Here is the Raising Raisins experiment from "Rainy Day Play" that I listed previously as part of our Food Theme of the Week
I had never done this experiment before now. We didn't have seltzer water or club soda so I used 7UP instead. It seemed to work just as well since it is carbonated.
My kids just stared and stared at the raisins in amazement. I have to say, it was pretty cool. We also went ahead and ate the rest of the raisins and 7UP that we didn't use as we watched.