copyright 2004 - john sayles 1 phases of matter ap review unit 3 chapters 5 and 11 problem sets #4...

Copyright 2004 - John Sayles 1

Phases of MatterPhases of Matter

AP Review Unit 3AP Review Unit 3

Chapters 5 and 11Chapters 5 and 11

Problem Sets #4 and 5Problem Sets #4 and 5

Copyright 2004 - John SaylesCopyright 2004 - John Sayles 22

Comparison of PhasesComparison of Phases

SolidSolid• Particles very slow, very closeParticles very slow, very close• Particles very strongly attracted, a la ColombParticles very strongly attracted, a la Colomb• Particles Particles LOCKEDLOCKED

LiquidsLiquids• Particles slow, closeParticles slow, close• Particles strongly attracted, a la ColombParticles strongly attracted, a la Colomb• Particles on aParticles on a LEASH LEASH

GasesGases• Particles very fast, very far apartParticles very fast, very far apart• Particles not attracted (one of the IGL assumptions)Particles not attracted (one of the IGL assumptions)• Particles Particles LIBERATEDLIBERATED


Representation of the States of Matter

Copyright © Houghton Mifflin Company. All rights reserved 11-2


Phase ChangesPhase Changes Melting (Fusion)/FreezingMelting (Fusion)/Freezing

• Can occur at any temp, but equilibrium process occurs at the Can occur at any temp, but equilibrium process occurs at the melting pointmelting point

• Involves Involves weakening/strengthening bonds between particlesweakening/strengthening bonds between particles• ∆∆HHfusionfusion= Joules/mol added to melt/removed to freeze= Joules/mol added to melt/removed to freeze• 80 cal/gram for water = 6 kJ/mol80 cal/gram for water = 6 kJ/mol

Boiling/CondensationBoiling/Condensation• Can occur at any temp, but equilibrium process occurs at the Can occur at any temp, but equilibrium process occurs at the

boiling pointboiling point• Involves Involves breaking/forming bonds between breaking/forming bonds between particlesparticles• ∆∆HHvap vap = J/mol added to boil/removed to condense= J/mol added to boil/removed to condense• 540 cal/gram for water = 40.6 kJ/mol540 cal/gram for water = 40.6 kJ/mol• Evaporation is the random process; Boiling is equilibrium processEvaporation is the random process; Boiling is equilibrium process


Factors Affecting PhaseFactors Affecting Phase Nature of the substanceNature of the substance

• Strength of bonds between particlesStrength of bonds between particles

• Mass of particlesMass of particles TemperatureTemperature

• High Temp increases KEHigh Temp increases KEaveave

• Weakens or breaks bondsWeakens or breaks bonds PressurePressure

• Only significantly affects gasesOnly significantly affects gases Melting of ice with pressure is an exceptionMelting of ice with pressure is an exception

• Boiling occurs when VP = external PBoiling occurs when VP = external P Higher external P makes boiling tougherHigher external P makes boiling tougher


Types of SolidsTypes of Solids MolecularMolecular

• Covalently bondedCovalently bonded Molecules held by weak IMF’sMolecules held by weak IMF’s Low MP’s, BP’s, ∆H’sLow MP’s, BP’s, ∆H’s

• Crystal composed of neutral moleculesCrystal composed of neutral molecules Doesn’t conduct in solid, solution, or ,meltDoesn’t conduct in solid, solution, or ,melt

• Solubility depends on polaritySolubility depends on polarity IonicIonic

• Ionically bondedIonically bonded Ions held by strong ionic bondsIons held by strong ionic bonds High MP’s, BP’s, ∆H’sHigh MP’s, BP’s, ∆H’s

• Crystal composed of charged ionsCrystal composed of charged ions Conducts in the melt or solutionConducts in the melt or solution

• Soluble in polar solventsSoluble in polar solvents


Types of Solids (continued)Types of Solids (continued) MetallicMetallic

• Metallic bondsMetallic bonds Variable strengthVariable strength Variable MP’s, etc …Variable MP’s, etc …

• Crystal composed of cations in a “sea of eCrystal composed of cations in a “sea of e--’s”’s” Conduct in solid and meltConduct in solid and melt

• Not solubleNot soluble Macromolecular (network covalent)Macromolecular (network covalent)

• Covalent bondsCovalent bonds No IMF’s; must mess with covalent bondsNo IMF’s; must mess with covalent bonds Very high MP’s, etc …Very high MP’s, etc …

• Crystal composed of neutral atomsCrystal composed of neutral atoms Doesn’t conductDoesn’t conduct

• Not solubleNot soluble


IMF’sIMF’s Dispersion (London) ForcesDispersion (London) Forces

• Caused by Caused by temporary induced dipolestemporary induced dipoles• Weakest IMF (0-2 kcal/mole)Weakest IMF (0-2 kcal/mole)• All molecules have them; only important for non-polarsAll molecules have them; only important for non-polars

Dipole ForcesDipole Forces• Caused by Caused by permanent dipolespermanent dipoles (polar molecules) (polar molecules)• 2-10 kcal/mole2-10 kcal/mole• Onl Onl polar moleculespolar molecules have them have them

Hydrogen BondsHydrogen Bonds• 10-20 kcal/mol10-20 kcal/mol• Found in molecules with Found in molecules with N, O, F attached N, O, F attached directly todirectly to H H• High performance dipole forcesHigh performance dipole forces

