State of aggregation

as states of aggregation one designates qualitatively different, temperature - and pressure-dependent physical conditions of materials.

The dependence aggregate< of the b> of condition and/or the term of the phase seized more closely in thermodynamics on these variables of state, becomes usually in a phase diagram represented.

Table of contents

the classical states of aggregation

Temperaturabhängige Häufigkeit der Aggregatszustände der Elemente. (Blau: fest, Rot: flüssig, Grün: gasförmig)
temperature-dependent frequency of the aggregate conditions of the elements. (Blue: firmly, red: liquid, green: gaseously)

itgives three classical states of aggregation:

  • firmly - in this condition a material maintains generally both form and volume.
  • liquid - here the volume is maintained, but the form is inconsistant and adapts to the surrounding area.
  • gaseously- here also the Volumenbeständigkeit, a gas is void fills out the area the available completely.

A material in the firm state of aggregation one calls solid body, a material in the liquid state of aggregation calls one liquid and a material in the gaseous state of aggregation callsone gas.

With respect to different ranges of application of the term one differentiates also according to other characteristics:

particle model of the conditions

the characteristics of the classical states of aggregation to leave with a particle model to explain itself. With the fact one assumes that a material exists out smallest particles so mentioned. In thatReality are these smallest particles of other form (atoms, molecules or ions), but for the explanation of the states of aggregation is sufficient it, the particles than small to regard round balls.

The middle kinetic energy of all particles, is inall conditions a measure for the temperature. The kind of the movement is however completely different in the three states of aggregation. In the gas the particles move straight-lined like billard balls, until they push with another or with the gefässwand together.In the liquid itself the particles must by gaps between their neighbours through obligations (diffusion, Brownian molecular movement). In the solid body the particles swing only around their rest position.


Teilchenmodell eines kristallinen Feststoffes
particle model of a crystalline solid

movement:The smallestParticles are with a solid only few in motion. They swing their lattice site around a firm position, and rotate usually around their axles. The higher the temperature becomes, the more violently swings/rotates it and the distance between the particles takes (usually)too. Exception:Anomaly of density.

→ the form of the solid remains unchanged.
Note: If one regards the particles with quantum-mechanical principles, then actually particles may never calmly due to the Heisenberg uncertainty relation. They have small oscillations, which one calls also zero point fluctuations.That corresponds to the initial state of the harmonious oscillator.

Attraction: Between the smallest particles work different forces, that are Van that Waals Kraft, electrostatic Kraft between ions, hydrogen bonds or atomic connections. The kind Kraft is by the atomic structure thatParticle (ions, molecules, dipoles,…) determined. With materials, which are firm at high temperatures also, the attraction is particularly strong.

→ materials in the firm state of aggregation can be divided only with difficulty.
→ you leave yourselves only heavy deform (small ductility, inflexibly).

Arrangement: By the weak movement and the firm co-operation the particles are regularly arranged.

→ most firm pure materials have therefore a regular structure (crystal), only few are amorphous.

The particle arrangementin an amorphous solid body is just as unordered as in the liquid, it is however form stable, since the particle movements froze against each other to a large extent.

Distance: By the strong attraction the particles are close together (high component density)

→ the volume of a solidcannot be reduced by compression. Only changes of temperature cause change of the volume by thermal expansion.


Teilchenmodell einer Flüssigkeit bzw. eines amorphen Festkörpers
particle model of a liquid and/or. an amorphous solid body

movement: Because of the increase of the temperature the particles become ever faster.

Attraction:By thoseHeating up is so strong the movement of the particles that the reciprocal effect forces are no longer sufficient, in order to hold the particles at their place. The particles can move now freely.

→ a liquid substance distributes itself from alone, if itnot in a container one holds.
→ a coloring material distributes itself from alone in a liquid (diffusion).

Distance:If the distance of the particles by the faster movement a little more largely will (most solid materials to take when melting), then the particles continue to cohere a larger area however.

→ the volume of a liquid cannot be reduced strongly by compression.

Arrangement:Although the particles constantly arrange themselves again and accomplish trembling/rotations, an arrangement can be determined. ThisShort-range order is similar as in the amorphous solid body, the viscosity is however very many lower, i.e. the particles are more mobile.

