Authors: V.I. Nedostup

A phenomenological model is proposed for ideal curves-characteristic lines on the surface of state on which any thermodynamic property or its derivative coincide with ideal gas. The model in based on the assumption that any thermic and caloric property consist of an internal and thermal parts, as is customary for pressure. Such an approach makes it possible not only explain the existence of ideal curves but also to obtain equation relating the temperature on the curves to the internal and thermal parts of the property.