(c) Soil pollution
(d) Thermal pollution
Answer: (a) Air pollution
In simple words: Jaundice is often spread through contaminated water or food. So, water pollution is the main type of pollution that can lead to outbreaks of jaundice, as it affects the quality of our drinking water.

🎯 Exam Tip: Associate specific diseases with the type of pollution that causes them. Waterborne diseases like jaundice are commonly linked to water pollution.

 

Question 11. DDT is:
(a) Non-degradable pollutant
(b) Degradable pollutant
(c) Green house gas
(d) None of these
Answer: (a) Non-degradable pollutant
In simple words: DDT is a type of pesticide that does not break down easily in nature. This means it stays in the environment for a very long time, building up in living things and causing harm.

🎯 Exam Tip: Understand the difference between degradable and non-degradable pollutants. Non-degradable substances like DDT persist in the environment and can accumulate in food chains, posing long-term risks.

 

Question 12. Which of the following is the main factor of water pollution?
(a) Pesticides
(b) Industrial waste
(c) Detergent
(d) NH3
Answer: (b) Industrial waste
In simple words: Industrial waste is a major cause of water pollution because factories often release harmful chemicals and heavy metals directly into water bodies. These substances are very toxic and can severely damage aquatic ecosystems and human health.

🎯 Exam Tip: Identify the most impactful sources of pollution. While all options can pollute water, industrial waste often contains a highly concentrated and diverse mix of dangerous chemicals, making it a "main" factor.

 

Question 13. In cities like Bombay and Calcutta, the major air pollutants are:
(a) Ozone
(b) Carbon monoxide and oxides of sulphur
Answer: (b) Carbon monoxide and oxides of sulphur
In simple words: In large cities, a lot of cars and factories release carbon monoxide and sulfur oxides into the air. These gases are major pollutants that make the air unhealthy to breathe and contribute to smog.

🎯 Exam Tip: For urban air pollution, focus on pollutants commonly generated by vehicle exhaust and industrial activities, such as carbon monoxide, sulfur dioxide, and nitrogen oxides.

 

Question 15. The disease 'Minamata' is caused by poisoning
(a) Lead
(b) Zinc
(c) Mercury
(d) Copper
Answer: (c) Mercury
In simple words: Minamata disease is a severe illness caused by mercury poisoning. It first appeared in Japan after a factory released mercury into the bay, which then built up in the fish that people ate.

🎯 Exam Tip: Learn about specific environmental diseases and their causes. Minamata disease is a classic example of heavy metal poisoning from industrial pollution.

Air and Water Pollution and its Control Very Short Answer Type Questions

 

Question 2. Which phenomena causes global warming?
Answer: The greenhouse effect causes global warming.
In simple words: The greenhouse effect, where certain gases trap heat, is what makes our planet's temperature go up.

🎯 Exam Tip: Clearly state "greenhouse effect" as the phenomenon. It's the underlying process that leads to the symptom of global warming.

 

Question 3. Name two green house gases?
Answer: Two important greenhouse gases are carbon dioxide and methane.
In simple words: Carbon dioxide and methane are two gases that trap heat in the Earth's atmosphere.

🎯 Exam Tip: Always remember at least two primary greenhouse gases, such as carbon dioxide and methane, as they are frequently asked in exams.

 

Question 4. Name the two main types of pollution?
Answer: The two main types of pollution are:
1. Air Pollution
2. Water Pollution
In simple words: The two main ways our environment gets dirty are through air pollution and water pollution.

🎯 Exam Tip: This is a fundamental concept. Clearly list "Air Pollution" and "Water Pollution" as the primary categories, as they cover most environmental contamination issues.

 

Question 5. Name two gases which are responsible for acid rain?
Answer: Sulphur dioxide and nitrogen dioxide are two gases responsible for acid rain.
In simple words: Acid rain is caused by sulfur dioxide and nitrogen dioxide gases that mix in the air.

🎯 Exam Tip: For acid rain, always mention sulfur dioxide (SO2) and nitrogen dioxide (NO2) as these are the main culprits from burning fossil fuels.

 

Question 6. What is potable water?
Answer: Potable water is water that is safe and fit for drinking by humans.
In simple words: Potable water is simply water that is clean and safe enough for people to drink without getting sick.

