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What effect does soda have on pennies mass/weight?

I've done many trials, putting pennies from the year 1987-2006.before putting pennies in soda, majority of pennies weigh the same. I've weighed the pennies before and after putting it into the soda to sit for a week.i used pepsi soda. once pennies are taken out they come out to be either 0.1 gram heavier or -0.1/ -0.3 grams lighter. what I don't seem to understand is why did the pennies come out to way more or less after taken out of pepsi soda if they weighed the same before I put them in the same soda. does the aging of penny effect its mass/weight when taken out of soda and WHY?

Christy B.
student - Falls Church, VA, USA
January 23, 2009

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The acid in the soda will eat the zinc center of the penny IF it can get to it. Some pennies have a contiguous copper coating which is only minorly affected by the acids in sodas. some do not.
Weight gain almost has to be from the formation of corrosion products. To be fair, boil the pennies for 5 min in fresh distilled water, dry well and weigh. The dry well and cool is critical.

James Watts
- Navarre, Florida
January 26, 2009