Intermolecular Attractions & the Properties of Liquids & Solids
CHAPTER 12 Chemistry: The Molecular Nature of Matter, 6th edition
By Jesperson, Brady, & Hyslop
REVIEW
2Jesperson, Brady, Hyslop. Chemistry: The Molecular Nature of Matter, 6E
Strength of Intermolecular Forces
CHAPTER 12 Concept Review
London Dispersion Forces
Dipole-Dipole Forces
Hydrogen Bonds (a type of Dipole-Dipole Force)
Ion-Dipole or Ion-Induced Dipole Forces
Weakest
Strongest
3Jesperson, Brady, Hyslop. Chemistry: The Molecular Nature of Matter, 6E
Strength of Intermolecular Forces
CHAPTER 12 Concept Review
London Dispersion Forces: minimized surface area
London Dispersion Forces: maximized surface area
Dipole-Dipole Forces: small overall dipole moment
Dipole-Dipole Forces: large overall dipole moment
Hydrogen Bonds: with 1 H-bond per molecule
Hydrogen Bonds: with multiple H-bonds per molecule
Ion-Dipole or Ion-Induced Dipole Forces
Weakest
Strongest
4Jesperson, Brady, Hyslop. Chemistry: The Molecular Nature of Matter, 6E
Strength of Intermolecular Forces
CHAPTER 12 Concept Review
Property of s, l, g Increases Decreases Example
Boiling Point
Melting Point
Compressibility
Diffusion
Retention of V & Shape
Surface Tension
Wetting
Viscosity
Property of s, l, g Increases Decreases Example
Boiling Point increasing total intermolecular forces
decreasing total intermolecular forces
Water has a high boiling point because it has H-bonding, dipole, and dispersion forces. It is close to heptane (C7H16), a heavier molecule that only experiences dispersion forces .
Melting Point increasing total intermolecular forces
decreasing total intermolecular forces
The melting point of ionic solids is extremely high compared to water which experiences all other intermolecular forces, but not ion-dipole forces. (NaCl is 1074 K and water is 273 K)
Compressibilityincreasing distance between collisions with other particles
decreasing distance between collisions with other particles
Gases are very compressible because the particles have higher kinetic energies, and great distances between particles.
Diffusionwith increasing kinetic energy & increased distance between collisions
with deceasing kinetic energy & decreased distance between collisions
Diffusion is much slower in a solid or in a liquid and much faster in a gas.
Retention of V & Shape
Increasing intermolecular forces and decreasing T & P
Decreasing intermolecular forces, and increasing kinetic energy of particles or T & P
Gases will fill the volume and shape of the container that holds them, while solids will retain their own shape and volume regardless of the container.
Surface Tension with increasing intermolecular forces
with decreasing intermolecular forces
The molecules on the surface have less neighbors (and therefore less stabilizing intermolecular forces) and so have a higher potential energy, which the material will try to reduce with its shape (sphere): water beading.
Wettingwhen there are fewer intermolecular attractions to overcome in order to interact with the surface
When the intermolecular forces in the liquid are stronger then the intermolecular forces with the surface
Water beads on a greasy surface rather then wetting because the dipole forces and hydrogen bonds are so much stronger then the dispersion forces that water experiences with the surface. If the surface is clean it can experience dipole forces and hydrogen bonds with the oxygen in SiO2.
Viscosityincreasing intermolecular forces and decreasing temperature
decreasing intermolecular forces and decreasing temperature
Not just a property of liquids, also gases and solids. Amorphous solids change shape over time because of their viscosity.
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Phase Changes = changes of physical state with temperature ( α to KE)
SOLID LIQUIDGAS
fusion
freezing
evaporation
condensation
deposition
sublimation
endothermic
exothermic
System absorbs energy from surrounds in the form of heato Requires the addition of heat
System releases energy into surrounds in the form of heat or lighto Requires heat to be decreased
TEM
PERA
TURE
HEAT ADDED
HEATING CURVE
solid
liquid
gas
s <--> l
l <--> g
fusionΔHfus
evaporationor vaporization
ΔHvap
endothermic
endothermic
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Equilibrium & Phase Diagrams
T1 = 78°CP1 = 330 atm
To increaseT2 = 100°CThe system must respond by increasing P2 = 760 to restore equilibrium:o T is highero Volume of liquid is
lower o P of vapor higher
Le Chatelier’s PrincipleLiquid + Heat Vapor
If you increase either the liquid or the heat the reaction is
driven to the right to re-establish equilibrium.
If you increase vapor the reaction will be driven to the
left to re-establish equilibrium.
Liquid + Heat Vapor
Liquid + Heat Vapor
Liquid + Heat VaporLiquid + Heat Vapor
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3-D Simple Cubic Lattice
Portion of lattice—open view
Unit Cell
Space filling model
Other Cubic Lattices
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Face Centered Cubic
Body Centered Cubic
Site Counts as Shared by X unit cells
Body 1 1
Face 1/2 2
Edge 1/4 4
Corner 1/8 8
Counting Atoms in Unit Cells
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Interpreting Diffraction DataBragg Equation• nλ=2d sinθ
– n = integer (1, 2, …)– = wavelength of
X rays– d = interplane spacing
in crystal– = angle of incidence
and angle of reflectance of X rays to various crystal planes
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Example: Using Diffraction DataX-ray diffraction measurements reveal that copper crystallizes with a face-centered cubic lattice in which the unit cell length is 362 pm. What is the radius of a copper atom expressed in picometers?
This is basically a geometry problem.
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Ex. Using Diffraction Data (cont.)
diagonal = 4 rCu = 512 pm
rCu = 128 pm
Pythagorean theorem: a2 + b2 = c2
Where a = b = 362 pm sides and c = diagonal
2a2 = c2 and aac 22 2
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