Testing Saturated & Unsaturated Hydrocarbons
Chemistry: Cambridge International GCSE Supplement, topic 11.5.6
Testing Saturated & Unsaturated Hydrocarbons with Bromine
Bromine water is used to test whether a hydrocarbon is saturated or unsaturated, by observing the colour change in an experiment.
Understanding saturated and unsaturated hydrocarbons
- Saturated hydrocarbons have only single bonds between carbon atoms.
- Unsaturated hydrocarbons have one or more double bonds between carbon atoms.
- They are distinguishable by their chemical properties.
- Alkenes are an important group of unsaturated hydrocarbons with at least one double bond.
Bromine water as a test for unsaturation
- Bromine water is a brownish-orange liquid used in organic chemistry.
- It reacts with unsaturated hydrocarbons but not saturated ones.
Procedure for testing hydrocarbons with bromine water
- Add a few drops of bromine water to a sample of the hydrocarbon.
- Shake or stir the mixture gently to mix the liquids.
- Observe the colour change carefully over a few minutes.
- Ensure this test is done safely, as bromine is toxic and corrosive.
Observing results
- If the mixture loses its brown-orange colour and turns colourless, the hydrocarbon is unsaturated.
- This colour change occurs because bromine adds across the double bonds in alkenes.
- If the mixture keeps its original colour, the hydrocarbon is saturated and does not react with bromine water.
Test yourself on Testing Saturated & Unsaturated Hydrocarbons
Which statement correctly defines a saturated hydrocarbon?
Why does bromine water lose its colour?