Use of a catalyst
A catalyst increases the rate of a reaction but it is not used up in the reaction. If a catalyst is present, the reacting particles can collide more successfully with less energy and so the reaction can take place at a lower temperature.
Elephant's toothpaste experiment
The elephant's toothpaste experiment shows how a catalyst can speed up the rate of a reaction.
Hydrogen peroxide breaks down slowly into water and oxygen. Adding a catalyst such as sodium iodide or potassium iodide makes this happen much more quickly, as shown in the video below.
Enzymes
A protein which catalyses or speeds up a chemical reaction. are biological catalysts.
They occur naturally in the body and help with The breakdown of large insoluble food molecules to smaller soluble ones..
They are used in the production of alcohol (zymase) and digestion of food (amylase). Enzymes are specific. This means that they can only catalyse one reaction.