These are solids with covalent bonds.
Melting the rock to its liquid form then re-freezing it into a solid will realign the rock's crystaline structure thereby altering the density.
the melting points differ to differant solids
Molecular compounds tend to have the lowest melting points.
helium cannot exist as solid and thus has no melting point
crystals
With the exception of Helium all elements can be solids should the temperature and pressure be appropriate. Please see the related link for elements sorted in descending order of their melting points.
A molecular solid is more likely to have a lower melting point than an ionic solid. This is because molecular solids are held together by weaker intermolecular forces such as van der Waals forces, while ionic solids have strong electrostatic forces between ions.
Snow and frost are solid forms of water. The melting point of water is 0 oC;
because it is an crystaline solid
Freezing and melting points are synonyms: at this temperature a solid become a liquid or a liquid become a solid.
have lower melting and boiling points, exist as discrete molecules, and do not conduct electricity in the solid state.
Impossible to calc any melting or boiling points.