Science Short: Aluminum & Iodine

Here is a very quick and easy to perform demonstration of the highly exothermic reaction between iodine and aluminum. Just simply mixing powders of the two together starts the reaction, but this usually takes a while to build up. You can speed it up significantly with a drop or two of water (glycerin also seems to work). The activation energy is quickly reached and the mixture ignites, producing a beautiful cloud of deep purple iodine vapor. This cloud changes colors as it spreads out in the air, which y