Making a "Gold" Penny

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MATERIALS

-          Pennies (must be very clean)

-          600mL beaker

-          200mL 3M NaOH

-          15g zinc powder

-          Bunsen burner or torch

-          Tongs

-          Hot plate

-          Gloves

-          Goggles
 

PRESENTATION

-          Fill the 600mL beaker about 1/3 full of the NaOH solution and place on the hot plate

-          Add about 15g of the zinc powder and begin heating at a high hot plate setting

-          After the solution begins to boil, drop a clean penny in and wait about 1 minute

-          Pull the penny out of the solution and then rinse it with water.  The penny is now plated with zinc which looks like a “silver penny”

-          To make a “gold penny,” dry the zinc plated penny off and heat it over the Bunsen burner for a few seconds.  This will make a brass alloy on the outside of the penny.

This demonstration may will work best if the solution is heated at the beginning of class.

DISCUSSION

-          Alloys

-          Electrochemical process

-          Voltage potentials

HAZARDS (MSDS Links)

 NaOH http://www.sciencelab.com/msds.php?msdsId=9924999

REFERENCES

 Shakhashiri, B. Z. In  Chemical Demonstrations: A Handbook for Teachers of

Chemistry; The University of Wisconsin Press:  1992; Vol. 4, p 263-268.