Physical Change – IGCSE Chemistry Definition
IGCSE Chemistry definition of physical change: a change that does not produce new substances. Covers examples, comparison with chemical change, and exam identification.
Published by IGCSEChemistry.com.my
Chemistry teaching team: K. S. Tan (15+ years teaching IGCSE Chemistry) and Ms Yash (10+ years teaching IGCSE Chemistry) and Ms Kartini (15+ years teaching IGCSE Chemistry).
Mapped to Cambridge IGCSE Chemistry 0620 (2026–2028). Last updated 2026-08-19.
A physical change is one where no new substances are formed. The 0620 syllabus requires you to distinguish physical changes from chemical changes, and this distinction is tested on Papers 1 and 2. Understanding what makes a change physical is also important when classifying separation techniques and changes of state.
The 0620 definition
A physical change is a change in which no new chemical substances are formed. The change is usually reversible, and the chemical composition of the substance remains the same.
Examples of physical changes
| Change | Why it is physical |
|---|---|
| Melting ice | Water changes from solid to liquid; still H₂O |
| Boiling water | Liquid water to steam; still H₂O |
| Dissolving sugar in water | Sugar molecules separate but are unchanged; can be recovered by evaporation |
| Crushing a solid | Smaller pieces, same substance |
| Bending a metal | Shape changes, same substance |
| Mixing sand and salt | Both substances unchanged; can be separated |
Physical vs chemical change
| Feature | Physical change | Chemical change |
|---|---|---|
| New substances formed? | No | Yes |
| Reversible? | Usually easily reversible | Usually difficult to reverse |
| Energy change | Usually small | Often significant (heat, light) |
| Chemical bonds | Not broken or formed (intermolecular forces may change) | Bonds broken and new bonds formed |
| Examples | Melting, boiling, dissolving, mixing | Combustion, neutralisation, rusting |
Key distinction: changes of state
All changes of state (melting, boiling, freezing, condensation, evaporation) are physical changes. The substance itself does not change — only the arrangement and energy of the particles change. Water as ice, liquid water, and steam are all H₂O.
Signs that a change is chemical (not physical)
If you observe any of these, it is likely a chemical change:
- Colour change (not just mixing colours)
- Gas produced (effervescence)
- Temperature change (significant, not just from mixing)
- Precipitate formed
- Difficult to reverse
Worked exam question
Classify each of the following as a physical or chemical change: (a) dissolving sodium chloride in water (b) burning magnesium in air (c) evaporating sea water to obtain salt (3)
Mark scheme
(a) Physical [1] — NaCl dissolves into Na⁺ and Cl⁻ ions but no new substance is formed; the salt can be recovered by evaporation
(b) Chemical [1] — magnesium reacts with oxygen to form a new substance, magnesium oxide (MgO)
(c) Physical [1] — water evaporates, leaving behind the salt; no new substances are formed
Common exam mistakes
- Saying dissolving is a chemical change. Dissolving an ionic compound like NaCl breaks the lattice into ions but does not create new substances — it is physical. However, dissolving a reactive metal in acid is chemical because new products form.
- Confusing a change of state with a chemical reaction. Boiling water is physical — no new substance is formed.
- Using “reversible” as the only test. Some chemical reactions are reversible too. The key test is whether new substances are formed.
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