Glossary: Sources of Energy
Energy – The capacity of a body or system to do work.
Fuel – A substance that produces heat and energy when burned.
Calorific Value – The amount of heat produced when a unit mass of fuel is completely burned.
Natural Source of Energy – Energy sources available from nature, such as sunlight, wind, and flowing water.
Synthetic Source of Energy – Man-made energy sources like chemical energy stored in batteries.
Renewable Source of Energy – A natural energy source that replenishes itself over time, e.g., solar, wind, and hydro power.
Non-renewable Source of Energy – An energy source that cannot be replenished in a short period, e.g., coal, petroleum, and natural gas.
Fossil Fuels – Fuels formed from the remains of ancient plants and animals over millions of years (e.g., coal, petroleum, natural gas).
Carbonisation – The process of conversion of dead plant matter into coal under heat and pressure.
Peat – The earliest form of coal with low carbon content (~30%).
Lignite – A soft, brown coal with low carbon content (~38%).
Bituminous Coal – A type of coal with moderate carbon content (~65%), used in electricity generation and making coke.
Anthracite – The highest grade of coal with over 90% carbon content.
Destructive Distillation – Strong heating of coal in the absence of air to obtain useful products like coke, coal tar, and coal gas.
Coke – A hard, porous by-product of coal, used as fuel and in metal extraction.
Coal Tar – A black, viscous liquid obtained from coal, used in making chemicals, perfumes, dyes, and drugs.
Coal Gas – A combustible gas obtained from coal used as industrial and domestic fuel.
Petroleum (Crude Oil) – A dark, viscous liquid found in rock layers, used to produce fuels and chemicals.
Refining – The process of separating crude petroleum into its useful components.
Asphalt – A black, sticky substance obtained from petroleum used for road surfacing.
Paraffin Wax – A waxy by-product of petroleum used in candles and ointments.
Lubricating Oil – A viscous oil derived from petroleum used to reduce friction in machines.
Diesel – A fuel derived from petroleum used in heavy vehicles and generators.
Kerosene – A fuel derived from petroleum used in lamps and stoves.
Gasoline (Petrol) – A refined fuel used in automobiles and for dry cleaning.
Aviation Fuel – A highly refined form of petrol used in aircraft.
Liquefied Petroleum Gas (LPG) – A clean-burning fuel made from petroleum, used in cooking.
Compressed Natural Gas (CNG) – Natural gas stored under high pressure and used as a clean fuel for vehicles.
Natural Gas – A gaseous fossil fuel found along with petroleum, used in homes, industries, and for power.
Cleaner Fuels – Fuels that cause less pollution (e.g., LPG, CNG, biomass).
Biomass – Organic matter used as fuel (e.g., wood, crop waste, animal dung).
Hydropower – Energy derived from flowing water.
Solar Energy – Energy harnessed from sunlight.
Wind Energy – Energy obtained from wind using turbines.
Geothermal Energy – Heat energy obtained from within the earth.
Tidal Energy – Energy derived from the rise and fall of ocean tides.
Global Warming – The gradual increase in the Earth’s temperature due to greenhouse gas emissions.
Pollution – The introduction of harmful substances into the environment.
Urbanisation – The process of increasing population in cities and towns.
Deforestation – The removal of forests for human use, often leading to environmental issues.
Something To Know
A. Fill in the blanks.
- ____________ and are non-renewable sources of energy.
Answer – Coal and petroleum
- ____________ is a major renewable, natural resource.
Answer – Wood
- The process, in which coal is strongly heated in the absence of air, is known as ____________.
Answer – destructive distillation.
- In oil wells ____________ is always found above the layer of petroleum.
Answer – natural gas
- ____________ is a black viscous liquid, obtained by destructive distillation of coal.
Answer – Coal tar
B. State True or False for the following statements.
- Fossil fuels are renewable natural resources.
Answer – False
- Anthracite has higher carbon content than lignite.
Answer – True
- Coke can be used to make fuel gases.
Answer – True
- Natural gas is found below the petroleum layers.
Answer – False
- Burning of fossil fuels is a major source of pollution.
Answer – True
C. Tick (✓) the correct option.
1.The highest grade of coal is known as—
lignite
anthracite
bituminous
peat
Answer – anthracite
- Coke and coal tar are obtained from—
petroleum
natural gas
coal
diesel
Answer – coal
- Different types of coal generally have the—
same content of volatile material and same percentage of carbon.
same content of volatile material but different percentage of carbon, different content of volatile material but same percentage of carbon.
different content of volatile material as well as different percentage of carbon.
Answer – different content of volatile material as well as different percentage of carbon.
