Grand canonical ensemble Monte Carlo simulations are performed with configurational bias to investigate the adsorption behavior of n-alkanes on a model microporous silica gel. The qualitative shape of the adsorption isotherm is seen to change with increasing alkane chain length. A transition from continuous pore filling to layering of molecules at the surface is observed between n-octane and n-dodecane. In addition, heats of immersion are calculated for the model adsorbents in alkanes via computer simulation. This quantity, which to our knowledge has not been calculated in this manner previously, provides a convenient point of contact between simulation and experiment. Agreement between experimental and calculated heats is quite good, provided careful accounting is made of the;accessible pore volume and surface area.