GCSE Combined Science (AQA)

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Heating Graphs

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Particle model of matter Internal energy and energy transfers

Heating Graphs

2:20 Heating to Change State
Spec 4.3.2.3
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  • Heat supplied to an object at a constant rate causes its temperature to rise gradually.
  • A graph can represent how temperature changes over time.
  • Initially, temperature rises at a constant rate due to constant heat supply.
  • The gradient of the graph is determined by specific heat capacity.
  • At the melting point, temperature remains constant during the change of state despite constant heat supply.
  • The graph shows a horizontal section at the melting point due to no temperature change.
  • Energy is used for changing the state, not increasing kinetic energy or temperature.
  • Temperature rises at a different rate once the object becomes a liquid, with a new specific heat capacity.
  • Temperature stops increasing again at the boiling point, indicating another change of state.
  • The graph is horizontal at the boiling point as energy is used for the state change.
  • Different lengths of horizontal sections indicate different latent heats.
  • Temperature rises again once the object becomes a gas, with another new specific heat capacity.
  • The graph can continue indefinitely for gases.
  • The graph is specific to water, but other substances have similar shapes with different gradients and boiling/melting points.
  • Understanding and explaining such graphs may be required in exams.

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