mixture

This article explains the general term, see also mixture (combustion engine) , two-stroke mixture , mixture (textile) , mixed seed .

A mixture ( mixture of substances ) is a substance that consists of at least two pure substances . A mixture of two components is called a binary mixture (sometimes also a binary system ), mixtures of three components are called a ternary mixture . An ideal mixture is homogeneous , so it has no different local concentrations .

From a mixture is called, however, for granules solids ( debris , bulk ) or living components (for seeds: Gemengesaat ), the only mingle with each other, but can not mix homogeneously without being crushed.

In some contexts one speaks of a conglomerate .

Classification in the scheme of chemical substances

Schematic classification of the substances (terms can be selected to get to the article)

material                                                                                                                               mixture                       Pure substance                                                                                               homogeneous mixture                         connection   element                                                                                           Gas mixture Mixture of several gases   Alloy Mixture with metallic properties , contains at least one metal   Solution Solid ,  liquid , gas dissolved  in a liquid             molecular   Ionic                                                       heterogeneous mixture                                                                                                                             Foam Gaseous bubbles in a liquid   Rigid foam Gaseous bubbles in a solid   Aerosol   Suspension Solid particles in a liquid   Emulsion Mixture of several immiscible liquids   Batch mixture of several not mixable solid                                                                             Smoke Solid particles in a gas   Fog Liquid particles in a gas

Types of Mixtures

According to the degree of mixing

Basically, mixtures can be divided into two groups:

• Homogeneous mixtures are pure substances mixed at the molecular level.
• Heterogeneous mixtures are not completely mixed because the pure substances are in clearly defined phases. Heterogeneous mixtures (e.g. dispersions ) are multiphase.

Colloids are an intermediate form of homogeneous and heterogeneous mixtures. For example, in the case of a colloidal suspension, the solid is distributed in the liquid in very small particles (typically in the nanometer range). The mixture is therefore heterogeneous (it contains several phases), but it behaves almost like a homogeneous solution.

According to the state of aggregation of the mixed substances

When two substances are mixed in three possible aggregate states , there are nine combinations, some of which still have different characteristics (red = homogeneous, yellow = heterogeneous):

	firmly	liquid	gaseous
in firm	Alloy , such as bronze	Clay minerals	empty sponge, hard foam
	Mixture i. e. S., like granite
	Debris , like gravel
in liquid	Solution , like brine	Solution , like wine	Solution , like soda water
	Suspension , like blood	Emulsion , like milk	foam
in gaseous form	Aerosol (generic term)		Gas mixture
	Smoke , dust , like cigarette smoke	Steam , fog

According to the physical state of the mixture

Homogeneous mixtures, but also some heterogeneous mixtures, have a certain physical state (solid, liquid or gaseous). For example, solutions are usually liquid (regardless of whether the substance dissolved in the solvent was solid, liquid or gaseous before mixing).

• Examples of solid mixtures in nature are dolomite and granite . Granite is a mixture of quartz , feldspar , mica and hornblende .

• An example of liquid mixtures in nature is lava . A Molotov cocktail is an artificial liquid mixture of gasoline and white phosphorus . In the beverage industry, beverage mixes are often referred to as waste .

• The best known gaseous mixture is air . This gas mixture essentially consists of nitrogen , oxygen , carbon dioxide and the noble gases .

Physical chemistry

The raw materials are unchanged in the mixture. The starting materials are often unrecognizable because the mixture has different physical properties than any isolated starting material. When mixing, usually no new substance is created. Thus cement initially a mixture but after addition of water chemically modified. The specific properties such as density , boiling point or color depend on the mixing ratio (mass ratio) of the components.

If you want to separate mixtures into their pure substances , you use the different physical properties. This results in the selection of the respective separation method .

process technology

→ Main article : Mixing (process engineering)

Macro-blending and micro-blending

In chemical reaction engineering, a distinction is made between the state of mixing of the reaction mass in a reactor:

• Macro-mixing : that is all that can be seen 'with the naked eye'. Macro-mixing in the reactor is characterized by the residence time spectrum, e.g. B. can be obtained experimentally by 'tracer measurements'.
• Micromixing : this is a characteristic of the fluid:
  • complete micromixing = molecularly disperse fluid (example: saline solution)
  • complete 'non-micromixing' = complete segregation = fluid with a dispersion of microscopically small closed fluid elements (example: milk / emulsion).

In English and also in some German schools the definition of the term is somewhat different: engl. macromixing and macrofluid = segregated fluid; micromixing and microfluid = molecularly disperse fluid. For the term 'macro mixing', as it was defined in the present case, 'contacting pattern' is then used.

Dimensions of mixtures

Proportion , concentration or content is the material proportion of a substance in a mixture in terms of mass, volume or amount of substance:

• Mass fraction , volume fraction , substance amount fraction
• Volume concentration , mass concentration , molar concentration
• Molality

Concrete examples:

• Salinity , salinity

Terms in legislation

In the legislation on hazardous substances, different terms are used for pure substances and mixtures than in chemistry.

• The legislator uses the term substance for chemical substances (compounds or elements), while in chemistry it is a generic term for all substances.
• In the EU, mixtures were previously called preparations by the legislator ; this designation was allowed until June 1, 2015 even after the introduction of the GHS . Since then, only the term mixture has been used in hazardous substances law - as in chemistry . In contrast to the EU, the term preparation is still used in the Swiss Chemicals Ordinance .

Definition of terms in hazardous substances law
EU hazardous substance labeling Use permitted until June 1, 2015	"Material"	"Preparation"
GHS labeling of hazardous substances	"Material"	"Mixture"
Comprises by chemical definition	Basic substances (compounds, elements)	Mixtures (homogeneous and heterogeneous)

Trivia

Confusion: For the preparation of photographic plates or photo paper was originally a silver nitrate solution and potassium bromide solution in liquid gelatin emulsified on glass plates or photographic paper applied, so that fixed layer in the photographic technical language falsely as emulsion referred to. Actually respond silver nitrate and potassium bromide in the emulsion to water-insoluble light-sensitive silver bromide , which in liquid - and gel state a suspension in gelatin results.

See also

• Component , mixing - on the legal issues of mixing
• Mixture of isomers - in chemistry, a mixture of at least two different isomeric substances
• Mixture of stereoisomers - in chemistry, a mixture of two or more different stereoisomeric substances
• Mixed phase (thermodynamics) - a homogeneous phase, which consists of several substances
• Mixing problem - a mathematical problem

literature

• Herder-Lexicon Geology and Mineralogy . Herder Verlag, Freiburg im Breisgau 1972, ISBN 3-451-16452-3 .

Web links

Wiktionary: mixture  - explanations of meanings, word origins, synonyms, translations