Unit 10: Intermolecular Forces and States of Matter

A SOLID has a _ shape, _ volume, _ compressible, _ flow, and the strength of intermolecular attractions are _

A SOLID has a FIXED shape, FIXED volume, IS_NOT compressible, NO flow, and the strength of intermolecular attractions are VERY_STRONG

A LIQUID has a _ shape, _ volume, _ compressible, _ flow, and the strength of intermolecular attractions are _

A LIQUID has an INDEF shape, FIXED volume, IS_NOT compressible, YES flow, and the strength of intermolecular attractions are MODERATE

A GAS has a _ shape, _ volume, _ compressible, _ flow, and the strength of intermolecular attractions are _

A GAS has a INDEF shape, INDEF volume, IS compressible, YES flow, and the strength of intermolecular attractions are VERY_WEAK

Phase transition

a change of a substance from one state to another

Boiling Point

the temperature at which vapor pressure of a liquid equals the pressure on the liquid

Freezing Point

the temperature at which a pure liquid changes to a crystalline solid

Melting Point

the temperature at which a solid becomes a liquid

Intramolecular Forces

forces that happen within that keep the molecule or compound together [strong, directional, and short range]

Intermolecular Forces

interactions that happen between two or more distinct particles [weaker, less directional and long range]

Ion ion [intermolecular forces]

1/r, strong [250kJ/mol], between ions

Ion dipole interaction [intermolecular forces]

1/r^2, moderate [10-50kJ/mol], between ions and polar solvents

Dipole dipole interaction [intermolecular forces]

1/r^3, weak [3-4kJ/mol], between polar molecules

London Dispersion Force [intermolecular forces]

1/r^6, weak [1-10kJ/mol], between all molecules [strength depends on size, polarizability]

Typical hydrogen bond [intermolecular forces]

about 20kJ/mol, between molecules with F, O, or N

Coulombs Law

Energy of interaction is directly proportional to the charges of the ions (Q1,Q2), and inversely proportional to the distance (d) between them

Attractive force will _ as charge on ion _ and _ as ionic radius _

Attractive force will INCREASE as charge on ion INCREASES and DECREASE as ionic radius INCREASES

Ion Dipole

interaction between an ion and the partial charge of a molecule with a permanent dipole

Sphere of Hydration

cluster of water molecules surrounding an ion as it dissolves in aqueous solution, sphere of solvation if solvent other than H2O

Dipole Dipole Force

forces through which polar molecules attract one another

London Forces

weak attractive forces resulting from instantaneous dipoles due to distortion of e cloud around molecule, all covalent molecules exhibit some London force

3 factors affecting strength of dispersion

polarizability, size of atoms/molecules, shape of molecule

Polarizability

Relative tendency of electron density of an atom or molecule to be distorted by a charged particle

Size of Atoms/Molecules [dispersion forces]

larger atoms/molecules more polarizable than small atoms/molecules, dispersion increases with polarizability

Shape of molecules [dispersion forces]

inceased surface area = increased interactions between molecules, linear molecules have higher dispersion than brached molecules of similar MW

Vapor Pressure

the partial pressure of vapor over the liquid, measured at equilibrium [depends on temperature, depends on intermolecular forces]

Volatile

liquids and solids with relatively high vapor pressures at normal temperatures

As temperature increases, vapor pressure _

increases

Phase Diagrams

a graph to summarize the conditions under which the different states of a substance are stable