GCSE Combined Science (AQA)

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Freezing & Melting

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Particle model of matter Changes of state and the particle model

Freezing & Melting

3:00 Changing State
Spec 4.3.1.2
Previous Density of States of Matter Next Boiling, Evaporating & Condensing
  • Freezing is the process of a substance changing from a liquid state to a solid state.
  • Example: Freezing water in an ice tray.
  • Melting is the opposite process, where a substance changes from a solid state to a liquid state.
  • Example: An ice lolly melting in the sun.
  • You should be able to recognize and describe freezing and melting, especially with water.
  • Substances melt when heated and gain thermal energy.
  • Ice and water are the same substance in different states; ice melts when heat is supplied.
  • Substances freeze when cooled and lose thermal energy.
  • Freezing and melting are caused by changes in thermal energy.
  • The melting point is the temperature at which a substance will melt when heated.
  • The melting point of water is 0 degrees Celsius, which helps define the Celsius scale.
  • A change of state occurs when temperature crosses the melting point.
  • Different substances have different melting points.
  • Example: Oil's melting point is approximately -20 degrees C; steel's is approximately 1,510 degrees C.
  • Oil is a liquid at room temperature, while steel is a solid due to their melting points.
  • You need to know the melting point of water for exams, but not other substances' melting points unless given.

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