The state of aggregation of a substance is usually called its ability to maintain its shape and volume. An additional feature is the ways in which a substance passes from one state of aggregation to another. Based on this, three states of aggregation are distinguished: solid, liquid and gas. Their visible properties are as follows:
A solid body retains both shape and volume. It can pass both into a liquid by melting, and directly into a gas by sublimation.
- Liquid - retains volume, but not shape, that is, it has fluidity. The spilled liquid tends to spread indefinitely over the surface onto which it is poured. A liquid can pass into a solid by crystallization, and into a gas by evaporation.
- Gas - does not retain either shape or volume. Gas outside of any container tends to expand indefinitely in all directions. Only gravity can prevent him from doing this, thanks to which the earth's atmosphere does not dissipate into space. A gas passes into a liquid by condensation, and directly into a solid can pass through precipitation.
Phase transitions
The transition of a substance from one state of aggregation to another is called a phase transition, since the scientific state of aggregation is a phase of matter. For example, water can exist in a solid phase (ice), liquid (ordinary water) and gaseous (steam).
The example of water is also well demonstrated. What is hung out in the yard to dry on a frosty windless day immediately freezes, but after a while it turns out to be dry: the ice sublimates, directly turning into water vapor.
As a rule, the phase transition from a solid to a liquid and gas requires heating, but the temperature of the medium does not increase: the thermal energy is spent on breaking the internal bonds in the substance. This is the so-called latent heat. During reverse phase transitions (condensation, crystallization), this heat is released.
That is why steam burns are so dangerous. When it comes into contact with the skin, it condenses. The latent heat of evaporation/condensation of water is very high: in this respect, water is an anomalous substance; That is why life on Earth is possible. During a steam burn, the latent heat of water condensation "scalds" the burnt place very deeply, and the consequences of a steam burn are much more severe than from a flame on the same area of the body.
Pseudophases
The fluidity of the liquid phase of a substance is determined by its viscosity, and the viscosity is determined by the nature of internal bonds, to which the next section is devoted. The viscosity of a liquid can be very high, and such a liquid can flow imperceptibly to the eye.
The classic example is glass. It is not a solid, but a very viscous liquid. Please note that glass sheets in warehouses are never stored leaning obliquely against the wall. Within a few days they will sag under their own weight and become unusable.
Other examples of pseudo-solid bodies are shoe pitch and building bitumen. If you forget the angular piece of bitumen on the roof, over the summer it will spread into a cake and stick to the base. Pseudo-solid bodies can be distinguished from real ones by the nature of melting: the real ones either retain their shape until they spread at once (solder when soldering), or float, letting out puddles and streams (ice). And very viscous liquids gradually soften, like the same pitch or bitumen.
Extremely viscous liquids, the fluidity of which is not noticeable for many years and decades, are plastics. Their high ability to retain their shape is provided by the huge molecular weight of polymers, many thousands and millions of hydrogen atoms.
The structure of the phases of matter
In the gas phase, the molecules or atoms of a substance are very far apart, many times greater than the distance between them. They interact with each other occasionally and irregularly, only during collisions. The interaction itself is elastic: they collided like hard balls, and immediately scattered.
In a liquid, molecules/atoms constantly "feel" each other due to very weak bonds of a chemical nature. These bonds break all the time and are immediately restored again, the molecules of the liquid are constantly moving relative to each other, and therefore the liquid flows. But in order to turn it into a gas, you need to break all the bonds at once, and this requires a lot of energy, which is why the liquid retains its volume.
In this regard, water differs from other substances in that its molecules in a liquid are connected by so-called hydrogen bonds, which are quite strong. Therefore, water can be a liquid at a normal temperature for life. Many substances with a molecular weight tens and hundreds of times greater than that of water, under normal conditions, are gases, like at least ordinary household gas.
In a solid, all its molecules are firmly in place due to strong chemical bonds between them, forming a crystal lattice. Crystals of the correct form require special conditions for their growth and therefore are rarely found in nature. Most solids are conglomerates of small and tiny crystals - crystallites, firmly linked by forces of mechanical and electrical nature.
If the reader has seen, for example, a cracked semi-axle of a car or a cast-iron grate, then the grains of crystallites on the scrap are visible with a simple eye. And on fragments of broken porcelain or faience dishes, they can be observed under a magnifying glass.
Plasma
Physicists also distinguish the fourth aggregate state of matter - plasma. In plasma, electrons are torn off from atomic nuclei, and it is a mixture of electrically charged particles. Plasma can be very dense. For example, one cubic centimeter of plasma from the interior of white dwarf stars weighs tens and hundreds of tons.
Plasma is isolated into a separate state of aggregation because it actively interacts with electromagnetic fields due to the fact that its particles are charged. In free space, the plasma tends to expand, cooling down and turning into a gas. But under the influence of electromagnetic fields, it can retain its shape and volume outside the vessel, like a solid body. This property of plasma is used in thermonuclear power reactors - prototypes of power plants of the future.
State of aggregation- this is a state of matter in a certain range of temperatures and pressures, characterized by properties: the ability (solid body) or inability (liquid, gas) to maintain volume and shape; the presence or absence of long-range (solid) or short-range (liquid) order and other properties.
A substance can be in three states of aggregation: solid, liquid or gaseous, currently an additional plasma (ionic) state is distinguished.
AT gaseous state, the distance between atoms and molecules of a substance is large, the interaction forces are small, and the particles, moving randomly in space, have a large kinetic energy exceeding the potential energy. The material in the gaseous state has neither its shape nor volume. The gas fills all available space. This state is typical for substances with low density.
AT liquid state, only the short-range order of atoms or molecules is preserved, when separate sections with an ordered arrangement of atoms periodically appear in the volume of a substance, however, the mutual orientation of these sections is also absent. The short-range order is unstable and can either disappear or reappear under the action of thermal vibrations of atoms. The molecules of a liquid do not have a definite position, and at the same time, they do not have complete freedom of movement. The material in the liquid state does not have its own shape, it retains only volume. The liquid can occupy only a part of the volume of the vessel, but freely flow over the entire surface of the vessel. The liquid state is usually considered intermediate between a solid and a gas.
AT solid substance, the arrangement of atoms becomes strictly defined, regularly ordered, the interaction forces of particles are mutually balanced, so the bodies retain their shape and volume. The regularly ordered arrangement of atoms in space characterizes the crystalline state, the atoms form a crystal lattice.
Solids have an amorphous or crystalline structure. For amorphous Bodies are characterized only by a short-range order in the arrangement of atoms or molecules, a chaotic arrangement of atoms, molecules or ions in space. Examples of amorphous bodies are glass, pitch, and pitch, which appear to be in a solid state, although in reality they flow slowly, like a liquid. Amorphous bodies, unlike crystalline ones, do not have a definite melting point. Amorphous bodies occupy an intermediate position between crystalline solids and liquids.
