NCERT Science Notes - Class 8
Chapter 3 - Coal and Petroleum

Welcome to AJs Chalo Seekhen. This webpage is dedicated to Class 8 | Science | Chapter 3 - Coal and Petroleum. The chapter delves into the formation, types, and uses of fossil fuels. It explains how coal is formed from dead plant matter over millions of years under heat and pressure, and how petroleum, or crude oil, originates from marine organisms. The chapter also covers natural gas, a cleaner fuel, and highlights the environmental impact of using these non-renewable resources. Students learn about the importance of conserving fossil fuels and the need for sustainable energy sources.

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NCERT Science Notes - Class 8
Chapter 3 - Coal and Petroleum

Definition

• Natural Resources: Materials obtained from nature that fulfill our basic needs. Examples include air, water, soil, and minerals.
  
  

Classification of Natural Resources

Natural resources can be classified into two main categories:

1. Inexhaustible Natural Resources
   • Definition: Resources that are available in unlimited quantities and are not likely to be depleted by human activities.
   • Examples:
     • Sunlight: Constantly available and essential for life.
     • Air: Essential for breathing, present in unlimited supply.
2. Exhaustible Natural Resources
   • Definition: Resources that are limited in quantity and can be depleted through human activities.
   • Examples:
     • Forests: Provide timber, fuel, and habitat but can be cut down.
     • Wildlife: Animals and plants that can become endangered or extinct if not protected.
     • Minerals: Such as coal, petroleum, and natural gas; these are finite resources that take millions of years to form.

Activity 3.2 - Group Activity on Resource Consumption

Understanding Exhaustible Natural Resources

Analogy

• The eatables in the container represent the total availability of an exhaustible natural resource (e.g., coal, petroleum, natural gas).

1. Consumption Patterns:
   • Each group may exhibit different consumption behaviors.
   • Earlier generations might display greediness by consuming excessively.
   • Some earlier generations may show concern for future generations by conserving resources.
2. Exhaustible Natural Resources:
   • Examples: Coal, petroleum, natural gas.
   • Formation: These resources were formed from the dead remains of living organisms (fossils).
3. Terminology:
   • Collectively, coal, petroleum, and natural gas are referred to as fossil fuels.

3.1 - Coal

Overview

• Description: Coal is a hard, black fuel used for cooking, electricity generation, and in various industries.
  
  

• Origin: Formed approximately 300 million years ago from dense forests in wetland areas.
• Process:
  • Forests were buried under soil due to natural events (e.g., flooding).
  • Over time, increased soil deposition led to compression and rising temperatures.
  • Dead vegetation was converted to coal through a process called carbonisation.
    
    

• Type: Classified as a fossil fuel due to its formation from organic matter.
  
  

1. Coke:
   • Tough, porous, black substance; almost pure carbon.
   • Uses: Manufacture of steel and extraction of metals.
2. Coal Tar:
   • Black, thick liquid with an unpleasant smell; a mixture of about 200 substances.
   • Uses:
     • Starting material for synthetic dyes, drugs, explosives, perfumes, plastics, paints, and roofing materials.
     • Naphthalene balls for repelling moths are also derived from coal tar.
   • Note: Bitumen, a petroleum product, is now often used instead of coal tar for road metalling.
3. Coal Gas:
   • Produced during coal processing for coke.
   • Uses: Fuel in industries near processing plants.
   • Historical Significance: First used for street lighting in London (1810) and New York (1820). Now primarily used for heat.

3.2 - Petroleum

Overview

• Usage:
  • Petrol: Fuel for light vehicles (motorcycles, scooters, cars).
  • Diesel: Fuel for heavy vehicles (trucks, tractors).
    
    

• Origin: Formed from marine organisms.
• Process:
  • When these organisms died, their remains settled at the sea bottom.
  • Over millions of years, layers of sand and clay covered the remains.
  • The absence of air, combined with high temperature and pressure, transformed the organic matter into petroleum and natural gas.
    
    

• Composition: Contains petroleum oil and natural gas.
• Layering: In deposits, petroleum and gas are found above water due to their lighter density; oil and gas do not mix with water.

Fun Facts About Oil Discovery 🌍⛽️

Refining of Petroleum 🛢️

• What is Petroleum?
  Petroleum is a dark oily liquid with an unpleasant odor, composed of various constituents such as:
  • Petroleum gas
  • Petrol
  • Diesel
  • Lubricating oil
  • Paraffin wax
• Refining Process:
  The separation of these constituents is known as refining, which is carried out in a petroleum refinery.
• Petrochemicals:
  Many useful substances derived from petroleum and natural gas are called petrochemicals. They are essential in manufacturing:
  • Detergents
  • Fibres (e.g., polyester, nylon, acrylic)
  • Polythene and other man-made plastics
• Hydrogen Production:
  Hydrogen gas obtained from natural gas is used in producing fertilizers (like urea).
• Commercial Importance:
  Due to its immense value, petroleum is often referred to as 'black gold'.

Constituents of Petroleum and Their Uses

3.3 - Natural Gas

1. Importance:
   Natural gas is a crucial fossil fuel due to its ease of transportation through pipes.
   
   
2. Compressed Natural Gas (CNG):
   1. Natural gas is stored under high pressure as CNG.
   2. Uses:
      1. Power generation
      2. Transport fuel: CNG is being used in vehicles because it is less polluting and considered a cleaner fuel.
         
         
3. Direct Use:
   1. CNG can be directly burned in homes and factories through a network of pipelines.
   2. Such pipelines are found in Vadodara (Gujarat), parts of Delhi, and other locations.
      
      
4. Manufacturing:
   Natural gas is also a starting material for producing various chemicals and fertilizers.
   
   
5. Reserves in India:
   India has significant reserves of natural gas, found in:
   1. Tripura
   2. Rajasthan
   3. Maharashtra
   4. Krishna Godavari delta
      
      
6. Formation:
   1. Boojho asks if coal, petroleum, and natural gas can be made in the laboratory from dead organisms.
   2. Paheli responds that their formation is a very slow process and the necessary conditions for their formation cannot be replicated in the lab.

3.4 - Some Natural Resources are Limited

1. Exhaustible Natural Resources:
   1. Resources like fossil fuels, forests, and minerals are exhaustible.
   2. Fossil Fuels:
      1. Coal and petroleum are fossil fuels formed from dead organisms over millions of years.
      2. Known reserves of these fuels will last only a few hundred years.
         
         
2. Environmental Impact:
   1. Burning fossil fuels is a major cause of air pollution and is linked to global warming.
   2. It is necessary to use these fuels only when absolutely necessary to:
      1. Improve the environment
      2. Reduce the risk of global warming
      3. Ensure availability for a longer period
         
         
3. Petroleum Conservation Research Association (PCRA) Tips for Saving Fuel:
   1. Drive at a constant and moderate speed as much as possible.
   2. Switch off the engine at traffic lights or when waiting.
   3. Ensure correct tyre pressure.
   4. Conduct regolar maintenance of the vehicle.

NCERT Science Notes - Class 8 | Chapter 3 - Coal and Petroleum