Liquids and Solids

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Chapter 16

• Liquids and Solids

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Chapter 16 Liquids and Solids

• 16.1 Intermolecular Forces
• 16.2 The Liquid State
• 16.3 An Introduction to Structures and Types
  of Solids
• 16.4 Structure and Bonding in Metals
• 16.5 Carbon and Silicon Network Atomic
  Solids
• 16.6 Molecular Solids
• 16.7 Ionic Solids
• 16.8 Structures of Actual Ionic Solids
• 16.9 Lattice Defects
• 16.10 Vapor Pressure and Changes of State
• 16.11 Phase Diagrams

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Red Beryl, Be3Al2Si6O18-
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Figure 16.1 Schematic representation of the
three states of matter
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Figure 16.2 (a) The electrostatic interaction
of two polar molecules. (b) The interaction of
many dipoles in a condensed state.
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Figure 16.3 The polar water molecule.
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Figure 16.4 The boiling points of the covalent
hydrides of elements in Groups 4A, 5A, 6A, and 7A.
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Figure 16.5 An instantaneous polarization can
occur on atom a, creating instantaneous dipole.
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Relative Strength of Intermolecular Forces
Ion - Ion Forces
Strongest Attractive Forces Ion -
Dipole Forces Dipole - Dipole Forces Ion -
Induced Dipole Forces Dipole - Induced Dipole
Forces London - Dispersive Forces
Weakest Attractive Forces
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Figure 16.6 A molecule in the interior of a
liquid is attracted to the molecules surrounding
it, whereas a molecule at the surface of liquid
is attracted only by molecules below it and on
each side of it.
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Figure 16.7 Nonpolar liquid mercury forms a
convex meniscus in a glass tube.
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Figure 16.8 Several crystalline solids
Fluorite
Rhodochrosite
Pyrite
Amethyst
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Figure 16.9 Three cubic unit cells and the
corresponding lattices.
Simple Cubic Body-centered
Cubic Face-centered Cubic
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Figure 16.10 X-rays scattered from two
different atoms may reinforce (constructive
interference) or cancel (destructive
interference) one another.
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Figure 16.11 Reflection of X rays of wavelength

Bragg equation nl 2d sinJ
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A conch shell on a beach.
Source Corbis
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Figure 16.12 Examples of three types of
crystalline solids.
Elemental Ionic
Molecular Solid Solid
Solid
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The Hexagonal Structure of Ice
Ice Structure with open holes giving Ice a
density less than water its self.
The delicate 6 point snow flake reflects the
hexagonal structure.
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Figure 16.13 The closet packing arrangement of
uniform spheres.
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Figure 16.14 When spheres are closest packed so
that the spheres in the third layer are directly
over those in the first layer (aba), the unit
cell is the hexagonal prism illustrated here in
red.
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Figure 16.15 When spheres are packed in the abc
arrangement, the unit cell is face-centered cubic.
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A toy slide puzzle
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A section of a surface containing copper atoms
(red) and an indium atom (yellow).
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Figure 16.17 The net number of spheres in a
face-centered cubic unit cell.
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Figure 16.16 The indicated sphere has 12
equivalent nearest neighbors.
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Example 16.1 (P 780) Silver crystallizes in a
cubic close packed structure. The radius of a
sliver atom is 1.44A (14 pm). Calculate the
density of Ag. Density mass per unit volume.
Use the Pythagorean theorem to calculate the edge
of the cube d and then the cubic volume.
d2 d2 (4r)2 d 8r2 r
8 since r 1.44 A
d 1.44 A ( 8 ) 4.07 A Volume of the unit
cell d3 (4.07 A) 67.4 A3 67.4 A3 x (
)3 6.74 x 10-23 cm3 In
the face-centered cubic there are 4 atoms per
cell Density Density _________ g/cm3

