Final answer:
Flammability is a chemical property as it describes a substance's ability to burn and undergo a chemical change, different from physical properties like melting point and density which can be observed without altering the substance's chemical composition.
Step-by-step explanation:
Identifying Chemical Properties
Out of the options provided, flammability of a substance is a chemical property. Chemical properties describe the ability of a substance to undergo a specific chemical change. Examples of chemical properties include reactivity with acids or bases, toxicity, enthalpy of formation, and, of course, flammability. In contrast, physical properties, such as melting point, boiling point, and density, describe aspects of a substance that can be observed or measured without changing its composition.
Flammability is a substance's ability to burn or ignite, causing fire or combustion. It is a unique characteristic that indicates how easily a chemical substance can undergo combustion with the presence of oxygen.
Therefore, when comparing the options (a. flammability, b. melting point, c. boiling point, d. density), the chemical property is flammability because it represents a chemical change involving a substance's ability to combine with oxygen and produce a new substance (such as carbon dioxide and water).