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Edexcel International A Level Chemistry

Reactions of Alkanes

Alkanes are relatively unreactive because they contain strong non-polar C–C and C–H bonds. Their key reaction in Topic 4 is free radical substitution, where ultraviolet light generates radicals that replace hydrogen atoms with halogen atoms.

Exam Unit
Unit 1
WCH11/01 – IAS
Specification Points
4.17 – 4.18
2 points covered
Sub-topics
5 lessons
Revision notes available
Exam Board
Edexcel IAL
Pearson International

Revision Notes

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

A radical pulling a hydrogen from a methane molecule
1

Free Radical Substitution

Revise the overall reaction between alkanes and halogens, including substitution, UV light and halogenoalkane formation.

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Light splitting a halogen molecule into two radicals
2

Initiation

Learn how ultraviolet light breaks the halogen-halogen bond by homolytic fission to produce reactive halogen radicals.

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A radical used and regenerated in a cycle
3

Propagation

Review the two propagation steps where radicals react with alkane molecules and regenerate new radicals to continue the chain.

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Two radicals joining to end the chain
4

Termination

Revise how two radicals combine to form a stable molecule, removing radicals and stopping the chain reaction.

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More and more hydrogen atoms replaced by halogen
5

Further Substitution

Learn why more than one hydrogen atom can be replaced, leading to mixtures of halogenated organic products.

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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

Edexcel International A Level Chemistry · Unit 1 · Topic 4

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

Download the map5 reactions · A4 portrait · print ready
Illustration of a summary map: compounds joined by reaction arrows
Summary map · PDF

Alkanes Summary Map

Edexcel International A Level Chemistry · Unit 1 · Topic 4B Alkanes

The whole section on one A4 page: crude oil, cracking, reforming, combustion, pollutants and alternative fuels, 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.

Virtual Lessons

Recorded video lessons that teach the topic step by step.

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Virtual Lessons

Taught step by step in 4 recorded video lessons, to watch at your own pace.

Topic 4B Alkanes taught by a specialist chemistry teacher, in 4 recorded video lessons that follow the specification.

  • Learn it before you revise itEach lesson explains the chemistry step by step, with the diagrams, mechanisms and worked examples the exam expects.
  • At your own pacePause, rewind and rewatch any part. Each lesson opens where you stopped.
  • Your progress is keptA lesson is ticked off once you have watched most of it, here and in your course on Moodle.

MCQ Bank

Multiple-choice papers on this topic, marked the moment you submit. MCQ (A) is free.

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Test yourself: 5 MCQ papers

Exam-style multiple-choice papers, marked the moment you submit with every answer explained. MCQ (A) is free.

5 exam-style multiple-choice papers, MCQ (A) to (E): 110 questions on Topic 4B Alkanes, written the way the exam asks them.

  • Marked the moment you submitYour score straight away, with every answer explained, right or wrong.
  • Revise what you missedEach explanation links to the revision notes for that point.
  • MCQ (A) is freeTry the first paper now. MCQ (B) to (E) come with the course.
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SAQ Bank

Written, drawn and worked exam practice on this topic, marked by a specialist chemistry teacher.

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Written and drawn answers: 10 papers

Draw, write and calculate the way the exam asks, then a specialist chemistry teacher marks your work.

10 exam papers, (A) to (J): 135 questions on Topic 4B Alkanes with no multiple choice. You write explanations, work out calculations and draw answers: structures, mechanisms and diagrams.

  • Answer the way the exam asksThe real paper wants written, worked and drawn answers, so that is how you practise.
  • Marked by a teacher, assisted by KASPA specialist chemistry teacher marks every answer against the mark scheme, with feedback on what to fix.
  • One paper marked each weekYour marked paper comes back here with every marking point shown.
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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.

Self-assessment · 40 points

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4.9

  1. a

    know the general formula of alkanes

    Revise
  2. b

    know the general formula of cycloalkanes

  3. c

    understand that alkanes are hydrocarbons

    Revise
  4. d

    understand that cycloalkanes are hydrocarbons

  5. e

    understand that alkanes are saturated

    Revise
  6. f

    understand that cycloalkanes are saturated

    Revise

4.10

  1. a

    understand the term 'structural isomerism'

    Revise
  2. b

    be able to draw structural isomers of organic molecules given their molecular formula

    Revise

4.11

  1. a

    be able to draw structural isomers of alkanes with up to six carbon atoms

    Revise
  2. b

    be able to name structural isomers of alkanes with up to six carbon atoms

    Revise
  3. c

    be able to draw structural isomers of cycloalkanes with up to six carbon atoms

  4. d

    be able to name structural isomers of cycloalkanes with up to six carbon atoms

4.12

  1. a

    know that alkanes are used as fuels

    Revise
  2. b

    know that alkanes are obtained from fractional distillation of crude oil

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  3. c

    know that alkanes are obtained from cracking of crude oil fractions

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  4. d

    know that alkanes are obtained from reforming of crude oil fractions

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  5. e

    be able to write equations for fractional distillation/cracking/reforming reactions where relevant

    Revise

4.13

  1. a

    know that carbon monoxide is emitted during combustion of alkane fuels

    Revise
  2. b

    know that oxides of nitrogen is emitted during combustion of alkane fuels

    Revise
  3. c

    know that oxides of sulfur is emitted during combustion of alkane fuels

    Revise
  4. d

    know that carbon particulates is emitted during combustion of alkane fuels

    Revise
  5. e

    know that unburned hydrocarbons is emitted during combustion of alkane fuels

    Revise

4.14

  1. a

    understand the toxicity problem arising from carbon monoxide produced during combustion of alkane fuels

    Revise
  2. b

    understand why carbon monoxide is toxic

    Revise
  3. c

    understand the acidity problem arising from oxides of nitrogen produced during combustion of alkane fuels

    Revise
  4. d

    understand the acidity problem arising from oxides of sulfur produced during combustion of alkane fuels

    Revise

4.15

  1. a

    be able to discuss reasons for developing alternative fuels in terms of sustainability

    Revise
  2. b

    be able to discuss reasons for developing alternative fuels in terms of reducing emissions

    Revise
  3. c

    be able to discuss reasons for developing alternative fuels in terms of CO2 emissions and climate change

    Revise

4.16

  1. a

    be able to apply the concept of carbon neutrality to petrol

    Revise
  2. b

    be able to apply the concept of carbon neutrality to bioethanol

    Revise
  3. c

    be able to apply the concept of carbon neutrality to hydrogen

4.17

  1. i

    understand the reactions of alkanes with: oxygen in the air (combustion)

    Revise
  2. ii

    understand the reactions of alkanes with: halogens

    Revise

4.18

  1. i

    understand the mechanism of the free radical substitution reaction between an alkane and a halogen: using free radicals, which are species with an unpaired electron, represented by a single dot

    Revise
  2. ii

    understand the mechanism of the free radical substitution reaction between an alkane and a halogen: showing the initiation step of the mechanism, with curly half-arrows for free radical formation

    Revise
  3. iii

    understand the mechanism of the free radical substitution reaction between an alkane and a halogen: showing the propagation and termination steps of the mechanism

    Revise
  4. iii a

    understand the propagation steps of the free radical substitution reaction between an alkane and a halogen

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  5. iii b

    understand the termination steps of the free radical substitution reaction between an alkane and a halogen

    Revise
  6. iv

    understand the mechanism of the free radical substitution reaction between an alkane and a halogen: having limited use in synthesis because of further substitution reactions

    Revise