Chapter 10 – Liquids & Solids. Intra- and Inter- molecular forces a. intramolecular forces a. intramolecular forces bonds bonds within molecule within

Chapter 10 – Liquids & Chapter 10 – Liquids & SolidsSolids

Intra- and Inter- molecular Intra- and Inter- molecular forcesforces

a. intramolecular forces a. intramolecular forces bondsbonds withinwithin molecule molecule ionicionic or or covalentcovalent


Intermolecular ForcesIntermolecular Forces BetweenBetween molecules molecules Causes solids or liquids (condensed Causes solids or liquids (condensed

states of matter) to form as molecules states of matter) to form as molecules bond togetherbond together

431 kJ/mol

16 kJ/mol


Determines many important properties Determines many important properties of substances:of substances:

statestate boiling and melting pointsboiling and melting points vapor pressurevapor pressure

Ion-Dipole ForcesIon-Dipole Forces

Results from the Results from the electrostaticelectrostatic attraction of an ion and a dipoleattraction of an ion and a dipole

Dipole – Dipole ForcesDipole – Dipole Forces

Found in Found in polarpolar molecules molecules Molecules with dipoles line up so that Molecules with dipoles line up so that

the the positive endpositive end of one molecule is of one molecule is close to the close to the negative endnegative end of of another molecule another molecule

The attraction The attraction weakensweakens as the as the distance between molecules distance between molecules increasesincreases



Dipole – dipole attractionsDipole – dipole attractions

Much Much weaker weaker than than covalentcovalent or or ionicionic forces forces

But does explain why polar liquids are But does explain why polar liquids are more soluble in polar liquids than in more soluble in polar liquids than in non-polar liquidsnon-polar liquids It takes 2000 mL of HIt takes 2000 mL of H22O to dissolve 1 mL O to dissolve 1 mL

of CClof CCl44 It takes 50 mL of HIt takes 50 mL of H22O to dissolve 1 mL of O to dissolve 1 mL of

CHCH22ClCl22

London dispersion forcesLondon dispersion forces

Found in non-polar moleculesFound in non-polar molecules Instantaneous Instantaneous dipolesdipoles can be produced can be produced

in non-polar molecules when electrons in non-polar molecules when electrons are are not distributed evenlynot distributed evenly

When an instantaneous When an instantaneous dipoledipole occurs occurs in one molecule, dipoles are in one molecule, dipoles are inducedinduced in in the neighboring molecules. the neighboring molecules.



Weaker than Weaker than dipoledipole attractions and attractions and short-livedshort-lived

Increase with Increase with molecular sizemolecular size Larger molecules have Larger molecules have greatergreater London- London-

dispersion forces dispersion forces Larger molecules have Larger molecules have more electronsmore electrons, ,

creating a greater opportunity for creating a greater opportunity for uneven electron distributionuneven electron distribution

Hydrogen BondingHydrogen BondingHydrogen BondingHydrogen Bonding

Hydrogen bond is an especially strong Hydrogen bond is an especially strong dipole-dipole force, as shown by the dipole-dipole force, as shown by the trend in boiling points of polar trend in boiling points of polar moleculesmolecules

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H-bonding is observed for HF, HH-bonding is observed for HF, H22O, O, NHNH33, but not CH, but not CH44

Conditions for occurrence:Conditions for occurrence: H attached to a small, highly H attached to a small, highly

electronegative element in one moleculeelectronegative element in one molecule Small, highly electronegative element Small, highly electronegative element

with one or more unshared electron pairs with one or more unshared electron pairs in the other moleculein the other molecule

Observed for the elements: Observed for the elements: F, O, N (rarely S and Cl)F, O, N (rarely S and Cl)


Which of the following molecules will Which of the following molecules will hydrogen-bond in the pure hydrogen-bond in the pure substance?substance?

