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, ISNOT compressible, NO flow, and the strength of intermolecular attractions are VERYSTRONG

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

Coulomb’s 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