Dancing Raisins

Initially some of the raisins sunk to the bottom.

Air pockets on the surface of the raisins attracted the carbon dioxide gas in the liquid, which covered the surface of the raisins.

When the bubbles stuck to the rough surface of the raisins, they became buoyant and rose to the surface.

The carbon dioxide bubbles popped at the top and the raisins' density changed again. That’s why they sunk again. 

 After leaving them in the soda overnight, these raisins became suspended in the middle of the liquid.

Look at the difference in size.  The first one is the dried raisin.  The second one is what it looked like after sitting in the liquid overnight.

When we looked at each one under the microscope we could see all the air pockets in the first one.  The second one was a little smoother and the air pockets had gone.