The Pretty Pretty Pennies Experiment
The Pretty Pretty Pennies Experiment
With this easy science experiment, you will learn why older pennies are darker and greener compared to newer ones.
Before you start the experiment, it is important to know why pennies get their gloomy color with age. The copper atoms that are found in pennies are attracted to the oxygen atoms that are found in the air we breathe. When these two kinds of atoms combine, they form copper oxide. Pennies look dirty and dark because they are covered with copper oxide. Now that you know this, you can learn how to get rid of that copper oxide and show off your shiny new looking pennies!
Materials for the experiment:
- 15 to 20 dirty pennies
- ¼ cup white vinegar
- 1 teaspoon salt
- Spoon
- A non metal bowl (usually a clear shallow one will work best so you can see the reaction)
- Paper towels
Experiment:
- First, put the salt and vinegar into the bowl. Stir it with the spoon until all of the salt dissolves.
- Put all of your pennies in the bowl. Leave them for five minutes. Watch the pennies as they go in. What’s happening?
- Now take half of your pennies out and place them on a paper towel.
- With the second half of pennies that are still in the bowl, take them out and rinse them off well in the sink. Then place them on a separate paper towel from your first half of pennies. Make sure to note that these are the rinsed ones!
- Wait 45 minutes to an hour and check back on the two piles. Notice the differences between the two? What do you think happened? Make your penny cleaning hypothesis!
The science behind the experiment:
You might have noticed that the rinsed pennies are a lot shinier than their non rinsed friends. This is because when the vinegar and salt dissolve the original copper oxide, they make it easier for the copper atoms to once again join with the oxygen in the air and the chlorine found in the salt. The chemical reaction with copper oxide begins to happen once again if the pennies are not rinsed with water. However, when the pennies are rinsed, it prevents this reaction from happening so quickly, leaving you with beautiful copper pennies!
