Chapter 131 Intermolecular Forces: Liquids, and Solids Chapter 13.
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Transcript of Chapter 131 Intermolecular Forces: Liquids, and Solids Chapter 13.
Chapter 13 1
Intermolecular Forces: Intermolecular Forces: Liquids, and SolidsLiquids, and Solids
Chapter 13Chapter 13
Chapter 13 2
A Molecular Comparison of Liquids A Molecular Comparison of Liquids and Solidsand Solids
Chapter 13 3
Intermolecular ForcesIntermolecular Forces
Chapter 13 4
Intermolecular ForcesIntermolecular Forces
Ion-Dipole ForcesIon-Dipole Forces- Interaction between an ion (Na+) and a dipole (water).- Strongest of all intermolecular forces
Chapter 13 5
Intermolecular ForcesIntermolecular Forces
Chapter 13 6
Intermolecular ForcesIntermolecular Forces
Dipole-Dipole ForcesDipole-Dipole Forces- Interaction between an dipole on one molecule and a
dipole on an adjacent molecule.- Dipole-dipole forces exist between neutral polar
molecules.- Weaker than ion-dipole forces
Chapter 13 7
Intermolecular ForcesIntermolecular Forces
Chapter 13 8
Intermolecular ForcesIntermolecular Forces
London Dispersion ForcesLondon Dispersion ForcesInduced Dipole – Induced DipoleInduced Dipole – Induced Dipole
- Weakest of all intermolecular forces.- It is possible for two adjacent nonpolar molecules to
affect each other.- The nucleus of one molecule (or atom) attracts the
electrons of the adjacent molecule (or atom).- This attraction causes the electron clouds become
distorted.- In that instant a polar molecule (dipole) is formed
(called an instantaneous dipole).
Chapter 13 9
Intermolecular ForcesIntermolecular Forces
London Dispersion ForcesLondon Dispersion Forces
Chapter 13 10
Intermolecular ForcesIntermolecular ForcesHydrogen BondingHydrogen Bonding- A special case of dipole-dipole forces.- This intermolecular force is very strong. - Strongest of the three Van der Waal’s forces
(Hydrogen bonding, Dipole-dipole, London forces,)- H-bonding requires H bonded to an electronegative
element (most important for compounds of F, O, and N).
Chapter 13 11
Intermolecular ForcesIntermolecular ForcesHydrogen BondingHydrogen Bonding
Chapter 13 12
Some Properties of LiquidsSome Properties of Liquids
ViscosityViscosity- Viscosity is the resistance of a liquid to flow.- A liquid flows by sliding molecules over each other.- The stronger the intermolecular forces, the higher the
viscosity.
Chapter 13 13
Some Properties of LiquidsSome Properties of Liquids
Surface TensionSurface Tension- The surface of a liquid behaves as a membrane or
barrier.- This is due to the unequal attractive forces on
molecules as the surface.- Surface molecules are only attracted inwards towards
the bulk molecules.
Chapter 13 14
Some Properties of LiquidsSome Properties of Liquids
Surface TensionSurface Tension- Cohesive forces bind molecules to each other.- Adhesive forces bind molecules to a surface.
Chapter 13 15
Some Properties of LiquidsSome Properties of Liquids
Surface TensionSurface Tension- Meniscus is the shape of the liquid surface. – If adhesive forces are greater than cohesive forces, the
liquid surface is attracted to its container more than the bulk molecules. Therefore, the meniscus is U-shaped (e.g. water in glass).
– If cohesive forces are greater than adhesive forces, the meniscus is curved downwards.
Chapter 13 16
Some Properties of LiquidsSome Properties of Liquids
Surface TensionSurface TensionCapillary Action - When a narrow glass tube is placed in
water, the meniscus pulls the water up the tube.
Chapter 13 17
Properties of LiquidsProperties of LiquidsVaporizationVaporization• Also called evaporation– A process in which a substance is transfromed from a liquid
to a gas.
• Standard molar enthalpy of vaporization (Hovap)
– The energy required to convert one mole of a liquid at its boiling point to a gas.
• The resulting gas will exert a pressure on a system.
Chapter 13 18
Properties of LiquidsProperties of LiquidsVapor PressureVapor Pressure• This is the pressure exerted by a substance in the gas
phase.• As a liquid’s temperature increases, its vapor
pressure increases.
