Make an Exploding Pepper Ring
In this simple science experiment, kids make pepper explode into a ring on the surface of water while exploring surface tension.
Simple explanation: Water molecules are "hugging" the pepper and holding it in place. This is called "surface tension." By adding the drop of soap, the "hug" is broken and the pepper zooms outward.
Detailed explanation: Water molecules form strong bonds, creating strong surface tension. But when soap is added, the soap molecules break up the bonds between the water molecules. As the water molecules break apart, you can see them carrying the flakes of pepper with them.
- Ground pepper - 1/8 teaspoon per student
- Dish soap - drop of this item per student
- Toothpick, straw or similar - 1 of this item per student
Fill bowl about 2/4 full with water. Sprinkle pepper onto the surface of the water. Ideally, the pepper should form a thin layer across the center.
Dip the toothpick or straw into the dish soap, then poke the wet end into the center of the layer of pepper floating on the water. The pepper will immediately shoot outward in a ring to the outside of the bowl.
To repeat, you'll need to rinse the bowl and add fresh water. If there is any soap residue in the bowl, the surface tension will already be diminished, making the effect of adding the soap far less dramatic.
This experiment also works well with two toothpicks (place them close together in the center of the bowl, then place a drop of soap between them and watch them zoom apart), or anything else small and light that floats (glitter, apple seeds, etc.)