GEN CHEMISTRY

• Gas


  • Assumes the volume and shape of its container
  • Low density
  • Very compressible
  • Very free motion
• Liquid


  • Definite volume but assumes the shape of its container
  • High density
  • Slightly compressible
  • Slide past one another freely
• Solid


  • Definite volume and shape
  • High density
  • Virtually incompressible
  • Vibrate about fixed particles
• Phase


  Homogenous part of the system in contact with other parts of the system but separated from them by a well-defined boundary
• 2 Phases


  • Solid phase - ice
  • Liquid phase - water
• Phase changes


  • Sublimation (solid to gas)
  • Melting (solid to liquid)
  • Vaporization (liquid to gas)
  • Freezing (liquid to solid)
  • Condensation (gas to liquid)
  • Deposition (gas to solid)
• Intermolecular forces


  Attractive forces between molecules
• Intramolecular forces


  Forces that hold atoms together in a molecule
• 930kJ is required to break all OH bonds in 1 mole of water (Intramolecular)
• kJ is required to vaporize 1 mole of water (Intermolecular)
• Intermolecular forces


  • Weaker than intramolecular forces
  • Determine the physical properties of molecules like their boiling point, melting point, density and enthalpies of fusion and vaporization
• Intramolecular forces


  Bonds within a molecule
• Intermolecular forces


  Forces between molecules, generally less strong than ionic or covalent bonds
• Types of intermolecular forces


  • Ion-dipole forces
  • Hydrogen bonding
  • Dipole-dipole forces
  • Dispersion forces
• Ion-dipole forces


  Attractive forces between an ion and a polar molecule
• Hydrogen bonding


  Special dipole-dipole interaction between the hydrogen atom in a polar N-H, O-H, or F-H bond and an electronegative O, N, or F atom
• Hydrogen bonding with water


  Can form hydrogen bonds with water in 2 different ways
• Dipole-dipole forces


  Attractive forces between polar molecules
• Dispersion forces


  Attractive forces that arise as a result of temporary dipoles induced in atoms or molecules
• Polarizability


  Ease with which the electron distribution in an atom or molecule can be distorted
• Polarizability


  Increases with greater number of electrons and more diffuse electron cloud
• Dispersion forces


  Usually increase with greater mass
• Polar molecule


  Experiences dipole-dipole forces
• Non-polar molecule


  Experiences dispersion forces
• Cohesion


  Intermolecular attraction between like molecules
• Adhesion


  Attraction between unlike molecules
• Surface tension


  Amount of energy required to stretch or increase the surface of a liquid by a unit area
• Viscosity


  Measure of a fluid's resistance to flow
• Equilibrium vapor pressure


  Vapor pressure measured when a dynamic equilibrium exists between condensation and evaporation
• Heat of vaporization


  Energy required to vaporize 1 mole of a liquid at its boiling point
• Clausius-Clapeyron equation


  Relates vapor pressure to temperature
• Volatility


  Tendency of a substance to vaporize
• Diethyl ether


  • Volatile, highly flammable organic liquid used mainly as a solvent
• Boiling point


  Temperature at which the equilibrium vapor pressure of a liquid is equal to the external pressure
• Critical temperature


  Temperature above which a gas cannot be liquefied, no matter how great the applied pressure
• Critical pressure


  Minimum pressure that must be applied to bring about liquefaction at the critical temperature
• Phase diagram


  Summarizes the conditions at which a substance exists as a solid, liquid, or gas
• Liquid


  • Has a definite volume but assumes the shape of its container
• Solid


  • Has a definite volume and shape
• cell


  • Simple cubic-tabm/unit cell (8×1/8=1)
  • Body centered cubic- 2 atoms/unit cell
  • Face centered cubic-4 atoms/unit cell