Can Taco Sauce Clean Your Penny?-Teacher Edition
Question: What ingredient in Taco sauce actually cleans your penny?
Materials:
Dirty Pennies
Taco sauce
Vinegar
Tomato Paste
Salt
Water
Small Plates
- Place a tarnished penny on your plate and cover it with Taco Sauce.
- Use your fingers to smear the taco sauce all over the surface of the pennies.
- Remember to wash your hands… and don’t lick your fingers
- Keep the sauce on for 2 minutes
- Rinse the penny in the sink
- Compare the top with the bottom
How does the side of the penny that had the taco sauce compare with the side that didn’t have the taco sauce?
The side of the penny is much cleaner than the other side –very shiny!
Now we are going to try and see which of the ingredients in taco sauce is responsible for making the penny clean?
- Place equally tarnished pennies on the 4 labeled areas on your paper plate. See illustration
- Cover the pennies with the various ingredients and allow them to sit for 2 minutes.
10. Rinse the pennies from each test plate with water.
Which ingredient cleaned the pennies the best?
None of the ingredients did a good job of cleaning the dirty pennies. In fact, the results were terrible!
Are you surprised?
Yes-answers will vary
11. Now place equally tarnished pennies on the next plate already labeled for you.
13. Cover the pennies with each of the mixtures
14. Wait 2 minutes for them to react
15. Rinse pennies
Which combination of ingredients cleaned the pennies the best?
Vinegar and salt should be the mixture that cleans the pennies the best.
What is the explanation for this? (Wait for your teacher to help the class with this)
Neither vinegar nor salt by themselves cleaned the pennies, but when they were mixed together something happened. The chemistry behind the reaction is somewhat complicated but very interesting. Salt breaks down into sodium ions and chloride ions and it is the chloride ions that work with the copper ions on the penny. It is also well known that a mixture of lemon juice and salt does a good job in removing tarnish from metals and works very well on pennies. By themselves, the salt which is a weak acid do very little in the way of removing the coating of copper oxide on the penny, but together these ingredients make a great cleaning agent.