Watch a rainbow come to life! This simple experiment creates a colorful reaction using a few household materials. Use the primary colors and see how the secondary colors emerge when water “walks” out of cups with the aid of paper towels.
6 clear cups/bowls/containers
food dye (red, yellow, & blue)
- Add a few drops of red dye to one cup, yellow to another cup, and blue to a third cup and fill them 3/4 of the way with water
- Arrange your cups in a circle alternating between dye cups and empty cups
- Cut your paper towels into 6 strips and place one end of each paper towel in a cup of dyed water and one end into an empty cup, repeat until the paper towel chain is complete
- 4. Now it is time to watch and see what the water does!
*After some time, the paper towels will saturate with the dyed water and then the water will start filling the empty cups. When the colors mix, they will create the secondary colors: green, orange, and purple.
*The process could take several hours depending on the absorbency of your paper towels so this is a fun overnight or all-day experiment. Just set up your cups and check in periodically to see how they have changed. If you want to speed up the process add more water to the dye cups.
While you wait:
*Discuss primary and secondary colors with your children, ask them what they think will happen to the cups and what colors will be made.
*Discuss how it is possible for water to be pulled out of the cups, against gravity, and into the adjoining empty cups–the answer is capillary action.
Capillary action is the ability of liquids to flow through narrow channels or porous materials often in defiance of gravity, this is how plants get water from their roots up to their stems. Water molecules naturally like to stay close to each other, this is called cohesion. Water molecules also like to attach themselves to other materials like paper towels in this instance, which is called adhesion. So, when the adhesion forces are stronger than cohesion forces, capillary action can take place, drawing the water up into the paper towels.
Keep checking back to see if your rainbow is forming, here the water has started to fill an empty cup with yellow and blue water making it green! You can add more water to the primary color cups to speed up the process.
At the end of the experiment, you will have equal amounts of colored water in each cup.
*If you have white flowers at your house, you can repurpose the colored water for another experiment. Simply place a cut flower into each cup and watch as the flowers take on the color of the dyed water (it could take a few hours to a day to see results). You can even split a flower stem between 2 cups to create a multicolored flower.
For more easy science experiments check out our eBooks on Overdrive