1. “Do me a solid..” the story of the other 2 states of matter Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1

2. 2 Gas, The oddball of the trio: The Three States of Matter compared

3. Solids/Liquids compared to gas H 2 O (s)  H 2 O(l) Δ H = 6 kJ/mol H 2 O (l)  H 2 O(g) Δ H = 41 kJ/mol s/l slightly compressible, density similar (see table 10.1) Copyright©2000 by Houghton Mifflin Company. All rights reserved. 3

4. 4 Intermolecular Forces Forces between (not within) molecules in “condensed states” dipole-dipole attraction: molecules with dipoles orient themselves so that “+” and “  ” ends attract hydrogen bonds: dipole-dipole attraction in which hydrogen is bound to a highly electronegative atom. (F, O, N)

5. Figure 10.2 Dipole-Dipole Attractions 1% as strong as the covalent/ionic bond. Rapidly weaken with increase distance Copyright©2000 by Houghton Mifflin Company. All rights reserved. 5

6. Figure 10.3 A Water Molecule H-bonding strong: small H big electro. Diff Water: high melting/ boiling points – to overcome this force Also seen with H-F, H-N bonds Copyright©2000 by Houghton Mifflin Company. All rights reserved. 6

7. 7 Figure 10.4 The Boiling Points of the Covalent Hydrides of the Elements in Groups 4A, 5A, 6A, and 7A H-bonding for H-O, H-F, H-N

8. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 8 What about non-polar molecules and noble gases when condensed? : London Dispersion Forces

9. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 9 London Dispersion Forces 4 relatively weak forces that exist among noble gas atoms and nonpolar molecules when in the condensed state (Ar, C 8 H 18 ) 4 caused by instantaneous dipole, in which electron distribution becomes asymmetrical.

10. London Forces the ease with which electron “cloud” of an atom can be distorted is called polarizability. Large molecules, more polarizable. Explain Table 10.2, pg. 455. Explain the trend in Halogen b.p. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 10

11. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 11 Focus on Liquid Properties Surface Tension Capillary Action Viscosity

12. Surface Tension: The resistance to an increase in its surface area (polar molecules).

13. Surface tension explained

14. Capillary Action: Spontaneous rising of a liquid in a narrow tube. Cohesion vs. Adhesion

15. Viscosity: Resistance to flow (molecules with large intermolecular forces). 15 High IF, high viscosity (thickness) Ex. Glycerol, gasoline vs. grease Ex: add xanthan gum to water, increases the viscosity

16. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 16 Focus on Solids: Types of Solids Crystalline Solids: highly regular arrangement of their components [table salt (NaCl), pyrite (FeS 2 )]. Amorphous solids: considerable disorder in their structures (glass).

17. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 17 Crystalline Solid Lattice: A 3-dimensional system of points designating the centers of components (atoms, ions, or molecules) that make up the substance. Unit Cell: The smallest repeating unit of the lattice. simple cubic

18. Unit Cells

19. Three common types of unit cell. –Simple cubic, atoms at the corners of a simple cube, each atom shared by 8 unit cells; –Body-centered cubic (bcc), atoms at the corners of a cube plus one in the center of the body of the cube, corner atoms shared by 8 unit cells, center atom completely enclosed in one unit cell; –Face-centered cubic (fcc), atoms at the corners of a cube plus one atom in the center of each face of the cube, –corner atoms shared by 8 unit cells, face atoms shared by 2 unit cells. Unit Cells Three common types of unit cell. –Simple cubic, atoms at the corners of a simple cube, each atom shared by 8 unit cells; –Body-centered cubic (bcc), atoms at the corners of a cube plus one in the center of the body of the cube, corner atoms shared by 8 unit cells, center atom completely enclosed in one unit cell; –Face-centered cubic (fcc), atoms at the corners of a cube plus one atom in the center of each face of the cube, –corner atoms shared by 8 unit cells, face atoms shared by 2 unit cells.

20. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 20 Figure 10.9 Three Cubic Unit Cells and the Correspond ing Lattices

21. Crystal Structure of Sodium Chloride Face-centered cubic. Two equivalent ways of defining unit cell: –Cl - (larger) ions at the corners of the cell, or –Na + (smaller) ions at the corners of the cell. The cation :anion ratio in the unit cell must be a 1:1, since formula is NaCl Visualize face center Cl -, Na + in spaces

22. Crystal Structure of Sodium Chloride

23. How many Na +, Cl - do you see? Count them!

24. Body Center = 1 unit Face Center = 1/2 unit Edge = 1/4 unit Corner = 1/8 unit

25. Three Cubic Unit Cells and the Correspondin g Lattices

26. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 26 How do we determine crystal structure? Interference of x-rays can show us the distance between the particles in the crystal

27. the Bragg Equation sin θ = xy/d, so xy=d sin θ and yz =d sin θ So, xy + yz = d sin θ + d sin θ = 2d sin θ For in phase xy + yz = nλ 27

28. The Bragg Equation xy + yz = nλ xy + yz = 2d sin θ, So, n = 2d sin  d = distance between atoms n = an integer = wavelength of the x-rays See problems 10.1, pg 461 28

29. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 29 Bragg Equation Used for analysis of crystal structures. n = 2d sin  d = distance between atoms n = an integer = wavelength of the x-rays

30. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 30 Types of Crystalline Solids Ionic Solid: contains ions at the points of the lattice that describe the structure of the solid (NaCl). Molecular Solid: discrete covalently bonded molecules at each of its lattice points (sucrose, ice). Atomic Solid: atoms at the lattice points. Three kinds of atomic solids: network, metals, group 18. (ex: diamond, Cu, Ar)

31. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 31 Figure 10.12 Examples of Three Types of Crystalline Solids

32. Atomic solids compared Network, diamond, covalent mp= 3500 C Metallic, Cu, delocalized cov., mp = 1083 C Group 18, Ar, London, mp = -189 C Copyright©2000 by Houghton Mifflin Company. All rights reserved. 32

33. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 33 Packing in Metals Model: closest packing atoms/molecules/ions as spheres. To maximize IF forces: sphere packed as close as possible. Small spaces exist between adjacent spheres: called interstitial holes.

34. Two types of packing possible 4 hexagonal closest packed (“hcp”) resulting from aba 4 cubic closest packed (“ccp”) resulting from abca Copyright©2000 by Houghton Mifflin Company. All rights reserved. 34

35. Let’s pack a crystal hcp and ccp 1. Form a base layer of 3 sphere. 2. Place 2 nd layer to occupy dimples in layer 1. (one choice only) 3. Two choices for the third layer of spheres: –3 rd layer over 1 st layer(ABAB). Hexagonal close packing (hcp); –3 rd layer is not over 1 st layer. 4 th layer is over 1 st layer. (ABCABC. Cubic close packing (ccp).

37. Choose: which one is ccp, which one is hcp? Close Packing of Spheres

38. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 38 Figure 10.14 Hexagonal Closest Packing

39. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 39 Figure 10.15 Cubic Closest Packing

40. Structures of Solids Close Packing of Spheres Each sphere is surrounded by 12 other spheres (6 in one plane, 3 above and 3 below). Coordination number: the number of spheres directly surrounding a central sphere. If unequally sized spheres are used, the smaller spheres are placed in the interstitial holes.

41. The Indicated Sphere Has 12 Nearest Neighbors True for both ccp and hcp

42. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 42 Figure 10.15 Cubic Closest Packing

43. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 43 Figure 10.16 The Indicated Sphere Has 12 Nearest Neighbors

44. Copyright©2000 by Houghton Mifflin Compay. All rights reserved. 44 Bonding Models for Metals We can explain why metals are malleable, ductile and conduct heat/electricity Electron Sea Model: A regular array of metal cations awash in a “sea” of electrons. Band (Molecular Orbital) Model: Electrons assumed to travel around metal crystal in MOs formed from valence atomic orbitals of metal atoms.

45. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 45 Figure 10.18 The Electron Sea Model for Metals Postulates a Regular Array of Cations in a “Sea” of Valence Electrons

46. Figure 10.19 The Molecular Orbital Energy Levels Produced When Various Numbers of Atomic Orbitals Interact. 2 ao’s make 2MOs When 4 ao’s overlap, 4MOs Note: when many MO are available, “bands” become virtually continuous. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 46

47. The Band Model for Magnesium Core electrons are localized, but valence are in closely spaced Mos: conduction bands. Electrons move into empty MOs Copyright©2000 by Houghton Mifflin Company. All rights reserved. 47

48. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 48 Figure 10.21 Two Types of Alloys

49. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 49 Metal Alloys 1. Substitutional Alloy: some metal atoms replaced by others of similar size. brass = Cu/Zn Sterling silver: Ag/Cu Pewter: tin/Cu/Bi/Sb Substances that have a mixture of elements and metallic properties.

50. 50 Metal Alloys (continued) 2.Interstitial Alloy: Interstices (holes) in closest packed metal structure are occupied by small atoms. Ex: --steel = iron, carbon in the holes --increase C, reduce ductility, increase hardness and strength. Mild steel: 0.2% C, nails, chains Medium: 0.2-0.6% C: beams High: 1.5% C: springs, tools, knives

51. Metal alloys Alloy steel: mix of interstitial, C and substitutional. Ex: stainless steel Fe, C and 11% Cr. Cr forms layer of Cr oxide, prevent rust. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 51

52. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 52 Network Solids Composed of strong directional covalent bonds that are best viewed as a “giant molecule”. 4 brittle 4 may or may not conduct heat or electricity 4 carbon, silicon-based graphite, diamond, ceramics, glass

53. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 53 Figure 10.22 The Structures of Diamond and Graphite : both network solids

54. Why is diamond insulator not conductor? a)Carbon in diamond Empty MOs much higher E b)Metal: Empty MOs close in E 54

55. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 55 However, Graphite is a conductor: --each C is sp2, not sp3 like diam. --The p Orbitals in graphite form pi bonds: increase stab. layers & allow conductivity -

