What happens when a substance changes state? | 11-14 years

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Use this lesson plan for 11–14 year olds to explore what happens when substances warm, cool, boil or freeze, tackling misconceptions about changes of state.

In this activity, students watch a demonstration and manipulate molecular models to explore what happens when the state of a substance changes. They answer questions to probe their misconceptions and develop a more scientific understanding of the behaviour of atoms and molecules during changes of state.

Students will be able to explain that:

Molecules do not break up and reform when a substance boils and cools.
Particles stay the same size and shape during state changes.
Particles move around and are not static.
Freezing means ‘liquid changing to solid’ and does not rely on cold temperatures.

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