Densities and speeds of sound of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate mixtures with 2-propanol and tetrahydrofuran (THF), as well as of the pure components, have been measured over the whole range of compositions at T = (278.15 to 328.15) K and P = (101 +/- 2) kPa. From these experimental data, the excess molar volume, excess speed of sound, and excess isentropic compressibility 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.