A Catalyst is a substance that increases the reaction rate without being consumed.

• It functions by providing an alternative reaction mechanism with a significantly lower activation energy ($E_a$).
• Lower $E_a$ means a larger fraction of reactant molecules possess sufficient kinetic energy to overcome the potential energy barrier.
• Note: A catalyst increases both forward and backward rates equally, so it does not change the equilibrium position or the equilibrium constant ($K_{eq}$).