What happens during the reaction of alkenes with hydrogen?

During the reaction of alkenes with hydrogen, known as hydrogenation, the double bond between the carbon atoms in the alkene reacts with hydrogen. This process results in the conversion of the double bond into a single carbon-carbon bond. The result is a saturated hydrocarbon, specifically an alkane.

In this reaction, the alkene gains hydrogen atoms, effectively "saturating" the molecule. This is a key transformation in organic chemistry because it leads to more stable compounds, and it is fundamentally used in various industrial processes, such as the production of margarine from vegetable oils.

The other options do not accurately describe the reaction. Alkenes are indeed reactive with hydrogen (so they do react), and instead of forming a new double bond or getting oxidized, they undergo a reduction process, where the double bond is converted to a single bond. The transformation of the double bond into a single bond is what characterizes this reaction.