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Presidents Day Science with Pennies

This article appeared in the February 17, 2017 edition of the Davis Enterprise.

Presidents Day Science with Pennies

President Lincoln's portrait on a penny. Photo by Beyond My Ken.


By Lisa Justice

Special to the Enterprise


In honor of Presidents Day this weekend, try this fun and easy science activity at home featuring a tiny item with a portrait of Abraham Lincoln on it--a penny!


You will need: a few dirty pennies, salt, white vinegar, measuring cups and spoons, a small bowl and some paper towels. Start by combining 1 teaspoon of salt and ¼ cup of vinegar in the bowl and stir it up until the salt dissolves.


Then dip one penny half-way in. Hold it for a few seconds, then take a look. What do you see? Can you tell a difference in so short a time?


Now dump all the pennies into the bowl. Watch what happens in the first few seconds. Do you see any changes happening?


Let your pennies soak for a few minutes, then take about half of them out and lay them on a paper towel to dry. Don’t rub, rinse or blot them; just lay them out on the paper towel and let them air dry.


Then take the rest of the pennies out of the salt and vinegar solution. Rinse them thoroughly in water to remove all traces of salt and vinegar, then lay them on a second paper towel to dry.


Let both sets of pennies dry for about an hour, then take a look at them. What do you see? Any differences? What do you think is causing the differences you can see?


Pennies are made of copper. The longer pennies are exposed to the air, oxygen from the air mixes with the copper to create a layer of copper oxide, making the pennies look dirty.


But copper oxide will break down when it comes into contact with a weak acid like vinegar and salt. So dipping or soaking pennies in the vinegar and salt solution removed the copper oxide and made the pennies look like shiny copper again.


But did all the pennies stay shiny after their bath? Probably not! The pennies that were rinsed with water probably still look pretty good, but your unrinsed pennies may now be a bright green.


Your unrinsed pennies may still have some salt on them. Salt has chlorine in it. When that chlorine combines with copper in the pennies and oxygen in the air, it forms malachite, a chemical compound known for its greenish color.


Can you use what you’ve learned with your pennies to figure out why the Statue of Liberty is green?



Explorit’s coming events:


●      Summer Science Camp registration is coming soon! Details will be coming to soon.

●      Explorit’s Exploration Gallery is open to the public every Wednesday, Saturday and Sunday, 1:00-5:00 p.m. and every Friday, 3:00-6:00 p.m.  Admission is $5.00 per person; Explorit members, teachers and children 2 and under are free. Come check out the new Nano Mini Exhibition!

●      Interested in membership? Think your Explorit membership may have lapsed?  Call Explorit at 530-756-0191 to check or sign up!

●      Birthdays are fun with science at Explorit! Choose Super Birthday Party topics to make this a special event! Call Explorit at 530-756-0191 for more information or to book your party.


Explorit Science Center is located at 3141 5th St. For more information call (530) 756-0191 or visit, or “like” us on Facebook at

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