Coal and Petroleum Full Notes + Step-by-Step Exercise Solutions
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1) Natural Resources & Fossil Fuels
Materials we use daily come from nature (air, water, soil, minerals, plants, animals) or are man-made. Based on availability:
- Inexhaustible resources – practically unlimited; cannot be exhausted by human use (e.g., sunlight, air).
- Exhaustible resources – limited in amount; can be used up (e.g., forests, wildlife, minerals, coal, petroleum, natural gas).
Fossil fuels (coal, petroleum, natural gas) formed from the dead remains of organisms over millions of years under high pressure and temperature and absence of air, hence called fossil fuels.
2) Coal: Story, Products & Uses
2.1 Formation (Carbonisation)
About 300 million years ago, dense forests in swampy lowlands got buried under sediments. As layers piled up, pressure and temperature increased, slowly converting dead vegetation into coal. This slow conversion is called carbonisation.
2.2 Important Industrial Products from Coal
- Coke – tough, porous, black; almost pure carbon. Uses: manufacture of steel; extraction of many metals.
- Coal tar – black, thick liquid with a strong smell; mixture of ~200 substances. Uses: starting material for synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic and roofing materials; naphthalene balls. (Roads now use bitumen instead of coal tar for surfacing.)
- Coal gas – obtained during processing of coal to get coke; used as a fuel near coal processing plants.
3) Petroleum: Formation & Refining
3.1 Formation
Petroleum formed from sea organisms. Their dead bodies were buried under sand and clay on the sea floor. Over millions of years, high pressure, high temperature and absence of air transformed them into petroleum and natural gas. In the rock layers, oil and gas (lighter) lie above water and below an impervious cap rock.
3.2 Refining of Petroleum
Crude petroleum is a dark, oily, smelly liquid—a mixture of many fractions. Refining in a petroleum refinery separates the mixture into useful fractions:
| S.No. | Constituent | Common Uses |
|---|---|---|
| 1 | Petroleum gas (LPG) | Fuel for homes & industry |
| 2 | Petrol (gasoline) | Motor fuel, aviation fuel, dry-cleaning solvent |
| 3 | Kerosene | Stoves, lamps, jet aircraft fuel |
| 4 | Diesel | Heavy vehicles, generators |
| 5 | Lubricating oil | Lubrication |
| 6 | Paraffin wax | Ointments, candles, vaseline |
| 7 | Bitumen | Paints, road surfacing |
4) Natural Gas & CNG
Natural gas can be transported easily through pipelines and stored under pressure as Compressed Natural Gas (CNG). It is used for power generation and as a cleaner fuel for vehicles (less polluting than petrol/diesel). CNG can be supplied to homes and factories via pipeline networks.
5) These Resources Are Limited – Use Them Wisely
Fossil fuels took millions of years to form; known reserves may last only a few hundred years. Burning them causes air pollution and contributes to global warming. Therefore we must conserve:
- Drive at constant, moderate speed.
- Switch off the engine at red lights or long waits.
- Maintain correct tyre pressure.
- Ensure regular maintenance of the vehicle.
6) Textbook Exercises – Fully Solved (Q1–Q9)
Q1. What are the advantages of using CNG and LPG as fuels?
Answer (stepwise):
- Cleaner burning: Less soot, sulphur and particulate emissions; reduced air pollution.
- Higher calorific value: Efficient energy per unit mass/volume.
- Convenience: CNG can be piped; LPG cylinders are portable and easy to use.
- Less engine deposits: Longer engine life and lower maintenance (for vehicles).
- Safety & control: Easy ignition and flame control for domestic use.
Q2. Name the petroleum product used for surfacing of roads.
Answer: Bitumen (now widely used in place of coal tar for road surfacing).
Q3. Describe how coal is formed from dead vegetation. What is this process called?
Answer (stepwise):
- Ancient dense forests in swampy lowlands were buried by sediments.
