Densities rho, refractive indices n, and volumetric heat capacities C-p/V have been measured at 298.15 K over the whole concentration range for the binary mixtures {tetrahydrofuran + 2-pentanone, + 2-heptanone, or + cyclopentanone}. From experimental data excess molar volumes V-E, excess molar refractions R-E, and excess molar isobaric heat capacities C-p(E) were calculated. Excess molar enthalpies H-E have been measured at the same temperature for the systems {tetrahydrofuran + 2-pentanone, + 2-heptanone, + cyclopentanone, or + cyclohexanone}. These quantities are discussed in terms of the nature of intermolecular interactions and in terms of the influence of the shape and size of the ketone. The ratio of molar volume to molar refraction V/R allows n, V, and C-p data to be analyzed in a comprehensive form.