|A penny is heated to glow red-hot and hung over acetone.|
The penny glows until all of the acetone is consumed.
The copper penny catalyzes the oxidation of the acetone to its combustion products of CO2 and H2O. However, although the combustion products are being formed, keep in mind that combustion itself is not taking place. The copper is simply providing a catalytic surface for the acetone to react upon.
The copper, being a catalyst, is not expended during the reaction.
An NSF funded Project