Coal And Petroleum Class 8 Science Chapter 3 Notes

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Coal And Petroleum Class 8 Science Chapter 3 Notes

Type of Natural resources

Inexhaustible Natural Resources: These resources are abundant in nature and cannot be depleted by human activities. Examples include sunlight and air, which are available in unlimited quantities.

Exhaustible Natural Resources: These resources have a limited quantity in nature and can be depleted through human activities. Examples include forests, wildlife, minerals, coal, petroleum, and natural gas. They are not available in infinite amounts and can be exhausted over time.

Fossil Fuels

• Fossil fuels are sources of energy that come from ancient plants and animals.
• These fuels have been formed over millions of years and are found deep within the Earth.
• Fossil fuels are non-renewable, which means they cannot be easily replaced once they are used up.

Coal

• Coal is a type of fuel that is black in color and as hard as stone.
• It is used for cooking food and was also used in old railway engines to produce steam and run the engine.
• Coal is used in thermal power plants to produce electricity.
• It is also used as a fuel in different industries.

Story of Coal

• Around 300 million years ago, there were dense forests on Earth in wetland areas.
• Over time, these forests got buried under soil due to natural processes like flooding.
• As more soil piled up on top of the forests, they were squeezed and compressed.
• The temperature also increased as they sank deeper underground.
• Under high pressure and high temperature, the dead plants slowly turned into coal.
• This process of converting dead vegetation into coal is called carbonisation because coal contains mainly carbon.
• Coal is also called a fossil fuel because it was formed from the remains of plants that lived long ago.
• When coal is heated in the presence of air, it burns and produces mainly carbon dioxide gas.
• Industries process coal to obtain useful products like coke, coal tar, and coal gas.

Coke

• Coke is a tough, porous, and black substance.
• It is made up of almost pure carbon.
• Coke is used in the manufacturing of steel and in the extraction of many metals.

Coal Tar

• Coal tar is a black, thick liquid with an unpleasant smell.
• It is made up of a mixture of about 200 different substances.
• Products derived from coal tar are used as starting materials for making various things we use in everyday life and industries.
• Some of the substances made from coal tar include synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, and roofing materials.
• Naphthalene balls, which are used to repel moths and other insects, are also obtained from coal tar.

Bitumen

• Bitumen is a substance that is used for road construction.
• It is a petroleum product, which means it is derived from crude oil.
• Bitumen is used instead of coal tar for making roads.
• It is a sticky, black, and thick liquid that becomes solid and hardens when cooled.
• Bitumen is mixed with aggregates like crushed rocks and sand to create asphalt, which is used for metalling the roads.

Coal Gas

• Coal gas is formed as a byproduct during the process of making coke from coal.
• It is a flammable gas that can be burned to release heat energy.
• In the past, coal gas was commonly used for street lighting because it produced a bright flame when burned.
• However, with advancements in technology and the availability of other sources of lighting, coal gas is now mainly used as a fuel for heating purposes.
• Using coal gas as a source of heat is one way to make use of the energy stored in coal and reduce waste.

Petroleum

• Petroleum is a natural resource that is used to make fuels like petrol and diesel.
• Petrol is used as a fuel in light automobiles such as motorcycles, scooters, and cars.
• Diesel is used as a fuel in heavy vehicles like trucks and tractors.
• Petroleum is derived from the word “petra” meaning rock and “oleum” meaning oil, as it is mined from between rocks under the Earth’s surface.
• Petroleum was formed from organisms that lived in the sea. When these organisms died, their bodies settled at the bottom of the sea and were covered with layers of sand and clay.
• Over millions of years, the absence of air, high temperature, and high pressure transformed the dead organisms into petroleum and natural gas.
• Petroleum and natural gas deposits are found above the layer of water because oil and gas are lighter than water and do not mix with it.
• The first oil well in the world was drilled in Pennsylvania, USA, in 1859. In India, oil was discovered in places like Assam, Gujarat, Mumbai High, and the river basins of Godavari and Krishna.

Refining of Petroleum

• Petroleum is a dark, oily liquid with an unpleasant odor.
• It is a mixture of different substances such as petroleum gas, petrol, diesel, lubricating oil, and paraffin wax.
• The process of separating these different substances from petroleum is called refining.
• Refining is carried out in a special facility called a petroleum refinery.

Natural Gas

• Natural gas is an important fossil fuel that is easy to transport through pipes.
• It can be stored under high pressure as compressed natural gas (CNG).
• CNG is used for power generation and as a fuel for transport vehicles because it is less polluting and cleaner than other fuels.
• The advantage of CNG is that it can be directly used for burning in homes and factories through a network of pipelines.
• Some places like Vadodara (Gujarat), parts of Delhi, and other locations have such pipeline networks for supplying natural gas.
• Natural gas is also used as a starting material in the production of chemicals and fertilizers.
• India has vast reserves of natural gas, and it has been found in places like Tripura, Rajasthan, Maharashtra, and the Krishna Godavari delta.

Balance Use Of Natural Resources

• Some natural resources are limited or exhaustible, such as fossil fuels, forests, and minerals.
• Fossil fuels like coal and petroleum are examples of exhaustible resources.
• It took millions of years for dead organisms to turn into coal and petroleum.
• The known reserves of fossil fuels will only last a few hundred years.
• Burning fossil fuels causes air pollution and is linked to global warming.
• It is important to use fossil fuels only when necessary to protect the environment.
• The Petroleum Conservation Research Association (PCRA) in India provides tips to save petrol/diesel while driving.
• PCRA’s tips include driving at a constant and moderate speed, switching off the engine at traffic lights or when waiting, maintaining correct tire pressure, and regularly maintaining the vehicle.