Copper Coin of Fire

This money is hot.

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Purpose -

One of the best demonstrations of a catalyst there is.

Nature - 

Demonstration

Materials - 

250 ml beaker, acetone, a clean shiny copper coin, copper wire, glass stirring rod, Bunsen burner

Method - 

· Attach the coin to the copper wire with a few loops and twists.  Attach the other end of the copper wire to the stirring rod so that when the rod rests on the rim of the beaker the coin hangs about 2 cm from bottom.  See Figure 1.

· Fill the beaker with about 1 cm of acetone.

· Using the Bunsen  burner, heat the coin until it glows red hot, then quickly hang the coin over the acetone so that it is just above the surface of the acetone.

· Watch the coin flicker with a golden plasma flame and stay red hot, (see Figure 2).   Turn lights off for best effect.

Safety -

Acetone is flammable and should be kept away from the Bunsen  flame.  It is also considered harmful and should be kept away from eye and exposed skin. Goggles are recommended.  The coin is very hot and care should be taken not to burn yourself with it.

Explanation -

The copper acts as a catalyst in converting acetone to acetaldehyde.  The reaction is :-

CH3-CO-CH3  =>   CH3COH

  The reaction requires heat to initiate but is highly exothermic, keeping the coin at a very high temperature once it is going.  The reaction will continue until the acetone is all evaporated, or until the coin is lifted away from the acetone.

Notes -

While there are no practical use for this particular reaction it does show the use of a catalyst to stimulate a reaction with it self being used.

To work well the copper coin needs to be very clean.  To do this soak the coin in 1M hydrochloric acid for a couple of hours, then wash and scrub with some steel wool.