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12-1 Chapter 12 Intermolecular Forces: Liquids, Solids, and Phase Changes.

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Presentation on theme: "12-1 Chapter 12 Intermolecular Forces: Liquids, Solids, and Phase Changes."— Presentation transcript:

1 12-1 Chapter 12 Intermolecular Forces: Liquids, Solids, and Phase Changes

2 12-2 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 Table 12.1 A Macroscopic Comparison of Gases, Liquids, and Solids StateShape and VolumeCompressibilityAbility to Flow Gas Solid Liquid Conforms to shape and volume of container Conforms to shape of container; volume limited by surface Maintains its own shape and volume high very lowmoderate almost none

4 12-4 Types of Phases Changes A liquid changing into a gas - vaporization; the reverse process - condensation A solid changing into a liquid - fusion (melting); the reverse process - freezing (solidification) A solid changing directly into a gas - sublimation; the reverse process - deposition Enthalpy changes accompany phase changes. Vaporization, fusion, and sublimation are EXOTHERMIC; the reverse processes ENDOTHERMIC

5 12-5 Heats of vaporization and fusion for several common substances.

6 12-6 Phase changes and their enthalpy changes

7 12-7 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) Energy changes result in a change in temperature and/or change in phase.

8 12-8 A cooling curve for the conversion of gaseous water to ice Heat Removed

9 12-9 Calculating the Loss of Heat - Cooling steam at 110 o C down to ice at -10 o C q = (amount)(molar heat capacity)(  T) - change of temp q = (amount)(enthalpy of phase change) - change of phase q = n C water(g) ( ) + q = n (-  H O vap ) + q = n C water(l) (0-100) + q = n (-  H O fus ) + q = n C water(s) (-10-0) =

10 12-10 Liquid-gas equilibrium

11 12-11 The effect of temperature on the distribution of molecular speed in a liquid

12 12-12 Vapor pressure as a function of temperature and intermolecular forces A linear plot of vapor pressure- temperature relationship

13 12-13 The Clausius-Clapeyron Equation Subtraction two equations for two temperatures.

14 12-14 SAMPLE PROBLEM 12.1Using the Clausius-Clapeyron Equation SOLUTION: PROBLEM: The vapor pressure of ethanol is 115 torr at 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 C = 308.0K ln 760 torr 115 torr = x10 3 J/mol J/mol*K 1 T2T K - T 2 = 350K = 77 0 C

15 12-15 Phase diagrams for CO 2 and H 2 O

16 12-16 Types of Intermolecular Forces - Bonding and Nonbonding

17 12-17 Types of Intermolecular Forces - Bonding and Nonbonding

18 12-18 Orientation of polar molecules because of dipole-dipole forces

19 12-19 Dipole moment and boiling point

20 12-20 The Hydrogen Bond A special dipole-dipole interaction occurs when a H atom is covalently bonded to a small electronegative atom, i.e. N, O, or F. The Hydrogen Bond is a through space bond between a H atom that is covalently bonded to one of the electronegative atoms to another of the electronegative atoms. H-F-----H-O-H H 2 O H-O-O

21 12-21 SAMPLE PROBLEM 12.2Drawing 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)

22 12-22 Hydrogen bonding and boiling point

23 12-23 The H-bonding abilitiy of the water molecule

24 12-24 DISPERSION (London) FORCES among nonpolar molecules separated Cl 2 molecules instantaneous dipoles

25 12-25 Effect of Molar Mass and boiling point DISPERSION (London) FORCES

26 12-26 Molecular shape and boiling point DISPERSION (London) FORCES

27 12-27 SAMPLE PROBLEM 12.3Predicting the Type and Relative Strength of Intermolecular Forces 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.

28 12-28 SOLUTION: SAMPLE PROBLEM 12.3Predicting 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.

