Dancing Raisins!

We looked at floating and sinking this week.  Room 20 had some great ideas about why some things float, and some things sink.  We discussed about heavy and light objects, the shape and size, introducing the word 'density.'  We had some raisins, half the class thought they would sink because raisins are dense, half thought they would float because raisins are little and light.

First, we half filled a jar with water.  We put the raisins in and they sunk.  Raisins are denser than water.  Next we tipped the water out and half filled a jar with soda.  Initially the raisins sunk, but then they started bouncing!!  They went up and down in the jar.  Why was that?

The raisins have lots of little creases in them.  Bubbles get trapped on the raisin, when enough bubbles get trapped the combined raisin/bubbles become less dense than water and the raisin floats up.  When it gets to the surface, the bubbles pop and the raisin sinks back down again, as it has become more dense than the water again.

Think like a scientist...I wonder??
Will vinegar and baking soda work the same?
Will a different soda like Fanta or Coke work?
Does temperature change the results?