A catalyst changes the way a reaction occurs, thereby lowering its activation energy and speeding up the reaction. All catalysts return to their original condition after a reaction is complete.
Catalysts, substances that speed up chemical reaction rates, may be homogeneous catalysts or heterogeneous ones. All catalysts work by lowering the activation energy for a reaction. This is the minimum quantity of energy that reactants must possess to undergo a specific reaction. Most catalysts do this by providing a simpler, less energy-intensive, means for reactant molecules to break bonds and form temporary ones with the catalyst.