What defines a catalyst?

A catalyst is defined as a substance that alters the rate of a chemical reaction without undergoing any permanent chemical change itself. This means that while a catalyst can facilitate a reaction, it is not consumed in the process and can participate in multiple reaction cycles. By providing an alternative pathway for the reaction with a lower activation energy, catalysts greatly enhance the reaction rate, making them essential in many industrial processes and biological systems.

In contrast, a catalyst does not increase the energy requirement for a reaction (which would make it less favorable), nor does it require specific temperature conditions to act, as some catalysts can function effectively at a range of temperatures. Additionally, it is key to remember that a catalyst remains unchanged at the end of the reaction, which distinguishes it from reactants that are transformed into products during the reaction.