Physics Photo of the Week

January 30, 2009

Thermite
Chemistry professor Dr. Steven Cartier recently demonstrated a rather violent Thermite reaction.  The reaction consists of common Aluminum metal and Fe2O3 (common Iron oxide).  This mixture of Al and Iron oxide is "unstable". 
The bonds between the Aluminum and the Oxygen are stronger than the bonds between the Iron and Oxygen.  This means that it can achieve a state of lower energy by breaking the Iron-Oxygen bonds and forming Aluminum-Oxygen bonds instead.    However, a large "activation energy" is required in order to break the Iron-Oxygen bonds to start this reaction.  The materials need to be pre-heated so the mixture has enough thermal energy to break the Iron-Oxygen bonds.  Once this reaction is started the smaller energy state of the final products emits a tremendous amount of heat.  The smaller image at right shows Dr. Cartier lifting the resultant hot incandescent Iron metal out of the bucket of sand.

In order to initiate this process, Potassium Permanganate (KMnO4) is mixed with the Al metal and Iron Oxide in a clay flower pot.  The Potassium Permanganate is unstable and easily oxidizes some glycerol that is carefully poured onto the mixture.  The Permanganate glycerol reaction produces enough heat to
initiate the main Al - Iron Oxide reaction (see the photo at left below.  Finally a video clip is shown below right.  The reaction is started in the clay flower pot.  As the molten Iron is formed, it drips through the hole in the bottom of the pot into the sand bucket below.  In the final frames, the sand bucket as well as the clay pot are both glowing red from the very high temperature.








Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department.  These photos feature an interesting phenomena in the world around us.  Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation.  Atmospheric phenomena are especially welcome.  Please send any photos to dcollins@warren-wilson.edu. 

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