29 12-29 Crystal Structures and the Unit Cell There are three types of cubic unit cells 1) Simple Cubic Unit Cell - 1 atom per unit cell 2) Body-Centered Cubic Unit Cell - 2 atoms per unit cell 3) Face-Centered Cubic Unit Cell - 4 atoms per unit cell

30 12-30 The crystal lattice and the unit cell

31 12-31 Figure (1 of 3) The three cubic unit cells Simple Cubic coordination number = 6 Atoms/unit cell = 1/8 * 8 = 1 1/8 atom at 8 corners

32 12-32 Figure (2 of 3) The three cubic unit cells Body-centered Cubic coordination number = 8 1/8 atom at 8 corners 1 atom at center Atoms/unit cell = (1/8*8) + 1 = 2

33 12-33 Figure (3 of 3) The three cubic unit cells Face-centered Cubic coordination number = 12 Atoms/unit cell = (1/8*8)+(1/2*6) = 4 1/8 atom at 8 corners 1/2 atom at 6 faces

34 12-34 Figure Packing of spheres simple cubic (52% packing efficiency) body-centered cubic (68% packing efficiency)

35 12-35 hexagonal unit cell Figure (continued) closest packing of first and second layers layer a layer b layer c hexagonal closest packing cubic closest packing abab… (74%) abcabc… (74%) expanded side views face-centered unit cell

36 12-36 SAMPLE PROBLEM 12.4Determining Atomic Radius from Crystal Structure PROBLEM:Barium is the largest nonradioactive alkaline earth metal. It has a body-centered cubic unit cell and a density of 3.62 g/cm 3. What is the atomic radius of barium? (Volume of a sphere: V = 4/3  r 3 ) PLAN:We can use the density and molar mass to find the volume of 1 mol of Ba. Since 68%(for a body-centered cubic) of the unit cell contains atomic material, dividing by Avogadro’s number will give us the volume of one atom of Ba. Using the volume of a sphere, the radius can be calculated. density of Ba (g/cm 3 ) volume of 1 mol Ba metalvolume of 1 Ba atom radius of a Ba atom multiply by packing efficiencyreciprocal divided by M V = 4/3  r 3 volume of 1 mol Ba atoms divide by Avogadro’s number

37 12-37 SAMPLE PROBLEM 12.4Determining Atomic Radius from Crystal Structure SOLUTION: continued Volume of Ba metal = g Ba mol Ba = 37.9 cm 3 /mol Ba 37.9 cm 3 /mol Ba x 0.68= 26 cm 3 /mol Ba atoms mol Ba atoms 6.022x10 23 atoms = 4.3x cm 3 /atom r 3 = 3V/4  = 2.2 x cm 1 cm g x 26 cm 3 mol Ba atoms x

38 12-38 End of Chapter 12

39 12-39 Figure 12.29Figure Cubic closest packing for frozen argon Cubic closest packing of frozen methane

40 12-40 Table 12.5 Characteristics of the Major Types of Crystalline Solids Particles Interparticle Forces Physical Behavior Examples (mp, 0 C) Atomic Molecular Ionic Metallic Network Group 8A(18) [Ne-249 to Rn-71] Molecules Positive & negative ions Atoms Soft, very low mp, poor thermal & electrical conductors DispersionAtoms Dispersion, dipole-dipole, H bonds Fairly soft, low to moderate mp, poor thermal & electrical conductors Nonpolar - O 2 [-219], C 4 H 10 [-138], Cl 2 [-101], C 6 H 14 [-95] Polar - SO 2 [-73], CHCl 3 [-64], HNO 3 [- 42], H 2 O[0.0] Covalent bond Metallic bond Ion-ion attraction Very hard, very high mp, usually poor thermal and electrical conductors Soft to hard, low to very high mp, excellent thermal and electrical conductors, malleable and ductile SiO 2 (quartz)[1610] C(diamond)[4000] Hard & brittle, high mp, good thermal & electrical conductors when molten NaCl [801] CaF 2 [1423] MgO [2852] Na [97.8] Zn [420] Fe [1535]

41 12-41 Figure The sodium chloride structure

42 12-42 Figure The zinc blende structure

43 12-43 Figure The fluorite (CaF 2 ) structure

44 12-44 Figure Crystal structures of metals cubic closest packing hexagonal closest packing

45 12-45 Figure Crystalline and amorphous silicon dioxide

46 12-46 Figure The band of molecular orbitals in lithium metal

47 12-47 Figure Electrical conductivity in a conductor, semiconductor, and insulator conductor semiconductor insulator

48 12-48 Figure The molecular basis of surface tension

49 12-49 Figure The hexagonal structure of ice

50 12-50 Figure The macroscopic properties of water and their atomic and molecular “roots”.

