ABSTRACT
However, according to the phase rule (Section 1.12), specifying any two properties of a pure substance fixes all properties. Nonetheless, the EOS in the form
p
(
T,V
), for example, gives no hint about the functions
u
(
T,v
),
s
(
T,v
), or of the remaining auxilliary properties
h
,
f
, and
g
(see Section 1.6.1). Knowledge of (
T,v
) requires information about the substance beyond that contained in its
p
-
v
-
T
relationship. Functional relationships such as
u
(
T,v
) are sometimes called
thermal equations of state
. Two gases, helium and nitrogen for example, may follow the ideal gas law with reasonable accuracy, but show significantly different
u
(
T,v
) behavior.
