This is a simple science experiment that can be done at home to demonstrate the capillary action of water. I am going to keep it as simple as possible as this is a science experiment for 4 -6 year old kids.
Capillary action happens when water defies gravity and moves up through pores in a porous materials. To understand this better, we have to know a few things about water.
1. Adhesion: When water particles stick to other materials.
2. Cohesion: When water particles stick to each other. This is why we see a water droplet holding its shape and not flattening out.
3. Surface tension: Cohesion pulls the water particles towards each other so that it forms an elastic surface on top. This is how we get water droplets that look like beads on waxy surfaces.
When a water comes in touch with a porous surface and when its adhesive force is greater than its cohesive force, water starts to climb. But since the cohesive force is still there, when one particle of water climbs, other particles follow too.
2 Empty glasses / cups (preferably see through)
1 Paper towel
Food coloring (Not mandatory but preferable)
Mix food color into the water. Roll the paper towel into a tube.
Pour the water into one glass and place the tissue paper as shown below.
Can you see how the water starts to climb up? Food coloring makes this easier to spot. Water color paint or ink can also be used for this experiment. We just need a colorful liquid.
Leave it undisturbed and after a few minutes, you can see the water climbing up and going down into the second glass.
The water levels keeps climbing up…
And stops when the level of water in both glasses are the same.
My daughter thinks
water escaped from one glass into the other.
Here is a video of the experiment if you want to show it to your kids. Do try this at home. Kids retain more when they try things out with their own hands rather than just reading about these concepts in a book.