Ch 11: Intermolecular forces and liquids and solids

Gen Chem II

physical properties

depend on physical state

what do covalent bonds determine

molecular shape

bond energies

chemical properties

intermolecular forces

influence physical properties of liquids and solids

state of a substance

depends on the balance between the kinetic energy of the individual particles (molecules or atoms) and the intermolecular forcesk

inetic energy

keeps molecules apart and moving around and is a function of the temp of the substance

IMF

draw particels together

Order of weak to strong IMF

gas, liquid, solid

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 and liquid

intermolecular forces

attractiveforces between moleculesintr

amolecular forces

hold atoms togehter in a molecule, stronger

when a substance is melted or boiled, what is broken

IMF, not covalent bonds

dipole - deipole forces

attractive forces between polar molecules

needs dipole moment

ion-dipole forces

attractive forces between an ion and a polar molecule

dispersion forces

nonpolar molecules and polar molecules. attractive forces that arise as a result of temporary dipoles induced in atoms or molecules

polarizability

ease with which the electron distribution in the atom or molecule can be distorted

polarizablity increases with:

greater nubmer of electrons

more diffuse electron cloudd

dispersion forces increase with

molar mass

hydrogen bond

special dipole-dipole interaction between hydrogen atom in a polar N,O,F bond. s

which has stronger dispersion? long or bunched

long, more surface area for interactions

surface tension

the amount of energy required to stretch or increase the surface of a liquid by a unit area

high surface tension is caused by

strong IMF

capillary action

rising of a liquid through a narrow space against the pull of gravity

cohesion

the Intermolecular attraction between like molecules

adhesion

attraction between unlike molecules

water

roudned downward - adhesion greater than cohesion

mercury

rounded upward - cohesion is greater than adhesion

vsicosity

measure of a fluids resistance to flow

was causes high viscosity

strong IMF

is ice more or less dense than water

less dense. it forms 90 degree angles which create more space

equilibrium vapor pressure

vapor pressure measured when a dynamic equilibrium exists between condensation and evaporation

molar heat of vaporization

energy required to vaporize 1 mole of a liquid

vapor pressure increases with

temperature

stronger IMF?

higher heat of vaporization, lower vapor pressure

boiling point

temperature at which the equilibrium vapor pressure ofa liquid is equal to the external pressuren

normal boiling point

temperature at which a liquid boils when the external pressure is 1 atm

critical temperature

the temperature above which the gas cannot be made to liquefy, no matter how great the applied pressure

critical pressure

the minimum pressure that must be applied to bring about liquefaction at the critical temperature

molar heat of fusion

energy required to melt 1 mole of a solid substance

GO OVER HEATING CURVE

molar heat of sublimation

energy required to sublmine 1 mole of a solid

molar heat of sublimation equation

ΔHsub = ΔHfus + ΔHvap (Hess’ law)

phase diagram

plot of pressure vs temperature summarizing all equilibria betwen phases

vapor pressure curve

as pressure increases, temperature increases

meltin point curve

as pressure increases, the solid phase is favored if the solid is more dense than the liquid