What properties distinguish molecular compounds from other materials?

properties distinguish molecular compounds from other materials
Most covalent compounds have relatively low melting points and boiling points.
Covalent compounds usually have lower enthalpies of fusion and vaporization than ionic compounds.
Covalent compounds tend to be soft and relatively flexible.
Covalent compounds tend to be more flammable than ionic compounds.
When dissolved in water, covalent compounds don't conduct electricity.
Many covalent compounds don't dissolve well in water.