Final answer:
To test for the presence of an alkene, bromine water is used, which reacts with the alkene to decolorize the solution, indicating the presence of an unsaturated hydrocarbon.
Step-by-step explanation:
The test that can be done for the presence of an alkene is the addition of bromine water, which is a brownish-orange solution of bromine. When added to an alkene, the bromine reacts and the color of the solution fades, indicating the presence of an alkene due to its unsaturation. This disappearance of color is a clear indication that the alkene has undergone a reaction with the bromine to form a bromoalkane, which is typically colorless. If the brownish-orange color persists, it suggests that no reaction has taken place, indicating that the compound being tested is saturated and does not contain alkene functional groups.