Does it Float? Sink?

Last week my 7 year old and I were home with nothing to do, so we decided to test out which food items float and which sink.  It's a real simple experiment you can do with your kids as long as you have a jar, water, and something in the fridge.  I started out by briefly explaining density to her and said that objects more dense than water sink and those that are less dense float.  I let her grab food items and tell me what she thought would happen.  Then she tested it out.

She started with a cherry tomato, which quickly sank to the bottom.  It looks like an oval shaped egg yolk in this picture due to refraction (bending) of light through the water/glass/air transitions, but trust me, it's a tomato.  Then she tried a piece of bread, which floated, but then changed it to a wadded up piece of bread.  It sunk!  By smashing the bread into a tighter space, the density increases and becomes greater than that of water.  We tried several other food items too, including cheese!  

So try it out.  Let your kids choose what to drop in the water, but have them make a prediction of the outcome first.