Coal and Petroleum — Class 8 Science NCERT Solutions (Free)
Free step-by-step NCERT solutions for Class 8 Science chapter "Coal and Petroleum" — 8 important questions with detailed answers for CBSE board exam preparation.
TL;DR: Free step-by-step NCERT solutions for Class 8 Science chapter "Coal and Petroleum" — 8 important questions with detailed answers for CBSE board exam p…
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NCERT Solutions for Class 8 Science — Coal and Petroleum. Step-by-step answers to all 8 textbook questions from this chapter, written for CBSE board preparation and free to use.
Coal and Petroleum — All 8 Questions Solved
Q1. What are fossil fuels?
Fossil fuels are energy sources formed from ancient dead plants and animals buried deep underground over millions of years through heat and pressure. Examples: coal, petroleum, natural gas.
Q2. Define coal. How was coal formed?
Coal is a black, non-metallic mineral used as fuel. It formed from partially decomposed plant matter in ancient forests that was buried, compressed, and heated over 300 million years, converting plant tissues into coal.
Q3. What is coal used for? Name three applications.
Coal uses: 1) Thermal power plants generate electricity, 2) Steel and cement industries as heat source, 3) Cooking and heating in homes, 4) Production of coal tar and coal gas, 5) Coking coal in metallurgy.
Q4. Define petroleum and explain its origin.
Petroleum is a dark, thick liquid hydrocarbon mixture found underground. Formed from remains of tiny marine organisms (plankton) buried 300-400 million years ago, subjected to heat and pressure, converted into crude oil.
Q5. What is fractional distillation? Name three petroleum products.
Fractional distillation separates crude oil into useful products based on boiling points using heated fractionating columns. Products: petrol/gasoline (vehicles), diesel (generators, trucks), kerosene (lamps, jet fuel), lubricating oil (machinery).
Q6. What is natural gas and what are its advantages over coal/petroleum?
Natural gas is a gaseous fuel mixture (methane, ethane) found above petroleum deposits. Advantages: burns cleanly with less pollution, cheaper than petroleum, easier to transport via pipelines, produces more heat per unit, leaves no ash residue.
Q7. What is the environmental impact of coal mining?
Coal mining causes: land degradation and soil erosion, destruction of forests and habitats, water pollution from mining waste, greenhouse gas emissions during burning, acid rain formation, and leaves behind empty mines.
Q8. Why are fossil fuels non-renewable?
Fossil fuels are non-renewable because they take millions of years to form from dead organisms. At current consumption rates, reserves are limited and will eventually deplete. Formation rate is much slower than usage rate.
Coal and Petroleum — Practice MCQs with Answers
Attempt these 20 multiple-choice questions after working through the solutions above. Each carries the correct option and the reasoning behind it, so a wrong answer tells you which idea to revisit.
MCQ 1. Which of the following is an example of a fossil fuel?
- A. Sunlight
- B. Wind
- C. Coal
- D. Water
Answer: C. Coal — Fossil fuels are formed from the decomposition of dead organisms over millions of years under high pressure and temperature. Coal is a prime example of a fossil fuel.
MCQ 2. The slow process of conversion of dead vegetation into coal is called:
- A. Fermentation
- B. Carbonization
- C. Distillation
- D. Oxidation
Answer: B. Carbonization — Carbonization is the slow biochemical process where dead plant matter is converted into coal under high pressure and temperature over millions of years inside the Earth.
MCQ 3. Which of these is NOT a product obtained during the processing of coal?
- A. Coke
- B. Coal gas
- C. Petrol
- D. Coal tar
Answer: C. Petrol — Coke, coal gas, and coal tar are obtained from the destructive distillation of coal. Petrol, however, is a product of petroleum refining.
MCQ 4. Which product of coal is almost a pure form of carbon and is used in the manufacturing of steel?
- A. Coal gas
- B. Coal tar
- C. Coke
- D. Bitumen
Answer: C. Coke — Coke is a tough, porous, and black substance, which is an almost pure form of carbon. It is primarily used as a reducing agent in the extraction of metals and in steel manufacturing.
MCQ 5. Coal tar is a thick, black liquid with an unpleasant smell. Approximately how many substances are commonly present in coal tar?
- A. About 20
- B. About 50
- C. About 100
- D. About 200
Answer: D. About 200 — Coal tar is a complex mixture of about 200 different substances. These substances are separated to obtain various useful products like dyes, drugs, explosives, perfumes, plastics, and paints.
MCQ 6. Which of the following gases is produced during the processing of coal and is used as a fuel in many industries located near the coal processing plants?
- A. Methane
- B. Hydrogen
- C. Coal gas
- D. Carbon dioxide
Answer: C. Coal gas — Coal gas is a mixture of gases like hydrogen, methane, and carbon monoxide, produced during the destructive distillation of coal. It is used as a fuel in industries.
MCQ 7. Petroleum is formed from organisms living in the sea. What happens to these organisms after they die?
- A. They turn into coal
- B. They float on the surface forever
- C. Their bodies settle at the bottom and get covered by layers of sand and clay
- D. They decompose completely without leaving any trace
Answer: C. Their bodies settle at the bottom and get covered by layers of sand and clay — When marine organisms die, their bodies settle at the bottom of the sea. Over millions of years, these layers get covered by sand and clay, and under high temperature and pressure, convert into petroleum and natural gas.
