Why these state functions are negative for solid water at equilibrium?
I share as an example the table from Termodinamica Cengel 7th Edición.
Update: I know that these functions can't be negative. But is there any reason to be negative in the table?
The true entropy can never be negative. By Boltzmann's relation S = k ln OMEGA it can be at minimum zero, if OMEGA, the number of accessible microstates or quantum states, is one. However, many tables arbitrarily assign a zero value for the entropy corresponding to, for example, a given temperature such as 0 degrees C. Then the entropy entries in the table for subfreezing temperatures will have negative values. But these values are negative only with respect to the arbitrarily assigned zero value corresponding to 0 degrees C in the table. Similarly, tables may arbitrarily assign a zero value for the internal energy and enthalpy corresponding to, say, 0 degrees C. Of course the true internal energy can never be negative, in total it equals mc^2 where m is the mass of the sample --- and similarly for enthalpy except that PdV work exchange with the surrounding atmosphere must then be included.
Dear Jose, Jack Denur is right in his answer. Please look in a textbook of thermodynamics to understand the background of the so-called potential functions. In thermodynamics the flow into a system is defined positive. Consequently the internal energy and enthalpy must increase with temperature. To understand the values in your table you should read the description and explanations given in your handbook.
By the way, I can't see any negative state function in your table. Only the difference between the two following columns is negative, the second and third column is always positive and increases with increasing temperature, as it should be! Regards, Gunther Höhne.
The thermodynamic Entropy is non negative property (S≥0). According to third law thermodynamic entropy can be either positive or zero. It cannot be negative. However Entropy change dS can be negative, zero or positive.
Comparative study of entropy and information change in closed and open thermodynamic systems
Marko Popovic
Full-text Article · Nov 2014 · Thermochimica Acta
Entropy: A concept that is not a physical quantity
https://www.researchgate.net/publication/230554936_Entropy_A_concept_that_is_not_a_physical_quantity
Thank you all. I understood perfectly that the temperature of 0 ° C is the reference state.
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