Most solids have crystalline a structure that is characterized by an ordered arrangement of atoms or molecules in space. The crystal structure is characterized by a long-range order, when the elements of the structure are periodically repeated; there is no such regular repetition in the short-range order. A characteristic feature of a crystalline body is the ability to retain its shape. A sign of an ideal crystal, the model of which is a spatial lattice, is the property of symmetry. Symmetry is understood as the theoretical ability of the crystal lattice of a solid to be combined with itself when its points are mirrored from a certain plane, called the plane of symmetry. The symmetry of the external form reflects the symmetry of the internal structure of the crystal. For example, all metals have a crystalline structure, which are characterized by two types of symmetry: cubic and hexagonal.
In amorphous structures with a disordered distribution of atoms, the properties of the substance are the same in different directions, i.e. glassy (amorphous) substances are isotropic.
All crystals are characterized by anisotropy. In crystals, the distances between atoms are ordered, but the degree of order may be different in different directions, which leads to a difference in the properties of the crystal substance in different directions. The dependence of the properties of a crystal substance on the direction in its lattice is called anisotropy properties. Anisotropy manifests itself when measuring both physical and mechanical and other characteristics. There are properties (density, heat capacity) that do not depend on the direction in the crystal. Most of the characteristics depend on the choice of direction.
It is possible to measure the properties of objects that have a certain material volume: sizes - from a few millimeters to tens of centimeters. These objects with a structure identical to the crystal cell are called single crystals.
The anisotropy of properties is manifested in single crystals and is practically absent in a polycrystalline substance consisting of many small randomly oriented crystals. Therefore, polycrystalline substances are called quasi-isotropic.
Crystallization of polymers, whose molecules can be arranged in an orderly manner with the formation of supramolecular structures in the form of bundles, coils (globules), fibrils, etc., occurs in a certain temperature range. The complex structure of molecules and their aggregates determines the specific behavior of polymers upon heating. They cannot go into a liquid state with low viscosity, they do not have a gaseous state. In solid form, polymers can be in glassy, highly elastic and viscous states. Polymers with linear or branched molecules can change from one state to another with a change in temperature, which manifests itself in the process of deformation of the polymer. On fig. 9 shows the dependence of deformation on temperature.
Rice. 9 Thermomechanical curve of amorphous polymer: t c , t t, t p - glass transition temperature, fluidity and the beginning of chemical decomposition, respectively; I - III - zones of a glassy, highly elastic and viscous state, respectively; Δ l- deformation.
The spatial structure of the arrangement of molecules determines only the glassy state of the polymer. At low temperatures, all polymers deform elastically (Fig. 9, zone I). Above glass transition temperature t c an amorphous polymer with a linear structure passes into a highly elastic state ( zone II), and its deformation in the glassy and highly elastic states is reversible. Heating above pour point t t transforms the polymer into a viscous state ( zone III). The deformation of the polymer in the viscous state is irreversible. An amorphous polymer with a spatial (network, cross-linked) structure does not have a viscous state, the temperature region of the highly elastic state expands to the temperature of polymer decomposition t R. This behavior is typical for rubber-type materials.
The temperature of a substance in any aggregate state characterizes the average kinetic energy of its particles (atoms and molecules). These particles in bodies have mainly the kinetic energy of oscillatory motions relative to the center of equilibrium, where the energy is minimal. When a certain critical temperature is reached, the solid material loses its strength (stability) and melts, and the liquid turns into steam: it boils and evaporates. These critical temperatures are the melting and boiling points.
When a crystalline material is heated at a certain temperature, the molecules move so vigorously that the rigid bonds in the polymer are broken and the crystals are destroyed - they pass into a liquid state. The temperature at which crystals and liquid are in equilibrium is called the melting point of the crystal, or the solidification point of the liquid. For iodine, this temperature is 114 o C.
Each chemical element has its own melting point t pl separating the existence of a solid and a liquid, and the boiling point t kip, corresponding to the transition of liquid into gas. At these temperatures, the substances are in thermodynamic equilibrium. A change in the state of aggregation may be accompanied by a jump-like change in free energy, entropy, density, and others. physical quantities.
To describe the various states in physics uses a broader concept thermodynamic phase. Phenomena that describe transitions from one phase to another are called critical.
When heated, substances undergo phase transformations. When melted (1083 o C), copper turns into a liquid in which the atoms have only short-range order. At a pressure of 1 atm, copper boils at 2310 ° C and turns into gaseous copper with randomly arranged copper atoms. At the melting point, the pressures of the saturated vapor of the crystal and liquid are equal.
The material as a whole is a system.
System- a group of substances combined physical, chemical or mechanical interactions. phase called a homogeneous part of the system, separated from other parts physical interfaces (in cast iron: graphite + iron grains; in ice water: ice + water).Components systems are the various phases that make up a given system. System Components- these are substances that form all phases (components) of this system.
Materials consisting of two or more phases are dispersed systems . Disperse systems are divided into sols, whose behavior resembles the behavior of liquids, and gels with the characteristic properties of solids. In sols, the dispersion medium in which the substance is distributed is liquid; in gels, the solid phase predominates. Gels are semi-crystalline metal, concrete, a solution of gelatin in water at a low temperature (at a high temperature, gelatin turns into a sol). A hydrosol is a dispersion in water, an aerosol is a dispersion in air.
State diagrams.
In a thermodynamic system, each phase is characterized by parameters such as temperature T, concentration With and pressure R. To describe phase transformations, a single energy characteristic is used - the Gibbs free energy ΔG(thermodynamic potential).
Thermodynamics in the description of transformations is limited to consideration of the state of equilibrium. equilibrium state thermodynamic system is characterized by the invariance of thermodynamic parameters (temperature and concentration, as in technological processing R= const) in time and the absence of flows of energy and matter in it - with the constancy of external conditions. Phase balance- equilibrium state of a thermodynamic system consisting of two or more phases.
For the mathematical description of the equilibrium conditions of the system, there is phase rule given by Gibbs. It connects the number of phases (F) and components (K) in an equilibrium system with the variance of the system, i.e., the number of thermodynamic degrees of freedom (C).
The number of thermodynamic degrees of freedom (variance) of a system is the number of independent variables, both internal (chemical composition of phases) and external (temperature), which can be given various arbitrary (in a certain interval) values so that new phases do not appear and old phases do not disappear .
Gibbs phase rule equation:
C \u003d K - F + 1.
In accordance with this rule, in a system of two components (K = 2), the following degrees of freedom are possible:
For a single-phase state (F = 1) C = 2, i.e., you can change the temperature and concentration;
For a two-phase state (F = 2) C = 1, i.e., you can change only one external parameter (for example, temperature);
For a three-phase state, the number of degrees of freedom is zero, i.e., it is impossible to change the temperature without disturbing the equilibrium in the system (the system is invariant).
