Chemistry, The Central Science, 10th edition
Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten
Unit 5 (Chp 11,13)
Bonds & IMAFs in
Liquids, Solids, and
Solutions
John D. Bookstaver
St. Charles Community College
St. Peters, MO
 2006, Prentice Hall, Inc.
“Bonds”
Attractions
“IMAFs”
Intra–
Inter–
(strong)
(weak)
Ionic
Covalent
(metal–
nonmetal)
(nonmetals)
polar
nonpolar
?
?
?
Intermolecular Attractive Forces
Intramolecular Attraction (within)
(strong bonds)
(weak)
Intermolecular Attraction (between)
Which attraction is overcome (broken) by
melting & vaporizing? weak IMAFs
between molecules
Intermolecular Attractive Forces
Intramolecular Attraction (within)
(strong bonds)
(weak)
Intermolecular Attraction (between)
IMAFs determine physical properties
such as boiling & melting points,
bp, mp,
vapor pressure, and viscosity.
vp, visc.
States of Matter
The main difference between phases of
matter is the distance between particles.
changes of state
States of Matter
State (distance between particles) at a certain
T and P depends on two opposing qualities:
IMAFs
KE
vs. (intermolecular
(kinetic energy
attractive forces
of the particles
between particles)
“Bonds”
Attractions
“IMAFs”
Intra–
Inter–
(strong)
(weak)
Ionic
Covalent
(metal–
nonmetal)
(nonmetals)
polar
nonpolar
?
London Dispersion Forces
Electrons in the 1s orbital of He
repel each other, BUT…
they occasionally wind up on
the same side of the atom.
d
+
d
At that instant, the He atom is
polar (instantaneous dipole).
(excess of e–’s on one side, and
shortage on the other)
London Dispersion Forces
causes
induced
dipole
d
LDFs:
+
d
instantaneous
dipole
d
+
d
attractions between instantaneous dipoles
and induced dipoles caused by motion of e–’s.
London Dispersion Forces
• present in all molecules,
(polar & nonpolar)
d
+
d
d
• The tendency of
an electron cloud
to distort to
become
temporarily polar
in this way is
called
+
d ___________.
polarizability
Factors Affecting London Forces
MW (molecular weight)
• LDFs increase with increased MW b/c…
larger e– clouds, are more polarizable.
(use this phrase to
answer FR question)
Factors Affecting London Forces
Shape
• long, skinny
molecules have
stronger IMAFs
due to…
…increased
surface area to
form more
attractions.
(SAcylinder > SAsphere)
“Bonds”
Attractions
“IMAFs”
Intra–
Inter–
(strong)
(weak)
Ionic
Covalent
(metal–
nonmetal)
(nonmetals)
polar
nonpolar
London
dispersion
forces
(nonpolar & all)
?
Dipole-Dipole Interactions
(dipole)
(dipole)
• Polar molecules with
permanent dipoles are
attracted to each other.
Dipole-Dipole Interactions
DEN
?
polar
bonds
assym.
shape
The more polar the molecule,
the higher the boiling/melting point.
(due to greater dipole-dipole IMAFs that
require more energy to overcome)
Which Have a Greater Effect:
Dipole-Dipole Interactions or Dispersion Forces?
•dipole–dipole interactions (permanent dipoles)
are typically stronger than LDFs
(temporary dipoles as instantaneous–induced).
•But much larger molecules could have
LDFs that are stronger than dipole-dipole
interactions.
(larger e– clouds, are more polarizable)
“Bonds”
Attractions
“IMAFs”
Intra–
Inter–
(strong)
(weak)
Ionic
Covalent
(metal–
nonmetal)
(nonmetals)
polar
nonpolar
London
dispersion
forces
(all, nonpolar)
dipole–
dipole
(polar)
?
How Do We
Explain This?
Boiling Points
•unusually high bp
•unusually strong IMAFs
polar
nonpolar
Hydrogen Bonding
• H-bonds are caused by an
electron deficient H atoms
(bonded to N, O, or F) attracted to
small, very electronegative
N, O, or F atoms on a
nearby molecule.
“Bonds”
Attractions
“IMAFs”
Intra–
Inter–
(strong)
(weak)
Ionic
Covalent
(metal–
nonmetal)
(nonmetals)
polar
nonpolar
London
dispersion
forces
(all, nonpolar)
?
dipole–
dipole
(polar)
H–bonds
H with
N, O, F
Ion-Dipole Interactions
• ionic solutes dissolve in polar solvents
H
Na+
O
Cl–
H
H
O
H
“Bonds”
Attractions
“IMAFs”
Intra–
Inter–
(strong)
(weak)
Ionic
Covalent
(metal–
nonmetal)
(nonmetals)
polar
nonpolar
London
dispersion
forces
(all, nonpolar)
ion–
dipole
(aq ions)
dipole–
dipole
(polar)
H–bonds
H with
N, O, F
Intermolecular Attractive Forces
Stronger
H-bonds
(if H with N, O, or F)
dipole-dipole int.’s
(polar molecules)
London dispersion forces
(nonpolar, instant–induced dipoles)
Weaker
Organic Functional Groups
Alkanes
• London dispersion forces (LDFs) only
• bp increases as length of chain b/c…
…larger e– cloud, more polarizable
Organic Functional Groups
What IMAFs?
