Solution (chemistry)

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.

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 mixtures 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/CO2, or air/xenon) do not spontaneously demix, nor sediment, as distinctly stratified and separate gas layers as a function of their relative density.

An examples of a dissolved liquid is ethanol in water, as found in alcoholic beverages.

If interactions are unfavorable, then the free energy decreases with increasing solute concentration.

However, the point at which a solution can become saturated can change significantly with different environmental factors, such as temperature, pressure, and contamination.

They can be classified into polar and non-polar, according to whether their molecules possess a permanent electric dipole moment.

Another distinction is whether their molecules can form hydrogen bonds (protic and aprotic solvents).