Organic Chemistry is a core part of GCSE Chemistry. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
CrackingBreaking long hydrocarbons into shorter useful ones
Thermal crackingHigh temperature and high pressure, no catalyst
Catalytic crackingHot powdered catalyst, lower temperature needed
Intermolecular forceWeak attraction between separate molecules
Homologous seriesFamily with same general formula and reactions
Petrol fractionShort-chain liquid fuel in high demand
ViscosityHow thick or runny a liquid is
Boiling pointTemperature at which a liquid becomes a gas
FlammabilityHow easily a substance catches fire and burns
Structural formulaShows how atoms are joined by lines for bonds
SaturatedAll carbon–carbon bonds are single bonds
Bromine water testOrange bromine water decolourises with alkenes
HydrocarbonCompound of only hydrogen and carbon atoms
AlkaneSaturated hydrocarbon: CnH2n+2, all single bonds
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
How do alkenes typically react with bromine?✗ Bromine substitutes for a hydrogen on the alkene, releasing HBr. ✓ By electrophilic addition — bromine adds across the double bond to form a dibromoalkane.
When water boils, what is broken?✗ The covalent bonds between hydrogen and oxygen atoms are broken when water boils. ✓ Intermolecular forces (hydrogen bonds) between water molecules are broken — the O-H covalent bonds stay intact.
How does a catalyst speed up a reaction?✗ A catalyst lowers the activation energy of the original reaction pathway. ✓ It provides an alternative reaction pathway with a lower activation energy.
Why is cracking carried out in industry?✗ To make crude oil thicker ✓ To turn long alkanes into useful short alkanes and alkenes
Why do long-chain alkanes have higher boiling points?✗ Stronger covalent bonds inside the molecule ✓ Stronger intermolecular forces between molecules
Practise Organic Chemistry — free games
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