🎯 Exam Tip: Provide a clear and concise definition. Emphasize "safe" and "fit for human consumption" as key characteristics of potable water.

 

Question 7. Which radiations are absorbed by atmospheric gas?
Answer: Atmospheric gases absorb infrared radiations.
In simple words: Gases in our air soak up heat rays, called infrared radiation, which helps keep the Earth warm.

🎯 Exam Tip: Understand the types of radiation involved in the greenhouse effect. Infrared radiation is the heat energy emitted from Earth that greenhouse gases absorb.

 

Question 8. What do you mean by "Van Mahotsav"?
Answer: Van Mahotsav is an annual tree-planting festival celebrated in India. It means "Festival of Forests" and aims to encourage people to plant more trees and raise awareness about forest conservation. It typically takes place in July.
In simple words: Van Mahotsav is a yearly tree-planting festival in India that encourages people to grow more trees and protect forests.

🎯 Exam Tip: Define "Van Mahotsav" by its purpose (tree planting, forest conservation) and its timing (annual festival, usually July). This highlights its role in environmental efforts.

 

Question 10. Which gas is responsible for Bhopal gas tragedy?
Answer: Methyl isocyanate (MIC) poisonous gas was responsible for the Bhopal gas tragedy.
In simple words: The deadly Bhopal gas tragedy happened because of a poisonous gas called Methyl Isocyanate, which leaked from a factory.

🎯 Exam Tip: For specific historical events like the Bhopal gas tragedy, identifying the exact chemical responsible is crucial. Methyl Isocyanate (MIC) is the key term here.

 

Question 11. How water can be purified?
Answer: Water can be purified through methods like filtration, boiling, and chlorination.
In simple words: We can clean water by filtering it, boiling it to kill germs, or adding chlorine to make it safe to drink.

🎯 Exam Tip: List common and effective household water purification methods. Filtration removes particles, boiling kills germs, and chlorination disinfects the water.

Air and Water Pollution and its Control Short Answer Type Questions

 

Question 1. What steps does government introduced to stop the air pollution in Delhi?
Answer: The government introduced several measures to reduce air pollution in Delhi, which include:
1. Promoting the use of unleaded petrol in vehicles.
2. Implementing Euro-II standards for vehicle emissions.
3. Encouraging the use of Compressed Natural Gas (CNG) instead of diesel and petrol in public transport systems. These efforts have significantly improved air quality and made Delhi a cleaner city. The shift to CNG for public transport was a landmark policy that drastically cut down vehicle emissions, demonstrating a strong commitment to environmental health.
In simple words: To clean Delhi's air, the government made cars use unleaded petrol, brought in better emission rules, and had public buses switch to cleaner CNG fuel. These steps really helped make the air better.

🎯 Exam Tip: When discussing government actions, name specific policies or initiatives, such as "unleaded petrol," "Euro-II standards," and "CNG for public transport," to show detailed knowledge.

 

Question 2. Why carbon dioxide is released too much in'the atmosphere?
Answer: Carbon dioxide (CO2) is released too much into the atmosphere primarily due to human activities, especially since the Industrial Revolution. This has happened for the following key reasons:
1. Burning fossil fuels: The combustion of fossil fuels like coal and oil in power stations, factories, and vehicles releases large amounts of CO2. These processes generate energy but also produce pollutants and greenhouse gases. Fossil fuels are a primary energy source globally, making their combustion a significant contributor to atmospheric CO2 levels.
2. Deforestation: The clearing of forests for agriculture, urbanization, and other purposes removes trees that absorb CO2 from the atmosphere. Fewer trees mean less CO2 is taken out of the air, leading to its accumulation. Forests act as vital carbon sinks, and their destruction reduces Earth's natural capacity to regulate CO2 levels.
In simple words: We release too much carbon dioxide into the air mostly by burning coal and oil for energy and by cutting down too many trees. Trees help soak up CO2, so losing them means more CO2 stays in the air.

🎯 Exam Tip: Focus on the two main human activities that increase atmospheric CO2: burning fossil fuels (for energy) and deforestation (reducing CO2 absorption). Explain how each activity contributes to the problem.