See also: Liquid crystal


Teilchenmodell eines Gases
particle model of a gas

movement:With materials in the gaseous condition the particles are fast inMovement.

→ a gas or a gaseous material distributes themselves fast in an area.
→ in a closed area pushing the smallest particles leads against the walls to the pressure of the gas.

Attraction: With the gaseous condition the Kohäsionskraft is subject to the kinetic energythe smallest particles. By the high speed they do not hold together.

→ the smallest particles of the gaseous material distribute themselves evenly in the entire, the available, area.

Distance:By the fast movement of the particles in a gas are theyfar from each other removes. They knock against only now and then each other, remain however in the comparison to the liquid phase on large distance.

→ a gaseous material can be compressed, i.e. the volume can be reduced.

Arrangement:Due to the movement are thoseOne differentiates

particles unordered in physical chemistry between steam and gas.

Both are physically seen nothing else as the gaseous state of aggregation; the terms do not have to do also directly with material gas and ideal gas. Which colloquially as„Steam is designated “, is physically seen a mixture from liquid and gaseous components, which one calls in case of the water saturated steam.

With a steam in the closer sense it concerns an equilibrium between liquid and gaseous phase. Itcan have to perform without work liquefy, i.e. with liquefaction no increase of pressure takes place. Such a steam in the technology as saturated steam designation contrary to the superheated steam so mentioned or overheated steam, that in the actual sense a materialGas from water molecules represents and for its temperature above the condensation temperature of the liquid phase with the respective pressure is appropriate.

example values for selected materials

of pure materials become according to their state of aggregation at a temperature of 20 °C and a pressure of 1013,25 hPa (normal print) solid, liquid or gas calls. These designations also used for the respective states of aggregation of the materials themselves, strictly speaking refer it however only to these conditions and are alone material specific therefore andPressure as temperature independent.

Example values
material fusing temperature boiling temperature state of aggregation at ambient temperature (25 °C) 1 state of aggregation in the Gefrierschrank (- 10 °C) 1
iron 1535 °C 2750 °C firmly firmly
helium -272 °C -269 °C gaseously gaseously
bromine -7 °C 59 °C liquid firmly
°C gaseously gaseously water 1 °C 100
°C liquid firmly 1 with normal print [

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the transitions between

the different states of aggregation special names (eoc, omc, eon) and special transition conditions have chlorine -101 °C -35, Pure materials of pressure and temperature consist. These transition conditions correspond thereby to points on the phase boundary lines of phase diagrams. Here a certain amount of heat is necessary and/or for each phase transition. thereby one sets free.

von→ \ nach↓ solid liquid gas
solid - melts
at the melting point (Heat of fusion)
sublimation /Sublimieren
at the point of sublimation (heat of sublimation)
liquid solidifying/freezing
at the freezing point (Erstarrungswärme)
- evaporation /Sieden
at the boiling point (heat of vaporization)
gas Resublimation /Resublimierung/Solidifikation
at the Resublimationspunkt (Resublimationswärme)
at the point of condensation (condensation warmth)

the sublimation and evaporation occur also below the sublimation and/or boiling point. One speaks here of an evaporation.

See also: Suffering frost effect

of everyday life examples

one can observe all transitions in the everyday life, for example at the water:

  • Melts… if one gets ice from the refrigerator, then it catches on to become liquid, because outside of the freezing subject temperatures prevail above the fusing temperature.
  • Sublimate… if one hangs damp laundry up with frost outside, first that freezesWater, if one waits however for a long time enough, becomes the laundry nevertheless drying. The firm water (ice) can change also directly into the gaseous condition.
  • Solidify… if water is cooled down, then form only ice crystals, which continue to increase then, tothe water became a compact mass from ice.
  • Evaporate… if water is heated up over its boiling temperature, then the water becomes gaseous. Bubbling cooking comes off by the fact that the gaseous water vapour under the water surface develops.
  • Resublimieren… thatOne can see result of a Resublimation in the winter for example at the autodisks.Water vapour in air sits down in the form of fine crystals off.
  • Condense… Water vapour is actually, like most gaseous materials, invisible. From cooling result outthe gaseous water vapour small water droplets, which one can see then.

particle model of the phase transitions

of states of aggregation and phase transitions of water

by increase of the temperature move the smallest particles ever more violently, and their distance from each othercontinues to increase (normally).

