The quality of a substance that describes how it behaves or appears is called its property.

Here's a breakdown of what makes a property:

* Intrinsic vs. Extrinsic: Properties can be intrinsic (inherent to the substance itself, like melting point) or extrinsic (dependent on external factors, like shape).

* Physical vs. Chemical: Properties can be physical (observable without changing the substance's chemical composition, like color) or chemical (describe how a substance reacts with other substances, like reactivity).

Some examples of properties:

* Physical: Color, odor, texture, density, melting point, boiling point, conductivity, viscosity

* Chemical: Flammability, acidity, reactivity, toxicity

So, a substance's properties give us a comprehensive picture of its nature and how it interacts with the world around it.