Drops on a Penny Experiment

How many drops can you fit on a penny? Use an eyedropper to squeeze water, drop by drop, onto a penny and put this science trick to the test!

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This experiment shows that water’s pretty sticky, and one of its favorite things to stick to is itself! That’s why when you add a droplet to the penny, it grabs onto the drops already there.

But water doesn’t like to stick to air (or the penny) as much. Wherever it’s touching them, it hugs together extra tightly and forms a “skin.” The skin helps hold the water together (kind of like putting it in a bag) and makes the nice, round water bubble you see on the penny!

Scientists call this skin “surface tension.” It’s what makes water drops round, lets rain roll off an umbrella, allows water striders to literally walk on water — and what makes a belly flop hurt so much!