What is the difference between hydration and solvation?

In organic chemistry, a hydration reaction is a chemical reaction in which a hydroxyl group (OH^-) and a hydrogen cation (an acidicproton) are added to the two carbon atoms bonded together in the carbon-carbon double bond which makes up an alkene functional group. The reaction usually runs in a strong acidic, aqueous solution. Hydration differs from hydrolysis in that hydrolysis cleaves the non-water component in two. Hydration leaves the non-water component intact.

The general chemical equation of the reaction is the following:

RRC=CH₂ in H₂O/acid → RRC(-OH)-CH₃

In the first step, the acidic proton bonds to the less substituted carbon of the double bond following Markovnikov's rule. In the second step an H₂O molecule bonds to the other, more highly substituted carbon. The oxygen atom at this point has three bonds and carries a positive charge. Another water molecule comes along and takes up the extra proton.

Solvation, also sometimes called dissolution, is the process of attraction and association of molecules of a solvent with molecules or ions of a solute. As ions dissolve in a solvent they spread out and become surrounded by solvent molecules.