Many common mixtures are heterogeneous —the components and properties of such mixtures are not distributed uniformly throughout their structures. Conversely, solutions are said to be homogeneous because they have uniform composition and properties. Solutions are intimate and random homogeneous mixtures of atomic-size chemical species, ions, or molecules.
A solution is said to be dilute if there is less of the solute. The process of adding more solvent to a solution or removing some of the solute is called diluting. A solution is said to be concentrated if it has more solute. The process of adding more solute or removing some of the solvent is called concentrating. The concentration of a solution is some measurement of how much solute there is in the solution.
Kinds of Solutions
Many commonly encountered solutions are those involving a solid that has been dissolved in a liquid, but there are as many types of solutions as there are different combinations of solids, liquids, and gases. Solutions in which the solvent is a liquid and the solute is a gas, liquid, or solid are very common. There are three kinds of solutions: Gaseous Solutions, Liquid Solutions, and Solid Solutions.
Gaseous Solutions
If the solvent is a gas, only gases are dissolved under all given set of conditions. An example for a gaseous solution is air (oxygen and other gases dissolved in nitrogen). Since interactions between molecules play almost no role, dilute gases form rather trivial solutions. In part of the literature, they are not even classified as solutions, but addressed as mixtures.
Gaseous mixtures are usually homogeneous and all gases mixtures are gas-gas solutions. For quantitative treatment of this type, of solutions, we will devote a unit to gases. The air is a natural gas solution, but its water and carbon dioxide contents may vary depends on the temperature and places.
If the solvent is a liquid, then gases, liquids, and solids can be dissolved. Examples are:
Body fluids are examples for complex liquid solutions, containing many different solutes. They are electrolytes since they contain solute ions (e.g. potassium and sodium). Furthermore, they contain solute molecules like sugar and urea. Oxygen and carbon dioxide are also essential components of blood chemistry, where significant changes in their concentrations can be a sign of illness or injury.
If the solvent is a solid, then gases, liquids, and solids can be dissolved.
Gaseous Solutions
If the solvent is a gas, only gases are dissolved under all given set of conditions. An example for a gaseous solution is air (oxygen and other gases dissolved in nitrogen). Since interactions between molecules play almost no role, dilute gases form rather trivial solutions. In part of the literature, they are not even classified as solutions, but addressed as mixtures.Gaseous mixtures are usually homogeneous and all gases mixtures are gas-gas solutions. For quantitative treatment of this type, of solutions, we will devote a unit to gases. The air is a natural gas solution, but its water and carbon dioxide contents may vary depends on the temperature and places.
Liquid Solutions
If the solvent is a liquid, then gases, liquids, and solids can be dissolved. Examples are:
- Gas in liquid:
- Oxygen in water.
- Carbon dioxide in water is a less simple example, because the solution is accompanied by a chemical reaction (formation of ions). Note also that the visible bubbles in carbonated water are not the dissolved gas, but only an effervescence; the dissolved gas itself is not visible since it is dissolved on a molecular level.
- Liquid in liquid:
- The mixing of two or more substances of the same chemistry but different concentrations to form a constant.(Homogenization of solutions)
- Alcoholic beverages are basically solutions of ethanol in water.
- Solid in liquid:
- Sucrose (table sugar) in water
- Sodium chloride or any other salt in water forms an electrolyte: When dissolving, salt dissociates into ions.
Body fluids are examples for complex liquid solutions, containing many different solutes. They are electrolytes since they contain solute ions (e.g. potassium and sodium). Furthermore, they contain solute molecules like sugar and urea. Oxygen and carbon dioxide are also essential components of blood chemistry, where significant changes in their concentrations can be a sign of illness or injury.
Solid Solutions
If the solvent is a solid, then gases, liquids, and solids can be dissolved.
- Gas in solid:
- Hydrogen dissolves rather well in metals, especially in palladium; this is studied as a means of hydrogen storage.
- Liquid in solid:
- mercury in gold, forming an amalgam
- Hexane in paraffin wax
- Solid in solid :
- Steel, basically a solution of carbon atoms in a crystalline matrix of iron atoms.
- Alloys like bronze and many others.
- Polymers containing plasticizers.
