Manganese Dioxide and Hydrogen Peroxide (35%) in a PYREX flask. (The foil just makes
it look well more like a "genie in a bottle"). The catalyst (MnO) causes the O2 in the
peroxide to release extremely rapidly as steam (yes, that is steam) and it is quite
spectacular. Think Old Faithful. I would not do this at home for fear of burns.
We are nearing the end of the Chemistry book and talking about energy of chemical
reactions (enthalpy). And the things that might cause reactions to speed up. A catalyst
such as MnO definitely qualifies.