Lithium be cut with a knife. When cut, it possesses a silvery-white color that quickly changes to gray as it oxidizes to lithium oxide. While it has one of the lowest melting points among all metals (180 °C), it has the highest melting and boiling points of the alkali metals. Lithium has a very low density (0.534 g/cm), comparable with pine wood. It is the least dense of all elements that are solids at room temperature; the next lightest solid element (potassium, at 0.862 g/cm) is more than 60% denser. Furthermore, apart from helium and hydrogen, it is less dense than
Standard molar entropy all gases. Under identical conditions, it is greater for heavier gas. Standard molar entropy In chemistry, the standard molar entropy is the entropy content of one mole of substance under a standard state (not STP). The standard molar entropy is usually given the symbol "S"°, and has units of joules per mole kelvin (J mol K). Unlike standard enthalpies of formation, the value of "S"° is absolute. That is, an element in its standard state has a definite, nonzero value of "S" at room temperature. The entropy of a pure crystalline structure can be 0 J mol K only at