Exam 1, Wed 422

1
Exam 1, Wed 4-22

• Chapter 13 13.10 13.13
• Chapter 14 14.1 14.5 (no spectroscopy on
  test)
• Chapter 16
• 16.1 16.2
• Types of solids (found in 16.3, 16.6)
• 16.10 16.11
• know how to use equation 16.5
• Multiple Choice, No Notes
• Practice Exams Webassign, van Koppens Spring
  06 (coursepages archives Chem 1C/1CL
  Quizzes Exams)

2
Intermolecular Forces

• Attractions between molecules
• If IMF are low relative to KE, substance is a gas
• If comparable to KE, liquid
• If high relative to KE, solid
• Higher IMF higher melting point and boiling
  point

3
Dispersion Forces

• Strength increases with size of molecule
• Ex Which has a higher boiling point
• He or Ar
• CH4 or C10H22

• The default (and weakest) IMF
• Caused by fluctuations in electron distribution
  within molecules

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(No Transcript)
5
Dipole-Dipole Forces

• For molecules with a net dipole moment (polar)
• end of one molecule attracts end of another
• Stronger than dispersion

6
Hydrogen Bonding

• A super dipole-dipole force, strongest IMF
• Only polar molecules with
• HF HO or HN bond

7
Hydrogen Bonding in Action
8
Properties of Liquids (16.2) Surface Tension

• Resistance to an increase in surface area
• Larger IMF, higher surface tension

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Examples of Surface Tension
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Capillary Action

• Water attracted to glass tube
• adhesive forces
• Surface area is minimized by pulling water into
  tube
• cohesive forces

Glass
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Viscosity

• A liquids resistance to flow
• Increases with
• Increasing IMF
• Length of molecular chain (entanglement)
• Ex Which has higher viscosity
• Acetone or Glycerol
• A 8 carbon chain or a 20 carbon chain

12
?Hvap and ?Hfus

• ?Hvap Amount of heat to vaporize 1 mol of liquid
• ?Hfus Amount of heat to melt 1 mol of solid
• Both increase with increasing IMF
• More energy required to break stronger IMF
• Ex Which has the smaller ?Hvap,
• water or acetone?

13
Crystalline Solids Long range order
Molecular Solids Composite units are
molecules low m.p.
Ionic Solids Composite units are cations and
anions high m.p.
Atomic Solids Composite units are atoms variable
m.p.
m.p. melting point
Covalent high m.p.
Nonbonding very low m.p.
Metallic variable m.p.
Examples What type of solid is formed
by H2O Cl2 Ar Cu Cdiamond
For example Webassign wants both atomic and
metallic for Au
14
FYI

• Covalent Bonding sharing electrons
• Ionic Bonding opposite charged ions
• Metallic Bonding sea of electrons