Coal and Petroleum – Short Answer Type Questions
Class 8 • Science
Chapter 5 — Coal and Petroleum
CBSE Board Examinations — Systematic overview
Topic A — Basics & Definitions (Q1–Q8)
1. What are fossil fuels?
Fossil fuels are energy-rich fuels formed from remains of plants and animals over millions of years.
2. Name two major fossil fuels.
Coal and petroleum (crude oil).
3. Define crude oil.
Crude oil is a complex mixture of hydrocarbons found underground and used as a primary energy source and raw material.
4. What is natural gas mainly composed of?
Methane (CH₄) is the main component of natural gas.
5. What is LPG?
LPG (liquefied petroleum gas) is mainly propane and butane stored as a liquid under pressure for domestic use.
6. Why are fossil fuels called non-renewable?
Because they form over millions of years and cannot be replenished within human timescales.
7. What is a hydrocarbon?
A compound made of hydrogen and carbon atoms (e.g., methane, octane).
8. Give one use of fossil fuels besides fuel.
Fossil fuels (petroleum) are raw materials for plastics, synthetic fibres and chemicals.
Topic B — Formation & Types of Coal (Q9–Q16)
9. How is coal formed?
Coal forms from plant remains buried under sediments and transformed by heat and pressure (carbonisation).
10. List the main ranks of coal.
Peat, lignite, bituminous coal and anthracite (from low to high carbon content).
11. Which coal is called brown coal?
Lignite is commonly called brown coal.
12. Which coal has the highest calorific value?
Anthracite has the highest calorific value because of high carbon content.
13. What impurities are found in coal?
Sulfur, ash-forming minerals and moisture are common impurities in coal.
14. Name one use of bituminous coal.
It is widely used in thermal power plants to generate electricity.
15. What is peat?
Peat is partially decayed plant matter, the earliest stage in coal formation.
16. Why does carbon content increase with coal rank?
With increased heat and pressure over time, volatile components decrease and carbon concentration increases.
Topic C — Uses & Problems of Coal (Q17–Q22)
17. What is coke and how is it obtained?
Coke is a high-carbon fuel obtained by heating coal in absence of air (destructive distillation); used in metallurgy.
18. Name two industrial uses of coal.
Electricity generation and production of coke for iron and steel making.
19. Mention one environmental drawback of using coal.
Burning coal emits pollutants like CO₂ and SO₂ causing air pollution and acid rain.
20. How does coal mining affect environment?
Mining leads to land degradation, habitat loss, water pollution and safety hazards.
21. Give one health problem from coal pollution.
Respiratory illnesses such as bronchitis and asthma.
22. Suggest one measure to reduce pollution from coal.
Use cleaner fuels, install pollution-control devices and improve efficiency of combustion.
Topic D — Petroleum & Crude Oil (Q23–Q30)
23. How is petroleum formed?
From remains of marine organisms buried under sediments, transformed by heat and pressure over millions of years.
24. What is crude oil?
Crude oil is unrefined petroleum, a complex mixture of hydrocarbons of various molecular sizes.
25. Where is crude oil found?
In underground reservoirs within sedimentary rock layers, often associated with natural gas.
26. Name one impurity commonly present in crude oil.
Sulfur compounds are common impurities in crude oil.
27. What is meant by refining?
Refining is the process of separating crude oil into useful fractions through distillation and other treatments.
28. Why is fractional distillation used for crude oil?
Because different hydrocarbons have different boiling points and can be separated in a fractionating column.
29. What is petrol fraction used for?
Petrol (gasoline) is used as fuel in petrol engines (cars, two-wheelers).
30. What is bitumen used for?
Bitumen is used in road construction and roofing as a heavy, sticky residue.
Topic E — Fractional Distillation Details (Q31–Q36)
31. Where do lighter fractions condense in the fractionating column?
Lighter fractions condense near the top of the column where the temperature is lower.
32. Which fraction is used as aviation fuel?
Kerosene is commonly used as aviation fuel (jet fuel).
33. Which fraction is used for lubrication?
Lubricating oil is the fraction used to reduce friction between moving parts.
34. What is naphtha used for?
Naphtha is used as feedstock in petrochemical industries to make plastics and chemicals.
35. Explain in one line why fractions separate.
Fractions separate because components have different boiling points and condense at different heights in the column.
36. What happens to residue left at bottom of distillation column?
The heavy residue is processed into bitumen or heavy oils and can be used for road surfacing or further refining.
Topic F — Uses & Applications (Q37–Q42)
37. Name two transport fuels derived from petroleum.
Petrol (gasoline) and diesel.
38. Give one industrial use of petroleum aside from fuel.
Production of plastics and synthetic fibres from petrochemical feedstocks.
39. How is LPG commonly used domestically?
LPG is used for cooking in households and in small-scale heating.
40. Why are lubricants important?
They reduce friction and wear between moving machine parts and improve efficiency.
41. What is liquefied natural gas (LNG)?
LNG is natural gas cooled to liquid form for transport and storage at low temperatures.
42. Name one use of bitumen besides roads.
Bitumen is used in roofing and waterproofing applications.
Topic G — Environmental Impact & Safety (Q43–Q50)
43. What greenhouse gas is mainly released from burning fossil fuels?
Carbon dioxide (CO₂) is the main greenhouse gas released.
44. How do sulfur compounds from burning fossil fuels affect the environment?
They form sulfur dioxide which can lead to acid rain, harming plants and aquatic life.
45. Mention one consequence of oil spills.
Oil spills damage marine ecosystems, kill wildlife and pollute coastlines.
46. Suggest two ways to conserve fossil fuels.
Use public transport, improve fuel efficiency, switch to renewable energy, and reduce wastage.
47. Why is it important to use cleaner fuels?
Cleaner fuels emit less pollution and reduce health hazards and greenhouse gas emissions.
48. Give one safety rule for handling LPG cylinders.
Check for leaks with soapy water, keep cylinders upright and store away from heat sources.
49. What is a fuel reserve?
A reserve is the quantity of fuel that can be extracted economically with current technology.
50. How can studying coal and petroleum help students?
It helps understand energy sources, uses, environmental impacts and the need for conservation and alternatives.