|Water at the Triple Point|
The triple point of a substance is the temperature and pressure at which three phases (liquid, gas, and solid) of that substance may coexist in thermodynamic equilibrium.
For example, at high temperatures and increasing pressure, water
results in first liquid, and then solid (above 109 Pa
- a crystalline form of ice which is denser than water begins to form).
At lower temperatures the liquid state ceases to appear with compression
causing the state to pass directly from gas to solid.