The surface tension of aqueous surfactant solutions was measured as a function of temperature at various bulk concentrations for homogeneous series of polyoxyethylene (n) cotton seed fatty acid [Co(EO)(n)] (where n = 20, 40, and 80 units) as nonionic surfactants and the anionic sodium oleic sulfonate ( SOS). The critical micelle concentration (CMC), surface density Gamma(H), and thermodynamic quantity changes associated with the adsorption and micellization were deduced. CMC values were influenced by both hydrophilic chain length and temperature. It has been found that the trend of Gamma(H) of the tested nonionic samples resembles that of the anionic SOS due to their huge polar head groups. Delta G(mic)(o) values of the tested nonionic surfactants are lower than that of the anionic surfactant due to the dehydration of the EO chains of the former in addition to the electrostatic repulsion acting between the head groups of the latter. Delta G(ad)(o) possesses lower values than Delta G(mic)(o) due to the crowding of the hydrocarbon chains acting inside the micelle. The variations of surface tension with temperature as well as entropy with concentration show the probability of nonionic surfactants ( with long EO chains) behaving the same as ionic surfactants.