56. Layers in graphite Copyright©2000 by Houghton Mifflin Company. All rights reserved. 56

57. Graphite vs. Diamod Graphite: conducts, soft, strong bonding in layers, weak between. Layers slide past: good for lubricant, pencils. Density: 2.2 g/cc Diamond: does not conducts, hardest, strong bonding all around. Good for cutting Density: 3.5 g/cc Copyright©2000 by Houghton Mifflin Company. All rights reserved. 57

58. Si: the carbon of geology Copyright©2000 by Houghton Mifflin Company. All rights reserved. 58

59. Si, right under C but different No long Si-Si chains like C Si forms chains of Si-O SiO 2 = e.f. of silica, most important Not CO 2 structure, Si cannot overlap p’s w/ O. No pi bonds. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 59

60. How does Si bond with O? A network of SiO 4 tetrahedrons. No indiv. SiO 2, although this is e.f. This is quartz Copyright©2000 by Houghton Mifflin Company. All rights reserved. 60

61. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 61 Glass: melt quartz, cool rapidly: (a) a Quartz Crystal (b) a Quartz Glass Additives: see table 10.5 Ex: add B 2 O 3 to make borosilcate glass

62. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 62 Silicate Anions: Note all are based on SiO 4 tetrahedron

63. Ceramics Made from clays (contain silicates) that are hardened by firing at high T. Non-metallic: silicates bind with cations as clay is dried, trapping crystals of kaolinite. Strong, brittle, heat/chemical resistant 63

64. Semiconductors Si: Like C, large gap to empty MOs but gap is smaller, so some electrons can cross the band gap.Si: Like C, large gap to empty MOs but gap is smaller, so some electrons can cross the band gap. Si is a semiconductor.Si is a semiconductor. Conductivity is enhanced by doping with group 13 or group 15 elements. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 64

65. Silicon Crystal Doped with (a) Arsenic and (b) Boron As: 1 extra valence e - n-type semiconductor extra e - can join the conduction band  B: l less valence e - : p-type semiconductor creates a “hole” that is filled by an e - from Si. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 65

66. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 66 Figure 10.30 Energy Level Diagrams for (a) an n-Type Semiconductor and (b) a p-Type Semiconductor

67. The p-n Junction e - flow from n to p to fill “holes” p side becomes neg (b) battery with – at n and + at p. e- flow back: reverse bias, current does not flow  (c) battery other way e - flow right way: forward bias  Application:Transistors: switches : chips: iphone 67

68. Molecular Solids Ice Dry ice: CO 2 S 8 P 4 What forces between molecules in above crystals? Why is S 8 solid? Copyright©2000 by Houghton Mifflin Company. All rights reserved. 68

69. Ionic Solids High melting pt Larger Ions (anions) in hcp or ccp structure  Cations fit in the holes  3 types of holes. trig< tetra<octa trig never occupied Copyright©2000 by Houghton Mifflin Company. All rights reserved. 69

70. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 70 Figure 10.33 The Holes that Exist Among Closest Packed Uniform Spheres

71. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 71 Tetrahedral Holes in a Face-Centered Cubic Unit Cell Ex. ZnS S 2- face centered. Zn 2+ in tetrahedral holes Q: How many tetrahedral holes? How many are occupied?

72. NaCl revisited Cl - face-centered from ccp packing Na + in all octahedral holes. Q: how many octa holes in (a). Copyright©2000 by Houghton Mifflin Company. All rights reserved. 72

73. NaCl octahedral holes Note: center Na + surrounded by the 6 face-centered Cl - 73

74. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 74 Vapor Pressure... 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.

75. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 75 Figure 10.36 Behavior of a Liquid in a Closed Container

76. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 76 Figure 10.37 The Rates of Condensation and Evaporation

77. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 77 Figure 10.38 Vapor Pressure

78. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 78 Figure 10.39 The Number of Molecules in a Liquid With a Given Energy Versus Kinetic Energy at Two Temperatures

79. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 79 Figure 10.40 The Vapor Pressure of Water

80. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 80 Figure 10.42 Heating Curve for Water

81. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 81 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

82. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 82 Figure 10.43 The Vapor Pressures of Solid and Liquid Water

83. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 83 Figure 10.44 An Apparatus that Allows Solid and Liquid Water to Interact Only Through the Vapor State

84. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 84 Figure 10.45 Water in a Closed System

85. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 85 Figure 10.46 The Supercooling of Water

86. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 86 Boiling Point Constant temperature when added energy is used to vaporize the liquid. vapor pressure of liquid = pressure of surrounding atmosphere

87. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 87 Phase Diagram Represents phases as a function of temperature and pressure. critical temperature: temperature above which the vapor can not be liquefied. critical pressure: pressure required to liquefy AT the critical temperature. critical point: critical temperature and pressure (for water, T c = 374°C and 218 atm).

88. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 88 Figure 10.47 The Phase Diagram for Water

89. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 89 Figure 10.48 Diagrams of Various Heating Experiments

90. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 90 Figure 10.49 The Phase Diagram for Water

91. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 91 Figure 10.52 The Phase Diagram for Carbon Dioxide

92. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 92 Figure 10.50 A Schematic of Two Circuits Connected by a Transistor

93. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 93 Figure 10.51 The Steps for Forming a Transistor in a Crystal of Initially Pure Silicon