Science & Discovery Projects
Easy
5 Minutes
Surface Tension Experiment
Bilal Şentürk
Maker
What You'll Need
- A shallow, wide bowl of clean water
- A pinch of ground black pepper or dried oregano
- Liquid dish soap
- A toothpick (or a clean fingertip)
- Tray or protective mat
Safety First!
- !Work on a stable, non-slip surface.
- !Supervise children at all times.
- !Keep soap away from eyes and mouth; rinse immediately if it contacts skin.
- !Clean up any spills right away to prevent slipping.
Let's Make It! Step-by-Step Guide
1
Prepare the Water
Step 1 of 3
The Science Behind It
Water molecules at the surface cling tightly to each other, forming a tension-filled “skin” that can support small, light objects. This phenomenon is called surface tension. When you introduce soap, its molecules wedge between the water molecules, weakening their bonds and collapsing the surface film. As the “skin” breaks, the floating pepper flakes lose their support and race toward the stronger tension at the bowl’s perimeter.
Helpful Tips
- Touch the soap only to the very center of the surface for the most dramatic effect.
- Try different soap brands or concentrations to see which breaks tension fastest.
- Use a clear bowl on a dark background to make the pepper movement easier to see.
- After the experiment, rinse the bowl with warm water to remove all soap residue.
Try These Variations!
- 1Alternative Powders: Float colored spices (turmeric, paprika) for a rainbow effect.
- 2Two-Point Release: Touch soap at two spots simultaneously and watch the pepper split in both directions.
- 3Temperature Test: Repeat with hot vs. cold water to see how temperature affects surface tension.
- 4Vinegar & Oil: Compare the effect of dish soap to vinegar or cooking oil on the pepper’s behavior.