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Particle Model

Changes of state and internal energy

  • 3 things to know
  • Paper 2

Overview

Freezing, condensing, sublimation, evaporating and boiling, mass conserved in changes of state as physical changes, heating raising the kinetic store of particles or changing state, and why temperature stays constant while a substance melts or boils.

What you need to know

Answer each one before you reveal it.

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Key term

Describe one difference between evaporating and boiling.

Key term

Give one way in which a change of state differs from many chemical changes.

Key term

Water boils away in an open pan and the pan and its contents weigh less afterwards. Explain why mass has still been conserved.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Name the change of state in which a liquid becomes a solid.

    Model answer

    Freezing.

  2. 2

    Name the change of state in which a gas becomes a liquid.

    Model answer

    Condensing.

  3. 3

    Name the change of state in which a solid turns directly into a gas.

    Model answer

    Sublimation.

  4. 4

    Describe one difference between evaporating and boiling.

    Model answer

    Evaporation happens only at the liquid surface and at any temperature, while boiling happens throughout the liquid at its boiling point.

  5. 5

    State what happens to the total mass of a substance when it melts.

    Model answer

    It stays the same, because mass is conserved during a change of state.

  6. 6

    Explain why melting is classed as a physical change rather than a chemical one.

    Model answer

    No new substance is formed, and freezing the liquid again returns the original solid with its original properties.

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