Which type of change alters the physical form but not the chemical composition of a substance?

A physical change is characterized by a transformation that modifies the form of a substance without affecting its chemical composition. This type of change can include processes such as melting, freezing, dissolving, or breaking. For instance, when ice melts into water, the chemical composition of H2O remains the same; only its physical state changes from solid to liquid.

It is important to differentiate physical changes from other types. In a chemical change, the substance undergoes a transformation that results in the formation of one or more new substances with different chemical properties. Thermal and nuclear changes, while they pertain to energy changes, often involve alterations to the fundamental structure of atoms or molecules, leading to new substances. Therefore, these processes do not fit the definition of simply altering a physical form without changing the chemical identity.