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Conventional Sources of Energy: NBSE Class 11 Environment
Get notes, summary, questions and answers, MCQs, extras, and PDFs of Chapter 19 “Conventional Sources of Energy” which is part of NBSE Class 11 Environment Education. However, the notes should only be treated as references and changes should be made according to the needs of the students.
If you notice any errors in the notes, please mention them in the comments
Summary
The chapter discusses conventional sources of energy, which are exhaustible and non-renewable. These include coal, petroleum, natural gas, and firewood, which have formed over millions of years from the remains of plants and animals. Once used, they cannot be replaced. Firewood has been a primary source of energy throughout history, especially in rural areas, but it causes air pollution when burned.
Coal, formed from ancient forests, was once the dominant energy source. It is still used today for various purposes, such as producing coke, coal gas, and synthetic petroleum. However, burning coal releases harmful gases like carbon monoxide and sulphur dioxide, leading to air pollution, health problems, and environmental issues like acid rain. Coal mining also causes water pollution, habitat loss, and land degradation.
Petroleum, formed from marine plants and animals, has largely replaced coal as the main energy source. It is refined through fractional distillation into various products like petrol, diesel, and kerosene. Petroleum use, however, leads to air pollution and environmental damage. Oil spills are especially harmful to marine life, and burning petroleum releases pollutants that harm the atmosphere.
Natural gas, often found with petroleum, is another fossil fuel. Its compressed form, CNG, is used in vehicles and is considered a cleaner alternative to petrol and diesel.
The chapter also covers the environmental impacts of using these fuels. Deforestation for firewood leads to soil erosion and habitat loss. Burning fossil fuels contributes to air pollution, global warming, and climate change. Acid rain, caused by sulphur dioxide emissions, harms ecosystems and human health. Despite their widespread use, these sources of energy have significant environmental consequences.
Textbook solutions
Multiple-Choice Questions
1. Conventional sources of energy are also known as
A. Exhaustible sources of energy
B. Inexhaustible sources of energy
C. Renewable sources of energy
D. All of these
Answer: A. Exhaustible sources of energy
2. Which of the following is used for manufacturing of coke?
A. Petroleum
B. Carbon dioxide
C. Coal
D. Natural gas
Answer: C. Coal
3. Which of the following is not a consequence of coal mining?
A. Water pollution
B. Earthquake
C. Land degradation
D. Loss of animal habitats
Answer: B. Earthquake
4. Incomplete burning of coal produces the following gas
A. Ozone
B. Carbon dioxide
C. Carbon monoxide
D. Oxygen
Answer: C. Carbon monoxide
5. Which product is added to LPG (Liquefied petroleum gas), so as to detect leakage (if any)?
A. Compressed Natural Gas (CNG)
B. Petroleum Gas
C. Mercaptan
D. Butane
Answer: C. Mercaptan
Short Answer Questions
1. What are the conventional sources of energy?
Answer: The sources of energy which are exhaustible are called conventional sources of energy or non-renewable sources of energy. E.g. coal, natural gas, petroleum. These sources have been formed through a series of processes that lasted over millions of years. Once these fuels are used, they will not be available again.
2. What is refining of petroleum?
Answer: The process of separating crude petroleum into more useful fractions is called refining of petroleum.
3. What is fractional distillation?
Answer: Fractional distillation is the process used to separate crude petroleum into various useful fractions. It is done by heating crude petroleum to a temperature of 400°C or above in a furnace, and the vapours are fed into a tall fractionating column. As the vapours rise up the column, they condense at different levels according to their boiling points.
4. What is the main constituent of methane?
Answer: Methane mainly contains the hydrocarbon methane (CH₄), which burns easily to produce heat.
5. What is CNG?
Answer: The compressed form of natural gas is called Compressed Natural Gas (CNG). It is used in automobiles as a fuel.
6. What are the harmful effects of deforestation?
Answer:
- Deforestation leads to soil erosion.
- It causes destruction of habitats of animals and plants.
- Deforestation leads to floods and droughts.
- It also results in increased carbon dioxide levels in the atmosphere.
7. What do you mean by acid rain?
Answer: Acid rain is formed when sulphur dioxide (SO₂) and oxides of nitrogen released into the air react with water vapour to form sulphuric acid and nitric acid. These acids dissolve in rain and snow, leading to acid rain.
8. What are the effects of global warming on the atmosphere?
Answer: Global warming causes the lower atmosphere to become warmer. This leads to more water evaporating into the atmosphere, which further warms the Earth’s atmosphere. This increased warmth causes changes in climate and weather patterns.
