1. 13 Liquids and Solids

2. 2 Chapter Goals 1.Kinetic-Molecular Description of Liquids and Solids 2.Intermolecular Attractions and Phase Changes The Liquid State 3.Viscosity 4.Surface Tension 5.Capillary Action 6.Evaporation 7.Vapor Pressure 8.Boiling Points and Distillation 9.Heat Transfer Involving Liquids

3. 3 Chapter Goals The Solid State 10.Melting Point 11.Heat Transfer Involving Solids 12.Sublimation and the Vapor Pressure of Solids 13.Phase Diagrams (P versus T) 14.Amorphous Solids and Crystalline Solids 15.Structures of Crystals 16.Bonding in Solids 17.Band Theory of Metals 18.Synthesis Question

4. 4 Kinetic-Molecular Description of Liquids and Solids Solids and liquids are condensed states.Solids and liquids are condensed states. –The atoms, ions, or molecules in solids and liquids are much closer to one another than in gases. –Solids and liquids are highly incompressible. Liquids and gases are fluids.Liquids and gases are fluids. –They easily flow. intermolecular attractions in liquids and solids are strong.The intermolecular attractions in liquids and solids are strong.

5. 5 Kinetic-Molecular Description of Liquids and Solids Schematic representation of the three common states of matter.

6. 6 Kinetic-Molecular Description of Liquids and Solids strengths of interactions degree of orderingIf we compare the strengths of interactions among particles and the degree of ordering of particles, we see that Gases< Liquids < Solids Miscible liquidsMiscible liquids are soluble in each other. –Examples of miscible liquids: Water dissolves in alcohol. Gasoline dissolves in motor oil.

7. 7 Kinetic-Molecular Description of Liquids and Solids Immiscible liquidsImmiscible liquids are insoluble in each other. –Two examples of immiscible liquids: Water does not dissolve in oil. Water does not dissolve in cyclohexane.

8. 8 Intermolecular Attractions and Phase Changes There are four important intermolecular attractions. –This list is from strongest attraction to the weakest attraction. 1.Ion-ion interactions –The force of attraction between two oppositely charged ions is governed by Coulomb’s law.

9. 9 Intermolecular Attractions and Phase Changes Coulomb’s law determines: 1.The melting and boiling points of ionic compounds. 2.The solubility of ionic compounds. Example 13-1: Arrange the following ionic compounds in the expected order of increasing melting and boiling points. NaF, CaO, CaF 2 You do it! What important points must you consider?

10. 10 Intermolecular Attractions and Phase Changes

11. 11 Intermolecular Attractions and Phase Changes 2.Dipole-dipole interactions –Consider BrF a polar molecule.

12. 12 Intermolecular Attractions and Phase Changes 3.Hydrogen bonding –Consider H 2 O a very polar molecule.

13. 13 Intermolecular Attractions and Phase Changes 3.Hydrogen bonding –Consider H 2 O a very polar molecule.

14. 14 Intermolecular Attractions and Phase Changes

15. 15 Intermolecular Attractions and Phase Changes 4.London Forces are very weak. –They are the weakest of the intermolecular forces. –This is the only attractive force in nonpolar molecules. Consider Ar as an isolated atom.

16. 16 Intermolecular Attractions and Phase Changes In a group of Ar atoms the temporary dipole in one atom induces other atomic dipoles.

17. 17 Intermolecular Attractions and Phase Changes Similar effects occur in a group of I 2 molecules.

18. 18 The Liquid State Viscosity Viscosity is the resistance to flow. –For example, compare how water pours out of a glass compared to molasses, syrup or honey. Oil for your car is bought based on this property. –10W30 or 5W30 describes the viscosity of the oil at high and low temperatures.

19. 19 The Liquid State An example of viscosity of two liquids.

20. 20 The Liquid State Surface Tension Surface tension is a measure of the unequal attractions that occur at the surface of a liquid. The molecules at the surface are attracted unevenly.

21. 21 The Liquid State Floating paper clip demonstration of surface tension.

