Have you ever thought about how many drops of water can fit on a penny? Explore the surface tension of water with this fun and easy penny lab for kids. We are always on the hunt for simple science experiments, and this one is just super fun and easy!
Penny Lab Experiment
Let’s investigate how many drops of water can fit on a penny. Grab your purse, turn over the couch cushions, or break out the piggy bank; it’s time to find some pennies to experiment with!
Watch the video:
Supplies:
- Pennies
- Eyedropper or pipette
- Water
- Food coloring (makes seeing this in action MUCH easier, but is optional)
- Small bowls
Penny Experiment Set Up:
STEP 1: Add water to both of your bowls, and one of them, add green food coloring. This is optional if you want to see the drops a bit better.
STEP 2: Use an eyedropper or pipette to pick up and carefully drip one drop of water at a time onto the penny.
STEP 3: Count how many drops you can fit onto one penny until the water overflows.
We were able to get ours up to about 27! Go ahead and record the data for separate trials on the same coin. What can you conclude?
TIP: If you want to add a little variety to this experiment, swap out the pennies for nickels, dimes, and quarters. Ask your students to guess how many drops will fit on each coin. Record the date from the experiment and make a class graph chart with your results!
Get Your Free Printable Penny Lab Guide!
Why Do So Many Drops Of Water Fit On A Penny?
Were you surprised that a lot more drops of water fit on a penny than you predicted? We had 27 drops of water on ours!
What property of water allows the water to stick to the penny? Surface tension and cohesion are why you can get so many drops of water on a penny.
Cohesion is the “stickiness” of like molecules to one another. Water molecules love to stick together! Surface tension is the result of all the water molecules sticking together. Learn more about the surface tension of water!
Once the water has reached the edge of the penny, a dome shape begins to form. This is due to the surface tension forming a shape with the least amount of surface area possible (like bubbles)!
What happens if you use a different liquid like alcohol? Can you as many drops on a penny?
More Fun Penny Experiments
- Sink the boat challenge!
- Penny Spinners
- Green Pennies Experiment
- Paper Bridge STEM Challenge
- Lemon Battery STEM Project
Use the Scientific Method
This drops of water on a penny experiment is a fantastic opportunity to use the scientific method and record your experiment using the free mini worksheet pack.
You can read about using the scientific method here, find more information on independent and dependent variables and writing a hypothesis!
Apply the scientific method to this drops-on-a-penny science activity and turn it into a surface tension experiment by choosing a question to investigate.
- How many drops do you think will fit on a penny? (PREDICTION)
- What happens when one drop of water meets another drop? (OBSERVATION)
- Which coin held the most water? (EXPLANATION)
- Can you think of everyday examples of surface tension? (APPLICATION)
More Fun Surface Tension Experiments To Try
Explore surface tension with these science activities…
- Floating Paperclip: Observe how a paperclip floats on water due to surface tension.
- Magic Pepper Experiment: Sprinkle pepper on water in a shallow dish. Touch the surface with a soapy finger and watch the pepper scatter.
- Magic Milk: Make colorful patterns of food coloring in milk when you add soap.
- Soap Powered Boat: Watch how a drop of soap propels a boat forward due to surface tension.
Helpful Science Resources
Here are a few resources that will help you introduce science more effectively to your kids or students and feel confident presenting materials. You’ll find helpful free printables throughout.
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