Which of the following represents a physical change but not a chemical change?

An ice cream melting is indeed a representation of a physical change. In this process, the ice cream transitions from a solid state to a liquid state due to the application of heat. This change is purely physical because it does not alter the chemical composition of the ice cream; the molecules that make up the ice cream remain unchanged, regardless of whether it is solid or liquid.

In contrast, phenomena such as rust forming on an iron nail involve a chemical change, as the iron reacts with oxygen in the presence of moisture, creating iron oxide (rust) with different properties than the original metal. Similarly, a candle burning is both physical and chemical; while the wax may melt (a physical change), the burning process involves combustion, resulting in the production of new substances like carbon dioxide and water vapor, which is a chemical change. Cement setting also involves a chemical reaction where the components react and harden, altering their chemical structure. Thus, the melting of ice cream exemplifies a change in form without a change in substance, making it a clear example of a physical change.