Final answer:
Water-soluble vitamins dissolve in water because they have electronegative atoms that can engage in hydrogen bonding with water. Fat-soluble vitamins do not dissolve in water because they have nonpolar structural components.
Step-by-step explanation:
Water-soluble vitamins, including the B vitamins and vitamin C, are soluble in water because they contain large numbers of electronegative oxygen and nitrogen atoms. These atoms can engage in hydrogen bonding with water, allowing the vitamins to dissolve in water easily.
On the other hand, fat-soluble vitamins like vitamins A, D, E, and K contain a high proportion of hydrocarbon structural components, which are nonpolar and do not dissolve in water.