Accelerated Chemistry 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 Heat Transfer Involving Liquids

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

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 attractions in liquids and solids are strong.

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

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.

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.

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.

Intermolecular Attractions and Phase Changes Coulomb’s law determines: The melting and boiling points of ionic compounds. The solubility of ionic compounds. : Arrange the following ionic compounds in the expected order of increasing melting and boiling points. NaF, CaO, CaF2

Intermolecular Attractions and Phase Changes

Intermolecular Attractions and Phase Changes Hydrogen bonding Consider H2O a very polar molecule. 2 Factors Great polarity of bond Close approach of dipoles Effects Boiling Points Strong H bonds

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

Intermolecular Attractions and Phase Changes

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

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.

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

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

The Liquid State Viscosity Viscosity is the resistance to 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.

The Liquid State An example of viscosity of two liquids. One

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.

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

The Liquid State Capillary Action Capillary action is the ability of a liquid to rise (or fall) in a glass tube or other container

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

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

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

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. Insert Fig. 13-11. Have it appear (wipe left) after the last sentence.

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. 0oC 20oC 30oC normal 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!

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

Boiling Points and Distillation 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 normal boiling 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.

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.

Heat Transfer Involving Liquids The Liquid State Heat Transfer Involving Liquids From earlier 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 have done this

The Liquid State

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. 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

The Liquid State

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.

Molar heat of vaporization or DHvap Molar heat of condensation The Liquid State Molar heat of vaporization or DHvap The DHvap is the amount of heat required to change 1.00 mole of a liquid to a gas at constant temperature. DHvap has units of J/mol. Molar heat of condensation The reverse of molar heat of vaporization is the heat of condensation.

The Liquid State

STUFF Molar Heat of Fusion ice 6.02 kJ/mol Molar Heat of Vaporization liquid to vapor 40.6 kJ/mol Specific Heat of water Ice 2.03 J/g C Liquid 4.184 J/g C Steam 2.0 j/g C

The Liquid State 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 40.6 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!

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.

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

The Liquid State 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?

The Liquid State

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

The Liquid State

The Liquid State Boiling Points of Various Kinds of Liquids Gas MW BP(oC)

The Liquid State

The Liquid State

The Liquid State

The Liquid State

The Liquid State At the molecular level what happens when a species boils?

The Solid State Normal Melting Point The normal melting point is the temperature at which the solid melts (liquid and solid in equilibrium) at exactly 1.00 atm of pressure. The melting point increases as the strength of the intermolecular attractions increase.

What experimental proof do you have? The Solid State Which requires more energy? What experimental proof do you have?

Heat Transfer Involving Solids Heat of Fusion Heat of fusion is the amount of heat required to melt one gram of a solid at its melting point at constant temperature. Heat of crystallization is the reverse of the heat of fusion.

Heat Transfer Involving Solids Molar heat of fusion or Hfusion The molar heat of fusion is the amount of heat required to melt a mole of a substance at its melting point. The molar heat of crystallization is the reverse of molar heat of fusion

Heat Transfer Involving Solids Here is a summary of the heats of transformation for water.

Heat Transfer Involving Solids Calculate the amount of heat required to convert 150.0 g of ice at -10.0oC to water at 40.0oC. specific heat of ice is 2.09 J/goC

Heat Transfer Involving Solids

Sublimation and the Vapor Pressure of Solids In the sublimation process the solid transforms directly to the vapor phase without passing through the liquid phase. Solid CO2 or “dry” ice does this well.

Phase Diagrams (P versus T) Phase diagrams are a convenient way to display all of the different phase transitions of a substance. This is the phase diagram for water.

Phase Diagrams (P versus T) Compare water’s phase diagram to carbon dioxide’s phase diagram.

Amorphous Solids and Crystalline Solids Amorphous solids do not have a well ordered molecular structure. Examples of amorphous solids include waxes, glasses, asphalt. Crystalline solids have well defined structures that consist of extended array of repeating units called unit cells. Crystalline solids display X-ray diffraction patterns which reflect the molecular structure. The Bragg equation, detailed in the textbook, describes how an X-ray diffraction pattern can be used to determine the interatomic distances in crystals.

Structure of Crystals Unit cells are the smallest repeating unit of a crystal. As an analogy, bricks are repeating units for buildings. There are seven basic crystal systems.

Structure of Crystals We shall look at the three variations of the cubic crystal system. Simple cubic unit cells. The balls represent the positions of atoms, ions, or molecules in a simple cubic unit cell.