HH22OO

HH22SeSe

HFHF

HBrHBr

NHNH33

PFPF33

Hydrogen Bonding in Hydrogen Bonding in Liquid WaterLiquid Water

Hydrogen Bonding in Hydrogen Bonding in Liquid WaterLiquid Water

H points at the H points at the electron pair on the electron pair on the atom in the other atom in the other moleculemolecule

In liquid water, each In liquid water, each water molecule is water molecule is surrounded by an surrounded by an average of 4 other average of 4 other water molecules; water molecules; structure is not rigid.structure is not rigid.

Longer than covalent Longer than covalent bond.bond.


Average of 4 Average of 4 hydrogen bonds in hydrogen bonds in liquid waterliquid water

Figure 10.2

Fluoride ion is Fluoride ion is hydrogen-bonded hydrogen-bonded to water in solutionto water in solution


Molecules Molecules hydrogen-hydrogen-bond to bond to themselvethemselves or to s or to other other moleculesmolecules..

Figure 10.2

Structure of Ice Structure of Ice Structure of Ice Structure of Ice

The water The water molecules in molecules in ice are fixed ice are fixed into a into a tetrahedral tetrahedral arrangement arrangement as a result of as a result of hydrogen hydrogen bonding. Open bonding. Open structure structure makes ice less makes ice less dense than dense than water.water.

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Structure of IceStructure of IceStructure of IceStructure of Ice

The open The open structure ofstructure ofice leavesice leaveschannels ofchannels ofempty spaceempty spacethrough thethrough thecrystals.crystals.

Identify Predominant Identify Predominant Type of Intermolecular Type of Intermolecular

ForcesForces

Identify Predominant Identify Predominant Type of Intermolecular Type of Intermolecular

ForcesForces

What types of intermolecular forces What types of intermolecular forces are observed for each of the are observed for each of the following molecules?following molecules?(A type of molecule may have more (A type of molecule may have more than one.)than one.)

HH22OO HFHF

HBrHBr NHNH33

PFPF33 CHCH33OHOH

FF22 COCO

COCO22 NN22

Intermolecular ForcesIntermolecular ForcesIntermolecular ForcesIntermolecular Forces

Strengths of Strengths of Intermolecular ForcesIntermolecular Forces

Strengths of Strengths of Intermolecular ForcesIntermolecular Forces

Intermolecular forces generally Intermolecular forces generally increase in strength asincrease in strength asLondon < Dipole-Dipole < H-bonding < London < Dipole-Dipole < H-bonding <

Ion-Dipole < Ionic BondingIon-Dipole < Ionic Bonding The forces are cumulative. All The forces are cumulative. All

molecules have London forces. Polar molecules have London forces. Polar molecules have both London and molecules have both London and dipole-dipole forces. ...dipole-dipole forces. ...

Trends in Intermolecular Trends in Intermolecular ForcesForces

Trends in Intermolecular Trends in Intermolecular ForcesForces

Which member of each pair has the larger Which member of each pair has the larger intermolecular forces? (we will learn later that this intermolecular forces? (we will learn later that this affects things such as boiling point, heat of affects things such as boiling point, heat of vaporization)vaporization)

CHCH33OH, CHOH, CH33SHSH

FF22, Kr, Kr

FF22, CO, CO

CO, HFCO, HF

COCO22, NH, NH33

NN22, NH, NH33

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Structural models of liquids Structural models of liquids

More complex than models for solids More complex than models for solids or gases for two reasons or gases for two reasons Liquids have strong intermolecular Liquids have strong intermolecular

forces forces Liquids have significant molecular Liquids have significant molecular

motion motion

Surface TensionSurface Tension

ResistanceResistance of a liquid to increase its of a liquid to increase its surface area surface area

For the surface area of a liquid to For the surface area of a liquid to increase, molecules would have to increase, molecules would have to move up to the surface move up to the surface This would require internal molecules to This would require internal molecules to

pull awaypull away from their surrounding from their surrounding molecules, going molecules, going againstagainst the the intermolecular forces intermolecular forces

Surface TensionSurface Tension An An unevenuneven distribution of forces distribution of forces

exists on exists on surfacesurface molecules molecules Molecules on the surface only Molecules on the surface only

experience intermolecular attractions experience intermolecular attractions with molecules with molecules below and to the sidebelow and to the side of them of them

