What type of metal is a 2008 penny made of?

Answer 1

Here's the history, according to the U.S. Mint: * From 1837 to 1857, the cent was made of bronze (95 percent copper, and five percent tin and zinc). * From 1857, the cent was 88 percent copper and 12 percent nickel, giving the coin a whitish appearance. * The cent was again bronze (95 percent copper, and five percent tin and zinc) from 1864 to 1962, except: In 1943, the coin's composition was changed to zinc-coated steel. This change was only for the year 1943 and was due to the critical use of copper for the war effort. However, a limited number of copper pennies were minted that year. * In 1962, the cent's tin content, which was quite small, was removed. That made the metal composition of the cent 95 percent copper and 5 percent zinc. The alloy remained 95 percent copper and 5 percent zinc until 1982, when the composition was changed to 97.5 percent zinc and 2.5 percent copper (copper-plated zinc). Cents of both compositions appeared in that year.

Answer 2

All US cents since mid-1982 are made of a zinc core plated with copper. The coins are 97.5% zinc by weight.

So much to learn, so little time. My husband and I decided to sup at a local Chinese restaurant near where we live. I had no idea what my column this week was going to be about and I nearly had given up hope of seeing something fascinating enough to merit writing. Since I like to watch the large goldfish swimming around in the garden pool near a set of booths, I asked to be seated there. As I gazed into the water, my eye was drawn to all the coins on the bottom. They were surrounded by a green furry algae but, oddly, the coins themselves didn't have any algae on them. I had to find out why.

My research started with looking up what coins are made out of. My thoughts were that pennies were made of copper, nickels of nickel or some form of that, and quarters out of steel or some other alloy. Boy, did I have some misconceptions. In 1792, when the US Mint was established, the law required that all coins be made from gold, silver, or copper. Gold was used to make the $10, $5, and $2.50 pieces. Silver was used to make the half-dollar, dollar, quarter, dime, and half-dime. Copper was used to make the penny and half-cent. Other coins were minted in gold, silver and copper as there became a need for other denominations. This was okay until during the Depression in 1933 when the US Mint stopped making gold coins, and in 1965, due to a silver shortage, the U.S. Congress dictated that silver was no longer going to be used in dimes and quarters and even the half-dollar was to be reduced from 90% to 40% silver content. The silver part of the half-dollar was totally eliminated in 1971. The composition of coins, now, is much different than it was then. Quarters and dimes are composed of copper-nickel clad with an outer layer of a 75% copper, 25% nickel alloy with a pure copper core. Nickels are relatively the same copper-nickel alloy but without the copper core. Pennies used to be 95% copper, 5% zinc until 1982 when they obtained their current composition of 97.5% zinc, 2.5% copper mix. This composition made the penny less expensive to make and lighter.

This lead to my realization that the one thing all these coins had in common was that they were partially made out of copper. Which, by the way, doesn't violate the law that all coins must be made out of gold, silver or copper. The next step was to see what properties of copper could affect the algae. This step was quite enlightening. First, I found out that nitrogen and phosphorus promote algae growth. Not helpful. Next came the discovery that copper is a well known algaecide and bactericide. Silver is also known to kill bacteria and viruses too. This ionization process is used in many Swimming Pools as an alternative to using chlorine and other harsh chemicals. Even NASA uses the Copper/Silver Ionization treatment as a method to purify drinking water aboard spacecraft. Even though I knew nothing of this method of cleaning water, it seems it was used back in the days of wagon trains where silver and copper coins were tossed into the drinking water barrels to help purify the water. So this is my answer, right? The copper in the coins killed the algae and bacteria. Not quite. It got a little complicated from here.

I was quite satisfied that I had found the answer in the copper killing the algae, but I got curious about what properties of the copper killed the bacteria. Most pool cleaning articles recommended copper ions levels being around .20 ppm and .30 ppm (parts per million). Here is a quick description of what an Ion is. An ion is an atom or group of atoms that possess an electrical charge. There is a nucleus with positively charged particles called protons in it and negatively charged electrons orbiting around the nucleus. Atoms usually contain an equal number of protons and electrons. Ions get electrical charges by losing or gaining electrons. When an ion gains an extra electron, it becomes negative and is called an ANION and when it loses an extra electron it becomes a positive CATION. Time to look up the chemical composition of copper and how copper is ionized in water. Copper's chemical symbol is Cu and it has an Atomic Mass of 64, contains 29 protons and 35 neutrons. It is number 29 on the Periodic Table. The melting point of Cu is 1083 degrees Celsius. Ouch! Copper or Cu is one of the transition metals which means that electrons from it's outer electron layer or shell participate in chemical reactions. This seemed good since I wanted to know how the copper ionized the water and killed the bacteria. The next discovery was a bit...disturbing. Copper or Cu is water resistant. Water Resistant????? but...but.... Of course, there are copper pans for cooking, copper pipes for water and all are water resistant and since copper is a relatively unreactive metal except on galvanized metal where copper becomes corrosive.

The next step was a difficult one. What in the water in that indoor pond was causing the copper to ionize. Some ideas I came up with were the possibility of chlorine in the water which would react with the copper to produce cuprous chloride or Copper (II) Chloride or perhaps the pH of the water was too high or low. It seems the algae like a high pH from 7.4 - 9 though some other algae like a 5.0 to 7.0 low pH. It was mentioned that a pH of 8.0 will make the pond or pool color seem green, it didn't seem we had a high pH as the water didn't show much of that color though we had thought to ask permission to take a water sample to test it. It had to be something in the water that was reacting to the copper in the coins and killing the algae. Wrong again...well sort of.

Nearly completely wrong, I found my answer. It is also the reason when trying to rid a pond or pool of algae, it is recommended that the copper solution is distributed directly on the algae. It seems that since the algae is negatively charged and the copper ions form electrostatic bonds on the negatively charged areas on the cell walls of the microorganisms. This leads to distorted cell wall permeability and minimizes the normal intake of life sustaining nutrients. It also attacks sulfur containing amino acids that resides in the proteins used for photosynthesis inside the algae cell as the copper is absorbed in. There was the answer and the reason that only the spots where the coins were didn't have algae. Only algae that comes in contact with the copper in the coins would be killed by it since it requires the electrostatic bonds to be formed between the algae and the copper. This is not at all where I expected this research to go but I learned many interesting facts in my search for the answers and I think that is what makes science enjoyable.

Answer 3

Since 1982, U.S. pennies have been 97.5% zinc and 2.5% copper.

Answer 4

If it is a US cent, it is zinc with a very thin coating of copper.

Answer 5

A 2008 penny is primarily made of copper-plated zinc. The outer layer is composed of 2.5% copper and 97.5% zinc, while the core is made of pure zinc.

Answer 6

ALUMINUM