51 12-51 Table 12.3 Surface 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 1.7x x x x x10 -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

52 12-52 Figure Shape of water or mercury meniscus in glass adhesive forces stronger cohesive forces

53 12-53 Table 12.4 Viscosity of Water at Several Temperatures Temperature( 0 C) Viscosity (N*s/m 2 )* x x x x10 -3 *The units of viscosity are newton-seconds per square meter.

54 12-54 Figure Periodic trends in covalent and van der Waals radii (in pm)

55 12-55 Figure Covalent and van der Waals radii

56 12-56

57 12-57 Figure Crystal structures and band representations of doped semiconductors

58 12-58 Forward bias Reverse bias p-n junction Figure The p-n junction

59 12-59 heat in furnace with O 2 treat with photoresistapply template expose to light and solvent remove template etch SiO 2 with HF remove photoresist treat with Ga vapor remove SiO 2 Figure Steps in manufacturing a p-n junction

60 12-60 Figure Structures of two typical liquid crystal molecules

61 12-61 Figure The three common types of liquid crystal phases

62 12-62 Figure Schematic of a liquid crystal display (LCD)

63 12-63 Table 12.7 Some Uses of New Ceramics and Ceramic Materials CeramicApplications SiC, Si 3 N 4, TiB 2, Al 2 O 3 Whiskers(fibers) to strength Al and other ceramics Si 3 N 4 Car engine parts; turbine rotors for “turbo” cars; electronic sensor units Si 3 N 4, BN, Al 2 O 3 Supports or layering materials(as insulators) in electronic microchips SiC, Si 3 N 4, TiB 2, ZrO 2, Al 2 O 3, BN ZrO 2, Al 2 O 3 Cutting tools, edge sharpeners(as coatings and whole devices), scissors, surgical tools, industrial “diamond” BN, SiCArmor-plating reinforcement fibers(as in Kevlar composites) Surgical implants(hip and knee joints)

64 12-64 Figure Unit cells of some modern ceramic materials SiC BN cubic boron nitride (borazon)

65 12-65 Table 12.8 Molar Masses of Some Common Polymers Name M polymer (g/mol)nUses Acrylates2 x x10 3 Rugs, carpets Polyamide(nylons)1.5 x x10 2 Tires, fishing line Polycarbonate1 x x10 2 Compact disks Polyethylene3 x x10 4 Grocery bags Polyethylene (ultra- high molecular weight) 5 x x10 5 Hip joints Poly(ethylene terephthalate) 2 x x10 2 Soda bottles Polystyrene 3 x x10 3 Packing; coffee cups Poly(vinyl chloride) 1 x x10 3 Plumbing

66 12-66 Figure The random coil shape of a polymer chain

67 12-67 Figure The semicrystallinity of a polymer chain

68 12-68 Figure The viscosity of a polymer in solution

69 12-69 Table 12.9 Some Common Elastomers NameT g ( 0 C)* *Glass transition temperature Uses Poly(dimethyl siloxane) Polybutadiene Polyisoprene Polychloroprene (neoprene) Breast implants Rubber bands Surgical gloves Footwear; medical tubing

70 12-70 Figure Manipulating atoms tip of an atomic force microscope (AFM)

71 12-71 Figure Manipulating atoms nanotube gear

72 12-72 Figure B12.1 Diffraction of x-rays by crystal planes Tools of the Laboratory

73 12-73 Figure B12.2 Formation of an x-ray diffraction pattern of the protein hemoglobin Tools of the Laboratory

74 12-74 Tools of the Laboratory Figure B12.3 Scanning tunneling micrographs gallium arsenide semiconductormetallic gold


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