Section 3: Physical Properties of Drug Molecules & States of Matter

Polarity Definition

The unequal distribution of electron density within a chemical bond or an entire molecule.

Polarity Metric

Quantified physically as a molecule's dipole moment.

Polarity Structural Requirements

Requires both a net electronegativity difference and an asymmetric molecular geometry.

Polar Molecule Examples

Asymmetric structures possessing a nonzero net dipole moment, such as HCl, H2O, and NH3.

Nonpolar Molecule Examples

Highly symmetric structures whose individual dipole vectors cancel out to equal a zero dipole moment, such as CO2 and CCl4.

IMFA Strength Rule

Stronger intermolecular forces lead to significantly higher boiling points, melting points, viscosity, and surface tension.

Additive Property Definition

A physical property derived strictly from the sum of individual atomic properties or functional groups present, depending directly on the amount.

Additive Property Examples

Mass, molecular weight, and gas volume.

Constitutive Property Definition

A physical property dictated entirely by the structural layout or geometric arrangement of atoms within the molecule.

Constitutive Property Examples

Optical activity, viscosity, and surface tension.

Optical Activity Configurations

Structural property where light rotates clockwise (Dextro) or counterclockwise (Levo).

Colligative Property Definition

A physical property dependent solely upon the total number of non-volatile solute particles dissolved in solution, regardless of their nature.

Colligative Property Examples

Vapor pressure lowering (↓ VP), boiling point elevation (↑ BP), freezing point depression (↓ FP), and osmotic pressure.

Combined Additive-Constitutive Property

Molar refraction stands as a major combined liquid property.

States of Matter Transitions (Solid-Liquid)

Melting absorbs heat energy; freezing releases heat energy.

States of Matter Transitions (Liquid-Gas)

Vaporization absorbs heat energy; condensation releases heat energy.

States of Matter Transitions (Solid-Gas)

Sublimation absorbs heat energy; deposition releases heat energy.

States of Matter Transitions (Gas-Plasma)

Ionization absorbs heat energy; recombination releases heat energy.

Enthalpy Trend in Matter States

Enthalpy of the system increases consistently as matter moves from Solid to Liquid to Gas to Plasma.

Latent Heat / Molar Heat Definition

The absolute heat energy necessary for 1 mole of a gas, solid, or liquid to change phase completely without changing temperature.

Molar Heat of Fusion (ΔHf)

The heat energy absorbed to convert 1 mole of solid to liquid, or released to convert 1 mole of liquid to solid.

Molar Heat of Vaporization (ΔHv)

The heat energy absorbed to convert 1 mole of liquid to gas, or released to convert 1 mole of gas to liquid.

Molar Heat of Sublimation (ΔHs)

The heat energy absorbed to convert 1 mole of solid to gas, or released to convert 1 mole of gas to solid.

Solid Phase Microscopic Properties

Molecules are packed tightly in an orderly layout, showing a definite shape, definite volume, negligible compressibility, and negligible expansibility.

Liquid Phase Microscopic Properties

Molecules are close together but randomly arranged, taking the shape of their container with a definite volume, slight compressibility, and slight expansibility.

Gaseous Phase Microscopic Properties

Molecules are separated by massive distances and move freely, showing no definite shape, no definite volume, high compressibility, and high expansibility.

Fluid Flow Properties across States

Solids are rigid and do not flow; liquids flow; gases flow very easily.