Sprinkle some pepper in water and make it dance across the surface. Explore surface tension of water when you try this fun pepper and soap experiment with the kids. We are always on the hunt for simple science experiments and this one is just super fun and easy!
Pepper and Soap Experiment
Investigate why pepper moves away from soap in a bowl of water!
Recomemded Grave Level: K-3. It’s simple to set up, visually engaging, and easy to understand for younger students, making it perfect for introducing basic science concepts like surface tension and cause-and-effect.
For older students, grades 4-5, you could expand the experiment to discuss surface tension more in-depth or introduce variables like comparing different types of liquids (soapy water vs. plain water) to create more scientific inquiry opportunities.
Supplies:
- Bowl of water
- Ground pepper
- Dish soap
- Toothpick
Set Up The Pepper Soap Experiment
Watch the video:
STEP 1: Sprinkle pepper into a bowl of water.
STEP 2: Dip your toothpick into dish soap.
STEP 3: Gently touch the pepper in the middle of the bowl and watch the magic happen!
How Does It Work?
Surface Tension
Surface tension exists in water because water molecules stick to each other. This tension is so strong that when you first sprinkle pepper onto the water, it sits on top of the water instead of sinking into it.
Why does pepper scatter when you add soap? When soap is added to the water, it breaks the surface tension in that area. That makes the water molecules close to your finger pull away, carrying the pepper along with them.
💡 Learn more about surface tension here and try more surface tension experiments.
The Measurement of Surface Tension
Famous scientist, Agnes Pockels discovered the science of surface tension of fluids simply doing the dishes in her own kitchen.
Despite her lack of formal training, Pockels was able to measure the surface tension of water by designing an apparatus known as the Pockels trough. This was a key instrument in the new discipline of surface science.
In 1891, Pockels published her first paper, “Surface Tension,” on her measurements in the journal Nature.
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