Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Chemistry FIFTH EDITION Chapter 10 Liquids and Solids
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2 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. 3 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. 4 Figure Behavior of a Liquid in a Closed Container
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 5 Figure The Rates of Condensation and Evaporation
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 6 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. 7 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. 9 Figure Vapor Pressure
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 10 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. 11 Vapor Pressure INCREASES SIGNIFICANTLY WITH TEMPERATURE
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 12 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. 13 Figure The Vapor Pressure of Water
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 14 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. 15 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. 16 Figure Heating Curve for Water
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 17 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. 18 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. 19 Figure The Vapor Pressures of Solid and Liquid Water
Copyright©2000 by Houghton Mifflin Company. All rights reserved. 20 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. 21 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. 22 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. 23 Figure The Supercooling of Water