Intermolecular Attractions & the Properties of Liquids & Solids CHAPTER 12

1. Intermolecular Attractions & the Properties of Liquids & Solids CHAPTER 12 Chemistry: The Molecular Nature of Matter, 6th edition By Jesperson, Brady, & Hyslop REVIEW

2. CHAPTER 12 Concept Review Strength of Intermolecular Forces London Dispersion Forces Dipole-Dipole Forces Hydrogen Bonds (a type of Dipole-Dipole Force) Ion-Dipole or Ion-Induced Dipole Forces Weakest Strongest Jesperson, Brady, Hyslop. Chemistry: The Molecular Nature of Matter, 6E

3. CHAPTER 12 Concept Review Strength of Intermolecular Forces London Dispersion Forces: minimized surface area London Dispersion Forces: maximized surface area Dipole-Dipole Forces: small overall dipole moment Dipole-Dipole Forces: large overall dipole moment Hydrogen Bonds: with 1 H-bond per molecule Hydrogen Bonds: with multiple H-bonds per molecule Ion-Dipole or Ion-Induced Dipole Forces Weakest Strongest Jesperson, Brady, Hyslop. Chemistry: The Molecular Nature of Matter, 6E

4. CHAPTER 12 Concept Review Strength of Intermolecular Forces Jesperson, Brady, Hyslop. Chemistry: The Molecular Nature of Matter, 6E

7. Phase Changes = changes of physical state with temperature ( α to KE) SOLID LIQUID GAS fusion evaporation freezing condensation deposition sublimation endothermic • System absorbs energy from surrounds in the form of heat • Requires the addition of heat exothermic • System releases energy into surrounds in the form of heat or light • Requires heat to be decreased

8. HEATING CURVE gas l <--> g evaporation or vaporization ΔHvap liquid TEMPERATURE endothermic s <--> l solid fusion ΔHfus endothermic HEAT ADDED

9. Equilibrium & Phase Diagrams • T1 = 78°C • P1 = 330 atm • To increase • T2 = 100°C • The system must respond by increasing • P2 = 760 to restore equilibrium: • T is higher • Volume of liquid is lower • P of vapor higher

10. Le Chatelier’s Principle Liquid + Heat  Vapor If you increase either the liquid or the heat the reaction is driven to the right to re-establish equilibrium. Liquid + Heat  Vapor Liquid + Heat  Vapor Liquid + Heat Vapor If you increase vapor the reaction will be driven to the left to re-establish equilibrium. Liquid + Heat  Vapor

11. 3-D Simple Cubic Lattice Unit Cell Space filling model Portion of lattice—open view

12. Other Cubic Lattices Face Centered Cubic Body Centered Cubic

13. Counting Atoms in Unit Cells

14. Interpreting Diffraction Data Bragg Equation • nλ=2d sinθ • n = integer (1, 2, …) •  = wavelength of X rays • d = interplane spacing in crystal •  = angle of incidence and angle of reflectance of X rays to various crystal planes

15. Example: Using Diffraction Data X-ray diffraction measurements reveal that copper crystallizes with a face-centered cubic lattice in which the unit cell length is 362 pm. What is the radius of a copper atom expressed in picometers? This is basically a geometry problem.

16. Ex. Using Diffraction Data (cont.) Pythagorean theorem: a2 + b2 = c2 Where a = b = 362 pm sides and c = diagonal 2a2 = c2 and diagonal = 4  rCu = 512 pm rCu = 128 pm