Ch 12 - Intermolecular Forces Flashcards
intermolecular forces
interactions between particles or molecules that influence physical properties
dispersion forces
every substance
weakest
relies on instantaneous dipole
strength depends on polarizability (ease that electron cloud can be distorted)
increases with molar mass
dipole dipole forces
polar substances
if polar + nonpolar, dipole induced dipole forces
attraction between oppositely charged portions
hydrogen bonding
super strong type of dipole-dipole
polar molecule with NOF directly bonded to H
ion dipole
ion + polar molecule
if ion + nonpolar, ion induced dipole forces
IMF strength ranking
dispersion < dipole dipole < H bonding < ion dipole
IMF must be overcome for
phase changes
boiling point
temperature at which vapor pressure = atm
weaker IMF = lower BP, easier to escape to gas
what if IMF are equal
more SA = more interaction = stronger IMF
vapor pressure
pressure of the gas above heating liquid
weaker IMF = higher vapor pressure
surface tension
downward force on the surface molecules due to attractions to interior molecules
stronger IMF = higher surface tension
viscosity
resistance to flow
stronger IMF = higher viscosity
melting point
solid to liquid
stronger IMF = higher melting point
phase cools/heats
temperature change, KE change
q = n * c * ΔT
phase change
constant temperature, molecules more closer together, PE change
q = n * ΔHvap or fus (can be negative)
