Cambridge O Level Chemistry · Syllabus 5070 · Chemical Reactions
Chemical Change
What is Chemical Change?
A change in which one or more new chemical substances are formed. Bonds within the reactants are broken and new bonds are made, so the atoms are regrouped into products with different formulae and different properties from the starting materials.
This definition is part of the Chemical Reactions chapter in Cambridge O Level Chemistry.
Questions students ask about Chemical 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.
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