Why You Need to Use Soap (a Germs Simulation Experiment)

This week our Independence class began a new unit on Personal Hygiene. To start things off we discussed the importance of using soap and did a little experiment to demonstrate just how powerful soap can be against germs!


What You Need

plate (or saucer) with a raised edge


ground black pepper

dishwashing liquid

What to Do

Pour water onto the plate. You should use enough water to cover the whole bottom of the plate.

Sprinkle several pinches of ground black pepper onto the water. Explain that these specks of pepper represent germs.

After our chat I told them we were going to learn about how soap makes germs scatter, and I asked them to sprinkle some pepper into our bowl. (Don’t add too much or the demonstration will not work as well.) They observed how the pepper floats on the surface of our water, and I told them that was like germs on the surface of our skin.


For the next step I asked them to skip using soap and just stick their finger in the water. We found that skipping soap was a mistake, as our fingers were still covered in ‘germs’. Ew!


Then we covered one finger with dish soap.


Now for the big moment! And it’s a fast one, so make sure everyone is watching. Stick that finger into the water in the center of the bowl if possible. And POOF! Those “germs” scatter to the edge of the bowl. “It was like magic!” one of the participants said.

It was quick, but powerful and participants loved that moment. Afterward we talked about how the soap helps repel the germs and what we can learn from this demonstration. Everyone agreed that when washing hands and showering we should all definitely be using soap!


Why it works?

We ended things with a short discussion on why this works. Basically the demonstration has more to do with the soap and water. The pepper just allows us to actually see what is happening. When soap is added to the water it lowers the surface tension of the water causing the water molecules on the surface to “scatter” or pull away from the point where you added the soap.

This was such a great experiential learning moment for the participants! Before cleaning up, they enjoyed a little sensory time with the pepper water.

Melissa Burton


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