1. 12-1 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 12 Intermolecular Forces: แรงระหว่างโมเลกุล : Liquids, Solids, and Phase Changes ของเหลว ของแข็ง และการเปลี่ยนวัฏภาค

2. 12-2 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Intermolecular Forces: Liquids, Solids, and Phase Changes 12.1 An Overview of Physical States and Phase Changes 12.2 Quantitative Aspects of Phase Changes 12.3 Types of Intermolecular Forces 12.4 Properties of the Liquid State 12.5 The Uniqueness of Water 12.6 The Solid State: Structure, Properties, and Bonding 12.7 Advanced Materials

3. 12-3 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ATTRACTIVE FORCES electrostatic in nature Intramolecular forces bonding forces within These forces exist within each molecule. chemical They influence the chemical properties of the substance. Intermolecular forces nonbonding forces between These forces exist between molecules. physical They influence the physical properties of the substance.

4. 12-4 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Phase Changes solidliquidgas melting freezing vaporizing condensing sublimination endothermic exothermic

5. 12-5 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Table 12.1 A Macroscopic Comparison of Gases, Liquids, and Solids StateShape and VolumeCompressibility Ability to Flow GasConforms to shape and volume of container high LiquidConforms to shape of container; volume limited by surface very lowmoderate SolidMaintains its own shape and volume almost none

6. 12-6 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.1 Heats of vaporization and fusion for several common substances.

7. 12-7 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.2 Phase changes and their enthalpy changes.

8. 12-8 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.3 A cooling curve for the conversion of gaseous water to ice.

9. 12-9 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Within a phase, a change in heat is accompanied by a change in temperature which is associated with a change in average E k as the most probable speed of the molecules changes. Quantitative Aspects of Phase Changes During a phase change, a change in heat occurs at a constant temperature, which is associated with a change in E p, as the average distance between molecules changes. q = (amount)(molar heat capacity)(  T) q = (amount)(enthalpy of phase change)

10. 12-10 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.4 Liquid-gas equilibrium.

11. 12-11 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.5 The effect of temperature on the distribution of molecular speed in a liquid.

12. 12-12 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.6Figure 12.7 Vapor pressure as a function of temperature and intermolecular forces. A linear plot of vapor pressure- temperature relationship.

13. 12-13 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Clausius-Clapeyron Equation

14. 12-14 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. SAMPLE PROBLEM 12.1 Using the Clausius-Clapeyron Equation SOLUTION: PROBLEM: The vapor pressure of ethanol is 115 torr at 34.9 0 C. If  H vap of ethanol is 40.5 kJ/mol, calculate the temperature (in 0 C) when the vapor pressure is 760 torr. PLAN:We are given 4 of the 5 variables in the Clausius-Clapeyron equation. Substitute and solve for T 2. 34.9 0 C = 308.0K ln 760 torr 115 torr = -40.5 x10 3 J/mol 8.314 J/mol*K 1 T2T2 1 308K - T 2 = 350K = 77 0 C

15. 12-15 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.8 Iodine subliming. iodine solid iodine vapor iodine solid test tube with ice

16. 12-16 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.9 Phase diagrams for CO 2 and H 2 O. CO 2 H2OH2O

17. 12-17 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. bond length covalent radius van der Waal’s distance van der Waal’s radius Figure 12.10 Covalent and van der Waals radii.

18. 12-18 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.11 Periodic trends in covalent and van der Waals radii (in pm).

19. 12-19 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

20. 12-20 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

21. 12-21 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.12 Polar molecules and dipole-dipole forces. solid liquid

22. 12-22 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. THE HYDROGEN BOND a dipole-dipole intermolecular force The elements which are so electronegative are N, O, and F. A hydrogen bond may occur when an H atom in a molecule, bound to small highly electronegative atom with lone pairs of electrons, is attracted to the lone pairs in another molecule... F H O N FH O NH hydrogen bond donor hydrogen bond acceptor hydrogen bond acceptor hydrogen bond donor hydrogen bond donor hydrogen bond acceptor

23. 12-23 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.13 Dipole moment and boiling point.

24. 12-24 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. SAMPLE PROBLEM 12.2 Drawing Hydrogen Bonds Between Molecules of a Substance SOLUTION: PROBLEM:Which of the following substances exhibits H bonding? For those that do, draw two molecules of the substance with the H bonds between them. (a)(b) (c) PLAN:Find molecules in which H is bonded to N, O or F. Draw H bonds in the format -B: H-A-. (a) C 2 H 6 has no H bonding sites. (c) (b)

25. 12-25 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.14 Hydrogen bonding and boiling point.

26. 12-26 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Polarizability and Charged-Induced Dipole Forces distortion of an electron cloud Polarizability increases down a group size increases and the larger electron clouds are further from the nucleus Polarizability decreases left to right across a period increasing Z eff shrinks atomic size and holds the electrons more tightly Cations are less polarizable than their parent atom because they are smaller. Anions are more polarizable than their parent atom because they are larger.

