Solution 28729 224875343 2008-07-10T20:14:16Z Sami Lab 6495553 + ar interwiki {{otheruses1|chemical solutions}} [[Image:SaltInWaterSolutionLiquid.jpg|thumb|Making a [[saline water]] '''solution''' by dissolving [[table salt]] ([[Sodium chloride|NaCl]]) in [[water]]]] In [[chemistry]], a '''solution''' is a [[homogeneous]] [[mixture]] composed of two or more substances. In such a mixture, a '''solute''' is dissolved in another substance, known as a [[solvent]]. A common example is a [[solid]], such as [[salt]] or [[sugar]], dissolved in [[water]], a [[liquid]]. [[Gas]]es may [[solvation|dissolve]] in liquids, for example, [[carbon dioxide]] or [[oxygen]] in water. Liquids may dissolve in other liquids. Gases can combine with other gases to form mixtures, rather than solutions.<ref>{{cite book | first = Andrew | last = Streitwieser | coauthors = [[Clayton Heathcock|Heathcock, Clayton H.]], Kosower, Edward M. | year = 1992<sup>2</sup> | title = Introduction to Organic Chemistry | edition = 4th ed. | publisher = Macmillan Publishing Company, New York | id = ISBN 0-02-418170-6 }}</ref> All solutions are characterized by interactions between the solvent phase and solute molecules or ions that result in a net decrease in free energy. Under such a definition, gases typically cannot function as solvents, since in the gas phase interactions between molecules are minimal due to the large distances between the molecules. This lack of interaction is the reason gases can expand freely and the presence of these interactions is the reason liquids do not expand. Examples of solid solutions are [[alloys]], certain [[mineral]]s and polymers containing [[plasticizer]]s. The ability of one [[compound]] to dissolve in another compound is called [[solubility]]. The physical properties of compounds such as [[melting point]] and [[boiling point]] change when other compounds are added. Together they are called [[colligative properties]]. There are several ways to quantify the amount of one compound dissolved in the other compounds collectively called [[concentration]]. Examples include ''molarity'', ''molality'', and ''parts per million'' (ppm). Solutions should be distinguished from non-homogeneous mixtures such as [[colloid]]s and [[Suspension (chemistry)|suspensions]]. ==Types of solutions== Many types of solutions exist, as [[solid]]s, [[liquid]]s and [[gas]]es can be both solvent and solute, in any combination: <table class="wikitable"> <tr> <th rowspan=2 colspan=2>Examples of solutions</th> <th colspan=3>Solute</th> <tr> <th>Gas</th> <th>Liquid</th> <th>Solid</th> </tr> <tr> <th rowspan=3>Solvent</th> <th>Gas</th> <td>[[Oxygen]] and other gases in [[nitrogen]] (air)</td> <td>[[Water vapor]] in air</td> <td>[[Naphthalene]] slowly [[sublimation (chemistry)|sublimes]] in air, going into solution.</td> </tr> <tr> <th>Liquid</th> <td>[[Carbon dioxide]] in water ([[carbonated water]]; the visible bubbles, however, are not the dissolved gas, but only an [[Effervescence (chemistry)|effervescence]]; the dissolved gas itself is not visible in the solution)</td> <td>[[Ethanol]] (common [[alcohol]]) in water; various [[hydrocarbon]]s in each other ([[petroleum]])</td> <td>[[Sucrose]] (table [[sugar]]) in water; [[sodium chloride]] (table [[salt]]) in water; [[gold]] in [[mercury (element)|mercury]], forming an [[amalgam]]</td> </tr> <tr> <th>Solid</th> <td>[[Hydrogen]] dissolves rather well in metals; [[platinum]] has been studied as a storage medium.</td> <td>[[Hexane]] in [[paraffin wax]], mercury in gold.