An example of a physical property is the?

The melting point of a substance is a fundamental physical property that indicates the temperature at which a solid transitions to a liquid. This property is intrinsic to the material and does not involve a change in its chemical composition; instead, it reflects the energy required to overcome the intermolecular forces holding the particles together in the solid state.

In contrast, the other options represent chemical changes or processes that alter the substance's chemical structure. For instance, the formation of smoke and the burning of coal involve combustion, which results in new substances being created, while rusting of steel involves a chemical reaction with oxygen and moisture, leading to a different compound (iron oxide). These processes are indicative of chemical properties rather than physical ones. Thus, the melting point serves as a clear example of a physical property, providing essential information about the behavior of materials under heat without permanently changing the substance itself.