Hopefully you downloaded my observation sheet to use when you have your students grow clover for St. Patrick’s Day. Today I want to share another fun activity to do with your students around March 17th. This activity is a great way to practice making colors!
Materials: clear cups, paper towel, and food coloring.
Here is what you do:
Each cup will need its own paper towel. Fold and trim the paper towels so that they will rest easily into the cups. Make sure the paper towel to touch the bottoms of each cup, but not rise up too far out of the top.
Line up the cups in an arc to resemble a rainbow or a circle like you see below.
Fill cups 1, 3, and 5 with water. Leave cups 2, 4, and 6 empty. Because the next step involves adding food coloring and stirring, fill up the cups only half way. This will make the next step easier if you choose to have the students do the stirring.
Stir a few drops of red food coloring into cup 1. Stir a few drops of yellow food coloring into cup 3. Stir a few drops of blue food coloring into cup 5.
Insert a folded paper towel into each cup as shown below so that one end of the paper towel is in a cup with colored water and the other end is an empty cup. Be sure to leave cups 2, 4, and 6 empty.
Almost immediately you should start to see the water climbing up the paper towels. Carefully add more water to the cups with colored water so that they almost reach the top. Then leave your cups alone for a couple of hours and when you return you’ll have a rainbow!
Here is the science behind this activity:
Just like water “climbs up” the roots of plants from the soil, the colored water in the cups climbs up the paper towels, against gravity. This is called capillary action. The paper towel is a very absorbent, so the colored water is able to move through it very quickly. It then drips down into the empty glass. The color of the two primary colors mixes to create secondary colors!!
Have fun doing this science activity!