You might’ve seen our first experiment where we explained what acids and bases are and how to use red cabbage to tell whether liquids are acidic or basic.
The experiment we are doing today is all about chemical reactions that you can see. Both pennies and the outside of the Statue of Liberty are made of copper, but you might notice that they aren’t the same color. This is because Lady Liberty became oxidized, her copper mixed with oxygen to form copper oxide and turned green over time.
We are going to do a simple experiment at home to show how this can happen!
What you need:
10 Pennies (the more dull the better!)
1. Start off by filling 2 small bowls with ~1/4 cup of vinegar and 1 teaspoon of salt each. Mix thoroughly until the salt is dissolved.
2. Take a penny and dip it halfway into the bowl. Count to 15 slowly and pull it out. What happened? Did the dullness go away?
3. Add 5 pennies to one bowl and 5 pennies to the other bowl and let them sit for a few minutes. What can you see happening? The mixture of salt and vinegar (acid) dissolves the copper oxide and restores the copper atoms to their shiny state.
4. Next, take the pennies from one bowl and rinse them with water and let them dry on a paper towel.
5. Take the other pennies from the other bowl and place them directly on another paper towel without rinsing. Let’s wait and see what happens!
6. Wait about an hour and go back to see what the pennies look like. What do you see?
Check out our results!
You should notice that the pennies you rinsed with water are more shiny than when you started the experiment, that’s because the vinegar and salt ate away at the copper oxide.
You should notice that the pennies you put directly on the paper towel are starting to turn green! Your green pennies have what is called a patina. A patina is a thin layer that has formed on the surface of your penny from “weathering” and oxidation from the chemical reaction we just put the penny through. Like we mentioned before, the Statue of Liberty is covered in a thin layer of copper and because she sits out in the elements and is surrounded by salt water, she has a patina similar to our green pennies. You can learn more fun facts about Lady Liberty by visiting the National Park Service website.