Testing for Alkenes: The Bromine Water Test
Part of Cracking (HT) — GCSE Chemistry
This deep dive covers Testing for Alkenes: The Bromine Water Test within Cracking (HT) for GCSE Chemistry. Revise Cracking (HT) in Organic Chemistry for GCSE Chemistry with 24 exam-style questions and 0 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 7 of 14 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 7 of 14
Practice
24 questions
Recall
0 flashcards
🧪 Testing for Alkenes: The Bromine Water Test
Since cracking produces alkenes, we need to identify them. The bromine water test is the classic method:
• Reagent: Bromine water (orange/yellow solution)
• Test: Add the hydrocarbon to bromine water and shake
• Positive result (alkene): Orange bromine water turns colourless
• Negative result (alkane): Orange colour remains — no reaction
Br₂ + C₂H₄ → C₂H₄Br₂
bromine + ethene → dibromoethane
• The C=C double bond reacts with bromine in an addition reaction
• Bromine adds across the double bond, removing it from solution
Safety Note: Bromine water is toxic and should be handled with care. Always use in a well-ventilated area and wear eye protection.