Twist on sink and float (always something new)

At one of my library activities this summer, I invited kids to sink a marshmallow by squashing it to make it denser than the water--I try to explain to them that to make something more dense you either have to make it smaller or make it heavier. Then I invite them to experiment with water displacement and float a piece of taffy by shaping it into a bowl. One of my students made the should-have-been-obvious leap and wrapped the taffy around the marshmallow to make it float!