Jump to first page Boiling Liquids at Reduced Pressure Acetone is boiled without heating.

Jump to first page Purpose n To boil acetone using an alternative method. n To boil acetone below its normal boiling point.

Jump to first page Demonstration n Acetone will be made to boil by reducing the vapor pressure.

Jump to first page Concepts n Reduced Pressure n Boiling Point n Entropy

Jump to first page Reduced Pressure n External pressure above the liquid is reduced. n Reducing external pressure, reduces the vapor pressure needed to induce boiling.

Jump to first page Boiling Point n Point at which vapor pressure of liquid slightly exceeds the external pressure above liquid. n The reduction in vapor pressure allows acetone to boil below it’s normal boiling point.

Jump to first page Entropy n A measure of disorder or randomness in a closed system. n Boiling causes molecules of the liquid to be converted from an ordered liquid state to a disordered gas state, increasing the entropy of the system.

Jump to first page Conclusions n By reducing external pressure above the liquid, the vapor pressure is also reduced. n At boiling point, the vapor pressure is slightly more than the external pressure. If external pressure is reduced, the boiling point will occur at a lower temperature than normal.

Jump to first page Comments n Cooking at High Elevations u atmospheric (external) pressure higher u boiling point of water is lower u food cooks more slowly at lower temperatures