States of MatterEdward A. Mottel

Department of Chemistry

Rose-Hulman Institute of Technology

04/18/23

States of Matter

Reading assignment: Fine, Beall & Stuehr, Chapter 9.1-9.2, 16.6, 17.2, 17.4-17.5,

Phases of matter Molecular interactions Atomic measurements

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Phases of MatterPhase Characteristics Structure Examples

Gas fills any volume minimal order He, O3, UF6

Liquid fills a specificvolume

short rangeordering

Br2, H2ON2(l), glass

Solid atoms &molecules in

fixed positions

crystallineshort & long

range ordering

amorphous short rangeordering

NaCl, sucrosepolyethylene

clearpolypropylene

Plasma atomicparticles no ordering nuceli &

electrons

What types of materials can you see through clearly?

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Phase Diagram

Indicates the stable phases of a compound as a function of• temperature• pressure

Points on the line indicate an equilibrium condition involving two or more phases.

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Phase DiagramWater

Temperature

Pre

ssu

re

gas

liquidvapor pressure line

solid

liquid

solid gasnormalboiling point

1

normalmeltingpoint

triple point(+0.01 °C, 0.006 atm)

critical point(374 °C, 218.3 atm)

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Phase DiagramWater

Temperature

Pre

ssu

re

gas

liquid

solidnormalboiling point

1

normalmeltingpoint

triple point(+0.01 °C, 0.006 atm)

critical point(374 °C, 218.3 atm)

Identify the process of boiling.Identify the process of sublimation.

How are the densities of water and ice related?What occurs beyond the critical point?

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Carbon Dioxide

Carbon dioxide facts• Triple point: -57 °C, 5.2 atm• Critical point: 31 °C, 72.9 atm

• Solid CO2 sinks in liquid CO2

Draw a phase diagram of carbon dioxide.

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Phase DiagramCarbon Dioxide

Pre

ssu

re

Temperature

1

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Phase DiagramCarbon Dioxide

Pre

ssu

re

Temperature

gas

liquid

1

solid

Why is solid carbon dioxide called “dry ice”?

Application: supercritical fluid

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Atomic and Molecular Interactions

SpeciesType of

Interaction Method of InteractionStrength ofInteraction(kJ mol-1)

atoms /ions

covalentbonds

sharing of electronsbetween atoms

single, double, triplebonds

Single: 140-440Double: 350-800Triple: 800-950

ionicbonds

electrostatic attractionnon-directional bonding E = k (q+ q- ) / d

dipole-dipoleH-bond:5-50

others weakeratoms /ions /

molecules

van der Waalforces

dipole-induced dipole weak

dispersion forces very weak

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Covalent BondsElectrons are Shared

O

HH • •

 • • • •

 • • O

HH

 •  • 

O

 •   •  

 •   • O • • • 

 • 

 • •

O

O

Double bonds are stronger than single bonds.

Is intramolecular bonding stronger in water or dioxygen?

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Ionic BondsElectrostatic Attraction

Ca2+

H+Cl – • • •

 •

 • • • •

E = k · q1 · q2

d

Compounds with ionic bonds generally havehigh melting points.

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van der Waal ForcesDipole-Dipole: Hydrogen Bonding

HHO

 • •

 • • • •

 • •

HHO

 • •

 • • • •

 • •

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van der Waal ForcesDipole-Induced Dipole

HHO

 • •

 • • • •

 • •

 •  • 

O

 •   •  

 •   • O • • • 

 • 

 • •

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van der Waal ForcesDispersion Forces

 •  • 

O

 •   •  

 •   • O • • • 

 • 

 • •

 •  • 

O

 •   •  

 •   • O • • • 

 • 

 • •

Molecular compounds generally have low melting points.

Is intermolecular bonding in liquid oxygen strong or weak?

Which bond breaks when liquid oxygen boils?

Intermolecular and Intramolecular Forces

What molecular interactions could occur

and which are the strongest?

Mercury doesn’t “wet”the surface of glass

(silicon dioxide).

Does water “bead up”on a clean or a dirty

windshield?

Why?

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The Chemical "Bond"

Electronegativity differences Various strength of bonds

covalentbonds

ionicbonds

polar covalentbond

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The Chemical "Bond"

Physical properties associated with phase & structure• Surface tension, viscosity, mp, bp, vapor

pressure• The special role of hydrogen bonds

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Predict the Boiling Point

Series 1 Series 2MW BP MW BP16 1832 -112 34 -6076 -88 81 -42123 -52

SiH4

GeH4

SnH4

CH4-161

130 -5

H2SH2SeH2Te

H2O+100

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Electronegative ElementsNitrogen, Oxygen, Fluorine, (Sulfur, Chlorine)

Hydrogen bondsform between molecules

or ions containing veryelectronegative elements,

and hydrogen bound toone of theseelectronegative elements

 • • • •

HHO

 • •  • •

 • • • •

HHO

 • •  • •

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The Effects of Hydrogen Bonding

Melting and boiling points• Liquid water at room temperature

Solubility• ammonia in water

Structure• Ice is less dense than liquid water• Helical structure of DNA

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Measurements

How are things measured?• Distances between cities• Dimensions of a football field• The size of a coin• The distance between atoms

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X-ray Diffraction

X-ray wavelength• 10–10 - 10–11 meters• nanometer (10–9 m), nm• Angstrom (10–10 m), Å

The distance between atoms is in the same range.

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X-ray Diffraction

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X-ray Diffraction

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X-ray Diffraction

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X-ray Diffraction

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X-ray Diffraction

incidentwave

reflectedwave

d n = 2d sin

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