The addition of hydrogen across a double bond is known as hydrogenation. It is a chemical reaction in which hydrogen gas (H2) is added to a molecule that contains a double bond between two carbon atoms (C=C). Hydrogenation typically occurs in the presence of a catalyst, such as a metal such as platinum, palladium, or nickel. During this process, the double bond is converted into a single bond, and two hydrogen atoms are added to the carbon atoms that were previously double-bonded. Hydrogenation is commonly used in various industrial processes, such as the production of saturated fats from unsaturated fats (e.g., converting vegetable oils into margarine), refining petroleum, and hydrogenating organic compounds for various applications.