20 BREAKDOWN OF POLYMERS Usually the smallest molecules are gaseous or liquid at room temperature and the large molecules are solids Perspex and polystyrene are solid polymers which can be broken down to smaller molecules by heat Put pieces of Perspex or polystyrene in a hard glass testtube Connect a delivery tube as 297 From large molecules to small molecules A Perspex or polystyrene B receiving tube c cold water D a liquid collects The collecting testtube must be cooled thoroughly with cold water as the fumes are harmful Gently heat the testtube containing the Perspex The polymer will melt and give off vapours which are collected in the receiving tube Heating must be carefully controlled to enable all the fumes to be condensed in the receiving tube A liquid is obtained This suggests that the polymer has been broken down by heat to smaller molecules The liquid does not return to the solid state unless a catalyst is used The specific catalysts are not usually available in school laboratories