Aluminum reacts with water to form various oxides of aluminum plus hydrogen gas, with the release of a great deal of heat. The primary reactions are:
2Al + 6H2O ---> 2Al(OH)3 + 3H2
2Al + 4H2O ---> 2AlO(OH) + 3H2
2Al + 3H2O ---> Al2O3 + 3H2
It is kind of interesting how much heat is released by the oxidation reactor of aluminum - until you realize that most common heat producing reations are acutally just oxidation reactions, such as burning logs in a fire or gasoline for your car. Most people do not think of a fire as a chemical reaction.
I have been asked, "if aluminum can be used for rocket fuel why doesn't aluminum foil just burst into flames when it is put in the oven?" The reason is due to particle size. As a particle gets small the ratio of surface area to volume increases. This is because the surface area is the square of the particle radius and the volume is the cube of the particle radius. So if you were to oxidize a 1 cm block of aluminum only the outside 6 sq cm would oxidize which would evolve heat but very little heat relative to the volume of the block. Now if you had a tiny particle of aluminum and oxidized it there would be a huge amount of heat generated on the surface relative
to the miniscule volume of the particle. So much so that the particle will glow red or white hot.
The 1 cm block that had 6 square cm oxidize generated just a tiny amount of heat, if that 1 square cm of aluminum is ground into fine particles and ignited it would be a rather spectacular fireworks display, because the surface area has increased a 1000 fold (not an actual number - it can be calculated but I am suppose to be working!).
I know that most people on this site already know this but - so what I think it is kinda cool how the relatively simply math can be applied to real world stuff - it is sorta like science.
edited to change the word alumina to the proper aluminum. Alumina is the oxidized form of aluminum.