This experiment shows the catalyzed decomposition of hydrogen peroxide. Hydrogen peroxide (HO) decomposes into water and oxygen gas, which is in the form of foam, but normally the reaction is too slow to be easily perceived or measured:
In normal conditions, this reaction takes place very slowly, therefore a catalyst is added to speed up the reaction, which will result in rapid formation of foam. The iodide ion from potassium iodide acts as a catalyst and speeds up the reaction while remaining chemically unchanged in the reaction process. The iodide ion changes the mechanism by which the reaction occurs:
The reaction is exothermic; the foam produced is hot (about 75°C or 167°F). A glowing splint can be used to show that the gas produced is oxygen.
The rate of foam formation measured in volume per time unit has a positive correlation with the peroxide concentration (v/V%), which means that more foam will be generated per unit time when a more concentrated peroxide solution is used.