Why vegetables are cooked with difficulty at a hill station?
Boiling is a special case of evaporation. It is the rapid conversion of a liquid into vapour by means of formation of bubbles. During boiling, vaporization is not restricted to the surface only but takes place throughout the bulk of the liquid.
The condition of free vaporization throughout the liquid is called boiling.
The temperature at which the vapour pressure of a liquid is equal to the external pressure is called the boiling temperature at that pressure. At 1 atm pressure, the boiling temperature is called normal boiling point. If the pressure is bar, then the boiling point is called standard boiling point of the liquid.
Now, If we go on hilly areas, the atmospheric pressure is less.
For boiling, vapour pressure should be equal to external pressure.
Since, atmospheric pressure is less,vapour pressure required for boiling will also be less.
So, boiling happens at a lower temperature. The temperature required for vegetables to be properly cooked is not achieved.The vegetables are not cooked properly because of this decrease in boiling point.