Which of these is an example of a physical change?
A physical change alters a substance's form or state without creating any new substance. Examples include melting ice, boiling or freezing water, dissolving sugar or salt, cutting paper, and crushing a can. Burning, rusting, and cooking are chemical changes because they form new substances.
The answer
A physical change is a change in the form, shape, or physical state of matter in which no new substance is formed and the change is usually reversible. The chemical identity of the material stays the same before and after.
Common exam-correct examples of physical changes:
- Melting ice (solid water → liquid water)
- Boiling, evaporating, or freezing water (state changes)
- Dissolving sugar or salt in water
- Cutting, tearing, or folding paper
- Crushing a can or breaking glass
- Grinding a solid into powder
- Mixing sand and iron filings (no reaction)
In all of these, you still have the same substance—just in a different shape or state.
Why the other options are wrong (chemical changes)
Multiple-choice versions of this question usually hide the correct answer among chemical changes, which do produce new substances with new properties. Rule these out:
- Burning wood, paper, or fuel — combustion produces ash, carbon dioxide, and water vapor; the original material is gone.
- Rusting iron — iron reacts with oxygen and water to form iron oxide, a brand-new compound.
- Cooking or baking (frying an egg, baking a cake) — heat drives chemical reactions that permanently change the food.
- Souring milk or rotting food — bacterial and enzymatic reactions create new substances.
- Digesting food and photosynthesis — both are chemical.
The test: if you can (in principle) get the original substance back by a physical means like cooling, evaporating, or filtering, it is physical. If a new substance with different chemical properties has appeared, it is chemical.
How to tell them apart reliably
Use these signposts. Signs of a chemical change include a color change, gas bubbles or a new odor, formation of a solid precipitate, light or heat released, and irreversibility. A physical change typically involves only a change of state, shape, size, or dissolving, and often just needs energy added or removed to reverse.
Two tricky cases students miss:
- Dissolving salt or sugar in water is physical. No new compound forms—evaporate the water and you recover the original solid. The ions separate but the substance's identity is unchanged.
- Boiling water is physical, not chemical. The bubbles are water vapor (still H₂O), not hydrogen and oxygen gas. Water only breaks into its elements through electrolysis, which is chemical.
So when a question asks "which of these is an example of a physical change?", scan the options and pick the one involving a change of state, shape, or dissolving with no new substance—melting, freezing, boiling, cutting, crushing, or dissolving—and reject anything that burns, rusts, cooks, rots, or reacts.
| Melting ice | Physical | Solid water becomes liquid water; still H₂O, reversible by cooling |
| Dissolving sugar in water | Physical | Sugar disperses but is unchanged; recover it by evaporating water |
| Crushing a can | Physical | Only shape changes; the aluminum is chemically identical |
| Boiling water | Physical | Bubbles are water vapor (H₂O), not new substances |
| Burning wood | Chemical | Combustion forms ash, CO₂, and water vapor—new substances |
| Rusting iron | Chemical | Iron reacts with oxygen to form iron oxide |
| Cooking an egg | Chemical | Heat permanently changes the proteins into new substances |
Frequently asked
What are 10 examples of physical changes?
Melting ice, boiling water, freezing water, dissolving sugar, dissolving salt, cutting paper, crushing a can, breaking glass, grinding a solid into powder, and mixing sand with iron filings are all physical changes—each alters form or state without creating a new substance.
How is a physical change different from a chemical change?
A physical change alters shape, size, or state without forming a new substance and is usually reversible. A chemical change produces one or more new substances with different properties, often signaled by color change, gas, odor, precipitate, or heat, and is typically hard to reverse.
Is dissolving salt a physical or chemical change?
Dissolving salt in water is a physical change. The salt separates into ions but its chemical identity is unchanged, and you can recover the original salt simply by evaporating the water—so no new substance is permanently formed.
Is melting ice a physical change?
Yes. Melting ice is a physical change: solid water turns into liquid water, but it is still H₂O. Only the physical state changes, and the process is reversible by cooling the water back below 0°C.