AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Changes of state are physical changes which differ from chemical changes…
Full specification wording
Changes of state: Changes of state are physical changes which differ from chemical changes because the material recovers its original properties if the change is reversed.
In a physical change the substance itself is unchanged, since only the arrangement and energy of its particles differ, so reversing the change returns the original material with its original…
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 2 of 2
- 2 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
In a physical change the substance itself is unchanged, since only the arrangement and energy of its particles differ, so reversing the change returns the original material with its original properties. Freeze the water you melted from ice and you get ice again, with the same melting point and the same density; no new substance has been made and no bonds within the molecules have been broken. A chemical change is different, because burning magnesium produces magnesium oxide, a new substance with its own properties, and cooling it does not give the magnesium back. The test to apply in an exam is whether the original properties return on reversal. Since no new substance forms, mass is conserved in a change of state as well.
What earns the marks
- A change of state being a physical change in which no new substance is formed.
- The original properties returning when the change is reversed.
- A chemical change producing a new substance that is not recovered on reversal.
- The particles themselves being unchanged, with only their arrangement and energy differing.
Common mistakes and how to put them right
Calling boiling a chemical change because bubbles are produced.
Saying a physical change is reversible simply because it is easy to undo.
Claiming the molecules are broken apart into atoms when a substance boils.
Offering a chemical change such as rusting as an example of a change of state.
Exam tips
- Justify 'physical' by naming a property that returns, such as the melting point or the density.
- Say explicitly that no new substance is formed, because that phrase carries a mark.
- Keep the particle-level statement separate from the observation, since examiners want both.
Try the lesson
The start of the Changes of state: Changes of state are physical changes which differ from chemical changes because the material recovers its original properties if the change is reversed. lesson, made from checked teaching notes for this specification point.
Have a go first
Ice melts to form water. Which statement describes what happens when this change of state is reversed?
Listen
In a physical change the substance itself is unchanged, since only the arrangement and energy of its particles differ, so reversing the change returns the original material with its original properties. Freeze the water you melted from ice and you get ice again, with the same melting point and the same density; no new substance has been made and no bonds within the molecules have been broken. A chemical change is different, because burning magnesium produces magnesium oxide, a new substance with its own properties, and cooling it does not give the magnesium back. The test to apply in an exam is whether the original properties return on reversal. Since no new substance forms, mass is conserved in a change of state as well. A strong answer earns marks for these points. a change of state being a physical change in which no new substance is formed. the original properties returning when the change is reversed. a chemical change producing a new substance that is not recovered on reversal. the particles themselves being unchanged, with only their arrangement and energy differing. Exam tip: Justify 'physical' by naming a property that returns, such as the melting point or the density.
Key words
Say what each word means before you turn the card.
physical change
Try answering aloud or in your head before turning the card.
chemical change
Try answering aloud or in your head before turning the card.
See every definition
- physical change
- A change in which the substance itself is unchanged, since only the arrangement and energy of its particles differ.
- chemical change
- A change that produces a new substance with its own properties, which is not recovered on reversal.
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Changes of state: Changes of state are physical changes which differ from chemical changes because the material recovers its original properties if the change is reversed.
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge