This is a classic and very fun science experiment that demonstrates the incredible power of water surface tension. It’s time to learn something new and have some fun with this Dancing Pepper and Soap Experiment.
Find more Fun Water Experiments here!
I love how simple and basic this science experiment is and yet the science behind it is still fascinating for both kids and adults!
Dancing Pepper and Soap Experiment
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Soap and Pepper Science Experiment
- Fill a bowl with water.
- Shake some pepper onto the top of the water in the bowl.
- Put some soap on a cotton swab.
- Touch the soapy cotton swab to the center of the water.
- Watch as the pepper dances and races to the edge of the bowl!
Step 1: Pour Water into a Bowl
This first step is super easy and all you need to do is pour some water into a medium to large-sized bowl.
The larger your bowl is, the more visual and dramatic the end result of this dancing pepper and soap experiment will be!
Step 2: Sprinkle Some Black Pepper into the Bowl
Now just sprinkle a generous amount of ground black pepper into the bowl of water.
You want to put enough pepper into the water that there is a nice even layer on the surface of the water, but not so much that the pepper clumps together and sinks in the water.
Step 3: Rub Some Soap onto a Cotton Swab
You need to be very careful in this step not to let any soap drop into the water prematurely or may trigger the pepper to start dancing around before you are ready!
Full Disclosure: I accidentally let a drop of soap fall into the side of the bowl when trying to rub some on a cotton swab and it pushed all the pepper to the other side! Oopsie!
The best way to avoid my mistake it to apply the soap to the cotton swab off to the side of the bowl of water and pepper. That way if you drip a little soap it will fall on the table and not into the water!
Step 4: Stick the Soapy Swab into the Middle of the Water
Once you have a little drop of soap on the end of the cotton swab, its about time to have some fun!
Go ahead and slowly lower the soapy tip of your cotton swab towards the center of the bowl until it touches the surface of the water.
Step 5: Watch the Pepper Race to the Edge
It’s time for the moment we are all been waiting for…drumroll please!
When the soap-covered tip of the cotton swab touches the surface of the water you will see a dazzling, dancing display!
The pepper quickly races away from the soap in the center of the bowl and moves to the sides of the bowl!
Pretty cool right!!!? But why does this happen? Let’s dive into the magical science behind what makes the pepper dance in the water.
Why is Pepper Afraid of Soap?
Although it appears as though the pepper is afraid of the soap, it’s actually the water moving away from the soap that pushes the pepper to the sides of the bowl.
In this dancing pepper and soap experiment we learn about hydrophobic (repels water) and hydrophilic (attracted to water) molecules.
Pepper molecules are hydrophobic and do not attract water. This helps the pepper to float on the surface of the water until the surface tension is broken by the soap.
For another cool way to visualize the reactions between hydrophobic and hydrophilic substances check out this Color Changing Milk Experiment.
How Does Soap Break Surface Tension?
The other important factor to making this dancing pepper and soap experiment is the ability for the soap to break up the surface tension of the water.
Soap molecules are very unique because one end is polar hydrophilic (water loving) and the other end is non-polar hydrophobic (water hating).
This unique design of soap molecules having a polar and non-polar end gives them the ability to break down the surface tension on the water.
As the surface tension is broken, the water molecules still want to stick together so they move away from the soap as fast as they can while pushing the soap to the sides of the bowl with them!
Try Some Other Cleaning Products:
For a fun little twist on this experiment you can try substituting other household cleaners or even toothpaste instead of soap!
These cleaners are also designed to break down surface tension and should make the pepper dance too!
PIN THIS EXPERIMENT FOR LATER