[NOTES/SM-01001] Thermodynamic Coodinates

Thermodynamic coordinates:
Thermodynamics uses a macroscopic description in terms of a few macroscopic coordinates. For example, mixture of gases can be described by

Examples of thermodynamic systems
(1) Gases Coordinates $P,V$  $ dW=PdV $ 
(2) String $dW=Tdl$
In general work done will have a form  $dW=XdY$

Combining Ist and IInd laws makes them very powerful because $dQ,dW$ are in exact differentials and depend on path taken.
But $dS, dU, dY$ depend only on the state of a system and do not depend on path or process relating different states.