Physics I / States of matter and phase behaviour
Practice question · Put in order

Order the heating of a pure substance from solid to gas at constant pressure.

Hints
  1. Temperature rises within a phase and pauses during a transition.
  2. The substance must melt before it can boil.
Show the answer
  1. Solid is heated; temperature rises until melting point
  2. Melting: temperature constant while solid converts to liquid (ΔH\Delta H_fus absorbed)
  3. Liquid is heated; temperature rises until boiling point
  4. Vaporisation: temperature constant while liquid converts to gas (ΔH\Delta H_vap absorbed)
Why

The flat sections in a heating curve correspond to phase transitions at constant T; energy goes into breaking intermolecular forces.

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