chapter 12 power point 5e hp
TRANSCRIPT
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Lecture PowerPoint
ChemistryThe Molecular Nature ofMatter and Change
Fifth Edition
Martin S. Silberberg
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Chapter 12
Intermolecular Forces:
Liquids, Solids, and Phase Changes
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Intermolecular Forces:
Liquids, Solids, and Phase Changes
12.1 An Overview of Physical States and Phase Changes
12.2 Quantitative Aspects of Phase Changes
12.3 Types of Intermolecular Forces
12.4 Properties of the Liquid State
12.5 The Uniqueness of Water
12.6 The Solid State: Structure, Properties, and Bonding
12.7 Advanced Materials
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Phase Changes
solid liquid gas
melting
freezing
vaporizing
condensing
sublimination
endothermic
exothermic
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Table 12.1
A Macroscopic Comparison of Gases, Liquids, and Solids
State Shape and Volume Compressibility Ability to Flow
Gas Conforms to shape and volume
of container
high high
Liquid Conforms to shape of container;volume limited by surface
very low moderate
Solid Maintains its own shape andvolume
almost none almost none
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Figure 12.1
Heats of vaporization and fusion for several common substances.
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Figure 12.2 Phase changes and their enthalpy changes.
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Figure 12.3
A cooling curve for the conversion of gaseous water to ice.
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Within a phase, a change in heat is accompanied by a change intemperature which is associated with a change in average Ek asthe most probable speed of the molecules changes.
Quantitative Aspects of Phase Changes
During a phase change, a change in heat occurs at a constanttemperature, which is associated with a change in Ep, as theaverage distance between molecules changes.
q = (amount)(molar heat capacity)(T)
q = (amount)(enthalpy of phase change)
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Sample Problem 12.1 Finding the Heat of a Phase Change Depicted byMolecular Scenes
SOLUTION:
PROBLEM: These molecular scenes represent a phase change of water. Selectdata from the previous text discussion to find the heat (in kJ) lost or
gained when 24.3 g of H2O undergoes this change.
PLAN: The scenes show a disorderly, condensed phase (liquid) changing toseparate molecules (gas) and represent the vaporization of water. Threeendothermic stages: (1) heating liquid 85.0 to 100.oC, (2) liquid to gas at100.oC, and (3) heating gas 100. to 117oC.
mol H2O = 24.3 g H2O xmol H2O
18.02 g H2O
= 1.35 mol H2O
q= nx Cwater(l) x T= (1.35 mol)(75.4 J/moloC)(100. 85.0oC) = 1527 J = 1.53 kJ
q= nx Cwater(g) x T= (1.35 mol)(33.1 J/moloC)(117 100.oC) = 759.6 J = 0.760 kJ
q= n(Hovap) = (1.35 mol)(40.7 kJ/mol) = 54.9 kJ
qtotal = 1.53 + 54.9 + 0.760 kJ = 57.2 kJ
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Figure 12.4 Liquid-gas equilibrium.
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Figure 12.5The effect of temperature on the distribution of
molecular speed in a liquid.
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ATTRACTIVE FORCES
electrostatic in nature
Intramolecular forces bonding forces
These forces exist withineach molecule.They influence the chemicalproperties of the substance.
Intermolecular forces nonbonding forces
These forces exist betweenmolecules.They influence the physicalproperties of the substance.
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Figure 12.6 Figure 12.7
Vapor pressure as a functionof temperature and
intermolecular forces.
A linear plot of therelationship between vapor
pressure and temperature.
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The Clausius-Clapeyron Equation
C
TR
HP
1-=ln
vap
12
vap
1
2 11-
=ln TTR
H
P
P
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Sample Problem 12.2 Using the Clausius-Clapeyron Equation
SOLUTION:
PROBLEM: The vapor pressure of ethanol is 115 torr at 34.9oC. If Hvap of
ethanol is 40.5 kJ/mol, calculate the temperature (in oC) whenthe vapor pressure is 760 torr.
PLAN: We are given 4 of the 5 variables in the Clausius-Clapeyronequation. Substitute and solve for T2.
12
vap
1
2 11-=lnTTR
H
P
P34.9oC + 273.15 = 308.0 K
ln760 torr
115 torr=
- 40.5 x103 J/mol
8.314 J/molK
1
T2
1
308.0 K
T2 = 350. K 273.15 = 77C
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Figure 12.8 Iodine subliming.
iodine solid
iodine vapor
iodine solid
test tube with ice
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Figure 12.9 Phase diagrams for CO2 and H2O.
CO2 H2O
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bond length
covalent radius
van der Waals distance
van der Waals radius
Figure 12.10 Covalent and van der Waals radii.
