From start to finish, this experiment will take less than 3 minutes, but the end result will likely cause your kids to want to try it again and again. Bonus if you make the “Zoom” noise the first time doing the experiment!
A demonstration video, a supplies list, and printable detailed instructions included.
- Shallow Dish
- Dish Soap
Step 1 – Begin by placing a drop of dish soap onto a plate. Then set the plate aside.
Step 2 – Next, take a shallow dish and pour water on it until the entire bottom of the dish is covered.
Step 3 – Sprinkle a tablespoon of pepper on the top of the water.
Step 4 – Dip one finger into the dish soap. What do you think will happen if you touch the pepper?
Step 5 – Place the finger you dipped in the soap in the middle of the dish with the water and pepper. Watch what happens…Zoom! Write down your observations. What happened to the pepper when you touched it. Do you know why?
Find out the answer in the how does this experiment work section below.
Water is an amazing substance with many unique properties. This experiment shows one of water’s unique properties – surface tension. Surface tension is the pull (or attraction) among water molecules that brings the molecules on the surface closer together. Water is a polar molecule, meaning that one end of a water molecule has a slight positive charge and the other end of a water molecule has a slight negative charge. This results in water molecules being attracted to one another. This attraction of water molecules is what is responsible for the surface tension of water. The polar molecules of the water pull on each other forming a tightness (or almost skin) on the top of the water.
When you sprinkled the pepper on the water, most (if not all) of it stayed floating on the surface of the water. This is because the pepper flakes are so light that they do not disturb the surface tension of the water and they stay floating on top of the water.
When you add a little dish soap, the surface tension of the water is disturbed. The soap “breaks” the surface tension of the water because one end of a soap molecule is hydrophobic (meaning “water-fearing”). As the soap molecules push away from the water molecules, they disturb the bonds holding the water molecules together. When this happens, the pepper moves or runs with the water molecules away from the center of the plate.
More Cool Science Experiments
If you liked this experiment, check out these other experiments with common food items:
- The Floating Egg – Eggs naturally sink in water, but we made them float
- Why Does the Heavier Orange Float? – This experiment show us that the weight of an object isn’t the only indicator to use to determine if it will sink or float.
- Dancing Raisins – Watch the Raisins dance around in the glass.
- Put a Straw Through a Potato – Did you know you can easily put a straw through a raw potato?
- Bouncing Egg – Make a raw egg bounce…just don’t drop it from too high in the air!
I hope you enjoyed the experiment. Here are some printable instructions: