How to Make Gold Pennies – Science Experiment
Learn about the science of alloys: copper + zinc = brass
How to Make Gold Pennies Science Experiment
Have you ever wondered what pennies are made of? Can you turn pennies from copper to gold? In this amazing Steve Spangler Science experiment, you’ll learn about the science of alloys: copper + zinc = brass. This golden penny lab will have your friends and your family talking about how you turned pennies into gold! But don’t get too excited, this copper-to-gold experiment doesn’t result in ACTUAL gold.
How to Turn Pennies Gold
At first glance, there appears to be something a bit strange (yet really amazing) about a gold penny. First, gold pennies don’t really exist. Modern day alchemists, cleverly disguised as ingenious and creative chemistry teachers, often share the secret of how to turn pennies gold. Students will take home an unforgettable lesson in alloys in this golden penny lab, creating a keepsake penny that can never be put back into circulation. You’ll be able to amaze your friends with this fake gold penny.
SAFETY NOTE: At Steve Spangler Science, we always practice safe science! This activity requires adult supervision. NaOH should be handled with great care: it is highly corrosive and can burn your skin. In addition, zinc dust should never be inhaled. Safety glasses should be worn throughout this entire activity.
- 20 mL of 6 M NaOH
- 0.1 g zinc dust
- Evaporating dish (a glass beaker works great!)
- Hot plate
- 200 mL beaker of water
- Bunsen burner or a propane torch
- Safety Glasses
Put on your safety glasses.
Pour 20 mL of NaOH solution to the dish.
Add the zinc dust in the dish with the NaOH, and gently swirl the mixture together.
Set the hot plate to medium heat and place the evaporating dish on top.
Heat for 5 minutes. Do not boil. When the dish is hot, place a penny in it. Heat for two minutes or until the penny is coated and becomes silver in appearance.
Remove the penny from the dish with tongs and drop it into water. When cool, wipe the penny clean with a cloth to remove any excess zinc.
Using tongs, hold the penny in the flame of a Bunsen burner and gently heat. The penny should turn “gold” (brass). (Do not overheat the penny.)
Dip the penny in the beaker of water until it is cool to the touch.
How Does It Work
Even though it’s a gold-colored penny, the U.S. Treasury has historically had a little problem with people trying to buy things with these “fake” gold pennies. In 1983, the Treasury started making pennies with a zinc core with a copper coating. It turns out that they weigh less and cost less to make than their pre-1983 counterparts, which were made with an alloy of 95% copper and 5% zinc.
In this activity, soaking the penny in the zinc solution actually coats the surface of the penny with zinc atoms. When the zinc-covered penny is heated, the copper atoms of the penny and the zinc atoms that coat the penny mix and turn gold in color. This mixing of metals is an alloy called “yellow brass.”
Artists often work with alloys like bronze, steel or brass because of their durability, malleability and color. Bronze is a mixture of copper and tin. Brass, made in the activity above, is a mixture of zinc and copper. Steel is made of iron and carbon. Alloys are used to make coins, jewelry, sculptures and other everyday items.
The Golden Penny Lab Experiment: Steve Spangler Science
This golden penny lab can be a great science experiment and can be a lesson in learning what pennies are made of. It is also a fantastic lesson on how to make brass. Follow the directions above with a responsible adult and experience the change for yourself! Don’t miss our other Steve Spangler Science online experiments that make great science fair demonstrations and activities. Can’t get enough of these copper to gold penny experiments? Visit our other chemistry experiments available at Steve Spangler Science and see how chemistry is working in the world around us.
SAFETY INFORMATION: Safe Science
This safety note is important enough to repeat! This gold penny activity requires adult supervision. Because it is corrosive and can burn skin, NaOH should be handled with great care. Zinc dust should also not be inhaled. Safety goggles must be worn throughout this entire activity.
SAFETY NOTE: This activity requires adult supervision. NaOH should be handled with great care. It is corrosive and can burn skin. Zinc dust should not be inhaled. Safety goggles should be worn throughout this entire activity.