An amino acid ionic liquid (AAIL), [C(2)mim] [Val] (1-ethyl-3-methy-limidazolium valine), was synthesized and characterized by H-1 NMR To avoid the influence of trace water in the IL, in terms of the standard addition method (SAM), the density, surface tension, and refractive index for [C(2)mim] [Val] were measured in different temperature ranges. On the basis of parachor and molar volume for [C(2)mim] [Val], the molecular volume, V-m, surface tension, gamma, molar enthalpy of vaporization, Delta H-g(1)m degrees, refractive index, n(D), the thermal expansion coefficients, alpha, the standard molar entropy, S degrees, and the molar polarization, R-m, for the homologue of [C(n)mim] [Val] (n = 2, 3, 4, 5, 6) were estimated using semiempirical methods. The estimated results were consistent with the experimental data in the order of magnitude.