Who this is for: Cambridge IGCSE Chemistry (0620) students who want fuels — petroleum fractions, fractional distillation and cracking — to become reliable marks instead of vague “fossil fuel” answers.
What query it owns: how to understand and revise fuels in Cambridge IGCSE Chemistry.
Why this is safe: this page owns the fuels revision-guide angle, while Tutopiya’s Fuels subtopic page owns the learning resource and the free Fuels quiz owns the practice.

Fuels provide the energy that powers transport, industry and homes. Cambridge IGCSE Chemistry (0620) tests how petroleum is separated by fractional distillation, why cracking is needed, and how natural gas and coal fit into the syllabus. Exam answers must link each fuel to its use and name the process that produces useful fractions. This guide covers the core ideas, past-paper wording and the mistakes that cost marks every series.

Key takeaways

• Petroleum is a mixture of hydrocarbons separated by fractional distillation in a fractionating column.
• Fractions with smaller molecules have lower boiling points and are collected higher in the column.
• Cracking breaks long-chain alkanes into shorter, more useful alkanes and alkenes using heat and a catalyst.
• Natural gas is mainly methane (CH₄); coal is mainly carbon.
• Exam answers must name uses of fractions (e.g. petrol for cars, bitumen for roads).

What are fuels in Cambridge IGCSE Chemistry?

Fuels are substances that release useful energy when burned. The syllabus focuses on fossil fuels — petroleum, natural gas and coal — and the industrial processes that turn crude oil into usable products. You must know how fractional distillation works, why cracking is carried out, and the main uses of key fractions.

Read the full notes on Tutopiya’s Fuels subtopic page before attempting questions.

The core ideas you must master

Fuel / process	Key fact	Typical use
Petroleum (crude oil)	Mixture of hydrocarbons	Raw material for fuels and chemicals
Refinery gases	Smallest molecules, lowest b.p.	Bottled gas (cooking, heating)
Gasoline (petrol)	Short-chain alkanes	Fuel for cars
Kerosene	Medium-chain alkanes	Jet fuel, heating
Diesel oil	Longer chains	Fuel for lorries, trains
Bitumen	Longest chains, highest b.p.	Road surfacing, roofing
Cracking	Long alkane → short alkane + alkene	Makes more petrol; alkenes for plastics
Natural gas	Mainly methane	Heating, cooking
Coal	Mainly carbon	Power stations, steel industry

Fractional distillation — step by step

1. Crude oil is heated in a furnace until most of it vaporises.
2. Vapour enters the fractionating column, which is hot at the bottom and cooler at the top.
3. Fractions condense at different heights according to boiling point.
4. Smaller molecules (lower b.p.) rise higher and are collected near the top.
5. Larger molecules (higher b.p.) condense lower down.

Fuels in past-paper wording: command words that matter

Command word	What the question wants	Typical fuels stem
Describe	Sequence or process	”Describe how petroleum is separated into fractions.”
Explain	Cause and effect	”Explain why cracking is carried out.”
State	Short fact	”State the main component of natural gas.”
Name	Identify a fraction or use	”Name the fraction used as fuel for cars.”
Suggest	Apply to a scenario	”Suggest why demand for petrol exceeds supply from distillation alone.”

Worked exam-style stems (how to answer the wording)

1. “Describe how petroleum is separated into fractions.” Crude oil is vaporised and passed into a fractionating column. Fractions with lower boiling points rise higher and are collected at different levels. Reward: vaporisation + boiling point difference + collection at different heights.
2. “Explain why cracking is needed.” Fractional distillation produces more long-chain fractions than needed and not enough petrol. Cracking converts long alkanes into shorter, more useful alkanes and alkenes. Reward: supply/demand mismatch + shorter chains produced.
3. “State the main component of natural gas.” Methane (CH₄). Reward: correct name or formula.

Test yourself with the Fuels quiz once you have worked through a few examples.

How fuels connect to the rest of Organic Chemistry

Fuels introduce hydrocarbons that feed directly into Alkanes and Alkenes. Cracking produces alkenes used in Polymers. The Cambridge IGCSE Chemistry resource hub links all Organic Chemistry subtopics.

Common mistakes students make

• Confusing fractional distillation with simple distillation (fractional uses a fractionating column).
• Saying smaller molecules have higher boiling points — the reverse is true.
• Describing cracking without mentioning alkenes as a product.
• Omitting uses of named fractions in describe answers.
• Calling natural gas “mainly ethane” — it is mainly methane.

When you need more support

If fractional distillation and cracking sequences keep costing marks, work through the Fuels quiz to find the gap, then get focused help from a Cambridge IGCSE Chemistry tutor.

Frequently asked questions

What is fractional distillation of petroleum? Heating crude oil so it vaporises, then separating fractions in a fractionating column by boiling point.

Why is cracking carried out? To convert surplus long-chain fractions into shorter, more useful alkanes and alkenes such as petrol and ethene.

What is the main component of natural gas? Methane (CH₄).

How do I revise fuels effectively? Learn fraction uses and boiling-point order, practise describe questions on distillation and cracking, then take the Fuels quiz.

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