My wife and I go skiing in the winter and we purchase chemical hand an foot warmers. What chemicals are found inside these and what is the chemistry responsible for this exothermic reaction?

Generally they contain tiny piece of iron , water , activated carbon , salt , water reservoir and a mineral called vermiculite

When iron is exposed to air than it begin to oxidize and produce heat. the other ingredient performs number of different activity like salt works to spread the chemical reaction , carbon is used to distribute the heat and vermiculite is used to insulate the warmth that's generated .