9. What is the average temperature rise of the atmosphere in the last 200 years?
Answer: The average temperature of the atmosphere has risen by almost 1°C in the last 200 years.
Long Answer Questions
1. How were coal and petroleum formed?
Answer: Coal is believed to have been formed by the slow compression of forests that existed on Earth 300 million years ago. The intense heat and high pressure under the Earth converted plants into coal. This is why coal is called a fossil fuel.
Petroleum is formed from the dead remains of marine plants and animals which settled in the sea millions of years ago. Intense heat as well as pressure underneath and the presence of natural catalysts converted the remains into petroleum. This is the reason why petroleum is called a fossil fuel.
2. Explain the fractional distillation of petroleum.
Answer: The process of separating crude petroleum into more useful fractions is called refining of petroleum.
The refining of petroleum is done by the process of fractional distillation.
Crude petroleum is heated to a temperature of 400°C or above in a furnace. The vapours of petroleum are fed into a tall fractionating column near its bottom. As the vapours rise up the fractionating column, they lose heat and hence their temperature drops. Due to this difference in temperatures, these vapours with higher boiling points condense first. Similarly, the vapours with lower boiling points rise up and condense in different parts of the fractionating column.
3. Name and define the main types of coal.
Answer:
- Peat: Peat is the first stage of coal formation and contains a large amount of moisture and decaying plant material.
- Lignite: It is a brownish-black coal with high moisture content, used primarily for electricity generation.
- Bituminous: It is a medium grade of coal used for generating electricity and making coke for the steel industry.
- Anthracite: This is the highest grade of coal, hard and black, with the highest carbon content and few impurities. It is used for domestic heating and as a high-quality fuel.
4. What are the harmful effects of fossil fuels?
Answer:
- Air pollution: Fossil fuels like coal and petroleum release pollutants such as sulphur dioxide, nitrogen oxides, carbon dioxide, and carbon monoxide into the air, leading to respiratory problems and environmental issues like acid rain and global warming.
- Water pollution: Oil spills during the transportation of petroleum or its products pollute water bodies and kill marine life.
- Land degradation: Mining of coal leads to the degradation of land, destruction of animal habitats, and loss of vegetation.
- Health hazards: Fossil fuel mining and burning cause serious health issues like pneumoconiosis in miners and respiratory problems in people living near mining areas.
- Global warming: The excessive release of carbon dioxide due to burning fossil fuels leads to global warming and climate change.
5. What is thermal pollution?
Answer: Thermal pollution refers to the impairment of the quality of environmental air or water by raising its temperature. Thermal power stations contribute to thermal pollution in a big way.
Effects:
- The life process involves many chemical reactions, and the rate of these reactions varies with temperature changes. Apart from biochemical reactions, temperature is of great importance to physiology and control of reproductive cycles, digestion, and respiration rates of aquatic animals, particularly fish.
- Most species of fish can adapt themselves to a fairly wide range of water temperature, provided the temperature changes occur very slowly. A steep change in temperature is quite destructive. The temperature change not only affects the fish but also brings about changes in the aquatic ecosystem. Any disruption in the food chain will upset the whole system.
- When the temperature of the aquatic system rises, the metabolic processes taking place in the body of the fish become faster, and its need for oxygen and rate of respiration rise. At a specific temperature, death occurs due to the failure of essential cell processes.
6. Discuss the limitations of the petroleum fuel.
Answer:
- Since it is a non-renewable source of energy, it will last for a few decades.
- Leakage of LPG can form an explosive mixture into the air on catching fire.
- It catches fire easily because it is highly inflammable, so great precautions have to be taken while dealing with petroleum fuels.
- Burning of petrol in vehicles releases poisonous gases into the atmosphere.
- Incomplete combustion of petrol releases poisonous gases like carbon monoxide and carbon particles.
7. Explain the environmental consequences of: (a) Coal, (b) Petroleum.
Answer: (a) Coal:
- Coal mining activities cause water pollution up to a large distance surrounding it.
- Loss of animal habitats, vegetation, and land degradation are the primary results of coal mining.
- A lot of CO (carbon monoxide) gas is released when coal burns in insufficient oxygen, causing damage to human health.
- Combustion of coal releases CO₂ (carbon dioxide) gas, which causes the greenhouse effect in the atmosphere.
- Another toxic pollutant from the coal-burning process is sulphur dioxide, which is injurious to human beings and causes acid rain.
