Vapour pressure

Consider a liquid at a constant temperature. If the intermolecular forces of the liquid is weak, the molecules of the liquid are readily to absorb energy from the surroundings to escape from the liquid to the vapour phase, and thus builds up a high vapour pressure. Therefore, the lower the intermolecular forces of a liquid, the higher the vapour pressure is.

On the other hand, if the intermolecular forces of the liquid is weak, theliquid would have a low boiling point. Therefore, the lower the intermolecular forces of a liquid, the lower its boiling point is.

Conclusively, the higher the vapour pressure of a liquid, the lower the boilingpoint is.


考慮在固定溫度下的某液體，若該液體的分子間引力較弱，則液體分子較容易吸收周圍環境的能量由液體逸出至蒸氣相，從而建立一較高的蒸氣壓。因此，液體的分子間引力愈低，其蒸氣壓愈高。

另一方面，若該液體的分子間引力較弱，其沸點較低。因此，液體的分子間引力愈低，其沸點愈低。

結論是：液體的蒸氣壓愈高，其沸點愈低。