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Science Experiment: Cleaning Pennies!
You will need:
Tarnished Pennies (These are the darker ones that aren't shiny anymore.)
Small Cups and Paper Towels
Ketchup
Water
2 or More Additional Solutions: Vinegar, Coke, Mustard, Mayo, Juice, Milk or Lemon Juice.
Pour a small amount of each solution into a cup. Be sure to include one water cup and one ketchup cup. These two cups can be enough, but more solutions are even more fun!
Take the pennies and place one into each cup. Be sure each penny is well coated.
Let the pennies soak for about five minutes. Place a square of paper towel in front of each cup. This will be where you place your coins for comparison. Keeping the pennies in front of the cups will help you remember which solution they were each in. Have additional paper towels available to wipe off any remaining solution from the pennies. We want to clearly see the pennies.
Now check your pennies! Which one is the shiniest? Are you surprised that ketchup did so well?
To explain the chemistry of making pennies shiny again, we first need to understand the chemistry of how they became tarnished in the first place. Oxygen in the atmosphere has a negative charge that is attracted to the positive charge of the copper in the penny. The two react to form copper oxide, which is darker in color. The older the penny the longer these forces have been at work, making the penny darker and darker as copper oxide increases.
In this experiment, we are actually creating a chemical reaction that breaks down the copper oxide. What works best is an acid combined with salt. Ketchup is acidic and the acid breaks down the copper oxide. The acid in ketchup is acetic acid, commonly known as vinegar. Ketchup also contains salt. Salt adds chloride that bonds with copper to form copper chloride, which allows the acid to break up even more copper oxide! The salt helps speed up the chemical reaction.
If you included other solutions in your experiment, what were the results? Look on the jar or bottle's ingredients label. Do you see anything that would explain the chemical reaction we just learned about? What happened to the penny soaked in water?
You don’t have to stop after doing this experiment once. Try more solutions. Make your own mix of vinegar and salt at different concentrations. Try leaving the pennies in the solutions for different lengths of time. Who knew learning how to clean a penny could be so much fun?
AGE GROUP: | Family | Children |
EVENT TYPE: | Youth Program/Class | Online |
TAGS: | STEM | STEAM | Science | Critical Thinking |
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