How to Clean a Penny

As part of our trio of science experiments this past week, my daughter and I made a mixture to clean a penny.  This is a fairly common experiment in school science labs, but if you haven't done this before, definitely do it.  It's another easy science experiment that requires few supplies.  First gather a few dirty coins.  I found a quarter and 2 pennies that could use a good cleaning.

Dirty coins.

Now take about a 1/4 cup of vinegar and a teaspoon of salt and mix them together in a small bowl.  I used standard table salt.  Drop the coins in and let them sit for 10 - 20 seconds.  Then take them out of the mixture.  You should notice that they are much cleaner than they were before placing them in the mixture.

In the process of being cleaned.

Shiny!

The pictures do not do this experiment justice.  I think you can tell that the pennies taken out of the mixture are cleaner and shinier, but it was much more apparent to the naked eye.  So what's going on here?  Vinegar is an acid that reacts with the salt to remove copper oxide from the surface of the pennies, making them shinier.  The quarter was thrown in to test if much would happen.  The quarter might have been a bit cleaner, but it was hard to tell.  

This experiment isn't done yet.  There's much more you can do with it as I'll describe in a future post.