Penny Water Drop Challenge

It’s summertime, and that means summer rain showers, glasses of ice-cold water, and maybe even some sprinkler or pool fun. 😎 At the Science Bar, we’re busy learning about water and exploring some of its cool properties. Today, we’re sharing one of our activities with you!

Here’s what you’ll need:

• A penny
• An eye dropper, straw, or pipette
• Water

Here’s what you do:

Using your eye dropper, straw, or pipette, slowly begin to drop small water droplets onto your penny. Count your drops as you go and continue adding drops until your penny finally overflows. How many were you able to add? What do you notice as you add drops?

Now, remember that this is a challenge. Try it again! How many drops can you add this time? Can you beat your record? Try it with a family member. Who can add the most drops to their penny?

Why did the water form a bubble on the penny?

Great question! We love this activity because it’s super simple, but also teaches some awesome science concepts. The water formed a bubble over the penny for two reasons: cohesion and adhesion. These are pretty big words that are used to describe water’s “stickiness.” We don’t normally think of water as sticky, but water molecules just love to stick to each other and to other substances.

Cohesion – the stickiness that water molecules have towards each other. Water molecules from your new droplets stuck to water molecules from your first droplet. Instead of overflowing, the droplets formed a nice round bubble shape on top of the penny.

Adhesion – the stickiness that water molecules have towards other things. In addition to sticking to each other, the water molecules also stuck to the penny! That’s another reason your droplets didn’t overflow immediately.

Want to learn more?

We’re doing this activity and other water science fun at the Science Bar in the Museum! We’re open for all and would love to have you join us.