Molecules below the surface experience Molecules below the surface experience intermolecular attractions with intermolecular attractions with molecules molecules in all directionsin all directions

This causes molecules on the surface to This causes molecules on the surface to be be pulled to the interiorpulled to the interior, giving the , giving the surface a surface a spherical shapespherical shape


Liquids with Liquids with greatergreater intermolecular intermolecular forces have a forces have a greatergreater surface surface tension tension

Would you expect a polar liquid to Would you expect a polar liquid to have a greater surface tension than a have a greater surface tension than a nonpolar liquid? Why or why not? nonpolar liquid? Why or why not?


Surface TensionSurface TensionSurface TensionSurface Tension

How does a water strider stay on the How does a water strider stay on the top of the water? Why does the top of the water? Why does the needle float?needle float?

Surface TensionSurface TensionSurface TensionSurface Tension

Why does soap make the paper clip Why does soap make the paper clip sink?sink?

Capillary ActionCapillary Action

RisingRising of a liquid in a of a liquid in a narrow tubenarrow tube Occurs when the molecules in the Occurs when the molecules in the

container have container have polar bondspolar bonds The polar bonds in the container The polar bonds in the container

attract the liquid, causing the liquid attract the liquid, causing the liquid to try to creep up the sides of the to try to creep up the sides of the container, which stretches the container, which stretches the surface of the liquid surface of the liquid


The liquid tries to balance the The liquid tries to balance the attraction attraction between liquid between liquid moleculesmolecules (cohesive forces) and the (cohesive forces) and the attraction between the attraction between the liquid and liquid and the containerthe container (adhesive forces) (adhesive forces)

This causes the liquid to This causes the liquid to pull itself pull itself upup the tube the tube


Explains the shape of the meniscus Explains the shape of the meniscus formed by a liquid in a tube formed by a liquid in a tube

The meniscus of water is The meniscus of water is concaveconcave because the attractions between the because the attractions between the waterwater molecules and the molecules and the glassglass molecules are greater than the molecules are greater than the attractions attractions between two waterbetween two water molecules molecules


What would you expect the meniscus What would you expect the meniscus to look like for a liquid in which the to look like for a liquid in which the internal (liquid to liquid) attractions internal (liquid to liquid) attractions are stronger than the attractions are stronger than the attractions between the liquid and the between the liquid and the container? container?

Capillary ActionCapillary ActionCapillary ActionCapillary Action

Which forces in each Which forces in each

system are greater?system are greater?

ViscosityViscosity

A liquid's A liquid's resistance to flowresistance to flow Can be compared to the "Can be compared to the "thicknessthickness" "

of a liquid of a liquid Thicker liquids are Thicker liquids are more viscousmore viscous

Maple syrup has a greater viscosity than Maple syrup has a greater viscosity than water water

ViscosityViscosity

Intermolecular forces and molecular Intermolecular forces and molecular complexity both contribute to the complexity both contribute to the viscosity of a liquid viscosity of a liquid

As intermolecular forces As intermolecular forces increaseincrease, , viscosity viscosity increasesincreases

As molecular complexity As molecular complexity increasesincreases, , viscosity viscosity increasesincreases

ViscosityViscosity

Why do you think that viscosity Why do you think that viscosity increases when the intermolecular increases when the intermolecular forces or molecular complexity forces or molecular complexity increases? increases?

Liquid PhenomenonLiquid Phenomenon

In what way do you think that In what way do you think that viscosity, capillary action, and viscosity, capillary action, and surface tension are related? surface tension are related?

In other words, if a liquid had a high In other words, if a liquid had a high viscosity, what would you predict viscosity, what would you predict about its surface tension and about its surface tension and capillary action? capillary action?

Phase ChangesPhase ChangesPhase ChangesPhase Changes Physical states of a Physical states of a

substance can co-substance can co-exist under a exist under a variety of variety of conditions of conditions of pressure and pressure and temperature.temperature.

