Phase diagram of water template

Schematic P–T phase diagram of water: ice, liquid, vapour, the negative solid–liquid slope, triple point 0.01 °C / 0.006 atm, critical point 374 °C / 218 atm, normal melting and boiling points.

What the template shows

• Which phase is stable at each temperature and pressure; lines are where two phases coexist
• normal melting point
• normal boiling point
• Solid (ice)
• Gas (vapour)
• Triple point
• Critical point
• schematic, not to scale
• Each line is a two-phase equilibrium; at the triple point solid, liquid and vapour coexist (0.01 °C, 0.006 atm = 611.657 Pa).
• The solid–liquid line leans left (negative slope): ice is less dense than water, so pressure lowers the melting point (Clapeyron equation).
• Above the critical point (374 °C, 218 atm) liquid and gas can no longer be told apart: a supercritical fluid.
• At 1 atm water melts at 0 °C and boils at 100 °C; below 0.006 atm ice sublimes directly (freeze-drying).
• Every part of this figure is editable · sources on the template card

Drawn with 257 shapes – every one editable in MolDraw.

Sources

• Atkins, de Paula & Keeler, Atkins' Physical Chemistry, 11th ed., OUP 2018, ch. 4 Textbook
• NIST Chemistry WebBook: water Database