chapt12_lec

chapt12_lec - 12-1Chapter 12Intermolecular Forces: Liquids,...

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Unformatted text preview: 12-1Chapter 12Intermolecular Forces: Liquids, Solids, and Phase Changes12-2Intermolecular Forces: Liquids, Solids, and Phase Changes12.1 An Overview of Physical States and Phase Changes12.2Quantitative Aspects of Phase Changes12.3 Types of Intermolecular Forces12.4Properties of the Liquid State12.5 The Uniqueness of Water12.6 The Solid State: Structure, Properties, and Bonding12.7 Advanced Materials12-3Table 12.1A Macroscopic Comparison of Gases, Liquids, and SolidsStateShape and VolumeCompressibilityAbility to FlowGasSolidLiquidConforms to shape and volume of containerConforms to shape of container; volume limited by surfaceMaintains its own shape and volumehighhighvery lowmoderatealmost nonealmost none12-4Types of Phases ChangesA liquid changing into a gas - vaporization;the reverse process - condensationA solid changing into a liquid - fusion(melting);the reverse process - freezing(solidification)A solid changing directly into a gas - sublimation;the reverse process - depositionEnthalpy changes accompany phase changes.Vaporization, fusion, and sublimation areEXOTHERMIC; the reverse processes ENDOTHERMIC12-5Heats of vaporization and fusion for several common substances.12-6Phase changes and their enthalpy changes12-7Within a phase, a change in heat is accompanied by a change in temperature which is associated with a change in average Ekas the most probable speed of the molecules changes.Quantitative Aspects of Phase ChangesDuring a phase change, a change in heat occurs at a constant temperature, which is associated with a change in Ep, as the average distance between molecules changes.q= (amount)(molar heat capacity)(T)q= (amount)(enthalpy of phase change)Energy changes result in a change in temperature and/or change in phase.12-8A cooling curve for the conversion of gaseous water to iceHeat Removed12-9Calculating the Loss of Heat -Cooling steam at 110oC down to ice at -10oCq= (amount)(molar heat capacity)(T) - change of tempq= (amount)(enthalpy of phase change) - change of phaseq= n Cwater(g)(100-110) +q= n (-HOvap) +q= n Cwater(l)(0-100) +q= n (-HOfus) +q= n Cwater(s)(-10-0) =12-10Liquid-gas equilibrium12-11The effect of temperature on the distribution of molecular speed in a liquid12-12Vapor pressure as a function of temperature and intermolecular forcesA linear plot of vapor pressure- temperature relationship12-13The Clausius-Clapeyron Equation ln P = -HvapR1T+C ln P2P1 = -HvapR1T2-1T1Subtraction two equations for two temperatures.12-14SAMPLE PROBLEM 12.1Using the Clausius-Clapeyron EquationSOLUTION:PROBLEM:The vapor pressure of ethanol is 115 torr at 34.9C. If Hvapof ethanol is 40.5 kJ/mol, calculate the temperature (in C) when the vapor pressure is 760 torr....
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chapt12_lec - 12-1Chapter 12Intermolecular Forces: Liquids,...

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