Doppler 9&10 STEM – Clean Those Pennies!

Mom and Dad, do you remember chemistry class? Then you might remember writing chemical reactions like this…

Cu + O2 -> 2CuO

2CuO is Copper Oxide also known as Rust. Rust is formed through a process called Oxidation. We see rust form on a daily basis on metals all the time. Whether it be the rust on your bumper, bike, pennies, and the GREEN Statue of Liberty. You know it was not always green. The copper on the statue has been exposed to oxygen since it was finished in the late 1880s.Penny

So we know that copper rusts easily over time… but is there a way to reverse rust… the short answer is yes! Pennies are much easier than the Statue of Liberty. So how do you reverse the process? Well, we need to convert the Copper Oxide (CuO) into a Copper molecule (Cu) and 2 Oxygen molecules (O2).

How do you do that? Add an acid like lemon juice. The acid separates the Oxygen molecules from the Copper molecules.

Here is what you need at home!

You Will Need:

A Paper Cup or Glass Cup

Lemon Juice


Paper Towel


Dirty Pennies


  1. Fill your cup half up with lemon juice
  2. Pour 1 tablespoon of salt into your cup
  3. Stir the salt into the lemon juice for 30 seconds or until salt dissolves
  4. Place dirty pennies into the lemon juice
  5. Wait 30 seconds to a minute, stirring occasionally
  6. Place the pennies on a paper towel to dry!
  7. Repeat as many times as possible until all your pennies are shiny!!!

If your kiddos try this experiment, send us photos of you and your experiment and you might get to see it during weather on The Four on Tuesdays and Thursdays!

Make sure you tune in every Tuesday for a New 9&10 STEM. Send us an email at weather@9& or find us on Facebook and at Doppler 9&10 Weather Team if you have a weather question or want something in science explained! It does not have to be weather-related! Anything Science or math-based we’ve got you! You can always get the latest forecast on as well as interact with us on social media!

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