Liquids & SolidsLiquids & Solids

Chapter 13

Heat of Fusion/VaporizationHeat of Fusion/Vaporization

HH22OO(s)(s) ----> H ----> H22OO(l) (l) HHfusionfusion = 6.02 kj/mol = 6.02 kj/mol

HH22OO(l)(l) ----> H ----> H22OO(g) (g) H Hvaporizationvaporization = 40.6 kj/mol = 40.6 kj/mol

From the From the H Hoo values above, which two states values above, which two states are most similar?are most similar?

How do the attractive forces between the How do the attractive forces between the molecules compare in these two states to molecules compare in these two states to the third state? the third state?

Liquids & SolidsLiquids & Solids

The liquid and solid states are considered The liquid and solid states are considered to be the condensed states. to be the condensed states.

Liquids & solids have much higher Liquids & solids have much higher densities than gases and are not densities than gases and are not compressible.compressible.

Three States of MatterThree States of Matter

Some Properties of a LiquidSome Properties of a Liquid

Surface TensionSurface Tension: The resistance to an increase in its : The resistance to an increase in its surface area (surface area (polar moleculespolar molecules). ). A sphere has the A sphere has the maximum volume for the minimum surface area.maximum volume for the minimum surface area.

Some Properties of a LiquidSome Properties of a Liquid

Capillary ActionCapillary Action: Spontaneous rising of a liquid : Spontaneous rising of a liquid in a narrow tube. in a narrow tube.

Viscosity: Resistance to flow (molecules with large intermolecular forces).

Some Properties of a LiquidSome Properties of a Liquid

Cohesive forces exist between molecules of a Cohesive forces exist between molecules of a liquid. Adhesive forces exist between the liquid. Adhesive forces exist between the liquid and its container.liquid and its container.

Water & Its Phase ChangesWater & Its Phase Changes

Water is the most common liquid--covering Water is the most common liquid--covering about 70% of the earth’s surface. about 70% of the earth’s surface.

Water is necessary for life, moderates the Water is necessary for life, moderates the earth’s climate, a means of transportation, earth’s climate, a means of transportation, and cools many industrial processes.and cools many industrial processes.

Pure water is colorless, odorless, tasteless, Pure water is colorless, odorless, tasteless, freezes at 0 freezes at 0 ooC and boils at 100C and boils at 100 o oC at 1 atm.C at 1 atm.

Normal Melting/Freezing PointNormal Melting/Freezing Point

The temperature at which a solid melts or freezes at 1 The temperature at which a solid melts or freezes at 1 atm pressure--0 atm pressure--0 ooC for water.C for water.

Molecules break loose from lattice points and solid Molecules break loose from lattice points and solid changes to liquid. (changes to liquid. (Temperature is constant as Temperature is constant as melting occurs.)melting occurs.)

vapor pressure of solid = vapor pressure of liquidvapor pressure of solid = vapor pressure of liquid

Normal Boiling PointNormal Boiling Point

The boiling temperature of a liquid at one atmosphere The boiling temperature of a liquid at one atmosphere pressure--100 pressure--100 ooC for water.C for water.

Constant temperatureConstant temperature when added energy is used to when added energy is used to vaporize the liquid.vaporize the liquid.

vapor pressure of liquid = pressure ofvapor pressure of liquid = pressure of surrounding atmospheresurrounding atmosphere

Figure 13.3: Figure 13.3: Both liquid Both liquid water and water and gaseous water gaseous water contain Hcontain H22O O

moleculesmolecules

Boiling PointBoiling Point

What effect does altitude have on boiling What effect does altitude have on boiling point? point?

Where on earth would have the highest Where on earth would have the highest boiling point?boiling point?

Where on earth would have the lowest boiling Where on earth would have the lowest boiling point? point?

Higher altitude--lower b.p.

Dead Sea

Top of Mt. Everest--70 oC

Freezing of WaterFreezing of Water

When water freezes, it expands about 1/9th in When water freezes, it expands about 1/9th in volume. This causes water pipes and volume. This causes water pipes and engine blocks to burst when frozen.engine blocks to burst when frozen.

The density of ice is less than water and, The density of ice is less than water and, therefore, ice floats. If ice were more dense therefore, ice floats. If ice were more dense than water, lakes and rivers would freeze than water, lakes and rivers would freeze from the bottom up and aquatic life could from the bottom up and aquatic life could not survive.not survive.

