Intermolecular Forces and Phases of matter

1
Intermolecular Forces and Phases of matter

• Physical states depends on temperature and
  pressure
• Examples
• Water freezes at 0oC and 1 atm pressure
• Water boils at 100oC and 1 atm
• Water boils at 70oC at 0.25 atm
• Oxygen gas can be liquefied at room temperature
  and extremely high pressures
• Liquid propane is stored under high pressures.
  When the pressure is lowered, it coverts to the
  gas phase

2
Liquids, solids, and attractions between molecules

• On an atomic level, how do we distinguish between
  gases, solids, and liquids?
• Why do liquids and solids exist? Why do the
  particles stick together? Why is all matter not
  in the gaseous state?
• Intermolecular forces

3
Intermolecular Forces

• Three basic types
• London dispersion forces
• Dipole-dipole forces
• Hydrogen bonding

4
London Dispersion Forces

• London dispersion forces are present between all
  molecules
• Temporary particle charges give temporary
  polarity
• Weak electron attractions that occur when e-
  change sides of the molecule
• Gives the overall molecule a charge