The Thermite Reaction

    The reaction being demonstrated below is called a "Thermite" Reaction.  Thermite is a generic name given to high temperature reactions between a metal oxide and aluminum.  The thermite reaction shown here is the single replacement reaction between iron(III) oxide and aluminum to produce aluminum oxide and elemental iron:

Fe₂O₃(s)     +      2 Al(s)      Al₂O₃(s)      +     2 Fe(s)     +      heat

    As the equation shows, this reaction releases heat energy and is thus considered exothermic.  The standard enthalpy change in this reaction is -849 kJ/mol (DH° = -849 kJ/mol).  Thus 849 kJ of energy is released for every mole of iron(III) oxide that reacts!!  With such a large amount of energy being released, the temperatures produced can reach values as high as 2200 °C!!   Since the melting point of iron is 1530 °C, the iron produced in the reaction is actually formed in the liquid phase at temperatures well above a thousand degrees celsius!!!

    To start the reaction, a sample of the thermite mixture, powdered aluminum and iron(III) oxide, is placed inside of a clay pot.  The reaction is ignited by inserting a burning sparkler (remember, even exothermic reactions absorb some energy, but even more energy is produced).  The reaction then proceeds by releasing lots of energy in the form of both heat and light.  Molten iron is seen to drip out of the bottom of the clay pot and into a pile of sand placed below it.  The liquid iron will continue to glow and emit heat for several minutes until it cools to a hard, black solid.