First, we looked at the penny and made observations. Lillie said that the darker/dirtier pennies were older. I showed her how to tell when the penny was made by looking for the date on the coin.
Next, we decided to clean them. First, we tried putting them in water and we noted no change in their apperance.
We filled one dish with water and soap and observed that there was no change in their appearance. In a third dish, we added 2 teaspoons of salt and 1/2 cup of vinegar.
I held one penny 1/2 way into the vinegar/salt mixture and
it cleaned 1/2 of the penny.
We cleaned a few more.