Copper                             "Silver"                               "Gold"

To produce the silver penny: a zinc coated penny

• Prepare a 6 M NaOH solution (40 g of NaOH in 100 mL of water).  CAUTION:  This solution is very caustic and can cause severe burns.

• Add 1/2 teaspoon of powdered zinc to 6M NaOH solution.

• Heat solution, but do not boil.  Add clean penny to solution and stir with a glass stirring rod.

• Remove penny with tongs when completely silver in color.  (This will take about 30 seconds)

• Rinse penny in water.  Do not wipe off excess powdered zinc with paper towel.  When wet powdered zinc dries it gives off heat and can spontaneously cause fire.

To produce the gold penny: a brass penny (an alloy of copper and zinc)

• Using tongs, hold the zinc-coated (silver) penny over the flame of a Bunsen burner until the penny  turns yellow in color.

• Cool the penny in water.  The penny will look gold.  It is brass (an alloy).

If you need to clean a penny... add 1 tablespoon of table salt into 3 tablespoons of vinegar.  Place penny in solution and swirl.  An alternative is to use fine steel wool.  Pennies that are dirty will not zinc coat very well.

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