As you and your child observed the raisins, you should have noticed that they initially sank to the bottom of the glass. That’s due to their density, which is greater than that of liquid. But because raisins have a rough, dented surface, they are filled with air pockets. These air pockets attract the carbon dioxide gas in the liquid, creating the little bubbles you should have observed on the surface of the raisins. The carbon dioxide bubbles increase the volume of each raisin without raising its mass. When the volume increases and the mass does not, the density of the raisins is lowered. The raisins are now less than the surrounding fluid, so they rise to the surface. At the surface, the carbon dioxide bubbles pop and the raisins’ density changes again. That’s why they sink again. The whole process is repeated, making it look as though the raisins are dancing. Try putting the raisins in a jar that has a replaceable lid or directly into a bottle of soda. What happens to the raisins when you put the lid or cap back on? What happens when you take it back off?