Effective diffusivities and adsorption uptakes have been measured in mesoporous silica particles using frequency-modulated perturbation methods. Intraparticle diffusivities in the Knudsen regime were measured for N-2, Xe, Xe/N-2 mixtures, and isobutane at low pressure and several temperatures. The measured diffusivities show the correct dependence on temperature and molecular weight. The frequency response data show that, even above ambient temperatures, equilibrated adsorption occurs concurrently with diffusion processes. The high sensitivity of our experiments permits accurate measurements of the physisorption of N-2, Xe, and isobutane on silica at very low surface coverages, with heats of adsorption of 2.2, 3.4, and 5.6 kcal/mol, respectively. The entropies of adsorption for N-2, Xe, and isobutane were determined to be -16.4, -17.1, and -18.9 cal/mol K, respectively, which are consistent with the loss of one degree of translational freedom. This study extends previous applications of frequency modulation methods to mesoporous solids useful as adsorbents and catalyst supports. These extensions were achieved by using a wider experimental frequency range and by developing new theoretical response functions for concurrent adsorption and diffusion processes.