State of aggregation of matter

This diagram shows the nomenclature for different phase transitions, its reversibility and relation to the variation of the entalpia.

In physics and chemistry it is observed that, for any substance or mixture, by changing its temperature or pressure, different states or phases can be obtained, called states of aggregation of matter, in relation to the forces of union of the particles (molecules, atoms or ions) that constitute it.

All aggregation states have different properties and characteristics; the best known and most commonly observable are four, called solid, liquid, gas and plasma phases. Other states that do not occur naturally in our environment are also possible, for example: Bose-Einstein condensate, fermionic condensate and neutron stars. Others, such as quark-gluon plasma, are thought to be possible as well.

The term "phase" is sometimes used synonymously with state of matter, but a system may contain several "immiscible" phases of the same state of matter.

Conventional states dependent on pressure and temperature

Solid State

A crystalline solid: atomic resolution image of strontium titanate. The brightest atoms are strontium and the darkest are titanium.

Solid-state objects appear as bodies of definite shape; their atoms often interlock into tight, defined structures, giving them the ability to withstand forces without apparent deformation. They are generally classified as hard as well as resistant, and in them the forces of attraction are greater than those of repulsion. In crystalline solids, the presence of small intermolecular spaces gives way to the intervention of bonding forces, which locate the cells in geometric shapes. In the amorphous or vitreous, on the contrary, the particles that constitute them lack an ordered structure.

Substances in a solid state usually have some of the following characteristics:

• High cohesion.
• They have a definite shape and form memory.
• For practical purposes, they are incompressible.
• Resistance to fragmentation.
• They don't have fluidity
• Constant volume
• Some of them are subdued.

In crystalline solids, the particles (atoms, molecules, or ions) are packed in a regularly ordered, repeating pattern. There are several different crystal structures, and the same substance can have more than one structure (or solid phase). For example, iron has a body-centered cubic structure at temperatures below 912 °C (1,674 °F), and a face-centered cubic structure between 912 and 1,394 °C (2,541 °F). Ice has fifteen known crystal structures, or fifteen solid phases, that exist at various temperatures and pressures.

Glass and other non-crystalline and amorphous solids without long-range order are not basic states of thermal equilibrium, so they are described below as “non-classical states of matter”.

Solids can be made into liquids by melting, and liquids can be made into solids by solidification. Solids can also be transformed directly into gases through the process of sublimation, and gases can also be directly transformed into solids through deposition.

Liquid state

Structure of a classic monoatomic liquid. Atoms have many closest neighbors in contact, but there is no far-reaching order.

If the temperature of a solid is increased, it loses shape until the crystalline structure disappears, reaching the liquid state. Main feature: the ability to flow and adapt to the shape of the container that contains it. In this case, there is still some union between the atoms of the body, although much less intense than in solids. The liquid state presents the following characteristics:

• Less cohesion.
• They have a kinetic energy movement.
• They are fluids, they have no definite form, nor form memory so they take the shape of the surface or the container that contains it.
• It usually changes to solid state in the cold
• It has fluidity through small holes.
• You can present diffusion.
• They're uncomprehensible.

Gas state

The spaces between the gas molecules are very large. Gas molecules have very weak or null links. The "gas" molecules can move freely and quickly.

Gas is the state of aggregation of matter composed mainly of unbound, expanded molecules with little attractive force, which means that gases do not have a defined volume or defined shape, and expand freely until they fill the container that contains them. Its density is much less than that of liquids and solids, and the gravitational and attractive forces between its molecules are negligible. In some dictionaries the term gas is considered a synonym of steam, although the concepts should not be confused: steam refers strictly to that gas that can be condensed by pressurization at constant temperature.

Depending on its energy content or the forces that act, matter can be in one state or in a different one: there has been talk throughout history of an ideal gas or a perfect crystalline solid, but both are models ideal limits and therefore have no real existence.

In a gas, the molecules are in a state of chaos and show little response to gravity. They move so fast that they break free of each other. They then occupy a much larger volume than in the other states because they leave intermediate free spaces and are enormously separated from each other. That is why it is so easy to compress a gas, which means, in this case, to decrease the distance between molecules. The gas lacks shape and volume, because it is understood that where it has free space, its wandering molecules will go there and the gas will expand until it completely fills any container.

