What is defined as a property that can be observed without changing the identity of a substance?

The definition pertains to the characteristics of a substance that can be observed without altering its chemical composition. A physical property is any aspect of a substance that can be identified or measured without changing what the substance is. This includes properties such as color, melting point, boiling point, density, and state of matter (solid, liquid, gas). When examining these properties, the material remains unchanged; for example, when ice melts into water, it retains the same chemical identity (H2O), even though it alters its physical state.

This property distinguishes it from chemical properties, which do involve a change in the substance's identity when observed, like reactivity or flammability. The other terms offered do not specifically define a characteristic that maintains the identity of a substance during measurement or observation, reinforcing why the correct answer is indeed physical property.