H= U+PV entalpia, funzione di stato, poiche' definita in termini di funzioni di stato.
QP = ∆H se
L'indice P in QP serve a ricordare che questa relazione vale solo se la trasformazione avviene a pressione costante.
dim: p=k Q = P∆V + ∆U = ∆PV + ∆U = ∆(PV + U)
Siccome U e' definita a meno di una costante, cosi' e' per H.
H= U+PV dH= dU+dPV+PdV
caso p=k dp=0 Vdp=0 dH= dU+PdV = dU+δW = δQ
|I propose to name the quantity S the entropy of the system, after the Greek word [τροπη trope], the transformation. I have deliberately chosen the word entropy to be as similar as possible to the word energy: the two quantities to be named by these words are so closely related in physical significance that a certain similarity in their names appears to be appropriate.
Although Clausius did not specify why he chose the symbol "S" to represent entropy, it is arguable that Clausius chose "S" in honor of Sadi Carnot, to whose 1824 article Clausius devoted over 15 years of work and research. On the first page of his original 1850 article "On the Motive Power of Heat, and on the Laws which can be Deduced from it for the Theory of Heat", Clausius calls Carnot the most important of the researchers in the theory of heat.