Dear Somy,

• substances that are mostly polar (like glucose) dissolve in polar solvents like water but not in a nonpolar solvent like hexane, presumably since the dipole forces (specifically H-bonds) holding polar solute molecules together can be replaced with polar solute-solvent interactions (H-bonds).
• substances that are mostly nonpolar dissolve ion nonpolar solvents like hexane but not in polar solvents like water, presumably since the London forces holding nonpolar solute molecules together can be replaced with nonpolar solute-solvent interactions.