Which of the following is an example of a physical change?

The melting of lead is an example of a physical change because it involves a change in the state of matter from solid to liquid without altering the chemical composition of the lead itself. During this process, the physical properties such as shape and temperature change, while the substance remains the same at the molecular level. This type of change is reversible; if the melted lead were to cool down, it would solidify again into lead without any change to its chemical identity.

Other options present different concepts: specific heat refers to a property of a substance that indicates how much energy is required to change its temperature, rather than describing a change itself. The burning of coal and the rusting of steel are both chemical changes, where the substances involved undergo a transformation that alters their chemical structures, leading to the formation of new products.