(b) Petroleum:
- During the combustion of petrol in cars or other vehicles, nitrogen dioxide, a poisonous gas, is produced, which is very harmful to humans and other animals.
- Sometimes during the transportation of petroleum (oil), it spills into water bodies or on land. Such accidents cause a great loss of living organisms in that area.
- The lead compounds emitted by vehicles are poisonous and pollute the air.
- The fossil fuels burnt in thermal power stations cause thermal pollution, which increases air and water temperature.
Think and Answer
1. Rohan thinks that global warming is a superstition of the scientists. It has no effect on human beings. How will you convince him that global warming is a grave threat?
Answer: I will tell Rohan that global warming is a scientifically proven phenomenon. It is not a superstition. The Earth’s atmosphere is becoming warmer due to increased carbon dioxide levels caused by human activities, such as burning fossil fuels. This rise in temperature leads to melting polar ice caps, rising sea levels, extreme weather events, and changes in agricultural patterns. These changes affect human beings directly through floods, droughts, and food shortages, proving that global warming is a grave threat.
2. Ridhima thinks that as India has vast reserves of coal, so it does not have to worry about the future. Do you think she is right? Why or why not?
Answer: Ridhima is not completely right. Although India has vast reserves of coal, it is a non-renewable resource. Once these reserves are exhausted, they cannot be replenished. Moreover, coal mining and burning cause significant environmental problems such as air pollution, land degradation, and global warming. Additionally, the increasing global shift towards renewable energy sources means that relying on coal may not be sustainable in the long run. Therefore, India needs to focus on alternative energy sources for the future.
