Science | Class 10 | Chapter 14: Sources of Energy

Science | Class 10 | Chapter 14: Sources of Energy | Question Bank Solutions SEBA.

Chapter: Sources of Energy.

A. MCQ & Very Short Questions (Mark : 1)

Q1. Which of the following is not a conventional source of energy? [HSLC’16]
(a) Fossil fuels
(b) Bio-Mass
(c) Nuclear energy
(d) Wind energy

Answer:
(d) Wind energy ✅
Wind energy is a non-conventional source, whereas fossil fuels, biomass, and nuclear energy are conventional.

Q2. Which of the following is not derived from energy of the sun? [HSLC’18, ’24, ’25]
(a) Biomass
(b) Nuclear energy
(c) Geothermal energy
(d) Wind energy

Answer:
(b) Nuclear energy ✅
Nuclear energy comes from nuclear fission, not from the sun’s energy.

Q3. Which of the following is not an example of a bio-mass energy source? [HSLC’19]
(i) Wood
(ii) Nuclear energy
(iii) Gobar gas
(iv) Coal

Answer:
(ii) Nuclear energy ✅
Nuclear energy does not come from biomass; wood, gobar gas, and coal are biomass-based.

Q4. Which one of the following is an example of non-conventional source of energy? [HSLC’22]
(i) Fossil fuels
(ii) Bio-mass
(iii) Hydropower plants
(iv) Solar energy

Answer:
(iv) Solar energy ✅
Solar energy is a renewable, non-conventional source.

Q5. Which of the following is a conventional source of energy? [HSLC’23]
(a) Wave energy
(b) Nuclear energy
(c) Geo-thermal energy
(d) Wind energy

Answer:
(b) Nuclear energy ✅
Nuclear energy is widely used and considered a conventional source.

Q6. From the energy flow diagram, it is confirmed that the flow of energy is [HSLC’24]
(a) unidirectional
(b) multidirectional
(c) upward in air
(d) downward in water

Answer:
(a) Unidirectional ✅
Energy always flows in one direction — from source to sink.

Q7. Which of the following is not a renewable source of energy? [HSLC’24]
(a) Sun
(b) Wind
(c) Fossil fuel
(d) Water

Answer:
(c) Fossil fuel ✅
Fossil fuels are non-renewable because they take millions of years to form.

Q8. Which of the following processes explains the extraction of the sun's energy to generate energy to light a bulb? [HSLC’25]
(a) Conversion of electric energy into solar energy
(b) Conversion of solar energy into electric energy
(c) Conversion of solar energy into kinetic energy
(d) Conversion of kinetic energy into solar energy

Answer:
(b) Conversion of solar energy into electric energy ✅
Solar energy is converted into electricity to light the bulb.

Q9. Fill in the gaps:

(i) The hydrocarbon which is the major component of Compressed Natural Gas (CNG) is ______. [HSLC’23]
Answer: Methane ✅

(ii) When combustion takes place in insufficient air (or oxygen), ______ gas produces. [HSLC’23]
Answer: Carbon monoxide (CO) ✅

Q10. What is the approximate percentage of methane in bio-gas? [HSLC’23]
Answer:
About 55% to 70%

B. Short Type Questions (Mark: 2/3/5)

Q1. Distinguish between fossil fuel and solar energy as direct sources of energy. [HSLC’15]

Answer:

Basis	Fossil Fuels	Solar Energy
Source	Derived from dead plants and animals buried under the Earth for millions of years.	Directly obtained from the Sun’s radiation.
Type	Non-renewable source of energy.	Renewable source of energy.
Pollution	Causes air pollution due to carbon emissions.	Pollution-free and eco-friendly.
Availability	Limited and exhaustible.	Abundant and inexhaustible.
Examples	Coal, petroleum, natural gas.	Solar panels, solar cookers.

Q2. Write a short note on any one of the following:

(a) Hydro Power Plant
(b) Solar Cooker
[HSLC’16]

Answer (a) Hydro Power Plant):
A hydro power plant converts the kinetic energy of flowing or falling water into electrical energy.

Water stored in a dam is released, which drives turbines connected to generators.
It is a renewable and pollution-free source of energy.
Examples: Bhakra Nangal Dam, Tehri Dam.

Answer (b) Solar Cooker:
A solar cooker uses solar energy to cook food.

It has a box painted black from inside with a glass cover to trap heat.
Sunlight is concentrated into the box using mirrors, raising the temperature for cooking.
It saves fuel, is eco-friendly, but cannot be used at night or on cloudy days.

Q3. What are the energy potentials from the sea? Mention the limitation of any one of them. [HSLC’16]

Answer:
The sea offers three main energy potentials:

Tidal Energy – Generated from the rise and fall of tides.
Wave Energy – Produced by the kinetic energy of moving waves.
Ocean Thermal Energy – Generated using temperature differences between surface water and deep water.

Limitation (Tidal Energy):

Suitable only in coastal areas where tidal variations are high.
Construction of tidal power plants is expensive.

Q4. Why are we looking at alternative sources of energy? Name a non-conventional source of energy and its two advantages. [HSLC’18]

Answer:
We need alternative sources of energy because:

Fossil fuels are limited and exhaustible.
Burning fossil fuels causes pollution and global warming.

Example: Solar Energy ✅

Advantages of Solar Energy:

It is renewable and available in abundance.
It is eco-friendly and causes no pollution.

Q5. What are the qualities of an ideal source of energy? Give the names of two energy sources that you would consider to be exhaustible. [HSLC’19]

Answer:
Qualities of an Ideal Energy Source:

Provides a large amount of energy per unit volume.
Economical and easily available.
Easy to store and transport.
Should be safe, eco-friendly, and cause minimal pollution.

