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  • Writer's pictureJenna Granger

Soap & Pepper

Updated: Dec 22, 2020

A demonstration of the importance of hand washing amid the Coronavirus & an exploration into how soap works.

Grade Level:



Physical Science:

  • properties of matter

  • surface tension of water

Tools & Materials

  • Shallow bowl, plate, or pie tin

  • Water

  • Ground pepper flakes (to represent virus)

  • Dish soap

To Do & Notice

1. Set-Up:

  • In this experiment we will use ground pepper flakes to represent a virus (like Coronavirus) to demonstrate how hand washing helps protect us from viruses.

2. Question:

  • How does soap interact with water & pepper?

3. Make a Claim:

  • What do you think will happen when you combine soap with water and pepper? Will the materials stay still or will they move? Will all of the materials stick together or will they move apart?

4. Testing Ideas:

  • Fill the bowl, plate or pie pan with about one inch of water.

  • Sprinkle pepper flakes evenly across the surface of the water.

  • Test #1: With your unwashed hand, stick one finger into the middle of the water. Observe what happens. Lift your finger out of the water and take a look at your finger. Are there any pepper flakes on your finger? You should notice that the pepper flakes (virus) sticks to your finger.

  • Test #2: Lather your hands with dish soap. Poke one soapy finger into the center of the bowl. Make sure that your soapy finger goes beneath the surface of the water and touches the bottom of the bowl. Observe what happens. Did the pepper flakes move? Did they stick to your finger? You should have noticed that the pepper flakes (virus) are pushed away by the soap.

5. Analyze & Interpret Data:

  • How does soap interact with water & pepper? Most of the pepper flakes (virus) should have darted to the sides of the pan, and some of the flakes should have fallen to the bottom of the pan. It may have looked like the soap was chasing the pepper flakes away.

  • How do you think washing your hands might help protect you from viruses?

6. Communicate Findings:

  • Always remember to wash your hands with soap and remind your friends and family to do so as well. Share your results with SWEP by sending us photos or videos of your experiment. Post your photos on social media and tag us @sweptahoe on Instagram and/or to @swep4 on Facebook. Be sure to hashtag and follow #SWEPsnippets. If you cannot post directly yourself, send your photos or video to SWEP (

What’s Going On

Why does pepper float?

  • Pepper is hydrophobic which means that the water molecules are not attracted to the pepper. The pepper is very light and won’t be dissolved by the water. Water molecules line up and stick to each other creating a line of tension on the surface of the water that the pepper cannot break through.

Breaking it down with soap:

  • The soap is able to break through the surface tension of the water molecules and clean objects. Now that the soap has entered the bowl the pepper is no longer floating on top. The pepper flakes (virus) move with the water molecules as the surface tension is broken. The top layer of the water becomes broken by the soap and as those water molecules move, they carry the pepper flakes with them.

  • Want to know more about soap & how it works? Watch this sciency video to learn how lipophilic and hydrophilic reactions help remove dirt, grease and germs from your skin.

How does hand washing help keep us healthy?

  • The act of washing and scrubbing your hands under running water removes the germs from your hands and the soap helps increase the cleanliness by pulling unwanted materials (germs) off of the skin and into the water. Washing out hands and keeping them clean is one of the best ways to avoid sickness and spreading germs. When hands are contaminated with germs, those germs can be transferred from one person to another or by touching objects. Washing hands with soap and clean running water for 15 seconds (the same time as singing Happy Birthday) reduces the bacterial count by 90%. Adding another 15 seconds to your hand washing technique reduces a total of 99.9% of bacterial counts.


  • Video of Soap and Pepper experiment with another explanation of how & why it works.

  • Video to help you understand how to protect yourself from germs & perfect your hand washing technique.

Going Further

Take this experiment to the next level and try these follow up activities:

- Question: Do you think that soap is the only substance that can break down the water’s surface tension? What other substances might cause the water & pepper to react the same way as they did with the soap? What would happen if you used olive oil or hairspray instead of soap?

- Materials:

  • Olive oil

  • Hairspray

  • Water

  • Ground pepper flakes

  • Shallow bowl, plate, or pie tin

- Testing Ideas: Repeat the same set up process as the original experiment with soap, water, and pepper. Add about one inch of water onto a plate and then add the ground pepper flakes. This time you will be using olive oil and/or hairspray instead of dish soap. Dip your finger into olive oil and poke the water and pepper mixture with the oily finger. Observe what happens. Next, spray some hairspray onto your other finger and poke the water and pepper mixture. Does the same reaction take place? What is different? What is similar? Is the water’s surface tension broken?

Thank you to Excellence in Education and our many partners for supporting student's science, sustainability and outdoor learning experiences.

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