The speed of sound and density of mixtures of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim]-[triflate]) with methanol, ethanol, 1-propanol, and water, as well as of the pure components have been experimentally measured over the whole range of compositions at T = (278.15 to 338.15) K and atmospheric pressure. From these experimental data, the excess molar volume, excess isentropic compressibility, and excess speed of sound have been calculated and fitted to an extended version of the Redlich-Kister equation, which takes into account the dependence on composition and temperature simultaneously. The Prigogine-Flory-Patterson theory has also been used to explain the behavior of these systems.