- A product, that is not obtained through the refining of petroleum, is—
diesel
kerosene
coal gas
petrol
Answer – coal gas
- Which of the following is a renewable source of energy?
tidal energy
coal
diesel
petrol
Answer – tidal energy
D. Answer the following questions in brief:
- Define the term’fuel’.
Answer – A fuel is a substance that produces heat and energy on burning in air.
- Name any two renewable natural sources of energy.
Answer – Solar energy and wind energy.
- Define the term ‘carbonisation’.
Answer – Carbonisation is the slow process of conversion of dead plant material into coal under high pressure and temperature over millions of years.
- Name the three main products obtained from destructive distillation of coal.
Answer – Coke, coal tar, and coal gas.
- State two uses each of the following:
(a) asphalt (b) paraffin wax
Answer – (a) asphalt
(i) Used for road surfacing,
(ii) Used for coating electric poles to prevent rusting.
(b) Paraffin wax
Answer – (i) Used in making candles, (ii) Used in ointments and cosmetics.
- Write the full forms of CNG, LPG and PNG.
Answer – CNG: Compressed Natural Gas
LPG: Liquefied Petroleum Gas
PNG: Piped Natural Gas
E. Answer the following questions.
- Describe, in brief, the process of ‘coal formation’.
Answer – Coal was formed millions of years ago from the remains of dense forests and plants buried under the earth. These remains were subjected to high pressure and temperature over time, leading to their transformation into coal. This slow process is known as carbonisation.
- Differentiate between lignite and bituminous coal.
Answer –
Feature | Lignite | Bituminous Coal |
Carbon Content | Around 38% | Around 65% |
Quality | Low-grade | Higher-grade |
Use | Mainly for electricity generation | Used for power generation and coke production |
- How do petroleum and natural gas occur in nature?
Answer – Petroleum and natural gas are found deep underground, trapped between layers of impermeable rocks. Petroleum lies above salt water, while natural gas, being lighter, is found above petroleum.
- State the main advantages of using natural gas.
Answer – It burns easily and has a high calorific value.
It is a cleaner fuel, causing less air pollution compared to coal and petroleum.
It leaves no ash after burning.
It is used as an efficient automobile and industrial fuel and also in manufacturing fertilizers.
- Keeping in mind their availability in nature, explain the need of
using coal and petroleum judiciously.
Answer – Coal and petroleum are non-renewable resources. They take millions of years to form, but we are using them rapidly. If not used wisely, they will get exhausted. Moreover, their excessive use causes pollution. Therefore, they must be used judiciously and alternative renewable energy sources should be explored.
Value Based Question
The chemistry teacher, explained to her students that when petroleum, a naturally occuring fossil fuel, is separated into its different components, each of these compo nents is useful in one way or the other. She then told her students that our daily life too can be thought of as ‘made up’ of a number of activities, actions and tasks. She suggested that ‘all of us’ should try to ensure and aim that all these ‘components’ of our daily life, are useful/helpful to the society at large.
- State the values that you think are contained in the teacher’s talk and suggestions.
Answer – Responsibility towards society
Productivity and usefulness
Environmental awareness
Self-awareness and introspection
Sustainability and mindful living
- Name any three components, obtained from petroleum, and state any one use of each of them.
Answer – Petrol – Used as fuel in vehicles.
Kerosene – Used as a domestic fuel for cooking and lighting.
Paraffin wax – Used in making candles and ointments.
- Have a ‘group discussion’ in which different students suggest ‘ways and means’ of making their different daily life actions and activities, useful to the society at large.
Answer – One student suggested saving electricity and water at home to conserve natural resources.
Another student shared that helping younger siblings with studies supports family and promotes education.
Someone mentioned segregating waste and practicing recycling to reduce pollution.
A student said they volunteer at local clean-up drives on weekends.
One suggested using public transport or cycling to reduce air pollution.
Another added the importance of respecting elders and teachers to create a positive environment.
Something To Do
- Make a report on ‘electricity consumption’ in your house. Suggest some ways that can help to reduce the consumption.
Answer – Report on Electricity Consumption in My House
In my house, electricity is used for lighting, fans, air conditioners, water heaters, refrigerators, washing machines, and electronic devices like computers and televisions. The monthly electricity bill ranges between 600 to 800 units, which is quite high during the summer months.
Ways to Reduce Electricity Consumption:
Use LED bulbs instead of incandescent bulbs.
Switch off lights and fans when not in use.
Use energy-efficient appliances with high star ratings.
Reduce the use of air conditioners by ventilating rooms naturally.
Use solar water heaters instead of electric ones.
Run washing machines with full loads to save electricity.
Encourage daylight usage during the daytime.
