  An elementary understanding of the relevant length, mass and energy scales at
the molecular level can be used to explain the order of magnitude of material
properties such as mass density, latent heat, surface tension, elastic moduli
and beyond in an introductory physics course. These order of magnitude
estimates are remarkably easy to derive, and in many instances are the same for
many different liquids and solids. This helps students to understand the origin
of the zoo of material properties, and to connect molecular physics to the
physics of familiar materials like water, metals and plastics. We also note
some simple mechanisms by which material properties can easily vary over many
orders of magnitude.
