Chemistry / Unit 8 Chem 1441 worked example, 60 to 90 seconds
Reading a Phase Diagram for a Given State
The idea
Determining a substance's physical state from its phase diagram means locating the point at the given temperature and pressure, then reading which labeled region — solid, liquid, or gas — or which curve that point falls on.
In practice
On water's phase diagram, a point at -10 °C and 50 kPa falls in the solid region, so water there is ice; a point at 25 °C and 90 kPa falls in the liquid region; a point at 200 °C and 25 kPa falls in the gas region; a point sitting exactly on a boundary curve marks conditions where the two neighboring phases coexist in equilibrium.
Where people slip
Misreading which axis is pressure and which is temperature, or forgetting that a phase diagram's axes are often not drawn to a constant scale, places the same coordinates in the wrong region entirely.
Your place on the trail
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