Expert: Andrew Jones, B.Sc - 9/8/2004

Question
does salt water boil at a higher temp than water alone - please explain also ,web refs will be appreciated too thank you

Answer
Yes, salt water does boil at a higher temperature than plain old water.

This is called a "colligative property".  It is the effect of changing the molecular-level make-up of the water.

On one hand, the concentration of water has dropped slightly, in that some of the volume is now sodium chloride,so the partial vapour pressure is now lower than that for pure water, and the temperature must increase accordingly.

Secondly, the ions in solution interact with the water molecules and cause a decrease in randomness in the system.  Since steam is a more random state, more energy must be pumped in to bring it to the more random state.

Andrew Jones