CHEM 132, Chapter 9

• The three states of matter


  • Solid
  • Liquid
  • Gas
• Solid to liquid


  Melting
• Liquid to gas


  Vaporization
• Solid to gas


  Sublimation
• Going from solid to liquid to gas


  Energy is increased and molecules move faster
• Gas to liquid


  Condensation
• Liquid to solid


  Freezing
• Gas to solid


  Deposition
• Moving from gas to liquid to solid


  Energy is decreased, and molecules move slower
• Intramolecular forces


  • Covalent
  • Ionic
  • Metallic
• Intramolecular forces


  Bonds where electrons are shared
• Intermolecular forces


  • Dipole dipole
  • Hydrogen bonding
  • London dispersion
• Intermolecular forces


  Forces between molecules that hold them together
• Dipole dipole


  Attraction between polar molecules
• Dipole dipole forces are only 1% as strong as covalent or ionic bonds
• Hydrogen bonding


  A type of dipole dipole force between H and either F, O, or N
• Hydrogen bonding is very strong
• Hydrogen bonding is due to the polarity, close approach of dipoles, and small size of the hydrogen atom
• London dispersion forces


  Weak and short lived attraction in all atoms and molecules
• Polarizability


  How easily the electron cloud could be distorted to produce a distribution of dipole charges
• The more electrons a particle has, the more polarizable it will be
• Polar molecules


  Have higher boiling points
• Molecules at the surface


  Have less intermolecular activity and aren't as energetically stable
• Higher IMF


  Means higher surface tension
• Adhesion


  IMF with other things
• Cohesion


  IMF with other IMFs, or polar with polar
• Higher adhesion


  Stronger capillary action, which causes the meniscus in graduated cylinders
• Higher IMF


  Means higher viscosity and higher delta Hvap
• Atmospheric pressure decreases


  Boiling point will decrease
• As IMF increases


  Surface tension, viscosity, boiling point, freezing point, heat of vaporization, and enthalpy of fusion all increase, and vapor pressure decreases
• Heat of fusion


  Enthalpy change that occurs at freezing point
• Normal melting point


  When solid and liquid are at equilibrium with total pressure equalling 1 atm
• Normal boiling point


  When vapor pressure of a liquid is exactly 1 atm
• Delta Hvap


  Should be larger than delta Hfus for a given substance
• Supercooled


  Liquids can be
• Superheated


  Liquids can be
• Triple point


  Temperature and pressure when all three phases exist in a closed system
• Critical point


  Temperature and pressure where gas and liquid are no longer different