Chapter 13 19
Properties of LiquidsProperties of LiquidsVapor PressureVapor PressureVolatile – A substance which has a low boiling point
Or
A substance which has a high vapor pressure at a low temperature
Chapter 13 20
Properties of LiquidsProperties of LiquidsVapor Pressure and Boiling PointVapor Pressure and Boiling Point- Liquids boil when the external pressure equals the
vapor pressure.- Two ways to get a liquid to boil: increase temperature
or decrease pressure.- Normal boiling point is the boiling point at 760 mmHg
(1 atm).
Chapter 13 21
Properties of LiquidsProperties of LiquidsVapor Pressure and Boiling PointVapor Pressure and Boiling Point- Vapor pressure, temperature and enthalpy of
vaporization can be related to each other using:Clausius-Clapeyron equation:
211
2 11ln
TTR
H
P
Povap
P = pressureT = temperatureR = gas lawHo
vap = enthalpy of vaporization
Chapter 13 22
Properties of LiquidsProperties of LiquidsVapor Pressure and Boiling PointVapor Pressure and Boiling Point
The Clausius-Clapeyron equation makes more sense when it is rearranged into the slope intercept form.
CRT
HP
ovap
ln
Chapter 13 23
Properties of LiquidsProperties of LiquidsVapor Pressure and Boiling PointVapor Pressure and Boiling Point
Chapter 13 24
Structures of SolidsStructures of SolidsUnit CellsUnit Cells- Crystalline solid: well-ordered, definite arrangements
of molecules, atoms or ions. - Crystals have an ordered, repeated structure.- The smallest repeating unit in a crystal is a unit cell.- Three-dimensional stacking of unit cells is the crystal
lattice.
Chapter 13 25
Structures of SolidsStructures of SolidsUnit CellsUnit Cells
Chapter 13 26
Structures of SolidsStructures of SolidsUnit CellsUnit Cells
Chapter 13 27
Structures of SolidsStructures of SolidsCell OccupancyCell Occupancy
Chapter 13 28
Structures of SolidsStructures of SolidsCell OccupancyCell Occupancy
Chapter 13 29
Structures of SolidsStructures of SolidsCell OccupancyCell Occupancy
Site Occupancy
Corner 1/8
Edge 1/4
Face 1/2
Center 1
Chapter 13 30
Structures of SolidsStructures of SolidsCell OccupancyCell Occupancy
Zinc (grey) 4 Center 4 atoms
Sulfur (yellow) 8 corners
6 faces
1 atom
3 atoms
Zn4S4 ZnS
Chapter 13 31
Structures of SolidsStructures of SolidsClose Packing of SpheresClose Packing of Spheres- A crystal is built up by placing close packed layers of
spheres on top of each other.- There is only one place for the second layer of
spheres.- There are two choices for the third layer of spheres:- Third layer eclipses the first (ABAB arrangement). This is
called hexagonal close packing (hcp).
- Third layer is in a different position relative to the first (ABCABC arrangement). This is called cubic close packing (ccp).
Chapter 13 32
Structures of SolidsStructures of SolidsClose Packing of SpheresClose Packing of Spheres
Chapter 13 33
Structures of SolidsStructures of SolidsClose Packing of SpheresClose Packing of Spheres- Each sphere is surrounded by 12 other spheres (6 in
one plane, 3 above and 3 below).- Coordination number: the number of spheres directly
surrounding a central sphere.
Chapter 13 34
Structures of SolidsStructures of SolidsOther Kinds of Solid MaterialsOther Kinds of Solid Materials
Molecular SolidsThese are crystalline substances in which the “building blocks” are composed of molecules in place of ions.
Example: Table Sugar
Chapter 13 35
Structures of SolidsStructures of SolidsOther Kinds of Solid MaterialsOther Kinds of Solid Materials
Network SolidsThese are crystalline substances in which the “building blocks” are atoms and all the atoms are connected by covalent bonds.
Example: Diamond
Chapter 13 36
Phase DiagramsPhase Diagrams- Phase diagram: plot of pressure vs. temperature
summarizing all equilibria between phases.
Chapter 13 37
Phase DiagramsPhase Diagrams
Chapter 13 38
Phase DiagramsPhase DiagramsTriple point - Temperature and pressure at which all
three phases are in equilibrium.
Critical point – Point above which the liquid and gas phases are indistinguishable.
Critical temperature - The minimum temperature for liquefaction of a gas using pressure
Critical pressure - Pressure required for liquefaction
Chapter 13 39
2, 16, 18, 24, 30, 32, 40, 44
HomeworkHomework