Examples of Exhaustible Energy Sources:

Coal
Petroleum

Q6. Can any source of energy be pollution-free? Why and why not? State two limitations of the energy that can be obtained from the oceans. [HSLC’20]

Answer:

No source of energy is completely pollution-free, but some are almost pollution-free, like solar and wind energy, because they do not release harmful gases.
Even renewable sources cause some pollution during manufacturing and installation of devices.

Two Limitations of Ocean Energy:

Construction of plants for tidal, wave, or ocean thermal energy is very expensive.
Suitable only for specific coastal locations.

Q7. Give any two ways in which biodegradable substances would affect the environment. [HSLC’22]

Answer:

Excessive biodegradable waste leads to bad odor and air pollution during decomposition.
It can cause water pollution when dumped into rivers or ponds, reducing oxygen levels and harming aquatic life.

Q8. What is a solar cell panel? What are the advantages associated with solar cells? [HSLC’22]

Answer:
A solar cell panel is a device made of multiple photovoltaic cells that convert solar energy into electrical energy.

Advantages of Solar Cells:

They are eco-friendly and produce clean energy.
Low maintenance and suitable for remote areas.
Renewable and abundantly available.

Q9. Write two disadvantages of fossil fuels. [HSLC’23]

Answer:

Fossil fuels are exhaustible and may run out in the future.
Their combustion causes air pollution and contributes to global warming.

Q10. Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices. [HSLC’24]

Answer:
Energy Sources:

Coal
Petroleum

Reasons:

These are non-renewable sources formed over millions of years.
Their reserves are limited, and excessive use leads to depletion.

A. MCQ & Very Short Questions (Mark: 1)

Assertion and Reasoning Questions

Q1.

Assertion (A): In case of power generation, now emphasis is given to the renewable energy sources such as solar energy.
Reason (R): The world will face serious problems if we depend only on fossil fuel for power generation.

Options:
(a) Both (A) and (R) are true and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.

Answer:
(a) Both (A) and (R) are true and (R) is the correct explanation of (A). ✅
Renewable energy is promoted because fossil fuels are limited and cause pollution.

Q2.

Assertion (A): In hydro-electric projects, much water is spent.
Reason (R): In hydro-electric projects, the kinetic energy of the water falling from height is used to generate electrical power.

Answer:
(d) (A) is false but (R) is true. ✅
Water is not “spent” in hydro power plants; it is reused after generating electricity.

Q3.

Assertion (A): In generation of electrical power from fossil fuel, much pollution is produced.
Reason (R): In solar power plants, wind power projects, etc., no pollution occurs.

Answer:
(a) Both (A) and (R) are true and (R) is the correct explanation of (A). ✅
Fossil fuel-based power generation causes pollution, unlike solar and wind energy.

Q4.

Assertion (A): The generation cost of electrical power in hydro-electric projects is comparatively less.
Reason (R): In case of hydro-electric projects, the amount of generated power depends upon the quantity of water.

Answer:
(b) Both (A) and (R) are true but (R) is not the correct explanation of (A). ✅
Hydro power is cheaper, but its cost advantage is not directly linked only to water quantity.

Q5.

Assertion (A): Biomass and bio-gas may be a good source of electrical power generation.
Reason (R): Such power plants help in waste management also.

Answer:
(a) Both (A) and (R) are true and (R) is the correct explanation of (A). ✅
Biogas plants convert organic waste into energy, helping manage waste and produce electricity.

Multiple-Choice Questions

Q6. The product of petroleum which has the greatest demand is:

(a) Kerosene
(b) Gasoline
(c) Diesel
(d) Fuel oil

Answer:
(c) Diesel ✅
Diesel is widely used in vehicles, industries, and power generators.

Q7. The amount of carbon present in Anthracite coal is:

(a) 65%
(b) 78%
(c) 95%
(d) 99%

Answer:
(c) 95% ✅
Anthracite is the hardest and purest form of coal with about 95% carbon.

Q8. In 1867 the oil drilling in Assam is first done in a place:

(a) Digboi
(b) Duliajan
(c) Makum
(d) Bongaigaon

Answer:
(a) Digboi ✅
Digboi, Assam, is known as the birthplace of the oil industry in India.

Q9. The crude oil is subjected to pyrolysis to:

(a) Make it convenient to carry
(b) Increase the calorific value
(c) Remove the impurities
(d) Increase the amount of petrol

Answer:
(c) Remove the impurities ✅
Pyrolysis of crude oil helps break down complex hydrocarbons and remove impurities.

Q10. The gas which is formed from the deposition of sea microbes at the bottom of the sea is:

(a) Natural gas
(b) Hydrogen gas
(c) Gasoline
(d) LPG

Answer:
(a) Natural gas ✅
Natural gas is formed from decomposed marine microorganisms trapped under sediments.

Q11. Which of the following types of coal contains less amount of carbon?

(a) Brown coal
(b) Sub-bituminous coal
(c) Bituminous coal
(d) Anthracite coal

Answer:
(a) Brown coal ✅
Brown coal (lignite) has the lowest carbon content and highest moisture among all coal types.

Q12. The chief component of natural gas is:

(a) Methane
(b) Ethane
(c) Propane
(d) Butane

Answer:
(a) Methane ✅
Natural gas primarily consists of methane (CH₄), about 85-95%.

Q13. The position of India, based on the number of nuclear power reactors, is:

Answer:
India ranks 5th/6th in the world in terms of the number of nuclear power reactors.

