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Physics Paper 1 · P3 · Lesson 3.8

Energy for changes of state

Use latent heat when energy changes state instead of temperature.

Key ideas1 of 3

Energy can change state

During melting or boiling of a pure substance at constant pressure, energy is transferred in while temperature stays constant. Energy changes the particles’ potential energy.

During a change of state, energy changes particle potential energy while temperature and average kinetic energy stay constant, for a pure substance at constant pressure.

Particles do not simply get hotter during the flat part of a heating graph.

Next: Heating and cooling graphs →
Topic resources and sources

Daily 5 · Exam practice · A4 revision sheet

All P3 content here is shared by Foundation and Higher Tier. Stretch questions combine the core ideas; they are not additional Higher Tier-only content.

AQA Combined Science Trilogy specification · 6.3.2.3. Original notes, questions and diagrams. Particle diagrams are simplified; animation speeds and experimental numbers are illustrative.

Photographs: Melt by Kathy Jantz, CC BY 4.0; Menisco 18mL-2 by Leandro Maranghetti Lourenço, CC BY-SA 3.0 (chosen from the licences offered); Bicycle Pump foot operated by Scott Ehardt (SCEhardt), Public domain, released worldwide by copyright holder. Images displayed without cropping or alteration; a resized source image is used for the ice.