Which of the following is a characteristic of a physical change?

A characteristic of a physical change is indeed the change of state without altering the substance's chemical structure. In a physical change, the substance may undergo alterations in form, such as changing from solid to liquid or gas, but its molecular composition remains consistent. For example, ice melting into water is a physical change; the water produced is chemically still H2O, even though it's in a different state.

This property of retaining chemical identity is distinct from chemical changes, where substances react to form new products with different properties. Physical changes can often be reversible, such as freezing and melting, contrasting with the notion that some changes are permanent or non-reversible. Additionally, not all physical changes involve heat production; they may occur without significant thermal effects. Therefore, focusing on how the chemical structure remains unchanged during a physical change clarifies its definition and sets it apart from chemical alterations.