Chapter 11 - Liquids & Intermolecular Forces

Gen Chem II (Lecture)

dispersion forces

• in all molecules (mostly nonpolar)

• a nonpolar particle can be temporarily polarized to allow a dispersion force to form

polarizability

the ease with which the charge distribution is distorted

dispersion force increases with:

• number of electrons

• size of atom or molecule

• linear / less compact molecule shape

• polarizability

dipole-dipole interactions

permanent dipole moment in polar molecules

hydrogen bonding

dipole-dipole interaction when H bonds with N, O, or F

ion-dipole interactions

exist between an ion and a polar molecule

viscosity

resistance of a liquid to flow

stronger intermolecular forces = _______ viscosity

higher

higher temperature = _______ viscosity

lower

surface tension

the energy required to increase the surface area of a liquid

stronger intermolecular forces = _______ surface tension

higher

heat of fusion

energy required to change a solid at its melting point to a liquid

heat of vaporization

energy required to change a liquid at its boiling point to a gas

heat of sublimation

energy required to change a solid directly to a gas (heat of fusion + heat of vaporization)

critical temperature

the temperature beyond which a gas cannot be compressed (liquified)

critical pressure

the pressure needed to liquify a gat at critical temperature

supercritical fluid

the state beyond the critical temperature and pressure where liquid and gas are indistinguishable

greater intermolecular forces = ________ critical temperature

higher

vapor pressure

pressure exerted by the vapor at any temperature when it’s at dynamic equilibrium

higher intermolecular forces = ________ vapor pressure

lower

higher temperature = ________ vapor pressure

higher

volatile liquid

evaporate readily due to high vapor pressure

boiling point

temperature at which a liquid’s vapor pressure equals atmospheric pressure

normal boiling point

temperature at which a liquid’s vapor pressure is 1 atm

Clausius-Clapeyron Equation

ln (P₂ / P₁) = (- ΔH_vap / R(=8.314 J/molK)) ((1 / T₁) - (1 / T₂))

triple point

when all three phases are in equilibrium