The entropy of a substance increases with its molecular weight and complexity and with temperature. The entropy also increases as the pressure or concentration becomes smaller.

Why does pressure affect entropy?

For example in a closed system (gases are ideal), if P increases and T=constant, you know that Volume must decrease. If V decreases then there is less space to explore and Entropy decreases. If P decreases, V has increased, and entropy has increased at constant T.

How does pressure affect enthalpy and entropy?

Enthalpy is the heat content of a system as a function of entropy and pressure. As the pressure increases ( ΔP>0 ), so does enthalpy, and vice versa. ... Enthalpy can still exist even at constant pressure; that describes the enthalpy of vaporization or fusion.