Phase Change Diagram

The phase of a substance is a function of temperature, specific volume, and pressure. This is often expressed graphically with:

• Temperature-specific volume ($T$-$v$) diagrams
• Pressure-specific volume ($P$-$v$) diagrams
• Pressure-temperature ($P$-$T$) diagrams
• Pressure-specific volume-temperature ($P$-$v$-$T$) surface

T-v Diagram

• The dotted lines on the T-v diagram represents lines of constant pressure

$f$ and $g$ points on diagram:

P-v Diagram

P-T Diagram

P-v-T Surface