Matter's phase (solid, liquid, gas) is determined by the average kinetic energy of molecules (temperature) relative to the strength of intermolecular attractive forces (e.g., polar/hydrogen bonds in water). During a phase transition, added heat (enthalpy) does not raise temperature but instead is converted to intermolecular potential energy as bonds are broken, which is why temperature plateaus at the melting point (heat of fusion) and boiling point (heat of vaporization) on a heat-vs-temperature phase diagram. This concept belongs to thermodynamics/physical chemistry, relating heat (energy transfer, measured in joules), temperature (average kinetic energy), and enthalpy (heat content) to molecular structure and intermolecular forces.
Matter's phase (solid, liquid, gas) is determined by the average kinetic energy of molecules (temperature) relative to the strength of intermolecular attractive forces (e.g., polar/hydrogen bonds in …