Phases: different Phases: different forms (gas, liquid, forms (gas, liquid, solid, etc.) of a solid, etc.) of a substance that co-substance that co-exist in a exist in a heterogeneous heterogeneous system.system.

Phase ChangesPhase ChangesPhase ChangesPhase Changes

Transitions between phases Transitions between phases are called phase changesare called phase changes evaporation: liquid evaporation: liquid gas gas

(reverse = condensation)(reverse = condensation)

melting: solid melting: solid liquid liquid (reverse = freezing)(reverse = freezing)

sublimation: solid sublimation: solid gas gas (reverse = deposition)(reverse = deposition)

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What are the phase What are the phase changes?changes?

What are the phase What are the phase changes?changes?

Heat of VaporizationHeat of VaporizationHeat of VaporizationHeat of Vaporization

Is evaporation exothermic or Is evaporation exothermic or endothermic?endothermic?

Heat of VaporizationHeat of VaporizationHeat of VaporizationHeat of Vaporization

HHvapvap = energy needed to evaporate 1 = energy needed to evaporate 1 mol of liquid at constant temperature mol of liquid at constant temperature

Energy used to overcome Energy used to overcome intermolecular forces during intermolecular forces during evaporationevaporation

Larger molecules have higher Larger molecules have higher HHvapvap

because of higher London forcesbecause of higher London forces Polar Polar HHvapvap > nonpolar > nonpolar HHvapvap if if

molecular size is similarmolecular size is similar H-bonded H-bonded HHvapvap > polar > polar HHvapvap

Heat of FusionHeat of FusionHeat of FusionHeat of Fusion

Generally heat of fusion (enthalpy of Generally heat of fusion (enthalpy of fusion) is less than heat of fusion) is less than heat of vaporization:vaporization: it takes more energy to completely it takes more energy to completely

separate molecules, than partially separate molecules, than partially separate them.separate them.

FreezingFreezingFreezingFreezing

Cooling liquids decreases their Cooling liquids decreases their kinetic energykinetic energy

When intermolecular forces become When intermolecular forces become greater than kinetic energy, the greater than kinetic energy, the liquid freezes and becomes solid.liquid freezes and becomes solid.

Freezing point = temperature at Freezing point = temperature at which solid and liquid are in a state which solid and liquid are in a state of equilibriumof equilibrium

Normal freezing point = f.p. at Normal freezing point = f.p. at pressure of 1 atm.pressure of 1 atm.

Phase DiagramsPhase DiagramsPhase DiagramsPhase Diagrams

Phase diagram: plot of pressure vs. Phase diagram: plot of pressure vs. temperature summarizing all temperature summarizing all equilibria between phases.equilibria between phases.

Given a temperature and pressure, Given a temperature and pressure, phase diagrams tell us which phase phase diagrams tell us which phase will exist.will exist.

lines: equilibrium between two lines: equilibrium between two phasesphases

areas: only one phase is stableareas: only one phase is stable triple point (confluence of 3 lines): triple point (confluence of 3 lines):

equilibrium between three phasesequilibrium between three phases

Phase Diagram FeaturesPhase Diagram FeaturesPhase Diagram FeaturesPhase Diagram Features

Features of a phase diagram:Features of a phase diagram: Triple point: temperature and pressure Triple point: temperature and pressure

at which all three phases are in at which all three phases are in equilibrium. equilibrium.

Vapor-pressure curve: generally as Vapor-pressure curve: generally as pressure increases, temperature pressure increases, temperature increases.increases.

Critical point: critical temperature and Critical point: critical temperature and pressure for the gas.pressure for the gas.

Melting point curve: as pressure Melting point curve: as pressure increases, the solid phase is favored if increases, the solid phase is favored if the solid is more dense than the liquid.the solid is more dense than the liquid.

Normal melting point: melting point at 1 Normal melting point: melting point at 1 atm.atm.

