Changes of State 10.4

Definitions Phase – any part of a system with uniform composition and properties. Condensation – gas changes to a liquid Molecules of liquid can evaporate and then condense and re-enter the liquid phase

Equilibrium Condensation and evaporation can happen at the same rate… Equilibrium – a dynamic condition in which 2 opposing changes occur at equal rates in a closed system No net change in amt. of substance in either phase.

Equilibrium and Vapor Pressure P is directly proportional to [ ] Equilibrium vapor pressure – pressure exerted by vapor in equilibrium with its corresponding liquid at a given temp Different for each liquid The higher the bonding the _____the EVP Think about the KMT

Definitions Volatile Liquids – liquids that evaporate readily __________ forces of attraction. Boiling – conversion of a liquid to a vapor within the liquid as well as at the surface Boiling point – the temp at which the equilibrium vapor pressure of the liquid = atm pressure

Boiling The ________ the atm pressure, the lower the b.p. Temp is constant while boiling Normal atmospheric pressure = 1 atm, 760 torr, 101.325kPa E needs to be + constantly to continue boiling

Molar Enthalpy of Vaporization MEV – the amt of E as heat that is needed to vaporize 1 mol of liquid at the liquids b.p. at constant pressure. ΔHv Measure of attraction of particles

Freezing and Melting Freezing – physical change of liquid to solid Loss of E Freezing point – the temp at which solid and liquid are at equilibrium at 1 atm At f. p. particles have same amt of ave K. E.

Melting At m.p. the solid and liquid have the same amt of k.e. also. For pure crystalline solids, f.p. and m.p. are at the same temp.

Molar Enthalpy of fusion Molar Enthalpy of fusion – the amount of energy as heat required to melt one mole of solid at the solids melting point.