Naked Science Forum

General Science => General Science => Topic started by: Locke on 02/02/2011 05:41:13

Title: Pressure and the Ensuing Temperatures of Evaporation and Solidification
Post by: Locke on 02/02/2011 05:41:13

If you have a certain liquid, not necessarily water, but let's use it for this example anyway, its boiling temperature is 100 degrees centigrade, and its freezing is 0 degrees centigrade.
If you raise the pressure on this liquid, is the difference between boiling and freezing still 100 degrees?
Please explain to the best of your ability.

Title: Pressure and the Ensuing Temperatures of Evaporation and Solidification
Post by: CliffordK on 02/02/2011 06:15:42

Water is somewhat unique.
Since ice expands when it freezes.
If you increase the pressure, you will moderately lower the freezing point, as well as increasing the boiling point.

Essentially all substances that don't decompose have a "Triple Point" where at a certain temperature & pressure, all 3 phases, solid, liquid, and gas will co-exist (the boiling point is equal to the melting point).

For water, the triple point is less than 1 ATM.
For many substances, the triple point is greater than 1 ATM.