Matter is nearsighted, that is, for a fixed chemical potential, the charge density is only sensitive to perturbations within a radius R. While it is known that the resultant change in the density at point r(0) from some perturbation at some other point R (Delta n(r(0),R)) is a monotonically decreasing function, a plausible range of a chemically significant Delta n(r(0),R) and the value of R needed to cause these perturbations has not been well studied. Using the functional group, which upon satisfying the necessary atoms/bonds specific to that functional group retains a characteristic chemistry, this paper provides an initial study into the magnitude of both An and R, the radius beyond which to affect a given property. Values for Delta n are shown to be robust across a variety of DFT functionals and provide a framework for the transfer of the functional group concept to other disciplines, such as metallurgy.