CHARLOTTE, N.C. — This is one of the easiest science experiments to do at home with the kids, but one of the fastest, most fun, and most rewarding!
What you’ll need:
- Food coloring
- Water
- Measuring cup
- Clear cups
- Paper towels
PREVIOUSLY: Science Sunday: Making a milk rainbow
Two things I noticed while practicing the experiment at home before work:
- The choose-a-size paper towels work best or you’ll have to cut them in half
- You may think you’re doing too much food coloring, but the more pigmented, the better!
Step 1: Set up five cups of water in a row
Personally, I put about ⅔ a cup in each, but it doesn’t have to be the same amount of water. I wanted to do this for the aesthetics.
Step 2: Mix up five different colors!
The food coloring I use comes with red, yellow, green, and blue, so I mixed blue and red to make purple. Your choice on if you’d rather make orange with red and yellow, or just do four colors.
Step 3: Pull apart five half-sheets of paper towels
Again, how many sheets you need will depend on how many cups/colors you’re choosing to use.
Step 4: Fold the paper towels in half and place in the cups
Start with an end cup and place a paper towel with half its body in one color and half in the other (the middle should be outside of the cup). Repeat until done! Every cup should have two paper towels, except the ends.
Step 5: Wait and watch the magic!
Timing of this experiment will depend on how much water you added and how much food coloring. The less water and more food coloring (or the thinner the paper towel), the quicker it’ll happen.
What will happen?
The colors will travel up the paper towel slowly and make a rainbow!
How does it work?
The colored water moves up the paper towels due to capillary action. The paper towel is made from fibers and water is attracted to those fibers and is able to travel through them against gravity.
The fibrous material acts as a capillary tube and helps pull the water upward. This is what helps water climb from a plant’s roots to the top of the tree.
What is capillary action?
Capillary action is the ability for a liquid to flow in a narrow space without an external force, and sometimes in spite of an external force, such as gravity. This is due to a combination of adhesion, cohesion, and surface tension.
Cohesion keeps the water molecules together and adhesion refers to the process in which water molecules are attracted to and stick to other materials.
Contact Brittany Van Voorhees at bvanvoorhe@wcnc.com and follow her on Facebook, Twitter and Instagram.