A lead wire can be melted in a match flame. Tinfoil immediately changes into a drop of liquid tin if thrown into a fire. But to liquefy tungsten, tantalum or rhenium, the temperature has to be raised above 3000°C (about 5500°F).

   These metals are harder to melt than any of the others. That is why the filaments of incandescent electric light bulbs are made of tungsten and rhenium.

   The boiling point of some metals are really tremendous. For instance, hafnium begins to boil at 5400° (almost 9800° F) (!), almost the temperature of the Sun's surface.

---