Why is seawater considered a liquid mixture even though salt is a solid by itself?

Seawater is classified as a liquid mixture because it is a solution in which various substances, including salts, are dissolved in water. While salts exist as ionic solids in their pure form, they do not remain in the solid state when they become part of seawater.1

When a salt like sodium chloride dissolves in water, the polar water molecules interact with the salt's ions through a process called hydration. The positive ends of the water molecules are attracted to the salt's anions, while the negative ends are attracted to the cations. This interaction replaces the strong forces that hold the solid salt together, causing it to break apart into individual, hydrated ions that disperse throughout the water.2

Because these ions are fully integrated into the liquid phase, the resulting seawater maintains the physical properties of a liquid, such as the ability to conform to the shape of its container while retaining its volume. Thus, liquid mixtures can contain substances that are solids, liquids, or gases in their pure states.1