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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!!