Transcript Document

Intermolecular Forces and
Liquids and Solids
Chapter 12
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Kinetic Molecular Theory
Gas molecules are
1._______________________________,
2._______________________________, and
3._______________________________.
•Liquids and solids are quite different!
A ________________ is a homogeneous part of the
system in contact with other parts of the system but
separated from them by a well-defined boundary.
2 Phases
Solid phase - ice
Liquid phase - water
Characteristic Properties of Gases, Liquids, and Solids
12.1
_______________________ Forces
__________________ forces hold atoms together in a molecule.
_____________forces are attractive forces between molecules.
Intermolecular vs Intramolecular
•
41 kJ to vaporize 1 mole of water (inter)
•
930 kJ to break all O-H bonds in 1 mole of water (intra)
“Measure” of intermolecular force
Generally,
_____molecular
forces are much
weaker than
_____molecular
forces.
boiling point
melting point
DHvap
DHfus
DHsub
12.2
Intermolecular Forces
_________________ Forces
______________ forces between polar molecules
Orientation of Polar Molecules in a Solid
12.2
Intermolecular Forces
________________ Forces
_________ forces between an ion and a polar molecule
Ion-Dipole Interaction
12.2
Intermolecular Forces
___________________ Forces
____________________ forces that arise as a result of
temporary dipoles induced in atoms or molecules
ion-induced dipole interaction
dipole-induced dipole interaction
12.2
Intermolecular Forces
Dispersion Forces Continued
____________________________ is the ease with which the
electron distribution in the atom or molecule can be distorted.
Polarizability _____________ with:
•
greater number of electrons
•
more diffuse electron cloud
Melting Points of Similar
Nonpolar Compounds
Dispersion forces
usually
______________
with molar mass.
12.2
What type(s) of intermolecular forces exist
between each of the following molecules?
HBr
CH4
S
SO2
12.2
Intermolecular Forces
_________________ Bond
The _________________ is a special __________________
interaction between they hydrogen atom in a polar N-H, O-H,
or F-H bond and an electronegative O, N, or F atom.
A
H…B
or
A
H…A
A & B are ____, ____, or ____
12.2
Why is the hydrogen bond considered a
“special” dipole-dipole interaction?
Decreasing molar mass
Decreasing boiling point
p.375
12.2
Properties of Liquids
______________________ is the amount of energy required
to stretch or increase the surface of a liquid by a unit area.
Strong
intermolecular
forces
High
surface
tension
p.376
12.3
Properties of Liquids
__________________________________ is the intermolecular
attraction between like molecules
_________________ is an attraction between unlike molecules
Adhesion
Cohesion
p.377
12.3
Properties of Liquids
________________ is a measure of a fluid’s resistance to flow.
Viscosity of Some Common
Liquids at 20ºC
____________
intermolecular
forces
_________
viscosity
p.378
12.3
Water is Unique!
Maximum Density
____0C
Density of Water
Ice is __________ than water
12.3
A ___________________________ solid possesses rigid and
long-range order. In a crystalline solid, atoms, molecules or
ions occupy specific (predictable) positions.
An ____________________________ solid does not possess
a well-defined arrangement and long-range molecular order.
A _____________________________________ is the basic
repeating structural unit of a crystalline solid.
At lattice points:
lattice
point
Unit Cell
Unit cells in 3 dimensions
•
Atoms
•
Molecules
•
Ions
p.381
12.4
12.4
12.4
12.4
12.4
Shared by 8
unit cells
Shared by 2
unit cells
12.4
1 atom/unit cell
2 atoms/unit cell
4 atoms/unit cell
(8 x 1/8 = 1)
(8 x 1/8 + 1 = 2)
(8 x 1/8 + 6 x 1/2 = 4)
12.4
12.4
When silver crystallizes, it forms face-centered
cubic cells. The unit cell edge length is 408.7 pm.
