Chemistry: Liquids and Intermolecular Forces

Intermolecular Forces

• Weaker than intramolecular forces.
• Control physical properties such as boiling/melting points, viscosity, and vapor pressure.

States of Matter

• Determined by intermolecular forces and kinetic energy.
• Solid and liquid phases refer to condensed phases due to closer particle proximity.

Types of Intermolecular Forces

• Dispersion Forces (London Forces): Present in all molecules; weakest.
• Dipole-Dipole Forces: Occur between polar molecules.
• Hydrogen Bonds: Strong dipole interactions involving H bonded to N, O, or F.
• Ion-Dipole Interactions: Important in ionic solutions; stronger than hydrogen bonds.

Factors Affecting Intermolecular Forces

• Polarizability: Ability of electron clouds to distort; increases boiling point with greater polarizability.
• Molecular weight: Larger molecules often have stronger dispersion forces.
• Presence of H bonds: Significantly raises boiling points in comparison to similar non-H bond substances.

Physical Properties Affected by Intermolecular Forces

• Viscosity: Resistance to flow; increases with stronger forces.
• Surface Tension: Inward forces at a liquid's surface creating a 'skin'.
• Capillary Action: Rise of liquids in narrow tubes; dependent on cohesive and adhesive forces.

Phase Changes

• Readily categorized into melting/freezing, vaporizing/condensing.
• Heat of Fusion: Energy required to melt a solid.
• Heat of Vaporization: Energy required to convert a liquid to gas.

Phase Diagrams

• Graphs representing states of matter under various temperature and pressure conditions.
• Critical Point: Temperature/pressure beyond which a gas cannot be compressed into a liquid.

Supercritical Fluids

• State beyond critical temperature/pressure where gas and liquid are indistinguishable.