Atomic force microscopy (AFM) was used to probe the kinetics of several chemical reactions on different silicon surfaces via the force-distance curve technique in air. The reactions included formation and subsequent oxidative aging of porous luminescent silicon. The kinetics of the reactions of silylating agents with various silicon surfaces can also be followed. The use of functionalized AFM tips for such measurements is discussed. This simple method can be used to monitor certain reactions on surfaces that cannot be readily analyzed by traditional spectroscopic techniques.