Note: Contact The Fire Systems Group at Michael.Mari@colorado.edu ANDJohn.Humphrey@colorado.edu (email BOTH) ahead of time to have the smoke alarms disabled during the class period when thermite will be performed.
Igniting a mixture of Fe2O3 and Al with a magnesium ribbon fuse produces molten iron and aluminum oxide in an impressive exothermic reaction.
2Al(s) + Fe2O3(s) → Al2O3(l) + 2Fe(l) + ∆
For Fe2O3, ∆Hfo = -824 kJ/mole
For Al2O3, ∆Hfo = -1673 kJ/mole
∆Hrxn = -849 kJ/mole
Heat produced raises the products to the melting point of iron (1530oC / 2790oF). For 50g Fe2O3 and 15g Al, ∆T is approximately 5744oC.
To Conduct Demonstration
- Pick the beverage can up to show the students. Place the can under the drainage hole in the flower pots.
- Ignite the propane torch using the mechanical self-lighter.
- Ignite the magnesium ribbon wick until it is white hot, then step quickly back.
- After the thermite burns, pick the soda can up with the tongs and show the students the hole burned through it.
Demo Time: 5 - 10 minutes
- Have a fire extinguisher handy and place the safety shield between the reaction and the audience.
- Keep the reaction cart a safe distance (at least 6ft) from the front row.
- Wear goggles and heat-protective gloves.
- Do not use water to extinguish flames or to cool products (explosive hydrogen gas can be produced when water comes into contact with molten iron).
- Perform in a well-ventilated room.
- Check floor and sweep if it is slippery due to tiny iron balls. Once cooled, the soda can and iron metal can be disposed in the trash.
Shakhashiri, B.Z. Chemical Demonstrations: A Handbook for Teachers of Chemistry; 1983.