Hydrogenation of alkenes is a reaction where hydrogen is added to an alkene to change it into an alkane. In this process, the double bond in the alkene is broken, and each of the two carbon atoms involved in the double bond gains one hydrogen atom.
This reaction needs a catalyst, usually metals like nickel, palladium, or platinum, because hydrogen alone does not easily react with alkenes. The reaction also releases heat because it is exothermic.
A common use of this process is in the food industry, where liquid vegetable oils containing alkenes are hydrogenated to form solid fats like margarine.