A. MCQ & Very Short Questions (Mark: 1)

Q1(ix). Why is cracking of crude oil?

(a) It is easily transportable
(b) To increase calorific value
(c) To remove impurity
(d) Increase production of petrol

Answer:
(d) Increase production of petrol ✅
Cracking breaks heavy hydrocarbons into lighter ones, increasing petrol output.

Q1(x). LPG is conserved at:

(a) Low temperature
(b) High pressure
(c) In presence of catalyst
(d) None of the above

Answer:
(b) High pressure ✅
LPG is stored in cylinders under high pressure to keep it liquid.

Q1(xi). The fuel of future use:

(a) CNG
(b) Hydrogen
(c) Petrol
(d) Gasohol

Answer:
(b) Hydrogen ✅
Hydrogen is a clean, renewable, and pollution-free fuel.

Q1(xii). Which of the following is a renewable source of energy?

(a) Hydro energy
(b) Wind energy
(c) Ocean energy
(d) Coal

Answer:
(a) Hydro energy, (b) Wind energy, and (c) Ocean energy ✅
All three are renewable, but coal is non-renewable.

Q1(xiii). Which one of the following is a non-conventional source of energy?

(a) Hydro energy
(b) Wind energy
(c) Ocean energy
(d) Coal

Answer:
(b) Wind energy ✅
Wind energy is a modern, non-conventional source, unlike coal and hydro power.

Q1(xiv). A solar cell is made of:

(a) An alloy
(b) A conducting material
(c) A semiconducting material
(d) An insulating material

Answer:
(c) A semiconducting material ✅
Solar cells are made of semiconductors like silicon.

Q1(xv). Fuel used in thermal power plants is:

(a) Water
(b) Uranium
(c) Biomass
(d) Fossil fuels

Answer:
(d) Fossil fuels ✅
Coal, oil, and natural gas are the main fuels in thermal power plants.

Q1(xvi). The chief constituent of biogas is:

(a) Methane
(b) Carbon dioxide
(c) Hydrogen
(d) Hydrogen sulphide

Answer:
(a) Methane ✅
Biogas contains 55–70% methane, which is its main component.

2. Fill in the blanks

(i) The main constituent of all fuels is carbon.

(ii) Fuel is a substance from which heat and energy can be prepared.

(iii) Fuels should have an appropriate calorific value.

(iv) For internal combustion engines, petrol is an ideal fuel.

(v) When Bituminous coal is burnt in absence of air, coke is produced.

(vi) The main process of Petroleum Refining is fractional distillation.

(vii) Coal is produced from plants by carbonization process.

(viii) The process by which the different constituents of petroleum are separated is called fractional distillation.

(ix) The amount of petroleum can be increased in crude oil by cracking process.

(x) To detect the leakage in LPG cylinder, a small amount of ethyl mercaptan is mixed up.

(xi) The process by which nuclear energy is transformed into electrical energy is called nuclear fission.

(xii) The main constituent of natural gas is methane.

(xiii) Coal, petroleum, and natural gas are fossil fuels.

(xiv) One of the most efficient and pollution-free sources of energy is solar energy.

(xv) The share of carbon in bituminous coal is about 78%.

(xvi) In India, presently 24 nuclear power reactors are working actively. (Approximate value as of HSLC reference.)

(xvii) By application of windmill technique, the wind energy is converted into electric energy.

(xviii) The Sun produces nuclear fusion reactions.

(xix) The photovoltaic cells directly convert solar energy into electricity.

3. From the following, find out the correct statements. Rewrite the wrong ones by correcting them.

(i) More smoke is released due to combustion of anthracite coal.
Answer: ❌ Incorrect

Correction: Less smoke is released due to combustion of anthracite coal because it has very high carbon content (~95%) and burns cleanly.

(ii) Sub-bituminous coal contains 80% carbon.
Answer: ❌ Incorrect

Correction: Sub-bituminous coal contains around 70% carbon, not 80%.
(Anthracite has the highest carbon content at ~95%, bituminous ~78%, sub-bituminous ~70%, and lignite ~60%.)

(iii) The fossil fuels are pollution free.
Answer: ❌ Incorrect

Correction: Fossil fuels are not pollution-free. Their combustion releases harmful gases like CO₂, CO, SO₂, and nitrogen oxides, which cause air pollution and global warming.

(iv) Tidal air is free from pollution and renewable.
Answer: ✅ Correct
Tidal energy is indeed renewable and pollution-free.

(v) Coal is an example of renewable source of energy.
Answer: ❌ Incorrect

Correction: Coal is a non-renewable source of energy because it takes millions of years to form and cannot be replenished quickly.

3. What is fuel?

Answer:
Fuel is any substance that can be burnt or otherwise used to produce energy in the form of heat or power. Fuels are mainly composed of carbon and hydrogen and, when burned, release energy through chemical reactions.
Example: Coal, petrol, diesel, natural gas, and wood.
(HSLC)

4. What is primary fuel?

Answer:
Primary fuel is a naturally occurring fuel that is obtained directly from nature and used in its natural form to produce energy.
Examples:

Coal
Crude oil
Natural gas
Wood
These fuels require little or no processing before use.
(HSLC)

5. What is secondary fuel?

Answer:
Secondary fuel is the fuel derived or processed from primary fuels to make them more efficient or convenient to use.
Examples:

Petrol and diesel (derived from crude oil)
Kerosene
LPG
Charcoal (from wood)
(HSLC)

6. What is calorific value?

Answer:
Calorific value is the amount of heat energy produced when one kilogram or one litre of a fuel is completely burnt in the presence of oxygen. It is measured in kilojoules per kilogram (kJ/kg) or kilojoules per litre (kJ/L).
Example:

The calorific value of LPG ≈ 55,000 kJ/kg.
(HSLC)

7. Which fuel has the highest calorific value?

Answer:
Among common fuels, hydrogen has the highest calorific value.

