Year 9 · Science
Changes of state: particle model in Year 9 Science
Start here
Focus on particle model of changes of state. Start with “Investigate The Movement of Particles in Changes of State”, then explain the idea in your own words.
Understand the key idea
A change of state is a physical change: the particles themselves stay the same and only their arrangement, spacing and energy change. Energy supplied during melting and boiling breaks forces of attraction between particles rather than raising the temperature, which is why the temperature stays flat during a change of state.
Common mix-up
A flat section on a heating graph does not mean no energy is being supplied. The energy is going into overcoming forces between particles, not into raising the temperature.
Try this first
- Label melting, boiling and the two flat sections on a heating curve.
- Explain why temperature does not rise while ice is melting.
- Compare evaporation and boiling in terms of where the change happens.
Ask: While ice is melting, where is the heat energy actually going?
Year 9 learners practise particle model of changes of state.
The activities include Investigate The Movement of Particles in Changes of State, Understand Changes of State, Understand Exothermic and Endothermic Processes in Changes of State, and related practice. The checked support below includes video, worksheet, teaching, lesson. Open a resource in its provider's website and choose the format that best helps the learner explain the idea independently.
Activities covered
- Investigate The Movement of Particles in Changes of State
- Understand Changes of State
- Understand Exothermic and Endothermic Processes in Changes of State
- Understand How Changes in Temperature Cause Changes of State
- Understand The Movement of Particles in Changes of State
- Understand The Role of Energy in Changes of State
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Watch it explained
a teacher walks through it
Changes of state: energy and evaporation
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Learn it properly
lessons and teaching pages
Solid, liquid, gas states and changes of state: lesson sequence
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Solids, liquids and gases - KS3 Physics
Best for: pencil-and-paper practice away from the screen
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