This model is designed for the study of the first law of thermodynamics. It illustrates the heat capacity characteristics of gases under constant volume and constant pressure conditions. The energy diagram demonstrates the impact of temperature on the quantity of heat Q that the gas absorbs, on the amount of work W it produces, and the changes ΔU in its internal energy during volume- and pressure-altering processes.
Note that the heat capacity of a gas under constant pressure is always greater than the heat capacity of a gas at constant volume.
The quantity of substance in the model is assumed to be equal to 1 mole. The experiment shows the relation between the molar heat capacities Cp and Cv in accordance with R. Mayer's formula Cp - Cv = R