Capillary Action STEM Activity for Kids

Looking for a simple yet impressive STEM activity for kids? This colorful capillary action science experiment is perfect!

Two things I love about this STEM project include:

We set it up, and then come back to check on it later. I think the fizzy, action-packed experiments (like this one!) are fun, but sometimes it’s nice to have an experiment that the kids want to keep coming back to and check on! It seems to me that they spend more time pondering about what’s going on and continuing to think about the experiment when they aren’t with it. I like to see these concepts sink in!
It looked really pretty sitting on our countertop!

Prep for Capillary Action STEM Activity For Kids

While I love the pretty colors in the experiment (my kids did too!) the real magic is in the how this happens — capillary action! We’ll chat more about that later, first let’s learn how to do it.

If your kid scientist keeps a notebook (or if you think they’re ready to start!), illustrating this experiment is simple and fun!

Paper towels or tissues
Food coloring
5 glasses or clear plastic cups about the same size
Water

How To Perform Capillary Action STEM Activity For Kids

Fill 3 of the 5 glasses with water. 2 will stay empty!
To one of the water-filled glasses, add 5-10 drops of red food coloring.
To the next water-filled glass, add 5-10 drops of yellow food coloring.
To the final water-filled glass, add 5-10 drops of blue food coloring.
Arrange the glasses in a row in this order, from left to right: red, empty glass, yellow, empty glass, blue, like this:
Cut a paper towel into four similar size strips, or fold 4 tissues into one inch strips. Fold the strips in half.
Place about one half of the first paper towel (or tissue) into the first empty cup, and the other half of the paper towel into the red water glass. Do the same thing between the other cups, and it should look like this when you are done putting the paper towels in:

8. Next step, wait! And observe. Come back to check on the glasses every couple of hours, check them again after overnight. After 24 hours our glasses looked like this:

View this post on Instagram

A post shared by Buzzy 🎉 (@momlifemadeeasy)

So What Exactly is Capillary Action?

It sounds really important – it’s ACTION after all! Let your kids know that this experiment demonstrates capillary action. Ask them what they think will happen when you first set up the experiment.

After the experiment is over, ask them what they observed. Then ask them what they think capillary action is!

After those observations are discussed, get into the meat of what capillary action is! In short, it’s the movement of water within a porous material — in our case, a paper towel.

What’s really interesting is that while it looks like the paper towel is “soaking up” the water, it is in fact the water molecules that are defying gravity and doing the climbing!

A prominent example in nature is tree roots using capillary action to “drink” water from the ground. And a not-so-natural example can be found in many grocery stores — the bright, unnatural colored (think bright, almost neon colors!) flowers are colored by employing capillary action!

You Might Also Enjoy: