Rainbow Toothpick Star - Science Experiment for kids

This Rainbow Toothpick Star is a super simple and easy science experiment. It is a fun way to learn about capillary action. The required materials can be found in every home.

Age: 3+           Time: <10min

 Safety 

1. Be careful, kids may swallow the toothpick.
2. Adult supervision.

 Materials List 

• Toothpicks
• Water
• Drinking straw
• Colored pencil

 Instruction 

Step 1/3 – Paint the five toothpicks into whatever colors you like. Bend the toothpicks at the middle but not break it into two pieces.

Step 2/3 – When you have 5 bent toothpicks, arranged them on the plate with the middles (the bent parts) of each touching one by one to form a closed star shape.


Step 3/3 – then use a straw to load some water and drop the water in the middle of the star. The toothpick will slowly expand outward into the shape of the star.

 Troubleshooting 

Did the toothpick not expand?
—The toothpick cannot be broken into two pieces when bending the toothpick. The bending angle should not be too small.

 Scientific Description 

The toothpicks are made of dried wood. When you break the toothpick, you stretch and compress some parts of the wood fibers inside the toothpick. When you drop water in the middle of the closed star formation, The dry wood fibers in each broken toothpick absorb water causing the toothpick to swell and expand to straighten itself. Capillary action is the ability of a liquid rising up and defying gravity in a narrow room. There are many small rooms in the wood fiber. This is what makes the pointed ends of the toothpicks push against each other, making the star to open.

 Extensions 

You can add hot water and cold water to see if they have different results. you can add some liquid besides water, like milk, oil, cola and etc to see if they have different results.
The experiment Rainbow Walking Water Science Activity applies the same principle.