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Generic Phase DiagramGeneric Phase DiagramGeneric Phase DiagramGeneric Phase Diagram

Shows Shows conditions conditions of stability of stability of phases of phases and and conditions conditions of of equilibriuequilibriumm

Figure 10.45

Phase Diagram of WaterPhase Diagram of WaterPhase Diagram of WaterPhase Diagram of Water

Phase Diagram of Carbon Phase Diagram of Carbon DioxideDioxide

Phase Diagram of Carbon Phase Diagram of Carbon DioxideDioxide

Slope of the solid-liquid Slope of the solid-liquid boundary lineboundary line

If negative, the liquid is more dense If negative, the liquid is more dense than the solid and vice-versathan the solid and vice-versa

The Wide World of Solids The Wide World of Solids A concept map to organize how A concept map to organize how

solids are classified solids are classified Solids

Amorphous

Crystalline

IonicMolecularAtomic

Metallic Network Group 8A

Amorphous solids Amorphous solids

Highly Highly disordereddisordered Described as a Described as a solution frozen in solution frozen in

placeplace Example: Glass Example: Glass

Crystalline solids Crystalline solids

Highly Highly orderedordered arrangement arrangement Represented as a Represented as a latticelattice Unit cellUnit cell - - smallest repeating unitsmallest repeating unit

of a lattice of a lattice

Unit CellsUnit Cells Three types of unit cells Three types of unit cells Simple cubicSimple cubic - a cube with atoms or - a cube with atoms or

molecules at each of the corners molecules at each of the corners Body-centered cubicBody-centered cubic - a cube with - a cube with

atoms or molecules at each of the atoms or molecules at each of the corners and one atom or molecule in corners and one atom or molecule in the center of the cube. the center of the cube.

Face-centered cubicFace-centered cubic - a cube with - a cube with atoms or molecules at each of the atoms or molecules at each of the corners and atoms or molecules in corners and atoms or molecules in the center of each side of the cube the center of each side of the cube

Crystalline SolidsCrystalline Solids

Structures determined by using X-ray Structures determined by using X-ray diffraction diffraction This technology was helpful in This technology was helpful in

determining the structure of DNA! determining the structure of DNA! Three main types of crystalline solids Three main types of crystalline solids

exist: ionic, molecular, and atomic. exist: ionic, molecular, and atomic.

Ionic SolidsIonic Solids Stable Stable High High melting pointmelting point Brittle Brittle Held together by Held together by ionic bondsionic bonds NonconductorsNonconductors when solid when solid What do you think would happen to the What do you think would happen to the

conductivity of an ionic solid if it were conductivity of an ionic solid if it were melted or dissolved in water? Why? melted or dissolved in water? Why?

Ionic SolidsIonic Solids

Similar structural model to that of Similar structural model to that of metallic solidsmetallic solids

Ions represented as Ions represented as hard sphereshard spheres Ions are packed Ions are packed closely togetherclosely together

and arranged in a way to maximize and arranged in a way to maximize attraction and attraction and minimize repulsionminimize repulsion

Ionic SolidsIonic Solids

Example: NaClExample: NaCl Chlorine ions are arranged in a face-Chlorine ions are arranged in a face-

centered cubic closest packed structurecentered cubic closest packed structure Sodium ions fill in the spaces in between Sodium ions fill in the spaces in between

the chlorine ions.the chlorine ions.

Molecular solids Molecular solids

Strong Strong covalent bondingcovalent bonding within the within the molecules molecules

Molecules held to each other by Molecules held to each other by intermolecular forcesintermolecular forces

Generally have Generally have low melting pointslow melting points Generally Generally nonconductorsnonconductors of heat of heat

and electric current and electric current

Molecular Solids Molecular Solids Molecules are held together by Molecules are held together by

intermolecular forcesintermolecular forces Polar molecules are held together by Polar molecules are held together by

dipole forcesdipole forces Nonpolar molecules are held together Nonpolar molecules are held together

by by London-dispersion forcesLondon-dispersion forces Intermolecular forces are generally Intermolecular forces are generally

greatergreater when the molecules are polar when the molecules are polar

Atomic solids Atomic solids

Consist of atoms at each of the Consist of atoms at each of the lattice points in the crystallattice points in the crystal

