Classic Thermite Reaction

A thermite reaction is a really good example of a redox reaction in action! Here is how to do the classic demonstration with iron and aluminum:

Key Takeaways

  • Fe2O3 (s) + 2 Al (s) → Al2O3 (s) + 2 Fe (s)
  • The reaction needs high activation energy. Once it is running it becomes self-sustaining
  • Thermite reactions produce an extreme amount of heat, which liquefies the produced iron 

Recipe for Thermite

How to ignite Thermite

  1. Prepare the thermite reaction mixture, by mixing 40g of iron (III) oxide with 10g of powdered aluminum.
  2. Place some aluminum foil in the clay pot and pour the reaction mixture in the pot. Place the clay pot in the ring stand.
  3. Move the apparatus to a fireproof area
  4. Stick the magnesium ribbon in the reaction mixture and start igniting it with the blow torch. 

How the Thermite Reaction works:

The thermite reaction can be described by the chemical equation below:

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

This reaction is initiated by heat (burning Mg) and becomes self-sustaining. The
reaction generates oxygen and therefore combustion occurs even in the absence
of oxygen. The reaction creates so much heat that the iron generated is melted.
The melting point of iron is 1530 °C and has ∆Hfus = 14.9 kJ/mol. The overall free
energy change (∆G) of this reaction at 298 K is -838 kJ/mol

Experiment Video