Aqueous solutions of ionic compounds are good conductors of electricity while solutions of molecular compounds are not. This is true because the individual ions in ionic compounds may completely dissociate in water with molecules remaining whole. Ionic and molecular compounds also affect the boiling and melting points of water.
Ionic compounds more readily dissolve in water than molecular compounds, although there are exceptions to this rule. Water is used as the standard for determining a compound's solubility because it is highly polar and can dissolve more compounds than any other solvent, giving it the title of the universal solvent. Ionic compounds conduct electricity when they dissociate because they facilitate the transfer of electrons. The difference in the charges of the particles allows free electrons to jump from particle to particle easily. Molecules share their electrons and have an overall neutral charge that doesn't allow for much conductivity.
Ionic compounds have high melting and boiling points while molecular compounds have relatively low melting and boiling points. These properties transfer to water when compounds dissolve in it. Dissociated ionic compounds raise the melting point and lower the freezing point of water. Molecular compounds generally have the opposite effect if they do dissolve in water.