At temperatures below its critical temperature, a gas is also called a vapor and can be liquefied only by compression without the need for refrigeration. A vapor can exist in equilibrium with a liquid (or solid), in which case the pressure of the gas is equal to the vapor pressure of the liquid (or solid).

A supercritical fluid (SCF) is a gas whose temperature and pressure are above the critical temperature and pressure, respectively. In this state, the distinction between liquid and gas disappears. A supercritical fluid has the physical properties of a gas, but its high density gives it solvent properties in some cases, leading to useful applications. For example, supercritical carbon dioxide is used to extract caffeine in the manufacture of decaffeinated coffee.

Plasma status

In a plasma, electrons depart from their cores, forming a "mar" of electrons. This gives you the ability to drive electricity.

Plasma is an ionized gas, that is, the atoms that compose it have separated from some of their electrons. In this way, plasma is a state similar to gas but made up of anions and cations (ions with a negative and positive charge, respectively), separated from each other and free, which is why it is an excellent conductor. A very clear example is the Sun.

In Earth's lower atmosphere, any atom that loses an electron (when hit by a fast cosmic particle) is said to be ionized. But at high temperatures it is very different. The hotter the gas, the faster its molecules and atoms move (ideal gas law) and at very high temperatures the collisions between these fast-moving atoms are violent enough to free the electrons. In the solar atmosphere, a large part of the atoms are permanently "ionized" by these collisions, and the gas behaves like a plasma.

Unlike cold gases (for example, air at room temperature), plasmas conduct electricity and are strongly influenced by magnetic fields. The fluorescent lamp contains plasma (its main component is mercury vapor) that heats and agitates electricity, through the line of force to which the lamp is connected. The line, electrically positive at one end and negative at the other, causes positive ions to accelerate toward the negative end, and negative electrons to go toward the positive end. The accelerated particles gain energy, collide with atoms, eject extra electrons, and maintain the plasma, even as particles recombine. The collisions also cause the atoms to emit light, and this form of light is more efficient than traditional lamps. Neon signs and street lights work on a similar principle and were also used in electronics.

Ionosphere Profile

The upper part of the ionosphere extends into space for a few hundred kilometers and is combined with the magnetosphere, whose plasma is generally more rarefied and also hotter. The ions and electrons in the plasma of the magnetosphere come from the ionosphere below and from the solar wind, and many of the details of their input and heating are not yet clear.

There is interplanetary plasma, the solar wind. The Sun's outermost layer, the corona, is so hot that not only are all its atoms ionized, but those who started a theory with many electrons have most (sometimes all) ripped out, including the electrons in the outermost layers. deep that are more strongly united. Electromagnetic radiation characteristic of iron, which has lost 13 electrons, has been detected in the Sun's corona.

This extreme temperature prevents the coronal plasma from being held captive by solar gravity and thus flows in all directions, filling the Solar System beyond the most distant planets.

Properties of plasma

There are 2 types of plasma, cold and hot:

• In cold plasmas, atoms are at room temperature and are the electrons that accelerate to reach a temperature of 5000 °C. But as the ions, which are much more massive, are at room temperature, do not burn when touching them.
• In hot plasmas, ionization occurs by shocks of atoms among themselves What it does is to heat a gas a lot and by the shocks of atoms themselves ionize. These same ionized atoms also capture electrons and in that process light is generated (that is why the Sun shines, and the fire shines, and the plasmas of the laboratories shine).

Quantum Condensates

Bose-Einstein Condensate

This new form of matter was obtained on July 5, 1995 by physicists Eric A. Cornell, Wolfgang Ketterle, and Carl E. Wieman, for which they were awarded the 2001 Nobel Prize in Physics. The scientists managed to cool the atoms to a temperature 300 times lower than had been previously achieved. It has been called "BEC, Bose - Einstein Condensed" and it is so cold and dense that they ensure that the atoms can remain immobile. It is not yet known what will be the best use that can be given to this discovery. This state was predicted by Satyendra Nath Bose and Albert Einstein in 1927.

Fermi condensate

Created at the University of Colorado for the first time in 1999, the first Fermi condensate made up of atoms was created in 2003. The fermionic condensate, considered the sixth state of matter, is a superfluid phase made up of fermionic particles at low temperatures. It is closely related to the Bose-Einstein condensate. Unlike Bose-Einstein condensates, fermion condensates are formed using fermions instead of bosons.

In other words, the Fermi condensate is a state of aggregation of matter in which matter becomes superfluid. It is created at very low temperatures, extremely close to absolute zero.