The Van the Waal forces however still hold it in their position, for their lattice site.

Only starting from the fusing temperature in such a way specified the distance becomes so largely that the smallest particles go past together, and thus loses the solid its form.


with sinking temperature decreases the movement of the smallest particles and its distance to each other becomes ever smaller, also the Rotationsenergie decreases.

With the solidification temperature in such a way specified the distance becomes so small that itself the smallestParticles mutually block and strengthened with one another attractively interact - they take a firm position in a three-dimensional lattice.

evaporation and sublimation
Aggregatzustände schematisch
of states of aggregation schematically

the speed of the smallest particles are not alike. A part is faster, inPart is slower than the average. The particles constantly change their current speed by collisions.

At the border of a solid body or a liquid, it can seem to the transition of a phase to a gaseous every now and then that a particle of itsCoincidentally a so strong impulse it gets neighbours that he escapes from the sphere of influence of the Kohäsionskraft.

This particle crosses then into the gaseous condition, and carries something heat energy forward in form of the kinetic energy, i.e. the firm or liquid phasea little cools down.

If the sublimation or boiling temperature is reached, this procedure happens continuously, until all smallest particles went over into the gaseous phase.

In this case the temperature in the evaporating phase remains usually unchanged, because allParticles with a higher temperature from the system disappear. The heat supply is thus converted into an increase of the entropy.

If particles change from a state of aggregation into another, they take up more energy, than with the normal increase of the temperature (see Evaporate). Therefore between evaporation and simmering one differentiates.

If the Kohäsionskräfte are very strong, and/or it itself actually around much stronger metal - or electrovalence acts, then it does not come to the evaporation.

condensation and Resublimation

The reverse procedure is the condensation and/or Resublimation. A smallest particle meets coincidentally a solid or liquid substance, transfers its impulse and by the Kohäsionskräften is held.

Thus the body warms up around the energy, those the smallest particlemore carried, than the average of the smallest particles in the firm and/or liquid phase.

If the particle comes however from a material, which is gaseous at this temperature, the Kohäsionskräfte are too weak to hold it. Even if it coincidentally somuch energy lost that it is bound, hurls it the next collision with neighbouring smallest particles again into the gaseous phase.

By lowering the temperature one can extract their energy from the smallest particles.

Thus they clump when falling below thatSublimation or solidification temperature by the reciprocal effect forces with other particles together and forms again a solid or a liquid.

phase diagrams

major items: Phase diagram

phase diagram one „usual “material and the water (anomaly of density)

p-T-phase diagram of a material describes itsState of aggregation and/or phase as a function of pressure and temperature. On the basis the lines one can recognize thus, at which pressure and which temperature the materials its state of aggregation to change. One can say thus, on the lines finds the transition between the states of aggregationinstead of, why one calls these also phase boundary lines. On them the respective states of aggregation in form of a dynamic equilibrium are present next to each other.

From a phase diagram one in addition the following can recognize:

  • At a certain pressure and a certain temperature, soTripelpunkt mentioned, can be present all three states of aggregation at the same time. It concerns thereby the point in „the center “of the phase diagram, at which all three phase boundary lines meet. The Tripelpunkt is suitable therefore as a starting point of these lines and forthe definition of many temperature scales.
  • Above a certain pressure and a certain temperature, the critical point in such a way specified, gas and liquid cannot be differentiated due to its identical density no more. In this Zustandsraum therefore no phase boundary line can be specified.
  • For pressures below the Tripelpunkt pressure the substance can become only gaseous with a lowering of the temperature only firmly or with an increase of the temperature. One calls the dividing line between both ranges sublimation curve. On it firm and gaseous phases can at the same time exist. The sublimation curve begins theoretically at the absolute zero and ends at the Tripelpunkt.
  • For pressures above the Tripelpunkt pressure the substance for temperatures is firmly, between bloom and boiling point liquid and above the boiling point gaseous below the melting point. The dividing line betweenfirm and liquid phase, thus, one calls the curve of the melting points fusion curve, the dividing line between liquid and gas calls one boiling point curve. Both curves begin likewise at the Tripelpunkt, whereby the fusion curve continues theoretically into the infinite andthe boiling point curve at the critical point ends.
  • The degrees of freedom within the phase diagram depend on the regarded level. At the Tripelpunkt and at the critical point no degree of freedom, there both to pressure and temperature firm, exists values only dependent on material possesses. At the phase boundary lineseither pressure or temperature therefore is freely selectable and causes itself each other, it exists a degree of freedom. In the pure Zustandsraum, thus in the surfaces of the phase diagram, pressure and temperature are freely selectable, which corresponds to two degrees of freedom.
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to mixtures of states of aggregation

