IMF’s, Solids, and Liquids
Ch. 11 in Textbook
msconti.blogspot.com
I. Intermolecular Forces (IMF’s)
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attractions between separate
molecules, not bonds
relatively weak
occur based on molecular
polarity and/or charge
the strength determines
substance’s phase, b.p., m.p.,
vapor pressure, etc.
itl.chem.ufl.edu
HW: 11.4, 11.6
science.uwaterloo.ca
1. Ion-Dipole Forces (AKA
Molecule-Ion Attractions)
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between an ion (full
charge) and the δ+ or δof a polar molecule
usually the polar
molecule is water acting
as a solvent
the greater the
magnitude of the ionic
charge and/or the partial
charges, the stronger the
IMF’s
chem.purdue.edu
chemprofessor.com
2. van der Waals Forces
A) Dipole-Dipole Forces
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a dipole (2 poles) is a polar
molecule
attractions between polar
molecules
relatively strong, but
technically weaker than iondipole forces
the higher the value of μ
(dipole moment), the higher the
IMF’s (for similar mass/size
molecules)
chemtext.blogspot.com
chem.unsw.edu.au
B) Hydrogen Bonding
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NOT a bond
when H is bonded to very EN
elements (N,O,F, ONLY) a
“super dipole” is formed
usually NH3, H2O, and HF
this leads to unusually high
dipole-dipole attractions and
thus, unusually high b.p.’s
also results in ice being less
dense than water
weren’t you listening, I said it’s
“NOT a bond!”
chemed.chem.wisc.edu
yellowtang.org
C) London Dispersion Forces (AKA
Weak Forces)
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occurs between
nonpolar molecules
helps when molecules
are close to one another
results from
momentary/temporary/
induced dipoles
itl.chem.ufl.edu
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the more you can distort an
atom or molecule’s
electron cloud distribution,
the more polarizable it is
larger/massive
atoms/molecules are more
polarizable
thus, larger
atoms/molecules have
stronger IMF’s
ex) halogens
elmhurst.edu
C
cactus.dixie.edu
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NOTE: all molecules have
London dispersion forces!
when molecules are of
similar size, polarity
determines the strength of
IMF’s
when molecules differ greatly
in size, then polarizability
determines the strength of
IMF’s
phys.bspu.unibel.by
HW: 11.8, 11.10, 11.12 (a)-(c), 11.18,
11.22
IMF flow chart
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do activity in lab area
as a group of 4
have chart “Schu
approved”
copy as notes
adroll.com
II.
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Properties of Liquids
1. Viscosity
resistance to flow
high viscosity- molasses, syrup
low viscosity- ethanol, water
based not only on the strength
of the IMF’s, but also structural
features that may cause
entanglement of molecules
as temp. inc., viscosity dec. due
to the breaking of IMF’s
syntheticperformanceoil.com
2. Surface Tension
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due to the imbalance of
IMF’s within a liquid
there is a net downward
pull of surface
molecules
results in close packing
of molecules at the
surface, forming a
“skin”
fizyka.phys.put.poznan.pl
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technically, surface
tension is defined as the
energy required to
increase the surface area
of a liquid by a unit
amount
units: J/m2
quest.nasa.gov
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water has a high surface
tension due to high
IMF’s
mercury has an even
higher surface tension
due to metallic bonding
ramehart.com
HW: 11.23
3. Cohesion and Adhesion
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cohesion = IMF’s between
molecules of the same
substance
adhesion = IMF’s between
molecules and other
surface
although both types of
forces are present, mercury
has greater cohesive forces
than water whereas water
has greater adhesive forces
than mercury
cr4.globalspec.com
4. Capillary Action
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molecules of liquid rising up
a narrow tube
mechanism = adhesion
causes water to stick to tube
which increases the surface
area; in order to reduce
surface area, surface tension
pushes water up tube against
gravity
ex) chromatography; water
in plant roots
cc.gatech.edu
HW: 11.24
III. Phase Changes
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chemistry.wustl.edu
HW: 11.28
1. Heating/Cooling Curves
physicalweeding.com
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heat is ALWAYS being added!
when temperature increases, the
KE (energy of motion) of the
particles must be increasing (PE
remains the same)
when temperature remains the
same, the KE of the particles
must remain the same; thus, PE
(energy of position) increases as
the phase change occurs
funsci.com
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ΔHvap > ΔHfus
q = mCΔT used for
calculating heat during
temp. changes
where
q = heat change in J
m = mass in g
C = specific heat in
J/g·K or J/g·ºC
ΔT = temp change
(Tf – Ti) in K or ºC
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mrbigler.com
HW: 11.34
2. Vapor and Vapor Pressure
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vapor = gaseous form of a
substance normally found as
a liquid
vapor pressure = pressure due
to vapor
evaporation = vaporization of
surface molecules of liquid
boiling = vaporization
throughout liquid, occurs
when the vapor pressure =
atmospheric pressure
kidsgeo.com
STORYTIME!
cityoflawton.ok.us
#1 Water in a Beaker
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@ room temp and
standard pressure
what happens to it?
goldcoast.qld.gov.au
#2 Stoppered Flask of Water
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@ room temp and
standard pressure
what happens to it?
daigger.com
#3 Ethanol Vs. Water
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@ room temp and standard pressure
what happens?
volatility = the ability to evaporate easily
outboardmotoroilblog.com
images.veer.com
#4 Heated flask of Water
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constant heating @
standard pressure
what happens to it?
normal boiling point =
temperature at which
the v.p. of water equals
1 atm (standard
pressure)
demo.physics.uiuc.edu
HW: 11.39, 11.42
3. Vapor Pressure Curves
kentchemistry.com
HW: 11.43
4. Phase Diagrams
from textbook
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triple point = temp. and
pressure at which all 3
phases exist in
equilibrium
critical point = the
highest temp. and
pressure at which a
liquid can exist
supercritical fluid =
liquid and gas phases
are indistinguishable
definitiontees.com
HW: 11.36, 11.47, 11.48, 11.50,
IV. Structures of Solids
1. Crystalline vs. Amorphous
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crystalline = well-defined
arrangement of atoms or
molecules (def. attractions =
def. m.p.)
ex) quartz, diamond, ionic
solids
amorphous = no well-defined
arrangement of atoms or
molecules (indef. attractions =
softens over temp. range, no
distinct m.p.)
ex) glass, rubber
ndt-ed.org
HW: 11.53
2. Unit Cells
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unit cell = the “bricks”
that make up a
crystalline solid; the
smallest repeating unit
in a crystal lattice
fkp.jku.at
A) Primitive Cubic
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the lattice points are at
the corners and are
actually shared by 8
atoms!
1/8 of an atom x 8
corners = 1 atom
ece-www.colorado.edu
mrsec.wisc.edu
B) Body-Centered Cubic
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lattice points are at the
corners and at the center
1/8 of an atom x 8
corners + 1 atom =
2 atoms
ece-www.colorado.edu
mrsec.wisc.edu
C) Face-Centered Cubic
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lattice points are at the
corners and each
face/side
½ of an atom x 6 sides +
1/8 atom x 8 corners =
4 atoms
mrsec.wisc.edu
ece-www.colorado.edu
HW: 11.56, 11.58
3. Bonding in Solids
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molecular solids
ionic solids
metallic solids
covalent-network solids =
continuous lattice
structure of covalent
bonds (no molecules);
rigid and dense with high
m.p.’s (FYI, must break
bonds to melt!)
ex) SiO2, C (diamond), C
(graphite), C (buckyballs)
chem.ufl.edu
HW: 11.69, 11.70
legacy.co.mohave.az.us