Elephant Toothpaste (Demonstration)
(Reference: Stone, C.H. J. Chem. Ed. 1944, 21, 300. Lorri Reilly, Michigan Technological University, Houghton, MI.)

Catalyst  :  Exothermic

Illustrate the idea of catalysts and reactions that give off heat

Wear chemical-resistant apron, gloves and safety goggles.
Hydrogen peroxide is very corrosive to skin and respiratory tract.
Do not heat these solutions, or stand over the reaction.

2L graduated cylinder
80 mL 30% hydrogen peroxide
Large squirt of dish-soap (10 mL)
20 mL 2.0 M KI or NaI solutions
Trash-bag, large tub

Place graduated cylinder in large tub lined with a trash-bag.  Place dish-soap and hydrogen peroxide solutions into graduated cylinder.  Explain that the hydrogen peroxide is decomposing, but at a very slow rate.  Then add iodide solution and step back!

The iodide is a catalyst because it speeds up the reaction of the hydrogen peroxide decomposing.  This is an exothermic reaction, and the energy released is in the form of heat.  You will notice steam rising from the cylinder, as well, it is warm to the touch.

When reaction is complete and vessel is cool, pour suds into sink and rinse everything thoroughly.  You want to remove all traces of the hydrogen peroxide.  You can reuse the trash-bag if it has been carefully rinsed.  All other solutions may go down the drain if you used the amounts given above.  If you use less of the iodide solution all of the hydrogen peroxide may not have decomposed.

Ginger Chateauneuf, 2000.