Key concepts
Temperature tracks average particle kinetic energy. During melting or boiling, added energy mainly changes particle separation and potential energy, so temperature can remain nearly constant.
Melting and freezing occur at the same equilibrium temperature. Vaporization and condensation are opposite processes. Sublimation changes solid directly to gas.
Applications and misconceptions
Pressure cookers raise boiling temperature; evaporative cooling removes high-energy molecules; refrigeration uses repeated vaporization and condensation; freeze-drying uses sublimation.
Misconception: boiling does not mean temperature must keep rising. At the boiling plateau, energy separates molecules instead. Bubbles form throughout the liquid when vapor pressure matches external pressure.