Can be divided into Metallic, Can be divided into Metallic, Network, and Group 8A atomic solids Network, and Group 8A atomic solids

Metallic solids Metallic solids High High thermalthermal conductivity conductivity High High electricalelectrical conductivity conductivity Malleable Malleable Ductile Ductile Range from low melting point and Range from low melting point and

soft to high melting point and brittle soft to high melting point and brittle Strong, Strong, non-directionalnon-directional covalent covalent

bonding bonding

The Closest Packing Model The Closest Packing Model

Metal atoms are represented as Metal atoms are represented as hard hard spheresspheres

In a metallic solid, atoms are In a metallic solid, atoms are arranged in arranged in layerslayers, packed as close , packed as close together as possible, in a way that together as possible, in a way that the space between atoms is the space between atoms is minimized minimized

The Closest Packing Model The Closest Packing Model

Hexagonal closest packed structure Hexagonal closest packed structure Atoms arranged in the Atoms arranged in the ABA ABA form form Creates a Creates a hexagonalhexagonal unit cell unit cell Examples: Magnesium and Zinc Examples: Magnesium and Zinc

The Closest Packing ModelThe Closest Packing Model

Cubic closest packed structure (figure Cubic closest packed structure (figure 10.15) 10.15)

Atoms arranged in the Atoms arranged in the ABCABC form form Creates a Creates a face-centeredface-centered unit cell unit cell Examples: Silver and Copper Examples: Silver and Copper

Metallic SolidsMetallic Solids

Not all metallic solids have one of Not all metallic solids have one of these two structuresthese two structures e.g. alkali metalse.g. alkali metals Body-centered cubic unit cellBody-centered cubic unit cell Eight nearest neighbors (less dense)Eight nearest neighbors (less dense)

Bonding Models for Metallic Bonding Models for Metallic Solids Solids

Electron Sea Model Electron Sea Model Represented as Represented as metal cationsmetal cations

surrounded by a sea of surrounded by a sea of electronselectrons Similar to Thomson's Plum Pudding Similar to Thomson's Plum Pudding

model of the atom model of the atom

Bonding Models for Metallic Bonding Models for Metallic Solids Solids

Molecular Orbital Model Molecular Orbital Model The valence orbitals of the metals The valence orbitals of the metals

atoms hybridize in a way that allows atoms hybridize in a way that allows valence electrons to move valence electrons to move throughout the entire crystal throughout the entire crystal

Metal Alloys Metal Alloys

Alloy - a substance containing a Alloy - a substance containing a mixture of elementsmixture of elements and having and having metallic properties metallic properties

Metal AlloysMetal Alloys

Substitutional alloys - within a metal Substitutional alloys - within a metal crystal, metal atoms are removed crystal, metal atoms are removed and replaced with atoms of similar and replaced with atoms of similar size size

Example: Brass Example: Brass Cu

Cu

Cu Cu

Cu Cu

Zn Zn

Zn

Metal AlloysMetal Alloys Interstitial alloys - small atoms fill in Interstitial alloys - small atoms fill in

the holes in the metal crystal the holes in the metal crystal Example: Steel Example: Steel

Can make the metal stronger by Can make the metal stronger by creating directional bonds between the creating directional bonds between the metal atoms and the smaller atoms metal atoms and the smaller atoms

Fe Fe Fe Fe Fe Fe

Fe Fe Fe Fe FeC C

C

Network Atomic Solids Network Atomic Solids Brittle Brittle Poor Poor conductorsconductors (thermal and (thermal and

electrical) electrical) Very Very high melting pointhigh melting point Strong, Strong, directionaldirectional covalent bonds covalent bonds Often referred to as "Often referred to as "giant moleculesgiant molecules" " Have Have non-latticenon-lattice type structures type structures

Carbon in diamond form is arranged in Carbon in diamond form is arranged in tetrahedrals connected together tetrahedrals connected together

Changes of State Changes of State

VaporizationVaporization (evaporation) - (evaporation) - molecules of a liquid escape the molecules of a liquid escape the liquid's surface and form a gas liquid's surface and form a gas

Heat of VaporizationHeat of Vaporization ( ( HHvapvap) - the ) - the energy that is required to vaporize energy that is required to vaporize one mole of liquid at one atmosphere one mole of liquid at one atmosphere of pressure of pressure

Changes of StateChanges of State

CondensationCondensation - vapor (gas) - vapor (gas) molecules going back into the liquid molecules going back into the liquid phase phase

SublimationSublimation - solid molecules - solid molecules escaping into the gas phase without escaping into the gas phase without going through the liquid phase going through the liquid phase Can you think of an example of Can you think of an example of

sublimation? sublimation?

