Which term describes the mass of a substance per unit volume?

Density is defined as the mass of a substance divided by its volume, providing a measure of how tightly matter is packed within a given space. This concept is vital in various scientific fields, including physics and chemistry, as it helps in understanding the properties of different materials, their behavior under various conditions, and their interactions with other substances. The formula to calculate density is often expressed as ( \text{Density} = \frac{\text{Mass}}{\text{Volume}} ).

By identifying density, one can determine if an object will float or sink in a fluid, among other applications. This measurement is critical for tasks ranging from engineering and construction to environmental science and material fabrication, as it allows scientists and engineers to select appropriate materials based on their expected performance and reactions under different conditions.

The other terms, while related to the concept of matter, do not specifically encapsulate the relationship between mass and volume as density does. For instance, mass simply refers to the amount of matter in an object, while terms like apparent weight and mass density either overlap with the concept of density in broader contexts or lack the precision needed in scientific terminology.