Just in case the children needed any more guidance for handwashing tips....(they'll be sick of us telling them!), this is a fun science experiment that my daughter told me about which demonstrates the impact of using soap to wash our hands. Have fun!
You only need a few common kitchen ingredients to perform this science magic trick.
If you are doing this as a "trick" then you might have one finger that is clean and another finger that you dipped in detergent before performing the trick. You could use a spoon or chopstick if you don't want a soapy finger.
When you add detergent to water the surface tension of the water is lowered. Water normally bulges up a bit, like what you see when you look at a water drop. When the surface tension is lowered, the water wants to spread out. As the water flattens on the dish, the pepper that is floating on top of the water is carried to the outer edge of the plate as if by magic.