To begin, I made a very simple chart. Since my kids aren't reading yet, I drew containers of water (you could totally tell that's what they were, right? Right??) in the predictions and results columns that they could mark.
I put a different kind of fun size candy bar in each space in the first column. I didn't tape them down because I wanted the kids to be able to pick each up while they were making their predictions.
If the kids thought the candy bar was going to float, they marked the water at the top of the glass. If they thought the candy bar would sink, they marked the bottom of the glass. My five year old guessed that the bigger candy bars would sink and the smaller ones would float (makes sense to me).
My three year old hedged her bets by coloring in the entire glass.
|She'd color the whole world pink if she could.|
Twix - sank
3 Musketeers - floated
Kit Kat - floated
Snickers - sank
Milky Way - sank
Afterward, they did some of their own experiments by cutting the candy bars, putting them all in at the same time, stirring like crazy, and just generally making a mess.
The Science: Anything more dense than water (like sugar) will sink, while things that are less dense than water will float. The Kit Kat and 3 Musketeers have a lot of air in them.
Other fun ways to learn about science using candy:
Balloon Experiments with Candy from Learn~Play~Imagine
Balancing with M&M's from Inspiration Laboratories
Candy Corn Catapults from Frugal Fun for Boys
Exploding Peep Geysers from Housing a Forest