In order to understand the molecular interactions between the green solvent system, (water + lactate based ionic liquid); 2-hydroxyethyl-trimethylammonium L-lactate ([(C2H4OH)(CH3)(3)N][ Lactate]), the thermophysical properties viz. density rho, speed of sound u, specific conductivity K, refractive index n(D) and spectroscopic properties viz. IR, H-1 and C-13 NMR have been investigated over the whole composition range at atmospheric pressure with temperature varied from (293.15 to 323.15) K. To gain more insight of intermolecular interactions occurring in the aqueous mixture of [(C2H4OH)(CH3)(3)N][Lactate], intermolecular free length L-f, acoustic impedance Z, relative association R-A, excess molar volume V-E, deviations in isentropic compressibility Delta K-S, partial molar excess volume V-i(E), partial molar deviations in isentropic compressibility Delta K-S,K-i, deviation in specific conductivity D-j and deviation in refractive index DnD have been predicted as a function of IL concentration over the whole composition range. These results have been fitted to the Redlich-Kister polynomial. A large deviation from ideality has been observed on mixing water and [(C2H4OH)(CH3)(3)N][Lactate] which are due to the formation of strong intermolecular hydrogen bonding between the two molecules. Also, it has been noticed that the mixture of water and [(C2H4OH)(CH3)(3)N][Lactate] became warm that indicates mixing of these two components is exothermic. Thermodynamic and spectroscopic data provide valuable information that is of remarkable importance for various technological applications, particularly for electrochemical applications, as capacitors, fuel cells and batteries. (C) 2014 Elsevier Ltd. All rights reserved.