Wednesday, June 24, 2015

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

I'm not sure my oldest son uses soap every time he showers. And I've seen our youngest son put soap on one hand and then instead of rubbing them together, stick the soapy hand immediately under the running water. Hopefully this simple, yet fun, experiment has convinced them of the merits of soap.

The experiment is meant to simulate how soap helps to get rid of germs.

What You Need
plate (or saucer) with a raised edge
ground black pepper
dishwashing liquid (we used Ms. Meyer's)

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 peppers represent germs.

Now squirt a dot of dishwashing liquid onto one of your index fingers. Rub it all around, completely covering the tip of the finger.

Lastly, put your soap-covered finger into the middle of the peppered water.

Be amazed. The soap seems to repel the pepper (aka the "germs").

Why it Works
This activity was discovered on Fantastic Fun and Learning. As explained by Shaunna, "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."

What to Read
You can't go wrong with a Magic School Bus Book. We have rediscovered our love for all things Frizzle this summer. This book complemented the activity beautifully!


  1. amazing tips!! i will try it soon thank you so much

  2. Soap does NOT REPEL germs. This is the most ridiculous explanation of how soap works I've ever seen.

  3. for a child it's a good motivator to get them washing their hands. didn't realize a 6 year old should understand anionic surfactants.

  4. Well it works like you said, but I thought that soap was killing the germs and not repel?

    1. Soap does not kill germs either, but the activity makes the point that soap is helpful in ridding the hands of things you do not want on them. In time they can learn the rest of it.

  5. It's meant to demonstrate to small children. Dip your finger in it without soap, nothing happens. It's a visual aid to encourage hand washing and soap usage during the process... unless you plan on teaching four year olds about chemical reactions

  6. My daughter is a Childminder in England; her 'mindies' don't like washing their hands and don't understand why they should. This seems like a very good way of explaining the importance of hand washing.