Making a Penny Glow: A Pre-1982 Trick
Before 1982, pennies were made of 95% copper with a small amount of zinc added. This composition allowed for a neat trick where the penny would glow red-hot when heated and dipped in acetone. However, after 1982, the U.S. Mint changed the composition of pennies to be mostly zinc with only a thin copper coating. This change ruined the glowing penny trick forever.
How to Make a Penny Glow
1. Take a pre-1982 penny and some stiff wire. Wind the wire around the penny so you can hold it like a marshmallow on a stick.
2. Carefully heat the penny over a propane torch or stove burner until it’s warm, but not melting hot.
3. Pour a couple tablespoons of acetone (found in nail polish remover or paint thinner) into a jar.
4. Holding the penny with the wire, lower it into the acetone so it just touches or is immersed in the liquid. Within seconds, the penny will begin to glow red-hot.
The Chemistry Behind It
Copper acts as a catalyst in this reaction. When a material burns, it needs to grab oxygen. Different materials require varying amounts of heat to start burning. Acetone generally needs more heat than a hot coin provides.
However, copper has a special property – it can grab hold of oxygen itself and pass it along to the acetone, overcoming the energy threshold needed to get it to burn. When the acetone burns, it releases heat that keeps the reaction going. The heat helps the copper grab more oxygen to pass to the acetone in a continuous cycle.
The penny itself is not diminished by the reaction. In fact, the heat may burn off any grime on an old penny, allowing it to glow better than when it started.
Why Modern Pennies Don’t Work
Sadly, zinc doesn’t have the same catalytic effect as copper. Since post-1982 pennies are mostly zinc with just a thin copper coating, the trick no longer works. The zinc core is unable to facilitate the acetone’s ignition.
So if you want to try this awesome glowing penny trick, you’ll need to hunt down some pre-1982 pennies. The U.S. Mint’s 1982 change in penny composition ruined this fun experiment forever[1][2][3].
Read More
[1] https://www.flinnsci.com/api/library/Download/674479ccda964683ac6201381ffbdb89
[2] https://cmes.utah.edu/outreach/Zinc%20Plated%20Penny%20Lesson%20Plan%20-%20revised%208-21.pdf
[3] http://home.miracosta.edu/dlr/110exp4x.htm
[4] https://www.pearson.com/channels/general-chemistry/asset/45b6e34a/the-zinc-in-a-copper-plated-penny-will-dissolve-in-hydrochloric-acid-if-the-copp
[5] http://sciencewithscreens.blogspot.com/2016/08/experiment-59-stripping-copper-coating.html
[6] https://www.youtube.com/watch?v=6kQ8c-S3K4E
[7] https://www.flinnsci.com/api/library/Download/365b4b2351cb42e1ba36a3df936cb7f2