Vapor PressureVapor Pressure

Vapor pressureVapor pressure - the pressure that - the pressure that is exerted by a vapor (gas), in a is exerted by a vapor (gas), in a closed systemclosed system

Measured when the Measured when the rate of rate of evaporationevaporation equals the equals the rate of rate of condensationcondensation

Vapor Pressure and Vapor Pressure and Evaporation RateEvaporation Rate

When the vapor pressure is When the vapor pressure is largelarge, a , a large number of the liquid molecules large number of the liquid molecules are taking part in the are taking part in the evaporation/condensationevaporation/condensation equilibrium equilibrium

As the vapor pressure As the vapor pressure increasesincreases, the , the rate of evaporation rate of evaporation increasesincreases. . More of the molecules are in the gas phase More of the molecules are in the gas phase

Vapor Pressure and Vapor Pressure and Intermolecular ForcesIntermolecular Forces

The size of intermolecular forces has The size of intermolecular forces has the greatest effect on vapor pressure the greatest effect on vapor pressure

As the intermolecular forces As the intermolecular forces increaseincrease, the vapor pressure , the vapor pressure decreasesdecreases

Why do you think that increasing Why do you think that increasing intermolecular forces decreases the intermolecular forces decreases the vapor pressure? vapor pressure?

Vapor Pressure and Molar Vapor Pressure and Molar MassMass

Molar mass also affects the vapor Molar mass also affects the vapor pressure pressure

As the molar mass As the molar mass increasesincreases, the , the vapor pressure vapor pressure decreasesdecreases

Vapor Pressure and Vapor Pressure and TemperatureTemperature

Vapor pressure increases with Vapor pressure increases with temperature temperature

As the temperature As the temperature increasesincreases, more , more molecules will have enough energy molecules will have enough energy to escape. to escape.

Vapor Pressure and Vapor Pressure and TemperatureTemperature

The relationship between vapor The relationship between vapor pressure and temperature is non-linear pressure and temperature is non-linear and can be represented by the and can be represented by the following equation following equation

ln (Pln (Pvapvap) = - ) = - HHvapvap 1 + C 1 + C

R T R T

PPvapvap = vapor pressure H = vapor pressure Hvapvap = heat of = heat of vaporization T = temperature in K vaporization T = temperature in K R = R =

universal gas constant C = constantuniversal gas constant C = constant

Comparing Vapor PressuresComparing Vapor Pressures

This equation can be rearranged to This equation can be rearranged to compare vapor pressure at two compare vapor pressure at two different temperatures different temperatures

ln Pln PT1T1vapvap = = HHvapvap 1 - 1 1 - 1

PPT2T2vapvap RR T T22 T T11

The Heating Curve The Heating Curve

Time with continuous energy input

Tem

pera

ture

Solid

Liquid and Solid Liquid

Gas and Liquid

Gas

Phase Change = No change in

temperature

Heating CurvesHeating Curves

During a phase change, the During a phase change, the temperature remains constant even temperature remains constant even though heat is being added though heat is being added continually continually

If heat is still being added, why does If heat is still being added, why does the temperature not increase during the temperature not increase during a phase change? a phase change?

