CHAPTER 12CHAPTER 12

CHEMISTRYCHEMISTRY

A comparison of Liquids & SolidsA comparison of Liquids & Solids

Molecular speed Molecular speed

Molecular distance Molecular distance

Molecular “order” Molecular “order”

Amount/Strength of Bonds Amount/Strength of Bonds

Liquids are faster

Liquids are closer than gases, farther than solids

Solids – most order; liquids - less order; gases – least order

Solids have the strongest external bonds

LIQUIDSLIQUIDS Indefinite shape Indefinite shape

Definite volume Definite volume

Not very compressible Not very compressible

Fluid Fluid

Ability to diffuse Ability to diffuse

Takes shape of container

Volume will change only slightly – with pressure or temp changes

Particles are more closely packed together

Particles can “flow” – can glide past one another

Constant random motion – slower than gases; Increase temp = Increase diffusion

LIQUIDSLIQUIDS

Surface TensionSurface Tension

A force that tends to pull adjacent parts of a liquid’s surface TOGETHER & DOWNWARD, thus making the surface less penetrable by solid bodies

LIQUIDSLIQUIDS How many pennies can you fit into a cup How many pennies can you fit into a cup

full of water? (Regular water only!)full of water? (Regular water only!) How many drops of water can you fit on How many drops of water can you fit on

the surface of a penny?the surface of a penny? Can you float a paper clip?Can you float a paper clip?

Use:

Regular water

Soap water

Salt water

LIQUIDSLIQUIDS

Ability to vaporizeAbility to vaporize

Ability to solidifyAbility to solidify

Vaporization; liq gas;

Two ways this can happen: BOILING, EVAPORATION

Becoming a solid; liq solids; Forces hold particles together in a solid

SOLIDSSOLIDS Can be:Can be:

CrystallineCrystalline

AmorphousAmorphous

Consists of crystals

Particles are arranged in an ORDERLY, GEOMETRIC, REPEATING pattern

Particles are arranged RANDOMLY

Ex – glass, plastic

http://www.cartage.org.lb/en/themes/sciences/Physics/SolidStatePhysics/AtomicBonding/BondingMechanisms/Difference/Difference.htm

SOLIDSSOLIDS Definite shape Definite shape

Definite volume Definite volume

NOT fluid NOT fluid

Not compressible Not compressible

Forces hold particles together

Particles packed very close together

Particles held in fixed positions

Very little empty space between particles

SOLIDSSOLIDS

Extremely SLOW diffusion Extremely SLOW diffusion

High density High density

Ability to melt Ability to melt

Strong attractive forces – don’t mix on own

Particles packed very close – high mass, low volume

KE overcomes intermolecular forces; sol liq

CRYSTALLINE SOLIDS

4 Types: Ionic Crystalline Solids Covalent Networks Metallics Covalent Moleculars

No surprises – you WILL have to list and explain these 4 on the test!!

CRYSTALLINE SOLIDSCRYSTALLINE SOLIDS

Ionic Crystalline SolidsIonic Crystalline Solids Transfer of electrons, +-+-+- (metal + nonmetal)Transfer of electrons, +-+-+- (metal + nonmetal) Crystal LatticeCrystal Lattice

• Total 3D array of points that describe the arrangement of Total 3D array of points that describe the arrangement of particles in a crystalparticles in a crystal

Unit CellUnit Cell• Smallest portion of a crystal lattice that reveals the 3D Smallest portion of a crystal lattice that reveals the 3D

patternpattern• There are a total of 7 different shapes (crystallography)There are a total of 7 different shapes (crystallography)• http://chemed.chem.wisc.edu/chempaths/GenChem-http://chemed.chem.wisc.edu/chempaths/GenChem-

Textbook/Lattices-and-Unit-Cells-837.htmlTextbook/Lattices-and-Unit-Cells-837.html• http://www.chem.ubc.ca/courseware/121/tutorials/exp7A/http://www.chem.ubc.ca/courseware/121/tutorials/exp7A/

2.html2.html

Crystalline SolidsCrystalline Solids ExamplesExamples

CubicCubic• 9090° angles° angles• L=w=hL=w=h

TetragonalTetragonal• 9090° angles° angles• Longer sides (rectangle) than top or bottom (square)Longer sides (rectangle) than top or bottom (square)

OrthorhombicOrthorhombic• 9090° angles° angles• ll≠w≠h≠w≠h• ALL rectangular sides!ALL rectangular sides!

Crystalline SolidsCrystalline Solids

Covalent NetworksCovalent Networks Single atoms covalently bonded to its nearest Single atoms covalently bonded to its nearest

neighboring atomneighboring atom Examples:Examples:

• Diamond (Diamond (True Covalent NetworkTrue Covalent Network))• Graphite (Graphite (Planar NetworkPlanar Network))

• CC6060 ( (BuckyballBuckyball))

No surprises – you WILL have to list and explain these 3 on the test!

