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  • Writer's pictureMelissa

How to Scare Pepper

Updated: Jun 2, 2021

In this activity you will make pepper grains dash away from your finger!


  • 1 plastic container

  • 1/8 teaspoon pepper (or 2 pepper packets from takeout)

  • bit of soap - a bar works great but hand soap or dish soap is fine too

  • dab of ketchup (or some other easy to find condiment)

  • 1 napkin

  • about 1 cup of water

*A Q-tip is a great substitute for a finger, for those who don't enjoy dirty hands.


1) Fill your plastic container about halfway with water, and place it on a flat surface.

2) Sprinkle the pepper over the top of your water.

3) What do you notice? Do the pepper grains stay in one place or spread out? Do they sink or float?

4) Pick a spot and touch the pepper grains with one finger. Does anything happen? Did any pepper stick to your finger?

5) For the next step, you will need your finger to be a little wet. Rub your wet finger on the bar of soap, or rub a bit of liquid soap onto your fingertip. Then touch the pepper floating on the water again.

6) What did you notice this time? Did the pepper stay where it was or dash away from your “magic” finger?

7) What do you think will happen if you rub a tiny bit of ketchup on your finger and touch the floating pepper? Will the pepper stay where it is or move away from your finger? Use the napkin to wipe the soap off your finger first, and then test the ketchup. What happened?

8) If your grownup says it is okay, test how “scared” pepper is of some other things around your house. Maybe a little dab of milk or juice or cooking oil? Maybe a teensy bit of toothpaste or shampoo? There are lots of possibilities, but make sure you ask a grownup before trying them out. You may need to sprinkle more pepper grains on top of your water first!

Here are a few things I tried: bar soap, olive oil, dishwasher tablet, sunscreen, shampoo.

If you test some of these things too, check to see if you get the same results (pepper grains scattered or did not scatter) that I did. That will tell you whether my results are reproducible. Reproducibility is very important in science. Results that cannot be reproduced may not be real results. They may be due to chance.

9) Cleanup: rinse the water and pepper down the drain


Water molecules like to stick together, like good friends holding hands. This creates something called “surface tension” on the top of the water in your container. When you sprinkle pepper on the water, the pepper grains are so light they do not disturb the surface tension of the water, so they float. When you touch the water with a soapy finger, the soap breaks the surface tension and the water molecules pull away from your soapy finger, taking the floating pepper grains along for the ride. When you test other things like ketchup or shampoo, you are testing to see if these substances break the surface tension of water or not. If they break the surface tension, the “scared” pepper grains will scatter away from your finger or drop to the bottom of the dish.

Click below to download a pdf of the How to Scare Pepper DIY science kit for easier printing.

scare pepper
Download PDF • 37KB

For this kit, I like to use a scrap of wax paper to wrap up the soap chip, and seal with masking tape.

Make messes, have fun and spread science joy!

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