polar &
H-bond
polar
Organic Functional Groups
What IMAFs?
polar &
H-bond
polar
polar
polar &
H-bond
butane
LDFs
ethylamine H-bond
(alkane)
(amine)
dipole-dipole
3–pentanone
(ketone)
dipole-dipole
H-bond
trimethylamine
(amine)
ethanol
H-bond
(alcohol)
ethanoic acid (carboxylic acid)
dipole-dipole
propanal (aldehyde)
IMAFs in Protein Structure & DNA
acid
amino
IMAFs in Protein Structure & DNA
4
1
2
3
IMAFs in Protein Structure & DNA
HW
p. 476
Intermolecular Forces Affect
Many Physical Properties
The strength of the
attractions between
particles can greatly
affect the physical
properties of a
substance or solution.
Cohesive/Adhesive Forces
Adhesive
• to surface
Cohesive
• to each other
glass
adhesive
cohesive
Capillary Action
• due to co/adhesive forces
Surface Tension
results from the
net inward force
experienced by the
molecules on the
surface of a liquid.
Viscosity
• resistance of a liquid to flow
• increases with IMAF’s and
decreases with higher temp.
HW p. 479 #29
Phase Changes
HW p. 479
#34
Energy and Phase Changes
• Heat of Fusion (Hfus):
energy to change (s) to (l) at melting point.
Energy and Phase Changes
DEMO:
butane
• Heat of Vaporization (Hvap):
energy to change (l) to (g) at boiling point.
Energy and Phase Changes
HW
p. 480
#35
47a
Temp. does
not change
Added
during
energy
What happens phase
to added KE? change. separates
particles
(overcome
IMAFs)
Vapor Pressure
pressure above liquid
more volatile
=
more vapor
=
_____
weak IMAFS
liquid molecules
escape to vapor
gas molecules
condense to liquid
(dynamic equilibrium)
Vapor Pressure
• As T ↑, the fraction of molecules that have
enough energy to escape increases.
Vapor Pressure
As more molecules escape the liquid, the
pressure they exert increases.
Dynamic Equilibrium:
vaporize/condense at same rate
Vapor Pressure
•normal b.p.:
T at which
v.p. = 1 atm
•boiling point:
T at which
vapor pressure
=
atmospheric
pressure
HW p. 480 #47b, 48
DEMO:
boil H2O
Solutions
+
• homogeneous mixtures of
pure substances.
• solute is dispersed uniformly
throughout the solvent.
Why does stuff dissolve?
IMAFs between
IMAFs between solute–solvent
solvated
solute–solute
must be
solvent–solvent
(dissolved)
stronger
For Ionic Solutes…
Ions are soluble in water because ion-dipole
attractions are strong enough to overcome the
crystal lattice energy of the ionic solid salt.
Energy Changes in Solution
separation of solute separation of solvent
(absorb = endothermic) (absorb = endothermic)
attractions between solute and solvent
(release = exothermic)
+
Demo
H
+
– enthalpy
+
–
+
(heat)
–
∆H
(final – initial)
+
Why Do
Endothermic
Processes Occur?
Usually favorable
processes tend to
lower energy.
∆E = – (exo or release)
But in some processes,
heat is absorbed,
not released. How?
+
–
+
+
Entropy
Entropy (S): dispersal of matter & energy
(disorder or randomness)
• increasing the entropy (dispersal) by mixing
lowers the energy of a system (even if ∆H = +).
∆S = (final – initial)
(less disorder)
∆S = (more – less) (more disorder)
∆S = +
∆H + (heat absorbed)
∆S + (gains disorder)
+ (lowered)
(raised)
∆E –
Types of Solutions
• Saturated
Solvent holds
maximum solute
possible at that
temperature.
Dissolved solute is in
dynamic equilibrium
with solid solute
particles.
Types of Solutions
• Unsaturated
Less than the
maximum
dissolved at that
temperature.
Types of Solutions
• Supersaturated
More solute than is normally possible
at that temperature.
unstable; crystallization is stimulated
by a “seed crystal” or scratching.
Factors Affecting Solubility
• “like dissolves like”: (similar IMAFs)
Polar substances dissolve in polar solvents.
H2O
CH3Cl
CH3CH2OH
NH3
Nonpolar dissolve in nonpolar solvents.
C6H14
CCl4
I2
similar IMAFs are more soluble.
HW p. 566 #12,14,18
Which is more soluble in water (H2O) and
which is more soluble in hexane (C6H14)
Gases in Solution
• In general, the solubility of gases in water
increases with increasing size. …WHY?
• Larger molecules have larger e– clouds
stronger dispersion forces.
Gases in Solution
• The solubility of gas in liquid is
directly proportional to pressure.
Gases are
more soluble:
Low T
High P
solubility of solids inc. with temp. 1) Highest
at
Solubility solubility
20oC? 30oC?
Curves
HW p. 566
#20,23,25
2) How
many grams
KClO3 at
70oC ?
