Here is what you need to do for this quick and easy-to-replicate Capillary Action Science Experiment.

Start out by putting 7 glasses on the counter. Fill glasses 1, 3, 5, and 7 most of the way up with water.

Next add food coloring to the glasses:

• 5-10 drops of red food coloring to glass 1 and 7
• 15 drops of  yellow food coloring to glass 3
• 5-10 drops food coloring to glass 5

Now, your experiment set-up should look like this.

Finally, take a paper towel and fold it in half width wise, fold it again, and again, and again. Now put one side of the folded paper towel into one glass and the other side of the paper towel in the next glass. Repeat with the remaining cups.

Walking Water Science Experiment

Here comes the fun part! Watch capillary action in motion as the water climbs up the paper towel.

Capillary action is the process in which a liquid moves up something solid, like a tube or into a material with a lot of small holes. This happens when 3 forces called cohesion, adhesion, and surface tension work together. Water molecules are considered cohesive (sticky to each other) and they adhere (stick) to the paper towel. As one water molecule moves up the paper towel it pulls the other molecules with it. The molecules pull each other along like a drawstring.

Notice how the water has walked or moved along the paper towel.

How cool is that?! The cup that had nothing in it is now equally filled with the ones on either side. The water stops walking when the water is at the same level next to it.

Here is what you end up with – a beautiful rainbow of colors that walked and mixed by itself  while your kids observed capillary action first hand!

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