ch11.pptx
- 1. 1 Intermolecular Forces and Liquids and Solids Chapter 11 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
- 2. 2 A phase is a homogeneous part of the system in contact with other parts of the system but separated from them by a well- defined boundary. 2 Phases Solid phase - ice Liquid phase - water
- 3. 3 Intermolecular Forces Intermolecular forces are attractive forces between molecules. Intramolecular forces hold atoms together in a molecule. Intermolecular vs Intramolecular • 41 kJ to vaporize 1 mole of water (inter) • 930 kJ to break all O-H bonds in 1 mole of water (intra) Generally, intermolecular forces are much weaker than intramolecular forces. “Measure” of intermolecular force boiling point melting point DHvap DHfus DHsub
- 4. 4 Intermolecular Forces Dipole-Dipole Forces Attractive forces between polar molecules Orientation of Polar Molecules in a Solid
- 5. 5 Intermolecular Forces Ion-Dipole Forces Attractive forces between an ion and a polar molecule Ion-Dipole Interaction
- 6. 6 in solution Interaction Between Water and Cations
- 7. 7 Intermolecular Forces Dispersion Forces Attractive forces that arise as a result of temporary dipoles induced in atoms or molecules ion-induced dipole interaction dipole-induced dipole interaction
- 8. 8 Induced Dipoles Interacting With Each Other
- 9. 9 Intermolecular Forces Dispersion Forces Continued Polarizability is the ease with which the electron distribution in the atom or molecule can be distorted. Polarizability increases with: • greater number of electrons • more diffuse electron cloud Dispersion forces usually increase with molar mass.
- 10. 10 S What type(s) of intermolecular forces exist between each of the following molecules? HBr HBr is a polar molecule: dipole-dipole forces. There are also dispersion forces between HBr molecules. CH4 CH4 is nonpolar: dispersion forces. SO2 SO2 is a polar molecule: dipole-dipole forces. There are also dispersion forces between SO2 molecules.
- 11. 11 Intermolecular Forces Hydrogen Bond The hydrogen bond is a special dipole-dipole interaction between they hydrogen atom in a polar N-H, O-H, or F-H bond and an electronegative O, N, or F atom. A H…B A H…A or A & B are N, O, or F
- 12. 12 Hydrogen Bond HCOOH and water
- 13. 13 Why is the hydrogen bond considered a “special” dipole-dipole interaction? Decreasing molar mass Decreasing boiling point
- 14. 14 Properties of Liquids Surface tension is the amount of energy required to stretch or increase the surface of a liquid by a unit area. Strong intermolecular forces High surface tension
- 15. 15 Properties of Liquids Cohesion is the intermolecular attraction between like molecules Adhesion is an attraction between unlike molecules Adhesion Cohesion
- 16. 16 Properties of Liquids Viscosity is a measure of a fluid’s resistance to flow. Strong intermolecular forces High viscosity
- 17. 17 Density of Water Maximum Density 40C Ice is less dense than water Water is a Unique Substance 3-D Structure of Water
- 18. 18 A crystalline solid possesses rigid and long-range order. In a crystalline solid, atoms, molecules or ions occupy specific (predictable) positions. An amorphous solid does not possess a well-defined arrangement and long-range molecular order. A unit cell is the basic repeating structural unit of a crystalline solid. lattice point Unit Cell Unit cells in 3 dimensions At lattice points: • Atoms • Molecules • Ions
- 19. 19 Seven Basic Unit Cells
- 20. 20 Three Types of Cubic Unit Cells
- 21. 21 Arrangement of Identical Spheres in a Simple Cubic Cell
- 22. 22 Arrangement of Identical Spheres in a Body-Centered Cubic Cell
- 23. 23 Shared by 8 unit cells Shared by 4 unit cells A Corner Atom, a Edge-Centered Atom and a Face-Centered Atom Shared by 2 unit cells
- 24. 24 Number of Atoms Per Unit Cell 1 atom/unit cell (8 x 1/8 = 1) 2 atoms/unit cell (8 x 1/8 + 1 = 2) 4 atoms/unit cell (8 x 1/8 + 6 x 1/2 = 4)
- 25. 25 Relation Between Edge Length and Atomic Radius
- 26. 26 Closet Packing: Hexagonal and Cubic hexagonal cubic
- 28. 28 When silver crystallizes, it forms face-centered cubic cells. The unit cell edge length is 409 pm. Calculate the density of silver. d = m V V = a3 = (409 pm)3 = 6.83 x 10-23 cm3 4 atoms/unit cell in a face-centered cubic cell m = 4 Ag atoms 107.9 g mole Ag x 1 mole Ag 6.022 x 1023 atoms x = 7.17 x 10-22 g d = m V 7.17 x 10-22 g 6.83 x 10-23 cm3 = = 10.5 g/cm3
- 29. 29 An Arrangement for Obtaining the X-ray Diffraction Pattern of a Crystal.
