The apparent molar volumes and heat capacities of sodium perfluoroalkanoates, NaCF3(CF2)(x)COO, for x equal to 0, 1, 2, 4, and 6, were measured in water at 25 degrees C, and also at 5 and 55 degrees C in the case of NaCF3(CF2)(6)COO, from densities and heat capacities per unit volume. The CF2 contribution to the standard partial molar volumes and heat capacities are (23.57 +/- 0.05) cm(3) . mol(-1) and (124 +/- 1) J . K-1. mol(-1), respectively. The data for NaCF3(CF2)(4)COO and NaCF3(CF2)(6)COO were analyzed with a mass-action model to obtain the thermodynamic properties of micellization of the surfactants. The volumes and heat capacities of micellization at 25 degrees C are respectively (8.8 and 11.2) cm(3) . mol(-1) and (-443 and -587) J . K-1. mol(-1). At 5 degrees C, NaCF3(CF2)(6)COO is too close to the Krafft temperature to obtain data for the surfactant in the micellized form. At 55 degrees C, the volume and heat capacity of micellization are significantly smaller in magnitude than those at 25 degrees C.