- Unlike thermal power plants, which burn fossil fuels and emit large amounts of carbon dioxide (a greenhouse gas) into the atmosphere, nuclear power plants use uranium (a metal) to produce huge amounts of energy from very small amount of fuel. However, they release harmful radiations that can pose a high risk to the population.
Do you think nuclear energy can be an answer to the problems caused by the use of fossil fuels? Try to prepare a report, listing points that suggest that nuclear power could be/could not be a better way of generating electricity as compared to fossil fuels.
Answer – Report: Is Nuclear Energy a Better Alternative to Fossil Fuels?
Advantages of Nuclear Energy:
Produces large amounts of energy from a small quantity of fuel.
No emission of carbon dioxide or other greenhouse gases.
Reduces dependence on fossil fuels like coal and petroleum.
Helps in slowing down global warming.
Disadvantages of Nuclear Energy:
High risk of radiation leaks, which can be harmful to humans and the environment.
Expensive and complex setup of nuclear power plants.
Disposal of radioactive waste is a big challenge.
Accidents (like Chernobyl or Fukushima) have long-lasting impacts.
Conclusion:
While nuclear energy can reduce pollution and dependence on fossil fuels, the risks associated with radiation and waste management make it a challenging alternative. Hence, nuclear energy may be a part of the solution, but not a complete replacement.
- Try to find out information about the places/activities for which solar energy or wind energy is being put to use in place of conventional fossil fuel based energy sources.
Answer – Report on Places/Activities Using Solar and Wind Energy
Solar Energy:
Rajasthan and Gujarat have major solar parks like the Bhadla Solar Park (Rajasthan), which is one of the largest in the world.
In Delhi, solar panels are installed on rooftops of schools and government buildings.
Railway stations like Guwahati and Varanasi use solar energy for electricity.
Street lighting and solar cookers are used in rural areas.
Wind Energy:
Tamil Nadu has the Muppandal Wind Farm, one of the largest wind farms in Asia.
Gujarat and Maharashtra have also set up large wind energy plants.
Windmills are used in coastal and hilly regions to generate electricity.
Conclusion:
Solar and wind energy are increasingly being used as clean and renewable alternatives to fossil fuels in many parts of India, helping reduce environmental pollution and energy costs.
Additional Questions and Answers – 01
Short Answer Questions (1-2 marks)
- What are fossil fuels? Give two examples.
Answer: Fossil fuels are non-renewable energy sources formed from dead plants and animals over millions of years. Examples: Coal, Petroleum.
- Why is CNG considered a cleaner fuel than petrol?
Answer: CNG burns more completely, releasing fewer pollutants (CO₂, smoke) and leaving no ash.
- What is the main component of coal?
Answer: Carbon (varies from 30% in peat to 90% in anthracite).
- Name the process used to obtain petroleum products like petrol and diesel.
Answer: Refining (Fractional distillation).
- Why is petroleum called ‘liquid gold’?
Answer: Due to its high economic value and wide use in transport, industries, and daily life.
- What is the primary use of coal tar?
Answer: Manufacturing synthetic dyes, drugs, paints, and explosives.
- Why is LPG stored in cylinders under pressure?
Answer: To liquefy the gas, allowing more fuel to be stored in less space.
- Which gas is found above petroleum in oil wells?
Answer: Natural Gas (mainly methane).
Long Answer Questions (3-5 marks)
- Compare renewable and non-renewable energy sources with examples.
Answer:
Feature | Renewable | Non-Renewable |
Availability | Replenished naturally (e.g., solar, wind) | Limited (e.g., coal, petroleum) |
Pollution | Low/zero emissions | High CO₂ and smoke |
Cost | Low long-term cost | Expensive extraction |
Examples | Solar panels, hydropower | Diesel, coal |
- Describe the formation of coal. Name its four types.
Answer: Formation: Dead plants buried under earth compressed over millions of years by heat and pressure (carbonisation).
Types:
Peat (30% carbon, soft).
Lignite (38% carbon, low-grade).
Bituminous (65% carbon, used for electricity).
Anthracite (90% carbon, hardest).
- Explain the refining of petroleum. List any three products obtained.
Answer: Process: Petroleum is heated in a fractionating column, separating components based on boiling points.
Products:
Petrol (Fuel for cars).
Diesel (Heavy vehicles).
LPG (Cooking gas).
- Why should we shift to cleaner fuels? Suggest two alternatives to fossil fuels.
Answer: Reasons: Fossil fuels cause air pollution, global warming, and are exhaustible.
Alternatives:
Solar energy (Sunlight → Electricity).
Wind energy (Turbines → Power).
- How does destructive distillation of coal benefit industries?
Answer: It produces:
Coke (Smokeless fuel for metallurgy).
Coal tar (Dyes, drugs).
Coal gas (Fuel for industries).
Diagram-Based Questions
- Label the layers in an oil well.
