Coal and Petrolium notes for class 8 CBSE

Detailed Notes on Coal and Petroleum - Class 8 CBSE

Chapter 5: Coal and Petroleum

Introduction

Coal and petroleum are classified as fossil fuels, which are energy-rich substances formed over millions of years from the remains of ancient living organisms such as plants and animals. These resources are buried deep under the earth's surface and transformed by natural processes involving heat, pressure, and the absence of oxygen. As non-renewable resources, they cannot be replenished within a human timescale once depleted. The text highlights: "In our everyday life, we use a large number of materials for our basic needs. Some of these materials are obtained from nature, while others are man-made. Air, water, soil, coal, petroleum, natural gas, metallic and non-metallic minerals, forests, etc., are all man-made resources. On the other hand, plastics, synthetic fibers, paints, drugs, explosives, etc., are man-made. All the natural resources can be classified into two main groups." This classification underscores the distinction between natural and synthetic materials, emphasizing the finite nature of fossil fuels.

Natural Resources

Natural resources are substances or materials available in the environment that can be utilized for human needs, such as food, shelter, and energy. They are broadly categorized into two types:

Inexhaustible Resources: These are resources available in abundant quantities and unlikely to be depleted by human use. Examples include air, sunlight, and water. The text explains: "The term 'inexhaustible' means something which cannot be used up completely. Those natural resources which are present in unlimited quantity in nature and are not likely to be exhausted by human activity are called inexhaustible resources, e.g., air, sunlight, and water. There is a never-ending supply of these resources."
Exhaustible Resources: These are limited in quantity and can be exhausted through human activities. Fossil fuels like coal, petroleum, and natural gas fall into this category. The text notes: "The term 'exhaustible' means something which can get exhausted or finished. Those resources which are present in a limited quantity in nature and can be exhausted by human activities are called exhaustible resources." This distinction is critical as it highlights the need for conservation efforts to sustain these resources for future generations.

Fossil Fuels

Fossil fuels are the natural fuels derived from the remains of prehistoric plants and animals that were buried under layers of earth millions of years ago. The process involves the gradual decomposition of these organic materials under high temperature and pressure in the absence of oxygen, transforming them into energy-rich substances. The text states: "The natural fuels formed from the remains of living organisms buried under the earth long ago, are called fossil fuels. Coal, petroleum, and natural gas are fossil fuels." The formation process took millions of years, making these resources non-renewable. For instance, coal formation began 300 million years ago from land plants, while petroleum originated from marine organisms buried under the sea.

Coal

Formation: Coal is a complex process that began approximately 300 million years ago during the Carboniferous period. Large land plants and trees died and were buried under layers of sediment due to natural events like flooding. Over time, these remains were subjected to intense heat and pressure in the absence of air, leading to the formation of coal. The text elaborates: "How Fossil Fuels were Formed: The dead remains of living organisms (plants and animals) buried under the earth long, long ago got covered by layers of the earth. With high temperature and pressure, these were slowly converted into fossil fuels."

Types: Coal varies based on its carbon content and age, classified into four main types:

Peat: The earliest stage with the lowest carbon content.
Lignite: A brownish coal with moderate carbon content.
Bituminous: The most common type, widely used, with higher carbon content.
Anthracite: The hardest and purest form with the highest carbon content.

Uses: Coal serves multiple purposes in modern society:

Energy Production: It is a primary fuel in thermal power plants for generating electricity.
Industrial Fuel: Coal gas, derived during its processing, is used as an industrial fuel.
Metallurgy: Coke, produced from coal, is essential in steel manufacturing and metal extraction.

Products of Coal:

Coke: A tough, porous, black substance almost pure carbon, used as a fuel and reducing agent in metallurgy. The text notes: "Coke is a tough, porous, and black substance. It is almost pure form of carbon. Coke is used in the manufacture of steel and in the extraction of many metals."
Coal Tar: A thick, black liquid with a pungent odor, containing about 200 substances. It is a key raw material for synthetic dyes, drugs, explosives, perfumes, plastics, and paints. The text states: "Coal tar is a black, thick liquid with an unpleasant smell. It is a mixture of about 200 substances. Products obtained from coal tar are used as starting materials for manufacturing various substances used in everyday life and in industry, like synthetic dyes, drugs, explosives, perfumes, plastics, paints, etc."
Coal Gas: A gaseous fuel produced during coke manufacturing, used for heating and lighting purposes. The text mentions: "Coal gas is obtained during the processing of coal to get coke. It is used as a fuel."

Petroleum

Formation: Petroleum, also known as crude oil, originated from the remains of tiny marine organisms like zooplankton and algae. These organisms were buried under the sea millions of years ago, and over time, heat and pressure transformed them into liquid hydrocarbons. The text explains: "Petroleum was formed from the dead organisms (like tiny plants and animals like zooplankton) buried under the sea millions of years ago."

Refining: The refining process involves fractional distillation, where petroleum is heated, and its components are separated based on boiling points into various fractions. The text notes: "The process of separating the various constituents/fractions of petroleum is known as refining."

