GCSE Physics (AQA)

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Change of State as a Physical Change

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Particle model of matter Changes of state and the particle model

Change of State as a Physical Change

2:08 Changing State
Spec 4.3.1.2
Previous Sublimation Next Kinetic Energy of Molecules
  • During changes of state, the number of particles of a substance does not change.
  • In a solid, particles are arranged in a close regular structure.
  • In a liquid, particles are in contact but can move past each other.
  • In a gas, particles move randomly and are spread out.
  • During changes of state, bonds become weaker, allowing particles to move and spread out more freely.
  • Only the bonds change during changes of state; particles themselves remain unchanged, and no particles are created or destroyed.
  • Changing state does not affect the mass of an object; the masses of each state are the same as the same particles are involved, just arranged differently.
  • Although mass remains the same, density changes as particles are more spread out.
  • All changes of state are reversible.
  • Ice, water, and vapor are the same substance in different states and can transition between these states (e.g., melting, freezing, boiling, condensing).
  • Changing state is a physical change, which is reversible, unlike chemical changes or reactions.
  • In exams, one should be able to explain why mass doesn't change during changes of state and how a change of state is a physical change.

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