Physical Changes & Energy Physical Changes & Energy ChangesChanges

EndothermicEndothermic

MeltingMelting

BoilingBoiling

Exothermic

CondensingCondensing

FreezingFreezing

Changes of state (melting, freezing, boiling,& condensing) are constant temperatureprocesses!!!!!

Heats of Fusion & VaporizationHeats of Fusion & Vaporization

The molar heat of fusion of ice is 6.02 kJ/mol.The molar heat of fusion of ice is 6.02 kJ/mol.

Hfusion = 6.02 kJ/mol

The molar heat of vaporization of water is The molar heat of vaporization of water is 40.6 kJ/mol at 100 40.6 kJ/mol at 100 ooC.C.

Hvaporization = 40.6 kJ/mol

Heating curve for water.Q = (ms t)ice + m Hf + (ms t) water + m Hv + (mst)steam

Q = KE & PE + PE + KE & PE + PE + PE & KE

Calculating Energy ChangesCalculating Energy Changes

Calculate the amount of energy required to melt 8.5 g Calculate the amount of energy required to melt 8.5 g of ice at 0 of ice at 0 ooC. C.

Q = mQ = mHHfusionfusion

Q = (8.5g HOH)(1mol/18.02g HOH)(6.02kJ/mol) Q = (8.5g HOH)(1mol/18.02g HOH)(6.02kJ/mol)

Q = 2.8 kJQ = 2.8 kJ

Calculating Energy ChangesCalculating Energy ChangesLiquid toLiquid to GasGas

Calculate the energy (in kJ) required to heat 25g of Calculate the energy (in kJ) required to heat 25g of liquid water from 25 liquid water from 25 ooC to 100 C to 100 ooC and change it to C and change it to steam at 100 steam at 100 ooC. The specific heat (s) of water is C. The specific heat (s) of water is 4.18 J/gC4.18 J/gCoo..

Q = msQ = mst + mHvaporization

Q = (25g)(4.18 J/gCo)(75 Co)(1kJ/1000J) + (25g)(1mol/18.02g)(40.6kJ/mol)

Q = 7.8 kJ + 57 kJ

Q = 65 kJ

Calculating Energy ChangesCalculating Energy ChangesSolid toSolid to GasGas

Calculate the energy (in kJ) required to melt 15g of Calculate the energy (in kJ) required to melt 15g of ice at 0 ice at 0 ooC, heat the water to 100 C, heat the water to 100 ooC, and C, and vaporize it to steam at 100 vaporize it to steam at 100 ooC. C.

Q = mHfusion + mst + mHvaporization

Q = (15g)(1mol/18.02g)(6.02kJ/mol) + (15g)(4.18 J/gCo)(100 Co)(1kJ/1000J) +

(15g)(1mol/18.02g)(40.6kJ/mol)

Q = 5.0 kJ + 6.3 kJ + 34 kJ

Q = 45 kJ

Types of BondingTypes of Bonding

Intramolecular Intramolecular

• within the moleculewithin the molecule

•covalent bondingcovalent bonding

•ionic bondingionic bonding

IntermolecularIntermolecular

•between moleculesbetween molecules

•dipole-dipole forcesdipole-dipole forces

•hydrogen bonding hydrogen bonding

•London Dispersion ForcesLondon Dispersion Forces

When ice changes to liquid and then to vapor, the intramolecular forces (covalent bonds) stay intact, only the weaker hydrogen bonds between molecules weakenand break. These are, therefore, physical changes.

Intermolecular ForcesIntermolecular Forces

Forces between (rather than within) molecules.Forces between (rather than within) molecules.

- dipole-dipole attractiondipole-dipole attraction: molecules with dipoles : molecules with dipoles orient themselves so that “+” and “orient themselves so that “+” and “” ends of ” ends of the dipoles are close to each other. (1 % as strong the dipoles are close to each other. (1 % as strong as covalent or ionic.)as covalent or ionic.)

- hydrogen bondshydrogen bonds: dipole-dipole attraction in : dipole-dipole attraction in which hydrogen is bound to a highly which hydrogen is bound to a highly electronegative atom. (electronegative atom. (F, O, NF, O, N))

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AttractionRepulsion

(a)

(b)

+– +–

+

–

+

–

–+

+

–

+

–

–

+–

+– +

Electrostatic interaction of two polar molecules.