Calorific value of hydrogen ≈ 1,50,000 kJ/kg.
After hydrogen, LPG and natural gas also have high calorific values.
(HSLC)

8. What are the best fuels to use at home?

Answer:
The best fuels for domestic use should be:

Clean and smokeless
Have a high calorific value
Easy to store and transport
Safe and economical
Examples of best domestic fuels: LPG, natural gas, and electricity.
(HSLC)

9. Why patrol cannot be used as domestic fuel?

Answer:
Petrol cannot be used as a domestic fuel because:

It is highly volatile and catches fire easily.
Produces harmful gases on burning.
Costlier compared to other domestic fuels.
It poses a high risk of explosion in confined spaces.
(HSLC)

10. What is peat?

Answer:
Peat is the first stage in the formation of coal. It is a brownish substance formed by the partial decomposition of plant material in waterlogged conditions.

It contains about 60% carbon.
Produces less heat and more smoke.
(HSLC)

11. What is carbonization?

Answer:
Carbonization is the process by which plant materials are converted into coal under high temperature and pressure over millions of years.

The carbon content gradually increases from peat → lignite → bituminous coal → anthracite.
(HSLC)

12. From which coal after distillation we get coke?

Answer:
Coke is obtained from bituminous coal by the process of destructive distillation in the absence of air.

Coke is a solid, porous, and carbon-rich substance used in iron and steel industries.
(HSLC)

13. Which coal gives maximum heat?

Answer:
Anthracite coal gives the maximum heat.

It has the highest carbon content (90% or more).
Produces very little smoke.
Known as the best quality coal.
(HSLC)

14. Calorific value of coke is higher or lower than coal – Explain.

Answer:
The calorific value of coke is higher than that of coal because:

Coke is almost pure carbon (about 98% carbon).
It burns without smoke and produces more heat per kilogram compared to normal coal.
(HSLC)

15. Which substance is known as liquid gold?

Answer:
Petroleum is known as liquid gold because:

It is extremely valuable and has a wide range of uses.
It is used to produce fuels like petrol, diesel, LPG, and kerosene.
Also used in plastics, lubricants, medicines, fertilizers, and cosmetics.
(HSLC)

16. Where does the large layers of petroleum deposits are found?

Answer:
Large petroleum deposits are mainly found deep under sedimentary rocks beneath land and sea beds.
In India, major petroleum fields are found in:

Assam (Digboi, Duliajan)
Gujarat (Ankleshwar, Cambay)
Mumbai High (offshore)
Andhra Pradesh and Tamil Nadu coasts
(HSLC)

18. What do you mean by Refining of Petroleum?

Answer:
Refining of petroleum is the process of separating crude oil into useful components or fractions based on their boiling points. Crude oil contains a mixture of hydrocarbons and impurities, and through refining, it is converted into valuable products like petrol, diesel, kerosene, LPG, lubricants, and other petrochemicals.
HSLC

19. What is the main method for refining of petroleum?

Answer:
The main method for refining petroleum is fractional distillation.

Crude oil is heated in a distillation column.
Different components separate based on their boiling points.
Lighter fractions like LPG come out at the top, while heavier products like diesel, lubricants, and bitumen are collected at the bottom.
HSLC

20. What are the different derivatives obtained after processing of natural gas?

Answer:
The main derivatives obtained from natural gas are:

Methane (CH₄) – used as fuel and to make chemicals.
Ethane (C₂H₆) – used in petrochemical industries.
Propane (C₃H₈) – used in LPG cylinders.
Butane (C₄H₁₀) – used as fuel and in making LPG.
Natural Gas Liquids (NGLs) – used in plastics and synthetic fibers.
HSLC

21. Name one constituent of the fuel mixture used in jet planes.

Answer:
One major constituent of the fuel mixture used in jet planes is kerosene, also known as aviation turbine fuel (ATF).
HSLC

22. What is the main component of L.P.G.?

Answer:
The main component of Liquefied Petroleum Gas (LPG) is butane. It may also contain a small amount of propane.
HSLC

23. What is the name of the compound used to detect leakage of L.P.G.?

Answer:
The compound used to detect leakage of LPG is ethyl mercaptan (C₂H₅SH). It has a strong foul smell, making leakage easily noticeable.
HSLC

24. Why is L.P.G. considered to be an excellent fuel?

Answer:
LPG is considered an excellent fuel because:

It has a high calorific value.
It burns completely without producing smoke.
It is easily transportable in liquid form.
It leaves no residue or ash after burning.
HSLC

25. What is the main component of natural gas?

Answer:
The main component of natural gas is methane (CH₄), which makes up about 85% to 95% of its composition.
HSLC

26. What is the source of energy of the fossil fuels?

Answer:
The source of energy in fossil fuels is the solar energy stored by plants and animals millions of years ago through photosynthesis. This energy is released when fossil fuels are burned.
HSLC

27. What is nuclear fusion reaction?

Answer:
Nuclear fusion is a reaction in which two light atomic nuclei combine to form a heavier nucleus, releasing a huge amount of energy.
Example:

28. How much energy the Earth is getting from Sun?

Answer:
The Earth receives solar energy at a rate of about 1.7 × 10¹⁷ watts. On average, about 1.36 kW of solar energy per square meter reaches the upper atmosphere, known as the solar constant.
HSLC

