7 Demonstration: Walking Water

Supplies:

5 clear cups

Red, yellow, and blue food coloring

3 cups water

Paper towels

Question: Set up the cups of colored water and then ask what will happen when we add our paper towel “bridges” to the cups?

Directions: Set the cups up in a row and add a cup of water to cups 1, 3, and 5. Add a different color of food coloring to each cup of water. Fold 4 half-sheets of paper towel into long strips length-wise as seen in the picture. Fold them in the middle and join the cups with the paper towel strips into “bridges.” Over time the colored water will travel between full and empty cups, blending the colors.

Theory: Water travels up and over the paper towels through capillary action. This is similar to how water travels from the roots of a plant up to the leaves.

Grades: 1st – 4th grades

Time: 20 minutes or so. Observe periodically while you do another activity.

Clean-Up: All liquids can go down the drain. Wash and re-use the cups.

Notes and Hints: You may use as many cups as you like and many colors of food coloring.

Image Credit: https://www.sciencebuddies.org/stem-activities/walking-water