Fiducia TogetherOrganic chemistry
Carbon compounds: alkanes, alkenes, alcohols and polymers.
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.
What it is
Organic compounds are based on carbon chains. Alkanes are saturated with single bonds; alkenes have a carbon-carbon double bond and are unsaturated. Homologous series share a general formula and similar properties.
Where it applies
GCSE chemistry, mostly at higher tier, and A Level.
How it works
Crude oil is separated by fractional distillation, exploiting differences in boiling point which follow from chain length. Cracking breaks long chains into shorter, more useful ones and produces alkenes.
Addition polymerisation joins alkene monomers into a polymer, and the resulting plastics do not biodegrade.
How to use it in your work
Bromine water distinguishes alkanes from alkenes — it stays orange with alkanes and decolourises with alkenes. That test is asked for repeatedly.
For fractional distillation, explain by boiling point and chain length, not by 'heaviness'.
Draw polymer repeat units with the bonds extending through the brackets.
Where to get help
Your teacher, your board's specification for the depth required at your tier, and Bitesize for the diagrams.
Revise this with a song
These are ours. We write revision songs because a lot of people remember a tune when they cannot remember a page, and because revising out loud in the kitchen beats staring at a highlighter.
- The Chemistry Song The GCSE chemistry specification, set to music.
Where to read more
Last reviewed 2026-08-28 by Fiducia Together · Next review due 2027-08-28
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.