MCQ 8. The process of separating the various constituents (fractions) of petroleum is known as:
- A. Carbonization
- B. Destructive distillation
- C. Fractional distillation
- D. Hydrogenation
Answer: C. Fractional distillation — Fractional distillation is the process used to separate the different components or fractions of petroleum, such as LPG, petrol, diesel, and kerosene, based on their distinct boiling points.
MCQ 9. Which component of petroleum is used as a solvent for dry cleaning?
- A. LPG
- B. Diesel
- C. Petrol
- D. Kerosene
Answer: C. Petrol — Petrol is primarily used as motor fuel for light vehicles. Additionally, it is also used as a solvent for dry cleaning clothes.
MCQ 10. Which petroleum product is used as fuel for jet aircrafts?
- A. Petrol
- B. Diesel
- C. Kerosene
- D. Lubricating oil
Answer: C. Kerosene — Kerosene is a petroleum product used as fuel for stoves, lamps, and is also widely used as jet fuel for aircrafts.
MCQ 11. The residue left after refining petroleum, primarily used for surfacing roads, is:
- A. Paraffin wax
- B. Bitumen
- C. Fuel oil
- D. Petroleum ether
Answer: B. Bitumen — Bitumen is the heaviest and highest boiling point fraction obtained during petroleum refining. It is primarily used for road surfacing and painting.
MCQ 12. What is the main component of natural gas?
- A. Ethane
- B. Propane
- C. Butane
- D. Methane
Answer: D. Methane — Natural gas primarily consists of methane. It is a very important fossil fuel because it can be transported easily through pipelines.
MCQ 13. Which of the following is commonly used as a domestic fuel and stored under pressure in cylindrical containers?
- A. CNG
- B. Natural Gas
- C. LPG
- D. Coal gas
Answer: C. LPG — LPG (Liquefied Petroleum Gas) is stored under pressure in cylinders for domestic use as cooking fuel. CNG (Compressed Natural Gas) is primarily used in vehicles.
MCQ 14. CNG is used as a fuel in vehicles because it is considered a cleaner fuel. Why is it considered cleaner?
- A. It is cheap and easily available
- B. It is highly polluting
- C. It is less polluting and burns completely
- D. It has a strong odor
Answer: C. It is less polluting and burns completely — CNG (Compressed Natural Gas) is considered an environmentally friendly fuel because it produces fewer harmful pollutants when burned compared to petrol or diesel, contributing to less air pollution.
MCQ 15. Why are coal and petroleum considered exhaustible natural resources?
- A. They are found everywhere on Earth
- B. Their formation is a very fast process
- C. Their reserves are limited and take millions of years to form
- D. They are renewable sources of energy
Answer: C. Their reserves are limited and take millions of years to form — Coal and petroleum are exhaustible because their formation takes millions of years, making their available reserves limited. They cannot be replenished quickly on a human timescale.
MCQ 16. What is the primary reason for environmental concerns associated with burning fossil fuels?
- A. Release of water vapor into the atmosphere
- B. Release of oxygen, which depletes the air
- C. Release of carbon dioxide and other pollutants, contributing to global warming and air pollution
- D. Release of inert nitrogen gas
Answer: C. Release of carbon dioxide and other pollutants, contributing to global warming and air pollution — Burning fossil fuels releases large amounts of carbon dioxide, which contributes to global warming. It also releases other pollutants like sulfur dioxide and nitrogen oxides, causing air pollution and acid rain.
MCQ 17. Which of the following is NOT a characteristic of fossil fuels?
- A. They are renewable resources
- B. They are non-renewable resources
- C. They are formed from dead organisms
- D. They take millions of years to form
Answer: A. They are renewable resources — Fossil fuels are non-renewable resources because their formation takes millions of years, and their reserves are limited. Therefore, stating they are renewable is incorrect.
MCQ 18. In India, where can large reserves of natural gas be found?
- A. In the Himalayan mountain ranges
- B. In coastal areas and offshore regions
- C. In arid desert regions
- D. Near active volcanic sites
Answer: B. In coastal areas and offshore regions — Large reserves of natural gas in India are predominantly found in coastal areas and offshore regions, such as the Krishna Godavari basin, Mumbai High, Rajasthan, and Tripura.
MCQ 19. Which of the following is a common application of paraffin wax, a petroleum product?
- A. Fuel for heavy motor vehicles
- B. Road surfacing
- C. Making candles, Vaseline, and ointments
- D. Lubricating heavy industrial machinery
Answer: C. Making candles, Vaseline, and ointments — Paraffin wax is a white, soft, solid wax obtained from petroleum. It is widely used for making candles, Vaseline, cosmetics, and ointments.
MCQ 20. The process of heating coal strongly in the absence of air to obtain various useful products is known as:
- A. Refining
- B. Carbonization
- C. Destructive distillation
- D. Fractional distillation
Answer: C. Destructive distillation — Destructive distillation is the process of heating a substance like coal in the absence of air to break it down into various products such as coke, coal tar, and coal gas.
How to Use These Solutions
Attempt each question yourself first and only then compare with the worked answer. Marks in the CBSE board exam are awarded for the METHOD as much as the final result, so reproduce the steps rather than memorising the last line. Where a solution states a law, a formula or a definition, learn that wording — examiners look for it.
Related practice for this chapter: chapter MCQs, previous-year questions, revision notes and sample papers.