A unit mass of a substance undergoes an irreversible process from state 1 to state 2 while gaining heat from temperature T in the amount of q. If the entropy of the substance is s1 at state 1, and s2 atthesurroundingsatstate2,the entropy change of the substance As during this process is \Delta ss 2-s_{1} \Delta s=52-51 \Delta s=s_{2}-s_{1}+q / T