Editing Boiling point (section)

== Relation between the normal boiling point and the vapor pressure of liquids ==

[[Image:vapor_pressure_chart.svg|thumb|right|A log-lin vapor pressure chart for various liquids]]

The higher the vapor pressure of a liquid at a given temperature, the lower the normal boiling point (i.e., the boiling point at atmospheric pressure) of the liquid.

The vapor pressure chart to the right has graphs of the vapor pressures versus temperatures for a variety of liquids.<ref>{{cite book|editor=Perry, R.H. |editor2=Green, D.W. |title=[[Perry's Chemical Engineers' Handbook]]|edition=7th|publisher=McGraw-Hill|year=1997|isbn= 0-07-049841-5}}</ref> As can be seen in the chart, the liquids with the highest vapor pressures have the lowest normal boiling points.

For example, at any given temperature, [[methyl chloride]] has the highest vapor pressure of any of the liquids in the chart. It also has the lowest normal boiling point (−24.2&nbsp;°C), which is where the vapor pressure curve of methyl chloride (the blue line) intersects the horizontal pressure line of one atmosphere ([[Atmosphere (unit)|atm]]) of absolute vapor pressure.

The [[Critical point (thermodynamics)|critical point]] of a liquid is the highest temperature (and pressure) it will actually boil at.

See also [[Vapour pressure of water]].