Today, Miss Magoo is going to show you how to do a pepper and soap experiment! It’s a simple, cheap experiment that demonstrates how surface tension works.
I love how simple this experiment is. It doesn’t require any prep time for the parent.
If you’re wanting to conduct this as a real experiment and not just for fun, don’t forget to go through the scientific method. We use the same method at home that we use in our class at Classical Conversations, so it includes purpose, hypothesis, materials, procedure, results and conclusion. It’s a nice and simple version of the scientific method that works well for young children.
Purpose: To demonstrate surface tension of water.
Hypothesis: Have everyone involved come up with a hypothesis.
- Pie plate
- Dish soap
Watch in Youtube: Pepper and Soap Experiment
In case you aren’t a movie watcher (I’m not much of one, so I completely understand) here are the directions (also known as the procedure):
- Pour water into the pie plate. Maybe 1/2 an inch deep.
- Sprinkle pepper over the water.
- Dip a toothpick in the dish soap– it doesn’t take much.
- Poke the toothpick near the center of the pepper and watch the pepper “run away.”
Results: Record what happened when you placed the soapy toothpick in the pepper.
Conclusion: We can see how surface tension in the water works when we touch the soapy toothpick to the peppery water. Pepper is hydrophobic, meaning it repels water. Because there is surface tension on the top of the water, the pepper floats on the top of the water and doesn’t soak up any of the water.
Soap breaks down the surface tension of the water, so as we put the soapy toothpick in the midst of the peppery water, we can see the water pull away from the toothpick, in its attempt to keep its surface tension. When it does this, it carries the pepper with it, causing it to look like the pepper is running away from the toothpick.
I hope you enjoyed this fun and simple pepper and soap experiment Miss Magoo shared today!