Cambridge O Level Chemistry · Syllabus 5070 · Chemical Reactions
Physical Change
What is Physical Change?
A change in which no new chemical substance is formed. The particles are rearranged in space or given more energy, but each particle keeps its own chemical identity and formula, so melting, boiling, dissolving and changing shape are all physical changes.
This definition is part of the Chemical Reactions chapter in Cambridge O Level Chemistry.
Common mistakes with Physical Change
- 1. “It is a physical change because you can reverse it.” Why temptingMost physical changes are easy to reverse, so the correlation is real. RepairReversibility is a correlation, not a definition. Heating hydrated copper(II) sulfate is chemical and reverses in seconds; cutting paper is physical and cannot be undone. Ask instead whether a new substance has formed. TransferClassify “anhydrous cobalt(II) chloride turning pink in damp air” and justify it. Chemical: a different compound, the hydrate, has formed.
Questions students ask about Physical Change
How do you tell a physical change from a chemical change?
Ask whether a new substance has formed. If yes, it is a chemical change; if no, it is only physical. Reversibility is not the test — heating hydrated copper(II) sulfate is chemical and reverses in seconds, while cutting paper is physical and cannot be undone.
Reviewed by Academiq Edu Instructor PanelLast reviewed Syllabus 2026-2028