Phase Changes and Phase Diagrams (Video Notes)

Vocabulary flashcards covering key phase-change terms, phase diagrams, and related concepts from the video notes.

Phase change

A transition between states of matter (solid, liquid, gas) such as melting, freezing, vaporization, condensation, sublimation, or deposition.

Melting

Solid to liquid phase change caused by an increase in temperature; molecular motion increases and bonds loosen.

Freezing

Liquid to solid phase change when temperature drops below the freezing point; molecules become fixed in a lattice.

Vaporization

Liquid to gas phase change when energy input causes molecules to move apart; includes boiling.

Boiling

Vaporization that occurs throughout a liquid when temperature and pressure conditions cause rapid vapor formation.

Evaporation

Liquid to gas phase change at the surface below the boiling point; energy from surface molecules escapes to the air.

Condensation

Gas to liquid phase change when temperature decreases and molecules come closer; dew point is involved.

Sublimation

Solid to gas phase change skipping the liquid phase, usually under conditions where melting is not favorable.

Deposition

Gas to solid phase change skipping the liquid phase; frost or snow crystals form.

Phase diagram

A graph showing the equilibrium relationships between solid, liquid, and gas phases as a function of temperature and pressure.

Triple point

The unique temperature and pressure where solid, liquid, and gas phases coexist in equilibrium.

Critical point

The end point on a phase diagram where distinct liquid and gas phases no longer exist as separate; beyond this, a supercritical fluid forms.

Supercritical fluid

A state beyond the critical point where liquid and gas properties blend and are indistinguishable.

Intermolecular forces

Attractive forces between molecules (e.g., hydrogen bonding, dipole-dipole, London dispersion) that influence phase behavior.

Endothermic phase changes

Phase changes that absorb energy from the surroundings (melting, vaporization, sublimation).

Exothermic phase changes

Phase changes that release energy to the surroundings (freezing, condensation, deposition).

Dew point

The temperature at which air must be cooled for condensation to begin.

Phase changes in heating vs cooling

Examines how heating drives melting and vaporization, while cooling drives freezing, condensation, and deposition.