Ch. 13 – States of Matter III. Phase Changes (p. 425 – 429)

A. Phase Changes

A. Phase Changes Vaporization Conversion of a liquid to a gas or vapor When this occurs at the surface of a liquid that is not boiling, it is called evaporation molecules at the surface gain enough energy to overcome IMF

A. Phase Changes Equilibrium trapped molecules reach a balance between evaporation & condensation

A. Phase Changes Vapor Pressure pressure of vapor above a liquid at equilibrium depends on temp & IMF temp v.p. IMF v.p.

A. Phase Changes Patm b.p. IMF b.p. Boiling Point temp at which v.p. of liquid equals external pressure depends on Patm & IMF Normal B.P. - b.p. at 1 atm Patm b.p. IMF b.p.

A. Phase Changes Liquids don’t always boil at same temp B.P. varies with altitude

A. Phase Changes IMF m.p. Melting Point equal to freezing point Which has a higher m.p.? polar or nonpolar? covalent or ionic? polar ionic

A. Phase Changes Sublimation solid  gas v.p. of solid equals external pressure EX: dry ice, mothballs, solid air fresheners

B. Phase Diagrams Show the phases of a substance at different temps and pressures

Water vs. Carbon Dioxide B. Phase Diagrams Water vs. Carbon Dioxide