For example, for a pure metal (K = 1) during crystallization, when there are two phases (F = 2), the number of degrees of freedom is zero. This means that the crystallization temperature cannot be changed until the process ends and one phase remains - a solid crystal. After the end of crystallization (F = 1), the number of degrees of freedom is 1, so you can change the temperature, i.e., cool the solid without disturbing the equilibrium.
The behavior of systems depending on temperature and concentration is described by a state diagram. The state diagram of water is a system with one H 2 O component, so the largest number of phases that can simultaneously be in equilibrium is three (Fig. 10). These three phases are liquid, ice, steam. The number of degrees of freedom in this case is equal to zero, i.e. it is impossible to change either the pressure or the temperature so that none of the phases disappears. Ordinary ice, liquid water and water vapor can exist in equilibrium simultaneously only at a pressure of 0.61 kPa and a temperature of 0.0075°C. The point where the three phases coexist is called the triple point ( O).
Curve OS separates the regions of vapor and liquid and represents the dependence of the pressure of saturated water vapor on temperature. The OC curve shows those interrelated values of temperature and pressure at which liquid water and water vapor are in equilibrium with each other, therefore it is called the liquid-vapor equilibrium curve or the boiling curve.
Fig 10 Water state diagram
Curve OV separates the liquid region from the ice region. It is a solid-liquid equilibrium curve and is called the melting curve. This curve shows those interrelated pairs of temperatures and pressures at which ice and liquid water are in equilibrium.
Curve OA is called the sublimation curve and shows the interconnected pairs of pressure and temperature values at which ice and water vapor are in equilibrium.
A state diagram is a visual way of representing the regions of existence of various phases depending on external conditions, such as pressure and temperature. State diagrams are actively used in materials science at various technological stages of obtaining a product.
A liquid differs from a solid crystalline body by low values of viscosity (internal friction of molecules) and high values of fluidity (the reciprocal of viscosity). A liquid consists of many aggregates of molecules, within which the particles are arranged in a certain order, similar to the order in crystals. The nature of structural units and interparticle interaction determines the properties of the liquid. There are liquids: monoatomic (liquefied noble gases), molecular (water), ionic (molten salts), metallic (molten metals), liquid semiconductors. In most cases, a liquid is not only a state of aggregation, but also a thermodynamic (liquid) phase.
Liquid substances are most often solutions. Solution homogeneous, but not a chemically pure substance, consists of a solute and a solvent (examples of a solvent are water or organic solvents: dichloroethane, alcohol, carbon tetrachloride, etc.), therefore it is a mixture of substances. An example is a solution of alcohol in water. However, solutions are also mixtures of gaseous (for example, air) or solid (metal alloys) substances.
Upon cooling under conditions of a low rate of formation of crystallization centers and a strong increase in viscosity, a glassy state can occur. Glasses are isotropic solid materials obtained by supercooling molten inorganic and organic compounds.
Many substances are known whose transition from a crystalline state to an isotropic liquid occurs through an intermediate liquid-crystal state. It is characteristic of substances whose molecules are in the form of long rods (rods) with an asymmetric structure. Such phase transitions, accompanied by thermal effects, cause an abrupt change in mechanical, optical, dielectric, and other properties.
liquid crystals, like a liquid, can take the form of an elongated drop or the shape of a vessel, have high fluidity, and are capable of merging. They are widely used in various fields of science and technology. Their optical properties are highly dependent on small changes in external conditions. This feature is used in electro-optical devices. In particular, liquid crystals are used in the manufacture of electronic watches, visual equipment, etc.
Among the main states of aggregation is plasma- partially or fully ionized gas. According to the method of formation, two types of plasma are distinguished: thermal, which occurs when a gas is heated to high temperatures, and gaseous, which forms during electrical discharges in a gaseous medium.
Plasma-chemical processes have taken a firm place in a number of branches of technology. They are used for cutting and welding refractory metals, for the synthesis of various substances, they widely use plasma light sources, the use of plasma in thermonuclear power plants is promising, etc.
In everyday practice, one has to deal not separately with individual atoms, molecules and ions, but with real substances - an aggregate of a large number of particles. Depending on the nature of their interaction, four types of aggregate state are distinguished: solid, liquid, gaseous and plasma. A substance can transform from one state of aggregation to another as a result of a corresponding phase transition.
The presence of a substance in a particular state of aggregation is due to the forces acting between the particles, the distance between them and the features of their movement. Each state of aggregation is characterized by a set of certain properties.
Properties of substances depending on the state of aggregation:
| condition | property |
| gaseous |
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| liquid |
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| solid |
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In accordance with the degree of order in the system, each state of aggregation is characterized by its own ratio between the kinetic and potential energies of the particles. In solids, the potential predominates over the kinetic, since the particles occupy certain positions and only oscillate around them. For gases, there is an inverse relationship between potential and kinetic energies, as a consequence of the fact that gas molecules always move randomly, and there are almost no cohesive forces between them, so the gas occupies the entire volume. In the case of liquids, the kinetic and potential energies of the particles are approximately the same, a non-rigid bond acts between the particles, therefore fluidity and a constant volume are inherent in liquids.
When the particles of a substance form a regular geometric structure, and the energy of bonds between them is greater than the energy of thermal vibrations, which prevents the destruction of the existing structure, it means that the substance is in a solid state. But starting from a certain temperature, the energy of thermal vibrations exceeds the energy of bonds between particles. In this case, the particles, although they remain in contact, move relative to each other. As a result, the geometric structure is broken and the substance passes into a liquid state. If the thermal fluctuations increase so much that the connection between the particles is practically lost, the substance acquires a gaseous state. In an "ideal" gas, particles move freely in all directions.
When the temperature rises, the substance passes from an ordered state (solid) to a disordered state (gaseous); the liquid state is intermediate in terms of the ordering of particles.
The fourth state of aggregation is called plasma - a gas consisting of a mixture of neutral and ionized particles and electrons. Plasma is formed at ultrahigh temperatures (10 5 -10 7 0 C) due to the significant collision energy of particles that have the maximum disorder of motion. A mandatory feature of plasma, as well as other states of matter, is its electrical neutrality. But as a result of the disordered motion of particles in the plasma, separate charged microzones can appear, due to which it becomes a source of electromagnetic radiation. In the plasma state, there is matter on, stars, other space objects, as well as in thermonuclear processes.
Each state of aggregation is determined primarily by the range of temperatures and pressures, therefore, for a visual quantitative characteristic, a phase diagram of a substance is used, which shows the dependence of the state of aggregation on pressure and temperature.
Diagram of the state of matter with phase transition curves: 1 - melting-crystallization, 2 - boiling-condensation, 3 - sublimation-desublimation
The state diagram consists of three main areas, which correspond to the crystalline, liquid and gaseous states. Individual regions are separated by curves reflecting phase transitions:
- solid to liquid and vice versa, liquid to solid (melting-crystallization curve - dotted green graph)
- liquid to gaseous and reverse conversion of gas to liquid (boiling-condensation curve - blue graph)
- solid to gaseous and gaseous to solid (sublimation-desublimation curve - red graph).
