At-Home STEM Activities: Chemical Reactions with Pennies
the statue of liberty, in New York City, has welcomed generations of immigrants to america since it was erected in 1886.
The Statue of Liberty is known today for its iconic blue-green tint. However, it has not always been this recognizable color. When the statue was first unveiled to the American people in 1886, it was a shiny copper color, just like a penny! This is because the surface of the Statue of Liberty is covered with thin copper sheets, the same element that pennies are made of. It took about twenty years of exposure to weather to turn the Statue of Liberty from its shiny new penny color, to the green it is today. This color change can be explained by - you guessed it, science! What happened to the Statue of Liberty can be explained by a chemical reaction. The thin copper sheets on the outside of the statue react with the oxygen in the air and produce a green oxcide. In the Statue of Liberty’s case, this copper oxcide continues to react to make copper carbonates, copper sulfide and copper sulfate. These three main compounds produce the blue-green color. The chemical reaction, which creates this color, is just a patina on the metal that is created to protect the metal from corrosion and degradation.
Watch Oxidation Happen At-Home
I have been on the quest for simple science experiments to do at home, where virtually any family would have the supplies in their home to conduct the experiment. This chemical reaction with pennies experiment was the perfect, low maintenance activity, which teaches kids important principles in chemical reactions and demonstrates why the Statue of Liberty is the color it is today!
This chemistry experiment uses an acid, vinegar, and, a base, salt, in one bowl to clean copper pennies, and in another bowl, just vinegar to turn a penny green! When dirty pennies are placed in vinegar and salt, the copper oxide on and some of the copper on the penny dissolve in the water and is removed from the pennies surface. When the penny is rinsed off and wiped clean, it looks brand new! When a penny is soaked in just vinegar, it speeds up the process of oxidation and over a few hours the penny will be greener.
Supplies:
White Vinegar
Iodized Salt
Paper Towels
Small (non-metal) Bowls
A Few Old Pennies
Take Note: Pennies made in 1982 or earlier are made of solid copper, use them in this reaction to make it work even better. Pennies made after 1982 are made from copper and zinc, so the reaction is less.
1.Rip a paper towel to fit into your small containers and line the bottoms. Place your pennies in each small bowl.
2. Pour the vinegar and salt into one small non-metal bowl and stir to dissolve. Pour just vinegar into the other small bowl.
3. After just 30 seconds you should start to notice the pennies in the bowl with the vinegar and salt will start to lose their outside dirty layer. Flip the pennies over and let them soak for another 30 seconds. Then rinse the pennies in water and wipe clean. Ta-da! Shiny new pennies.
pennies in vinegar at start of experiment
pennies in the salt and vinegar begin to shine up immediately
4. Check back on your pennies in the vinegar and salt about one hour later. They should be developing a green layer. Keep checking back on your pennies, 2 hours, 3 hours, 1 day, etc, to see the changes.
pennies in vinegar 1 hour later. Noitce the green layer forming on both.
on the left the penny from 1984 and on the right the penny from 1944.
5. I was able to find one penny minted in 1944 and one from after 1982. I put both back in the vinegar and salt mixture to see if I could get them even shinier. The penny that was from 1944 was significantly cleaner then the penny from after 1982, which is a mixture of copper and zinc, instead of pure copper on the 1944 penny.
What is Going On?
A chemical reaction has occurred! A chemical reaction is the combination of two reactants to form something entirely new. A penny is made of copper. The vinegar on the paper towel helps the copper in the penny easily react with the oxygen in the air to form a blue-green colored compound called malachite.
