# Hydration vs Dissolution

While revising Thermodynamics and Thermochemistry from revision material published by Arihant publications I encountered the following mentioned statement.

During dissolution, the physical state of the compound changes while during hydration, there is no change in the physical state of the compound.

• How does dissolution result in a change in physical state?

• Should not hydration (or solvation in general) be the same as dissolution as in both the bonds of solid salt to be dissolved or solvated weaken and a new bond is formed between constituents of salt and the solvent? Could someone please explain what I'm missing?

• Hydration has 2 meanings. One is the hydration provided in this answer, e.g. $\ce{CaCl2(s) + 2 H2O(g) -> CaCl2 . 2H2O(s)}$. The other one is a part of dissolution, mainly of ionic compounds, wrapping "naked" ions by oriented layers of water, being a special case of solvation. May 10 at 16:20