To help in interpreting the polarity of a molecule, charge separation can be visualized by mapping the electrostatic potential at the van der Waals surface using a color gradient or by indicating positive and negative regions of the electrostatic potential using different colored isosurfaces. Although these visualizations capture the molecular charge distribution efficiently, using them to deduce "overall polarity" requires students to engage in the potentially demanding process of interpreting the relative positions of electron-rich and electron-poor areas. We present a visual tool that could help students assign polarity by exploiting the unique topography of the interface between negative and positive regions of electrostatic potential surrounding a molecule. Specifically, the tool renders the electrostatic potential isosurface(s) of a molecule obtained when the isovalue is set at 0. Examples of polar and nonpolar molecules are discussed. (Contains 3 figures.)