Which of the following statements is NOT correct?

A chemical change happens when substances react to form one or more new substances with a different chemical composition -- bonds break and new bonds form, and the change is generally not easily reversed. A physical change only alters the state, shape, or arrangement of a substance without changing what it chemically is, and it is usually reversible.

Digestion, photosynthesis, and respiration each convert one set of substances into chemically different ones: enzymes break complex food molecules into simpler compounds, sunlight drives the synthesis of glucose and oxygen from carbon dioxide and water, and cells oxidise glucose to release carbon dioxide, water, and energy. Crystallisation, by contrast, is simply the separation of a dissolved solute into an ordered solid as the solvent cools or evaporates; the solute's chemical identity never changes, and dissolving the crystals again reverses the process. So crystallisation is a physical change, not a chemical one.

• Digestion: complex proteins, fats, and carbohydrates break into simpler molecules such as amino acids, fatty acids, and glucose -- new substances form, so this is a chemical change.

• Photosynthesis: carbon dioxide and water combine to produce glucose and oxygen -- new substances form, so this is a chemical change.

• Respiration: glucose reacts with oxygen to yield carbon dioxide, water, and energy -- new substances form, so this is a chemical change.

• Crystallisation: the same solute simply changes from a dissolved state to an ordered solid lattice -- no new substance forms, so this is a physical change, not a chemical one.

Since digestion, photosynthesis, and respiration each involve a genuine chemical change while crystallisation involves no change in chemical composition, crystallisation is the physical-change example among the four processes.