2. Dr. S. M. Condren Chapter 15 The Liquid State, The Solid State, and Modern Materials

3. Dr. S. M. Condren Properties of Liquids surface tension - A property of liquids arising from unbalanced molecular cohesive forces at or near the surface

4. Dr. S. M. Condren Properties of Liquids surface tension capillary action - phenomenon in which the surface of a liquid is elevated or depressed when it comes in contact with a solid

5. Dr. S. M. Condren Properties of Liquids surface tension capillary action viscosity –resistance of a fluid to flow –resistance acts against the motion of any solid object through the fluid, and also against motion of the fluid itself past stationary obstacles

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8. Compared to the average energy, those molecules which escape the surface of a liquid are lower in energy same energy higher in energy

9. Dr. S. M. Condren Phase Changes Evaporation phase change from liquid to gas Condensation phase change from gas to liquid

10. Dr. S. M. Condren Vapor Pressure vs. Temperature p vs. t( o C) exponential function as t increases, p increases

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14. Vapor Pressure vs. Temperature Clausius-Clapeyron Equation ln(P 2 /P 1 )=(  H vap /R)(1/T 1 - 1/T 2 )

15. Dr. S. M. Condren Properties of Liquids boiling point the temperature at which its vapor pressure is equal to the local atmospheric pressure normal boiling point the temperature at which its vapor pressure is equal to one atmospheric pressure

16. Dr. S. M. Condren Properties of Liquids liquid-vapor equilibirum both liquid and vapor of the liquid present in the same container uder stable conditions vapor pressure The pressure exerted by a vapor in equilibrium with its solid or liquid phase.

17. Dr. S. M. Condren Properties of Liquids enthalpy of vaporization - The amount of heat required to convert a unit mass of a liquid at its boiling point into vapor without an increase in temperature.

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21. Phase Changes Melting phase change from solid to liquid Freezing phase change from liquid to solid melting point(freezing point) temperature at which a liquid congeals into the solid state at a given pressure

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23. Phase Changes Melting and Freezing enthalpy of fusion - heat absorbed by the substance in changing its state without raising its temperature

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25. Phase Changes Liquid Crystals substance that behaves like both a liquid and a solid by applying a small electric field, certain liquid crystal substances gain the ability to rotate polarized light. These types of liquid crystals are used to construct displays used in digital watches, calculators, miniature television sets, portable computers, and other items

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27. Phase Diagram - General P T Solid Gas Liquid 1 atm mp nbp triple point critical point x sublimation point xx

28. Dr. S. M. Condren Phase Diagrams label axes label phase regions label: triple point critical point melting point boiling point sublimation point

29. Dr. S. M. Condren Critical Point The temperature and pressure at which the liquid and gaseous phases of a pure stable substance become identical. The critical temperature of a gas is the maximum temperature at which the gas can be liquefied; the critical pressure is the pressure necessary to liquefy the gas at the critical temperature.

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34. Solids Crystals X-ray Diffraction Bragg's Law

35. Dr. S. M. Condren Solids Crystals - A homogenous solid formed by a repeating, three-dimensional pattern of atoms, ions, or molecules and having fixed distances between constituent parts.

36. Dr. S. M. Condren Solids X-ray Diffraction - When an X-ray beam bombards a crystal, the atomic structure of the crystal causes the beam to scatter in a specific pattern. This phenomenon, known as X-ray diffraction, occurs when the wavelength of the X rays and the distances between atoms in the crystal are of similar magnitude.

37. Dr. S. M. Condren Solids Bragg's Law - The fundamental law of x- ray crystallography, n = 2dsin , where n is an integer, is the wavelength of a beam of x-rays incident on a crystal with lattice planes separated by distance d, and  is the Bragg angle. [After Sir William Henry Bragg and Sir William Lawrence Bragg.]