The coordinates of the intersection of these curves are called the triple point, in which, under conditions of a certain pressure P \u003d P in and a certain temperature T \u003d T in, a substance can coexist in three states of aggregation at once, and the liquid and solid states have the same vapor pressure. The coordinates Pv and Tv are the only values of pressure and temperature at which all three phases can coexist simultaneously.
The point K on the phase diagram of the state corresponds to the temperature T k - the so-called critical temperature, at which the kinetic energy of the particles exceeds the energy of their interaction and therefore the line of separation between the liquid and gas phases is erased, and the substance exists in the gaseous state at any pressure.
It follows from the analysis of the phase diagram that at a high pressure greater than at the triple point (P c), the heating of a solid ends with its melting, for example, at P 1, melting occurs at the point d. A further increase in temperature from T d to T e leads to the boiling of the substance at a given pressure P 1 . At a pressure Р 2 less than the pressure at the triple point Р в, heating the substance leads to its transition directly from the crystalline to the gaseous state (point q), that is, to sublimation. For most substances, the pressure at the triple point is lower than the saturation vapor pressure (P in
P saturated steam, therefore, when the crystals of such substances are heated, they do not melt, but evaporate, that is, they undergo sublimation. For example, iodine crystals or "dry ice" (solid CO 2) behave this way.
State Diagram Analysis gaseous state
Under normal conditions (273 K, 101325 Pa), both simple substances, the molecules of which consist of one (He, Ne, Ar) or several simple atoms (H 2, N 2, O 2), and complex substances with a low molar mass (CH 4, HCl, C 2 H 6).
Since the kinetic energy of gas particles exceeds their potential energy, the molecules in the gaseous state are constantly moving randomly. Due to the large distances between the particles, the forces of intermolecular interaction in gases are so small that they are not enough to attract particles to each other and keep them together. It is for this reason that gases do not have their own shape and are characterized by low density and high ability to compress and expand. Therefore, the gas constantly presses on the walls of the vessel in which it is located, equally in all directions.
To study the relationship between the most important gas parameters (pressure P, temperature T, amount of substance n, molar mass M, mass m), the simplest model of the gaseous state of matter is used - ideal gas, which is based on the following assumptions:
- the interaction between gas particles can be neglected;
- the particles themselves are material points that do not have their own size.
The most general equation describing the ideal gas model is considered to be the equations Mendeleev-Clapeyron for one mole of a substance:
However, the behavior of a real gas differs, as a rule, from the ideal one. This is explained, firstly, by the fact that between the molecules of a real gas there are still insignificant forces of mutual attraction that compress the gas to a certain extent. With this in mind, the total gas pressure increases by the value a/v2, which takes into account the additional internal pressure due to the mutual attraction of molecules. As a result, the total gas pressure is expressed by the sum P+ a/v2. Secondly, the molecules of a real gas have, albeit a small, but quite definite volume b , so the actual volume of all gas in space is V- b . When substituting the considered values into the Mendeleev-Clapeyron equation, we obtain the equation of state of a real gas, which is called van der Waals equation:
where a and b are empirical coefficients that are determined in practice for each real gas. It is established that the coefficient a has a large value for gases that are easily liquefied (for example, CO 2, NH 3), and the coefficient b - on the contrary, the higher in size, the larger the gas molecules (for example, gaseous hydrocarbons).
The van der Waals equation describes the behavior of a real gas much more accurately than the Mendeleev-Clapeyron equation, which, nevertheless, is widely used in practical calculations due to its clear physical meaning. Although the ideal state of a gas is a limiting, imaginary case, the simplicity of the laws that correspond to it, the possibility of their application to describe the properties of many gases at low pressures and high temperatures, makes the ideal gas model very convenient.
Liquid state of matter
The liquid state of any particular substance is thermodynamically stable in a certain range of temperatures and pressures characteristic of the nature (composition) of the substance. The upper temperature limit of the liquid state is the boiling point above which a substance under conditions of stable pressure is in a gaseous state. The lower limit of the stable state of the existence of a liquid is the temperature of crystallization (solidification). Boiling and crystallization temperatures measured at a pressure of 101.3 kPa are called normal.
For ordinary liquids, isotropy is inherent - the uniformity of physical properties in all directions within the substance. Sometimes other terms are also used for isotropy: invariance, symmetry with respect to the choice of direction.
In the formation of views on the nature of the liquid state, the concept of the critical state, which was discovered by Mendeleev (1860), is of great importance:
A critical state is an equilibrium state in which the separation limit between a liquid and its vapor disappears, since the liquid and its saturated vapor acquire the same physical properties.
In the critical state, the values of both densities and specific volumes of the liquid and its saturated vapor become the same.
The liquid state of matter is intermediate between gaseous and solid. Some properties bring the liquid state closer to the solid. If solids are characterized by a rigid ordering of particles, which extends over a distance of hundreds of thousands of interatomic or intermolecular radii, then in the liquid state, as a rule, no more than a few tens of ordered particles are observed. This is explained by the fact that orderliness between particles in different places of a liquid substance quickly arises, and is just as quickly “blurred” again by thermal vibrations of particles. At the same time, the overall density of the “packing” of particles differs little from that of a solid, so the density of liquids does not differ much from the density of most solids. In addition, the ability of liquids to compress is almost as small as in solids (about 20,000 times less than that of gases).
Structural analysis confirmed that the so-called short range order, which means that the number of nearest "neighbors" of each molecule and their mutual arrangement are approximately the same throughout the volume.
A relatively small number of particles of different composition, connected by forces of intermolecular interaction, is called cluster . If all particles in a liquid are the same, then such a cluster is called associate . It is in clusters and associates that short-range order is observed.
The degree of order in various liquids depends on temperature. At low temperatures slightly above the melting point, the degree of order in the placement of particles is very high. As the temperature rises, it decreases and, as the temperature rises, the properties of the liquid approach the properties of gases more and more, and when the critical temperature is reached, the difference between the liquid and gaseous states disappears.
The proximity of the liquid state to the solid state is confirmed by the values of the standard enthalpies of vaporization DH 0 of evaporation and melting DH 0 of melting. Recall that the value of DH 0 evaporation shows the amount of heat that is needed to convert 1 mole of liquid into vapor at 101.3 kPa; the same amount of heat is spent on the condensation of 1 mole of vapor into a liquid under the same conditions (i.e. DH 0 evaporation = DH 0 condensation). The amount of heat required to convert 1 mole of a solid to a liquid at 101.3 kPa is called standard enthalpy of fusion; the same amount of heat is released during the crystallization of 1 mole of liquid under normal pressure conditions (DH 0 melting = DH 0 crystallization). It is known that DH 0 evaporation<< DН 0 плавления, поскольку переход из твердого состояния в жидкое сопровождается меньшим нарушением межмолекулярного притяжения, чем переход из жидкого в газообразное состояние.