27. 12-27 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.15 Dispersion forces among nonpolar molecules. separated Cl 2 molecules instantaneous dipoles

28. 12-28 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.16 Molar mass and boiling point.

29. 12-29 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.17 Molecular shape and boiling point. more points for dispersion forces to act fewer points for dispersion forces to act

30. 12-30 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. PROBLEM:For each pair of substances, identify the dominant intermolecular forces in each substance, and select the substance with the higher boiling point. (a) MgCl 2 or PCl 3 (b) CH 3 NH 2 or CH 3 F (c) CH 3 OH or CH 3 CH 2 OH (d) Hexane (CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 ) or 2,2-dimethylbutane PLAN: Bonding forces are stronger than nonbonding (intermolecular) forces. Hydrogen bonding is a strong type of dipole-dipole force. Dispersion forces are decisive when the difference is molar mass or molecular shape. SAMPLE PROBLEM 12.3 Predicting the Type and Relative Strength of Intermolecular Forces

31. 12-31 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. SOLUTION: SAMPLE PROBLEM 12.3 Predicting the Type and Relative Strength of Intermolecular Forces continued (a) Mg 2+ and Cl - are held together by ionic bonds while PCl 3 is covalently bonded and the molecules are held together by dipole-dipole interactions. Ionic bonds are stronger than dipole interactions and so MgCl 2 has the higher boiling point. (b) CH 3 NH 2 and CH 3 F are both covalent compounds and have bonds which are polar. The dipole in CH 3 NH 2 can H bond while that in CH 3 F cannot. Therefore CH 3 NH 2 has the stronger interactions and the higher boiling point. (c) Both CH 3 OH and CH 3 CH 2 OH can H bond but CH 3 CH 2 OH has more CH for more dispersion force interaction. Therefore CH 3 CH 2 OH has the higher boiling point. (d) Hexane and 2,2-dimethylbutane are both nonpolar with only dispersion forces to hold the molecules together. Hexane has the larger surface area, thereby the greater dispersion forces and the higher boiling point.

32. 12-32 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.18 Summary diagram for analyzing the intermolecular forces in a sample. INTERACTING PARTICLES (atoms, molecules, ions) INTERACTING PARTICLES (atoms, molecules, ions) ions only IONIC BONDING (Section 9.2) ions only IONIC BONDING (Section 9.2) ion + polar molecule ION-DIPOLE FORCES ion + polar molecule ION-DIPOLE FORCES ions present ions not present polar molecules only DIPOLE-DIPOLE FORCES polar molecules only DIPOLE-DIPOLE FORCES HYDROGEN BONDING HYDROGEN BONDING polar + nonpolar molecules DIPOLE- INDUCED DIPOLE FORCES polar + nonpolar molecules DIPOLE- INDUCED DIPOLE FORCES nonpolar molecules only DISPERSION FORCES only nonpolar molecules only DISPERSION FORCES only Dispersion forces also present H bonded to N, O, or F

33. 12-33 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.19 The molecular basis of surface tension. hydrogen bonding occurs in three dimensions hydrogen bonding occurs across the surface and below the surface the net vector for attractive forces is downward

34. 12-34 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Table 12.3Surface Tension and Forces Between Particles SubstanceFormula Surface Tension (J/m 2 ) at 20 0 C Major Force(s) diethyl ether ethanol butanol water mercury dipole-dipole; dispersion H bonding H bonding; dispersion H bonding metallic bonding 1.7x10 -2 2.3x10 -2 2.5x10 -2 7.3x10 -2 48x10 -2 CH 3 CH 2 OCH 2 CH 3 CH 3 CH 2 OH CH 3 CH 2 CH 2 CH 2 OH H2OH2O Hg

35. 12-35 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.20 Shape of water or mercury meniscus in glass. adhesive forces stronger cohesive forces H2OH2O capillarity Hg

36. 12-36 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Table 12.4 Viscosity of Water at Several Temperatures Temperature ( 0 C) Viscosity (N*s/m 2 )* 20 40 60 80 1.00x10 -3 0.65x10 -3 0.47x10 -3 0.35x10 -3 *The units of viscosity are newton-seconds per square meter. viscosity - resistance to flow

37. 12-37 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.21 The H-bonding ability of the water molecule. hydrogen bond donor hydrogen bond acceptor

38. 12-38 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Unique Nature of Water great solvent properties due to polarity and hydrogen bonding ability exceptional high specific heat capacity high surface tension and capillarity density differences of liquid and solid states

39. 12-39 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.22 The hexagonal structure of ice.

40. 12-40 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.23 The expansion and contraction of water.

41. 12-41 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.24 The macroscopic properties of water and their atomic and molecular “roots”.