Change of state refers to the conversion of a substance from one physical state (solid, liquid, or gas) to another. Examples include: Melting (Solid to Liquid): Ice melting into water. Boiling/Vaporization (Liquid to Gas): Water boiling to steam. Freezing (Liquid to Solid): Water freezing into ice. Condensation (Gas to Liquid): Steam condensing into water. Sublimation (Solid to Gas): Dry ice turning directly into carbon dioxide gas. Deposition (Gas to Solid): Water vapour directly turning into snow.