Chapter 12 Power Point 5e HP

8/4/2019 Chapter 12 Power Point 5e HP

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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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Body-centeredCubic

Coordination number = 8


1 atom at

center

Atoms/unit cell = (1/8 x 8) + 1 = 2


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Face-centeredCubic

Coordination number = 12Atoms/unit cell = (1/8 x 8) + (1/2 x 6) = 4


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

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-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.




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Figure B12.2

Formation of an x-ray diffraction pattern of the

protein hemoglobin.



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Figure B12.3 Scanning tunneling micrographs.

G ld fCesium atoms on gallium

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Chapter 12 Power Point 5e HP