Materials
- 5 matchsticks or wooden toothpicks
- Flat, non-absorbent surface (plate or petri dish)
- Dropper or straw
- Water
Instructions
- Carefully bend each matchstick in half. Do not break it completely. The wood should still be hinged.
- Arrange the bent matchsticks on the flat surface in a small circle. The open ends of each V-shape should touch the next one, forming a closed shape in the center.
- Use a dropper or straw to place a few drops of water directly into the center of the formation.
- Make sure the water touches the bent section of each matchstick.
- What you will observe: Within seconds to a minute, the matchsticks begin to move. The bent arms slowly push away from each other, opening up and forming a clear, five-pointed star shape.
What’s going on?
- This experiment demonstrates capillary action and surface tension.
- The matchsticks are dry at first, so the bent wood stays tightly folded. When water is added, it is pulled into the tiny spaces in the wood by capillary action.
- As the wood absorbs water, it swells slightly. This swelling causes each bent matchstick to straighten. Because all the matchsticks are connected in a circle, they push against each other as they open.
- Surface tension holds the water together and helps the water spread evenly to each matchstick, allowing the movement to happen smoothly and at the same time.
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