A thermite reaction is a type of reaction in which a metal oxide is reduced by using aluminum as the reducing agent. It is generally exothermic in nature, meaning that a large amount of heat is liberated. Due to this heat, the metals produced are in the molten state. An example of a thermite reaction is the reduction of iron (III) oxide by using aluminum powder. The equation for this reaction is:

Fe2O3(s) + 2Al(s) ⟶ 2Fe(l) + Al2O3(s) + Heat

The iron obtained in this process is in the molten state and can be used for welding purposes. This reaction is used to join railway tracks (welding rails) or cracked machine parts. The thermite reaction is also used industrially for the preparation of metals from their oxides and the production of incendiary devices. It is important to note that this reaction produces intense heat and molten metal, so a fire extinguisher should be readily available at all times. Water should not be used to extinguish the reaction, since addition of water to hot iron produces potentially explosive hydrogen gas. Since fires resulting from thermite reactions can be difficult to control, the chemicals should not be used in larger amounts than suggested. A safety shield should be used for protection from sparks.