GCSE Chemistry · Edexcel 1CH0 · Topic 9B
Hydrocarbons
Key points
- Hydrocarbons contain hydrogen and carbon only.
- Alkanes () are saturated: only single C–C bonds, e.g. methane, ethane, propane, butane.
- Alkenes () are unsaturated: they contain a C=C double bond, e.g. ethene, propene, butene.
- Test: bromine water turns from orange to colourless with an alkene; it stays orange with an alkane.
- Alkenes undergo addition reactions: with bromine to form dibromoalkanes, and with hydrogen (using a catalyst) to form alkanes.
- Both burn in oxygen; complete combustion gives carbon dioxide and water.
- Draw displayed formulae showing every bond.
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Hydrocarbons are compounds of hydrogen and carbon only. The two families at GCSE are the alkanes and the alkenes, and the difference between them, a single C=C double bond, completely changes how they react.
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