True Covalent NetworksTrue Covalent Networks

HardHard Interlocking networksInterlocking networks High MP, non- or semiconductorsHigh MP, non- or semiconductors StrongStrong

http://cheminfo.chem.ou.edu/~mra/jmol/jmol.php

Planar NetworkPlanar Network ““Molecular Sheets”Molecular Sheets” Weak intermolecular forces Weak intermolecular forces

between sheetsbetween sheets Sheets glide past one another Sheets glide past one another

and allow a thin deposit of and allow a thin deposit of graphite as you writegraphite as you write

http://cheminfo.chem.ou.edu/~mra/jmol/jmol.php

BuckyballBuckyball

““Soccer ball”Soccer ball” 32 faces – 20 hexagons and 12 pentagons32 faces – 20 hexagons and 12 pentagons

MetallicsMetallics

Positive ions of metals Positive ions of metals surrounded by valence surrounded by valence electronselectrons

High electric High electric conductivity due to the conductivity due to the freedom of electrons to freedom of electrons to movemove

Covalent MolecularCovalent Molecular

Covalently bonded molecules held Covalently bonded molecules held together by intermolecular forcestogether by intermolecular forces

Low MP, easily vaporized, soft, good Low MP, easily vaporized, soft, good insulatorsinsulators

Example - iceExample - ice

SummarySummary

http://www.chm.davidson.edu/ChemistryApplets/Crystals/NetworkSolids.html

Amorphous SolidAmorphous Solid Noncrystalline solidsNoncrystalline solids NO regular, natural shapeNO regular, natural shape

Takes on shape imposed on themTakes on shape imposed on them Particles arranged randomlyParticles arranged randomly

Examples:Examples: Rubber, glass, plasticRubber, glass, plastic

Changes of StateChanges of State

EquilibriumEquilibrium Two opposing changes occur at equal ratesTwo opposing changes occur at equal rates

LeChatlier’s PrincipleLeChatlier’s Principle Add a stress (change in concentration, change in Add a stress (change in concentration, change in

pressure, change in temperature) to a system and the pressure, change in temperature) to a system and the system will work to relieve the stresssystem will work to relieve the stress

RULES – RULES – • Shift away from an added substance, towards removed Shift away from an added substance, towards removed

substance substance (Solids do not affect concentration!!)(Solids do not affect concentration!!)• Treat energy as a reactant/product for changes in tempTreat energy as a reactant/product for changes in temp• If decrease volume – shift towards side with fewer gas If decrease volume – shift towards side with fewer gas

moleculesmolecules

LeChatlier’s PrincipleLeChatlier’s Principle

LeChatlier’s PrincipleLeChatlier’s Principle Example:Example:

AsAs44OO66(s) + 6C(s) (s) + 6C(s) As As44(g) + 6CO(g)(g) + 6CO(g)• How would this shift if?How would this shift if?

Add COAdd CO Remove AsRemove As44OO66

Remove AsRemove As44

NN22(g) + 3H(g) + 3H22(g) (g) 2NH 2NH33(g)(g)• How would this shift if?How would this shift if?

Decrease volumeDecrease volume

CaCOCaCO33(s) + energy (s) + energy CaO(s) + CO CaO(s) + CO22(g)(g)• How would this shift if?How would this shift if?

Increase temperatureIncrease temperature Decrease temperatureDecrease temperature

BoilingBoiling Conversion of a liquid to a vaporConversion of a liquid to a vapor VAPOR PRESSUREVAPOR PRESSURE

Pressure of the vapor (gas) above the liquid surfacePressure of the vapor (gas) above the liquid surface Boiling occurs when VP = PBoiling occurs when VP = Patm atm (Barometer reading)(Barometer reading)

If PIf Patmatm low … low … (for ex - on top of a mountain) (for ex - on top of a mountain)

Boiling occurs easier…low BPBoiling occurs easier…low BP• Boiling Point of water on top of Mt. Everest = 69Boiling Point of water on top of Mt. Everest = 69°C°C

Food takes longer to cook (because it at cooking at a low Food takes longer to cook (because it at cooking at a low temp!)temp!)

If PIf Patmatm high… high… (for ex – below sea level)(for ex – below sea level)

Boiling is difficult…high BPBoiling is difficult…high BP• Boiling point of water at 1000ft below sea level = 101.1Boiling point of water at 1000ft below sea level = 101.1°C°C

Food cooks faster (because it is cooking at a high temp!)Food cooks faster (because it is cooking at a high temp!)

BoilingBoiling

Normal Boiling PointNormal Boiling Point Boiling point at Boiling point at standardstandard atmospheric atmospheric

pressure (1 atm, 760 mmHg, etc) – Sea Levelpressure (1 atm, 760 mmHg, etc) – Sea Level

Melting/FreezingMelting/Freezing

Normal MP/FP of water = 0Normal MP/FP of water = 0°C (NOT °C (NOT affected by pressure changes!!)affected by pressure changes!!)

SublimationSublimation Solid Solid gas gas Some substance do this at room temperatureSome substance do this at room temperature

• Example – dry ice (solid COExample – dry ice (solid CO22))

Heating/Cooling CurvesHeating/Cooling CurvesHeating Curve:Heating Curve:

Heating/Cooling CurveCooling curve would be reversed:Cooling curve would be reversed:

Phase DiagramPhase Diagram Water: LectureWater: Lecture

Phase DiagramPhase Diagram Carbon DioxideCarbon Dioxide

Phase DiagramPhase Diagram

Triple PointTriple Point All three states of matter exist simultaneouslyAll three states of matter exist simultaneously

Critical PointCritical Point Last temp and pressure at which a liquid can Last temp and pressure at which a liquid can

existexist Difference between phase diagram of Difference between phase diagram of

water and carbon dioxide?water and carbon dioxide?

WaterWater Liquid waterLiquid water

• Has “clumps” of 4-8 molecules per groupHas “clumps” of 4-8 molecules per group

Solid waterSolid water• Forms hexagonal lattice (6 sides) with empty Forms hexagonal lattice (6 sides) with empty

spacesspaces• Gives solid ice low density (large volume, small Gives solid ice low density (large volume, small

mass)mass)• Solid floats on liquid!!Solid floats on liquid!!