However, other important properties of liquids are more like those of gases. So, like gases, liquids can flow - this property is called fluidity . They can resist the flow, that is, they are inherent viscosity . These properties are influenced by attractive forces between molecules, the molecular weight of the liquid substance, and other factors. The viscosity of liquids is about 100 times greater than that of gases. Just like gases, liquids can diffuse, but at a much slower rate because liquid particles are packed more densely than gas particles.
One of the most interesting properties of the liquid state, which is not characteristic of either gases or solids, is surface tension .
Diagram of the surface tension of a liquid A molecule located in a liquid volume is uniformly acted upon by intermolecular forces from all sides. However, on the surface of the liquid, the balance of these forces is disturbed, as a result of which the surface molecules are under the action of some resultant force, which is directed inside the liquid. For this reason, the liquid surface is in a state of tension. Surface tension is the minimum force that keeps the particles of a liquid inside and thereby prevents the surface of the liquid from contracting.
Structure and properties of solids
Most of the known substances, both natural and artificial, are in the solid state under normal conditions. Of all the compounds known today, about 95% are solids, which have become important, since they are the basis of not only structural, but also functional materials.
- Structural materials are solids or their compositions that are used to make tools, household items, and various other structures.
- Functional materials are solids, the use of which is due to the presence of certain useful properties in them.
For example, steel, aluminum, concrete, ceramics belong to structural materials, and semiconductors, phosphors belong to functional ones.
In the solid state, the distances between the particles of matter are small and have the same order of magnitude as the particles themselves. The interaction energies between them are large enough, which prevents the free movement of particles - they can only oscillate about certain equilibrium positions, for example, around the nodes of the crystal lattice. The inability of particles to move freely leads to one of the most characteristic features of solids - the presence of their own shape and volume. The ability to compress solids is very small, and the density is high and little dependent on temperature changes. All processes occurring in solid matter occur slowly. The laws of stoichiometry for solids have a different and, as a rule, broader meaning than for gaseous and liquid substances.
The detailed description of solids is too voluminous for this material and is therefore covered in separate articles:, and.
Definition
Aggregate states of matter (from the Latin aggrego - attach, connect) - these are the states of the same substance - solid, liquid, gaseous.
During the transition from one state to another, an abrupt change in energy, entropy, density and other characteristics of matter occurs.
Solid and liquid bodies
Definition
Solid bodies are bodies that are distinguished by the constancy of shape and volume.
In them, the intermolecular distances are small and the potential energy of the molecules is comparable to the kinetic one. Solids are divided into two types: crystalline and amorphous. Only crystalline bodies are in a state of thermodynamic equilibrium. Amorphous bodies, in fact, represent metastable states, which in their structure approach non-equilibrium, slowly crystallizing liquids. In an amorphous body, a very slow process of crystallization takes place, the process of a gradual transition of a substance into a crystalline phase. The difference between a crystal and an amorphous solid lies primarily in the anisotropy of its properties. The properties of a crystalline body depend on the direction in space. Various kinds of processes, such as thermal conductivity, electrical conductivity, light, sound, propagate in different directions of a solid body in different ways. Amorphous bodies (glass, resins, plastics) are isotopic, like liquids. The only difference between amorphous bodies and liquids is that the latter are fluid, static shear deformations are impossible in them.
Crystalline bodies have the correct molecular structure. The anisotropy of its properties is due to the correct structure of the crystal. The correct arrangement of the atoms of a crystal forms the so-called crystal lattice. In different directions, the arrangement of atoms in the lattice is different, which leads to anisotropy. Atoms (or ions, or whole molecules) in the crystal lattice perform random oscillatory motion around the middle positions, which are considered as nodes of the crystal lattice. The higher the temperature, the greater the energy of oscillations, and hence the average amplitude of oscillations. The size of the crystal depends on the amplitude of the oscillations. An increase in the amplitude of oscillations leads to an increase in the size of the body. This explains the thermal expansion of solids.
Definition
Liquid bodies are bodies that have a certain volume, but do not have elasticity of form.
Liquids are characterized by strong intermolecular interaction and low compressibility. A liquid occupies an intermediate position between a solid and a gas. Liquids, like gases, are isotopic. In addition, the liquid has fluidity. In it, as in gases, there are no tangential stresses (shear stresses) of bodies. Liquids are heavy, i.e. their specific gravity is comparable to the specific gravity of solids. Near the crystallization temperatures, their heat capacities and other thermal characteristics are close to those of solids. In liquids, to a certain extent, the correct arrangement of atoms is observed, but only in small areas. Here the atoms also oscillate near the nodes of a quasi-crystalline cell, but unlike the atoms of a solid body, they jump from one node to another from time to time. As a result, the motion of atoms will be very complex: it is oscillatory, but at the same time the center of vibrations moves in space.
Gas, evaporation, condensation and melting
Definition
A gas is a state of matter in which the distances between molecules are large.
The forces of interaction between molecules at low pressures can be neglected. Gas particles fill the entire volume that is provided to the gas. Gases can be considered as highly superheated or unsaturated vapors. Plasma is a special type of gas - it is partially or completely ionized gas, in which the density of positive and negative charges is almost the same. Plasma is a gas of charged particles that interact with each other using electrical forces at a great distance, but do not have near and far particles.
Substances can change from one state of aggregation to another.
Definition
Evaporation is the process of changing the state of aggregation of a substance, in which molecules fly out from the surface of a liquid or solid, the kinetic energy of which exceeds the potential energy of the interaction of molecules.
Evaporation is a phase transition. During evaporation, part of the liquid or solid passes into vapor. A substance in a gaseous state that is in dynamic equilibrium with a liquid is called saturated vapor. In this case, the change in the internal energy of the body:
\[\triangle \ U=\pm mr\ \left(1\right),\]
where m is body weight, r is the specific heat of vaporization (J / kg).
Definition
Condensation is the reverse process of vaporization.
The calculation of the change in internal energy is carried out according to the formula (1).
Definition
Melting is the process of transition of a substance from a solid to a liquid state, the process of changing the state of aggregation of a substance.
When a substance is heated, its internal energy increases, therefore, the speed of thermal movement of molecules increases. In the event that the melting point of the substance is reached, the crystal lattice of the solid begins to break down. Bonds between particles are destroyed, the energy of interaction between particles increases. The heat transferred to the body goes to increase the internal energy of this body, and part of the energy goes to doing work to change the volume of the body when it melts. For most crystalline bodies, the volume increases when melted, but there are exceptions, for example, ice, cast iron. Amorphous bodies do not have a specific melting point. Melting is a phase transition, which is accompanied by an abrupt change in heat capacity at the melting temperature. The melting point depends on the substance and does not change during the process. In this case, the change in the internal energy of the body:
\[\triangle U=\pm m\lambda \left(2\right),\]
where $\lambda $ is the specific heat of fusion (J/kg).
