Assuming that you are asking about US Lincoln cents: If they are dated 1909-1982 (except 1943-46) - they are 95% copper and 5% zinc (with a tiny amount of tin up through 1962) and weigh 3.089 grams (147 to the pound) - 3.25g of copper per. If they are dated 1982-onward - they are 2.5% copper and 97.5% zinc and weigh 2.500 grams (181 to the pound) - 0.0625g of copper per. If they are dated 1982 - its tough to tell, because both types were minted. If they are dated 1943 - they are made of zinc coated steel and contain no copper If they are dated 1944-1946 - they are made from old brass shell casings (I'm not sure of the copper content, but likely similar to other pre-1982 cents).
Copper
Copper penny
In 1903, the U.S. penny was made of bronze, which is an alloy of copper (95%) and tin (5%). The penny continued to be made of bronze until 1982 when it was switched to a copper-plated zinc composition.
Yes, the darkening of a copper penny is a chemical change. When copper is exposed to air and moisture, it reacts with oxygen and carbon dioxide, leading to the formation of copper oxide and other compounds that give the penny a darker appearance. This process alters the chemical composition of the copper, indicating a chemical change rather than a physical one.
The mineral that you can't scratch with your fingernail but can be scratched by a copper penny is calcite. Calcite has a hardness of about 3 on the Mohs scale, while fingernails have a hardness of around 2.5. A copper penny, which has a hardness of approximately 3.5, can easily scratch calcite.
The penny is made out of copper.
Copper
Copper pennies (95% copper, 5% zinc) weigh 3.11 grams. Modern zinc pennies (97.5% zinc, 2.5% copper) weigh 2.5 grams.
A penny.
PENNY
A 1993 penny is composed of 97.5% zinc and 2.5% copper. Therefore, the percentage of copper in a 1993 penny is 2.5%.
A 1983 penny is made of 95% copper and 5% zinc. The actual weight of copper in a 1983 penny is approximately 2.5 grams.
A penny
did they make 1982 copper penny by mistake
Yes. Dissolution of a copper penny would indeed be a chemical reaction.
zinc is 97.5% of the penny and copper is 2.5% of the penny
The penny turns silvery because the zinc (Zn) coats the outside of the copper penny. You then chemically combine the two metals when they share their electron cloud. That is why you burn the penny after you remove it from the Zn and NaOH mixture.