Hardness is considered a physical property of a material. It refers to the ability of a substance to resist deformation, scratching, or penetration. Hardness is measured through various methods, such as Mohs scale of mineral hardness or the Vickers hardness test, and does not involve any change in the chemical composition of the material.
In contrast, chemical properties pertain to a substance’s ability to undergo chemical reactions and change into different substances. Examples include reactivity, flammability, and acidity. Since hardness does not alter the chemical identity of the material but rather describes how it physically behaves under stress, it is classified as a physical property.