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Figure 12.11
Periodic trends in covalent and van der Waals radii (in pm).
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Figure 12.12 Polar molecules and dipole-dipole forces.
solid
liquid
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Figure 12.13 Dipole moment and boiling point.
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(Intramolecular) Forces
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THE HYDROGEN BOND
a dipole-dipole intermolecular force
The elements which are so electronegative are N, O, and F.
A hydrogen bond may occur when an H atom in a molecule,bound to small highly electronegative atom with lone pairs ofelectrons, is attracted to the lone pairs in another molecule.
..F..
.
.
..H O..
N.
.
FH.
.
..
..
O..
.
.
..NH
hydrogen bond
donor
hydrogen bondacceptor
hydrogen bond
acceptor
hydrogen bonddonor
hydrogen bond
donor
hydrogen bond
acceptor
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Figure 12.14 Hydrogen bonding and boiling point.
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Sample Problem 12.3 Drawing Hydrogen Bonds Between Moleculesof a Substance
SOLUTION:
PROBLEM: Which of the following substances exhibits H bonding? For
those that do, draw two molecules of the substance with the Hbond(s) between them.
C2H6(a) CH3OH(b) CH3C NH2
O
(c)
PLAN: Find molecules in which H is bonded to N, O, or F. Draw Hbonds in the format B: HA.
(a) C2H6 has no H bonding sites.
(c)(b)C O H
H
H
H
COH
H
H
H
CH3C N
O
H
H
CH3
CN
O
H
H
CH3CN
O
H
H
CH3O
N
O
H
H
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Polarizability and Charged-Induced Dipole Forces
distortion of an electron cloud
Polarizability increases down a group
size increases and the larger electron clouds are furtherfrom the nucleus
Polarizability decreases left to right across a period
increasing Zeff shrinks atomic size and holds the electronsmore tightly
Cations are less polarizable than their parent atombecause they are smaller.
Anions are more polarizable than their parent atombecause they are larger.
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Figure 12.15 Dispersion forces among nonpolar particles.
separatedAr
molecules
instantaneousdipoles
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Figure 12.16
Molar mass and boiling point.
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Figure 12.17 Molecular shape and boiling point.
more points fordispersion
forces to act
fewer points fordispersionforces to act
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Figure 12.18
Summary diagram for analyzing the intermolecular forces in a sample.
INTERACTING PARTICLES(atoms, molecules, ions)
ions only
IONIC BONDING(Section 9.2)
ion + polar moleculeION-DIPOLE FORCES
ions present ions not present
polar molecules only
DIPOLE-DIPOLEFORCES
HYDROGENBONDING
polar + nonpolar
moleculesDIPOLE-INDUCED DIPOLEFORCES
nonpolar
molecules onlyDISPERSIONFORCES only
DISPERSION FORCES ALSO PRESENT
H bonded toN, O, or F
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Sample Problem 12.4 Predicting the Types of Intermolecular Force
PROBLEM: For each pair of substances, identify the dominant
intermolecular force(s) in each substance, and select thesubstance with the higher boiling point.
(a) MgCl2 or PCl3
(b) CH3NH2 or CH3F
(c) CH3OH or CH3CH2OH
(d) Hexane (CH3CH2CH2CH2CH2CH3)
or 2,2-dimethylbutaneCH3CCH2CH3
CH3
CH3PLAN: Use the formula, structure, Table 12.2 (button) and Figure 12.18.
Bonding forces are stronger than nonbonding (intermolecular) forces.
Hydrogen bonding is a strong type of dipole-dipole force.
Dispersion forces are decisive when the difference is molar mass ormolecular shape.
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SOLUTION:
Sample Problem 12.4 Predicting the Types of Intermolecular Force
(a) Mg2+ and Cl are held together by ionic bonds while PCl3 is covalentlybonded and the molecules are held together by dipole-dipole interactions. Ionicbonds are stronger than dipole interactions and so MgCl2 has the higher boilingpoint.
(b) CH3NH2 and CH3F are both covalent compounds and have bonds which arepolar. The dipole in CH3NH2 can H bond while that in CH3F cannot. ThereforeCH3NH2 has the stronger interactions and the higher boiling point.
(c) Both CH3OH and CH3CH2OH can H bond but CH3CH2OH has more CH formore dispersion force interaction. Therefore CH3CH2OH has the higher boiling
point.(d) Hexane and 2,2-dimethylbutane are both nonpolar with only dispersionforces to hold the molecules together. Hexane has the larger surface area,thereby the greater dispersion forces and the higher boiling point.
