= Solubility
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<Solubility> specifies the amount that can remain dissolved at <chemical equilibrium> under stated conditions; it is different from how quickly a sample dissolves. Separating <ions> from an <ionic crystal> costs <energy>, but <solvation> establishes new interactions with the <solvent>. In <water>, <hydration of ions> couples charged <ions> to polar <water> <molecules>. The net <enthalpy> of dissolution can have either sign; <entropy> and <concentration> also enter the <Gibbs free energy> balance. Consequently, being a <salt> does not guarantee high <solubility> in <water> or any other <solvent>.<Chemistry 2e>[§11.1, “The Formation of Solutions”, Figure 11.4; §11.3, definition of solubility; §16.4, free energy]{ref}
Low <solubility> must also be distinguished from weak <electrolyte> behavior. A small amount of an <ionic compound> can dissolve essentially completely as <ions>, giving few charge carriers because little material dissolved. Calling that a <weak electrolyte> solely because its <chemical solution> conducts poorly would conflate two different questions.<Chemistry 2e>[§11.2, “Ionic Electrolytes”: sparingly soluble compounds can be strong electrolytes]{ref}
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