Extras MCQs
1. What are conventional sources of energy also known as?
A. Renewable sources
B. Sustainable sources
C. Non-renewable sources
D. Unlimited sources
Answer: C. Non-renewable sources
Q. What is an example of a non-renewable source of energy?
A. Solar energy
B. Wind energy
C. Coal
D. Biomass
Answer: C. Coal
Q. Which of the following was the primary source of energy until the mid-19th century?
A. Coal
B. Petroleum
C. Firewood
D. Natural gas
Answer: C. Firewood
Q. What major event led to the search for new fuels like coal, oil, and natural gas?
A. World War I
B. The Industrial Revolution
C. The discovery of America
D. The invention of electricity
Answer: B. The Industrial Revolution
Q. What percentage of the world’s energy needs was supplied by coal in the early 20th century?
A. 50%
B. 60%
C. 80%
D. 30%
Answer: C. 80%
Q. Which country contributed over 70% to the increase in world annual coal production from 2005 to 2011?
A. India
B. United States
C. Russia
D. China
Answer: D. China
Q. What is a significant environmental consequence of burning coal?
A. Release of methane gas
B. Release of carbon monoxide
C. Reduction in global warming
D. Decrease in acid rain
Answer: B. Release of carbon monoxide
Q. What harmful gas is produced when coal burns in insufficient oxygen?
A. Carbon dioxide
B. Methane
C. Carbon monoxide
D. Sulphur dioxide
Answer: C. Carbon monoxide
Q. What is the primary source of coal in India?
A. Deep-sea mining
B. Open-cast mining
C. Recycling
D. Hydraulic fracturing
Answer: B. Open-cast mining
Q. What process is used to refine petroleum?
A. Cracking
B. Fractional distillation
C. Carbon capture
D. Hydrolysis
Answer: B. Fractional distillation
Q. Where in India has natural gas been recently discovered?
A. Rajasthan Desert
B. Ganges River Delta
C. Krishna-Godavari basin
D. Western Ghats
Answer: C. Krishna-Godavari basin
Q. What is the primary component of LPG (Liquefied Petroleum Gas)?
A. Ethane
B. Methane
C. Butane
D. Propane
Answer: C. Butane
Q. What additive is mixed with LPG to detect its leakage?
A. Chlorine
B. Ethanol
C. Mercaptan
D. Ammonia
Answer: C. Mercaptan
Q. What percentage of the world’s energy needs is currently supplied by coal?
A. 10%
B. 30%
C. 50%
D. 70%
Answer: B. 30%
Q. What dangerous environmental phenomenon can be caused by sulphur dioxide released from burning coal?
A. Global warming
B. Acid rain
C. Ozone depletion
D. Smog
Answer: B. Acid rain
Q. What is the main component of natural gas?
A. Methane
B. Ethane
C. Propane
D. Butane
Answer: A. Methane
Q. What is the compressed form of natural gas called?
A. LPG
B. LNG
C. CNG
D. RNG
Answer: C. CNG
Q. Which region in India has the highest amount of coal reserves?
A. Western
B. Eastern
C. Southern
D. North-Eastern
Answer: B. Eastern
Q. What percentage of the world’s proven reserves of crude oil does India have?
A. 2.8%
B. 0.4%
C. 5.0%
D. 0.8%
Answer: B. 0.4%
Q. What percentage of India’s oil demand is currently met through imports?
A. 50%
B. 44.9%
C. 70%
D. 10%
Answer: C. 70%
Q. What harmful environmental effect is caused by the combustion of coal due to the release of sulphur dioxide?
A. Global warming
B. Deforestation
C. Acid rain
D. Ozone depletion
Answer: C. Acid rain
Q. What is the main environmental concern associated with fly ash produced by coal combustion?
A. Soil erosion
B. Groundwater contamination
C. Greenhouse gas emissions
D. Acid rain
Answer: B. Groundwater contamination
Q. What greenhouse gas is primarily responsible for global warming?
A. Methane
B. Nitrous oxide
C. Carbon dioxide
D. Sulphur dioxide
Answer: C. Carbon dioxide
Q. What is one of the main causes of thermal pollution?
A. Automobile emissions
B. Coal mining
C. Thermal power stations
D. Deforestation
Answer: C. Thermal power stations
25. Which method of energy harnessing has no emissions in the environment?
A. Solar power
B. Geothermal power
C. Natural gas
D. Coal
Answer: B. Geothermal power
Extra Questions and Answers
1. What are conventional sources of energy or non-renewable sources of energy?
Answer: The sources of energy that are exhaustible are called conventional sources of energy or non-renewable sources of energy. These sources include coal, natural gas, and petroleum, which have been formed through processes lasting over millions of years. Once these fuels are used, they will not be available again.
Q. How was coal formed? Why is it called a fossil fuel?
Answer: Coal is believed to have been formed by the slow compression of forests that existed on Earth 300 million years ago. The intense heat and high pressure under the Earth converted these ancient plants into coal. This process, occurring over millions of years, is why coal is called a fossil fuel.
Q. What are the limitations of coal as a source of energy?
Answer:
- In the early part of the twentieth century, 80 per cent of the world’s energy requirements were supplied by coal. Today, coal supplies just 30 per cent of our energy needs.
- India has substantial reserves of coal, with about 76 per cent obtained from open-cast mining and the rest from underground mining.
- World annual coal production increased by 1,905 Mt or 32% in 6 years in 2011 compared to 2005, with over 70% of this increase occurring in China and 8% in India.
Q. What are the uses of coal?
Answer:
- It is used in the manufacture of coke.
- It is used in the manufacture of coal gas.
- It is used as a fuel.
- It is used as a source of organic compounds, such as benzene, toluene, anthracene, naphthalene, aniline, and phenol.
- It is used in the manufacture of synthetic petroleum.
Q. What are the environmental consequences of burning coal?
Answer:
- When coal burns in sufficient oxygen, it produces carbon dioxide gas (CO2). Although carbon dioxide is not toxic, its excess in the atmosphere is considered a pollutant because it leads to undesirable changes in the climate.
- When coal burns in insufficient oxygen, it produces carbon monoxide (CO), a poisonous gas that can cause severe health problems if inhaled, including death. Sleeping in a closed room with a coal fire burning inside on a cold winter night can lead to carbon monoxide poisoning.
- When coal burns, the sulphur present in it forms sulphur dioxide gas (SO2), which is poisonous and pollutes the air.
- Coal burning produces a lot of black smoke, which spoils clothes and blackens buildings.
Q. What are the environmental consequences of coal mining?
Answer:
- Coal mining activities cause water pollution over a large distance surrounding the mining area.
- Loss of animal habitats, vegetation, and land degradation are the primary results of coal mining.
- A lot of carbon monoxide (CO) gas is released when coal burns in insufficient oxygen, causing damage to human health.
- Combustion of coal releases carbon dioxide (CO2) gas, which contributes to the greenhouse effect in the atmosphere.
- Another toxic pollutant from coal-burning is sulphur dioxide (SO2), which is harmful to human health and causes acid rain.
Q. How is petroleum formed and why is it called a fossil fuel?
Answer: Petroleum is formed from the dead remains of marine plants and animals that settled in the sea millions of years ago. Intense heat and pressure beneath the Earth’s surface, along with natural catalysts, converted these remains into petroleum. This long process is why petroleum is called a fossil fuel.
