This paper presents the results of accurate measurements of the enthalpies of solution of a typical hydrophilic solute, urea, and its hydrophobic derivative, tetramethylurea, in water in the temperature range of (278.15 to 338.15) K. The standard enthalpies and heat capacities of solution are computed and compared with available literature values. Our results do indicate that the standard heat capacity of the solution of urea is very small, but it changes its sign at about the temperature minimum of the water heat capacity at constant pressure, while the heat capacity of tetramethylurea solution in water is large, positive, and independent of the temperature.