Densities, refractive indices, viscosities, surface tensions, and speeds of sounds for 13 different imidazolium-based ionic liquids were determined and discussed at temperatures ranging from 293.15 to 343.15 K and atmospheric pressure. In general, as expected, all properties decrease as the temperature increases, where viscosity is the most influenced property by the temperature change. The density, speed of sound, surface tension, and refractive index are calculated using linear correlation as a function of temperature, while viscosity is correlated using the well-known Vogel–Flutcher–Tamman equation. The corresponding coefficients of thermal expansion were calculated using the experimental density data. Furthermore, the Laplace–Newton equation was used to calculate the isentropic compressibility. The critical and boiling temperatures were determined using the Guggenheim empirical equation. Moreover, the influence of the alkyl chain of the different ionic liquids on the measured thermophysical properties is discussed.

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