🧪 Chemistry · Topic 7 of 10
Start with the study notes on Coal, Petroleum & Natural Resources (definitions, examples and a quick revision), then work through 60 practice questions, each with the correct answer and a clear explanation of why it is right. When you are ready, take this topic as an interactive quiz to test yourself.
Topic overview
Natural resources are things found in nature that people use.
Fossil fuels are fuels formed from the remains of dead plants and animals buried under the earth for millions of years.
Coal (solid) · Petroleum (liquid) · Natural gas (gas)
Remember: Fossil fuels take millions of years to form, so once used up they cannot be replaced in our lifetime.
Coal formed from huge forests that were buried about 300 million years ago. Heat and pressure, without air, slowly turned the plants into coal. This process is called carbonisation.
Coal is mostly carbon. Its grades, from lowest to highest carbon content, are:
Peat → Lignite → Bituminous coal → Anthracite (best)
Example: Most of India's electricity comes from thermal power plants, which burn coal to turn water into steam that spins turbines.
Heating coal without air (destructive distillation) gives three useful products:
Petroleum formed from tiny sea plants and animals that died, sank to the sea bed and were covered with sand and clay. Over millions of years, heat and pressure turned them into oil and natural gas.
Oil and gas collect in rock, trapped under a layer that does not let them through. Gas sits on top, then oil, then water.
Examples:
Crude oil is a mixture, so it must be refined before use. It is separated in a refinery by fractional distillation, because each part (fraction) has a different boiling point.
Lightest (top) → Petroleum gas · Petrol · Kerosene · Diesel · Lubricating oil · Paraffin wax · Bitumen ← Heaviest (bottom)
Petrochemicals from petroleum and natural gas are used to make plastics, polythene, nylon, polyester and detergents.
Natural gas is found with petroleum. It is mainly methane. Stored under high pressure, it is called CNG (Compressed Natural Gas).
Example: Delhi's buses and autorickshaws switched to CNG to cut air pollution.
Fossil fuels are limited, and burning them causes pollution: carbon dioxide (global warming), sulphur dioxide (acid rain) and soot.
The Petroleum Conservation Research Association (PCRA) advises:
Renewable energy sources do not run out, e.g. solar, wind, water (hydro) and biogas.
Example: Biogas is made when bacteria break down cow dung and plant waste without air. It is mostly methane, and the leftover slurry is good manure.
| Misconception | Correct understanding |
|---|---|
| Coke is a petroleum product. | Coke comes from coal; petroleum gives petrol, kerosene and diesel. |
| Fossil fuels will form again soon. | They take millions of years, so for us they are effectively non-renewable. |
| Crude oil can be used straight from the well. | It is a mixture that must be refined first. |
| Air and sunlight can run out. | They are inexhaustible, though air can be polluted. |
| Coal and petroleum formed the same way. | Coal came from land forests; petroleum came from tiny sea organisms. |
Give one inexhaustible and one exhaustible resource.
Sunlight (inexhaustible) and coal (exhaustible).
What is the process of coal formation called?
Carbonisation.
Name three products made from coal.
Coke, coal tar and coal gas.
Which product of coal tar repels moths?
Naphthalene.
How is petroleum separated into petrol, kerosene and diesel?
By refining (fractional distillation), using their different boiling points.
Which petroleum product is used for road surfaces?
Bitumen.
Why is CNG called a clean fuel?
It burns almost completely, with very little smoke.
Where was India's first oil well drilled?
Digboi, in Assam.
Key takeaway: Coal and petroleum took millions of years to form and are running out, so we must use them carefully and switch to renewable energy.
Notes written by Velnov for Class 6–8 students, following the topics of the NCERT science syllabus.
Q1. easy
Resources that are found in nature and can be used by humans are called:
Answer: A — Natural resources
Air, water, soil, minerals, forests and fossil fuels are all natural resources. Some are unlimited (inexhaustible) and some are limited (exhaustible).
Q2. medium
Resources present in unlimited quantity in nature are called:
Answer: A — Inexhaustible natural resources
Sunlight, air and water are inexhaustible - they are not likely to be used up by human activities, though they can be polluted.
Q3. medium
Resources present in LIMITED quantity that may be exhausted by human use are called:
Answer: A — Exhaustible natural resources
Forests, wildlife, minerals, coal and petroleum are exhaustible. They take a very long time to form, so careless use can finish them.
Q5. medium
The slow process by which dead vegetation buried under the earth turned into coal is called:
Answer: A — Carbonisation
Carbonisation is the gradual conversion of dead plant matter into coal under high pressure and temperature over millions of years, increasing the carbon content.
Q7. medium
Coal is mainly composed of:
Answer: A — Carbon
Coal is mostly carbon, with smaller amounts of hydrogen, oxygen, nitrogen and sulphur. The higher the carbon content, the better the quality of the coal.
