Looking for a simple yet impressive STEM activity for kids? This Capillary Action science experiment is perfect!
Yes, it makes a pretty rainbow! The real magic is in the how — capillary action! More on that later, first let’s learn how to do it!
This STEM activity for kids is fun to watch in action. If your little scientist keeps a notebook (or if you think they’re ready to start!), kids seem to find illustrating this experiment to be especially fun!
Supplies For Capillary Action STEM Activity For Kids
- Paper Towels
- 2 Bowls
How To Perform Capillary Action STEM Activity For Kids
- Color the ends of a paper towel in matching rainbow colors using markers, nothing else will work. Make sure to fully saturate the paper towels or the capillary action won’t carry the color very far.
- Fill 2 bowls with water and place either end of the paper towel in the water.BE CAREFUL not to move the water during the process, or the colors will bleed and mix in the water and carry across the towel in that same pattern, ruining the rainbow.
- Watch the capillary action carry the water up both sides of the paper towel, meeting in the middle to form a full rainbow!
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. After the experiment is over, ask them what they observed. Then ask them what they think capillary action is!
After those observations and hypotheses 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 indeed the water molecules that are 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 — bright, unnatural dyed flowers are colored by employing capillary action!
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