The substance that speeds up a chemical reaction is called a .

The substance that speeds up a chemical reaction without being consumed in the process is called a catalyst.

Catalysts work by providing an alternative reaction pathway with a lower activation energy ($E_a$), thereby increasing the rate of the reaction. They remain chemically unchanged at the end of the reaction and can be reused. For example, in the Haber process for ammonia synthesis, an iron catalyst speeds up the reaction between nitrogen and hydrogen gases. Similarly, enzymes in biological systems act as catalysts to facilitate biochemical reactions efficiently.

Catalysts are essential in various industrial processes, such as the use of manganese dioxide (MnO₂) in the decomposition of hydrogen peroxide ($2\mathrm{H}{}_2\mathrm{O}{}_2\to 2\mathrm{H}{}_2\mathrm{O}+\mathrm{O}{}_2$) or vanadium(V) oxide (V₂O₅) in the contact process for sulfuric acid production. Their ability to enhance reaction rates without being consumed makes them economically and environmentally valuable.

2H₂O₂+MnO₂heat2H₂O+O₂