Catalyst

H2O lc

A catalyst adds some magic to a chemical reaction. Reactions need an amount of energy in order to happen. If they don't have it, the reaction probably cannot happen. A catalyst lowers the amount of energy needed so that a reaction can happen more easily. A catalyst is all about energy. If you fill a room with hydrogen gas (H2) and oxygen gas (O2), very little will happen. When you light a match in that room most of the hydrogen and oxygen will combine to create water molecules (H2O). It is an explosive reaction. You can also add a catalyst to that room and get a reaction started. If you add some palladium (Pd) it will act as the catalyst.