29. What is Biogas?

Answer:
Biogas is a renewable fuel produced by the anaerobic decomposition of organic matter such as cow dung, agricultural waste, and kitchen refuse.
Main components:

Methane (CH₄) → ~60%
Carbon dioxide (CO₂) → ~35%
Traces of hydrogen sulphide and hydrogen.
Uses: Cooking, lighting, and running engines.
HSLC

30. What is the name of the machine that has been made by using wind energy?

Answer:
The machine made by using wind energy is called a windmill or wind turbine. It converts wind energy into mechanical energy or electricity.
HSLC

31. Mention the chief constituent of natural gas.

Answer:
The chief constituent of natural gas is methane (CH₄).
HSLC

32. Write two characteristics of a good fuel.

Answer:
Two characteristics of a good fuel are:

It should have a high calorific value.
It should burn completely without producing smoke or harmful gases.
HSLC

33. Name two commonly used solar devices.

Answer:
Two commonly used solar devices are:

Solar cooker
Solar water heater
HSLC

34. Name the main constituent of LPG.

Answer:
The main constituent of LPG is butane.
HSLC

35. What is gobar gas?

Answer:
Gobar gas is the biogas produced from cow dung (gobar) in a biogas plant. It mainly contains methane and is used as a domestic fuel.
HSLC

36. Name two alternate sources of energy.

Answer:
Two alternate sources of energy are:

Solar energy
Wind energy
HSLC

37. Name two sources of renewable energy.

Answer:
Two sources of renewable energy are:

Hydroelectric energy
Biogas energy
HSLC

38. Name two sources of non-renewable energy.

Answer:
Two sources of non-renewable energy are:

Coal
Petroleum
HSLC

39. Name the coal which are used mainly for the production of heat.

Answer:
Bituminous coal is mainly used for the production of heat because it has a high calorific value.
HSLC

40. What is called petrochemical substances? Give example.

Answer:
Petrochemical substances are chemical products derived from petroleum or natural gas.
Examples: Plastics, synthetic rubber, detergents, dyes, and fertilizers.
HSLC

41. What is LPG? What is the chief constituent of LPG?

Answer:
LPG stands for Liquefied Petroleum Gas. It is a mixture of hydrocarbon gases stored in a liquid state under pressure.

The chief constituent of LPG is butane and propane.

42. What is biodiesel?

Answer:
Biodiesel is a renewable, biodegradable fuel made from natural sources like vegetable oils, animal fats, or used cooking oil.

It is an eco-friendly alternative to petroleum-based diesel.
It produces less carbon emission and is sustainable.

43. Write the name of two devices which are used to convert solar energy into electric energy.

Answer:
Two devices used to convert solar energy into electricity are:

Solar photovoltaic cells
Solar panels (solar modules)

44. What is a wind farm?

Answer:
A wind farm is a group of wind turbines installed in one location to produce electricity using wind energy.

The turbines convert the kinetic energy of wind into electrical energy.

45. What is the significant advantage of tidal energy?

Answer:
The main advantage of tidal energy is that it is a renewable, predictable, and pollution-free source of power.

Tides occur regularly due to the gravitational pull of the moon and sun, ensuring consistent energy generation.

46. What are the great drawbacks of tide energy?

Answer:
The main drawbacks of tidal energy are:

Limited suitable locations for tidal power plants.
High installation and maintenance costs.
Can affect marine ecosystems and navigation.

47. Name two major sources of nuclear energy.

Answer:
The two major sources of nuclear energy are:

Uranium-235
Plutonium-239

48. What do you mean by nuclear fission?

Answer:
Nuclear fission is a process in which the nucleus of a heavy atom (like uranium or plutonium) splits into two or more lighter nuclei, releasing a large amount of energy.

This process is used in nuclear reactors to produce electricity.

49. Name the bacteria which can convert cow dung into gas.

Answer:
The bacteria that convert cow dung into biogas are:

Methanogenic bacteria (e.g., Methanobacterium and Methanococcus).

50. Name two gaseous fuels.

Answer:
Two examples of gaseous fuels are:

Natural gas
Hydrogen gas

51. How is increased demand for energy affecting our environment adversely?

Answer:
Increased demand for energy affects the environment in several ways:

Leads to deforestation and loss of biodiversity.
Causes air, water, and soil pollution due to fossil fuel burning.
Increases global warming and climate change.
Depletes natural resources at an unsustainable rate.

52. Name two appliances that use solar energy directly.

Answer:
Two appliances that use solar energy directly are:

Solar cooker
Solar water heater

53. Why are solar heating devices painted black from inside?

Answer:
Solar heating devices are painted black inside because:

Black color absorbs maximum heat.
It increases the efficiency of the device by minimizing reflection.

54. What is the value of the solar constant?

Answer:
The solar constant is the amount of solar energy received per unit area per second at the outer edge of Earth’s atmosphere.

Its value is approximately 1.36 kW/m².

55. What is coke?

Answer:
Coke is a porous, carbon-rich fuel obtained by heating coal in the absence of air (destructive distillation).

Uses:
1. As a reducing agent in the extraction of metals.
2. As a fuel in industries.

56. What is the main constituent of petroleum gas?

Answer:
The main constituent of petroleum gas is butane.

57. What is geothermal energy?

Answer:
Geothermal energy is the heat energy obtained from the Earth’s interior.

It is used to produce steam which drives turbines to generate electricity.

58. What is meant by OTEC?

Answer:
OTEC stands for Ocean Thermal Energy Conversion.

