The lattice constants of orthorhombic polyethylene have been determined as a function of temperature: † lattice constants, å t, k abc 4 7.121 4.851 2.548 77 7.155 4.899 2.5473 293 7.399 4.946 2.543 303 7.414 4.942 2.5473 (a) what is the theoretical volume coefficient of expansion of 100% crystalline polyethylene? (the volume coefficient of expansion is given by where the change in volume v is measured as a function of temperature t at constant pressure p.) (b) why are the c-axis lattice constants substantially independent of the temperature?