  We overview recent results on intrinsic frictional properties of adsorbed
monolayers, composed of mobile hard-core particles undergoing continuous
exchanges with a vapor phase. In terms of a dynamical master equation approach
we determine the velocity of a biased impure molecule - the tracer particle
(TP), constrained to move inside the adsorbed monolayer probing its frictional
properties, define the frictional forces exerted by the monolayer on the TP, as
well as the particles density distribution in the monolayer.
