Letter 13102

WHICH SOLUTION WILL CHANGE THE COLOR OF A PENNY THE QUICKEST? WHY? 

WHY DOES A PENNY OXIDIZE WHEN PLACED IN A BASE SOLUTION, LIKE baking soda [link is to product info at Amazon] ? WHY IS THERE LESS OXIDATION OF A PENNY IN AN ACID SOLUTION, LIKE LEMON JUICE?

RHONDA L.
- EL PASO, TX , USA

We really need to know whether you are in 3rd grade or high school, Rhonda, as we can't answer appropriately without knowing what science and chemistry concepts you already understand and which you haven't heard of yet. But if you understand the concepts of 'oxidation', 'base' and 'acid', then the answer might just be hitting you now that an acid offers an abundance of hydrogen which is more or less incompatible with an oxide forming on the penny. Rather, an acid dissolves oxides. Good luck.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

copper will turn deep brown-pitch black if placed in a Liver Of Sulphur [linked by editor to product info at MisterArt] (potassium sulphide plus water) weak acid are used to clean copper thats why the lemon juice will clean it, bases do not clean it and just build up a smut on the surface

Anthony O'Connor
- Dublin, Ireland

Thanks for the follow-up, Anthony. The thing is, liver of sulfur is not safe for young children to fool with! Even a high-schooler should perhaps use it only under supervision of the science teacher. So I also thank you for pointing out one of the problems with many student questions: it's not possible to answer a question appropriately if we don't know whether the student is a 3rd grader vs. a senior in high school.

Ted Mooney finishing.com Brick, New Jersey

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