Corrosion is a process that occurs when metals react with the environment. Although corrosion is naturally occurring, kids can mimic the process in the science lab or your own kitchen using coins and a few materials found around the house. Because of its quick reaction to the elements, copper is a great metal to use for your experiments. The most kid-friendly and readily available copper is a penny, so scoop out some pennies from the couch cushions, you'll be ready to start experimenting.
Salt and Vinegar Test
The salt and vinegar experiment is a fun way for kids to learn what copper looks like when it corrodes. Simply lay a copper penny on the bottom of a clear plastic cup. Sprinkle a dash of salt onto the penny, followed by a capful of white vinegar. You will notice that the penny comes clean almost immediately after pouring on the vinegar. Now that the copper surface is clean and exposed to the oxygen and moisture in the air -- watch what happens next. Remove the penny from the cup and place it on a clean paper towel. After a few hours, the penny will begin to turn green from corrosion.
Test the corrosive qualities of soda using your favorite can of pop and a tarnished penny. Simply place the tarnished penny in the bottom of a clear plastic cup and pour just enough soda over the penny to cover it. Check the cup every day for one week to note any changes to the penny. After one week’s time, you should notice that the penny is nice and shiny, indicating that the soda has eaten away at the tarnish; a testament to its corrosive nature.
Saltwater and Freshwater
Saltwater is more corrosive to metals than freshwater and the proof is visible when the two are put to the test with a copper penny. Place two clear plastic cups side by side, dropping a single copper penny onto the bottom of each. Pour distilled water over both pennies, adding a teaspoon of salt to only one of the cups. Allow the pennies to sit in the cups for five minutes. Remove each penny after the waiting period and place them on a clean paper towel. After several hours, you will notice that the penny that was in the saltwater solution will begin to corrode faster than the one that was not.
Soaking a penny in lemon juice for five minutes is also a great way for kids to learn about the corrosion. The acid in the juice polishes a dirty penny, making it look like new. Place a dirty penny into a clear plastic cup and add just enough lemon juice to cover the penny. Allow the penny to sit in the lemon juice for approximately five minutes before removing. Rub the penny with a paper towel, note how the corrosive qualities of the juice acids render the penny squeaky clean, and free of tarnish and all signs of age.