22. 22 The Liquid State Capillary Action Capillary action is the ability of a liquid to rise (or fall) in a glass tube or other container

23. 23 The Liquid State Cohesive forces are the forces that hold liquids together. Adhesive forces are the forces between a liquid and another surface. –Capillary rise implies that the: Adhesive forces > cohesive forces –Capillary fall implies that the: Cohesive forces > adhesive forces

24. 24 The Liquid State Water exhibits a capillary rise. Water Mercury Mercury exhibits a capillary fall.

25. 25 The Liquid State Capillary action also affects the meniscus of liquids.

26. 26 The Liquid State Evaporation Evaporation is the process in which molecules escape from the surface of a liquid and become a gas. Evaporation is temperature dependent.

27. 27 The Liquid State

28. 28 The Liquid State This is an animation of evaporation

29. 29 The Liquid State Vapor Pressure Vapor pressure is the pressure exerted by a liquid’s vapor on its surface at equilibrium. Vapor Pressure (torr) and boiling point for three liquids at different temperatures. 0 o C 20 o C 30 o Cnormal boiling point diethyl ether185 442 647 36 o C ethanol12 44 7478 o C water 5 18 32100 o C What are the intermolecular forces in each of these compounds? You do it!

30. 30 The Liquid State Vapor Pressure as a function of temperature.

31. 31 The Liquid State Boiling Points and Distillation boiling pointThe boiling point is the temperature at which the liquid’s vapor pressure is equal to the applied pressure. normalboiling pointThe normal boiling point is the boiling point when the pressure is exactly 1 atm. Distillation is a method we use to separate mixtures of liquids based on their differences in boiling points.

32. 32 The Liquid State Distillation Distillation is a process in which a mixture or solution is separated into its components on the basis of the differences in boiling points of the components. Distillation is another vapor pressure phenomenon.

33. 33 The Liquid State Heat Transfer Involving Liquids From Chapter 1 Example 13-2: How much heat is released by 2.00 x 10 2 g of H 2 O as it cools from 85.0 o C to 40.0 o C? The specific heat of water is 4.184 J/g o C. You do it!

34. 34 The Liquid State

35. 35 The Liquid State Molar heat capacity is the amount of heat required to raise the temperature of one mole of a substance 1.00 o C. Example 13-3: The molar heat capacity of ethyl alcohol, C 2 H 5 OH, is 113 J/mol o C. How much heat is required to raise the T of 125 g of ethyl alcohol from 20.0 o C to 30.0 o C? 1 mol C 2 H 5 OH = 46.0 g You do it!

36. 36 The Liquid State

37. 37 The Liquid State The calculations we have done up to now tell us the energy changes as long as the substance remains in a single phase. Next, we must address the energy associated with phase changes. –For example, solid to liquid or liquid to gas and the reverse. Heat of Vaporization is the amount of heat required to change 1.00 g of a liquid substance to a gas at constant temperature. –Heat of vaporization has units of J/g. Heat of Condensation is the reverse of heat of vaporization, phase change from gas to liquid.

38. 38 The Liquid State Molar heat of vaporization or  H vap The  H vap is the amount of heat required to change 1.00 mole of a liquid to a gas at constant temperature.  H vap has units of J/mol. Molar heat of condensation The reverse of molar heat of vaporization is the heat of condensation.

39. 39 The Liquid State

40. 40 The Liquid State Example 13-4: How many joules of energy must be absorbed by 5.00 x 10 2 g of H 2 O at 50.0 o C to convert it to steam at 120 o C? The molar heat of vaporization of water is 40.7 kJ/mol and the molar heat capacities of liquid water and steam are 75.3 J/mol o C and 36.4 J/mol o C, respectively. You do it!

41. 41 The Liquid State Next, let’s calculate the energy required to boil the water. Finally, let’s calculate the heat required to heat steam from 100 to 120 o C.

42. 42 The Liquid State The total amount of energy for this process is the sum of the 3 pieces we have calculated.

43. 43 The Liquid State Example 13-5: If 45.0 g of steam at 140 o C is slowly bubbled into 450 g of water at 50.0 o C in an insulated container, can all the steam be condensed? You do it!

