CBSE Chapter 3 Coal And Petroleum Natural Resources
The various resources which are obtained from nature are called natural resources, for example, air, water, soil, plants, petroleum, etc. These are necessary for the survival of all living beings. Based on their availability in nature, natural resources can be classified into the following two types
1. Inexhaustible Natural Resources
Those natural resources which are present in unlimited quantity in nature and are not likely to be exhausted (used up) by human activities are called inexhaustible natural resources, Example; sunlight, air, water, etc.
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2. Exhaustible Natural Resources
Those natural resources which are present in a limited quantity in nature and can be exhausted (used up) by human activities are called exhaustible natural resources, for example, coal, petroleum, natural gas, minerals, forests, wildlife, etc. Coal, petroleum and natural gas are collectively known as fossil fuels. As they were formed from the remains of dead organisms (fossils).
” Cbse Class 8 Science Chapter 3 Notes “
Class 8 Science Chapter 3 Coal And Petroleum Revision Notes Coal
It is a hard, black combustible fuel. Coal is found in deep coal mines under the surface of the Earth. It burns in the presence of air and produces CO2, gas and heat. Earlier, it was used in railway engines to produce steam to run the engines.
Formation Of Coal
About 300 million years ago, the Earth had dense forests in low-lying wetland areas. Natural processes like flooding, earthquakes, volcanoes, etc., buried these forests under the surface of the Earth.
As more soil deposited over them, they were compressed. The temperature also rose as they sank deeper and deeper. Under high pressure and temperature dead plants got slowly converted into coal.
This slow process of conversion of dead vegetation buried deep under the Earth into coal is called carbonisation.
” Coal And Petroleum Class 8 “
Coal As A Source Of Energy
Coal contains mainly carbon, and when heated in air, it burns and produces mainly carbon dioxide gas and heat. The reaction can be written as
Carbon Oxygen Carbon dioxide Heat
(Coal) (From air)
Uses of Coal
Some of the uses of coal are given below
- Coal is one of the fuels used to cook food.
- It is used in thermal power plants to produce electricity.
- It is used as a fuel in various industries.
- It is used for the manufacture of coke, coal tar and coal gas.
- Products Obtained from Coal
- Coal is processed in the industry to get some useful products. Which are coke, coal tar and coal gas.
” Natural Resources Class 8 “
1. Coke
It is a tough, porous and black substance. Coke is an almost pure form of carbon. When coal is heated in the absence of air, then coal gas and coal tar are eliminated and ok is left behind as a black residue.
Uses of Coke
- Coke is mainly used
- In the extraction of metals such as iron, zinc, etc.
- In the manufacture of steel.
- As a fuel
2. Coal Tar
It is a thick, black liquid having an unpleasant smell. It is a mixture ofabout 200 different carbon compounds.
Uses of Coal Tar
Some of the uses of coal tar are as follows
- The various compounds obtained from coal tar are used as starting materials for manufacturing substances used in everyday life and in industries. For example, perfumes, photographic materials, roofing materials, drugs, explosives, plastics and paints etc.
- Naphthalene balls are obtained from coal tar and are used to repel moths and other insects.
- Coal tar has been used for metalling the roads. But, these days bitumen (a petroleum product) is being used for metalling the roads.
” Exhaustible And Inexhaustible Resources “
3. Coal Gas
It is a gaseous fuel which is obtained during the processing of coal in the absence of oxygen to get coke. It is mainly a mixture of methane and hydrogen with some carbon monoxide.
Uses of Coal Gas
- Some of the uses of coal gas are as follows
- It is used as a fuel in many industries situated near the coal processing plants.
- It has also been used for lighting purposes.
- Science Insight Coal gas was used for street lighting for the first time in London in 1810 and in New York around 1820. This is because when it burns, it produces a good amount of light. Nowadays, it is used as a source of heat rather than light.
CBSE Class 8 Science Chapter 3 Coal And Petroleum Notes For Competitive Exams Petroleum
It is a dark coloured, thick crude (raw) oil having an unpleasant odour. The name petroleum means ‘rock oil (petra = rock, oleum = oil). It is found deep below the Earth’s crust, trapped in rocks in certain areas.
Petrol and diesel are obtained from petroleum. Petrol is used as a fuel in light automobiles, for example, motorcycles, scooters and cars, whereas diesel is used in heavy motor vehicles, for example, trucks and tractors.
” Fossil Fuels Class 8 “
Formation of Petroleum
Petroleum was formed by the decomposition of the remains of plants and animals buried under the sea millions of years ago.
