GCSE Physics (AQA)

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Heating & Change of State

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Particle model of matter Internal energy and energy transfers

Heating & Change of State

6:54 Heating to Change State
Spec 4.3.2.1 4.3.2.3
Previous Specific Heat Capacity of Water Next Specific Latent Heat
  • Heating a substance changes its state between solid, liquid, and gas.
  • Water boils at 100 degrees Celsius, turning from liquid to gas.
  • During a change of state, heating does not affect the temperature.
  • Kinetic energy of molecules remains unchanged during a state change.
  • Energy supplied during heating weakens or breaks intermolecular bonds.
  • Bonds reform when thermal energy is removed, indicating a physical process.
  • Matter exists in three states: solid (strong bonds), liquid (weaker bonds), gas (few/no bonds).
  • State changes involve breaking or forming bonds: melting (solid to liquid), boiling (liquid to gas), condensation (gas to liquid), freezing (liquid to solid).
  • Sublimation (solid to gas) and evaporation (liquid to gas without heat) are other state changes.
  • Evaporation occurs by absorbing heat from surroundings, without reaching boiling point.
  • Evaporation is a slow process as only a few bonds break at a time.
  • In exams, understanding that liquids absorb heat from surroundings to change state is essential.
  • Sweat cools the body by absorbing heat for evaporation, reducing body temperature faster than surrounding air.

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