3) Is 50 g of
KCl at 50oC
sat, unsat,
or supersat?
30 g of
NaCl at
30oC?
Intermolecular Forces Affect
Many Physical Properties
The greater the IMAFs,…
greater the bp and mp.
the _______
greater the cohesion/adhesion.
the _______
greater the surface tension.
the _______
greater the viscosity.
the _______
the _______
lower the vapor pressure (volatility)
Intermolecular Forces Affect
Many Physical Properties
Which has a higher boiling point? Explain.
CF4 vs. CH3OCH3
CF4 has London dispersion forces and
CH3OCH3 has dipole-dipole interactions.
Stronger intermolecular attractive forces in
CH3OCH3 require more energy to overcome.
mp’s (of solids)
Attractions
“Bonds”
mp’s & bp’s
“IMAFs”
Intra–
Inter–
(strong)
(weak)
Ionic
Covalent
(metal–
nonmetal)
(nonmetals)
polar
nonpolar
London
dispersion
forces
(all, nonpolar)
ion–
dipole
(aq ions)
dipole–
dipole
(polar)
H–bonds
H with
N, O, F
4 Types of Solids
Ionic [metal–nonmetal]
• ions (transferred e–’s)
Covalent [nonmetals]
• sharing of e–’s
Diamond
Covalent Network [C(d)]
• shares e–’s throughout
Quartz
Metallic [metals]
• metal atoms bonded
by a sea of e–’s
Ionic Solids
more q
less d
stronger
attraction
more
energy
to break
(ordered)
• Strong Ionic Bonds in a crystal lattice of
+/– ions bonded by electrostatic attraction.
(Coulombic)
hard and brittle
q 1q 2
E=
high melting points
d
conduct in solution(aq) or molten(l)
Covalent (Molecular) Solids
C(graphite)
• Weak IMAF’s (LDF’s, dipole-dipole, H-bonds)
softer
lower melting points
Covalent-Network Solids
C(graphite)
C(diamond)
• Strong Covalent Bonds throughout.
C(diamond)
WC2 (carbide)
SiO2 (quartz)
Very hard
Very high melting points
Metallic Solids
• Metals are not
covalently bonded,
but attractions are
too strong to be
IMAFs.
• Metallic Bonds
delocalized valence “sea” of electrons.
Excellent conductors
Malleable and Ductile (“smooshable”)
soft to very hard
low to very high m.p.’s
Alloys
Brass
Steel
67%Cu, 33%Zn
80%Fe, 0.4%C,
18%Cr, 1%Ni
Alloys:
Homogeneous metallic mixtures (solutions)
by mixing melted metals in the liquid phase.
Attractions:
Held together mainly by metallic bonding
due to a delocalized sea of electrons.
Alloys
Brass
Steel
C
Fe
Fe
Fe
Fe
Substitutional:
• at. radius = similar
• density = in between
• malleability = similar
Fe
Fe
Fe
Fe
Fe
Fe
Fe
Interstitial:
• at. radius = different
(smaller fits between larger)
• density = greater
(more mass in same volume)
• malleability = less
Attractions in Solids, Liquids, & Solutions
Type
Forces Between Particles
Properties
Intermolecular
Attractions
(IMAFs)
Molecular
London dispersion forces (nonpolar)
Ar
I2
C2H5OH
Soft
CO2 H2O Dipole-dipole interactions (polar) - + Low mp & bp
d
d
C11H22O11 Hydrogen bonds (H with N, O, F)
Poor conductor
C(diamond) CovalentSiO2
Network
WC2
NaCl
CuSO4
Ionic
Covalent Bonds (network)
C(diamond) , SiO2 (quartz) ,
WC2 (tungsten carbide) , etc…
Ionic Bonds
crystal lattice of
charged ions
Metallic Bonds
All metals Metallic
& alloys: Cu, Fe, K, Al,… “sea” of electrons
(l) + (l), Solutions
(s) + (l) = (aq)
+
qq
Very hard
Very high mp
Poor conductor
Hard and brittle
High mp
1 2
Conducts as (aq) or (l)
d
Soft to very hard
Low to very high mp
Great Conductor, Malleable, Ductile
Solute-Solvent Attractions
similar IMAFs or ion–dipole
Attraction or Bond
Stronger with:
Molecular (IMAFs)
Hydrogen bonds
(if H with N , O , or F)
greater ∆EN
N<O<F
Dipole-dipole interactions
(polar molecules)
greater ∆EN
London dispersion forces
(all molecules & nonpolar)
instant/induced dipoles)
Ionic Bonds
(attractions between +/– ions)
greater dipole moment
larger e– cloud,
more polarizable
greater q, less d
(Coulombic attraction)
Attractions Affect
Physical Properties
The Stronger the Attractions, the…
higher mp of solid.
harder solid.
higher bp of liquid.
higher viscosity of liquid.
lower vapor pressure of liquid (more volatile).
more soluble in solutions (similar attractions).
Reasoning with Concepts
1) Identify attractions
(Bonds? IMAFs?)
2) Compare strength
+ –
3) Connect to energy (abs./rel.)
and/or physical property