Chapter summary
Organic Chemistry, at a glance
Recognise molecular families and connect structures, reactions, fuels and materials.
O-Level 5086 / 5088 (2026) / SEC G3 K326 / K328 (2027)
Quick revision
Revisit the essentials, then return to an explanation when you need it.
| 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. |
| 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. |
- 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.
Quick recall
How is crude oil separated into fractions?