NCERT Class 8 Science — Chapter 1: Coal and petroleum

mcqeasy

In the context of petroleum fractionation, what is the primary function of the lubricating oil fraction?

Official previous-year question

Verified 1 Aug 2026.

Options

ASurfacing of roads
BManufacturing of ointments
CReducing friction in engines and machinery
DUse as a domestic fuel

Did you get this right?

Solution

The correct option is

Reducing friction in engines and machinery

Explanation

Petroleum (crude oil) is a complex mixture of hydrocarbons. It is processed through fractional distillation to separate it into various useful fractions based on their boiling points. Each fraction serves a distinct industrial or domestic purpose.

Analysis of Petroleum Fractions:

Lubricating Oil: This is a heavy fraction obtained at higher temperatures. Due to its viscous nature, its primary function is to reduce friction and wear between moving parts in engines and industrial machinery.
Bitumen: The residual fraction left after distillation is used for the surfacing of roads and in paints.
Kerosene and LPG: These lighter fractions are primarily used as domestic fuels.
Petroleum Jelly: A semi-solid fraction used in the manufacturing of ointments and cosmetics.

Key Takeaway:
In petroleum fractionation, lighter fractions (LPG, Petrol) are used as fuels, while heavier fractions are used for lubrication (Lubricating Oil) and infrastructure (Bitumen).

Your note

More from Chapter 1: Coal and petroleum

Which of the following is NOT a constituent of petroleum?

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Consider the following statements about Coal Gas: 1. It was used for street lighting for the first time in London in 1950. 2. Nowadays, it is primarily used as a source of heat rather than light. 3. It is used as a fuel in industries situated near coal processing plants. Which of the statements given above is/are correct?

medium

With reference to the constituents of petroleum, consider the following statements: 1. Kerosene is primarily used as a fuel for heavy motor vehicles. 2. Lubricating oil is used for lubrication. 3. Paraffin wax is used in ointments and candles. Which of the statements given above is/are correct?

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Consider the following statements regarding the formation of petroleum: 1. It is formed from the remains of vegetation on land. 2. It is formed from organisms living in the sea. Which of the statements given above is/are correct?

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What is the primary reason petroleum is often referred to as ‘black gold’?

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The correct option is

Reducing friction in engines and machinery

Explanation

Analysis of Petroleum Fractions:

Lubricating Oil: This is a heavy fraction obtained at higher temperatures. Due to its viscous nature, its primary function is to reduce friction and wear between moving parts in engines and industrial machinery.
Bitumen: The residual fraction left after distillation is used for the surfacing of roads and in paints.
Kerosene and LPG: These lighter fractions are primarily used as domestic fuels.
Petroleum Jelly: A semi-solid fraction used in the manufacturing of ointments and cosmetics.

Key Takeaway:
In petroleum fractionation, lighter fractions (LPG, Petrol) are used as fuels, while heavier fractions are used for lubrication (Lubricating Oil) and infrastructure (Bitumen).