The polar water molecule and hydrogen bonds among water molecules.

10_210

– 100

0

100

– 200

Bo

ilin

g p

oin

t ( °C

)

Period

2 3 4 5

H2 O

Group 6A

Group 7A

Group 5A

Group 4A

HF

NH 3

CH4

SiH4

GeH4

SnH4

HI

SbH3

H2Te

H2SH2Se

HClAsH3

HBr

PH3

The boiling points of the covalent hydrides of the elements in Groups 4A, 5A, 6A, & 7A. The highboiling points of HOH, NH3, HF is due to hydrogenbonding.

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Atom A Atom B

No polarization

Atom A Atom B

Instantaneous dipole on atom Ainduces a dipole on atom B

Atom A Atom B

(a)

+–

+– +–

No polarization

Instantaneous dipole on molecule Ainduces a dipole on molecule B

(b)

Molecule A Molecule B

Molecule A Molecule B

Molecule A Molecule B

H H H H+ +

+ +

+ +

+ +

+ +

+–+–

+–

H H H H

H H H H

Instantaneous and induced dipole moments between nonpolar molecules -- London Dispersion Forces. LDF forces are both weak and short-lived.

London Dispersion ForcesLondon Dispersion ForcesAlso Known As Induced DipolesAlso Known As Induced Dipoles

Size of the London Dispersion Force depends on the Size of the London Dispersion Force depends on the number of electrons and shapes of moleculesnumber of electrons and shapes of molecules

– the larger the molar mass, the larger the the larger the molar mass, the larger the induced dipoleinduced dipole

+

----

- -- --

-

+

----

- -- --

-

++

++

---

--

-------

--

-

++

++

---

--

-------

--

-

London Dispersion ForcesLondon Dispersion Forces

- relatively weakrelatively weak forces that exist among forces that exist among noble gas atoms and nonpolar molecules. noble gas atoms and nonpolar molecules. (Ar, C(Ar, C88HH1818))

- caused by caused by instantaneous dipoleinstantaneous dipole, in which , in which electron distribution becomes asymmetrical.electron distribution becomes asymmetrical.

- the ease with which electron “cloud” of an the ease with which electron “cloud” of an atom can be distorted is called atom can be distorted is called polarizabilitypolarizability..

Vapor PressureVapor Pressure

Liquid justpoured intoopen container,little vapor Evaporation faster

than CondensationEvaporation as fast as Condensation

Equilibrium

Vapor PressureVapor Pressure

. . . is the pressure of the vapor present . . . is the pressure of the vapor present at at equilibriumequilibrium with its liquid.with its liquid.

. . . is determined principally by the size of . . . is determined principally by the size of the intermolecular forces in the liquid.the intermolecular forces in the liquid.

. . . increases significantly with temperature.. . . increases significantly with temperature.

Volatile liquidsVolatile liquids have high vapor pressures.have high vapor pressures.

Vapor PressureVapor Pressure

Low boiling pointLow boiling point

• high vapor pressure. high vapor pressure.

• weak intermolecular forces.weak intermolecular forces.

Low vapor pressureLow vapor pressure

• high molar masses.high molar masses.

• strong intermolecular forces.strong intermolecular forces.

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T1

Kinetic energy(a)

Num

ber

of m

ole

cule

sw

ith a

giv

en e

nerg

y Energy neededto overcomeintermolecular forces in liquid

T2

Kinetic energy(b)

Num

ber

of m

ole

cule

sw

ith a

giv

en e

nerg

y Energy neededto overcomeintermolecular forces in liquid

Boltzman Distribution -- number of molecules ina liquid with a given energy versus kinetic energy at two different temperatures.

Rate of Evaporation & High Rate of Evaporation & High Vapor PressureVapor Pressure

Liquids evaporate more rapidly and have a Liquids evaporate more rapidly and have a high vapor pressure when the liquid:high vapor pressure when the liquid:

1. has weak intermolecular forces.1. has weak intermolecular forces.

2. is made up of lighter molecules.2. is made up of lighter molecules.

3. is at a high temperature.3. is at a high temperature.

Vapor PressureVapor Pressure

Which of the following pairs have the highest Which of the following pairs have the highest vapor pressure?vapor pressure?

1. HOH1. HOH(l) (l) or CHor CH33OHOH(l)(l)

2. CH2. CH33OHOH(l)(l) or CH or CH33CHCH22CHCH22CHCH22OHOH(l)(l)

Why?