1.00 x 10-8 cm A
(4 atoms)(1.07.9 g/mol)(6.022 x 1023
atoms/mol) 6.74 x 10-23 cm3
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Volume of a unit cell (2r, 4r, r)
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Figure 16.18 In the body-centered cubic unit
cell the spheres touch along the body diagonal.
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Figure 16.19 The body-centered cubic unit cell
with the center sphere deleted.
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Figure 16.20 On the face of the body-centered
cubic unit cell.
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Figure 16.21 The relationship of the body
diagonal (b) to the face diagonal (f) and the
edge (e) for the body-centered cubic unit cell.
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Figure 16.22 The electron sea model for metals
postulates a regular array of cations in a "sea"
of valence electrons.
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Figure 16.23 The molecular orbital energy
levels produced when various numbers of atomic
orbitals interact.
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Figure 16.24 A representation of the energy
levels (bands) in a magnesium crystal
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Grains of nanophase palladium magnified 200,000
times by an electron microscope.
Source Nanophase Technologies Corporation
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Metal Alloys
Alloy a substance that contains mixture of
elements and has metallic
properties Substitutional alloy some host metal
atoms are replaced by other atoms
of similar size Brass
66 copper, 33 zinc (fig 16.25a)
Sterling silver 93 silver, 7 copper
Pewter 85 tin, 7 copper, 6 bismuth, and 2
antimony Plumbers solder 67 lead, 33
tin Interstitial alloy some of the interstices
(holes) are filled by smaller atoms Mild
steels gt0.2 carbon Medium steels 0.2-0.6
carbon, High carbon steels 0.6-1.5 carbon
(fig 16.25b)
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Figure 16.25 Two types of alloys
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Figure 16.26 The structures of (a) diamond
(b) graphite(c) fullerenes
a)
c)
b)
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Figure 16.27 Partial representation of the MO
energies in (a) diamond and (b) a typical metal
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Graphite consists of layers of carbon atoms.
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Figure 16.28 The p orbitals (a) perpendicular
to the plane of the carbon ring system in
graphite can combine to form (b) an extensive pie
bonding network.
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Figure 16.29 The structure of quartz
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Figure 16.30 Examples of silicate anions, all
of which are based on SiO44- tetrahedra
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Figure 16.31 Two-dimensional reprentations of
(a) a quartz crystal and (b) a quartz glass.
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Ceramics
Ceramics are a class of nonmetallic materials
that are strong, brittle, and resistant to heat
and attack by chemicals. A ceramic is a
heterogeneous mixture of crystals of silicates
that are surrounded by a glassy
cement. Aluminosilicate Aluminum and silicon
take part in the oxygen-bridged
polyanion. Feldspar, is a mixture
silicates with empirical formulas such as
K2O Al2O3 6 SiO2 and Na2O Al2O3 6SiO2
Weathering of Feldspar produces the mineral
Kaolinite a clay Al2Si2O5(OH)4 consisting
of tiny platelets that in the presence of
water can slide over each other. When
clays are fired in an oven at high
temperatures, the water is driven off and
a glass is formed that binds the kaolinite
crystals together.
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Semiconductors
In silicon, unlike carbon, the conduction band is
closer in energy to the filled MOs, and a few
electrons can cross the energy gap at 25oC,
making silicon a semiconducting element, or
semiconductor. The small conductivity of
silicon can be increased by doping the
silicon crystal with other elements n-type
semiconductor Doped with Arsenic with an extra
electron. p-type semiconductor Doped with
Boron with one less valence
electron than silicon or
hole. These doped semiconductors have enhanced
conduction, and by combining n and p
semiconductors we have a p-n junction.
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Figure 16.32 A silicon crystal doped with
arsenic, which has one extra valence electron.
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Figure 16.33 Energy-level diagrams for (a) an
n-type semiconductor and (b) a p-type
semiconductor.
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Figure 16.34 The p-n junction involves the
contact of a p-type and an n-type semiconductor.
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Kelvins Highest knownsuperconducting temperatures
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High Temperature Superconductors
at 77K (LN2) Generalized Formula of
perovskites YBa2Cu3Ox Where x
6.527
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A magnet is levitated over a superconducting
ceramic immersed in liquid nitrogen.
Source Phototake
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The levitating power of a superconducting oxide
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Golf clubs with a titanium shell and metallic
glass inserts.
Source Liquid Metal Golf
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A schematic of two circuitsconnected by a
transistor.
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Steps to form a Transistor in Pure Silicon - I