38. Dr. S. M. Condren Structure Determination

39. Dr. S. M. Condren Diffraction Conditions Solid State Resources CD-ROM Movies Chapter 4

40. Dr. S. M. Condren Diffraction Conditions

41. Dr. S. M. Condren Solids Bragg's Law n = 2d sin  wheren => order of diffraction => X-ray wavelength d => spacing between layers of atom  => angle of diffraction

42. Dr. S. M. Condren EXAMPLE What is the spacing between copper atoms if X-ray radiation of wavelength 1.54  diffracts in the second order at 58.42°? n = 2 = 1.54A  = 58.42° d = ? n = 2d sin  d = (n )/2sin  = (2*1.54A)/(2*sin(58.42°)) = 1.54A/0.852 = 1.81 

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44. Ionic Solids cations and anions form the points in the 3-D structure NaCl

45. Dr. S. M. Condren Metallic Solids atoms of the metal form the 3-D points in the structure iron copper

46. Dr. S. M. Condren Molecular Solids molecules form point in the 3-D structure sugar

47. Dr. S. M. Condren Network Covalent Solids atoms covalently bonded to the surrounding atoms in a 3-D network diamond quartz

48. Dr. S. M. Condren Lattice and Units Cells Lattices 7 types 4 most common types:cubic orthorhombic monoclinic triclinic

49. Dr. S. M. Condren Unit Cells?

50. Dr. S. M. Condren Which are Unit Cells?

51. Dr. S. M. Condren Unit Cells of Metals cubic:a = b = c  =  =  = 90° simple cubic (primitive cubic) atoms only at corners of cube body centered cubic (BCC) atoms at the corners and at the center of the body. face-centered cubic (FCC) atoms at the corners and at the center of all 6 faces, same as cubic close-packed.

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54. Number of Atoms per Unit Cell - atoms at corner of unit cell count 1/8 - atoms at center of a face count 1/2 - atoms at center of the body count 1

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56. Primitive Cubic use of an orange to show why only 1/8 atom at corners of a unit cell Solid State Resources CD-ROM Chapter 3 Movie Orange Slicing

57. Dr. S. M. Condren Number of Atoms per Unit Cell primitive cubic => 8(1/8) = 1 BCC => 8(1/8) + 1 = 2 FCC => 8(1/8) + 6(1/2) = 4

58. Dr. S. M. Condren Combinations of Elements Element CombinationLikely Structure Nonmetal and nonmetalDiscrete molecule CO 2, PCl 3, NO Metal and metalExtended (alloys) CuZn (brass), NiTi Metal and nonmetalExtended (salts) NaCl, ZnS, CaTiO 3

59. Dr. S. M. Condren Unit Cells of Compounds cubic:a = b = c  =  =  = 90° face-centered cubic (FCC) =>NaCl, LiCl, ZnS(zinc blend, S ions in FCC with Zn ions in tetrahedral holes)

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61. NaCl Stoichiometry

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64. Why is CsCl not body-centered cubic (BCC)?

65. Dr. S. M. Condren Unit Cells of Compounds orthorhombic: a  b  c  =  =  = 90° monoclinic: a  b  c  =  = 90°  > 90° triclinic: a  b  c     90°

66. Dr. S. M. Condren EXAMPLE Metallic gold crystallizes in the face-centered cubic lattice. The length of the cubic unit cell is 4.070A. What is the closest distance between gold atoms? a = 4.070  r = ? closest distance = 2r

67. Dr. S. M. Condren Face-Centered-Cubic Unit Cell d f = face diagonal r = radius of atom d f = 4r a = edge a 2 + a 2 = d f 2 2a 2 = (4r) 2 r = (a*2 1/2 )/4

68. Dr. S. M. Condren EXAMPLE Metallic gold crystallizes in the face- centered cubic lattice. The length of the cubic unit cell is 4.070A. What is the closest distance between gold atoms? a = 4.070A r = ? closest distance = 2r 4r = a2 1/2 =>r = a2 1/2 /4 r = (4.070A*1.414)/4 = 1.44A closest distance = 2(1.44A) = 2.88A

69. Dr. S. M. Condren Molecular Substances Common Properties - nonconductors of electricity when pure - insoluble in water but soluble in non-polar solvents - volatile, appreciable vapor pressure at room temperature - low melting and boiling points

70. Dr. S. M. Condren Metals Common Properties –Nonvolatile. –Insoluble in water and other common solvents.

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72. Network Covalent Substances graphite => sp 2 hybrid C, planar

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74. Network Covalent Substances diamond => sp 3 hybrid C, 3D

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76. Network Covalent Substances silicon dioxide => sp 3 Si, 4 O around each Si => sp 3 O, 4 Si around each Si

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82. Amorphous Solids (Glasses) lacking definite form no long range ordering in the structure