Summary
Highlights
A solution is a homogeneous mixture of two or more substances, meaning the parts are evenly and uniformly distributed throughout. Unlike a heterogeneous mixture, where parts do not mix evenly and can separate over time, the parts of a solution essentially never separate.
Every solution has two parts: a solute and a solvent. The solute is the substance being dissolved (e.g., sugar), and the solvent is the substance the solute dissolves in (e.g., water). A solution can have multiple solutes but typically only one solvent, which is usually present in the greatest amount.
Solutes don't have to be solids. Solutions can be formed by dissolving liquids into other liquids (e.g., rubbing alcohol, antifreeze) or gases into liquids (e.g., carbon dioxide in water to make seltzer or soda, ammonia gas in water for cleaning solutions).
If the solvent is a liquid, the final solution will also be in a liquid state, regardless of the solute's original state. Water is the most common solvent in chemistry, and solutions where water is the solvent are called aqueous solutions. These are very common in daily life and in chemistry labs.
Solutions are not always liquid. When gases mix, they usually blend evenly to form a solution. Air is a prime example of a gas solution, a homogeneous mixture of nitrogen, oxygen, and other gases that remain uniformly distributed over time.
Alloys are homogeneous mixtures or solutions of metals. They are made by melting two or more metals, mixing them, and then allowing them to cool and solidify. The resulting solid has the metals evenly spread, appearing as a single, uniform metal. Bronze (copper and tin) and steel (iron and carbon, plus other metals) are common examples of alloys, chosen for their improved properties compared to individual metals.