How do clouds desalinate water?

  • 1 Replies

0 Members and 1 Guest are viewing this topic.



  • Guest
How do clouds desalinate water?
« on: 20/01/2011 02:30:04 »
Hilton  asked the Naked Scientists:
Hi Chris,
With all the rain we are presently having, please can you tell me, how do the clouds desalinate / "unsalt" the sea water, which is where most of the rain water is coming from?  

Thanking you.
Kind regards,

What do you think?
« Last Edit: 20/01/2011 02:30:04 by _system »


Offline CliffordK

  • Neilep Level Member
  • ******
  • 6321
  • Site Moderator
    • View Profile
How do clouds desalinate water?
« Reply #1 on: 20/01/2011 02:39:43 »
When you boil a pot of water on the stove, you get steam, or water vapor mixed with droplets of water.

However, when seawater evaporates at well below the boiling point of water (due to partial pressures), you get primarily pure water vapor, i.e. single molecule H2O vapor which then mixes with air.  It is incapable of dissolving Salt (NaCl) into its ionic form, Na+ + Cl-

The boiling point of water is 100C
The boiling point of Sodium Chloride is: 1413C or 2575F, with a resulting much lower vapor pressure.

Thus, when the water evaporates (at low temperatures), the salt is mostly left behind.

Coastal towns are struck with wind-blown salt and salt water.  However, that settles out quickly and isn't carried inland very far.