in → solid liquid gas solid
alloy , conglomerate suspension , suspended matters , mud , colloid smoke , aerosol liquid
gel , wet sponge emulsion , dispersion fog ↓gemischt, Aerosol
gas expanded polystyrene foam gas mixture

non--classical states of aggregation

apart from the three classical states of aggregation gives it further, only under extreme conditions arises (according to temperature, from low to high, sorts):

  • The Bose Einstein condensate: Here it acts overa quantity of extremely cold atoms, which take the same quantum-mechanical condition, thus indistinguishably, thus perfectly coherently behave. Quasi an atomic heap, which behaves like an enormous atom.
  • Superfluid: Is still liquid in certain sense than liquid. Itno internal friction gives more, i.e. internal currents do not stop no more in the course of the time.
  • Atomic gas: In it no more molecules exist, since the constant impacts destroy the connections, however are still firmly bound the electrons.
  • That Plasma condition: It arises in suns or in fusion reactors . At very high temperatures the atoms in atomic nucleus become and - covering divides, free electrons to develop.
  • Sometimes the vacuum is called state of aggregation.

It pay attention that plasma and vacuum noneactual states of aggregation are. Reason for it is that there are no phase transitions, which define these conditions. An apparent contrast to the classical states of aggregation is with the so-called.Chandrall polymers forwards, which are firm at room temperature and become liquid with increasing cold weather (negativeAggregation). It concerns here however not an actual reversal of the states of aggregation, but rather around a utilization of the different densities of different materials used in the polymer.


a gaseous condition, in that free electrons andif ionized atoms occur, one calls plasma.

This condition can be achieved at high temperatures (thermal decay), but for example also by strong electrical fields (lightning, halogen bulb). At high temperatures (~ 5000 K) gas almost disintegratescompletely into a plasma, in addition, at low temperatures free electrons and ionized atoms (also in solids or liquids) occur as can be prove.

There is therefore no phase transition to the plasma.Therefore is also disputed whether a plasma at all its own state of aggregationis. The plasma is produced not by a phase transition from the gas, as for instance water from ice, but by reaction, i.e. the decay of a neutral atom in an ion and an electron. It knows itself then an equilibrium betweenneutral atoms and ions adjust, which is described by the so-called Saha equation.

At ever higher temperatures even the atomic nuclei can be completely opened, which for the nuclear fusion is interesting.

In principle a plasma behaves however like a gas, only alsoElectrons and cations or atomic nuclei as smallest particles. Thus the plasma is a good electrical conductor.

Bose Einstein condensate (“BEC”)

BEC can be achieved only at extremely low temperatures close to the absolute zero. The individual atoms lose thereby theirAnd function to identity completely synchronously, similarly a trained company of guard soldiers with a parade. Therefore these particles are called also troop of atoms in the BEC, which only one quantum state too own to have. But center contrary to the guard soldiersitself these atoms around one point to a kind atomic lump - they are all at the same time at the same place and become thus completely identical. Most diverse basicphysical phenomena can be observed in such a way. The characteristics of the atoms here developing havemuch with the theory of the ideal gas commonly. The atoms in the BEC have a further interesting characteristic, i.e. that they interact hardly with one another. The temperatures needed for it are reached by the laser cooling.

The BEC is not simple to prove and/ make visible, the applied method is comparatively simple: The shade of the atoms in the condensate is thrown on the lens of a digital camera and (something indistinct ones) the result shows a kind “atomic Tornado”, which consolidates itself fast.

fermion condensate

fermion condensatesimilarly the BEC, however not for bosons, but for fermions [

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