Small N, O, F atoms VERY small HSmall N, O, F atoms VERY small H++ ion ion Very polar bonds due to highly electroneg N, O, FVery polar bonds due to highly electroneg N, O, F


GasesGases

PressurePressure• Caused by Caused by collisionscollisions

TemperatureTemperature• Determines Determines KEKEaveave and speed of molecules and speed of molecules

• KE messes with bondsKE messes with bonds• Must be KelvinsMust be Kelvins

VolumeVolume• Determined by Determined by empty space between particlesempty space between particles• Ideal gasesIdeal gases have have no molecular volumeno molecular volume


The Gas LawsThe Gas Laws Ideal Gas LawIdeal Gas Law

• PV = nRTPV = nRT R = .0821 atm L/(mol K) = 62.4 mm Hg L/(mol K)R = .0821 atm L/(mol K) = 62.4 mm Hg L/(mol K)

• Most useful for Most useful for calculating molescalculating moles

Real Gas LawReal Gas Law• (P + a n(P + a n22/V/V22) (V - nb) = nRT) (V - nb) = nRT

• P correction accounts for drag of real IMF’sP correction accounts for drag of real IMF’s VDW constant “a” indicates strength of IMF’sVDW constant “a” indicates strength of IMF’s

• V correction accounts for real molecular volumeV correction accounts for real molecular volume VDW constant “b” indicates actual molecular volumeVDW constant “b” indicates actual molecular volume


Vapor PressureVapor Pressure Def’n: pressure of the vapor Def’n: pressure of the vapor at equilibriumat equilibrium with the with the

liquid or solidliquid or solid Depends onDepends on

• Nature of substanceNature of substance IMF’sIMF’s Molecular massMolecular mass

• TemperatureTemperature Claussius-Clapeyron equationClaussius-Clapeyron equation ln (VPln (VP11/VP/VP22) = -∆H) = -∆Hvapvap/R (1/T/R (1/T11 - 1/T - 1/T22))

BP = temp at which VP = external PBP = temp at which VP = external P• Increase T until VP = external P and/or …Increase T until VP = external P and/or …• Decrease external PDecrease external P


Boiling Point versus Molecular Weight for Hydrides


11_24

60

Boi

ling

poi

nt (

º C)

20

Molecular weight

A

160

40 140

20 120

0 100

20 80

40 60

60 40

80 20

100 0

120 20

Boi

ling

poi

nt (

º C)

2040 4060 6080 80100 100120 120

Molecular weight

B

H2O

H2S

H2Se

H2Te

NH3

CH4

SiH4

GeH4

SnH4

PH3

AsH3

SbH3

HF

HClHBr

HI


Variation of Vapor Pressure with Temperature


11_7

100

200

300

400

500

600

700

800

Vap

or p

ress

ure

(m

mH

g)

– 20 0 20 40 60 80 100

Temperature (ºC)

760

Diethyl

ether

Chloroform

Carbontetrachloride

Water


Plot of the Logarithm of Vapor Pressure versus 1/T


11_10

1.50

1.70

1.90

2.10

2.30

2.50

2.70

2.90

log

P

2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00

1/T X 103

Water

Carbontetrachloride

Diethyl ether

Chloroform


Phase DiagramsPhase Diagrams Y-axis is Y-axis is PressurePressure, X-axis is , X-axis is TempTemp Each point represents T & P where 2 phases are at Each point represents T & P where 2 phases are at

equilibriumequilibrium• One line shows all BP’sOne line shows all BP’s• One line shows all MP’sOne line shows all MP’s• One line shows all SubP’sOne line shows all SubP’s• Triple Point is only T,P where all three phases are at equilibriumTriple Point is only T,P where all three phases are at equilibrium

Critical Temp: T above which only gas existsCritical Temp: T above which only gas exists Slope of the Solid-Liquid equilibrium line depends on Slope of the Solid-Liquid equilibrium line depends on

whether solid or liquid is most densewhether solid or liquid is most dense• Slopes right for most substances (solid more dense)Slopes right for most substances (solid more dense)• Slopes left for waterSlopes left for water


Phase Diagram for Water (Not to Scale)


11_11

D

A

BC

Solid Liquid

(374º C, 218 atm)

Gas

0ºC 100ºCTemperature

1.0

Pre

ssur

e (a

tm)

(0.01ºC, 0.00603 atm)


Phase Diagrams for Carbon Dioxide (Not to Scale)

Copyright © Houghton Mifflin Company. All rights reserved 11-12A

11_12a

Solid

Triple point(–57ºC, 5.1 atm)

Liquid

Gas

Critical point(31ºC, 73 atm)

–78ºC

Temperature

1.0

Pre

ssu

re (

atm

)

A


Properties of LiquidsProperties of Liquids Vapor PressureVapor Pressure

• Depends on T, IMF’s, massDepends on T, IMF’s, mass VolatilityVolatility

• Depends on IMF’s and massDepends on IMF’s and mass Surface TensionSurface Tension

• Depends on IMF’sDepends on IMF’s

• Affects “wetting” ability, formation of bubblesAffects “wetting” ability, formation of bubbles ViscosityViscosity

• Depends on IMF’s and massDepends on IMF’s and mass

• Motor oil composed of very heavy moleculesMotor oil composed of very heavy molecules

copyright 2004 - john sayles 1 phases of matter ap review unit 3 chapters 5 and 11 problem sets #4...

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