Why is the Statue of Liberty green? It’s a beautiful patina, but how does it happen? Explore the science in your own kitchen or classroom by making green pennies! Learning about the patina of pennies is a classic science experiment for kids!


Green Pennies, polishing pennies, and copper science for kids


Science experiments with things found in your purse or pocket? Get ready to add this simple penny experiment to your science activities this season. If you want to learn how to turn pennies green and what cleans them, let’s dig in! While you’re at it, make sure to check out our other penny experiments.


Our science activities and experiments are designed with you, the parent or teacher, in mind!  Easy to set up, quick to do, most activities will take only 15 to 30 minutes to complete and are heaps of fun!  Plus, our supplies lists usually contain only free or cheap materials you can source from home!

green pennies from ordinary pennies copper science


Get yourself a dozen dull pennies and try out a double science activity with polishing pennies and making green pennies. Either one is a fun science activity in itself, but together they make a great science project and help kids to understand further why green pennies and the Statue of Liberty look the way they do!


We know that copper is shiny and bright, so why do these pennies {that are copper} look dull? Well, the atoms in the copper when mixed with oxygen atoms in the air form copper oxide which is the dull surface appearance of the penny. Can we polish it? YES, keep reading to find out!

Adding the green pennies to a mixture of salt and acid {vinegar} dissolves the copper oxide and restores the copper atoms to their shiny state.

What is the scientific method?

The scientific method is a process or method of research. A problem is identified, information about the problem is gathered, a hypothesis or question is formulated from the information, and the hypothesis is put to the test with an experiment to prove or disprove its validity.  Sounds heavy…

What in the world does that mean?!? The scientific method should be used as a guide to help lead the process. It’s not set in stone.

You don’t need to try and solve the world’s biggest science questions! The scientific method is all about studying and learning things right around you.

As kids develop practices that involve creating, gathering data evaluating, analyzing, and communicating, they can apply these critical thinking skills to any situation. To learn more about the scientific method and how to use it, click here.

Even though the scientific method feels like it is just for big kids…

This method can be used with kids of all ages! Have a casual conversation with younger kiddos, or do a more formal notebook entry with older kiddos! You can even turn this into a science fair project!

Click here to get your FREE printable mini Science Pack!


  • So what makes green pennies green?
  • What is copper?
  • What does all this have to do with the Statue of Liberty? 


  • white vinegar
  • salt
  • water
  • bowl with a good size bottom base
  • a teaspoon
  • paper towels
  • pennies
Green Pennies Science Activity Supplies Vinegar Salt


STEP 1: Prep the green pennies science experiment by filling 2 small bowls with about 1/4 cup of vinegar and a teaspoon of salt each. Mix thoroughly.


STEP 2: Before dropping about 5 pennies into the bowl. Take one and dip it halfway into the bowl. Count to 10 slowly and pull it out. What happened?

Add a few more pennies and let them sit for a few minutes. What can you see happening?

Make sure to add 6 pennies to the other bowl too.


STEP 3: Now, take the pennies from one bowl, rinse them and let them dry on a paper towel. Take the other pennies from the other bowl and place them directly on another paper towel (do not rinse). Let’s wait and see what happens.

Alternatively, try out other acids like lemon juice and other citrus juices and see which ones work best!

Can you see the differences between the two groups of pennies, the rinsed and unrinsed pennies? Do you now have some green pennies? I bet you do! Your dull pennies should either be green or polished!



Your green pennies have what is called a patina. A patina is a thin layer that has formed on the surface of your copper penny from “weathering” and oxidization from the chemical process we just put the penny through.

Why is the Statue of Liberty Green?

The Statue of Liberty is covered in a thin layer of copper. Because she sits out in the elements and is surrounded by salt water, she has a patina similar to our green pennies. It would be a huge job to polish her!



Kids’ science experiments are numerous! Easy to set up, budget-friendly, and filled with opportunity!

Printable Science Projects For Kids

If you’re looking to grab all of our printable science projects in one convenient place plus exclusive worksheets and bonuses like a STEAM Project pack, our Science Project Pack is what you need! Over 300+ Pages!

  • 90+ classic science activities with journal pages, supply lists, set up and process, and science information. NEW! Activity-specific observation pages!
  • Best science practices posters and our original science method process folders for extra alternatives!
  • Be a Collector activities pack introduces kids to the world of making collections through the eyes of a scientist. What will they collect first?
  • Know the Words Science vocabulary pack includes flashcards, crosswords, and word searches that illuminate keywords in the experiments!
  • My science journal writing prompts explore what it means to be a scientist!!
  • Bonus STEAM Project Pack: Art meets science with doable projects!
  • Bonus Quick Grab Packs for Biology, Earth Science, Chemistry, and Physics