SublimationSublimation

•Change of a solid Change of a solid directly to a vapor directly to a vapor without passing through without passing through the liquid state. the liquid state.

•IodineIodine

•Dry IceDry Ice

•Moth BallsMoth Balls

Types of SolidsTypes of Solids

Crystalline SolidsCrystalline Solids: highly regular : highly regular arrangement of their components [arrangement of their components [table salt table salt (NaCl), pyrite (FeS(NaCl), pyrite (FeS22))].].

Amorphous solidsAmorphous solids: considerable disorder in : considerable disorder in their structures (their structures (glassglass).).

Representation of Components Representation of Components in a Crystalline Solidin a Crystalline Solid

LatticeLattice: A 3-dimensional system of : A 3-dimensional system of points designating the centers of points designating the centers of components (atoms, ions, or molecules) components (atoms, ions, or molecules) that make up the substance.that make up the substance.

Representation of Components Representation of Components in a Crystalline Solidin a Crystalline Solid

Unit CellUnit Cell: The smallest repeating unit of : The smallest repeating unit of the lattice.the lattice.

- simple cubic -- 1 atom/cellsimple cubic -- 1 atom/cell

- body-centered cubic -- 2 atoms/cellbody-centered cubic -- 2 atoms/cell

- face-centered cubic -- 4 atoms/cellface-centered cubic -- 4 atoms/cell

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Simple cubic

Body-centered cubic

Face-centered cubic

(c)

(b)

(a)

Unit cell Lattice Example

Poloniummetal

Uraniummetal

Goldmetal

Three cubic unit cells and the correspondinglattices.

Types of Crystalline SolidsTypes of Crystalline Solids

Atomic SolidAtomic Solid: contains atoms at the lattice : contains atoms at the lattice points (points (diamonddiamond) -- variable melting points.) -- variable melting points.

Ionic SolidIonic Solid: contains : contains ionsions at the points of the at the points of the lattice that describe the structure of the solid lattice that describe the structure of the solid ((NaClNaCl) -- high melting points, strong ) -- high melting points, strong electrostatic forces between + & - ions.electrostatic forces between + & - ions.

Molecular SolidMolecular Solid: discrete : discrete covalently bonded covalently bonded molecules at each of its lattice points (molecules at each of its lattice points (sucrose, sucrose, iceice) -- low melting points, weak attraction.) -- low melting points, weak attraction.

Metallic Molecular Ionic Atomic Networks

malleable & ductile brittle & weak, or soft & waxy solids

hard & brittle very hard

Usually high MP MP < 300°C MP > 300°C MP > 1000°C

High BP Low BP Very high BP Very high BP

High Hvap Low Hvap, Hfusion

High Hvap, Hfusion Very high Hvap, Hfusion

high density low density medium density medium density

good conductor insulator good electrical conductor when molten or dissolved in water

very insulating very unreactive

soluble in other metals

solubility varies often soluble in water

dissolve in very few things

Crystalline SolidsCrystalline Solids

10_216

= Cl

= Na

Sodium chloride

(b)

= H2O= CDiamond Ice

(a) (c)

Three crystalline solids -- a) atomic solid, b) ionicsolid, and c) molecular solid.

The properties of solids are determined primarily bythe nature of the forces that hold the solid together.

Molecular SolidsMolecular Solids

• molecular units at each lattice position.molecular units at each lattice position.

• strong covalent bonding within molecules.strong covalent bonding within molecules.

• relatively weak forces relatively weak forces betweenbetween molecules. molecules.

• London Dispersion Forces -- COLondon Dispersion Forces -- CO22, I, I22, P, P44, & S, & S88..

• Hydrogen Bonding -- HHydrogen Bonding -- H22O, NHO, NH33, & HF., & HF.

Figure 13.16: (Left) Sulfur crystals contain SFigure 13.16: (Left) Sulfur crystals contain S88 molecules. molecules.

(Right) White phosphorus contains P(Right) White phosphorus contains P44 molecules. molecules.

Network SolidsNetwork Solids

Composed of strong directional Composed of strong directional covalent covalent bonds bonds that are best viewed as a “giant that are best viewed as a “giant molecule”.molecule”.