More State Changes More State Changes

Heat of FusionHeat of Fusion ( ( HHfusfus) - the energy ) - the energy required to convert a solid to a liquidrequired to convert a solid to a liquid

Melting point and boiling point are Melting point and boiling point are determined by the vapor pressure of determined by the vapor pressure of the substance the substance

Melting PointMelting Point

The point at which the The point at which the vapor vapor pressure of the liquidpressure of the liquid equals the equals the vapor pressure of the solidvapor pressure of the solid when when the total pressure equals one the total pressure equals one atmosphere atmosphere

Melting PointMelting Point

Liquids and solids have characteristic Liquids and solids have characteristic vapor pressure at specific vapor pressure at specific temperatures and pressures temperatures and pressures

When a substance is in solid form, When a substance is in solid form, the temperature and pressure the temperature and pressure conditions do not favor the existence conditions do not favor the existence of the substance in the liquid phase of the substance in the liquid phase

Melting Point Melting Point

As the temperature is raised, the As the temperature is raised, the vapor pressure of the solid increases vapor pressure of the solid increases

When the vapor pressure of the solid When the vapor pressure of the solid increases to the point that it has the increases to the point that it has the same vapor pressure that a liquid same vapor pressure that a liquid would have under those conditions, would have under those conditions, this is the melting point this is the melting point

Boiling PointBoiling Point

The point at which the The point at which the vapor vapor pressurepressure equals the pressure of the equals the pressure of the environmentenvironment

This means that when the This means that when the atmospheric pressure is below one atmospheric pressure is below one atmosphere, liquids will boil at a atmosphere, liquids will boil at a lower temperaturelower temperature

Strange PhenomenaStrange Phenomena

Supercooling - when a liquid is cooled Supercooling - when a liquid is cooled below the melting pointbelow the melting point and and remains a liquid remains a liquid Occurs when the liquid is allowed to cool Occurs when the liquid is allowed to cool

without being disturbed, causing the without being disturbed, causing the molecules to not be ordered enough to molecules to not be ordered enough to form a solid form a solid

Temperature raises back up to melting Temperature raises back up to melting point when solid begins to formpoint when solid begins to form

Strange PhenomenaStrange Phenomena

Superheating - when a liquid is heated Superheating - when a liquid is heated above the boiling pointabove the boiling point and remains and remains a liquid a liquid Can occur when a liquid is heated too Can occur when a liquid is heated too

quickly quickly The pressure in the liquid is greater than The pressure in the liquid is greater than

the pressure in the atmosphere preventing the pressure in the atmosphere preventing bubbles from forming bubbles from forming

Temperature drops back down to Temperature drops back down to boiling point when gas begins to formboiling point when gas begins to form

Phase diagram Phase diagram Shows the relationship between Shows the relationship between

phase, temperature, and pressure for phase, temperature, and pressure for a given substance a given substance

Pre

ssure

Solid

Liquid

Gas

Temperature

Triple Point

Critical Point

Triple pointTriple point

The temperature and pressure at The temperature and pressure at which which solid, liquid, and gassolid, liquid, and gas can all can all exist simultaneously exist simultaneously

This is the point at which the solid This is the point at which the solid and liquid have the and liquid have the same vapor same vapor pressurepressure

Usually very close to the Usually very close to the melting melting pointpoint

Critical TemperatureCritical Temperature

temperature above which the vapor temperature above which the vapor cannot be liquefied, regardless of cannot be liquefied, regardless of the pressure applied.the pressure applied.

Critical PressureCritical Pressure

the pressure required to liquefy the the pressure required to liquefy the vapor at critical temperature. vapor at critical temperature.

Critical pointCritical point

Point at which the critical Point at which the critical temperature and critical pressure temperature and critical pressure coincide.coincide.

The temperature and pressure at The temperature and pressure at which the vapor can no longer be which the vapor can no longer be liquefied liquefied The vapor passes through a fluid phase The vapor passes through a fluid phase

before returning to the liquid state before returning to the liquid state

Meaning of the line Meaning of the line segmentssegments

The different line segments relate to The different line segments relate to the equilibrium points between the equilibrium points between phases at the specific temperatures phases at the specific temperatures and pressures.and pressures.

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Chapter 10 – Liquids & Solids. Intra- and Inter- molecular forces a. intramolecular forces a. intramolecular forces bonds bonds within molecule within