Chapter 12: Intermolecular Forces Flashcards
intramolecular forces
forces within a molecule
intermolecular forces
forces between molecules (minimum of 2)
dipole-dipole interactions
both 1st and 2nd substances are polar (can be the same and different molecules)
ion-dipole interactions
results from attraction between an ion and a polar neutral molecule (or dipole)
induced-dipole interactions
when an ion or a dipole induces a dipole in an atom or a molecule with no dipole
dipole-induced interactions
1st substance is polar, 2nd is not (occurs between a dipole-nonpolar or a dipole-atom)
ion-induced dipole
occurs between an ion and a nonpolar molecule, or an ion and an atom
dispersion forces
also known as van der Waals or London dispersion forces (induced dipole-dipole interactions) weakest of the IMFs
factors that affect dispersion forces
polarizability of the electron clouds and molecular shape
hydrogen bond
polar molecules containing H atoms bonded directly to the most electronegative atoms (F, O, or N)
why do low molar mass compounds have high boiling points?
because of hydrogen bonding, not molar mass
surface tension
increases with the strength of IMF and decreases with rising temperatures, a property related to the tendency of a liquid to seek a shape that yields the minimum surface area
cohesive forces
intermolecular forces between like molecules (eg. forces between H2O and H2O)
adhesive forces
intermolecular forces between unlike molecules (eg. forces between H2O and glass)
concave meniscus
attraction of water to glass is greater than water to water
convex shaped
attraction of mercury to mercury is greater than mercury to glass
viscosity
measure of a fluid’s resistance to flow, increases with intermolecular forces and decreases with temperature
evaporation
surface process (first the molecules on the surface must go to the vapor state and the rest will follow
factors that affect evaporation
surface area, temperature, and strength of IMF (high surface area -> high rate of evaporation -> high vapor pressure)
which would evaporate quicker? a dish or a flask
the dish due to the larger surface area
as temp increases:
more molecules have the minimum KE needed to enter the gas phase (the number of molecules in the gas phase increases, as well as the vapor pressure)
vapor pressure
the pressure exerted by a liquids vapor when the liquid and vapor are in equilibrium
ethylene glycol with the strongest IMFs will have
high boiling point, low rate of vaporization, and low vapor pressure
diethyl ether with the weakest IMFs will have
low boiling point, high rate of vaporization, high vapor pressure
what is the boiling point?
temperature at which a liquids vapor pressure equals atmospheric (external) pressure
boiling point increases as
IMFs increase