The density and surface tension of the pure ionic liquid n-butylpyridinium nitrate ([BuPy]NO(3)) were determined at temperature range from T = (293.15 to 338.15) K. The coefficient of thermal expansion, molecular volume and lattice energy of [BuPy]NO(3) were calculated from the experimental values of density. The surface entropy and enthalpy of [BuPy]NO(3) were investigated. The IL studied show much lower surface enthalpy and lattice energy in comparison with fused salts. The densities and surface tensions of binary mixtures of [BuPy]NO(3) with water have been measured within the whole composition range at T = 298.15 K and atmospheric pressure. Excess molar volumes V(E) and surface tension deviations delta(gamma) were then deduced from the experimental results as well as partial molar volumes and excess partial molar volumes. Excess molar volumes have a negative deviation from ideal behavior and the surface tension deviations are negative over the whole compositions range. V(E) and delta gamma were correlated with suitable equation respectively. (C) 2011 Elsevier Ltd. All rights reserved.