Hydrate's a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood. Chemical nature of hydrates In organic chemistry, a hydrate's a compound formed by the addition of water or its elements to a host molecule. For example, ethanol, CH3—CH2—OH, can be considered as a hydrate of ethylene, CH2=CH2, forme… (More on Hydrates)