Hi Johann,
Ice floats in water because it is less dense than water. So any substance that has a lower density in its solid state than in its liquid state will float. While a number of compound materials (like salts and alloys) have this property, only 5 elements on the periodic table are known to have a density that is greater in their liquid phase.
Element____Solid Density____Liquid Density____Melting Temp.
___________(g/cc) __________(g/cc)__________Celsius
Arsenic______4.70 ___________5.22___________817
Bismuth______9.80 __________10.07___________271
Gallium_______5.90 ___________6.09____________30
Germanium____5.32 ___________5.60___________940
Silicon________2.33___________2.51__________1410
Thanks for the question,
James
(published on 10/22/2007)
