Styropyro shows a classic demonstration of "The Vanishing Cup" experiment. Things you will need: a container, slightly larger than the Styrofoam cup, acetone and a Styrofoam cup. Place the container on a flat surface and fill it up with an acetone. Get the Styrofoam cup and Carefully place it inside the container. Watch the Styrofoam cup slowly shrinks as it touches the acetone. After a while. the Styrofoam cup turns into liquid form. Notice how much of the Styrofoam cup is left after it shrinks. Styrofoam is mostly air so when a small amount of plastic dissolves, the cup shrinks and turns into liquid form.