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Figure 12.19 The molecular basis of surface tension.
hydrogen bondingoccurs in three
dimensions
hydrogen bondingoccurs across the surface
and below the surfacethe net vectorfor attractive
forces is downward
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Table 12.3 Surface Tension and Forces Between Particles
Substance Formula
Surface Tension
(J/m2) at 200C Major Force(s)
diethyl ether
ethanol
butanol
water
mercury
dipole-dipole; dispersion
H bonding
H bonding; dispersion
H bonding
metallic bonding
1.7x10-2
2.3x10-2
2.5x10-2
7.3x10-2
48x10-2
CH3CH2OCH2CH3
CH3CH2OH
CH3CH2CH2CH2OH
H2O
Hg
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Surface Tension in liquid Mercury (Hg)
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Figure 12.20 Shape of water or mercury meniscus in glass.
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Table 12.4 Viscosity of Water at Several Temperatures
Temperature (oC)Viscosity(Ns/m2)*
20
40
60
80
1.00x103
0.65x103
0.47x103
0.35x103
*The units of viscosity are Newton-seconds per square meter.
viscosityresistance to flow
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Figure 12.21 The H-bonding ability of the water molecule(forms a tetrahedral shape).
hydrogen bond donor
hydrogen bond acceptor
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The Unique Nature of Water
great solvent properties due to polarity and
hydrogen bonding ability
exceptional high specific heat capacity
high surface tension and capillarity
density differences of liquid and solid states
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Figure 12.22 The hexagonal structure of ice.
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Figure 12.23 The expansion and contraction of water.
Th i ti f t d th i t i
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Figure 12.24The macroscopic properties of water and their atomic
and molecular roots.
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Figure 12.25 The striking beauty of crystalline solids.
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portion of 3-D lattice
Figure 12.26 The crystal lattice and the unit cell.
lattice point
unit
cell
unit
cell
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Figure 12.27 (1 of 3) The three cubic unit cells.
Simple Cubic
Coordination number = 6
Atoms/unit cell = 1/8 x 8 = 1
1/8 atom at8 corners
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Figure 12.27 (2 of 3) The three cubic unit cells.
Body-centeredCubic
Coordination number = 8
1/8 atom at8 corners
1 atom at
center
Atoms/unit cell = (1/8 x 8) + 1 = 2
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Figure 12.27 (3 of 3) The three cubic unit cells.
Face-centeredCubic
Coordination number = 12Atoms/unit cell = (1/8 x 8) + (1/2 x 6) = 4
1/8 atom at8 corners
1/2 atom at
6 faces
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Figure 12.28 Packing identical spheres.
simple cubic
(52% packing efficiency)
body-centered cubic
(68% packing efficiency)
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hexagonal
unit cell
Figure 12.28 (continued)
closest packing of firstand second layers
layer a
layer a
layer b
layer c
hexagonal
closest
packingcubic closest
packing
abab (74%)abcabc (74%)
expanded
side views
face-centered
unit cell
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Figure 12.29 Edge length and atomic (ionic) radius inthe three cubic unit cells.
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Sample Problem 12.5 Determining Atomic Radius from Crystal Structure
PROBLEM: The crystal structure of copper adopts cubic closest packing
and the edge length of the unit cell is 361.5 pm What is theatomic radius of copper?
PLAN: Copper has a face-centered cubic unit cell with edge length A = 361.5pm see Figure 12.29C. The diagonal of the cells face is 4rand thePythagorean theorem can be used to solve for r.
SOLUTION: 22=C BA
pmpmA 2.511)5.361(22C 22
C = 4r r = C/4 = 511.2 pm/4 = 127.8 pm
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Figure 12.30 Figure 12.31
Cubic closest packing forfrozen argon.
Cubic closest packingof frozen methane.
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Table 12.5 Characteristics of the Major Types of Crystalline Solids
Particle(s)InterparticleForces
PhysicalProperties Examples (mp,
oC)
Atomic
Molecular
Ionic
Metallic
NetworkCovalent
Group 8A(18)
[Ne(-249) to Rn(-71)]
Molecules
Positive &negative ions
Atoms
Atoms
Soft, very low mp, poorthermal & electricalconductors
DispersionAtoms
Dispersion,dipole-dipole,H bonds
Fairly soft, low to moderatemp, poor thermal &electrical conductors
Nonpolar:O2[-219],C4H10[-138], Cl2 [-101],C6H14[-95], P4 [44.1]
Polar: SO2[-73],CHCl3[-64], HNO3[-42], H2O
[0.0], CH3COOH[17]
Covalent bond
Metallic bond
Ion-ion
attraction
Very hard, very high mp,usually poor thermal and
electrical conductors
Soft to hard, low to veryhigh mp, excellent thermaland electrical conductors,malleable and ductile
Hard & brittle, high mp,good thermal & electricalconductors when molten
NaCl [801]
CaF2 [1423]
MgO [2852]
Na [97.8]
Zn [420]
Fe [1535]
SiO2 (quartz) [1610]
C (diamond) [~4000]
Type
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Figure 12.32 The sodium chloride structure.
expanded view space-filling
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Figure 12.33 The zinc blende structure.
zinc sulfide (ZnS)
Th fl it (C F ) t t
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Figure 12.34 The fluorite (CaF2) structure.
