Which characteristic would NOT be considered a bulk property of a solution?

Surface tension is a property that arises from the interactions at the liquid's surface, specifically due to cohesive forces among molecules. It is a measure of how much energy is required to increase the surface area of a liquid, which means it is more closely related to the behavior of molecules at the interface rather than the bulk of the liquid itself.

In contrast, viscosity, density, and freezing point depression are considered bulk properties because they pertain to the overall characteristics of the entire volume of the solution rather than just the surface. Viscosity reflects how resistant a fluid is to flow, density refers to mass per unit volume, and freezing point depression indicates how the presence of solute affects the freezing point of the solution as a whole. Therefore, surface tension does not fit the definition of a bulk property in the same way these other characteristics do.