For each of the systems below:
i) identify the nature of the walls that separate the system from the surroundings
ii) identify the baths that represent the effects of the surroundings on the system.
iii) identify the variables that make up the thermodynamic state space of the system Example: An uncapped thermos bottle containing coffee. By some means (an insulated piston, insulated saran wrap, magic,...) both evaporation and heat flow from the open cap are prevented.

Walls: Insulating, volume-change-allowing, impermeable
Baths: Pressure bath only. (Heat can’t flow, so no thermal bath. Molecules can’t flow, so no chemical potential baths.)
Variables: S (insulating walls, no heat flow), P (atmosphere is a pressure bath), mole numbers for chemical components of the coffee solution (impermeable walls)

a) A closed thermos bottle containing coffee.
b) A closed glass beaker containing an aqueous buffer solution, sitting on a lab bench.
c) An open glass beaker containing a sodium chloride solution in water, sitting on a table top. As with the coffee example, evaporation from the open top is somehow prevented (or just ignored for present purposes).
d) A dialysis bag containing a protein solution, in a large beaker of pure buffer solution.