Intermolecular Forces - AP Chemistry Unit 3

Intramolecular Forces

Forces within a molecule, such as covalent bonds.

Intermolecular Forces (IMFs)

Forces between molecules, which are much weaker than intramolecular forces.

Polarizability

The ability of a molecule to form instantaneous temporary dipoles; larger electron clouds lead to higher polarizability.

London Dispersion Forces (LDFs)

The weakest type of IMF that exists between all molecules with electrons, more notable in non-polar covalent molecules.

Dipole-Dipole Forces

Forces that exist between polar molecules due to an uneven distribution of charge.

Hydrogen Bonding

A stronger type of dipole-dipole attraction that occurs when hydrogen is bonded to nitrogen, oxygen, or fluorine.

Ion-Dipole Forces

Forces that occur when ions are attracted to the oppositely charged dipoles of a polar molecule.

Molecular Solids

Solids formed from molecules, held together by IMFs, with low melting points and not electrically conductive.

Covalent Network Solids

Solids formed from atoms held together by covalent bonds, having the highest melting points.

Ionic Solids

Solids formed from cations and anions held together by lattice energy, which are soluble in water.

Metallic Solids

Solids formed from metals, held together by a sea of electrons, and always electrically conductive.

Viscosity

The resistance to flow in liquids; related to the ease with which individual molecules can flow.

Surface Tension

A measurement of inward forces that must be overcome to break the surface of a liquid.

Capillary Action

The tendency of liquids to climb narrow tubes driven by adhesion and cohesion.

Meniscus

The curvature that exists at the surface of a liquid due to surface tension.

Vapor Pressure

The pressure that develops in the gas phase when a liquid is placed in a closed container.

Volatility

The ability of a substance to turn into a gas; related to vapor pressure.

Homogeneous Mixture

A mixture in which one substance is dissolved in another, such as seawater.

Dilution Equation

M1V1 = M2V2; used for calculating concentrations when mixing solutions.

Beer's Law

A = abc; describes the relationship between absorbance and concentration in solutions.

Distillation

The process of separating substances based on differences in boiling points.

Filtration

The process of separating solids from liquids using a porous membrane.

Chromatography

A technique for separating components of a mixture based on their relative polarities.

Ideal Gas Law

The equation PV = nRT that relates pressure, volume, temperature, and amount of gas.

Boyle’s Law

P1V1 = P2V2; describes the relationship between pressure and volume.

Charles’ Law

V1/T1 = V2/T2; describes the relationship between volume and temperature.

Gay-Lussac’s Law

P1/T1 = P2/T2; describes the relationship between pressure and temperature.

Dalton’s Law of Partial Pressures

States that the total pressure is equal to the sum of the partial pressures of individual gases.

Graham’s Law of Diffusion

States that heavier gases diffuse slower than lighter gases.

Kinetic Molecular Theory

A model that explains the behavior of ideal gases and their properties.

Maxwell-Boltzmann Diagrams

Probability distributions that describe the speed or energy of gas particles.

Triple Point

The condition at which solid, liquid, and gas phases exist in equilibrium.

Aqueous Solution

A solution in which water is the solvent.

Molarity (M)

A measure of concentration calculated as moles of solute divided by liters of solution.

Factors Affecting Vapor Pressure

Including IMFs, temperature, and molar mass; increased temperature usually increases vapor pressure.

IMFs and Physical Properties

As IMFs increase, molecules stick together more, affecting boiling points and melting points.

Allotropes

Different forms of an element in the same physical state, such as graphite and diamond.

Kinetic Energy and Temperature

As temperature increases, so does the kinetic energy of particles.

Pressure and Volume Relationship

The presence of extra gases does not change the volume of a rigid container.

Real vs. Ideal Gases

Real gases have volume and intermolecular forces; ideal gases do not.