Recall the colour change when bromine water reacts with an alkene.

In the subtopic Cracking and alkenes, this learning objective focuses on recall the colour change when bromine water reacts with an alkene. It sits within Carbon compounds as fuels and feedstock for AQA GCSE Chemistry 8462 Unit 4.7 Organic chemistry, so the explanation must stay anchored to organic chemistry rather than becoming a generic carbon-compounds fact. Approved keywords to use include alkene, bromine water. Alkene. means a hydrocarbon that contains at least one carbon-carbon double bond Avoid the mistake of students often think that bromine water turns clear when it reacts with an alkene; instead, students should remember that bromine water actually changes from brown to colourless when it reacts with an alkene For exam answers, when an alkene reacts with bromine water, the orange–brown colour disappears within seconds, giving a clear or pale yellow solution Keep molecular formula, structural formula, displayed formula, and general formula distinct. Do not confuse alkanes with alkenes, saturated with unsaturated, cracking with combustion, polymers with monomers, or hydrocarbons with oxygen-containing alcohols and carboxylic acids. When formulae are used, preserve the stored notation exactly and explain the GCSE chemistry idea in words rather than using unsupported displayed-formula diagrams.