Boiling Point

There are certain properties of solutions  which are directly connected with vapour pressure and one of it is boiling point.  You must have observed that water boils at a temperature of 100^oC.  This is because a liquid boils when its vapour pressure is equal to external pressure. The normal boiling point (BP) refers to an external pressure which is equal to the atmospheric pressure (760 mm Hg), which for water is 100^oC. With an increase is pressure, the boiling point increases,

e.g., the boiling point of water at 770 mm is 100. 37^oC. You must have noticed that in a pressure cooker the water boils at 121^oC at 103 kg/kilo pascal, for this a greater pressure must be overcome and thus the boiling point can be elevated. Conversely, the boiling point can be lowered at a reduced atmospheric pressure as in high altitudes i.e. if you boil potatoes at a hill station, it will take longer time to cook as compared to the planes. For every 290 m increase in altitude above sea level, the boiling point of water is lowered by 1oC.