Chapter 12: Liquids, Solids and Interparticle Forces

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Chapter 12 Liquids, Solids and Interparticle
Forces
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What is a liquid? A solid?

• Properties of liquids and solids depend on
  Interparticle (Intermolecular) forces
• - vaporization/condensation/freezing
• - equilibrium vapor pressure/volatility
• - surface tension
• - boiling point/freezing point
• We are going to learn about Interparticle or
  Intermolecular forces first! (Different order
  than in chapter.)

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TYPES OF INTERPARTICLE FORCES - SEE HANDOUT

• All forces of attraction between atoms, ions,
  molecules are Interparticle forces
• Includes ionic bonding, covalent bonding,
  metallic bonding, network covalent bonding, and
  ion-dipole attraction
• Important Subcategory is Intermolecular Forces
• Also called Van Der Waals forces
• Weak to moderate forces of attraction
• Not a type of bonding
• Includes three main ones London Dispersion
  Forces, Dipole-dipole Attraction and Hydrogen
  Bonding Force of Attraction

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Intermolecular Forces

• 1. London dispersion forces (LDF)
• - Small to moderate strength
• - Depend on size of electron cloud (and so also
  molar mass) of atom or molecule
• - Noble gases, diatomic elements, and many other
  nonpolar compounds

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Nonpolar molecules such as H2 can develop
instantaneous dipoles and induced dipoles. The
attractions between such dipoles, even through
they are transitory, create London dispersion
forces. (See figures 12.17 18)
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Table 12.4 Dispersion Force and Molar Mass
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(No Transcript)
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Intermolecular Forces

• 2. Dipole-dipole attraction
• - Moderate strength
• - Molecules that have polar covalent bonds
• - Polar molecules d and d- attraction
• Table of Properties of Hydrohalogens
• H-F H-Cl H-Br H-I
• DEN 1.4 1.1 0.8 0.4
• e-s 10 18 36 54
• BP 291 188 206 238

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There are many dipole-dipole interactions
possible between randomly arranged ClF molecules.
In each interaction, the positive end of one
molecule is attracted to the negative end of a
neighboring ClF molecule.
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Polarity and Dipole-to-Dipole Attraction
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Intermolecular Forces

• 3. Hydrogen-bonding force of attraction
  (enhanced dipole-dipole)
• - Strong force, but much less than real bonding
• - Memory helper
• E.T. FON Home only F-H, O-H and N-H have this
  type of force
• - Due to small radius and high EN
• - See in boiling point data

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Depiction of hydrogen bonding among water
molecules. The dotted lines are the hydrogen
bonds.
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Figures 12.22 24 Intermolecular H-Bonding
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Hydrogen Bonding and Water

• Water - 80 hydrogen-bonded - very tight
  arrangement (also high viscosity high density and
  high specific heat)
• Ice - crystal is very open, less dense than
  liquid
• (4. Dipole - induced dipole between diff types
  of molecules, O2 in H2O)

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Diagrams of hydrogen bonding involving selected
simple molecules. The solid lines represent
covalent bonds the dotted lines represent
hydrogen bonds.
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If there were no hydrogen bonding between water
molecules, the boiling point of water would be
approximately - 80C.
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Notice that molecules with F-H, O-H and N-H have
HIGH BPs because of Hydrogen-bonding forces of
attraction.
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Properties and H-Bonding
Name Form- ula Molar Mass Structure BP, C MP, C Solb in Water
Ethane C2H6 30.0 -88 -172 immisc
Methanol CH3OH 32.0 64.7 -97.8 misc- ble
Table on page 411 in Tro.
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Chemistry at a GlanceIntermolecular Forces
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PRACTICE IDENTIFYING THE TYPE OF IM FORCE

• CH4(g) C6H6(l)
• Br2(l) HBr(l)
• IBr(s) CH3OH(l)

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The Structure of Solids, Liquid and Gases
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Distinguishing Properties of Solids, Liquids, and
Gases
Property Solid Liquid Gas Vol/Shape Def
vol Def vol indef shape Indef vol/shape
def shape Shape of container Shape of
container Density High High, usually lt
Solid Very low Compressibility
Small Small Large Thermal ExpansionVery
small Small Moderate Strength
Strong Moderate Weak of IM Forces Example
Sucrose Water Carbon dioxide
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There are six changes of state possible for
substances learn all 6
Fusion
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BP, FP, Phase Changes, and DHophase

