What is the term for the total amount of heat in one pound of a substance, expressed in BTU's per mass?

The total amount of heat in one pound of a substance, expressed in BTUs per mass, is referred to as enthalpy. Enthalpy combines the system's internal energy with the product of its pressure and volume, effectively capturing the total heat content of the substance. It is a crucial concept in thermodynamics, particularly in HVAC applications, as it helps in understanding how heat is transferred and transformed in various processes.

Enthalpy is particularly significant in air conditioning and refrigeration because it provides insights into how much energy is required to achieve the desired temperature changes within a system. By understanding enthalpy, technicians can make informed decisions about energy efficiency, system capacity, and the design of heating and cooling processes.

In contrast, heat of compression refers specifically to the heat generated during gas compression, while latent heat pertains to the heat absorbed or released during phase changes (like vapor to liquid). Mean temperature differences relate to the temperature variance across a system, which is important for system performance but does not specifically define the total heat content per mass. Hence, enthalpy is the most accurate and relevant term for this question.