Q9. medium
Which of these is a product obtained by processing coal?
Answer: A — Coke
Coke, coal tar and coal gas come from coal. Petrol, diesel and kerosene are obtained from petroleum instead.
Q11. medium
Coke is mainly used:
Answer: A — In the extraction of metals and in the manufacture of steel
In a blast furnace, coke reduces iron oxide to iron and also supplies the heat needed. It is a key raw material for the steel industry.
Q13. medium
Naphthalene balls, used to repel moths, are obtained from:
Answer: A — Coal tar
Naphthalene is one of the many chemicals extracted from coal tar. Moth balls made from it sublime slowly, releasing vapour that keeps insects away.
Q15. medium
Coal gas is:
Answer: A — A fuel gas obtained during the processing of coal to make coke
Coal gas is released when coal is heated without air. It was used for street lighting in London and Delhi in the 19th century, and is now used as an industrial fuel.
Q17. medium
Petroleum was formed from:
Answer: A — Dead sea organisms buried under sand and clay millions of years ago
Tiny sea plants and animals sank to the ocean bed and were covered with sand and clay. Over millions of years, heat and pressure and the absence of air turned them into petroleum and natural gas.
Q19. medium
Petroleum and natural gas deposits are usually found:
Answer: A — Trapped between layers of impervious rock, with gas above the oil
Oil and gas float above the water in porous rock, sealed by non-porous rock layers above. Natural gas, being lightest, sits at the top, then oil, then water.
Q21. medium
Refining separates the components of petroleum based on their different:
Answer: A — Boiling points
In a tall fractionating column, crude oil is heated. Each fraction condenses at the height where the temperature matches its boiling point, and is drawn off separately.
Q23. medium
Which petroleum fraction is used as fuel for LIGHT motor vehicles and aeroplanes?
Answer: A — Petrol
Petrol is a light, highly volatile fraction used in cars, motorcycles and aviation fuel. It is also used as a solvent for dry cleaning.
Q24. medium
Which petroleum fraction is used as jet aircraft fuel and in stoves and lamps?
Answer: A — Kerosene
Kerosene fuels jet aircraft and is widely used in India for stoves and lamps. It sits between petrol and diesel in the fractionating column.
Q26. medium
Paraffin wax obtained from petroleum is used to make:
Answer: A — Ointments, candles and vaseline
Paraffin wax is a soft, white solid fraction used in candles, ointments, vaseline and waxed paper.
Q28. medium
Lubricating oil from petroleum is used to:
Answer: A — Reduce friction between moving parts of machines
Lubricants form a thin film between rubbing surfaces, reducing friction and wear and helping machines run smoothly and last longer.
Q30. medium
Which of these is made from petrochemicals?
Answer: A — Polythene bags
Polythene, nylon, polyester, detergents and most plastics are all petrochemical products. Cotton, wood and clay are natural materials.
Q32. medium
CNG stands for:
Answer: A — Compressed Natural Gas
Natural gas stored under high pressure is called CNG. It is used as a clean fuel for vehicles and for power generation.
Q34. medium
In India, natural gas reserves are found in:
Answer: A — Tripura, Rajasthan, Maharashtra and Krishna-Godavari delta
India's important natural gas fields lie in Tripura, Rajasthan, Maharashtra and the Krishna-Godavari delta in Andhra Pradesh.
Q36. medium
In which Indian states are the major COAL deposits found?
Answer: A — Jharkhand, Odisha, West Bengal, Chhattisgarh and Madhya Pradesh
India's coalfields are concentrated in the eastern and central states - Jharkhand (Jharia, Bokaro), Odisha, West Bengal (Raniganj), Chhattisgarh and Madhya Pradesh.
Q38. medium
Why must we conserve fossil fuels?
Answer: A — They are exhaustible, take millions of years to form and cause pollution when burnt
Once used, fossil fuels cannot be replaced in any human timescale. Burning them also releases carbon dioxide and other pollutants, so conserving them helps on both counts.
Q40. medium
Which PCRA tip helps save fuel while driving?
Answer: A — Drive at a constant, moderate speed and switch off the engine at red lights
Steady driving avoids the extra fuel used in repeated acceleration, and switching off at long signals prevents idling waste. Correct tyre pressure and regular servicing also improve mileage.
Q42. medium
Biogas is produced from:
Answer: A — Decomposition of animal dung and plant waste by bacteria without air
In a biogas plant, bacteria break down cow dung and organic waste anaerobically, producing mainly methane. The leftover slurry is a good manure.
Q44. medium
Which of these damages caused by burning coal is MOST serious for the atmosphere?
