A substance that undergoes a physical change like melting is still the same substance is it true or false

Kc = 0.040 for the system below at 450oc. if a reaction is initiated with 0.40 mole of cl2 and 0.40 mole of pcl3 in a 2.0 liter container, what is the equilibrium concentration of cl2 in the same system? pcl5(g) ⇄ pcl3(g) + cl2(g)

The identities of substances are the same before and after which type of change

40dm3 of gas at 760 torr are heated from 5°c to 50°c what is the new volume