- 30. 30 Extra distance = BC + CD = 2d sinq = nl (Bragg Equation) Reflection of X rays from Two Layers of Atoms.
- 31. 31 X rays of wavelength 0.154 nm are diffracted from a crystal at an angle of 14.17o. Assuming that n = 1, what is the distance (in pm) between layers in the crystal? nl = 2d sin q n = 1 q = 14.17o l = 0.154 nm = 154 pm d = nl 2sinq = 1 x 154 pm 2 x sin14.17 = 314.0 pm
- 32. 32 Types of Crystals Ionic Crystals • Lattice points occupied by cations and anions • Held together by electrostatic attraction • Hard, brittle, high melting point • Poor conductor of heat and electricity CsCl ZnS CaF2
- 33. 33 Types of Crystals Covalent Crystals • Lattice points occupied by atoms • Held together by covalent bonds • Hard, high melting point • Poor conductor of heat and electricity diamond graphite carbon atoms
- 34. 34 Types of Crystals Molecular Crystals • Lattice points occupied by molecules • Held together by intermolecular forces • Soft, low melting point • Poor conductor of heat and electricity water benzene
- 35. 35 Types of Crystals Metallic Crystals • Lattice points occupied by metal atoms • Held together by metallic bonds • Soft to hard, low to high melting point • Good conductors of heat and electricity Cross Section of a Metallic Crystal nucleus & inner shell e- mobile “sea” of e-
- 36. 36 Crystal Structures of Metals
- 38. 38 An amorphous solid does not possess a well-defined arrangement and long-range molecular order. A glass is an optically transparent fusion product of inorganic materials that has cooled to a rigid state without crystallizing Crystalline quartz (SiO2) Non-crystalline quartz glass
- 39. 39 Chemistry In Action: High-Temperature Superconductors MgB2
- 40. 40 Chemistry In Action: And All for the Want of a Button white tin grey tin T < 13 0C stable weak
- 42. 42 T2 > T1 Effect of Temperature on Kinetic Energy
- 43. 43 The equilibrium vapor pressure is the vapor pressure measured when a dynamic equilibrium exists between condensation and evaporation H2O (l) H2O (g) Rate of condensation Rate of evaporation = Dynamic Equilibrium
- 45. 45 Molar heat of vaporization (DHvap) is the energy required to vaporize 1 mole of a liquid at its boiling point. ln P = - DHvap RT + C Clausius-Clapeyron Equation P = (equilibrium) vapor pressure T = temperature (K) R = gas constant (8.314 J/K•mol) Vapor Pressure Versus Temperature
- 46. 46 Alternate Forms of the Clausius-Clapeyron Equation At two temperatures or
- 47. 47 The boiling point is the temperature at which the (equilibrium) vapor pressure of a liquid is equal to the external pressure. The normal boiling point is the temperature at which a liquid boils when the external pressure is 1 atm.
- 48. 48 The critical temperature (Tc) is the temperature above which the gas cannot be made to liquefy, no matter how great the applied pressure. The critical pressure (Pc) is the minimum pressure that must be applied to bring about liquefaction at the critical temperature.
- 49. 49 The Critical Phenomenon of SF6 T < Tc T > Tc T ~ Tc T < Tc
- 50. 50 H2O (s) H2O (l) The melting point of a solid or the freezing point of a liquid is the temperature at which the solid and liquid phases coexist in equilibrium Solid-Liquid Equilibrium
- 51. 51 Molar heat of fusion (DHfus) is the energy required to melt 1 mole of a solid substance at its freezing point.
- 52. 52 Heating Curve
- 53. 53 H2O (s) H2O (g) Molar heat of sublimation (DHsub) is the energy required to sublime 1 mole of a solid. DHsub = DHfus + DHvap ( Hess’s Law) Solid-Gas Equilibrium
- 54. 54 A phase diagram summarizes the conditions at which a substance exists as a solid, liquid, or gas. Phase Diagram of Water
- 55. 55 Phase Diagram of Carbon Dioxide At 1 atm CO2 (s) CO2 (g)
- 56. 56 Effect of Increase in Pressure on the Melting Point of Ice and the Boiling Point of Water
- 57. 57 Chemistry In Action: Ice Skating
- 58. 58 Chemistry In Action: Liquid Crystals