Rapid decomposition of Hydrogen Peroxide catalyzed by Potassium Iodide

2 H2O2 → 2 H2O + O2

This is called reaction is often called Elephant’s Toothpaste and is a pretty simple experiment to set up. Be careful though, it’s an exothermic reaction, and concentrated hydrogen peroxide can bleach clothing and cause burns to the skin.  Unlike  the individuals in this .gif, please wear eye protection.