The reverse process of melting is crystallization. The calculation of the change in internal energy is carried out according to the formula (2).
The change in the internal energy of each body of the system in the case of heating or cooling can be calculated by the formula:
\[\triangle U=mc\triangle T\left(3\right),\]
where c is the specific heat of the substance, J/(kgK), $\triangle T$ is the change in body temperature.
When studying the transitions of substances from one state of aggregation to another, it is impossible to do without the so-called heat balance equation, which says: the total amount of heat that is released in a thermally insulated system is equal to the amount of heat (total) that is absorbed in this system.
In its meaning, the heat balance equation is the law of conservation of energy for heat transfer processes in thermally insulated systems.
Example 1
Assignment: There are water and ice in a heat-insulated vessel at a temperature $t_i= 0^oС$. The masses of water ($m_(v\ ))$ and ice ($m_(i\ ))$ are 0.5 kg and 60 g respectively. Water vapor of mass $m_(p\ )=$10 g is let into the water. at temperature $t_p= 100^oС$. What will be the temperature of the water in the vessel after thermal equilibrium is established? The heat capacity of the vessel is ignored.
Solution: Let's determine what processes take place in the system, what aggregate states of matter we had and what we got.
Water vapor condenses, giving off heat.
This heat is used to melt the ice and, possibly, to heat the water available and obtained from the ice.
Let us first check how much heat is released during the condensation of the available mass of steam:
here, from reference materials, we have $r=2.26 10^6\frac(J)(kg)$ - specific heat of vaporization (also applicable for condensation).
Heat needed to melt ice:
here from reference materials we have $\lambda =3.3\cdot 10^5\frac(J)(kg)$ - specific heat of ice melting.
We get that the steam gives off more heat than required, only to melt the existing ice, therefore, we write the heat balance equation in the form:
Heat is released during condensation of steam with mass $m_(p\ )$ and cooling of water, which is formed from steam from temperature $T_p$ to the desired T. Heat is absorbed during melting of ice with mass $m_(i\ )$ and heating of water with mass $m_v+ m_i$ from temperature $T_i$ to $T.\ $ Denote $T-T_i=\triangle T$, for the difference $T_p-T$ we get:
The heat balance equation will take the form:
\ \ \[\triangle T=\frac(rm_(p\ )+cm_(p\ )100-lm_(i\ ))(c\left(m_v+m_i+m_(p\ )\right))\left (1.6\right)\]
We will carry out calculations, taking into account that the heat capacity of water is tabular $c=4.2\cdot 10^3\frac(J)(kgK)$, $T_p=t_p+273=373K,$ $T_i=t_i+273=273K$:
$\triangle T=\frac(2,26\cdot 10^6\cdot 10^(-2)+4,2\cdot 10^3\cdot 10^(-2)10^2-6\cdot 10^ (-2)\cdot 3,3\cdot 10^5)(4,2\cdot 10^3\cdot 5,7\cdot 10^(-1))\approx 3\left(K\right)$then T=273+3=276 (K)
Answer: The temperature of the water in the vessel after the establishment of thermal equilibrium will be equal to 276 K.
Example 2
Task: The figure shows the section of the isotherm corresponding to the transition of a substance from a crystalline to a liquid state. What corresponds to this section on the p,T diagram?
The entire set of states depicted on the p, V diagram by a horizontal straight line segment on the p, T diagram is depicted by one point that determines the values of p and T, at which the transition from one state of aggregation to another takes place.
The most widespread knowledge is about three states of aggregation: liquid, solid, gaseous, sometimes they think about plasma, less often liquid crystal. Recently, a list of 17 phases of matter, taken from the famous () Stephen Fry, has spread on the Internet. Therefore, we will talk about them in more detail, because. one should know a little more about matter, if only in order to better understand the processes taking place in the Universe.
The list of aggregate states of matter given below increases from the coldest states to the hottest, and so on. may be continued. At the same time, it should be understood that from the gaseous state (No. 11), the most “expanded”, on both sides of the list, the degree of compression of the substance and its pressure (with some reservations for such unexplored hypothetical states as quantum, ray, or weakly symmetric) increase. After the text a visual graph of the phase transitions of matter is given.
1. Quantum- the state of aggregation of matter, achieved when the temperature drops to absolute zero, as a result of which internal bonds disappear and matter crumbles into free quarks.
2. Bose-Einstein condensate- the aggregate state of matter, which is based on bosons cooled to temperatures close to absolute zero (less than a millionth of a degree above absolute zero). In such a strongly cooled state, a sufficiently large number of atoms find themselves in their minimum possible quantum states, and quantum effects begin to manifest themselves at the macroscopic level. Bose-Einstein condensate (often referred to as "Bose condensate", or simply "back") occurs when you cool a chemical element to extremely low temperatures (usually just above absolute zero, minus 273 degrees Celsius). , is the theoretical temperature at which everything stops moving).
This is where strange things start to happen. Processes normally only observable at the atomic level now occur on scales large enough to be observed with the naked eye. For example, if you put a "back" in a beaker and provide the desired temperature, the substance will begin to crawl up the wall and eventually get out on its own.
Apparently, here we are dealing with a futile attempt by matter to lower its own energy (which is already at the lowest of all possible levels).
Slowing down atoms using cooling equipment produces a singular quantum state known as a Bose condensate, or Bose-Einstein. This phenomenon was predicted in 1925 by A. Einstein, as a result of a generalization of the work of S. Bose, where statistical mechanics was built for particles, ranging from massless photons to atoms with mass (Einstein's manuscript, which was considered lost, was found in the library of Leiden University in 2005 ). The result of the efforts of Bose and Einstein was the Bose concept of a gas that obeys Bose-Einstein statistics, which describes the statistical distribution of identical particles with integer spin, called bosons. Bosons, which are, for example, both individual elementary particles - photons, and whole atoms, can be with each other in the same quantum states. Einstein suggested that cooling atoms - bosons to very low temperatures, would cause them to go (or, in other words, condense) into the lowest possible quantum state. The result of such condensation will be the emergence of a new form of matter.
This transition occurs below the critical temperature, which is for a homogeneous three-dimensional gas consisting of non-interacting particles without any internal degrees of freedom.
3. Fermionic condensate- the state of aggregation of a substance, similar to the backing, but differing in structure. When approaching absolute zero, atoms behave differently depending on the magnitude of their own angular momentum (spin). Bosons have integer spins, while fermions have spins that are multiples of 1/2 (1/2, 3/2, 5/2). Fermions obey the Pauli exclusion principle, which states that two fermions cannot have the same quantum state. For bosons, there is no such prohibition, and therefore they have the opportunity to exist in one quantum state and thereby form the so-called Bose-Einstein condensate. The process of formation of this condensate is responsible for the transition to the superconducting state.
