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This month at my daughter’s preschool, we have been teaching the kids about money with the annual Coin Wars fundraiser. And since we had the family coin jar out and readily available, we’ve been doing all sorts of fun preschool STEM activities with coins this week. First up? A simple test of fine motor skills and water surface tension. Be sure to grab your FREE printable chart at the end of this post to record your results!

Can Coins Hold Water?

I love doing simple science experiments with my preschoolers because at that age, science verges on magic. (Who am I kidding – I still think science is magical at 35!) This simple preschool STEM activity with coins teaches little learners about the magic of surface tension, while also making for an awesome fine motor challenge with eye droppers.

Drops on a Coin Supplies

Best of all, this requires very few supplies, all of which you very likely already have in your home or classroom. That makes the project essentially FREE. You will need a small cup of water, an eye dropper, and an assortment of spare coins. For ease of clean-up, you may also want to lay a paper towel down on the table underneath the coins.

Supplies

Coins – pennies, dimes, nickels and quarters
Water
Eye dropper
Paper Towels
Drops on a Coin Record Chart

Scientific Method – Preschool Style

Even preschoolers can grasp the basics of following the scientific method, and it can be applied to this simple experiment.  Start with defining the question: How many drops of water can a coin hold?

Then, encourage your preschoolers to make a guess, or hypothesis, as to the answer. This could take the form of a specific number of drops, or which coin they think will hold the most water.

Next, it’s time to test their hypothesis. Using an eye dropper, have them carefully add one drop of water at a time to the surface of a coin. Count how many drops the coin can hold before the surface tension breaks and the water spills over.

You can record your predictions and findings on the printable chart below. Use it to record trials (repeating the same experiment again and again) or the results of each student if you are conducting these preschool STEM activities as a group.

Record your results using our printable chart. Print multiple copies – first record the number of drops by experimenter or trial. Then, use a second copy to color the boxes to create a simple bar graph of your findings.

Water and Surface Tension

Some preschoolers may want to understand the magic behind this simple science with coins. That magic is the surface tension of water. Water molecules like to stick together. They are attracted to one another, and the force of attraction creates surface tension. This is what allows you to add more water to the surface of the coin than you likely guessed at first, and why the water bubbles up on the surface of the coin, creating a ‘dome.’

Eventually, the weight of the water and the force of gravity (that holds us all to the Earth), overpowers the surface tension, and the water spills over the side of the coin.

More Preschool STEM Activities to Test

Your preschooler will likely be engrossed just dropping water on the coins over and over again, but you can ask lots of fun math and science questions along the way. Which coin holds the most/least water? Does the head or tails side of a coin hold more water? Does surface tension apply to other liquids? What happens if you add soap?

If you enjoyed this post, be sure to check out our favorite school fundraiser, Coin Wars, to teach your preschooler about money while also giving back to your school. We also love this FREE printable from Carrots are Orange to visually teach kids the Value of a Dollar. Stay tuned for more learning fun with coins coming up next week – what cleans coins best? You can find all of these and more on our STEM for Kids – Science board.

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