The chemical properties of iodine are very similar to those of bromine and chlorine. It is, however, much less reactive. It can also act as an oxidising agent that can reduce a number of elements such as phosphorus, aluminium, zinc and iron Usually, though, high temperatures are required.
Aluminium, despite its normal inert behaviour, is a very reactive metal. The inactivity that is normal is due to a generally impermeable layer of aluminium oxide on the surface.
The oxidation of finely powdered aluminium by iodine can be started by simply using a few drops of water, which starts a spectacular reaction that produces clouds of purple smoke.