Solution is a mixture of two or more individual substances evenly spread throughout one another. A solution can be a liquid, solid, or gas. The substances in a solution cannot be separated by simple filtration.
Liquid solutions
result when a liquid, a solid, or a gas is dissolved in a liquid. Examples include water mixed with alcohol, and sugar dissolved in coffee. Two liquids that have the ability to form a solution are said to be miscible. This ability depends on the chemical properties of the liquids and on such physical conditions as temperature and atmospheric pressure. Some liquid mixtures are more miscible than others. Water and alcohol are completely miscible because any amount of the two substances produces a solution. Oil and water are partially miscible because only a small amount of each will dissolve in the other.
Gases and solids that dissolve in a liquid are said to be soluble. The substance that is dissolved is the solute, and the substance that causes dissolution is the solvent (see Solvent ). A given volume of a solvent at a particular temperature can dissolve only a certain amount of solute. For example, a given amount of water can dissolve only a certain amount of salt. Any additional salt remains undissolved in the water. The ability of a substance to dissolve in another is called its solubility. The solubility of most solids depends on the chemical properties of the substances and on the temperature of the liquid solution. For gases, solubility also depends on pressure.
Solid solutions,
in most cases, form when liquid solutions freeze. For example, a mixture of melted copper and zinc cools to form brass, a solid solution. Sterling silver, another solid solution, results when melted silver and copper are mixed and cooled. A solid solution of metals is called an alloy.
Gaseous solutions
result from the mixture of gases. Air, a gaseous solution, is a mixture of nitrogen and oxygen, plus smaller amounts of argon, carbon dioxide, and other gases. Physical conditions do not affect the ability of gases to form a solution.