• The chip begins as a thin wafer of silicon that
  has ben doped with an
• n-type impurity. A protective layer of
  silicon dioxide is then produced
• on the wafer by exposing it in a furnace to
  an oxidizing atmosphere.
• The next step is to produce a p-type
  semiconductor. In this step the
• surface of the oxide is covered by a
  light-sensitive wax.
• A template that allows light to shine through
  only in selected areas is
• then placed on top, and the chip is exposed
  to light. The wax that has
• been expose to light undergoes a chemical
  change that causes its
• solubility to be different from the
  unexposed wax.
• The unexposed wax is dissolved by using selective
  solvents, and the
• exposed area is treated with an etching
  solution to dissolve the oxide
• coating.
• When the remaining wax is dissolved, the silicon
  wafer has its oxide
• coating intact except at the one spot (of
  diameter x), as shown.

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(a)-(h) The steps for forming a transistor in a
crystal of initially pure silicon.
a) The chip begins as a thin wafer of silicon
that has been doped with an n-type
impurity. A protective layer of silicon
dioxide is then produced on the wafer by
exposing it in a furnace to an oxidizing
atmosphere.
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Steps to form a Transistor in Pure Silicon - II

• Exposing the wafer to a p-type impurity such as
  boron at about 1000oC
• causes a p-type semiconductor area to be
  formed in the exposed spot
• as the boron atoms diffuse into the silicon
  crystal.
• f) For the formation of a small n-type area in
  the center of the p-type
• region, the wafer is again placed in the
  oxidizing furnace to be
• recoated over its entire surface with oxide.
  Then a new wax covering
• is applied, which is illuminated through a
  template with a transparent
• area indicated by part y in the template.
• g) The wax and oxide are then removed from the
  illuminated area, and the
• wafer is exposed to an n-type impurity to
  form a small n-type region,
• as shown.
• Finally conductors are layered onto the chip,
  giving the finished
• transistor, ehich has two circuits
  connected through an n-p-n junction.
• This transistor then becomes a part of a
  larger circuit layered onto the
• chip and interconnected by conductors.

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(a)-(h) The steps for forming a transistor in a
crystal of initially pure silicon. (contd)
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A new IBM microchip featuring silicon on a
"blanket" of insulating material to protect it
from temperature changes.
Source IBM Corporation
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Figure 16.35 Sulfur crystals (yellow) contain
S8 molecules. (right) White phosphorous contains
P4 molecules. It is so reactive with the oxygen
in air that it must be stored under water.
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Figure 16.36 The holes that exist among
closest packed uniform spheres
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Figure 16.37 (a) The octahedral hole (shown in
yellow) lies at the center of six spheres that
touch along the edge (e) of the square.
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Figure 16.38 (a) The tetrahedral hole (b) The
center of the tetrahedral hole
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Figure 16.39 One packed sphere and its
relationship to the tetrahedral hole
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Figure 16.40 (a) A simple cubic array with X-
ions, with an M ion in the center (in the cubic
hole). (b) The body diagonal b equals
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Figure 16.41 (a) The location (x) of a
tetrahedral hole in the face-centered cubic unit
cell.(b) one of the tetrahedral (c) the unit cell
(d) The alternate tetrahedral

1. Face Centered Cubic structure showing one
   tetrahedral hole location.
2. Tetrahedral hole (x) in the Tetrahedral
   structure.
3. Zinc Sulfide (ZnS) with the zinc atoms on the
   holes.
4. Calcium Fluoride (CaF2) with the Ca ions in the
   holes.