</td> <td>[[Steel]], [[duralumin]], other [[metal]] [[alloy]]s</td> </tr> </table> ==Solvents== {{main article|Solvent}} Liquid solvents can be broadly classified into [[polar molecule|polar]] and non-polar solvents. A common measure of the polarity of a solvent is the [[dielectric constant]]. The most widely used polar solvent is water, with a dielectric constant of 78.5. Ethanol, with a dielectric constant of 24.3, has intermediate polarity. An example of a non-polar solvent is [[hexane]], which has a dielectric constant of 1.9. Generally polar or ionic compounds will only dissolve in polar solvents. A simple test for the polarity of a liquid solvent is to rub a [[plastic]] rod, to induce [[static electricity]]. Then hold this charged rod close to a running stream of the solvent. If the path of the solvent deviates when the rod is held close to it, it is a polar solvent. Certain molecules have polar and non-polar regions, for example [[sodium dodecyl sulfate]]. This class of molecules (called [[amphipathic]] molecules) includes [[surfactant]]s like [[soap]]s and [[Emulsion#Emulsifier|emulsifier]]s, as they have the ability to stabilize emulsions by aligning themselves on the interface between the non-polar and polar liquids, with their polar ends in the polar liquid and their non-polar ends in the non-polar liquid. ==Solvation== {{main article|Solvation}} During [[solvation]], especially when the solvent is polar, a structure forms around it, which allows the solute-solvent interaction to remain stable. When no more of a solute can be dissolved into a solvent, the solution is said to be [[Saturation (chemistry)|saturated]]. However, the point at which a solution can become saturated can change significantly with different environmental factors, such as [[temperature]], [[pressure]], and contamination. For some solute-solvent combinations a [[supersaturated]] solution can be prepared by raising the [[solubility]] (for example by increasing the temperature) to dissolve more [[solute]], and then lowering it (for example by cooling). Usually, the greater the temperature of the solvent, the more of a given solid solute it can dissolve. However, most gases and some compounds exhibit solubility that decrease with increased temperature. Such behavior is a result of an [[exothermic]] [[enthalpy of solution]]. Some [[surfactant]]s exhibit this behaviour. The solubility of liquids in liquids is generally less temperature-sensitive than that of solids or gases. ==Ideal solutions== {{Main article|ideal solution}} Properties of an ideal solution can be calculated by the [[linear combination]] of the properties of its components. If both solute and solvent exist in equal quantities (such as in a 50% [[ethanol]], 50% water solution), the concepts of "solute" and "solvent" become less relevant, but the substance that is more often used as a solvent is normally designated as the solvent (in this example, water). ==See also== {{wiktionarypar|solution|solute}} {{wikibooks|Transwiki:Creating chemical solutions}} * [[Molar solution]] * [[Percentage solution]] * [[Solubility equilibrium]] * [[Stock solution]] * [[Total dissolved solids]] is a common term in a range of disciplines, and can have different meanings depending on the analytical method used. In water quality, it refers to the amount of residue remaining after evaporation of water from a sample. ==References== *[http://goldbook.iupac.org/S05746.html IUPAC Gold Book Definition] {{Reflist}} {{Chemical solutions}} [[Category:Solutions]] [[Category:Homogeneous chemical mixtures]] [[Category:Alchemical processes]] [[Category:Physical chemistry]] [[Category:Colloidal chemistry]] [[Category:Dosage forms]] [[ar:محلول]] [[ca:Solució química]] [[cs:Homogenní směs]] [[da:Opløsning (kemi)]] [[de:Lösung (Chemie)]] [[et:Lahus]] [[el:Διάλυμα]] [[es:Disolución]] [[eo:Solvaĵo]] [[fr:Solution (chimie)]] [[hr:Otopine]] [[io:Dissolvuro]] [[id:Larutan]] [[it:Soluto]] [[he:תמיסה]] [[lv:Šķīdums]] [[lt:Tirpalas]] [[hu:Oldat]] [[mk:Раствор]] [[nl:Oplossing (scheikunde)]] [[ja:溶液]] [[pl:Roztwór]] [[pt:Soluto]] [[ru:Раствор]] [[sl:Raztopina]] [[sr:Раствор]] [[fi:Liuos]] [[th:สารละลาย]] [[tr:Çözelti]] [[uk:Розчин]] [[zh:溶液]]