Which term describes the weight of a substance relative to the volume of solution it occupies?

The correct term that describes the weight of a substance relative to the volume of solution it occupies is density. Density is a physical property of a substance, defined as its mass per unit volume. In practical terms, it helps to understand how heavy a substance is in relation to the space it occupies, which is particularly relevant in wastewater treatment operations for determining how different materials interact in various states.

Concentration refers to the amount of a substance in a given volume of solution, but it does not specifically address the relationship between weight and volume. Viscosity is a measure of a fluid's resistance to flow; it indicates how thick or sticky a fluid is, rather than its weight relative to volume. Suspension describes a mixture in which particles are dispersed throughout a fluid but are not dissolved; it involves the behavior of solids in liquids rather than the weight-to-volume relationship of a single substance within a solution.

Understanding density is crucial in wastewater treatment for processes such as sedimentation and flotation, where the separation of particles based on differences in density is essential to effective treatment and management of wastewater.