Science Notes for Chapter 3 Coal and Petroleum Class 8 - FREE PDF Download
FAQs on Coal and Petroleum Class 8 Science Chapter 3 CBSE Notes - 2025-26
1. What is the key term 'carbonisation' in the context of coal formation?
Carbonisation is the slow chemical process of converting dead vegetation, like ancient ferns and forests, into coal. This transformation occurs over millions of years under conditions of high temperature and high pressure deep within the Earth's crust.
2. What are the main products obtained when coal is processed?
When coal is processed in industry, three main products are obtained:
- Coke: A tough, porous, and black substance, almost the pure form of carbon, used in manufacturing steel.
- Coal Tar: A thick, black liquid with an unpleasant smell, used as a starting material for manufacturing various substances like synthetic dyes, drugs, and paints.
- Coal Gas: A flammable gas produced during the processing of coal to get coke, used as a fuel in many industries.
3. How does the formation of petroleum differ from the formation of coal?
The primary difference lies in their origin. Coal is formed from the remains of terrestrial vegetation (like trees and ferns) buried in swamps millions of years ago. In contrast, petroleum and natural gas were formed from the remains of tiny marine organisms (like algae and plankton) that settled at the bottom of seas and oceans.
4. What is the process used to separate petroleum into useful substances like petrol and diesel?
The process of separating the various constituents or fractions of petroleum is called petroleum refining. This is carried out in a petroleum refinery using a method known as fractional distillation, which separates the crude oil into different components based on their varying boiling points.
5. Can you provide a quick summary of the main uses of petroleum products mentioned in Class 8 Science?
The key petroleum products and their uses are:
- LPG (Liquefied Petroleum Gas): Fuel for home and industry.
- Petrol: Fuel for light motor vehicles and aviation.
- Diesel: Fuel for heavy motor vehicles and electric generators.
- Lubricating Oil: Used for lubrication of machinery.
- Paraffin Wax: Used in ointments, candles, and vaseline.
- Bitumen: Used for surfacing roads and in paints.
6. Why is natural gas considered a very important fossil fuel?
Natural gas is considered a very important fossil fuel because it is a cleaner-burning fuel compared to coal and petroleum, producing fewer pollutants. It is also easy to transport through a network of pipelines directly to homes and industries. When compressed, it is known as CNG (Compressed Natural Gas) and is used as a less-polluting fuel for vehicles.
7. Why are resources like coal and petroleum classified as 'exhaustible natural resources'?
Coal and petroleum are classified as exhaustible natural resources because their supply is finite and limited. They were formed from the remains of living organisms over millions of years, a process that cannot be replicated in a short time. Therefore, once the existing reserves are used up, they cannot be replenished quickly, making their conservation essential.
8. What are the key strategies for conserving fossil fuels as suggested by the PCRA?
In India, the Petroleum Conservation Research Association (PCRA) advises several simple strategies to save petrol and diesel while driving. For a quick revision, these include:
- Driving at a constant and moderate speed.
- Switching off the engine at traffic lights or places where you have to wait.
- Ensuring correct tyre pressure.
- Ensuring regular vehicle maintenance.
9. What is the fundamental difference between inexhaustible and exhaustible natural resources?
The fundamental difference is their availability. Inexhaustible natural resources, like sunlight and air, are present in unlimited quantities in nature and are not likely to be depleted by human activities. In contrast, exhaustible natural resources, such as forests, wildlife, and fossil fuels, are limited in stock and can be completely used up by human consumption.











