Moving Pepper in Water Experiment

The "Moving Pepper in Water" science experiment is a very cool experiment you can do with your kids in just a few minutes that requires materials you most likely already have in your house.  You need pepper (flakes from a pepper shaker), liquid dish soap, a Q-tip, and water.  That's it!  Begin by filling up a container of water.  We used a standard baking dish.  Spread several flakes of pepper on the surface of the water.  On a separate plate, spread a tiny amount of liquid dish soap.  Spread a little bit of the dish soap on the end of a Q-tip.  Then carefully place the soap soaked end of the Q-tip in the water and observe.  Here's the video I took of my 5 and 9 year old doing this experiment.

Very cool!  Notice how the pepper flakes quickly move to the edges of dish, away from the Q-tip?  Awesome!  Now, the important part.  Why does this happen?  Why do the pepper flakes move?  The pepper flakes are sitting on the surface of the water and water has a certain amount of surface tension.  The surface tension of liquid dish soap differs.   It is less than that of water.  Once the soap makes contact with the water, the pepper flakes, attached to the surface of water with greater surface tension rush away from the soap toward the edges of the dish.  Super cool!  Try it at home.  If your kids are like mine, they'll be amazed and want to try it several times!