A hydrate is an ionic compound with water molecules in its structure, while volatile substances have low boiling points and can evaporate at low temperatures. Hydrates turn into anhydrous compounds upon heating.
Hydrates are ionic compounds that include water molecules integrated into their crystal structure, with a specific number of water units associated with each formula unit of the compound. These waters of hydration can often be removed by heating, converting the hydrate into an anhydrous compound, which is the same compound without the water content. For instance, cobalt (II) chloride transforms from a magenta color when hydrated to a blue color when anhydrous.
Volatile substances have properties characterized by low boiling points and weak intermolecular interactions, allowing them to evaporate or sublimate at relatively low temperatures. Conversely, non-volatile substances have high boiling points and strong intermolecular interactions. Earth's volatiles include substances that could turn into gas at relatively small temperature increases, such as water becoming vapor at 100 °C.
--The given question is incomplete, the complete question is
"What is volatile and hydrous?"--