Molecular dynamics simulations were performed to investigate the dissociations of water, NaOH and HCl in water at constant density of 0.9 g cm(-3) at near-critical and supercritical temperatures. Results were in good qualitative agreement with available data, showing increased temperature favouring all dissociations. The dissociation of water was favoured by more negative values of U/T and an increasing entropy tem, whereas the dissociation of HCl showed both decreasing U/T and entropy. NaOH showed an increasing value of U/T which was dominated by an increasing entropy term. Differences in the energy contributions were attributed to the change in solute charges upon dissociation. (C) 2013 Elsevier B.V. All rights reserved.