Electrons have spin 1/2 and are therefore fermions. They combine into pairs (so-called Cooper pairs), which then form a Bose condensate.
American scientists attempted to obtain a kind of molecule from fermion atoms by deep cooling. The difference from real molecules was that there was no chemical bond between the atoms - they just moved together in a correlated manner. The bond between atoms turned out to be even stronger than between electrons in Cooper pairs. For the pairs of fermions formed, the total spin is no longer a multiple of 1/2, therefore, they already behave like bosons and can form a Bose condensate with a single quantum state. During the experiment, a gas of potassium-40 atoms was cooled to 300 nanokelvins, while the gas was enclosed in a so-called optical trap. Then an external magnetic field was applied, with the help of which it was possible to change the nature of interactions between atoms - instead of strong repulsion, strong attraction began to be observed. When analyzing the influence of the magnetic field, it was possible to find such a value at which the atoms began to behave like Cooper pairs of electrons. At the next stage of the experiment, scientists propose to obtain the effects of superconductivity for the fermionic condensate.
4. Superfluid matter- a state in which the substance has virtually no viscosity, and when flowing, it does not experience friction with a solid surface. The consequence of this is, for example, such an interesting effect as the complete spontaneous "creeping out" of superfluid helium from the vessel along its walls against gravity. Of course, there is no violation of the law of conservation of energy here. In the absence of friction forces, only gravity forces act on helium, forces of interatomic interaction between helium and the walls of the vessel and between helium atoms. So, the forces of interatomic interaction exceed all other forces combined. As a result, helium tends to spread as much as possible over all possible surfaces, and therefore "travels" along the walls of the vessel. In 1938, the Soviet scientist Pyotr Kapitsa proved that helium can exist in a superfluid state.
It is worth noting that many of the unusual properties of helium have been known for quite some time. However, in recent years, this chemical element has been “spoiling” us with interesting and unexpected effects. So, in 2004, Moses Chan and Eun-Syong Kim of the University of Pennsylvania intrigued the scientific world by claiming that they had succeeded in obtaining a completely new state of helium - a superfluid solid. In this state, some helium atoms in the crystal lattice can flow around others, and helium can thus flow through itself. The effect of "superhardness" was theoretically predicted back in 1969. And in 2004 - as if experimental confirmation. However, later and very curious experiments showed that everything is not so simple, and, perhaps, such an interpretation of the phenomenon, which was previously taken for the superfluidity of solid helium, is incorrect.
The experiment of scientists led by Humphrey Maris from Brown University in the USA was simple and elegant. The scientists placed a test tube turned upside down into a closed tank of liquid helium. Part of the helium in the test tube and in the tank was frozen in such a way that the boundary between liquid and solid inside the test tube was higher than in the tank. In other words, there was liquid helium in the upper part of the test tube, and solid helium in the lower part; it smoothly passed into the solid phase of the tank, over which a little liquid helium was poured - lower than the liquid level in the test tube. If liquid helium began to seep through solid, then the level difference would decrease, and then we can speak of solid superfluid helium. And in principle, in three out of 13 experiments, the level difference did decrease.
5. Superhard matter- a state of aggregation in which matter is transparent and can "flow" like a liquid, but in fact it is devoid of viscosity. Such liquids have been known for many years and are called superfluids. The fact is that if the superfluid is stirred, it will circulate almost forever, while the normal liquid will eventually calm down. The first two superfluids were created by researchers using helium-4 and helium-3. They were cooled almost to absolute zero - to minus 273 degrees Celsius. And from helium-4, American scientists managed to get a superhard body. They compressed the frozen helium by pressure more than 60 times, and then the glass filled with the substance was installed on a rotating disk. At a temperature of 0.175 degrees Celsius, the disk suddenly began to rotate more freely, which, according to scientists, indicates that helium has become a superbody.
6. Solid- the state of aggregation of matter, characterized by the stability of the form and the nature of the thermal motion of atoms, which make small vibrations around the equilibrium positions. The stable state of solids is crystalline. Distinguish solids with ionic, covalent, metallic, and other types of bonds between atoms, which determines the variety of their physical properties. The electrical and some other properties of solids are mainly determined by the nature of the motion of the outer electrons of its atoms. According to their electrical properties, solids are divided into dielectrics, semiconductors, and metals; according to their magnetic properties, they are divided into diamagnets, paramagnets, and bodies with an ordered magnetic structure. The investigations of the properties of solids have united into a large field—solid-state physics, the development of which is being stimulated by the needs of technology.
7. Amorphous solid- a condensed state of aggregation of a substance, characterized by the isotropy of physical properties due to the disordered arrangement of atoms and molecules. In amorphous solids, atoms vibrate around randomly located points. Unlike the crystalline state, the transition from a solid amorphous to liquid occurs gradually. Various substances are in the amorphous state: glasses, resins, plastics, etc.
8. Liquid crystal- this is a specific state of aggregation of a substance in which it simultaneously exhibits the properties of a crystal and a liquid. We must immediately make a reservation that not all substances can be in the liquid crystal state. However, some organic substances with complex molecules can form a specific state of aggregation - liquid crystal. This state is carried out during the melting of crystals of certain substances. When they melt, a liquid-crystalline phase is formed, which differs from ordinary liquids. This phase exists in the range from the melting temperature of the crystal to some higher temperature, when heated to which the liquid crystal transforms into an ordinary liquid.
How does a liquid crystal differ from a liquid and an ordinary crystal and how is it similar to them? Like an ordinary liquid, a liquid crystal has fluidity and takes the form of a vessel in which it is placed. In this it differs from the crystals known to all. However, despite this property, which unites it with a liquid, it has a property characteristic of crystals. This is the ordering in space of the molecules that form the crystal. True, this ordering is not as complete as in ordinary crystals, but, nevertheless, it significantly affects the properties of liquid crystals, which distinguishes them from ordinary liquids. The incomplete spatial ordering of the molecules that form a liquid crystal manifests itself in the fact that in liquid crystals there is no complete order in the spatial arrangement of the centers of gravity of the molecules, although there may be a partial order. This means that they do not have a rigid crystal lattice. Therefore, liquid crystals, like ordinary liquids, have the property of fluidity.
An obligatory property of liquid crystals, which brings them closer to ordinary crystals, is the presence of an order in the spatial orientation of molecules. Such an order in orientation can manifest itself, for example, in the fact that all long axes of molecules in a liquid crystal sample are oriented in the same way. These molecules should have an elongated shape. In addition to the simplest named ordering of the axes of molecules, a more complex orientational order of molecules can be realized in a liquid crystal.
