16 July 2006

The Value of a Penny

My big project this month is studying chemistry; because all the entry-level chem classes at City College are already closed, and I don't get to register until August, my best bet for getting into a chemistry class this fall is to learn enough material to pass a placement test into a middle-level course. This means learning AP Chemistry in a month. (I could have saved myself a lot of work if I had embraced my inner geek in 10th grade rather than trying to write angst-ridden poetry.)

Today while I was reading my chem textbook I was distracted by a sidebar note about a 1982 change in metal composition of the penny. I did some more research, and here's what I found:

Until 1982, pennies, were, for the most part, 95% copper and 5% zinc or zinc/tin alloy. In 1982, rising prices of copper caused the US Mint to change the composition of the cent coin to 97.5% zinc and 2.5% copper. Curious, I decided to calculate the actual value of the metal in each type of coin. I also used density values of each metal to determine the volume of each coin (which should remain roughly the same, otherwise we'd notice the coin being a different size).

Pre-1982 US 1-cent coin:

mass: 3.11 grams
composition: 95% copper, 5% zinc
volume: 0.354 cc
value of metal: $0.0246

1982-present US 1-cent coin:
mass: 2.50 grams
composition: 97.5% zinc, 2.5% copper
volume: 0.353 cc
value of metal: $0.00884

Canadian 1-cent coin:
mass: 2.35 grams
composition: 94% steel, 1.5% nickel, 4.5% copper
volume: 0.291 cc
value of metal: $0.00328

(These calculations are based on the data I was able to cull from the web: copper is worth $0.00814/g, zinc is $0.003542/g, nickel is $0.02893/g, and steel is$0.000631/g.)

So, the metal in a US penny issued before 1982 is actually worth about 2.5 cents. A penny hoarder with a smelter could turn a profit by melting pennies down and selling the metal as scrap!

There has been public debate about whether the US one-cent coin is obsolete and should be removed from circulation. As we see above, the metal in the coin itself is worth almost $0.01 already, which means that the cost of making the coin probably means a loss for the US Mint. Pennies are popular, however, which is one reason why they are kept in circulation.

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