The TS Diagram :
We only consider pure substances
Two-phase envelope, similar to PV Diagram
Subcooled or compressed liquids have lower entropy than saturated liquids
Superheated vapors have higher entropy than saturated vapors
The entropy of a saturated vapor-liquid mixture lies below the entropy of the saturated vapor (at the same T & P) and above the entropy of the saturated liquid at the same T & P.