IGCSE · Practice questions · Fuels and fractional distillation

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Six original Cambridge-style questions on fuels and the fractional distillation of petroleum.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Keep these straight

Gas at the top, bitumen at the base.

Fossil fuels: coal, natural gas (mainly methane), petroleum.
Order: refinery gas, gasoline, naphtha, kerosene, diesel, fuel oil, lubricating oil, bitumen.
Down the column: longer chains, higher b.p., less volatile, more viscous.
Separation: by boiling point; a physical process, no bonds broken.

Recall

[2 marks]

Name the three fossil fuels and state the main constituent of natural gas.

Coal, natural gas and petroleum (crude oil). ✓
Natural gas is mainly methane, CH₄. ✓

Recall

[4 marks]

Give a use for each fraction: (a) refinery gas; (b) diesel oil; (c) fuel oil; (d) bitumen.

(a) bottled gas for heating and cooking. ✓
(b) fuel for diesel engines. ✓
(c) fuel for ships and home heating systems. ✓
(d) making roads. ✓

Explain

[3 marks]

Describe how petroleum is separated into fractions in a fractionating column.

Petroleum is heated and vaporised; the vapour enters the column. ✓
The column is hot at the bottom and cooler at the top; vapours rise and cool. ✓
Each fraction condenses at the level where the temperature is below its boiling point and is drawn off there. ✓

Analysis

[3 marks]

Compare the kerosene and lubricating oil fractions in terms of chain length, volatility and viscosity.

Lubricating oil has longer chains than kerosene. ✓
Lubricating oil is less volatile (higher boiling point). ✓
Lubricating oil is more viscous. ✓

Data

[2 marks]

A fraction has molecules with 5 to 10 carbon atoms and boils between about 40 °C and 180 °C. Identify the fraction and give its use.

Gasoline (petrol). ✓
Fuel for cars. ✓

Explain

[2 marks]

A student says that fractional distillation produces pure compounds. Explain why this is incorrect.

Each fraction is a mixture of hydrocarbons. ✓
The molecules in a fraction have similar chain lengths and a range of boiling points, not a single boiling point. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.