 

Question 3. Write two characteristics of chlorofluro carbons (CFCs)
Answer: Two characteristics of chlorofluorocarbons (CFCs) are:
1. They were widely used in refrigerators, air conditioners, and aerosol sprays due to their stable and non-toxic properties, which made them popular for many applications.
2. CFCs are known to damage the ozone layer in the Earth's atmosphere. This damage reduces the planet's protection against harmful ultraviolet radiation from the sun. Their chemical stability means they can reach the upper atmosphere and break down the ozone over a long period.
In simple words: CFCs were used in fridges and sprays. But they also hurt the Earth's ozone layer, which protects us from the sun.

🎯 Exam Tip: For CFCs, highlight their dual nature: their industrial utility (refrigerants, aerosols) and their significant environmental harm (ozone depletion). Both aspects are crucial for a complete answer.

 

Question 4. Why does the increased level of nutrients in the water affect the survival of aquatic organisms?
Answer: When fertilizers used in agriculture dissolve in water, they are washed into nearby water bodies. These fertilizers contain excessive amounts of nitrates and phosphates, which act as nutrients for algae. This abundance of nutrients causes algae to grow rapidly, leading to a phenomenon known as an algal bloom. When these algae eventually die, decomposers like bacteria feed on them. These bacteria use up a lot of oxygen from the water during decomposition, causing a significant decrease in the oxygen level. This reduced oxygen level is harmful to the survival of other aquatic organisms such as fish and insects, as they need dissolved oxygen to breathe. Without enough oxygen, these organisms cannot survive, leading to their decline or death and disrupting the entire aquatic ecosystem.
In simple words: Too many nutrients from farm fertilizers make algae grow fast in water. When these algae die, bacteria eat them and use up all the oxygen. This leaves no oxygen for other water animals, so they cannot live.

🎯 Exam Tip: Explain the process step-by-step: nutrient runoff -> algal bloom -> algal death -> bacterial decomposition -> oxygen depletion -> harm to aquatic life. This chain of events is known as eutrophication.

 

Question 5. Burning of fossil fuels causes pollution. Explain.
Answer: Fossil fuels like coal and petroleum are burned primarily to generate energy for various uses, including electricity and transportation. However, their combustion releases more than just energy and carbon dioxide. It also produces other poisonous gases, such as carbon monoxide, sulfur dioxide, and oxides of nitrogen, along with tiny smoke particles. These emissions significantly contribute to atmospheric pollution. These pollutants can cause respiratory problems, acid rain, and global warming. For instance, sulfur dioxide contributes to acid rain, which damages buildings and harms plant life. Carbon monoxide, a colorless and odorless gas, is toxic to humans and animals. This widespread release of harmful substances makes the burning of fossil fuels a major environmental concern, impacting air quality and public health globally.
In simple words: Burning fossil fuels like coal and oil gives us energy, but it also releases harmful gases like carbon monoxide and sulfur dioxide, plus tiny smoke particles. These make the air dirty and cause health problems and acid rain.

🎯 Exam Tip: Detail not only that pollution occurs but also *how* it occurs by listing specific pollutants (carbon monoxide, sulfur dioxide, nitrogen oxides) and their direct environmental impacts (respiratory issues, acid rain, global warming).

Air and Water Pollution and its Control Long Answer Type Questions

 

Question 1. Describe the threat to the beauty of the Taj Mahal.
Answer: Over the past two decades, the Taj Mahal, India's most famous tourist attraction located in Agra, Uttar Pradesh, has been a growing concern. Experts have warned that pollutants in the air are causing its beautiful white marble to become discolored. This shows that polluted air not only affects living organisms but also damages non-living things like buildings, monuments, and statues. Industries located in and around Agra, such as rubber processing, chemical manufacturing, and oil refineries, contribute significantly to this pollution. The phenomenon of the monument’s marble getting discolored is also known as "Marble Cancer." Suspended particulate matter, particularly soot particles from the Mathura oil refinery, has been a major factor in the yellowing of the marble. To protect the Taj Mahal, the Supreme Court has implemented several measures. It has ordered industries to switch to cleaner fuels like Compressed Natural Gas (CNG) and Liquefied Petroleum Gas (LPG). Additionally, automobiles in the Taj zone have been directed to use unleaded petrol. These efforts aim to reduce air pollution and preserve the iconic structure for future generations.
In simple words: Air pollution, especially from industries and vehicles near Agra, is harming the Taj Mahal's white marble, making it turn yellow. This damage is called "Marble Cancer." The government has ordered factories and vehicles to use cleaner fuels to save its beauty.

