Welcome to myschoollibrary! Today in our Basic Science And Technology lesson, we will be treating the topic ” Crude Oil And Petrochemicals ” Do have a nice time studying with us!


Lesson Note

Subject: Basic Science And Technology

Class: JS2

Topic: Crude Oil And Petrochemicals

Learning Objectives: by the end of the lesson, the students should be able to:

  1. Explain the terms crude oil and petrochemicals;
  2. Describe the process of refining crude oil;
  3. State the uses of crude oil and petrochemicals;
  4. Statevthe importance of crude oil to Nigeria;
  5. Name examples of materials made from petrochemicals.



Crude oil is a dark brown liquid substance found under the ground or sea. It is locked up between rocks several meters under the ground. Crude oil can not come out of the rock on its own and can not be seen from the surface of the earth. That’s why some scientists are trained to search for oil. The search for oil is called oil exploration. Oil companies do employ special scientists called geophysicists who are experts in geology and physics.

During oil exploration, geophysicists make use of special equipment to send signals to the rocks in the depth of the ground or sea to get some signals from the depths. These signals are used by geoscientists to examine the structure of the layers of the rocks which they used to identify the presence of crude oil. The presence of oil is confirmed by drilling with the aid of equipment called drilling rig. Strong pipes joined end to end are driven by the drilling rig down into the ground to reach the oil. As the pipes touch the oil, natural gas comes out first through the pipes. This is the gas used for cooking. Later, the main oil comes up through the pipe. From the pipes, it is sent through other pipes to oil storage tanks. The process of bringing out oil from the underground rocks is called oil production. What comes out from oil drilling is called petroleum or rock.

Oil is found in many countries of the world such as Europe, America, Middle East and Asia. Nigeria is one of the major producers of oil in the world. Oil is found in many parts of Nigeria especially the Niger-Delta areas. I Nigeria, Oil was first discovered in Oloigbiri oil field in Ogbia local government area of Bayelsa State. Oil is the major source of income in Nigeria.



Crude oil can be defined as the liquid form of unrefined petroleum. It is a dark brown or greenish flammable liquid. It consists of a complex mixture of various hydrocarbons that differ in appearance, composition and purity. Crude oil also contains small particles of minerals such as sulphur and metals. Other forms of petroleum are natural gas which is stored in cylinders and used for cooking and bitumen used for tarrying roads.


Petrochemicals are chemical compounds which are derived from the refining of petroleum. For example, methane is a refinery product which is used to produce carbon black and gas. Other examples are ethane and propene, plastics such as polythene, synthetic fibres (nylon), rubber, etc; detergent; chemicals used for manufacturing of paints, medicine, insecticides, selective weed killers.


We discussed earlier that crude oil produced from underground rocks is piped straight into oil storage tanks. From the storage tanks, crude oil is transported into its components. Since crude oil is a mixture, a physical method of separation is used. This method is called fractional distillation.

The fundamental process in the refinery that separates crude oil into its components is the fractional distillation. Reason being that crude oil components have different boiling points. The refining process therefore involves fractional distillation of crude oil fractions, purification and conversion of the fractions into more useful products.


  • Heating the crude oil in gas furnace at a high temperature of 500 degrees centigrades to 600 degrees centigrade by passing it through heating pipes in the gas furnace.
  • The vapour is passed into a tall fractionating tower, the temperature of which varies from 400 Centigrades at the bottom to 40 degree centigrades at the top.
  • Fractions of the crude oil are collected from the different temperature levels in the trays of the tower. Each tray contains several bubble caps through which the vapour with similar boiling temperature pass and condense. The most volatile components are found in the upper part of the tower, while viscous and solid components are collected at the bottom of the tower.


Crude oil is quite different from the petrol and oil used in vehicles. Petrol is just a fraction obtained from crude oil. The following are fractions from crude oil:

Petroleum gas or refined gas. This fraction is obtained at the uppermost part of the tower. It is the product with the least boiling point.


a. It is sold as cooking gas

b. It serves as source of other chemicals.
2. Petrol or gasoline: This product is the second with relatively high temperature range and a number of carbon constituent than the refinery gas.

USES: It is a major source of fuel for internal combustion engine.
3. Naphtha: This product has a higher number of carbon atams per molecules than petrol and is usually further refined to get petrol.

a. It is used as chemical feed stock.

b. It is refined to give more gasoline.

4. Kerosene or paraffin oil: This product has higher viscosity than both gasoline and naphtha. It also contains higher number of carbon than gasoline and naphtha.


a. It is used as heating and lighting oil.

b. It can also be used to produce gasoline.
5. Heavy gas oil: This is usually coloured and more viscous than light gas.


a. It s used as fuel for slow speed engines such as diesel engine.

b. Can be used to produce gasoline.
6. Light gas: This include diesel oil or gas oil. It is a viscous product.


a. Used as heating oil.

b. It is used in high speed diesel engine.
7. Lubricating oil, fuel oil and bitumen: These are thick and nonvolatile products. They are referred to as residues.


a. It serves as lubricant.

b. It is used in the production of candles and waxes.

c. It is useful in road surfacing.

d. It is also used for roofing.


Petrochemicals are used as raw materials for industrial production of essential materials such as:

  1. Raw materials for the production of polymers (plastics); paints; synthetic rubber and textiles.
  2. Fertilizers
  3. Pesticides
  4. Good additives
  5. Detergents
  6. Cosmetics.


  • They are sources of revenue
  • Sources of energy
  • Products and sources of industrial raw materials, thus making most industries functional.


Done studying? Use the questions below to test your learning progress!

1. What do you understand by the terms crude oil and petrochemicals.
2. Describe the process of refining crude oil.
3. State the uses of crude oil and petrochemicals.

4. State the importance of crude oil and petrochemicals to your country if you are from oil producing country.
5. State the importance of crude oil to Nigeria.
6. Name examples of materials made from petrochemicals.
Were you able to answer those questions? Bravo!!

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