It is a process that uses the temperature difference between warm surface water and cold deep water in oceans to generate electricity.

59. What does SPV stand for?

Answer:
SPV stands for Solar Photovoltaic.

It refers to the technology that converts sunlight directly into electricity using solar cells.

60. In which process energy released is more — nuclear fission or nuclear fusion?

Answer:
Nuclear fusion releases more energy than nuclear fission.

In fusion, light nuclei (like hydrogen) combine to form heavier nuclei, releasing enormous energy (e.g., in the sun).

B. Short Type Questions
(Marks: 2/3)

1. Name the solid product obtained on heating bituminous coal in the absence of air. Mention two uses of it.
Answer:

The solid product obtained is coke.
Uses of coke:
1. Used as a reducing agent in the extraction of metals like iron.
2. Used as a fuel in industries and domestic purposes.

2. Name four alternate sources of energy.
Answer:
Four alternate sources of energy are:

Solar energy
Wind energy
Geothermal energy
Tidal energy

3. What are primary and secondary fuels?
Answer:

Primary fuels: Fuels that are found in nature and are used directly without processing.
Examples: Coal, natural gas, petroleum, wood.
Secondary fuels: Fuels obtained by processing primary fuels.
Examples: Petrol, diesel, coke, kerosene.

4. Define calorific value of a fuel. Write two characteristics of a good fuel.
Answer:

Calorific value: It is the amount of heat energy produced when one kilogram of fuel is completely burnt.
Two characteristics of a good fuel:
1. It should have a high calorific value.
2. It should produce less smoke and residue after burning.

5. Write the different classes of coal.
Answer:
The different classes of coal are:

Anthracite – Highest carbon content and highest calorific value.
Bituminous – Used widely for industrial purposes.
Sub-bituminous – Lower carbon content than bituminous.
Lignite – Lowest carbon content and calorific value.

6. What are primary and secondary fuels? Give examples.
Answer:
(Same as Q3 but with examples included explicitly)

Primary fuels: Found naturally and used directly.
Examples: Coal, petroleum, natural gas.
Secondary fuels: Processed from primary fuels.
Examples: Petrol, diesel, coke, kerosene.

7. What are the different components obtained after distillation of sub-bituminous coal?
Answer:
The components obtained are:

Coke
Coal tar
Ammoniacal liquor
Coal gas

8. Why is anthracite coal considered to be the best of all?
Answer:
Anthracite coal is considered the best because:

It has the highest carbon content (about 80–90%).
It has the highest calorific value and produces less smoke on burning.

9. How is coke prepared? What are its uses?
Answer:

Preparation: Coke is prepared by heating bituminous coal in the absence of air at about 1000°C in coke ovens.
Uses:
1. Used in the extraction of metals like iron in blast furnaces.
2. Used as a fuel in industries.

10. Write what do you know about the origin of petroleum.
Answer:
Petroleum was formed from the remains of plants and animals buried under the sea millions of years ago.

Due to high pressure, heat, and absence of air, these remains were converted into petroleum and natural gas over time.

11. Name the organisation of India that are involved in production of petroleum.
Answer:
The main organisations involved are:

Oil and Natural Gas Corporation (ONGC)
Oil India Limited (OIL)
Indian Oil Corporation (IOC)

12. Describe the distillation process in petroleum refining.
Answer:

Petroleum is heated in a fractional distillation column.
Different components are separated based on their boiling points:
1. Petroleum gas
2. Petrol
3. Kerosene
4. Diesel
5. Lubricating oil
6. Bitumen
Each fraction is collected at different levels in the column.

13. How is cracking done?
Answer:

Cracking is the process of breaking down heavy hydrocarbons into lighter hydrocarbons like petrol and LPG.
It is done by heating heavy fractions of petroleum in the presence of a catalyst or at high temperature.

14. Name the important product obtained from petroleum.
Answer:
The most important product obtained from petroleum is petrol (gasoline).

15. How is L.P.G produced and preserved?
Answer:

Production: LPG (Liquefied Petroleum Gas) is obtained during the refining of petroleum and natural gas processing.
Preservation: It is stored under high pressure in strong steel cylinders to keep it in a liquid state.

16. What are the precautions that should be taken while using L.P.G cylinders?
Answer:

Keep the cylinder in an upright position.
Always check for gas leaks before using.
Do not keep the cylinder near fire or heat sources.
Close the regulator and knob when not in use.

17. What are the alternative sources of energy?
Answer:
Alternative sources of energy include:

Solar energy
Wind energy
Geothermal energy
Tidal energy
Biomass energy
Hydroelectric energy

18. What is the source of solar energy? Mention its reactions.
Answer:

The main source of solar energy is the Sun.
It is produced by nuclear fusion reactions occurring in the Sun’s core:

19. What are photovoltaic cells and solar reflectors?
Answer:

Photovoltaic cells: Devices that convert solar energy directly into electrical energy using semiconductors like silicon.
Solar reflectors: Mirrors used to concentrate sunlight onto a small area to produce high temperatures, often used in solar cookers and power plants.

20. How is biogas formed from organic wastes?
Answer:

Biogas is formed by the anaerobic decomposition of organic wastes like animal dung, kitchen waste, and crop residue.
Microorganisms break down these wastes in the absence of oxygen, producing a mixture of gases mainly methane (CH₄), carbon dioxide (CO₂), and small amounts of hydrogen (H₂) and hydrogen sulfide (H₂S).

21. How is Gobar gas prepared?
Answer:

Gobar gas is a type of biogas prepared from cow dung (gobar).
Steps:
1. Cow dung is mixed with water to make a slurry.
2. This slurry is fed into a biogas digester.
3. Anaerobic bacteria decompose the slurry and release biogas, which contains about 60% methane.

