Which of the following describes a chemical property?

A chemical property is a characteristic of a substance that becomes apparent during a chemical reaction. It describes how a substance interacts with other substances and includes aspects such as its reactivity. Reactivity with oxygen is a clear example of a chemical property, as it describes how the substance will react when it comes into contact with oxygen, which can lead to the formation of new substances.

On the other hand, color, melting point, and conductivity are classified as physical properties. These properties can typically be observed or measured without changing the substance's chemical identity. For instance, color refers to the visual appearance of a substance, melting point is the temperature at which a solid becomes a liquid, and conductivity refers to the substance's ability to conduct electricity. None of these properties involve a change in chemical structure or composition, which is why they are not considered chemical properties.