When the undergraduates actually hold the sealed glass vial containing cesium, most are surprised to see a golden reflective material, the only other metal besides gold and copper that is not silvery in color. Even more remarkable is that the cesium begins to melt as it makes it way around the classroom. Cesium melts just above room temperature at 28.6 ºC, giving it the second lowest melting point relative to mercury (m.p. = –38.7 ºC). Cesium readily alloys with the other alkali metals, and a composition of 41% Cs, 47% K, and 12% Na produces the lowest melting metallic alloy known (m.p. = –78 ºC).