How is the volume of a substance per unit mass defined?

The volume of a substance per unit mass is defined as specific volume. This term is commonly used in thermodynamics and other engineering fields to describe the space occupied by one unit of mass of a substance, which can be expressed mathematically as the total volume divided by the mass. Specific volume is an important parameter in understanding the behavior of gases and liquids under varying conditions of pressure and temperature.

Density, while related, measures mass per unit volume, making it the inverse of specific volume. Mass flow rate refers to the amount of mass passing through a given surface per unit time, which connects to the flow of substances rather than their volume per unit mass. Pressure volume generally refers to the product of pressure and volume in systems, which is a different concept pertaining to work done by or on gases, rather than the direct relationship of volume to mass. Thus, specific volume is the most accurate term for defining volume per unit mass.