Chemistry Chapter 12

dispersion force

temporary polarity in the molecules due to unequal electron distribution

also called london force

electrons happen to be together at the same time (instantaneous dipole)

weakest attraction

dipole-dipole

the attractive and repulsive forces for molecules with a permanent dipole

the positive end of a polar molecule is attracted to the negative end of its neighbor, giving rise to the force

boiling point is higher than nonpolar compounds

immiscible liquids

why oil and water don’t mix

pentane is nonpolar molecule, water is a polar molecule

attractive forces among water molecules are much stronger than their attractions for the pentane molecules

hydrogen bonding

special case of dipole-dipole forces

only occur when hydrogen is bonded with N, O, or F

ion-dipole force

occurs when an ionic compound is mixed with a polar compound

strength of attraction is one of the main factors that determines the solubility of ionic compounds in water

surface tension

property of liquids that results from the tendency of liquids to minimize their surface area

stronger attractive forces = makes it greater

result of liquid experiencing fewer intermolecular forces than liquid molecules in the bulk liquid

factors affecting surface tension

the stronger the intermolecular attractive forces, the higher it will be

raising the temperature reduces it

viscosity

measure of a liquid’s resistance to flow

measures in a unit called poise (P)

factors affecting viscosity

stronger attractions = highers it

heating= lowers it

more spherical= lower it will be

capillary action

ability of a liquid to flow up a thin tube against the influence of gravity

the narrower the tube, the higher the liquid rises

result of two forces working in conjunction, cohesive and adhesive

cohesive forces

liquid-liquid interactions

adhesive forces

liquid-solid interactions

vaporization

process where molecules at the surface of a liquid gain enough energy to overcome attractive forces

the larger the surface area, the faster the rate of evaporation

condensation

process where a gas changes into a liquid

effect of intermolecular forces on evaporation

strong intermolecular forces= makes it slower

weak intermolecular forces= makes it faster

effect of intermolecular forces on condensation

strong intermolecular forces= makes it easier

weak intermolecular forces= makes it harder

normal boiling point

liquid is the temperature at which the vapor pressure of the liquid is equal to 1 atm

the lower the external pressure= makes it lower

sublimation

phase change from solid to gas directly without passing through the liquid phase

fusion

phase change from a solid to liquid

also requires heat absorption (endothermic)

phase changes

describe the different states and changes that occur at various temperature/pressure conditions

triple point

on phase diagram where the temperature-pressure condition where all 3 states coexist