Answer: Rock cap
Natural gas
Petroleum
Saltwater
- Sketch a fractionating column and mark where petrol is collected.
Answer: Petrol condenses in the upper, cooler section of the column.
HOTS (Higher-Order Thinking Skills) Questions
- If coal reserves deplete, how would it impact electricity generation in India?
Answer: 70% of India’s electricity comes from coal → Power shortages.
Solution: Shift to renewable energy (solar/wind).
- Why is CO₂ emission higher from coal than wood, even though both are fuels?
Answer: Coal has higher carbon content (90% vs. 50% in wood) → More CO₂ per kg burned.
- How can solar energy reduce dependence on fossil fuels in villages?
Answer: Solar panels provide electricity without grid connection.
Solar cookers replace firewood/kerosene.
Value-Based Questions
- Ramesh uses a bicycle instead of a bike for short distances. What value does he show?
Answer: Environmental responsibility (reduces fossil fuel use and pollution).
- A factory near a river dumps coal waste into water. Why is this harmful?
Answer: Pollutes water → Kills aquatic life and harms human health.
Practical Activity
- Demonstrate how sunlight can replace LPG for cooking.
Materials: Solar cooker, food sample.
Steps:
Place food in the cooker.
Adjust reflector to focus sunlight.
Observation: Food cooks without LPG.
Summary Table: Fossil Fuels & Alternatives
Fuel Advantage Disadvantage
Coal Cheap, abundant High pollution
Petroleum Versatile (vehicles, etc.) Non-renewable, costly
Solar Clean, unlimited Needs sunlight
Additional Questions – 02
Short Questions and Answers
- Question – What is a fossil fuel?
Answer – A fossil fuel is a natural fuel formed from the remains of dead plants and animals over millions of years, such as coal, petroleum, and natural gas.
- Question – What is meant by calorific value?
Answer – Calorific value is the amount of heat energy produced on complete combustion of 1 kg of a fuel.
- Question – Why is CNG considered an eco-friendly fuel?
Answer – CNG produces less smoke and harmful gases, making it a cleaner alternative to other fossil fuels.
- Question – Which fossil fuel has the highest carbon content?
Answer – Anthracite coal has the highest carbon content.
- Question – What is destructive distillation of coal?
Answer – It is the process of heating coal in the absence of air to produce coke, coal tar, and coal gas.
- Question – Name one solid, one liquid, and one gaseous fuel.
Answer – Solid – Coal, Liquid – Petrol, Gas – LPG.
- Question – Name two by-products of petroleum refining.
Answer – Diesel and kerosene.
- Question – What does LPG stand for?
Answer – Liquified Petroleum Gas.
- Question – Why is wood not considered an ideal fuel?
Answer – Because it produces smoke and causes deforestation.
- Question – What is the main use of bituminous coal?
Answer – It is mainly used in power generation and for producing coke.
________________________________________
Long Questions and Answers
- Question – Why is there a need to switch from non-renewable to renewable sources of energy?
Answer – Non-renewable sources like coal and petroleum are limited and cause environmental pollution. Their burning leads to greenhouse gas emissions and global warming. On the other hand, renewable sources like solar, wind, and hydropower are eco-friendly, inexhaustible, and reduce dependency on fossil fuels.
- Question – Describe the refining of petroleum and list its major products along with uses.
Answer – Refining of petroleum is the process of separating crude oil into different useful products through fractional distillation. Major products include:
Petrol – Used as fuel in vehicles.
Diesel – Used in heavy vehicles and generators.
Kerosene – Used for cooking and lighting.
Lubricating oil – Used to reduce friction in machines.
Asphalt – Used for road construction.
Paraffin wax – Used in candles and ointments.
- Question – What is biomass energy? What are its advantages?
Answer – Biomass energy is the energy derived from organic materials like plant waste, dung, and crop residue.
Advantages:
It is renewable and widely available.
Reduces dependency on fossil fuels.
Utilizes agricultural waste efficiently.
Emits less carbon dioxide when used properly.
- Question – Write a comparison between coal and petroleum as sources of energy.
Answer –
Property | Coal | Petroleum |
Form | Solid | Liquid |
Pollution | High smoke and ash | Less ash, more harmful gases |
Use | Electricity generation, industrial fuel | Transport fuel, power generation |
By-products | Coke, coal tar | Petrol, diesel, kerosene, LPG |
Availability | Found in mines | Found in underground oil reservoirs |
- Question – How does the use of cleaner fuels help in sustainable development?
Answer – Cleaner fuels like LPG, CNG, and renewable energy sources produce less pollution and reduce carbon emissions. They conserve natural resources, ensure better public health, and reduce the impact of climate change, thereby contributing to sustainable development.