We have been studying how the earth is changing and wondering about the forces that move the huge plates on top of the mantle. In order to understand convection currents, (which is one of the mechanisms for this) we have been thinking about what happens to matter when it is heated and cooled. I showed two demonstrations, The bottle and the balloon and the Egg in a flask egg-suck video to demonstrate that air expands when heated to become less dense and contracts when cooled to become more dense. I showed two other demonstrations to show that matter that is less dense rises/floats on matter that is more dense. The immiscible liquids jar was one and the squished pan and regular pan in a tank were the other. Ask your students to explain each of these to you!
