MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Bromine water is used as a test for alkenes and alkanes. When an alkene is added to bromine water, a halogen, and shaken the double bond in the alkene reacts with the bromine. After being allowed to stand, the layers separate again. The bromine water has been decoloured by the reaction to form water (lower layer). The bromine has added to the alkene to form the corresponding bromoalkane (upper layer). An alkane has been added to bromine water and the test tube shaken. The alkane used here is hexane which, as a hydrocarbon, is immiscible with water. After shaking and being allowed to stand, the two layers separate again, but the bromine is now dissolved in the hexane (top layer) rather than the water (bottom layer). Alkanes do not decolorize bromine.
Model release not required. Property release not required.