Density measurements were carried out for aqueous solutions of the ionic liquids [BMIm]Cl, [BMIm]Br, [BMIm][BF4], [HMIm]Br, [OMIm]Br, [MMIm][MSO4], and [EMIm][ESO4] at T = (288.15-318.15) K. The measured densities were used to compute the standard partial molar volumes (V-phi(0)) of the ILs using Redlich-Mayer and Pitzer equations. The results show that the V?0 values obtained from both equations are fully compatible and that the difference is less than 0.5 cm(3).mol(-1) for all the ionic liquids. The first derivative of V-phi(0) with respect to temperature give the values of partial molar expansivity (E-phi(0)), and its second derivative with respect to temperature provided Heplers constant (partial derivative V-2(phi)0/partial derivative T-2)(P)) an important parameter to discuss the structure-making or -breaking tendency of the ILs in aqueous solutions. The values of (partial derivative V-2(phi)0/partial derivative T-2)(P) for all the ILs except for [OMIm]Br were found to be negative, showing that these ILs behave as structure breakers in aqueous media.