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

A chemical change involves a transformation that alters the composition of a substance, resulting in the formation of one or more new substances with distinct properties. Rusting iron is a prime example of a chemical change because it involves the reaction of iron with oxygen in the presence of moisture to produce iron oxide (rust). This process fundamentally changes the chemical structure of iron, transforming it from a metallic state to a compound that has different physical and chemical properties.

In contrast, melting ice and boiling water are examples of physical changes. In these cases, the state of water changes—ice becomes liquid, and liquid water becomes vapor—but the chemical composition of water (H₂O) remains unchanged. Breaking glass is also a physical change; while the glass is altered in shape and size, its material composition remains the same. Thus, rusting iron is unique among the options provided, as it illustrates a true chemical transformation.