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Figure 16.42 The locations (gray x) of the
octahedral holes in the face-centered cubic unit
cell.
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Figure 16.43 Defects in crystalline ionic
solids
Frenkel defects atom or ion at wrong
location
Schottky defects Vacant sites
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Figure 16.44 Behavior of a liquid in a closed
container
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Figure 16.45 The rates of condensation and
evaporation over time for a liquid sealed in a
closed container.
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Figure 16.46 The vapor pressure of a liquid
can be measured easily using a simple barometer
of the type shown here.
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Figure 16.47 The number of molecules in a
liquid with a given energy versus kinetic energy
at two temperatures.
a) Lower temperature b) Higher
temperature
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Figure 16.48 The vapor pressure of water,
ethanol, and diethyl ether as a function of
temperature.
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The Linear behavior of Vapor Pressure vs. Temp!
We will use the equation for the vapor pressure
of a compound vs. temperature to derive an
equation for two temperatures.
ln(PT1vap) C ln(PT2vap)
Which can be rearranged into
ln(PT1vap) ln(PT2vap) ( -
) Or ln( )
( - )
Hvap RT1
Hvap RT2
Hvap R
1 1 T2 T1
Hvap R
PT1vap PT2vap
1 1 T2 T1
This equation is often referred to as the
Clausius Claperon equation in most text books,
and is used to calculate the vapor pressures at
different Temperatures, or calculate Hvap from
data on vapor pressures.
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Problem Calculate the heat of Vaporization of
diethyl ether From the following vapor
pressures 400. Mm Hg at 18oC 760. Mm Hg at
35oC Plan We are given P1, P2, T1, and T2
substitute into the Clausious-Claperon equation
and calculate the value of Hvap ! Solution
T1 18oC 273 K 291 K
T2 35oC 273 K 308 K Ln ( )
( - ) Ln (
) Ln 1.90 _____________
0.6418 ( -
) 0.6418
(-0.00019 K) Hvap __________
J/mol _________ kJ/mol
P1 P2
- Hvap R
1 T1
1 T2
760 mm Hg 400 mm Hg
- Hvap 8.31 J/mol K
1 1 308 291
- Hvap 8.31 J/mol K
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100.0 760.0
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Figure 16.49 Iodine being heated, causing it to
sublime onto an evaporating dish cooled by ice.
Source Stock Boston
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Figure 16.50 The heating curve for a given
quantity of water where energy is added at a
constant rate.
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Figure 16.51 The vapor pressures of solid and
liquid water as a function of temperature.
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Figure 16.52 An apparatus that allows solid and
liquid water to interact only through the vapor
state.
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Figure 16.53 Water in a closed system with a
pressure of 1 atm exerted on the piston.
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Figure 16.54 The supercooling of water.
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A boiling chip releasing air bubbles acts as a
nucleating agent for the large bubbles that form
when water boils.
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Gases
Sublimation
Deposition
Condensation H0vap - 40.7 kJ/mol
H0sub
- H0sub
Vaporization H0vap 40.7 kJ/mol
Liquids
Freezing H0fus -6.02 kJ/mol
Melting H0fus 6.02 kJ/mol
Deposition
Sublimation
Solids
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Figure 16.55 The phase diagram for water
Triple point
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Figure 16.53 Water in a closed system with a
pressure of 1 atm exerted on the piston.
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Temperature (oC)
Heating curve for Experiment 1 - 20oC to 160oC
at 1.0 atm, 760 torr
100 oC
Boiling
0 oC
Melting
Time with a constant energy input
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Temperature (oC)
100 oC
0 oC
Heating curve for Experiment 2 - 20oC to
160oC at 2.0 torr, 0.0026 atm
Sublimation
Time with a constant energy input
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Temperature (oC)
100 oC
Heating curve for Experiment 3 - 20oC to
140oC at 4.588 torr, .0060 atm
0 oC
Triple point 0.0098oC and 4.588 torr
Time with a constant energy input
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Figure 16.56 Diagrams of various heating
experiments on samples of water in closed
systems.
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Figure 16.57 The phase diagram for water
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Figure 16.58 The phase diagram for carbon
dioxide
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The phase diagram for carbon
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