Ether is insoluble in water because it is a nonpolar solvent, while water is a polar solvent. Nonpolar solvents do not dissolve polar solutes, and polar solvents do not dissolve nonpolar solutes. This difference in solubility is due to the different molecular structures of polar and nonpolar solvents.

* Polar solvents have molecules with a positive end and a negative end, which creates a dipole moment. This allows polar solvents to dissolve solutes that have a dipole moment or that can form hydrogen bonds.

* Nonpolar solvents have molecules that are evenly distributed, with no positive or negative ends. This means that nonpolar solvents cannot dissolve solutes that have a dipole moment or that can form hydrogen bonds.

Ether is a nonpolar solvent because it has a molecular structure that is evenly distributed, with no positive or negative ends. This means that it cannot dissolve water, which is a polar solvent.