What you need

• Five wooden toothpicks
• A small sponge
• A plate
• A little water

Instructions

1. Snap the toothpicks in half but don't break them fully
2. Arrange the toothpicks on the plate so they are spaced out with their broken ends forming a small circle
3. Carefully squeeze a drop of water into the middle. Make sure it touches the end of each toothpick

Results and Explanation

The toothpicks move. Just like synchronised swimmers! The water makes the wood expand, the broken ends press against each other and the toothpick opens out. The same thing happens to doors when it's humid - they swell and get jammed.

These experiments have not been specifically safety tested for home use but we believe them to be safe if the instructions are followed. Adult supervision or direction is recommended as appropriate. All experiments are carried out at your own risk.