Answer: A — Release of carbon dioxide and sulphur dioxide, causing global warming and acid rain
Coal combustion releases carbon dioxide, which drives global warming, and sulphur dioxide, which produces acid rain. Fly ash and soot also pollute the air.
Q46. medium
Which of these is an INEXHAUSTIBLE natural resource?
Answer: A — Sunlight
Sunlight, air and water are available in essentially unlimited amounts. Coal, petroleum and mineral ores exist in fixed quantities and can be exhausted.
Q48. medium
Which fraction comes off at the TOP of a petroleum fractionating column?
Answer: A — Petroleum gas (the lightest fraction with the lowest boiling point)
The column is hottest at the bottom. Light fractions with low boiling points rise highest before condensing, so petroleum gas comes off the top and heavy bitumen stays at the bottom.
Q50. medium
The first oil well in the world was drilled in 1859 in:
Answer: A — Pennsylvania, USA
Edwin Drake drilled the first oil well at Titusville, Pennsylvania, in 1859. In India, oil was first struck at Digboi, Assam, in 1867.
Q52. medium
Which of these actions helps conserve coal and petroleum?
Answer: A — Using public transport, cycling and switching to solar energy
Sharing rides, cycling for short distances and shifting to renewable sources all cut fossil fuel use, extending the life of these limited resources and reducing pollution.
Q54. medium
Which of these is a SOLID fossil fuel?
Answer: A — Coal
Coal is the solid fossil fuel, petroleum is liquid, and natural gas is gaseous. All three formed from buried organic remains.
Q56. medium
Which is the LOWEST grade of coal, with the least carbon?
Answer: A — Peat
Peat is the first stage of coal formation. It contains a lot of moisture, has a low carbon content and gives comparatively little heat when burnt.
Q58. medium
Which overall statement about coal and petroleum is CORRECT?
Answer: A — Both are exhaustible fossil fuels formed over millions of years, and their careful use is essential
This sums up the topic: coal came from buried forests, petroleum from buried marine organisms; both yield many valuable products; both are limited and polluting; so conservation and a shift to renewables are essential.
Q59. medium
Why is coal called a 'dirty' fuel compared with natural gas?
Answer: A — It leaves ash and releases large amounts of soot, sulphur dioxide and carbon dioxide
Coal contains sulphur and non-combustible mineral matter. Burning it produces fly ash, soot, sulphur dioxide and more carbon dioxide per unit of energy than any other fossil fuel.
Q4. hard
Coal, petroleum and natural gas are called FOSSIL FUELS because they:
Answer: A — Were formed from the remains of dead plants and animals buried millions of years ago
Over millions of years, buried organic remains were transformed by heat and pressure into coal, petroleum and natural gas. Since they cannot be replaced in our lifetime, they are exhaustible.
Q6. hard
Coal was formed mainly from:
Answer: A — Dense forests buried under the earth about 300 million years ago
Earthquakes and floods buried vast forests. Cut off from air and subjected to heat and pressure, the plant matter slowly turned into coal.
Q8. hard
The process of heating coal in the ABSENCE of air is called:
Answer: A — Destructive distillation
Destructive distillation of coal produces coke, coal tar and coal gas. Without air, coal decomposes instead of burning.
Q10. hard
Coke is:
Answer: A — A tough, porous, black substance that is almost pure carbon
Coke is nearly pure carbon, hard and porous. It is used in the extraction of metals such as iron from their ores, and in making steel.
Q12. hard
Coal tar is:
Answer: A — A thick black liquid with an unpleasant smell, a mixture of about 200 substances
Coal tar is a complex mixture used to make dyes, explosives, paints, synthetic fibres, drugs, perfumes, plastics and roofing materials.
Q14. hard
Bitumen, used for metalling roads, is now obtained mostly from:
Answer: A — Petroleum processing (it has largely replaced coal-tar products for roads)
Coal tar was once used for road surfacing, but bitumen - a petroleum product - is now preferred because it is more durable and available in larger quantities.
Q16. hard
Coal gas was first used for street lighting in London in:
Answer: A — 1810
Coal gas lit London's streets from 1810 and New York's from 1820. In India, it lit the streets of Delhi from 1900. Today it is mainly an industrial fuel.
Q18. hard
Petroleum is often called 'black gold' because:
Answer: A — It is dark in colour and extremely valuable
Crude petroleum is a dark, oily liquid, and because so many essential products come from it, it is as precious to modern economies as gold.
Q20. hard
The process of separating the various components of petroleum is called:
Answer: A — Refining
Crude oil is separated in a refinery by fractional distillation, since each component has a different boiling point. The plant where this happens is called a petroleum refinery.
Q22. hard
Which of these is NOT a fraction obtained from petroleum?
Answer: A — Coke
Coke comes from coal. Petroleum yields petroleum gas, petrol, kerosene, diesel, lubricating oil, paraffin wax and bitumen.
