Alkenes are double bonds of hydrocarbons therefore they are UNSATURATED.
Alkene is any of the series of unsaturated hydrocarbons containing a double bond, including Methene, Ethene, Propene, Butene.
Functional Group of Alkenes: C=C
Alkenes: More reactive, Turns bromine water colourless, Double bond C=C, unsaturated.
To Test for Alkenes: Alkenes decolourise Bromine water (brown/orange). Alkanes DONT. If you put alkene in bromine it will become clear showing alkene is present.