Boiling is Evaporation Beneath a Liquid Surface

At what point boiling begins depends not only on temperature but also on pressure. As atmospheric pressure increases, the vapor molecules inside any bubbles that form must move faster in order to exert enough pressure from inside 

If you re chilly outside the shower stall, step back inside and be warmed by the condensation of the excess water vapor there. 

Before the boiling point is reached, the pressure of the water vapor inside the bubbles is less than the sum of atmospheric pressure plus water pressure. As a result, the bubbles of water vapor collapse. 

Boiling occurs when water molecules in the liquid are moving fast enough to generate bubbles of water vapor beneath the surface of the liquid. 

TTtc tigh hd of a pre.ssure cooker holds pressurized vapor above the water. surface, and this Inhibits boiling. In this way the boiling temperature of the water is increased. Any food placed in this hotter water cooks more quickly than food placed in water tailing at lOO C. 

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