The plants and animals which lived in the sea. died and their bodies settled at the bottom of the sea. The lead remains covered with mud, sand and clay. Due to high temperature, high pressure and the absence of air, these were slowly converted into petroleum and natural gas as shown in the figure.
The layer containing petroleum oil and gas is found above the water. It is because oil and gas are lighter than water and do not mix with it.
Petroleum is extracted by drilling holes (oil wells) in the Earth’s crust. In the drilling process, natural gas comes out first with a great pressure and for a time, the crude petroleum oil comes out by itself due to gas pressure.
The world’s first oil well was drilled in Pennsylvania, USA, in 1859. In 1867, oil was struck at Makum in Assam. In India, oil is found in Assam, Gujarat, Mumbai (offshore area) and the river basins of the Godavari and Krishna rivers.
” Formation Of Coal And Petroleum “
Refining of Petroleum
Petroleum is a mixture of petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc.
Before the use of petroleum for specific purposes, it has to be refined (or purified). The process ofseparating the various useful constituents (fractions) of petroleum is known as refining. It is carried out in a petroleum refinery.
Various Constituents of Petroleum and Their Uses
The various constituents of petroleum and their uses are given below in the table.
” Carbonisation Process “
Petrochemicals
The useful chemicals which are obtained from petroleum and natural gas are called petrochemicals. They are very important as these are used to manufacture a wide range of useful materials such as detergents, fibres (polyester, nylon, acrylic, etc), plastics (polythene, etc). Hydrogen gas obtained from natural gas is used in the production of fertilisers such as urea. Thus, due to its great commercial importance, petroleum is also called ‘black gold’.
Natural Gas
It mainly consists of methane (95%). Other constituents are ethane and propane. It occurs deep under the Earth’s crust either alone or along with oil above the petroleum.
In India, natural gas has been found in Tripura, Rajasthan, Maharashtra and in the Krishna Godavari delta.
It is a very important fossil fuel as it is easy to transport through pipes. When it is compressed by applying pressure, it is called Compressed Natural Gas (CNG).
This gas is used for power generation. It is now being used as a fuel for transport vehicles as it is a clean fuel.
Natural gas is used as a starting material to manufacture many chemicals (petrochemicals) and fertilisers.
” Byproducts Of Coal Processing “
CBSE Class 8 Science Chapter 3 Coal And Petroleum Notes For Quick Learning: Conservation Of Natural Resources
Coal, petroleum and natural gas are fossil fuels and will last only a few hundred years. Fossil fuels, forests and minerals, etc., are exhaustible natural resources. If consumed at a rate faster than the rate at which these are formed in nature, they will get exhausted very soon.
Once the present stock of these gets exhausted, no new supplies of these fossil fuels will be available to us shortly. This is because it requires millions of years to convert the dead organisms into these fuels.
Moreover, the burning of these fuels is a major cause of air pollution. Their use is also linked to global warming. So, we should use these fuels only when necessary as
- It will reduce air pollution and thus lead to a better environment.
- It will reduce the risk of global warming.
- It will ensure their availability for a longer period.
- How to Save Petrol or Diesel while Driving?
- Petrol and diesel are the main fuels used for driving vehicles. So, we should make every effort to save these precious fuels.
- In India, the Petroleum Conservation Research Association (PCRA) advises people how to save petrol or diesel while driving their vehicles.
- The various tips to avoid the wastage of these fuels while driving are as follows:
- Drive at a constant and moderate speed as far as possible.
- Switch off the engine of the vehicle at traffic lights or at a place where you have to wait.
- Ensure the correct tyre pressure of the vehicle. Low tyre pressure consumes more fuel.
- Ensure regular maintenance of the vehicle.
” Cbse Class 8 Science Notes “
Coal is A fossil fuel obtained from deep under the Earth’s crust.
Coal gas is obtained during the processing of coal to get coke. It can be used as fuel.
Coke, A tough, porous and black substance, almost pure form of carbon.
Coal, A black, thick liquid obtained by processing coal.
Fossil fuels are Fuels obtained from the decomposition of dead remains of plants and animals, for Example, petrol, coal, etc.
Natural gas is a fossil fuel which mainly contains methane and can be transported through pipes.
” Inexhaustible Natural Resources Examples “
Petroleum is a dark coloured crude oil having an unpleasant odour.
Petroleum refining: Petroleum is separated into different fractions by this process.
Petrochemicals are useful chemicals which are obtained from petroleum and natural gas.