Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Chemistry FIFTH EDITION by Steven S. Zumdahl University of Illinois

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2 Chemistry FIFTH EDITION Chapter 10 Liquids and Solids

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 3 Section 10.8 CHANGES OF STATE (PHASE TRANSISTIONS) 1) MELTING: s  l 2) FREEZING: l  s 3) VAPORIZATION: l  g 4) SUBLIMATION: s  g 5)CONDENSATION: LIQUEFACTION: g  l DEPOSITION: g  s

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 4 VAPOR PRESSURE VAPORIZATION: LIQUID MOLECULES ESCAPE LIQUIDS SURFACE TO FORM A GAS PROCESS IS ENDOTHERMIC: ENERGY REQUIRED TO OVERCOME INTERMOLECULAR FORCES IN THE LIQUID

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 5 Figure Behavior of a Liquid in a Closed Container

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 6 Figure The Rates of Condensation and Evaporation

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 7 SYSTEM AT EQUILIBRIUM DYNAMIC EQUILIBRIUM MOLECULES STILL LEAVING THE LIQUID & COMING BACK CONDENSATION & VAPORIZATION STILL OCCURING

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 8 VAPOR PRESSURE OF THE LIQUID VAPOR PRESSURE AT EQUILIBRIUM EQUILIBRIUM VAPOR PRESSURE TWO OPPOSING PROCESSES OCCURING AT THE SAME RATE; THEREFORE, NO OBSERVABLE CHANGE

Copyright©2000 by Houghton Mifflin Company. All rights reserved is the pressure of the vapor present at equilibrium.... is determined principally by the size of the intermolecular forces in the liquid.... increases significantly with temperature. Volatile liquids have high vapor pressures.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 10 Figure Vapor Pressure

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 11 VOLATILE: LIQUIDS WITH HIGH VAPOR PRESSURE LIQUIDS W/ LARGE INTERMOLECULAR FORCES: REL. LOW VAPOR PRESSURE SINCE MOLECULES NEED HIGH ENERGIES TO ESCAPE VAPOR PHASE LIQUIDS W/ LARGE MOLAR MASSES: REL. LOW VAPOR PRESSURE BECAUSE OF LARGE LDF; ATOMS ARE MORE POLARIZABLE

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 12 Vapor Pressure INCREASES SIGNIFICANTLY WITH TEMPERATURE

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 13 Figure The Number of Molecules in a Liquid With a Given Energy Versus Kinetic Energy at Two Temperatures

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 14 Figure The Vapor Pressure of Water

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 15 ln (P vap ) =[-  H vap/ /R] [1/T] + C  H vap = enthalpy of vaporization R = universal gas constant T = Temperature in Kelvin

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 16 CLAUSIUS – CLAPEYRON EQUATION ln (P vap, T(1) / P vap, T(2) ) = [  H vap /R] [1/T 2 - 1/T 1 ]

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 17 Figure Heating Curve for Water

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 18 HEATING CURVE FOR WATER TWO IMPORTANT OBSERVATIONS: 1)TEMP. OF A SUBSTANCE REMAINS CONSTANT DURING A PHASE CHANGE 2)TEMP. RISES WHEN HEAT IS INPUTED WHILE A SUBSTANCE IS IN ONE PHASE

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 19 Melting Point Molecules break loose from lattice points and solid changes to liquid. (Temperature is constant as melting occurs.) vapor pressure of solid = vapor pressure of liquid

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 20 Figure The Vapor Pressures of Solid and Liquid Water

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 21 Boiling Point Constant temperature when added energy is used to vaporize the liquid. vapor pressure of liquid = pressure of surrounding atmosphere

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 22 NORMAL BOILING POINT TEMPERATURE AT WHICH THE VAPOR PRESSURE OF A LIQUID IS EXACTLY 1 ATMOSPHERE

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 23 CHANGES IN STATE DO NOT ALWAYS OCCUR AT EXACTLY THE BOILING POINT OR MELTING POINT SUPER COOLING: WATER REMAINS LIQUID BELOW 0°C AT 1 ATM. SUPERHEATING: REMAINS LIQUID ABOVE ITS BOILING POINT

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 24 Figure The Supercooling of Water

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 25 Homework Exercises # 79 – 87 odd, 88, 89, 91, 92

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 26 Section 10.9 PHASE DIAGRAMS GRAPHICAL WAY TO SUMMARIZE THE PHASES OF A SUBSTANCE AS A FUNCTION OF TEMPERATURE ANE PRESSURE CLOSED SYSTEM – no material can escape NO AIR IS PRESENT DIAGRAMS NOT DRAWN TO SCALE

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 27 Phase Diagram Represents phases as a function of temperature and pressure. critical temperature: temperature above which the vapor can not be liquefied. critical pressure: pressure required to liquefy at the critical temperature. critical point: critical temperature and pressure (for water, T c = 374°C and 218 atm).

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 28 The Phase Diagram for Water

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 29 TRIPLE POINT REPRESENTS TEMPERATURE AND PRESSURE AT WHICH 3 PHASES OF A SUBSTANCE COEXIST IN EQUILIBRIUM FOR WATER, – 0.01 °C, atm.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 30 Figure The Phase Diagram for Water

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 31 CRITICAL POINT CRITCAL TEMPERATURE: TEMPERATURE ABOVE WHICH THE VAPOR CANNOT BE LIQUEFIED NO MATTER WHAT PRESSURE IS APPLIED CRITICAL PRESSURE: VAPOR PRESSURE AT THE CRITICAL TEMPERATURE WATER: 374°C, 218 atm.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 32 HOW TO LIQUIFY? 1) Nitrogen: critical temp. = -147°C Gas cannot be liquified until temp. is Below -147°C 2) Methyl chloride: critical temp.= 144°C Liquify by increasing the pressure as long as temp. is below 144°C 3) Oxygen: critical temp. = -119°C Liquify by increasing the pressure as long as temp. below -119°C

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 33 Figure The Phase Diagram for Carbon Dioxide