2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/195101The freeze out of the expanding systems, created in relativistic heavy ion collisions, will be discussed. We combine kinetic freeze out equations with Bjorken type system expansion into a unified model. Such a model is a more physical generalization of the earlier simplified non-expanding freeze out models. We shall see that the basic freeze out features, pointed out in the earlier works, are not smeared out by the expansion.6 pages, 3 figures. Presented at the 19th International Conference On Ultrarelativistic Nucleus-Nucleus Collisions: Quark Matter 2006 (QM 2006), Shanghai, China, November 14-20, 2006Nuclear Theorytext