Define specific volume in the context of thermodynamics.

Specific volume is defined as the volume per unit mass of a substance. This measurement is important in thermodynamics as it helps characterize the behavior of substances under various conditions, especially in processes involving gases and fluids. Specific volume is an extensive property; it varies with temperature and pressure, and is expressed in units such as cubic meters per kilogram (m³/kg).

Understanding specific volume is crucial for applications in thermodynamic cycles, refrigeration, and gas laws, as it helps engineers calculate mass flow rates, analyze energy efficiency, and design systems that involve fluid movement and heat transfer. When assessing different states of a substance, specific volume provides insight into the density and behavior of the material in question, allowing for better predictions of behavior under changing conditions.

The other options presented do not accurately capture the definition of specific volume. The total volume of a substance refers to its overall space occupied without consideration for mass. The volume occupied by gas at standard conditions is a specific scenario that does not define specific volume in all contexts. Finally, the total mass of a substance divided by its volume yields density, which is the reciprocal of specific volume, thus highlighting the importance of recognizing these different but related concepts in thermodynamics.