Calculate the density of silver.
m
d=
V
V = a3 = (408.7 pm)3 = __________________
___ atoms/unit cell in a face-centered cubic cell
1 mole Ag
107.9 g
x
m = 4 Ag atoms x
= ___________
23
mole Ag 6.022 x 10 atoms
7.17 x 10-22 g
m
=
= ___________________
d=
-23
3
V
6.83 x 10 cm
Compare Ex 12.3, p.384
12.4
12.5
Extra distance = BC + CD = 2d sinq = nl
(Bragg Equation)
12.5
X rays of wavelength 0.154 nm are diffracted
from a crystal at an angle of 14.170. Assuming
that n = 1, what is the distance (in pm) between
layers in the crystal?
nl = 2d sin q
n=1
q = 14.170 l = 0.154 nm = 154 pm
nl
1 x 154 pm
=
= ____________
d=
2 x sin14.17
2sinq
12.5
Types of Crystals
p.385
________________ Crystals
• Lattice points occupied by cations and anions
• Held together by electrostatic attraction
• Hard, brittle, high melting point
• Poor conductor of heat and electricity
CsCl
ZnS
CaF2
12.6
Types of Crystals
p.386
________________ Crystals
• Lattice points occupied by molecules
• Held together by intermolecular forces
• Soft, low melting point
• Poor conductor of heat and electricity
12.6
Types of Crystals
p.387
_________________ Crystals
• Lattice points occupied by atoms
• Held together by covalent bonds
• Hard, high melting point
• Poor conductor of heat and electricity
carbon
atoms
diamond
graphite
12.6
Types of Crystals
p.387
_________________ Crystals
• Lattice points occupied by metal atoms
• Held together by metallic bond
• Soft to hard, low to high melting point
• Good conductor of heat and electricity
Cross Section of a Metallic Crystal
nucleus &
inner shell emobile “sea”
of e-
12.6
Types of Crystals
Types of Crystals and General Properties
p.385
12.6
An ____________________________ solid does not possess
a well-defined arrangement and long-range molecular order.
A _______ is an optically transparent fusion product of inorganic
materials that has cooled to a rigid state without crystallizing
Crystalline
quartz (SiO2)
Non-crystalline
quartz glass
12.7
T2 > T1
Condensation
Freezing
Deposition
Evaporation
Melting
Sublimation
Least
Order
Greatest
Order
12.8
The ______________________ vapor pressure is the
vapor pressure measured when a dynamic equilibrium
exists between condensation and evaporation
H2O (l)
H2O (g)
Dynamic Equilibrium
Rate of
Rate of
= evaporation
condensation
p.389
12.8
Before
Evaporation
At
Equilibrium
12.8
____________________________________ (DHvap)
is the energy required to vaporize 1 mole of a liquid.
Clausius-Clapeyron Equation
ln P = -
DHvap
RT
P = (equilibrium) vapor pressure
+C
T = temperature (K)
R = gas constant (8.314 J/K•mol)
12.8
The ___________________ is the temperature at which
the (equilibrium) vapor pressure of a liquid is equal to
the external pressure (on the surface of the liquid).
The ________________________ is the temperature at
which a liquid boils when the external pressure is 1 atm.
Molar Heats of Vaporization for Selected Liquids
remember
12.8
The ____________________________________ (Tc) is the
temperature above which the gas cannot be made to liquefy,
no matter how great the applied pressure.
Critical Temperatures and Critical
Pressures of Selected Substances
The ______________
(Pc) is the minimum
pressure that must be
applied to bring about
liquefaction at the
critical temperature.
12.8
The ___________ point of a
solid or the _____________
point of a liquid is the temperature at which the solid
and liquid phases coexist in
equilibrium
p.395
Freezing
H2O (l)
Melting
H2O (s)
12.8
______________________ (DHfus) is the energy
required to melt 1 mole of a solid substance.
Molar Heats of Fusion for Selected Substances
remember
12.8
12.8
_________________________
(DHsub) is the energy required
to sublime 1 mole of a solid.
Deposition
H2O (g)
Sublimation
H2O (s)
DHsub = DHfus + DHvap
( Hess’s Law)
12.8
A __________________ summarizes the conditions
at which a substance exists as a solid, liquid, or gas.
Phase Diagram of Water
Triple Point
12.8
The _______________________ is the
only temperature and pressure where all
three phases can exist in equilibrium.
p.395
Triple Point
12.8