• Phase changes changes of state
• Learn all six
• Phase changes are accompanied by heat flow,
  called Enthalpy of phase change or DHophase
• Heat of vaporization liquid to vapor energy (J)
  to vaporize 1 mol at constant T P DHvap for
  water is 40.7 kJ/mol DHcond -DHvap
• Heat of fusion solid to liquid energy (J) to
  melt 1 mol at constant T P DHvap for water is
  6.02 kJ/mol DHfrz -DHfus

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BP, FP, Phase Changes, and DHophase

• Sensible heat transfer temperature is changed
  but not phase
• q m cp DT
• m is mass, cp is specific heat and DT is Tf Ti
• Latent heat transfer using DHophase phase
  changes but not temperature
• q m DHophase
• m is mass or moles depending on units
• See examples 12.1 and 12.2. Try skill builders.

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BP, FP, Phase Changes, and DHophase

• Specific heat energy required to raise
  temperature of 1.00 gram of substance by 1.00oC
• cp for water is 4.184 J/g.oC
• Find heat required to raise the temperature of
  20.0 g of water from 25.0oC to 35.0oC.
• q 20.0 g (4.184 J/goC)(35.0-25.0)oC
• 837 J

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Practice Calculations for Heating Curves

• Calculate the total heat absorbed when a 15.5
  gram cube of ice melts, warms to the BP of water
  and then vaporizes completely. (DHfus 6.02
  kJ/mol DHvap 40.7 kJ/mol) There will be two
  latent heat transfers and one sensible heat
  transfer.
• Latent 15.5 g (1mol/18.015g)(6.02kJ/mol) 5.18
  kJ
• Sensible 15.5 g (4.184J/goC)(100.0oC)(1kJ/103J)
  6.49 kJ
• Latent 15.5 g (1mol/18.015g)(40.7kJ/mol) 35.0
  kJ
• Total 46.7 kJ

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BP, FP, Phase Changes, and DHophase

• Boiling point temperature at which the vapor
  pressure of a liquid is equal to the external
  pressure above the liquid, usually atmospheric
  pressure of 1 atm (Normal BP is at 1 atm)
• Freezing point temperature at which a liquid
  changes into a solid at 1 atm

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Boiling Point of Water at Various Locations That
Differ in Elevation
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In the evaporation of a liquid in a closed
container (a), the liquid level drops for a time
(b) and then becomes constant (ceases to drop).
At that point a state of equilibrium has been
reached in which the rate of evaporation equals
the rate of condensation (c).
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Equilibrium Vapor Pressure

• In closed system at any given temperature,
• rate of vaporization rate of condensation
• At dynamic equilibrium number of molecules in
  gas phase and number of molecules in liquid phase
  stay the same, but processes still happening
• Vapor pressure taken at equilibrium the partial
  pressure
• Vapor pressure changes with change in temperature
  
• Normal boiling point is when vapor pressure is
  1.00 atm or 760. Torr

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Vapor Pressure of Water at Various Temperatures
Plot vapor pressure curves (pressure vs.
temperature) curved line like Figure 11.26.
Normal boiling point is the temperature at which
vapor pressure atm pressure 760 torr.
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Properties of Liquids

• Just read about surface tension, viscosity and
  capillary action

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Types of Crystalline Solids

• There are two types of solids crystalline and
  amorphous. We are looking at crystalline.
• There are FOUR types of crystalline solids
• Molecular solids made of molecules with covalent
  bonds molecules held in place by IM forces low
  to mod MPs
• Ionic solids made of formulas units of ions
  held in place by ionic bonding high MPs
• Metallic composite units are atoms held in
  place with metallic bonding range of MPs but
  usually higher than molecular solids
• Network covalent atoms held together in network
  covalent bonding only diamond, SiC, SiO2.
• (Atomic solids like noble gases do not occur at
  normal conditions.)