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AQA A Level Chemistry

3.3.2
Alkanes

AQA 3.3.2 covers alkanes as saturated hydrocarbons: the fractional distillation of crude oil, thermal and catalytic cracking, complete and incomplete combustion, the pollutants from internal combustion engines and their removal, sulfur dioxide from fuels, and the free-radical substitution of methane by chlorine.

Exam Paper
Paper 2
7405/2
Specification Points
3.3.2.1 – 3.3.2.4
4 AQA sections
Sub-topics
4 lessons
16 revision pages
Exam Board
AQA
AQA 7405

Revision Notes

4 revision notes, in the order the specification teaches them.

A fractionating tower with liquids drawn off at different heights
1

Alkanes from Crude Oil

Fractional distillation, cracking and reforming: where alkanes come from and how fractions are processed.

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A clean flame with gas molecules rising
2

Alkanes as Fuel

Complete and incomplete combustion, oxides of sulfur and nitrogen, and catalytic converters.

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A green leaf and grain beside a fuel drop
3

Alternative Fuel

Biofuels, hydrogen and carbon neutrality compared with fossil fuels (extension for this board).

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A radical pulling a hydrogen from a methane molecule
4

Reactions of Alkanes

Free-radical substitution with halogens under UV light: initiation, propagation, termination and further substitution.

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Summary Map

Download, print and revise the reactions of this topic at a glance.

Summary maps

Download, print and revise the reactions of this topic at a glance.

Illustration of a summary map: compounds joined by reaction arrows
Summary map · PDF

Alkanes Map

AQA A-level Chemistry · 3.3.2 Alkanes

Every reaction on one A4 page: reagents, conditions and reaction type for each arrow, colour coded, with the key tests.

Download the map4 reactions · A4 landscape · print ready
Illustration of a summary map: compounds joined by reaction arrows
Summary map · PDF

Alkanes Summary Map

AQA A-level Chemistry · 3.3.2 Alkanes

The whole section on one A4 page: crude oil, thermal and catalytic cracking, combustion, pollutants, converters and flue-gas desulfurisation, with the free radical mechanism in a table.

Download the map6 key ideas + the mechanism · A4 portrait · print ready

© 2026 Online Learning System. For personal study: printing is allowed; editing, copying and redistribution are not.

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Revision Game

Match reagents to products, free, with your board's reagents and conditions.

Illustration of memory game cards, two turned face up as a matching pairFree

Revision Game: Alkanes

Turn the cards over two at a time: match reagents to what they make, and find how each product is made.

A free memory game on the reactions in this topic, with your board's reagents, conditions and spec points.

  • Two ways to playMatch each set of reagents to what the reaction makes, or see a product and find the reactant and reagents that make it.
  • Drawn the way the exam draws themEvery structure is drawn in ChemDraw, with the reagents and conditions your exam board asks for.
  • It countsRounds earn XP and keep your streak going, and every correct match shows in your KASP analytics, apart from your marks.

Study Cards

Pick a deck, then turn each card to check what you remember.

Specification

Every specification point in this topic, in the exam board's own words. Rate how confident you are with each one.

Official AQA documentsSpecification (opens the AQA website in a new tab)Data booklet (opens the AQA website in a new tab)

Self-assessment · 26 points

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3.3.2.1

  1. i

    know that alkanes are saturated hydrocarbons

    Revise
  2. ii

    know that petroleum is a mixture consisting mainly of alkane hydrocarbons that can be separated by fractional distillation

    Revise

3.3.2.2

  1. i

    know that cracking involves breaking C-C bonds in alkanes

    Revise
  2. ii a

    know that thermal cracking takes place at high pressure

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  3. ii b

    know that thermal cracking takes place at high temperature

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  4. ii c

    know that thermal cracking produces a high percentage of alkenes

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  5. iii a

    know that catalytic cracking takes place at slight pressure

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  6. iii b

    know that catalytic cracking takes place at high temperature

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  7. iii c

    know that catalytic cracking takes place in the presence of a zeolite catalyst

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  8. iii d

    know that catalytic cracking is used mainly to produce motor fuels

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  9. iii e

    know that catalytic cracking is used mainly to produce aromatic hydrocarbons

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  10. iv

    explain the economic reasons for cracking alkanes

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3.3.2.3

  1. i

    know that alkanes are used as fuels and that combustion can be complete or incomplete

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  2. ii a

    know that internal combustion engines produce NOx

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  3. ii b

    know that internal combustion engines produce CO

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  4. ii c

    know that internal combustion engines produce carbon

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  5. ii d

    know that internal combustion engines produce unburned hydrocarbons

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  6. ii e

    know that catalytic converters remove NOx

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  7. ii f

    know that catalytic converters remove CO

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  8. ii g

    know that catalytic converters remove unburned hydrocarbons

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  9. iii

    know that combustion of hydrocarbons containing sulfur leads to sulfur dioxide that causes air pollution

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  10. iv

    explain why sulfur dioxide can be removed from flue gases using calcium oxide or calcium carbonate

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3.3.2.4

  1. i

    describe the reaction of methane with chlorine

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  2. ii a

    explain the initiation step in the chlorination of methane as a free-radical substitution mechanism

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  3. ii b

    explain the propagation steps in the chlorination of methane as a free-radical substitution mechanism

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  4. ii c

    explain the termination steps in the chlorination of methane as a free-radical substitution mechanism

    Revise