CHAPTER 13 n Liquids and Solids Copyright

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CHAPTER 13 n Liquids and Solids Copyright © 2000 by Harcourt, Inc Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt Inc, 6277 Sea Harbor Drive, Orlando, Florida 32887 -6777 1 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Chapter Goals n n n Kinetic-Molecular Description of Liquids & Solids Intermolecular Attractions & Phase Changes Properties of Liquids – Viscosity, Surface Tension, Capillary Action – Evaporation, Vapor Pressure, – Boiling Points & Distillation, Heat transfer Properties of Solids – Melting Points, Heat Transfer – Sublimation & Vapor Pressure – Phase Diagrams, Amorphous & Crystalline Solids – Crystal Structures, Bonding in Solids, Band Theory Synthesis Question 2 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Kinetic-Molecular Description of Liquids & Solids n Solids & liquids are condensed states – – n Liquids & gases are fluids – n atoms, ions, molecules are close to one another highly incompressible easily flow Intermolecular attractions in liquids & solids are strong 3 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Kinetic-Molecular Description of Liquids & Solids strengths of interactions among particles & n degree of ordering of particles Gases< Liquids < Solids n Miscible liquids diffuse into one another n – n they are soluble in each other for example: – – water/alcohol gasoline/motor oil 5 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Kinetic-Molecular Description of Liquids & Solids n Immiscible liquids do not diffuse into each other – n they are insoluble in each other for example: – – water/oil water/cyclohexane 6 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Intermolecular Attractions and Phase Changes n Ion-ion interactions – force of attraction between two oppositely charged ions is determined by Coulomb’s law 7 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Intermolecular Attractions and Phase Changes n Coulomb’s law & the attraction energy determine: – – n melting & 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. Na. F, Ca. O, Ca. F 2 you do it What important points must you consider? 9 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Liquid State n Viscosity - resistance to flow water vs. molasses you buy oil for your car based on this property Ostwald viscometer used to measure this property 16 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Liquid State Surface Tension - measure of the unequal attractions that occur at the surface of a liquid n molecules at surface are attracted unevenly n – – water bugs floating razor blades 17 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Liquid State Capillary Action - ability of a liquid to rise (or fall) in a glass tube n cohesive forces - hold liquids together n adhesive forces - forces between a liquid another surface n – – capillary rise implies adhesive > cohesive capillary fall implies cohesive > adhesive 18 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Liquid State n Vapor Pressure – n pressure exerted by a liquid’s vapor on its surface at equilibrium Vap. Press. (torr) for 3 Liquids 0 o. C 20 o. C 30 o. C diethyl ether 185 442 647 n ethanol 12 44 74 n water 5 18 32 n Norm. B. P. 36 o. C 78 o. C 100 o. C 22 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Liquid State n Boiling Points & Distillation – – n boiling point is temperature at which the liquid’s vapor pressure is equal to applied pressure normal boiling point is boiling point @ 1 atm distillation is a method we use to separate mixtures of liquids based on their differences in boiling points 24 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Liquid State n Distillation – – 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. 25 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Liquid State n Heat Transfer Involving Liquids – from Chapter 1 Example 13 -2: How much heat is released by 200 g of H 2 O as it cools from 85. 0 o. C to 40. 0 o. C? The specific heat of water is 4. 184 J/go. C. you do it 26 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Liquid State molar heat capacity - amount of heat required to raise the T of one mole of a substance one degree C n Example 13 -3: The molar heat capacity of ethyl alcohol, C 2 H 5 OH, is 113 J/molo. C. How much heat is required to raise the T of 125 g of ethyl alcohol from 20. 0 o. C to 30. 0 o. C? 1 mol C 2 H 5 OH = 46. 0 g n you do it 28 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Liquid State n energy associated with changes of state heat of vaporization amount of heat required to change 1 g of a liquid substance to a gas at constant T units of J/g heat of condensation reverse of heat of vaporization 30 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Liquid State molar heat of vaporization or DHvap amount of heat required to change 1 mol of a liquid to a gas at constant T units of J/mol molar heat of condensation reverse of molar heat of vaporization 31 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Liquid State n Example 13 -4: How many joules of energy must be absorbed by 500 g of H 2 O at 50. 0 o. C to convert it to steam at 120 o. C? The molar heat of vaporization of water is 40. 7 k. J/mol and the molar heat capacities of liquid water and steam are 75. 3 J/mol o. C and 36. 4 J/mol o. C, respectively. 33 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Liquid State 2 nd let’s calculate the energy required to boil the water 3 rd let’s calculate the heat required to heat steam from 100 to 120 o. C 36 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Liquid State n Example 13 -5: If 45. 0 g of steam at 140 o. C is slowly bubbled into 450 g of water at 50. 0 o. C in an insulated container, can all the steam be condensed? you do it 38 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Liquid State n 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 42 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Liquid State n Example 13 -6: Arrange the following substances in order of increasing boiling points. C 2 H 6, NH 3, Ar, Na. Cl, As. H 3 you do it 53 Copyright © 2000 by Harcourt, Inc. All rights reserved.