Q. What is the process of refining petroleum?
Answer: The process of refining petroleum involves separating crude petroleum into more useful fractions through fractional distillation. Crude petroleum is heated to a temperature of 400°C or above in a furnace. The vapours of petroleum are fed into a tall fractionating column near its bottom. As the vapours rise up the column, they lose heat and condense at different levels based on their boiling points, separating into various fractions like petrol, kerosene, diesel, and more.
Q. What are the limitations of petroleum as a source of energy?
Answer:
- Since it is a non-renewable source of energy, petroleum will last only for a few decades.
- Leakage of LPG can form an explosive mixture with air if it catches fire.
- Petroleum catches fire easily because it is highly inflammable, requiring great precautions during handling.
- Burning of petrol in vehicles releases poisonous gases into the atmosphere.
- Incomplete combustion of petrol releases harmful gases like carbon monoxide and carbon particles.
Q. What are the environmental consequences of using petroleum?
Answer:
- During the combustion of petrol in cars or other vehicles, nitrogen dioxide, a poisonous gas, is produced, which is harmful to humans and animals.
- Oil spills during the transportation of petroleum can cause significant environmental damage, including the loss of living organisms in the affected area.
- Lead compounds emitted by vehicles using petroleum fuels are poisonous and contribute to air pollution.
- Fossil fuels burnt in thermal power stations cause thermal pollution, increasing air and water temperatures.
Q. What is petroleum gas, and how is it used?
Answer: Petroleum gas is obtained as a by-product during the refining of petroleum. It mainly consists of butane and other gases like ethane. In homes, it is used as Liquefied Petroleum Gas (LPG) for cooking. LPG catches fire easily and is odourless, making it difficult to detect leaks. To address this, a strong-smelling substance called mercaptan is mixed with LPG to help detect leaks.
Q. What is natural gas, and how is it used?
Answer: Natural gas is another fossil fuel found with petroleum in oil wells. It mainly contains methane, which burns easily to produce heat. The compressed form of natural gas is known as Compressed Natural Gas (CNG), which is used as fuel in automobiles.
Q. What environmental problems are associated with the high ash content of Indian coal?
Answer: Indian coal, with an ash content of around 40 per cent, generates large quantities of fly ash when used in power plants. Fly ash, which contains traces of heavy metals like SiO₂, Al₂O₃, and Fe₂O₃, can cause serious environmental problems, including contamination of groundwater and land degradation when disposed of in low-lying areas or disposal ponds near power plants.
Q. What are the environmental consequences of coal mining and its combustion?
Answer: Coal mining, whether underground or open-cast, pollutes water and air, affects the health of miners and nearby residents, and can cause land degradation. The combustion of coal releases noxious gases and particulate matter into the atmosphere, including sulphur dioxide, which leads to acid rain and respiratory problems in living beings. Coal dust generated by mining and the impurities removed from coal during washing also contribute to environmental pollution.
Q. What problems are associated with oil well drilling and oil spills?
Answer: Oil well drilling, even when done carefully, can release toxic chemicals, causing air and water pollution. Accidental explosions and leaks during exploration and production can lead to environmental disasters. Oil spills on land or in water kill creatures, particularly in the sea where they are especially dangerous to life-forms like coral and plankton that cannot escape. The processing of petroleum also produces solid wastes and when burned, petroleum products release pollutants such as oxides of nitrogen, sulphur dioxide, carbon monoxide, and carbon dioxide.
Q. What is thermal pollution, and how does it affect aquatic life?
Answer: Thermal pollution refers to the impairment of environmental air or water quality by raising its temperature. Thermal power stations are a major contributor to thermal pollution. The rise in temperature of aquatic systems speeds up metabolic processes in aquatic animals, especially fish, increasing their need for oxygen. If the temperature change is too steep, it can be destructive, disrupting the food chain and leading to the failure of essential cell processes, ultimately causing death in aquatic life.
17. What is the greenhouse effect, and how has it contributed to global warming?
Answer: The greenhouse effect is the warming of the Earth’s surface due to the trapping of the sun’s heat by the atmosphere, which acts like the glass in a greenhouse. Modern lifestyles have disrupted the natural balance of atmospheric gases, with exhaust gases from vehicles and power stations adding about 6 billion tonnes of carbon dioxide to the atmosphere. This extra CO₂ has caused the lower atmosphere to become warmer, contributing to global warming, with the average temperature of the atmosphere rising by almost 1°C in the last 200 years.
