A physical change is a change that affects the form or physical properties of a substance without altering its chemical composition. This means the substance itself remains the same at the molecular level, even though its appearance, shape, size, or state may change
. Key characteristics of a physical change:
- The chemical identity of the substance does not change.
- Physical properties such as shape, size, color, volume, density, and state (solid, liquid, gas) may change.
- Physical changes can be reversible (e.g., melting ice can be refrozen) or irreversible (e.g., cutting wood into sawdust)
- Examples include melting, freezing, boiling, condensing, dissolving, cutting, and grinding
Examples:
- Melting ice into water (solid to liquid) without changing the chemical structure of H₂O
- Dissolving salt in water, where salt can be recovered by evaporation
- Cutting a piece of wood into a baseball bat; the wood remains chemically the same
Physical changes do not produce new substances, unlike chemical changes where new substances with different compositions are formed
. In summary, a physical change alters the appearance or state of matter but does not change the substance's chemical identity
