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What are Fossil Fuels?

  • Difficulty Level : Easy
  • Last Updated : 21 Jul, 2021
Geek Week

The existence of living beings is known to exist for millions of years now. We know that resources like coal and petroleum take billions of years to be formed due to natural processes. Coal and petroleum are further extracted by human effort to be used for the personal usage of mankind. In this article, we will be learning about Coal and Petroleum. But before that, we should be familiar with the basic terms like:

Natural Resources refer to those resources which are derived from Nature. Natural Resources are further classified as:

  1. Inexhaustible Natural Resources – Inexhaustible natural resources refer to those resources that are abundant in nature and will not be exhausted even after extensive use.  e.g. sunlight, air, etc.
  2. Exhaustible Natural Resources – Exhaustible natural resources refer to those resources that are not present in unlimited quantity in nature and would be exhausted if used extensively. e.g Forests, coal, and petroleum, etc. Exhaustible Resources can be further classified as:-
  • Renewable Resources: The resources which cannot be exhausted even after continuous utilization are termed that renewable resources. Examples of renewable resources are the sun, wind, and tidal energy.
  • Non – Renewable Resources: The resources that cannot be immediately replaced once depleted are called Non-renewable resources. Examples of Non-renewable resources include fossil fuels, such as coal, petroleum and natural gas and rare minerals typically found in meteorites.

Fossil Fuels 

Fossil Fuels are nothing but different types of exhaustible natural resources which are together known as fossil fuels. Coal, petroleum, and other non-renewable natural resources are actually made from the dead remains of living organisms after millions of years due to a natural process. They are found in the earth’s crust. The different types of fossil fuels are as follows:

(1) Natural Fuels: Simply refers to those fuels which are naturally found in nature and can be used as it is without making any changes to it.  For e.g Wood, Crude oil, and Natural Gas. Let’s discuss Natural Gas in detail.

Natural Gas is 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 consists mainly of methane (about 85%), ethane (about 10%) propane (about 3%), and butane.

 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 several chemicals and fertilizers. India has vast reserves of natural gas. In our country, natural gas has been found in Tripura, Rajasthan, Maharashtra, and the Krishna Godavari delta. 

(2) Derived Fuels: These are the one which are extracted or made up by human effort with the help of Natural fuels. e.g Coke, Kerosene, and Coal gas. But, we will discuss coal and petroleum in detail.

  • Coal: Over 295 million years ago, there were dense forests and trees all over the World. But, due to natural disaster like flood , tsunami some of these trees got buried into the earth. As a result of decomposition over time, they were converted to coal. Coal is rigid like stone substance that is full black due to the high pressure and temperature. Since ancient times, coal has been used as a heat source to cook food, to create steam to run trains, for industrial use, generating electricity etc.

Important Byproducts of Coal are:

  1. Coke- It contains 98 % carbon. It is porous, tough, black and the purest form of coal. Like charcoal, it Is a good fuel and burns without smoke. It is largely employed as a reducing agent in the extraction of metals from their ores. It is also used in making fuel gases like water gas and producer gas.
  2. Coal Tar- Coal tar is a mixture of different carbon compounds. It thick, black liquid with an unpleasant smell. The fractional distillation of coal tar gives many chemical substances which are used in the preparation of dyes, explosives, paints, synthetics fibers, drugs, and pesticides. Some of these chemical substances are benzene, toluene, phenol, and aniline. Naphthalene balls used to repel moths and other insects are also obtained from coal tar.
  3. Coal gas- Coal gas is mainly a mixture of hydrogen, methane, and carbon monoxide. The gases present in coal gas are combustible and hence, it is an excellent fuel. It has a high calorific value. It was used for lighting houses, factories, and streets in Mumbai until 1950. It was also used for cooling earlier.
  • Petroleum: It is dark brownish to green-colored viscous liquid fossil fuel. It has a strong foul smell due to the presence of sulfur-containing compounds it. It is commonly called crude oil. The economy of a nation depends to a great extent on petroleum wealth, that’s why petroleum is called black gold. Its name is derived from Latin words Petra (meaning rock) and petroleum (meaning oil). Thus, petroleum literally means “rock oil”.

The Origin of Petroleum

Petroleum is a complex mixture of solid, liquid and hydrocarbons, mixed with saltwater and earthy particles. It is always found trapped between two impervious rocks. It is believed that petroleum is formed by the anaerobic decomposition of tiny sea animals and plants which got buried in the sea bed millions of years ago. Let us see how this happened.

Refining of Petroleum

Petroleum is a mixture of several hydrocarbons. It also contains water, salt, and rocky materials. It cannot be used in this made form either as a fuel or a basic material to produce other useful components. Before being put to use, it has to be purified or refined. The process of separating the various components of petroleum from one another is known as the refining of petroleum. This is done by a process called fractional distillation which is based on the fact that the different components of petroleum have distinctly different boiling points. In fractional distillation, crude petroleum is heated to a temperature of, 40°C or slightly above in a furnace.

Uses of Petroleum 

  1. Petroleum products are used as fuels.
  2. Lubricating oils and vaseline are used as lubricants. 
  3. Paraffin wax, products of petroleum, is used for manufacturing candles, polishes, waxed paper, waterproofing, etc.
  4. Some by-products of petroleum after purification are used in the preparation of medicines, ointments, face creams and cosmetics.

Sample Problems

Problem 1: Define the term ‘Petrochemicals’.


Petrochemicals are substances obtained from petroleum and natural gas. They are used in the manufacture of detergents, fibers, polythene, etc.

Problem 2: You are given a mixture of petroleum and water. How will you separate the two?


Allow standing the mixture of petroleum and water undisturbed for some time. The top layer will consist of petroleum which can be separated from water by decantation.

Problem 3: Differentiate between coke and coal.






 It is an amorphous form of carbon.

It is a noncrystalline form of carbon.


 It is obtained by heating soft coal in the absence or limited supply of air.

It is obtained by the decay of vegetation which existed millions of years ago.

Problem 4: Explain why fossil fuels are exhaustible natural resources. 


Fossil Fuels are nothing but different types of exhaustible natural resources which are together known as fossil fuels. Coal, petroleum, and other non-renewable natural resources are actually made from the dead remains of living organisms after millions of years due to a natural process. The fossil fuels are exhaustible natural resources because it can be exhausted if extensively used after a particular amount of time . And we cannot deny the fact that the formation of fossil fuels takes millions of years to be formed, but it is getting used at a rapid rate.

Problem 5: List the steps to conserve the resources.


As we know, we all are dependent on resources. But we should keep in mind that resources are limited in nature. If we misuse it, our future generation will have no resources. This is an alarming situation. We can take the following steps:

  1. We should cook our food on low flame.
  2. Devices that consume less energy like CFLs and LED lights should be preferred.
  3. We should take care not to waste electricity.
  4. We should cover our cooking vessels while cooking.
  5. Instead of the use of individual vehicles, the use of public transport should be encouraged.
  6. Solar or tidal energy should be developed and encouraged.
  7. Dams should be used to generate electricity instead of burning coal or petroleum.
  8. Public awareness programs should be conducted.

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