ap chem - unit 3; intermolecular forces and properties

intermolecular forces (IMF)

attractive forces between molecules

ion-ion force

attraction between oppositely charged ions

dipole-induced dipole

the non-polar molecule interacts with the polar molecule and the non-polar one becomes slightly polar (temporarily)

ion-dipole force

attraction between an ion and a polar molecule (oppositely charged parts)

dipole-dipole

attraction between a polar molecule and a polar molecule, strength of the reaction depends on the magnitude of the dipole

hydrogen bonding

a type of dipole-dipole; only occurs with an H and an N, O or F.

londen dispersion forces

between non-polar and some other molecule (only occurs although it is non polar because it of the random electron movement). (induced-dipole induced-dipole)

strongest to weakest IMF

1 being strongest, 5 being weakest


1. ion-ion
2. ion-dipole
3. hydrogen bonding
4. dipole-dipole
5. londen dispersion

big molecule

highly polarizable

small molecule

highly nonpolarizable

ionic solids

ionic bonds; strong ionic forces - brittle, high melting point, contuctswhen dissolved into a liquid

covalent network solids

connected and layered network (diamond v. graphite); rigid and hard, do not conduct electricity

molecular solids

H-bonds; e.g. ice; weaker IMFs, lower melting points

metallic solids

sea of electrons, meaning it is a good conductor, malleable, ductible

crystalline solid

nice grid

amorphus solid

not so nice grid

solid → liquid → gas

phase change

solid → liquid; weakens IMFs

liquid → gas breaks IMFs

assumptions we make about the kinetic molecular theory

* gas moves in random directions of relatively large distances
* collisions are perfectly elastic (no energy lost)
* gasses move in straight lines intil they collide w/ the container
* average KE in a sample of gas is proportional to the temperatures; KE = 1/2\*m\*v^2

gasses deviate from ideal conditions the most when

there is high pressure, and low temperatures

distillation

seperates mixtures by taking advantage of boiling points and differences in vapor pressures

paper chromatography

seperates mixtures by taking of polarity and nonpolarity

E (energy) =

h\*v

energy =planck’s constant \* frequency

c (speed of light) =

3\.00x10^8 m/s

wavelength \* frequency

A (absorbance) =

a \* b \* c

a = molar absorpivity

b = path length

c = concentation

…however, in a lab, you can ignore that a and the b, as those will stay constant

vapor pressure

when a liquid is introduced into a closed container, it establishes a dynamic equilibrium with its vapor. the pressure of the vapor at equilibrium is referred to as the vapor pressure of the liquid.