- Over long periods, increasing pressure and temperature acted on the buried plant matter.
- In the absence of air, chemical changes gradually converted it into coal.
This slow conversion of dead vegetation into coal is called carbonisation.
Q4. Fill in the blanks.
- (a) Fossil fuels are coal, petroleum and natural gas.
- (b) Process of separation of different constituents from petroleum is called refining.
- (c) Least polluting fuel for vehicles is CNG (Compressed Natural Gas).
Q5. Tick True/False.
- (a) Fossil fuels can be made in the laboratory. — False (conditions/time not reproducible).
- (b) CNG is more polluting fuel than petrol. — False (CNG is cleaner).
- (c) Coke is almost pure form of carbon. — True.
- (d) Coal tar is a mixture of various substances. — True.
- (e) Kerosene is not a fossil fuel. — False (it is a petroleum fraction).
Q6. Explain why fossil fuels are exhaustible natural resources.
Answer: They formed from dead organisms over millions of years under special conditions, while our rate of consumption is far faster than their natural formation. Their reserves are limited and can be used up, hence “exhaustible”.
Q7. Describe characteristics and uses of coke.
Answer: Coke is a tough, porous, black solid and is almost pure carbon. It burns with little smoke and high heat. Uses: extraction of metals (as a reducing agent), and in the manufacture of steel.
Q8. Explain the process of formation of petroleum.
Answer (stepwise):
- Marine organisms died and settled on the sea bed; layers of sand and clay covered them.
- Over millions of years, absence of air, high temperature, and high pressure changed them into petroleum and natural gas.
- In the strata, oil and gas (lighter) accumulated above water within a porous reservoir rock capped by an impervious layer.
Q9. Power shortage (%) in India, 1991–1997 — Draw a graph.
Data:
| Year | 1991 | 1992 | 1993 | 1994 | 1995 | 1996 | 1997 |
|---|---|---|---|---|---|---|---|
| Shortage (%) | 7.9 | 7.8 | 8.3 | 7.4 | 7.1 | 9.2 | 11.5 |
How to plot (stepwise):
- Draw X-axis (Years) from 1991 to 1997 at equal intervals.
- Draw Y-axis (Shortage %) from 0 to at least 12% with equal scaling.
- Mark each year’s point at its shortage value; join points with straight line segments for a line graph (or draw bars for a bar graph).
- Label axes and the graph title clearly.
Inline example (simple SVG line chart, scales approximated):
Your school may ask you to draw it by hand; follow the “How to plot” steps above.
7) Extra Practice & Quick Revision
- Carbonisation converts plant remains into coal.
- Coke ≈ pure carbon; coal tar = many substances; coal gas = fuel.
- Refining splits crude oil into LPG, petrol, kerosene, diesel, lube oil, paraffin wax, bitumen.
- CNG is cleaner than petrol/diesel.
- Plan trips to avoid traffic; car-pool or use public transport.
- Maintain vehicles; correct tyre pressure saves fuel.
- Switch off engine at long halts.
Self-Practice Questions
- Define fossil fuels. Why are they called exhaustible resources?
- List three differences between coal and petroleum products.
- State two reasons why CNG is promoted for city transport.
- Explain why petroleum is called “black gold”.
- From the table of petroleum fractions, match each item with a product used at home.
8) Glossary (Key Terms)
- Fossil fuels: Coal, petroleum, natural gas—formed from dead organisms over millions of years.
- Carbonisation: Slow conversion of plant remains into coal under high pressure/temperature and absence of air.
- Refining (of petroleum): Separation of crude oil into useful fractions.
- Coke: Tough, porous, nearly pure carbon (from coal); used in steel/metals.
- Coal tar: Thick black liquid with many organic compounds (dyes, drugs, perfumes, plastics...).
- Bitumen: Heavy petroleum fraction; used for road surfacing and paints.
- CNG: Compressed Natural Gas; cleaner transport fuel.
— End of Notes & Solutions —