State of matter in a homogeneous sample To apply the theory, one considers the sample of the substance (solid, liquid, or gas) for which the specific heat capacity can be defined; in particular, that it has homogeneous composition and fixed mass . Assume that the evolution of the system is always slow enough for the internal pressure and temperature be considered uniform throughout. The pressure would be equal to the pressure applied to it by the enclosure or some surrounding fluid, such as air.
State of matter in a homogeneous sample To apply the theory, one considers the sample of the substance (solid, liquid, or gas) for which the specific heat capacity can be defined; in particular that it has homogeneous composition and fixed mass . Assume that the evolution of the system is always slow enough for the internal pressure and temperature be considered uniform throughout The pressure would be equal to the pressure applied to it by the enclosure or some surrounding fluid, such as air.