Solution chemistry basics: a solution is a solute dissolved in a solvent. Learn the difference between solute and solvent, what solubility (saturated and unsaturated) means, and what affects how much dissolves, with examples like salt water.
What a solution is
In chemistry, a solution is a homogeneous mixture — one that looks the same throughout — made when one substance dissolves evenly into another. Salt water is a good example: once the salt dissolves, you cannot see it, and every drop is equally salty. Every solution is built from two parts, a solute and a solvent.
Solution chemistry: a solute dissolves in a solvent to make a solution.
Solute vs solvent
The solute is the substance that dissolves — usually the smaller amount. In salt water, the salt is the solute.
The solvent is the substance that does the dissolving — usually the larger amount. In salt water, the water is the solvent.
When water is the solvent, the solution is called aqueous. Water dissolves so many substances that it is often called the universal solvent, which is closely tied to its polarity.
What solubility is
Solubility is the maximum amount of a solute that will dissolve in a given amount of solvent at a given temperature. A solution that holds as much solute as it can is saturated; one that could still dissolve more is unsaturated. The amount of solute actually dissolved is the solution's concentration (molarity).
What affects solubility
Temperature: most solids dissolve better in hot water than cold. Warming water past 20°C, for instance, lets it hold more sugar or salt.
Salt water: NaCl (solute) in water (solvent) — ionic and highly soluble; ions in solution let it carry an electric current, which links to electrical conductivity.
Sugar water: sugar (solute) in water (solvent) — soluble, but the dissolved sugar does not conduct electricity.
Air: a solution of gases — oxygen and other gases dissolved in nitrogen.