44. 44 The Liquid State

45. 45 The Liquid State Clausius-Clapeyron equation –determine vapor pressure of a liquid at a new T –determine what T we must heat something to get a specified vapor pressure –way to determine  H vap if we know pressure at 2 T’s

46. 46 The Liquid State In Denver the normal atmospheric pressure is 630 torr. At what temperature does water boil in Denver?

47. 47 The Liquid State

48. 48 The Liquid State Boiling Points of Various Kinds of Liquids GasMWBP( o C)

49. 49 The Liquid State

50. 50 The Liquid State

51. 51 The Liquid State

52. 52 The Liquid State

53. 53 The Liquid State

54. 54 The Liquid State

55. 55 The Liquid State

56. 56 The Liquid State At the molecular level what happens when a species boils?

57. 57 The Liquid State Example 13-6: Arrange the following substances in order of increasing boiling points. C 2 H 6, NH 3, Ar, NaCl, AsH 3 You do it! Ar < C 2 H 6 < AsH 3 < NH 3 < NaCl nonpolar nonpolar polar very polar ionic London London dipole-dipole H-bonding ion-ion

58. 58 The Solid State Normal Melting Point normal melting pointThe normal melting point is the temperature at which the solid melts (liquid and solid in equilibrium) at exactly 1.00 atm of pressure. The melting point increases as the strength of the intermolecular attractions increase.

59. 59 The Solid State Which requires more energy? What experimental proof do you have?

60. 60 Heat Transfer Involving Solids Heat of Fusion Heat of fusionHeat of fusion is the amount of heat required to melt one gram of a solid at its melting point at constant temperature. Heat of crystallization Heat of crystallization is the reverse of the heat of fusion.

61. 61 Heat Transfer Involving Solids Molar heat of fusion or  H fusion The molar heat of fusion is the amount of heat required to melt a mole of a substance at its melting point. The molar heat of crystallization is the reverse of molar heat of fusion

62. 62 Heat Transfer Involving Solids Here is a summary of the heats of transformation for water.

63. 63 Heat Transfer Involving Solids Example 13-7: Calculate the amount of heat required to convert 150.0 g of ice at - 10.0 o C to water at 40.0 o C. specific heat of ice is 2.09 J/g o C you do it

64. 64 Heat Transfer Involving Solids

65. 65 Sublimation and the Vapor Pressure of Solids Sublimation In the sublimation process the solid transforms directly to the vapor phase without passing through the liquid phase. Solid CO 2 or “dry” ice does this well.

66. 66 Phase Diagrams (P versus T) Phase diagrams are a convenient way to display all of the different phase transitions of a substance. This is the phase diagram for water.

67. 67 Phase Diagrams (P versus T) Compare water’s phase diagram to carbon dioxide’s phase diagram.

68. 68 Amorphous Solids and Crystalline Solids Amorphous solids do not have a well ordered molecular structure. –Examples of amorphous solids include waxes, glasses, asphalt. unit cellsCrystalline solids have well defined structures that consist of extended array of repeating units called unit cells. –Crystalline solids display X-ray diffraction patterns which reflect the molecular structure. –The Bragg equation, detailed in the textbook, describes how an X-ray diffraction pattern can be used to determine the interatomic distances in crystals.

69. 69 Structure of Crystals Unit cells are the smallest repeating unit of a crystal. –As an analogy, bricks are repeating units for buildings. There are seven basic crystal systems.

70. 70 Structure of Crystals We shall look at the three variations of the cubic crystal system. Simple cubic unit cells. –The balls represent the positions of atoms, ions, or molecules in a simple cubic unit cell.

71. 71 Structure of Crystals In a simple cubic unit cell each atom, ion, or molecule at a corner is shared by 8 unit cells –Thus 1 unit cell contains 8(1/8) = 1 atom, ion, or molecule.

72. 72 Structure of Crystals Body centered cubic (bcc) has an additional atom, ion, or molecule in the center of the unit cell. On a body centered cubic unit cell there are 8 corners + 1 particle in center of cell. –1 bcc unit cell contains 8(1/8) + 1 = 2 particles.

