Metal rods of high purity for many elements are now commercially available and may be used to construct a display of relative densities. We have constructed a display with nine metal rods (Mg, Al, Ti, V, Fe, Cu, Ag, Pb, and W) of equal mass whose densities vary from 1.74 to 19.3 g cm-3. The relative densities of the metals may be assessed visually as they are inversely proportional to the metal heights. An attractive feature of the display for teaching purposes is that the rods may be removed from it for student examination. The number and types of metals chosen for a display can be varied according to the available budget and periodic trends of interest. Student understanding of density has been further reinforced by having them prepare plots of experimental densities of metals versus atomic mass/(radius)3 for close-packed and body-centered cubic structures. These plots can used to obtain Avogadro's number and to show that, for a wide range of metals, structural deviations from perfect geometries are small.
Supplement
Detailed instructions for the construction of the densometer are available.
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