Polystyrene, also known as Plastic number 6, and commonly referred to as Styrofoam (in the same way some people refer to all tissues as Kleenex).  Technically, Styrofoam is a Dow Chemical-trademarked name for Extruded Polystyrene used for building insulation and floral foam.  So, the rest of the polystyrene family (CD cases, coffee cups, packing materials,…