Chapter summary

Organic Chemistry, at a glance

Recognise molecular families and connect structures, reactions, fuels and materials.

O-Level 6092 (2026) / SEC G3 K324 (2027)

Quick revision

Revisit the essentials, then return to an explanation when you need it.

Exam definitions: learn these in mark-scheme words
Term	Definition to write
Hydrocarbon	A compound made of carbon and hydrogen only.
Homologous series	A family of compounds with the same general formula and functional group, similar chemical properties, and a gradual change in physical properties as the molecules get larger. Successive members differ by CH₂.
Saturated hydrocarbon	A hydrocarbon with only single bonds between carbon atoms.
Unsaturated hydrocarbon	A hydrocarbon with at least one carbon-carbon double bond.
Cracking	The breaking down of large hydrocarbon molecules into smaller, more useful molecules, using heat and a catalyst.
Monomer	A small molecule that can join with many others to form a polymer.
Polymer	A very large molecule built up from many small units (monomers).
Addition polymerisation	Many unsaturated monomer molecules join together to form a polymer, with no other product formed.
Polyunsaturated	Describes food molecules (fats and oils) that contain many carbon-carbon double bonds.

Pure and Combined: fermentation
Term	Definition to write
Fermentation	The conversion of glucose into ethanol and carbon dioxide by enzymes in yeast, at about 37 °C, in the absence of oxygen.

Pure only

Pure only: more exam definitions
Term	Definition to write
Isomers	Compounds with the same molecular formula but different structural formulae.
Condensation polymerisation	Monomers join together to form a polymer, with a small molecule such as water lost at each link.

Core reaction connections

Alkane
Combustion; chlorine substitution under UV; larger molecules can crack.
Alkene
Bromine/hydrogen addition and addition polymerisation.
Ethanol
Fermentation makes it; combustion releases energy; oxidation forms ethanoic acid.
Polymer
Match the repeat unit to its monomer; distinguish physical and chemical recycling.

Pure only

Pure: add C4 and branched structures, isomerism, ethene hydration, carboxylic-acid reactions, esters and condensation-polymer hydrolysis. Reagents and essential conditions matter; exact numerical process settings are not required.

Quick recall

Card 1 of 8. Answer in your head, then check.

How is crude oil separated into fractions?

Revisit an explanation

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