Structure of Crystals In a simple cubic unit cell each atom, ion, or molecule at a corner is shared by 8 unit cells Thus 1 unit cell contains 8(1/8) = 1 atom, ion, or molecule.

Structure of Crystals Body centered cubic (bcc) has an additional atom, ion, or molecule in the center of the unit cell. On a body centered cubic unit cell there are 8 corners + 1 particle in center of cell. 1 bcc unit cell contains 8(1/8) + 1 = 2 particles.

Structure of Crystals A face centered cubic (fcc) unit cell has a cubic unit cell structure with an extra atom, ion, or molecule in each face.

Structure of Crystals A face centered cubic unit cell has 8 corners and 6 faces. 1 fcc unit cell contains 8(1/8) + 6(1/2) = 4 particles.

Bonding in Solids Molecular Solids have molecules in each of the positions of the unit cell. Molecular solids have low melting points, are volatile, and are electrical insulators. Examples of molecular solids inlude: water, sugar, carbon dioxide, benzene

Bonding in Solids Covalent Solids have atoms that are covalently bonded to one another Some examples of covalent solids are: Diamond, graphite, SiO2 (sand), SiC

Bonding in Solids Ionic Solids have ions that occupy the positions in the unit cell. Examples of ionic solids include: CsCl, NaCl, ZnS

Bonding in Solids Metallic Solids may be thought of as positively charged nuclei surrounded by a sea of electrons. The positive ions occupy the crystal lattice positions. Examples of metallic solids include: Na, Li, Au, Ag, ……..

Bonding in Solids Compound Melting Point (oC) ice 0.0 ammonia -77.7 Variations in Melting Points for Molecular Solids What are the intermolecular forces in each solid? Compound Melting Point (oC) ice 0.0 ammonia -77.7 benzene, C6H6 5.5 napthalene, C10H8 80.6 benzoic acid, C6H5CO2H 122.4

Bonding in Solids Substance Melting Point (oC) sand, SiO2 1713 Variations in Melting Points for Covalent Solids Substance Melting Point (oC) sand, SiO2 1713 carborundum, SiC ~2700 diamond >3550 graphite 3652-3697

Bonding in Solids Variations in Melting Points for Ionic Solids Compound Melting Point (oC) LiF 842 LiCl 614 LiBr 547 LiI 450 CaF2 1360 CaCl2 772 CaBr2 730 CaI2 740

Bonding in Solids Metal Melting Point (oC) Variations in Melting Points for Metallic Solids Metal Melting Point (oC) Na 98 Pb 328 Al 660 Cu 1083 Fe 1535 W 3410

Bonding in Solids A group IVA element with a density of 11.35 g/cm3 crystallizes in a face-centered cubic lattice whose unit cell edge length is 4.95 Å. Calculate the element’s atomic weight. What is the atomic radius of this element?

Bonding in Solids Face centered cubic unit cells have 4 atoms, ions, or molecules per unit cell. Problem solution pathway: Determine the volume of a single unit cell. Use the density to determine the mass of a single unit cell. Determine the mass of one atom in a unit cell. Determine the mass of 1 mole of these atoms

Use the density to determine the mass of a unit cell. Bonding in Solids Determine the volume of a single unit cell. Use the density to determine the mass of a unit cell.

Bonding in Solids Determine the mass of one atom in the unit cell. Determine the mass of one mole of these atoms.

Bonding in Solids To determine an atomic radius requires some geometry. For simple cubic unit cells: The edge length = 2 radii

Bonding in Solids For face-centered cubic unit cells: The face diagonal = 2 x edge length. The diagonal length = 4 radii.

Bonding in Solids For body-centered cubic unit cells: The body diagonal = 3 x edge length. The diagonal length = 4 radii.

Bonding in Solids Determine the diagonal length then divide by 4 to get the atomic radius.

Band Theory of Metals Sodium’s 3s orbitals can interact to produce overlapping orbitals

Band Theory of Metals The 3s orbitals can also overlap with unfilled 3p orbitals

Band Theory of Metals Insulators have a large gap between the s and p bands. Gap is called the forbidden zone. Semiconductors have a small gap between the bands.

Synthesis Question 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 100.0oC 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%.

Synthesis Question 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 CO2. How many moles of carbon dioxide are present in the extractor?

Synthesis Question

Synthesis Question

Group Question How many CO2 molecules are there in 1.0 cm3 of the Maxwell House Coffee Company extractor? How many more CO2 molecules are there in a cm3 of the supercritical fluid in the Maxwell House extractor than in a mole of CO2 at STP?