Where the
world gathers for metal finishing
Q&As since 1989


-----

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 ? WHY IS THERE LESS OXIDATION OF A PENNY IN AN ACID SOLUTION, LIKE LEMON JUICE?

RHONDA L.
- EL PASO, Texas , 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.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

---

copper will turn deep brown-pitch black if placed in a liver of sulfur [on eBay or Amazon] (potassium sulfide 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, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey