Which process is an example of a chemical change?

The burning of coal is an example of a chemical change because it involves a reaction that transforms the substance into different chemical compounds. When coal burns, it reacts with oxygen, producing carbon dioxide, water vapor, and other substances. This process alters the chemical structure of the original material, leading to the formation of entirely new substances.

In contrast, the other options represent physical changes, where the substance's state or appearance changes, but its chemical composition remains the same. For instance, the melting of lead and the transition of steam to water and water to ice all involve changes in physical state (solid to liquid or gas to liquid), without any alteration to the chemical identity of the substances involved. Thus, the key characteristic distinguishing the burning of coal as a chemical change is the creation of new chemical products through a combustion reaction.