[ Themodynamics
Table of Contents ].
A P-T diagram is the most common way to show
the phases of a substance. Figure 9 is the P-Tdiagram
for pure water. A P-T diagram can be constructed for any pure
substance. The line thatseparates
the solid and vapor phases is called the sublimation line.
The line that separates thesolid
and liquid phases is called the fusion line. The line that
separates the liquid and vaporphases
is called the vaporization line. The point where the three
lines meet is called the triplepoint.
The triple point is the only point at which all three phases
can exist in equilibrium. Thepoint
where the vaporization line ends is called the critical
point. At temperatures and pressuresgreater
than those at the critical point, no substance can exist as a
liquid no matter how great apressure
is exerted upon it.