The Styrofoam cup. It seems like a simple unitasker, one that holds liquids and is a good insulator. Why is it a good insulator and so light? Styrofoam is the the brand name that Dow Chemical uses for its version of polystyrene. Polystyrene is a polymer, which is a substance that is made up of repeated units, monomers, bonded together. What makes Styrofoam special is the process in which it is made. During the process, gas is blown into the polystyrene causing the material to be mostly empty space. The Styrofoam is very low in density becuase the mass of the polystyrene is contained in a larger area. It is a good insulator because the air spaces that make up the foam deters heat energy flow. The above video demo shows what happens when the polystyrene is dissolved in acetone. The polystyrene structure basically collapses and condenses, leaving a hardened, more dense mass.