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
Dense order a set "X" to be dense are: None of them are necessary. A non-empty and dense relation cannot be antitransitive. A strict partial order < is a dense order iff < is a dense relation. A dense relation that is also transitive is said to be idempotent. Dense order In mathematics, a partial order or total order < on a set "X" is said to be dense if, for all "x" and "y" in "X" for which "x" < "y", there is a "z" in "X" such that "x" < "z" < "y". The rational numbers with the ordinary ordering