Q25. hard
Which petroleum fraction fuels heavy motor vehicles and electric generators?
Answer: A — Diesel
Diesel is used in trucks, buses, tractors, trains and generators. It is heavier than petrol and gives more energy per litre.
Q27. hard
Which heavy petroleum fraction is used for paints and road surfacing?
Answer: A — Bitumen
Bitumen is the thick, black residue left after lighter fractions are removed. It is used to metal roads and as a waterproofing material in paints.
Q29. hard
Substances obtained from petroleum and natural gas, used to make detergents, fibres and plastics, are called:
Answer: A — Petrochemicals
Petrochemicals are the raw materials for detergents, synthetic fibres like polyester and nylon, plastics, polythene and many drugs.
Q31. hard
Hydrogen gas obtained from natural gas is used in the production of:
Answer: A — Fertilisers (urea)
Hydrogen from natural gas is combined with nitrogen to make ammonia, which is then converted into urea and other nitrogenous fertilisers.
Q33. hard
The great advantage of natural gas is that it:
Answer: A — Can be transported easily through pipelines and burns cleanly
Pipelines can carry natural gas directly to homes and factories without any storage or transport of containers, and it burns with very little pollution.
Q35. hard
In which Indian states is petroleum mainly found?
Answer: A — Assam, Gujarat, Maharashtra (Mumbai High) and Rajasthan
Assam (Digboi), Gujarat (Ankleshwar), the offshore Mumbai High field and Rajasthan are India's main petroleum-producing areas.
Q37. hard
Which organisation in India is responsible for exploration and production of petroleum?
Answer: A — ONGC (Oil and Natural Gas Corporation)
The Oil and Natural Gas Corporation explores for and produces oil and gas in India, both on land and offshore.
Q39. hard
PCRA in India advises people on how to save petrol and diesel. PCRA stands for:
Answer: A — Petroleum Conservation Research Association
The Petroleum Conservation Research Association promotes fuel-saving practices such as driving at a steady moderate speed, keeping tyres properly inflated and servicing vehicles regularly.
Q41. hard
Which of these is a RENEWABLE alternative to fossil fuels?
Answer: A — Solar energy
Solar, wind, hydro, tidal, geothermal and biomass energy are renewable - they are replenished naturally and do not run out. Coal, petroleum and natural gas are not.
Q43. hard
The main constituent of both natural gas and biogas is:
Answer: A — Methane
Methane (CH4) is the chief component of natural gas and makes up about 65-75% of biogas. It burns cleanly with a blue flame.
Q45. hard
Which is the CLEANEST fossil fuel among these?
Answer: A — Natural gas
Natural gas contains very little sulphur and burns almost completely, releasing far less carbon dioxide per unit of energy and almost no soot compared with coal or oil.
Q47. hard
Petroleum cannot be used directly as a fuel because:
Answer: A — Crude oil is a mixture of many substances that must first be separated by refining
Crude petroleum contains gases, petrol, kerosene, diesel, oils and wax all mixed together. Each has a different use, so refining is necessary before it can be used.
Q49. hard
The correct order of petroleum fractions from LIGHTEST to HEAVIEST is:
Answer: A — Petroleum gas, petrol, kerosene, diesel, lubricating oil, bitumen
Boiling point rises down the list. Petroleum gas boils below room temperature; bitumen is a thick residue that hardly boils at all.
Q51. hard
The first oil well in India was drilled at:
Answer: A — Digboi, Assam
Digboi in Assam saw India's first oil well in 1867 and still has one of the world's oldest working refineries.
Q53. hard
Why is the rate of formation of fossil fuels irrelevant to conservation planning?
Answer: A — They take millions of years to form, so on any human timescale they cannot be replaced
Even though fossil fuels are still forming somewhere, the process takes hundreds of millions of years. We use them millions of times faster than they form, so they are effectively non-renewable.
Q55. hard
Which is the highest-quality coal, with the greatest carbon content?
Answer: A — Anthracite
Coal quality improves in the order peat, lignite, bituminous, anthracite. Anthracite has the highest carbon content, burns with little smoke and gives the most heat.
Q57. hard
Thermal power plants in India use coal mainly to:
Answer: A — Heat water into steam that turns turbines and generates electricity
Burning coal boils water into high-pressure steam. The steam spins a turbine coupled to a generator, producing electricity. Most of India's electricity still comes from coal.
Q60. hard
Why are petroleum refineries usually built near ports or oil fields?
Answer: A — To reduce the cost and risk of transporting large quantities of crude oil
Crude oil arrives in huge tankers or through pipelines. Siting refineries at ports or oil fields cuts transport costs and the risk of spills, and the lighter refined products are then distributed onward.