22. What are the chief sources of energy?
Answer:
The chief sources of energy are:

Conventional sources – coal, petroleum, natural gas, hydroelectric power.
Non-conventional sources – solar, wind, tidal, geothermal, nuclear energy, and biomass.

23. How will you classify the sources of chief energy?
Answer:
Energy sources are classified into:

Renewable sources: Replenished naturally.
Examples: Solar energy, wind energy, hydro energy, biomass.
Non-renewable sources: Limited in nature and exhaustible.
Examples: Coal, petroleum, natural gas, nuclear fuel.

24. What are by-products formed during the manufacture of coke?
Answer:
The main by-products are:

Coal gas
Coal tar
Ammoniacal liquor
Benzene, toluene, and naphthalene

25. What are the main components of LPG? How is LPG conserved? Write two uses of it.
Answer:

Main components: Butane and propane.
Conservation: Stored under high pressure in strong steel cylinders.
Uses:
1. Used as a domestic cooking fuel.
2. Used as a fuel in vehicles and industries.

26. Write four major advantages of biodiesel.
Answer:

Environmentally friendly and reduces air pollution.
Renewable source of energy.
Produces less carbon monoxide and particulate matter.
Can be used in existing diesel engines without major modifications.

27. Write down four chemical substances which can be synthesized from natural gas.
Answer:

Methanol
Ammonia
Hydrogen
Urea

28. What are the advantages of solar energy, wind energy, and tidal energy?
Answer:

Solar energy:
1. Abundant and renewable
2. No pollution
Wind energy:
1. Cost-effective and eco-friendly
2. Useful in remote areas
Tidal energy:
1. Predictable and reliable
2. No greenhouse gas emissions

29. What are the different steps to generate electricity from wastes?
Answer:

Collection and segregation of wastes.
Anaerobic digestion to produce biogas.
Incineration of solid waste to generate heat.
Using the produced biogas or steam to drive turbines for generating electricity.

30. How energy can be obtained from municipal solid waste?
Answer:
Energy can be obtained by:

Incineration – burning solid waste to produce heat and steam.
Anaerobic digestion – decomposing organic waste to produce biogas.
Landfill gas recovery – methane produced in landfills is captured and used as fuel.

31. What are the drawbacks of the industry of nuclear energy?
Answer:

Radioactive waste disposal is difficult and hazardous.
Risk of nuclear accidents and radiation leakage.
High cost of building and maintaining nuclear power plants.
Limited availability of uranium and thorium resources.

32. What is the composition of solar energy?
Answer:
Solar energy consists of:

Visible light (~46%)
Infrared radiation (~49%)
Ultraviolet radiation (~5%)

33. What are the advantages of coke over coal?
Answer:

Coke produces more heat than coal as it has a higher carbon content.
Burns without smoke, making it more environmentally friendly.
Used as a reducing agent in metallurgy, unlike coal.

34. What is gasohol? Where is it used?
Answer:

Gasohol: A fuel mixture of 90% petrol and 10% ethanol.
Uses: Used as an automobile fuel to reduce pollution and petroleum consumption.

C. Essay Type Questions
(Marks: 4)

1. What specific qualities should a substance contain to become a fuel? Describe them.

Answer:
A good fuel should have the following qualities:

High calorific value
- It should produce a large amount of heat energy per unit mass.
- Example: LPG has a higher calorific value than coal.
Easy availability and low cost
- The fuel should be readily available and economical for practical use.
Easy ignition and controlled combustion
- A good fuel should catch fire easily and burn at a steady rate without explosions.
Less smoke and non-toxic gases
- It should produce minimal pollutants and should be environmentally friendly.
Ease of storage and transportation
- It should be safe to handle and store without the risk of fire or leakage.
Non-corrosive nature
- It should not corrode storage containers or engine components.

Conclusion:
A fuel having these qualities ensures efficiency, safety, and minimal environmental impact.

2. What are the different types of coal? Describe the properties and uses of each of them.

Answer:
Coal is classified into four main types based on carbon content and calorific value:

(a) Anthracite

Properties:
- Hard, black, and lustrous.
- Highest carbon content (~80–90%) and calorific value.
- Burns with a smokeless flame.
Uses:
- Domestic heating.
- Metallurgical processes.

(b) Bituminous

Properties:
- Dense, black coal with 60–80% carbon.
- Produces more smoke than anthracite.
Uses:
- Used in power generation.
- Raw material for making coke and coal tar.

(c) Sub-Bituminous

Properties:
- Lower carbon content (~40–60%) and lower calorific value.
- Brownish-black in color.
Uses:
- Used for steam generation and in cement industries.

(d) Lignite

Properties:
- Lowest grade of coal with ~25–35% carbon.
- High moisture content, low calorific value.
Uses:
- Used in thermal power stations and brick kilns.

3. How is natural gas separated from crude oil? What are the components obtained by cracking of crude oil?

Answer:

(a) Separation of natural gas from crude oil:

Natural gas is often found along with petroleum in underground reservoirs.
During petroleum extraction, gas rises to the surface due to high pressure.
It is separated from crude oil using a gas separator and then purified.

(b) Components obtained by cracking of crude oil:

Cracking is the process of breaking down heavy hydrocarbons into lighter hydrocarbons by applying heat or using catalysts. The main products are:

Liquefied Petroleum Gas (LPG) – used for cooking.
Petrol (Gasoline) – used as automobile fuel.
Diesel – used in trucks, buses, and generators.
Kerosene – used for lamps, stoves, and jet fuels.
Lubricating oils – used in engines and machinery.
Bitumen – used for road surfacing.

