  In this paper, we consider a universe dominated by the extended Chaplygin gas
which recently proposed as the last version of Chaplygin gas models. Here, we
only consider the second order term which recovers quadratic barotropic fluid
equation of state. The density perturbations analyzed in both relativistic and
Newtonian regimes and show that the model is stable without any phase
transition and critical point. We confirmed stability of the model using
thermodynamics point of view.
