A rise in temperature also lowers the activation energy. The molecules in the reactants must be orientated in such a manner that old bonds are broken so new bonds in the product can form. After all, anybody can plug in numbers and use a calculator. A catalyst is a substance that speeds up chemical reaction without being consumed in the process. A prime example is the enzymes in the human body.
Chemists use catalysts to speed up slow reactions.
An example of this is the production of ammonia, know as the Haber Process. Since the reaction is very slow on its own, chemists add a catalyst to speed it up. Heterogeneous -the catalyst enters and exists in different phases of the reaction. The catalyst usually provided the area where gaseous molecules can adsorb on its surface, then it forms the product. The term adsorption is usually related with heterogeneous catalysts.