how do you know if a penny is pure copper?
U.S. pennies made after 1982 are copper coated zinc. Before that, they were a 95% copper alloy with zinc during most years.
In 1943 (wartime), they were steel. Those quickly rusted and were discontinued.
There were copper-nickel alloy pennies in the 1860's.
Dr WLS has given you a physical way of determining the answer; i.e., by looking at the date. For a chemical answer, you can test for Zn in a solution of a penny.
Another way is determine the density of the penny and see if it matches the density of copper.
To determine if a penny is made of pure copper, you can follow these steps:
1. Identify the penny's age: Pennies minted before 1982 are typically made of 95% copper, while those minted after 1982 are made of 97.5% zinc with a thin copper plating.
2. Check the weight: A pure copper penny weighs about 3.11 grams. You can use a small digital scale to measure the weight accurately.
3. Look at the color: Pure copper pennies have a reddish-brown color, whereas the post-1982 zinc-based pennies have a lighter, more golden hue.
4. Observe the edges: Copper pennies typically have a smooth and even rim, while zinc-based pennies may show a slight seam or line where the copper plating meets the zinc core.
5. Conduct a magnet test: Pure copper is not magnetic, so if a penny is attracted to a magnet, it likely contains a significant amount of zinc.
Remember that some pennies may have undergone wear, which can affect their appearance. If you are still unsure, you can consult a professional or use more specialized testing techniques.