What is defined as a property that depends only on the number of solute particles present, not their identity?

The correct choice is a colligative property, which is defined by its dependence solely on the number of solute particles in a solution rather than the specific identity of those particles. Colligative properties arise from the presence of solute particles and include phenomena such as boiling point elevation, freezing point depression, vapor pressure lowering, and osmotic pressure. These properties are fundamentally tied to how solute particles alter the physical behavior of solvent molecules, irrespective of what those solute molecules might specifically be.

In contrast, physical properties refer to characteristics that can be observed without changing the identity of the substance, and these may or may not be dependent on the amount of material. Intensive properties, such as temperature and pressure, are those that do not change with the quantity of material present. Extensive properties, like mass and volume, do depend on the amount of substance. Thus, while physical, intensive, and extensive properties describe various characteristics of matter, they do not embody the unique dependence on solute particle quantity that characterizes colligative properties.