Turn Pennies Into Gold

Gold PennyWant to turn pennies into gold?  It’s actually a pretty easy chemistry, or should I say alchemy, trick.  With the price of gold the way it is today, turning pennies into gold could make you a millionaire.  I’ll show you how to mix a few chemicals, along with fire, to create gold pennies.

Seriously though, there’s no way to turn an old penny into real gold.  Actually, I take that back.  You would just need to bombard the pennies with protons and neutrons until they turn to gold.  Not the most cost effective way of getting your hands on some gold.

The good news is, you can turn old pennies into what looks like gold.  It’s really easy to do and fairly safe, although the safest of procedures can still be dangerous if the person carrying it out is, shall we say, careless.  We all know the kid who sticks a fork into an outlet…

Anyway, these “gold” pennies are great party favors and totally safe for kids.  In fact, they still retain their antimicrobial properties even after the transformation (see Coins are Antimicrobial!).  Why do the coins appear to be gold?  When you mix the copper coins with zinc and sodium hydroxide, then heat them, you create a layer of brass on the outside of the coin.  If you’ve ever seen brass before it looks a lot like gold.

Why must you use pennies with pre-1983 dates?  In 1983 the U.S. mint changed the composition of pennies to be 2.5% copper and the balance zinc.  The copper only lightly coats the zinc in new pennies.  However old pennies consisted of 95% copper and 5% zinc.

Get your chemistry on and make some gold plated coins!  Just be careful.  The provided procedure is accurate to my knowledge and fairly safe.  Use common sense; don’t eat the zinc, it will eat your stomach and may do other weird things.  An adult should supervise, and all that jazz.  Do this at your own risk; we (ChemistryTwig) are not responsible for any injuries, deaths, property damages, or other mishappenings if such may occur after using this procedure.  Now that all of that is out of the way, go make some gold (okay, bronze)!

Materials
U.S. copper pennies dated 1982 or earlier
Zinc, granular
Sodium Chloride (Table Salt)
Vinegar
NaOH (3 Molar or so)
Distilled Water

Procedure
1.) mix 15ml of vinegar and 3g of vinegar in a beaker, place in pennies.
2.) Mix 25ml NaOH 3M and 1 gram Zinc, heat on hot plate (or stove) until steaming, in a ceramic dish.
3.) Dry off pennies and place them in the ceramic dish.
4.) Remove when pennies are coated in “silver.”
5.) Place them in a beaker of distilled water.
6.) Using tongs, heat them in Bunsen burner until “gold.”

The Chemical Reaction

Zn(s) + 2NaOH(aq) → Na2ZnO2(aq) + H2(g)
ZnO2 2- ions migrate to Copper penny and are reduced.
When heat is added (in the form of fire) the Zincate ions and Copper combine to produce Brass, a metal alloy.

Safety
Goggles need to be worn due to possible splashing of NaOH solution when heating, a strong base, also when heating do not breath in fumes. Pennies are hot when heated in Bunsen burner and possible zinc dust can be within the granular zinc which is highly flammable.
Oh, and don’t eat or drink any of the chemicals. Almost forgot that one!

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