The authoritative public forum
  for Metal Finishing since 1989
-----

How long did it take for the penny to dissolve?

Okay I'm doing a science project on " would soda dissolve a penny?' and I have done for two days and nothing had change.So what should I do?

Lorena G.
Student at SMM - Florida
2006

---

2007

What is the POINT of the experiment, Lorena? What is your hypothesis? What are you trying to learn? What you SHOULD do is write that the penny does not dissolve after two days immersion in soda, because that's the experimental procedure you followed and that's the result you got.

Is the penny pre-1982 (solid copper) or post-1982 (copper plated zinc). You can speed the process on post-1982 pennies by bending the penny in half with pliers or a vice to expose the zinc, but this may be sound advice or 'junk science' depending on your objective. 'Junk science' is altering the experiment to get the result you wanted instead of recording the actual results, and students should always get an 'F' on any project where they practice junk science. Of course, a few teachers should get an 'F', but that's a different topic :-)

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

---

Happy New Year Ted!
Maybe the original formula of Coca Cola would have been worth trying for this experiment! Based on the hypothesis given in the letter, I agree with your ending statement. Thanks for the great service you provide here!

Mark Baker
Process Engineer - Syracuse, New York
2007

---

January , 2007

Thanks for the kind words, Mark. I'm sure that Tom Pullizzi, co-founder of finishing.com but presently a science teacher, would help his students to a much better hypothesis.

I hold one of the world's best jobs! With people like you answering the tough finishing questions, I get to offer 'rhetorical answers' (if that's a valid term) to the easy student questions :-)

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

I'm doing a seminar about how soda is bad for you and I want to show how a penny dissolves in soda so they could see how much acid is in the soda. how long does it usually take for it to dissolve.

Desrai N.
cirkya - Los Angeles, California, USA
2007

---

First of two simultaneous responses --

Desrai, 2 days.

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
2007

---

Second of two simultaneous responses --

Soda is infinitely slow dissolving copper. It will work faster on the zinc center, but the copper cladding prevents any significant surface contact with the zinc. Also temperature and agitation are factors.

If you want a graphic demonstration, take a precisely measured cube of lean beef and put it into a glass of soda. Take pictures twice a day against a ruler. You will be shocked in a few days.

James Watts
- Navarre, Florida
2007

---

2007

I like Mr. Watts' suggestion because it at least brings us a tiny bit closer to science.

The media and the teachers don't want students to drink soda, and it's probably good advice. But to try to demonstrate that soda is bad for you by claiming that it can dissolve the zinc in a penny is only to present a complete non-sequitur as science; it's not even junk science :-)

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