[A&W]

is probably one of the best and most interesting ways to teach matter. I do many of the things the other posters have done and they're wonderful lessons. You might even consider making butter with "whipping cream". It's always fun to watch kids just amazed at how this liquid becomes butter right before their eyes. Don't forget to make a loaf of bread as well, I use a bread maker. The kids think it's cool to place all these separate ingredients and watch the bread materialize by the end of the day. The bread also goes very well with the butter you made earlier.