- brittlebrittle

- do not conduct heat or electricitydo not conduct heat or electricity

- carbon, silicon-basedcarbon, silicon-based

graphite, diamond, ceramics, glassgraphite, diamond, ceramics, glass

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Diamond(a)

Network solid structure of diamond.

Bonding Models for MetalsBonding Models for Metals

Metals are malleable, ductile, good Metals are malleable, ductile, good conductors of heat and electricity, have high conductors of heat and electricity, have high melting points, and are durable. The melting points, and are durable. The bonding in metals is bonding in metals is strongstrong but but nondirectionalnondirectional..

Bonding Models for MetalsBonding Models for Metals

Electron Sea ModelElectron Sea Model: A regular array of : A regular array of metals in a “sea” of electrons. The cations metals in a “sea” of electrons. The cations are mutually attracted to the valence are mutually attracted to the valence electrons--this attraction holds the metal electrons--this attraction holds the metal together.together.

The mobile electrons can conduct heat and The mobile electrons can conduct heat and electricity and the cations are fairly easily electricity and the cations are fairly easily moved--making the metal malleable & moved--making the metal malleable & ductile.ductile.

Electron Sea ModelElectron Sea ModelAtomic Solids that are made of metal atomsAtomic Solids that are made of metal atoms

– metal atoms release their valence electronsmetal atoms release their valence electrons

– metal cations fixed in a “sea” of mobile metal cations fixed in a “sea” of mobile electronselectrons

– Leads to strong attractions that are non-Leads to strong attractions that are non-directionaldirectional

e-

e- e-

e-

e-

e-

e-

e-

e-

e-

e-

e-

e-

e-

e-

e-

+ + + + + + + + +

+ + + + + + + + +

+ + + + + + + + +

Metal AlloysMetal Alloys

1.1. Substitutional AlloySubstitutional Alloy: some metal atoms : some metal atoms replacedreplaced by others of similar size. by others of similar size.

brass = Cu/Znbrass = Cu/Zn

Substances that have a mixture of elements and Substances that have a mixture of elements and metallic properties.metallic properties.

Metal AlloysMetal Alloys(continued)(continued)

2.2. Interstitial AlloyInterstitial Alloy: : Interstices (holes) Interstices (holes) in in closest packed metal structure are occupied closest packed metal structure are occupied by by smallsmall atoms. atoms.

steel = iron + carbonsteel = iron + carbon

3.3. Both typesBoth types: : Alloy steels Alloy steels contain a mix of contain a mix of substitutional (Cr, Mo) and interstitial substitutional (Cr, Mo) and interstitial (Carbon) alloys.(Carbon) alloys.

Substitutional Alloy

Interstitial Alloy

SteelsSteels

Pure iron is relatively soft, ductile, and Pure iron is relatively soft, ductile, and malleable. The addition of carbon to iron malleable. The addition of carbon to iron makes the bonds more directional.makes the bonds more directional.

Mild SteelsMild Steels - contain less than 0.2 % carbon. - contain less than 0.2 % carbon. Still ductile and malleable - used for nails, Still ductile and malleable - used for nails, cables, and chains.cables, and chains.

SteelsSteelsMedium Steels Medium Steels - contain 0.2 - 0.6 % carbon. - contain 0.2 - 0.6 % carbon.

Harder than mild steels - used for rails and Harder than mild steels - used for rails and structural beams.structural beams.

High-carbon steels High-carbon steels - contain 0.6 - 1.5 % carbon. - contain 0.6 - 1.5 % carbon. Tough and hard - used for springs, tools, and Tough and hard - used for springs, tools, and cutlery.cutlery.

Alloy steelsAlloy steels - mixed interstitial & substitutional - mixed interstitial & substitutional alloys. Stainless steel has cobalt and nickel alloys. Stainless steel has cobalt and nickel substituted for iron - resistant to corrosion.substituted for iron - resistant to corrosion.

Identifying Types of SolidsIdentifying Types of Solids

a. ammoniaa. ammonia

b. ironb. iron

c. cesium fluoridec. cesium fluoride

d. argond. argon

e. sulfur (Se. sulfur (S88))

f. sulfur trioxidef. sulfur trioxide

g. barium oxideg. barium oxide

h. goldh. gold

a. moleculara. molecular

b. atomicb. atomic

c. ionicc. ionic

d. atomicd. atomic

e. moleculare. molecular

f. molecularf. molecular

g. ionicg. ionic

h. atomich. atomic

Name the type of solid formed by each of the following: