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AQA A Level Chemistry

Alkanes as Fuel

Alkanes are widely used as fuels because combustion is exothermic and releases useful energy. These pages separate the fuel topic into combustion chemistry, pollutant formation and catalytic converter treatment so students can connect equations, reaction conditions and environmental consequences.

Exam Paper
Paper 2
7405/2
Specification Points
3.3.2.3
1 point covered
Sub-topics
5 lessons
Revision notes available
Exam Board
AQA
AQA 7405

Revision Notes

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

A clean flame with gas molecules rising
1

Combustion

Revise complete and incomplete combustion of alkanes, including the key products, equations and why combustion releases energy.

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A chimney plume with a sulfur dioxide molecule
2

Oxides of Sulfur

Learn how sulfur impurities in fuels form sulfur dioxide and how sulfur oxides contribute to acid rain and environmental damage.

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An exhaust pipe with a brown haze and a nitrogen oxide molecule
3

Oxides of Nitrogen

Review how high temperatures in engines allow nitrogen and oxygen from air to react, producing nitrogen oxides that cause pollution.

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A cut-away honeycomb catalyst with gases passing through
4

Catalytic Converter

Revise how catalytic converters use transition metal catalysts to convert harmful exhaust gases into less harmful products.

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A scrubber tower spraying through waste gas
5

Flue-Gas Desulfurisation

Removing sulfur dioxide from power-station flue gases with calcium oxide or calcium carbonate, and why the neutralisation works.

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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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Written, drawn and worked exam practice on this topic.

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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

    Revise
  3. ii b

    know that thermal cracking takes place at high temperature

    Revise
  4. ii c

    know that thermal cracking produces a high percentage of alkenes

    Revise
  5. iii a

    know that catalytic cracking takes place at slight pressure

    Revise
  6. iii b

    know that catalytic cracking takes place at high temperature

    Revise
  7. iii c

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

    Revise
  8. iii d

    know that catalytic cracking is used mainly to produce motor fuels

    Revise
  9. iii e

    know that catalytic cracking is used mainly to produce aromatic hydrocarbons

    Revise
  10. iv

    explain the economic reasons for cracking alkanes

    Revise

3.3.2.3

  1. i

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

    Revise
  2. ii a

    know that internal combustion engines produce NOx

    Revise
  3. ii b

    know that internal combustion engines produce CO

    Revise
  4. ii c

    know that internal combustion engines produce carbon

    Revise
  5. ii d

    know that internal combustion engines produce unburned hydrocarbons

    Revise
  6. ii e

    know that catalytic converters remove NOx

    Revise
  7. ii f

    know that catalytic converters remove CO

    Revise
  8. ii g

    know that catalytic converters remove unburned hydrocarbons

    Revise
  9. iii

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

    Revise
  10. iv

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

    Revise

3.3.2.4

  1. i

    describe the reaction of methane with chlorine

    Revise
  2. ii a

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

    Revise
  3. ii b

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

    Revise
  4. ii c

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

    Revise