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Figure 12.35 Crystal structures of metals.
cubic closest packing hexagonal closest packing
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Figure 12.36 Crystalline and amorphous silicon dioxide.
Figure 12 37 The band of molecular orbitals in lithium metal
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Figure 12.37 The band of molecular orbitals in lithium metal.
Figure 12 38
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Figure 12.38
Electrical conductivity in a conductor, semiconductor, and insulator.
conductor semiconductor insulator
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Figure 12.39
The levitating power of a superconducting oxide.
rare earth magnet
superconducting ceramic disk
liquid nitrogen
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Figure 12.40
Crystal structures and bandrepresentations of doped
semiconductors.
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Forward bias
Reverse bias
p-n junctionFigure 12.41 The p-n junction.
Figure 12 42 Structures of two typical molecules that
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Figure 12.42 Structures of two typical molecules thatform liquid crystal phases.
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Figure 12.43 The three common types of liquid crystal phases.
nematic smecticcholesteric
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Figure 12.45
Schematic of a liquidcrystal display (LCD).
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Figure 12.44 Liquid crystals in biological systems.
nematic arrays oftobacco mosaic virus particles
actin and myosin proteinfilaments in voluntary muscle cells
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Table 12.7 Some Uses of Modern Ceramics and Ceramic Mixtures
Ceramic Applications
SiC, Si3N4, TiB2, Al2O3 Whiskers (fibers) to strengthen Al and other ceramics
Si3N4 Car engine parts; turbine rotors for turbo cars;electronic sensor units
Si3N4, BN, Al2O3 Supports or layering materials (as insulators) inelectronic microchips
SiC, Si3N4, TiB2, ZrO2,Al2O3, BN
ZrO2, Al2O3
Cutting tools, edge sharpeners (as coatings andwhole devices), scissors, surgical tools, industrialdiamond
BN, SiC Armor-plating reinforcement fibers (as in Kevlarcomposites)
Surgical implants (hip and knee joints)
Figure 12.46 Expanded view of the atom arrangements in some
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modern ceramic materials.
SiC
siliconcarbide
BN
cubic boronnitride
(borazon)
YBa2Cu3O7
hightemperaturesuperconductor
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Table 12.8 Molar Masses of Some Common Polymers
Name Mpolymer (g/mol) n Uses
Acrylates 2 x105 2 x103 Rugs, carpets
Polyamide (nylons) 1.5 x104 1.2 x102 Tires, fishing line
Polycarbonate 1 x105 4 x102 Compact discs
Polyethylene 3 x105 1 x104 Grocery bags
Polyethylene (ultra-high molecular weight)
5 x106 2 x105 Hip joints
Poly(ethylene
terephthalate)
2 x104 1 x102 Soda bottles
Polystyrene 3 x105 3 x103 Packing; coffee cups
Poly(vinyl chloride) 1 x105 1.5 x103 Plumbing
Figure 12.47 The random-coil shape of a polymer chain.
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Figure 12.47 p p y
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Figure 12.48 The semicrystallinity of a polymer chain.
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Figure 12.49 The viscosity of a polymer in solution.
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Table 12.9 Some Common Elastomers
Name Tg(oC)*
*Glass transition temperature
Uses
Poly (dimethyl siloxane) -123
-106
-65
-43
Polybutadiene
Polyisoprene
Polychloroprene (neoprene)
Breast implants
Rubber bands
Surgical gloves
Footwear, medical tubing
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Figure 12.50 The colors of quantum dots.
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Figure 12.51 The magnetic behavior of a ferrofluid.
D i i
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Figure 12.52 Driving a nanocar.
Tools of the Laboratory
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Figure B12.1
Diffraction of x-rays by crystal planes.
Tools of the Laboratory
Tools of the Laboratory
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Figure B12.2
Formation of an x-ray diffraction pattern of the
protein hemoglobin.
Tools of the Laboratory
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Tools of the Laboratory
Figure B12.3 Scanning tunneling micrographs.
G ld fCesium atoms on gallium