Capillary Action I DIY Science Experiment for Kids

header image showing 7 cups with rainbow water colours

C for Capillary

header image showing 7 cups with rainbow water colours

Bet, this capillary action experiment is going to be fun to kids and adults alike!

Tips to introduce

  • Be as creative as you can in introducing the concept to children! First, you can begin talking about how leaves and stems take in water when we water the soil?
  • Initially, children tend to understand the principle of capillary action when they observe rather than discussing. So, plunge straight into the experiment.
  • When you think they are ready for this experiment, write down on a sheet the things you’ll need and direct them to collect it all at one place. You can get food colors from super markets. If you can reuse old sketch pen ink fillers (check the video for how we’ve done for the blue color). Fix a time and place and let them know you’ll meet them there, then.
  • When you are at the experiment venue, explain to them what you are going to do without revealing what you are likely to observe.
  • Set it up and let them observe what happens!
  • Allow them to explain their inference if it is of their interest. Don’t push or annoyingly try to bring explanations out of them. Most importantly, enjoy if their rationales are not logical or correct. They are still children, and being right is not as important as being interested to observe and have fun with science. And then follow their cues to build on.

Things you’ll need

pictures of things needed

How do you do it?

1. Fold the paper towels into thick strips. We will need six of these.

2. Arrange 7 glass/transparent plastic cups. Half-fill alternative cups with water, starting from the ends. So, you should have 4 water-filled cups and 3 empty cups.

3. Add red food color to the two cups at the ends. Add yellow and blue colors one to each of the remaining two water-filled cups in the middle. Stir well.

Image showing paper towels placed in the cups

4. Place the folded paper towels in the cups such that each connects the adjacent cups.

5. Time to observe!

image showing colors moving through the paper towel using capillary action


The Science behind

Unless we placed a paper or cotton accidentally in a liquid and left the open end to drip, we might not have observed capillary action. We don’t get to see it happening inside plants either. However, the liquid raising through the paper towel is just enough for children to understand what happens. If they are a little older, you can discuss about cohesive and adhesive forces.

The three basic colors – red, yellow, and blue – move through the paper towels by capillary action and begin to drip into the adjacent empty cups. As the colored waters mix in the empty cups, they form the intermediary colors – orange, green, and purple, giving an amusing rainbow colored appearance.

Share your experience

Was the capillary action experiment helpful? Was it fun? Did you try? Did it work? Or didn’t? Leave a word in the comment section. I would love to hear!

Here’s the full list of DIY Science Experiments in this series:

A for Air – Does Air has Weight?

B for Buoyancy – Can Egg float on Salt Water?

C for Capillary action – Rainbow Walking

D for Density – 3 Layer Density Experiment

E for Earth & Moon – Why does the Moon change its shape?: Phases of the Moon

F for Fire – Does Fire need Oxygen to Burn?

G for Gravity – Defying Gravity

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