🎯 Exam Tip: Explain "Marble Cancer" and link it directly to air pollution, specifically industrial emissions (e.g., Mathura oil refinery) and vehicular pollution. Mention the government's specific remedial actions like promoting CNG and unleaded petrol.

 

Question 2. What is algal bloom? What are its harmful effects?
Answer: Algal bloom is an incident where chemical waste containing nitrates and phosphates mixes with water bodies like rivers and ponds. These chemicals act as powerful nutrients, causing a rapid and excessive growth of algae. This rapid multiplication of algae covers the water surface. The harmful effects of an algal bloom are significant. When these large quantities of algae die, they are decomposed by bacteria and other microorganisms. During this decomposition process, these microorganisms consume a large amount of oxygen present in the water. This leads to a severe decrease in the oxygen level, creating an anoxic or hypoxic environment. Such low oxygen levels are fatal for most aquatic organisms, including fish, insects, and other animals, causing them to die due to lack of oxygen. The reduction in biodiversity and the foul smell from decaying algae further degrade the water body, making it unsuitable for recreation and other uses. The death of aquatic organisms disrupts the entire food web and can lead to long-term ecological damage, making it challenging for the ecosystem to recover.
In simple words: Algal bloom is when too much chemical waste makes algae grow very fast in water. When these algae die, they use up all the oxygen in the water, killing fish and other water animals.

🎯 Exam Tip: Define algal bloom by linking it to nutrient excess (nitrates, phosphates) and rapid algal growth. Explain its harmful effects by detailing the process of oxygen depletion (eutrophication) and its consequences for aquatic life and water quality.

 

Question 3. Why is it necessary to purify the water? Explain the different methods for purifying water.
Answer: It is necessary to purify water because natural sources like rivers and lakes often contain many chemicals, pathogens (disease-causing microorganisms), and other pollutants. Therefore, the water supplied to homes must be purified before it is safe for human consumption. Water purification is crucial because clean water prevents waterborne diseases and ensures public health. Municipal authorities use various methods for water purification at the city level, and individuals can further purify water at home. The water supplied to homes for domestic purposes may still not be completely fit for drinking. Water that is safe for human consumption is called potable water. Potable water is free from pollutants, impurities, and pathogens; it is clean, clear, transparent, odorless, and pleasant to taste, with the desired quantity of oxygen and dissolved salts. Since there's no simple way to determine water purity, further purification before drinking is advisable.
Water purification methods at the Municipality:
(a) Sedimentation: This process involves allowing water to stand still so that heavier suspended particles settle down at the bottom.
(b) Filtration: After sedimentation, water is passed through layers of sand and gravel to remove smaller suspended particles.
(c) Disinfection: Chemicals like chlorine are added to kill any remaining harmful microorganisms in the water.
Some methods used for domestic and industrial purification of water are:
(a) Boiling: Heating water to a high temperature kills most bacteria and viruses.
(b) Carbon filtering: Activated carbon filters remove impurities, odors, and tastes from water.
(c) Distillation: This involves boiling water and collecting the steam, which is then condensed back into liquid. This process removes most impurities and salts.
(d) Reverse osmosis: This method forces water through a semi-permeable membrane, effectively removing dissolved salts, minerals, and other impurities.
In simple words: We need to clean water because natural water sources have germs and dirt. City plants use sedimentation, filtration, and chlorine to clean water. At home, we can boil water, use carbon filters, distill it, or use reverse osmosis to make it safe to drink.

🎯 Exam Tip: Start by explaining *why* purification is necessary (contaminants, health). Then, clearly separate and describe municipal-level methods (sedimentation, filtration, disinfection) from domestic/industrial methods (boiling, carbon filtering, distillation, reverse osmosis), providing a brief function for each.

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