73. 73 Structure of Crystals A face centered cubic (fcc) unit cell has a cubic unit cell structure with an extra atom, ion, or molecule in each face.

74. 74 Structure of Crystals A face centered cubic unit cell has 8 corners and 6 faces. –1 fcc unit cell contains 8(1/8) + 6(1/2) = 4 particles.

75. 75 Bonding in Solids Molecular Solids have molecules in each of the positions of the unit cell. –Molecular solids have low melting points, are volatile, and are electrical insulators. Examples of molecular solids include: –water, sugar, carbon dioxide, benzene

76. 76 Bonding in Solids Covalent Solids have atoms that are covalently bonded to one another Some examples of covalent solids are: Diamond, graphite, SiO 2 (sand), SiC

77. 77 Bonding in Solids Ionic Solids have ions that occupy the positions in the unit cell. Examples of ionic solids include: –CsCl, NaCl, ZnS

78. 78 Bonding in Solids Metallic Solids may be thought of as positively charged nuclei surrounded by a sea of electrons. The positive ions occupy the crystal lattice positions. Examples of metallic solids include: –Na, Li, Au, Ag, ……..

79. 79 Bonding in Solids Variations in Melting Points for Molecular Solids What are the intermolecular forces in each solid? CompoundMelting Point ( o C) ice 0.0 ammonia -77.7 benzene, C 6 H 6 5.5 napthalene, C 10 H 8 80.6 benzoic acid, C 6 H 5 CO 2 H 122.4

80. 80 Bonding in Solids Variations in Melting Points for Covalent Solids SubstanceMelting Point ( o C) sand, SiO 2 1713 carborundum, SiC ~2700 diamond >3550 graphite 3652-3697

81. 81 Bonding in Solids Variations in Melting Points for Ionic Solids CompoundMelting Point ( o C) LiF 842 LiCl 614 LiBr 547 LiI 450 CaF 2 1360 CaCl 2 772 CaBr 2 730 CaI 2 740

82. 82 Bonding in Solids Variations in Melting Points for Metallic Solids MetalMelting Point ( o C) Na 98 Pb 328 Al 660 Cu 1083 Fe 1535 W 3410

83. 83 Bonding in Solids Example 13-8. A group IVA element with a density of 11.35 g/cm 3 crystallizes in a face-centered cubic lattice whose unit cell edge length is 4.95 Å. Calculate the element’s atomic weight. What is the atomic radius of this element?

84. 84 Bonding in Solids Face centered cubic unit cells have 4 atoms, ions, or molecules per unit cell. Problem solution pathway: 1.Determine the volume of a single unit cell. 2.Use the density to determine the mass of a single unit cell. 3.Determine the mass of one atom in a unit cell. 4.Determine the mass of 1 mole of these atoms

85. 85 Bonding in Solids 1.Determine the volume of a single unit cell. 2.Use the density to determine the mass of a unit cell.

86. 86 Bonding in Solids 3.Determine the mass of one atom in the unit cell. 4.Determine the mass of one mole of these atoms.

87. 87 Bonding in Solids To determine an atomic radius requires some geometry. For simple cubic unit cells: –The edge length = 2 radii

88. 88 Bonding in Solids For face-centered cubic unit cells: –The face diagonal =  2 x edge length. –The diagonal length = 4 radii.

89. 89 Bonding in Solids For body-centered cubic unit cells: –The body diagonal =  3 x edge length. –The diagonal length = 4 radii.

90. 90 Bonding in Solids Determine the diagonal length then divide by 4 to get the atomic radius.

91. 91 Band Theory of Metals Sodium’s 3s orbitals can interact to produce overlapping orbitals

92. 92 Band Theory of Metals The 3s orbitals can also overlap with unfilled 3p orbitals

93. 93 Band Theory of Metals Insulators have a large gap between the s and p bands. forbidden zone –Gap is called the forbidden zone. Semiconductors have a small gap between the bands.

94. 13 Liquids and Solids