Constituents: Petroleum is a complex mixture of hydrocarbons, organic compounds made of hydrogen and carbon.

Occurrence: It is found deep beneath the earth's surface, trapped between layers of impervious rocks, requiring drilling for extraction. The text states: "Petroleum occurs deep under the surface of the earth between two layers of impervious rocks."

Extraction: Extracted through drilling wells, petroleum is then transported to refineries for processing.

Products and Uses:

Petroleum Gas (LPG): A flammable gas used as a fuel for cooking and heating in homes and industries. The text: "Petroleum gas, also called liquefied petroleum gas or LPG, is used as a fuel for home and industry."
Petrol: A volatile fuel used in internal combustion engines of cars, scooters, and motorcycles. The text: "Petrol is used as a fuel for vehicles like cars, scooters, and motorcycles."
Kerosene: Used for lighting in lamps and as aviation fuel in jet aircraft. The text: "Kerosene is used as a fuel for stoves, lamps, and for jet aircraft (jet planes)."
Diesel: Powers heavy motor vehicles and electric generators. The text: "Diesel is used as a fuel for heavy motor vehicles and in electric generators."
Lubricating Oil: Reduces friction in machinery and engines. The text: "Lubricating oil is used for lubrication in machines and engines."
Paraffin Wax: Utilized in making candles, vaseline, ointments, and wax paper. The text: "Paraffin wax is used for making candles, vaseline, ointments, wax paper, and other articles."
Bitumen: A viscous material used for road construction. The text: "Bitumen is used for making roads."

Natural Gas

Composition: Primarily methane (CH₄) with trace amounts of ethane and propane. The text confirms: "Natural gas consists mainly of methane, with small amounts of ethane and propane."

Occurrence: Often found alongside petroleum deposits, trapped under impervious rock layers.

Uses:

Domestic and Industrial Fuel: Used for cooking, heating, and power generation.
Compressed Natural Gas (CNG): A cleaner fuel alternative for vehicles. The text: "Compressed Natural Gas (CNG) is used as a fuel in vehicles."

Advantages: Burns with a clean flame, produces minimal ash and smoke, and is easily transported via pipelines. The text: "Natural gas is used as a fuel because it burns without smoke and leaves very little ash after burning."

Energy Resources

Fossil fuels (coal, petroleum, natural gas) are the backbone of global energy production, powering industries, transportation, and households. However, they are exhaustible, and their depletion necessitates the adoption of renewable energy sources like solar, wind, and hydropower. The text notes: "Most of the energy that we use today comes mainly from the three exhaustible resources of the earth, viz., coal, petroleum, and natural gas."

Petrochemicals

Petrochemicals are chemicals derived from petroleum and natural gas, serving as raw materials for synthetic products. Examples include polythene, PVC, nylon, synthetic rubber, and explosives. The text states: "Many useful chemicals (or substances) are obtained from petroleum and natural gas. These are termed as petrochemicals."

Conservation of Fossil Fuels

Given their limited availability, fossil fuels must be used judiciously. The text advises: "We have seen that fossil fuels are non-renewable sources of energy. They need to be conserved. We should use fuels wisely." This involves promoting energy efficiency, exploring renewable alternatives, and reducing wasteful consumption to ensure sustainability.

Questions and Answers

Q1: What are fossil fuels?

A1: Fossil fuels are coal, petroleum, and natural gas formed from the remains of dead plants and animals buried under the earth millions of years ago. (Text: "The natural fuels formed from the remains of living organisms buried under the earth long ago, are called fossil fuels.")

Q2: How is coal formed?

A2: Coal is formed by the decomposition of large land plants and trees buried under the earth 300 million years ago under heat and pressure. (Text: "How Fossil Fuels were Formed: The dead remains of living organisms (plants and animals) buried under the earth long, long ago got covered by layers of the earth. With high temperature and pressure, these were slowly converted into fossil fuels.")

Q3: What are the uses of petroleum?

A3: Petroleum is used to produce LPG, petrol, kerosene, diesel, lubricating oil, paraffin wax, and bitumen. (Text: "The various constituents of petroleum and their uses: Petroleum gas or LPG, petrol, kerosene, diesel, lubricating oil, paraffin wax, bitumen.")

NCERT Questions Solutions

Q1: Name three useful products of coal.

Ans: Three useful products of coal are coke, coal tar, and coal gas. (Text: "Products of coal: Coke, coal tar, and coal gas.")

Q2: What are the advantages of using CNG as a fuel?

Ans: CNG burns with a clean flame, produces less pollution, and is safer to use due to its low risk of leakage. (Text: "Natural gas is used as a fuel because it burns without smoke and leaves very little ash after burning.")

Q3: Explain why fossil fuels are exhaustible natural resources.

Ans: Fossil fuels are exhaustible because they take millions of years to form and cannot be replenished once used up. (Text: "We have seen that fossil fuels are non-renewable sources of energy.")