The first fermionic condensates described the state of electrons in a superconductor. The first atomic fermionic condensate was created by Deborah S. Jin in 2003. A chiral condensate is an example of a fermionic condensate that appears in massless fermion theories with chiral symmetry breaking.

Super Solid

This material is a solid in the sense that all of the helium-(4) atoms that make it up are frozen in a rigid crystalline film, similar to how atoms and molecules are in a solid. normal as ice The difference is that, in this case, “frozen” does not mean “stationary”.

Because the helium-4 particle is so cold (just a tenth of a degree above absolute zero), the laws of quantum uncertainty begin to take over. In effect, helium atoms begin to behave as if they were solid and fluid at the same time. In fact, under the right circumstances, a fraction of the helium atoms begin to move across the film as a substance known as a "superfluid," a liquid that moves without any friction. Hence its name "supersolid".

It is shown that helium particles applied at temperatures close to absolute 0 change the moment of inertia and a solid becomes a supersolid, which previously appears as a state of matter.

High energy states

Degenerate matter

Under extremely high pressure, such as in the cores of dead stars, ordinary matter undergoes a transition to a series of exotic states of matter known collectively as degenerate matter, which rely primarily on quantum mechanical effects. In physics, the term "degenerate" refers to two states that have the same energy and are therefore interchangeable. Degenerate matter relies on the Pauli exclusion principle, which prevents two fermionic particles from occupying the same quantum state. Unlike normal plasma, degenerate plasma expands little when heated, because there are simply no momentum states left. Consequently, degenerate stars collapse to very high densities. The most massive degenerate stars are smaller, because the gravitational force increases, but the pressure does not increase proportionally.

Electron degenerate matter is found inside white dwarf stars. The electrons remain bound to the atoms, but can be transferred to adjacent atoms. Matter degenerate into neutrons is found in neutron stars. The enormous gravitational pressure squeezes the atoms so tightly that the electrons are forced to combine with the protons via inverse beta decay, resulting in a superdense neutron clump. Normally, free neutrons outside an atomic nucleus decay with a half-life of about 10 minutes, but in a neutron star, decay is outpaced by reverse decay. Cold degenerate matter is also present in planets such as Jupiter and even more massive brown dwarfs, which are expected to have a core with metallic hydrogen. Due to degeneracy, the most massive brown dwarfs are not significantly larger. In metals, electrons can be modeled as a degenerate gas moving in a lattice of non-degenerate positive ions.

The matter of quarks

In regular cold matter, quarks, fundamental particles of nuclear matter, are confined by the strong force in hadrons made up of 2-4 quarks, such as protons and neutrons. Quark matter or quantum chromodynamic matter (QCD) is a group of phases in which the strong force is overcome and the quarks remain unconfined and free to move. The matter phases of quarks occur at extremely high densities or temperatures, and there are no known ways to produce them in equilibrium in the laboratory; under ordinary conditions, any quark matter that forms immediately undergoes radioactive decay.

Strange matter is a type of quark matter suspected to exist within some neutron stars close to the Tolman-Oppenheimer-Volkoff limit (approximately 2-3 solar masses), although there is no direct evidence for its existence. In strange matter, some of the available energy manifests itself in the form of strange quarks, a heavier analogue of the common down quark. It is possible that, once formed, it is stable at lower energy states, although this is unknown.

Quark-gluon plasma is a very high-temperature phase in which quarks are freed and can move independently, rather than being perpetually bound together in particles, in a sea of gluons, subatomic particles that transmit the strong force that binds quarks. This is analogous to the release of electrons from atoms in a plasma. This state is reached briefly in collisions of very high-energy heavy ions in particle accelerators, and allows scientists to observe the properties of individual quarks, rather than just theorize. Quark-gluon plasma was discovered at CERN in 2000. Unlike plasma, which flows like a gas, the interactions within QGP are strong and it flows like a liquid.

At high densities, but at relatively low temperatures, quarks form a liquid of quarks whose nature is currently unknown. At even higher densities, it forms a distinct color and flavor blocking (CFL) phase. This phase is superconductive for color charging. These phases may occur in neutron stars, but are currently theoretical.

