3.8 describe the addition reaction of alkenes with bromine, including the decolourising of bromine water as a test for alkenes

3.8 •halogens react with alkenes, forming haloalkenes (addition reactions)

                •the double bond breaks and flips outwards, for the ‘di’ halogen 

      •alkene + bromine water ------> dibromoalkane (colourless)

                •unlike halogenation for alkanes, this is a unsaturation test