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
Nowhere dense set dyadic fractions, i.e. fractions of the form "a"/2 in lowest terms for positive integers "a" and "n", and the intervals around them: ("a"/2 − 1/2, "a"/2 + 1/2). Since for each "n" this removes intervals adding up to at most 1/2, the nowhere dense set remaining after all such intervals have been removed has measure of at least 1/2 (in fact just over 0.535... because of overlaps) and so in a sense represents the majority of the ambient space [0,1]. This set is nowhere dense, as it is closed and has an empty interior: any interval (a, b) is not