Stained glass condensate

Stained glass condensate is a type of matter theorized to exist in atomic nuclei traveling at close to the speed of light. According to Einstein's theory of relativity, a high-energy nucleus appears to have a contracted, or compressed, length along its direction of motion. As a result, the gluons within the nucleus appear to a stationary observer as a "gluon wall"; traveling close to the speed of light. At very high energies, the density of the gluons in this wall is seen to increase a lot. Unlike the quark-gluon plasma that occurs when these walls collide, the gluon condensate describes the walls themselves, and is an intrinsic property of particles that can only be observed under high-energy conditions like those at RHIC and possibly also in the «Large Hadron Collider».

Very high energy states

Several theories predict new states of matter at very high energies. An unknown state has created baryon asymmetry in the universe, but little is known about it. In string theory, a Hagedorn temperature for superstrings is predicted to be around 10³⁰ K, where they are produced copiously. At Planck's temperature (10³² K), gravity becomes a significant force between individual particles. No current theory can describe these states and they cannot be produced by any predictable experiment. However, these states are important in cosmology because the universe may have passed through them in the Big Bang.

The gravitational singularity that general relativity predicts exists at the center of a black hole is not a phase of matter; it is not a material object at all (although the mass-energy of matter contributed to its creation), but a property of space-time. Since spacetime breaks there, the singularity should not be considered a localized structure, but rather a global topological feature of spacetime. It has been argued that elementary particles are not fundamentally material either, but instead are localized properties of spacetime. time. In quantum gravity, singularities can indeed mark transitions to a new phase of matter.

Other possible states of matter

There are other possible states of matter; some of these only exist under extreme conditions, such as inside dead stars, or at the beginning of the universe after the Big Bang:

• Superfluid
• Degenerate matter
• Strongly symmetrical matter
• Weakly symmetrical matter
• Foreign matter or quarks matter
• Superfluid polaritón
• Fotonic Matter
• Quantum Spin Liquid
• Liquid crystal

Status changes

For each element or chemical compound there are certain conditions of pressure and temperature at which changes of state occur, and when reference is made only to the temperature of change of state, it must be interpreted that this refers to the pressure of the atm (atmospheric pressure). Thus, under "normal conditions" (atmospheric pressure, 0 °C) there are compounds in solid, liquid and gaseous states (S, L and G).

The processes in which a substance changes state are: sublimation (S-G), vaporization (L-G), condensation (G-L), solidification (L-S), melting (S-L), and reverse sublimation (G-S). It is important to clarify that these status changes have several names.

Types of state change

They are the processes in which one state of matter changes to another while maintaining a similarity in its composition. The different changes of state or phase transformations of matter are described below:

• Fusion: It is the passage of a solid to the liquid state through heat; during this endothermal process (process that absorbs energy to carry out this change) there is a point where the temperature remains constant. The "melting point" is the temperature at which the solid melts, so its value is particular for each substance. Such molecules will move in an independent form, transforming into a liquid. An example could be a melting ice, as it passes from solid state to liquid.

• Solidification: It is the passage from a liquid to solid through cooling; the process is exothermal. The "solidification point" or freezing point is the temperature at which the liquid is solidified and remains constant during the change, and it coincides with the melting point if performed slowly (reversible); its value is also specific.

• Vaporization and ebullition: They are the physical processes in which a liquid passes into a gaseous state. If it is done when the temperature of the entire liquid equals the boiling point of the liquid to that pressure by continuing to heat the liquid, it absorbs the heat, but without increasing the temperature: the heat is used in the conversion of the water in liquid state to that of water in gaseous state, until the entire mass passes to the gaseous state. At that time it is possible to increase the gas temperature.

• Condensation: It is called condensation to the change of state of matter that is passed in a liquid form. It is the reverse process of vaporization. If a gaseous state step is made directly solid, the process is called reverse sublimation. If a liquid to solid state step occurs, it is called solidification.

• Sublimation: It is the process that consists of changing the state of solid matter to the gaseous state without passing through the liquid state. A classic example of substance capable of sublimating is dry ice.

• Reverse sublimation: It is the direct step of the gaseous state to the solid state.

• Desion: It's the change of a gas plasma.

• Ionization: It's the change of a gas to a plasma.

It is important to note that in all phase transformations of substances, they are not transformed into other substances, only their physical state changes.

State changes are generally divided into two types: forward and backward.

• Progressive changes: Vaporization, fusion and progressive sublimation.
• Regressive changes: Condensation, solidification and regressive sublimation.

The following table indicates how the state changes are called: