Coal and Petroleum

We use various materials for our basic needs. Some of them are found in nature and some have been made by human efforts. Let’s look at few materials used by us in daily life that are natural and man-made.






Fibre glass







Air, Water, Soil and minerals are obtained from nature, they are called Natural Resources.
Can we use all our natural resources forever ?
Can air, water and soil be exhausted by human activities ?
Is water a limitless resource ?
In the light of the availability of various resources in nature, natural resources can be broadly classified into two kinds :
A) Inexhaustible Natural Resources
These resources are present in unlimited quantity in nature and are not likely to be exhausted by human activities.
Examples : Sunlight, Air, Water, Soil, etc.
B) Exhaustible Natural Resources
The amount of these resources in nature is limited. They can be exhausted by human activities.
Examples : Forests, Wildlife, Minerals, Coal, Petroleum, Natural gas, etc.
In this chapter we will learn about some exhaustible natural resources like coal, petroleum and natural gas. These were formed from the dead remains of living organisms (fossils). So, these are all known as Fossil Fuels.
3.2 COAL
You may have seen coal, or heard about it. It is as hard as stone and is black in colour. Coal is one of the fuels used to cook food. Earlier, it was used in railway engines to produce steam to run the engine. It is also used in thermal power plants to produce electricity. Coal is also used as a fuel in various industries.
I) Formation of Coal
Coal is called a fossil fuel because it was formed from the remains of vegetation that grew as long as 400 million years ago. It is often referred to as “buried sunshine,” because the plants which formed coal captured energy from the sun through photosynthesis to create the compounds that make up plant tissues. The most important element in the plant material is carbon, which gives coal most of its energy.
Most of our coal was formed about 300 million years ago, when much of the earth was covered by steamy swamps. As plants and trees died, their remains sank to the bottom of the swampy areas, accumulating layer upon layer and eventually forming a soggy, dense material called peat.
Over long periods of time, the makeup of the earth’s surface changed, and seas and great rivers caused deposits of sand, clay and other mineral matter to accumulate, burying the peat. Sandstone and other sedimentary rocks were formed, and the pressure caused by their weight squeezed water from the peat. Increasingly deeper burial and the heat associated with it gradually changed the material to coal. Scientists estimate that from 3 to 7 feet of compacted plant matter was required to form 1 foot of bituminous coal.
Coal formation is a continuing process (some of our newest coal is a mere 1 million years old). Today, in areas such as the Great Dismal Swamp of North Carolina and Virginia, the Okefenokee Swamp of Georgia, and the Everglades in Florida, plant life decays and subsides, eventually to be covered by silts and sands and other matter. Perhaps millions of years from now, those areas will contain large coal beds.
II) Heating of Coal
When heated in air, coal burns and produces mainly carbon dioxide gas.Coal is processed in industry to get some useful products such as coke, coal tar and coal gas.
A) Coke
It 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.
B) Coal Tar
It is a black, thick liquid with 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, photographic materials, roofing materials, etc. Interestingly, naphthalene balls used to repel moths and other insects are also obtained from coal tar.
Note : These days, bitumen, a petroleum product, is used in place of coal-tar for metalling the roads.
C) Coal Gas
Coal gas is obtained during the processing of coal to get coke. It is used as a fuel in many industries situated near the coal processing plants.Coal gas was used for street lighting for the first time in London in 1810 and in New York around 1820. Now a days, it is used as a source of heat rather than light.
Life in this generation has become fast and busy. If the development in technology is one reason, fast transportation is also one of the reasons. Now a days, travelling from one place to another has become very easy. Have you ever wondered what is the fuel used in automobiles, heavy motors, etc for running? You know that petrol is used as a fuel in light automobiles such as motor cycles/ scooters and cars. Heavy motor vehicles like trucks and tractors run on diesel.
Petrol and diesel are obtained from a natural resource called petroleum.
A) Formation of Petroleum
Formation of Petroleum Petroleum was formed from organisms living in the sea. As these organisms died, their bodies settled at the bottom of the sea and got covered with layers of sand and clay. Over millions of years, absence of air, high temperature and high pressure transformed the dead organisms into petroleum and natural gas. Look at figure given below.

It shows the deposits of petroleum and natural gas. You see that the layer containing petroleum oil and gas is above that of water. Why is it so ? Recall that oil and gas are lighter than water and do not mix with it.
B) Refining of Petroleum
Petroleum is a dark oily liquid. It has an unpleasant odour. It is a mixture of various constituents such as petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc. The process of separating the various constituents/ fractions of petroleum is known as refining. It is carried out in a petroleum refinery.
C) Various constituents of petroleum and their uses

Constituents of petroleum


Petroleum gas in Liquid form (LPG)

Fuel for home and industry


Motor fuel, aviation fuel, solvent for dry cleaning


Fuel for stoves, lamps and for jet air crafts


Fuel for heavy mot or vehicles, electric generators

Lubricating oil


Paraffin wax

Ointments, candles, Vaseline, etc.


Paints, road surfacing

Natural gas is a very important fossil fuel because it is easy to transport through pipes. Natural gas is stored under high pressure as compressed natural gas (CNG). CNG is used for power generation. It is now being used as a fuel for transport vehicles because it is less polluting. It is a cleaner fuel.
The great advantage of CNG is that it can be used directly for burning in homes and factories where it can be supplied through pipes. Such a network of pipelines exists in Vadodara (Gujarat), some parts of Delhi and other places.
Natural gas is also used as a starting material for the manufacture of a number of chemicals and fertilizers. India has vast reserves of natural gas.
In our country, natural gas has been found in Tripura, Rajasthan, Maharashtra and in the Krishna Godavari delta.
A) Some Natural Resources are Limited
You have studied in the beginning of the chapter that some natural resources are exhaustible like fossil fuels, forests, minerals etc. You know that coal and petroleum are fossil fuels.
It required the dead organisms millions of years to get converted into these fuels. On the other hand, the known reserves of these will last atmost a few hundred years.
Moreover, burning of these fuels is a major cause of air pollution. Their use is also linked to global warming. It is therefore necessary that we use these fuels only when absolutely necessary. This will result in better environment, smaller risk of global warming and their availability for a longer period of time.
In India, the Petroleum Conservation Research Association (PCRA) advises people how to save petrol/diesel while driving.
Their tips are :

  • Drive at a constant and moderate speed as far as possible,
  • Switch off the engine at traffic lights or at a place where you have to wait,
  • Ensure correct tyre pressure, and
  • Ensure regular maintenance of the vehicle.

B) Petrochemicals
Many useful substances are obtained from petroleum and natural gas. These are termed as ‘Petrochemicals’. These are used in the manufacture of detergents, fibres (polyester, nylon, acrylic etc.), polythene and other man-made plastics. Hydrogen gas obtained from natural gas, is used in the production of fertilisers (urea). Due to its great commercial importance, petroleum is also called ‘black gold’.

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