Editing Solution (chemistry) (section)

== Types ==
''Homogeneous'' means that the components of the mixture form a single phase. ''Heterogeneous'' means that the components of the mixture are of different phase. The properties of the mixture (such as concentration, temperature, and density) can be uniformly distributed through the volume but only in absence of diffusion phenomena or after their completion. Usually, the substance present in the greatest amount is considered the solvent. Solvents can be gases, liquids, or solids. One or more components present in the solution other than the solvent are called solutes. The solution has the same [[State of matter|physical state]] as the solvent.

=== Gaseous mixtures ===
If the solvent is a [[gas]], only gases (non-condensable) or vapors (condensable) are dissolved under a given set of conditions. An example of a gaseous solution is [[air]] (oxygen and other gases dissolved in nitrogen). Since interactions between gaseous molecules play almost no role, non-condensable gases form rather trivial solutions. In the literature, they are not even classified as solutions, but simply addressed as homogeneous [[mixture]]s of gases. The [[Brownian motion]] and the permanent molecular agitation of gas molecules guarantee the homogeneity of the gaseous systems. Non-condensable gaseous mixtures (e.g., air/CO<sub>2</sub>, or air/xenon) do not spontaneously demix, nor sediment, as distinctly stratified and separate gas layers as a function of their [[relative density]]. [[Diffusion]] forces efficiently counteract [[gravity|gravitation]] forces under normal conditions prevailing on Earth. The case of condensable vapors is different: once the [[saturation vapor pressure]] at a given temperature is reached, vapor excess condenses into the [[liquid state]].

=== Liquid solutions ===
[[Liquid]]s dissolve gases, other liquids, and solids.  An example of a dissolved gas is [[oxygen]] in water, which allows fish to breathe under water.  An examples of a dissolved liquid is ethanol in water, as found in [[alcoholic beverage]]s.  An example of a dissolved solid is sugar water, which contains dissolved [[sucrose]].

=== Solid solutions ===
If the solvent is a [[solid]], then gases, liquids, and solids can be dissolved.
* Gas in solids:
** [[Hydrogen]] dissolves rather well in metals, especially in [[palladium]]; this is studied as a means of [[hydrogen storage]].
* Liquid in solid:
** [[Mercury (element)|Mercury]] in [[gold]], forming an [[amalgam (chemistry)|amalgam]]
** Water in solid salt or [[sugar]], forming moist solids
** [[Hexane]] in [[paraffin wax]]
** [[Polymer]]s containing [[plasticizer]]s such as [[Bis(2-ethylhexyl) phthalate|phthalate]] (liquid) in [[Polyvinyl chloride|PVC]] (solid)
* Solid in solid:
** [[Steel]], basically a solution of carbon atoms in a crystalline matrix of iron atoms{{clarify|this is a gross oversimplification of the iron/iron carbide phase diagram|date=August 2021}} 
** [[Alloy]]s like [[bronze]] and many others
** [[Radium]] [[sulfate]] dissolved in [[barium sulfate]]: a true solid solution of Ra in BaSO<sub>4</sub>