4. Describe the method of petroleum refining.

Answer:
Petroleum refining is the process of separating crude petroleum into useful products by fractional distillation.

Steps involved:

Heating of crude oil
- Crude oil is heated in a furnace to about 400°C to convert it into vapors.
Fractional distillation
- The vapors are passed into a fractionating column, which is cooler at the top and hotter at the bottom.
- Components condense at different heights based on their boiling points:
  - Top: Petroleum gas
  - Upper section: Petrol (gasoline)
  - Middle section: Kerosene and diesel
  - Lower section: Lubricating oils and paraffin wax
  - Bottom: Bitumen and asphalt
Collection of fractions
- Each component is collected separately and stored for various uses.

Products obtained:

Petroleum gas → cooking fuel
Petrol → automobile fuel
Diesel → transport and generators
Kerosene → stoves and lamps
Lubricants and wax → machinery and candles
Bitumen → road construction

Conclusion:
Petroleum refining converts crude oil into valuable fuels and chemicals essential for daily life and industries.

5. What are the main components of natural gas? Mention the petrochemicals obtained from natural gas. Describe their uses.

Answer:
Main components of natural gas:

Methane (CH₄) → 80–95%
Ethane (C₂H₆)
Propane (C₃H₈)
Butane (C₄H₁₀)
Small amounts of carbon dioxide, nitrogen, and hydrogen sulfide.

Petrochemicals obtained from natural gas:

Methanol → used for making formaldehyde, acetic acid, and plastics.
Ammonia → used for fertilizers and nitric acid production.
Ethylene and Propylene → used for manufacturing plastics and synthetic fibers.
Hydrogen → used in refineries and ammonia production.

Uses:

Domestic cooking fuel.
Fuel for vehicles (CNG).
Used in the production of fertilizers, plastics, and chemicals.

6. Describe different methods used to utilize solar energy.

Answer:
Solar energy can be harnessed in the following ways:

Solar Cookers
- Use mirrors or reflective surfaces to focus sunlight for cooking food.
Solar Water Heaters
- Use solar panels to heat water for domestic and industrial purposes.
Solar Cells (Photovoltaic Cells)
- Convert sunlight directly into electricity. Used in calculators, satellites, and solar panels.
Solar Thermal Power Plants
- Use sunlight to produce steam, which drives turbines to generate electricity.
Solar Dryers
- Used for drying grains, fruits, and vegetables using solar heat.

7. Describe a gobar gas plant. What are the different uses of gobar gas?

Answer:
Gobar gas plant:

A biogas plant that uses cow dung (“gobar”) and other organic waste to produce biogas through anaerobic fermentation.
The gas mainly contains methane (~55–65%), carbon dioxide, and traces of hydrogen sulfide.

Uses of gobar gas:

Cooking fuel → smokeless and economical.
Electricity generation → used in rural electrification.
Lighting → used in lamps in rural areas.
By-product (slurry) → used as high-quality manure for agriculture.

8. What are the different components found during refining of petroleum? Write the uses of two such components.

Answer:
Main components obtained from petroleum refining:

Petroleum gas → used as fuel in LPG cylinders.
Petrol (gasoline) → used as automobile fuel.
Diesel → used in trucks, buses, and generators.
Kerosene → used for cooking, lighting, and aviation fuel.
Lubricating oils → used in engines and machines.
Bitumen → used in road surfacing.

Uses of two components:

Petrol: Fuel for cars and motorcycles.
Diesel: Powering heavy vehicles and generators.

9. What is hydel power? Draw schematic diagram of hydroelectric power plant.

Answer:
Hydel power:

Electricity generated from the kinetic energy of flowing water is called hydel power.
Dams store water in reservoirs, and when released, water flows through turbines connected to generators, producing electricity.

Schematic diagram:

10. Give the principle, construction, and operation of a box-type solar cooker.

Answer:

Principle:

Works on the principle of greenhouse effect: sunlight enters through a glass cover, gets trapped inside, and cooks food.

Construction:

Outer box: Made of wood or metal.
Inner box: Painted black to absorb heat.
Glass cover: Allows sunlight in and traps heat.
Reflector panel: Directs extra sunlight into the box.

Operation:

Food is placed in black vessels inside the cooker.
Glass cover is closed, trapping solar radiation.
Heat builds up, raising the temperature to 100–150°C.
Food cooks slowly and evenly.

Case Study-Based Questions

(1) Energy Sources

Q1. What is the important characteristic of energy?
Answer:
Energy can neither be created nor destroyed; it can only be converted from one form to another.

Q2. How do you define energy sources?
Answer:
Energy sources are natural reserves where energy is stored in sufficient amounts and from which we can obtain usable energy.

Q3. In how many broad categories are energy sources divided and what are they?
Answer:
Energy sources are divided into two main categories:

Renewable energy sources → e.g. solar, wind, hydropower.
Non-renewable energy sources → e.g. coal, petroleum, natural gas.

(2) Solar Energy

Q1. How does the sun produce energy?
Answer:
The sun produces energy through nuclear fusion reactions, where hydrogen atoms fuse to form helium, releasing enormous energy in the form of light and heat.

Q2. What is an excellent example of renewable energy sources?
Answer:
Solar energy is an excellent example of a renewable energy source.

Q3. Give some other examples of renewable energy sources.
Answer:

Wind energy
Hydropower (river water energy)
Ocean wave energy
Geothermal energy
Bioenergy

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