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CHAPTER 11

CHAPTER 11. LIQUIDS AND SOLIDS. Chapter Goals. Kinetic-Molecular Description of Liquids and Solids Intermolecular Attractions and Phase Changes The Liquid State Viscosity Surface Tension Capillary Action Evaporation Vapor Pressure Boiling Points and Distillation

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CHAPTER 11

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  1. CHAPTER 11 • LIQUIDS AND SOLIDS

  2. Chapter Goals • Kinetic-Molecular Description of Liquids and Solids • Intermolecular Attractions and Phase Changes The Liquid State • Viscosity • Surface Tension • Capillary Action • Evaporation • Vapor Pressure • Boiling Points and Distillation • Heat Transfer Involving Liquids

  3. Chapter Goals The Solid State • Melting Point • Heat Transfer Involving Solids • Sublimation and the Vapor Pressure of Solids • Phase Diagrams (P versus T) • Amorphous Solids and Crystalline Solids • Structures of Crystals • Bonding in Solids • Band Theory of Metals • Synthesis Question

  4. Kinetic-Molecular Description of Liquids and Solids • 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. • They easily flow. • The intermolecular attractionsin liquids and solids are strong.

  5. gas liquid solid cool cool heat heat Kinetic-Molecular Description of Liquids and Solids • Schematic representation of the three common states of matter.

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

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

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

  9. Intermolecular Attractions and Phase Changes • Coulomb’s law determines: • The melting and boiling points of ionic compounds. • 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,CaF2 You do it! What important points must you consider?

  10. Intermolecular Attractions and Phase Changes

  11. Intermolecular Attractions and Phase Changes • Hydrogen bonding • Consider H2O a very polar molecule.

  12. Intermolecular Attractions and Phase Changes • Hydrogen bonding • Consider H2O a very polar molecule.

  13. Intermolecular Attractions and Phase Changes

  14. Intermolecular Attractions and Phase Changes • Dipole-dipole interactions • Consider BrF a polar molecule.

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

  17. Intermolecular Attractions and Phase Changes • Similar effects occur in a group of I2 molecules. The effect is shown in this movie.

  18. The Liquid State Viscosity • Viscosity is the resistanceto 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. The Liquid State • An example of viscosity of two liquids.

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

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

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

  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. The Liquid State • This is an animation of evaporation

  28. 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. 0oC20oC30oCnormal boiling point diethyl ether 185 442 647 36oC ethanol 12 44 74 78oC water 5 18 32 100oC • What are the intermolecular forces in each of these compounds? You do it!

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

  30. The Liquid State Boiling Points and Distillation • The boiling point is the temperature at which the liquid’s vapor pressure is equal to the applied pressure. • The normalboiling 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.

  31. 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.

  32. The Liquid State Heat Transfer Involving Liquids • From Chapter 1 • Example 13-2: How much heat is released by 2.00 x 102 g of H2O as it cools from 85.0oC to 40.0oC? The specific heat of water is 4.184 J/goC. • You do it!

  33. The Liquid State

  34. The Liquid State • Molar heat capacity is the amount of heat required to raise the temperature of one mole of a substance 1.00 oC. • Example 13-3: The molar heat capacity of ethyl alcohol, C2H5OH, is 113 J/moloC. How much heat is required to raise the T of 125 g of ethyl alcohol from 20.0oC to 30.0oC? 1 mol C2H5OH = 46.0 g You do it!

  35. The Liquid State

  36. 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.

  37. The Liquid State Molar heat of vaporization or DHvap • The DHvap isthe amount of heat required to change 1.00 mole of a liquid to a gas at constanttemperature. DHvaphasunits of J/mol. Molar heat of condensation • The reverse of molar heat of vaporization is the heat of condensation.

  38. The Liquid State

  39. The Liquid State • Example 13-4: How many joules of energy must be absorbed by 5.00 x 102 g of H2O at 50.0oC to convert it to steam at 120oC? 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 oC and 36.4 J/mol oC, respectively. You do it!

  40. 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 120oC.

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

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

  43. The Liquid State

  44. 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 DHvap if we know pressure at 2 T’s

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

  46. The Liquid State

  47. The Liquid State • Boiling Points of Various Kinds of Liquids GasMWBP(oC)

  48. The Liquid State

  49. The Liquid State

  50. The Liquid State

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