GlossariesGCSE GlossariesGCSE Chemistry GlossaryBromine Water

Bromine Water - GCSE Chemistry Definition

Reviewed by: Philippa Platt

Published

Bromine water is a mixture of bromine and water, forming a reddish-brown liquid commonly used as a reactive test for unsaturation in GCSE Chemistry. It is used to identify the presence of carbon-carbon double bonds in alkenes.

When bromine water is added to an alkene, the solution changes from its characteristic orange-brown to colourless, due to a chemical reaction where bromine atoms add across the double bond.

For example, when ethene reacts with bromine in an addition reaction, 1,2-dibromoethane is formed:

CH2CH2 + Br2 → CH2BrCH2Br

This reaction does not occur with alkanes, as they do not have double bonds for the bromine to react with, making bromine water a useful reagent to distinguish between saturated and unsaturated hydrocarbons.

Examiner-written GCSE Chemistry revision resources that improve your grades 2x

  • Written by expert teachers and examiners
  • Aligned to exam specifications
  • Everything you need to know, and nothing you don’t
GCSE Chemistry revision resources

Share this article

Philippa Platt

Reviewer: Philippa Platt

Expertise: Chemistry Content Creator

Philippa has worked as a GCSE and A level chemistry teacher and tutor for over thirteen years. She studied chemistry and sport science at Loughborough University graduating in 2007 having also completed her PGCE in science. Throughout her time as a teacher she was incharge of a boarding house for five years and coached many teams in a variety of sports. When not producing resources with the chemistry team, Philippa enjoys being active outside with her young family and is a very keen gardener

The examiner written revision resources that improve your grades 2x.

Join now