In the Sorting Salt and Pepper video we saw that we could mix salt and pepper into a pile and then separate them easily by using the static charge on a balloon. That is one way to separate salt and pepper, but there are many others. How many can you think of? Don't read any more until you have spent some time thinking of as many different ways as you can.
In part one, I left you with a challenge. We put a little sand into a glass of water and stirred it. Instead of moving to the outside edge, as we might expect, the sand gathered in the center of the glass. I left you with the challenge of telling me why.
Congratulations! Several of you got the right answer, and several more got it at least partially right.
I developed this activity while producing some science videos to go with a science textbook. They wanted students to be able to measure potential and kinetic energy, using everyday objects. Thanks to the abundance of cell phones, this is an easy way to do that.