Marshmallow Experiment

The demonstration of the experiment can be seen in the following link :
http://www.youtube.com/watch?v=hqQZ7QLqIVU

The reaction in this experiment is the decomposition of hydrogen peroxide (H2O­2) to give oxygen gas.
2H2O­2(aq) → 2H2O(l) + O2(g)

Potassium iodide (KI) is used as a catalyst to speed up the formation of oxygen gas. (MnO2 can also be used as catalyst, but the black colour of MnO2 will make the foam looks worse.)

To make the reaction more visible and visual, some liquid soap (or liquid detergent) is added before adding the KI catalyst. The oxygen bubbles rapidly formed in the presence of some liquid soap (or liquid detergent) will cause a dramatic effect of foaming.