The Solid State n Normal Melting Point – – T at which the solid melts (liquid and solid in equilibrium) at 1 atm of pressure melting point increases as intermolecular attractions increase 55 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Heat Transfer Involving Solids n heat of fusion amount of heat required to melt one gram of a solid at its melting point at constant T heat of crystallization reverse of heat of fusion 56 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Heat Transfer Involving Solids molar heat of fusion amount of heat required to melt a mole of a substance at its melting point molar heat of crystallization reverse of molar heat of fusion 57 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Heat Transfer Involving Solids n Example 11 -7: Calculate the amount of heat required to convert 150. 0 g of ice at -10. 0 o. C to water at 40. 0 o. C. specific heat of ice is 2. 09 J/go. C you do it 59 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Amorphous & Crystalline Solids n Amorphous solids do not have a well ordered structure paraffin, glasses n Crystalline solids have well defined structures that consist of extended array of repeating units give X-ray difraction patterns see Bragg equation in book 64 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Bonding in Solids n Molecular Solids – – – molecules occupy unit cells low melting points, volatile & insulators examples: n water, sugar, carbon dioxide, benzene 71 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Bonding in Solids n Metallic Solids – – – positively charged nuclei surrounded by a sea of electrons positive ions occupy lattice positions examples: n Na, Li, Au, Ag, ……. . 74 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Bonding in Solids Variations in Melting Points n Molecular Solids Compound Melting Point (o. C) ice 0 ammonia -77. 7 benzene, C 6 H 6 5. 5 napthalene, C 10 H 8 80. 6 benzoic acid, C 6 H 5 CO 2 H 122. 4 n 75 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Bonding in Solids Covalent Solids Substance sand, Si. O 2 carborundum, Si. C diamond graphite n Melting Point (o. C) 1713 ~2700 >3550 3652 -3697 76 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Bonding in Solids Ionic Solids Compound Li. F Li. Cl Li. Br Li. I Ca. F 2 Ca. Cl 2 Ca. Br 2 Ca. I 2 n Melting Point (o. C) 842 614 547 450 1360 772 730 740 77 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Unit Cell Problem n A group IVA element with a density of 11. 35 g/cm 3 crystallizes in a face-centered cubic lattice whose unit cell edge length is 4. 95 A. Calculate the element’s atomic weight. What is the atomic radius of this element? 79 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Synthesis Question n Maxwell House Coffee Company decaffeinates its coffee beans using an extractor that is 7. 0 feet in diameter and 70. 0 feet long. Supercritical carbon dioxide at a pressure of 300. 0 atm and temperature of 100. 00 C is passed through the stainless steel extractor. The extraction vessel contains 100, 000 pounds of coffee beans soaked in water until they have a water content of 50%. 88 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Synthesis Question n This process removes 90% of the caffeine in a single pass of the beans through the extractor. Carbon dioxide that has passed over the coffee is then directed into a water column that washes the caffeine from the supercritical CO 2. How many moles of carbon dioxide are present in the extractor? 89 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Group Question n How many CO 2 molecules are there in 1. 0 cm 3 of the Maxwell House Coffee Company extractor? How many more CO 2 molecules are there in a cm 3 of the supercritical fluid in the Maxwell House extractor than in a mole of CO 2 at STP? 92 Copyright © 2000 by Harcourt, Inc. All rights reserved.

Chapter Goals Kinetic-Molecular Description of Liquids & Solids n Intermolecular Attractions & Phase Changes n Properties of Liquids n – – – n Viscosity, Surface Tension, Capillary Action Evaporation, Vapor Pressure, Boiling Points & Distillation, Heat transfer – – Melting Points, Heat Transfer Sublimation & Vapor Pressure Phase Diagrams, Amorphous & Crystalline Solids Crystal Structures, Bonding in Solids, Band Theory Properties of Solids 93 Copyright © 2000 by Harcourt, Inc. All rights reserved.