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What are the chemical reactions to a penny

i am doing an eighth grade science fair project. the topic has to do with chemistry, physics and stuff. so I think that doing research on the chemistry is appropriate. does copper tarnish appear if joined with oxygen? if so, how long? or, if not, what does, because why is this tarnish brown, when the statue of liberty is green? if acids work well on dissolving the tarnish on pennies, why not on other coins? on one of the other questions, it said that acids clean surfaces better and bases clean pores better. coins are coins right? or are the metals different? they are made the same. I couldn't find anything on pennies or the chemistry of copper, zinc, oxygen, acids, bases with pennies in all the chemistry books and this is the only helpful site so far on reaching the requirement. there is nothing on the faq about chemistry of pennies in detail.

Jane U
student - Northridge, California, USA
February 20, 2008

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Our FAQ on Cleaning Pennies contains a lot of these answers, but not all, Jane. You can probably get the composition of other coins from the website of the US Mint at www.usmint.gov, but clearly other coins are a different color and they are not made of the same material as pennies.

A penny will turn the same color as the Statue of Liberty is it sees the same exposure conditions, but it usually doesn't. Pennies are kept indoors and are oily and frequently handled. But if you visit the beach and find an old penny in the cracks of a boardwalk you will see that it's green. I believe the green color is a copper carbonate ⇦ this on eBay or Amazon [affil links] , from reaction with the carbon dioxide in the air, but it wears off. All that stays on a penny is the brown coating because it is harder and more wear resistant. Good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
February 21, 2008

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My name is Jace, I am in the sixth grade, and I signed up for the science fair this year. in my science project I filled five Jars with 1/4 cup of the following substances: orange juice, lime juice, coca-cola, salt water, and tap water. Do I need to make any changes or adaptations for this to work, possibly, better?

Jace S.
Student - Pickton, Texas
April 15, 2008