Depending on the type of ordering of the molecular axes, liquid crystals are divided into three types: nematic, smectic and cholesteric.
Research on the physics of liquid crystals and their applications is currently being carried out on a wide front in all the most developed countries of the world. Domestic research is concentrated both in academic and industrial research institutions and has a long tradition. The works of V.K. Frederiks to V.N. Tsvetkov. In recent years, the rapid study of liquid crystals, Russian researchers also make a significant contribution to the development of the theory of liquid crystals in general and, in particular, the optics of liquid crystals. So, the works of I.G. Chistyakova, A.P. Kapustina, S.A. Brazovsky, S.A. Pikina, L.M. Blinov and many other Soviet researchers are widely known to the scientific community and serve as the foundation for a number of effective technical applications of liquid crystals.
The existence of liquid crystals was established a very long time ago, namely in 1888, that is, almost a century ago. Although scientists had encountered this state of matter before 1888, it was officially discovered later.
The first to discover liquid crystals was the Austrian botanist Reinitzer. Investigating the new substance cholesteryl benzoate synthesized by him, he found that at a temperature of 145 ° C, the crystals of this substance melt, forming a cloudy liquid that strongly scatters light. With continued heating, upon reaching a temperature of 179 ° C, the liquid becomes clear, that is, it begins to behave optically like an ordinary liquid, such as water. Cholesteryl benzoate showed unexpected properties in the turbid phase. Examining this phase under a polarizing microscope, Reinitzer found that it has birefringence. This means that the refractive index of light, that is, the speed of light in this phase, depends on the polarization.
9. Liquid- the state of aggregation of a substance, combining the features of a solid state (conservation of volume, a certain tensile strength) and a gaseous state (shape variability). A liquid is characterized by a short-range order in the arrangement of particles (molecules, atoms) and a small difference in the kinetic energy of the thermal motion of molecules and their potential energy of interaction. The thermal motion of liquid molecules consists of oscillations around equilibrium positions and relatively rare jumps from one equilibrium position to another, which is associated with the fluidity of the liquid.
10. Supercritical fluid(GFR) is the state of aggregation of a substance, in which the difference between the liquid and gas phases disappears. Any substance at a temperature and pressure above the critical point is a supercritical fluid. The properties of a substance in the supercritical state are intermediate between its properties in the gas and liquid phases. Thus, SCF has a high density, close to liquid, and low viscosity, like gases. The diffusion coefficient in this case has an intermediate value between liquid and gas. Substances in the supercritical state can be used as substitutes for organic solvents in laboratory and industrial processes. Supercritical water and supercritical carbon dioxide have received the greatest interest and distribution in connection with certain properties.
One of the most important properties of the supercritical state is the ability to dissolve substances. By changing the temperature or pressure of the fluid, one can change its properties in a wide range. Thus, it is possible to obtain a fluid whose properties are close to either a liquid or a gas. Thus, the dissolving power of a fluid increases with increasing density (at a constant temperature). Since the density increases with increasing pressure, changing the pressure can affect the dissolving power of the fluid (at a constant temperature). In the case of temperature, the dependence of fluid properties is somewhat more complicated - at a constant density, the dissolving power of the fluid also increases, but near the critical point, a slight increase in temperature can lead to a sharp drop in density, and, accordingly, dissolving power. Supercritical fluids mix with each other indefinitely, so when the critical point of the mixture is reached, the system will always be single-phase. The approximate critical temperature of a binary mixture can be calculated as the arithmetic mean of the critical parameters of the substances Tc(mix) = (mole fraction of A) x TcA + (mole fraction of B) x TcB.
11. Gaseous- (French gaz, from Greek chaos - chaos), the aggregate state of matter in which the kinetic energy of the thermal motion of its particles (molecules, atoms, ions) significantly exceeds the potential energy of interactions between them, and therefore the particles move freely, uniformly filling in the absence of external fields, the entire volume provided to them.
12. Plasma- (from the Greek plasma - fashioned, shaped), a state of matter, which is an ionized gas, in which the concentrations of positive and negative charges are equal (quasi-neutrality). The vast majority of matter in the Universe is in the plasma state: stars, galactic nebulae and the interstellar medium. Near the Earth, plasma exists in the form of the solar wind, magnetosphere, and ionosphere. High-temperature plasma (T ~ 106 - 108 K) from a mixture of deuterium and tritium is being investigated with the aim of implementing controlled thermonuclear fusion. Low-temperature plasma (T Ј 105K) is used in various gas-discharge devices (gas lasers, ion devices, MHD generators, plasma torches, plasma engines, etc.), as well as in technology (see Plasma metallurgy, Plasma drilling, Plasma technology) .
13. Degenerate matter- is an intermediate stage between plasma and neutronium. It is observed in white dwarfs and plays an important role in the evolution of stars. When atoms are under conditions of extremely high temperatures and pressures, they lose their electrons (they go into an electron gas). In other words, they are completely ionized (plasma). The pressure of such a gas (plasma) is determined by the electron pressure. If the density is very high, all particles are forced to approach each other. Electrons can be in states with certain energies, and two electrons cannot have the same energy (unless their spins are opposite). Thus, in a dense gas, all lower energy levels turn out to be filled with electrons. Such a gas is called degenerate. In this state, the electrons exhibit a degenerate electron pressure that opposes the forces of gravity.
14. Neutronium— state of aggregation into which matter passes under ultrahigh pressure, which is unattainable in the laboratory yet, but exists inside neutron stars. During the transition to the neutron state, the electrons of matter interact with protons and turn into neutrons. As a result, matter in the neutron state consists entirely of neutrons and has a density of the order of nuclear. The temperature of the substance in this case should not be too high (in energy equivalent, not more than a hundred MeV).
With a strong increase in temperature (hundreds of MeV and above), in the neutron state, various mesons begin to be born and annihilate. With a further increase in temperature, deconfinement occurs, and the matter passes into the state of quark-gluon plasma. It no longer consists of hadrons, but of constantly born and disappearing quarks and gluons.
15. Quark-gluon plasma(chromoplasm) is an aggregate state of matter in high-energy physics and elementary particle physics, in which hadronic matter passes into a state similar to the state in which electrons and ions are in ordinary plasma.
Usually the matter in hadrons is in the so-called colorless ("white") state. That is, quarks of different colors compensate each other. A similar state exists in ordinary matter - when all atoms are electrically neutral, that is,
positive charges in them are compensated by negative ones. At high temperatures, ionization of atoms can occur, while the charges are separated, and the substance becomes, as they say, "quasi-neutral". That is, the entire cloud of matter as a whole remains neutral, and its individual particles cease to be neutral. Presumably, the same thing can happen with hadronic matter - at very high energies, color is released and makes the substance "quasi-colorless".
Presumably, the matter of the Universe was in the state of quark-gluon plasma in the first moments after the Big Bang. Now quark-gluon plasma can be formed for a short time in collisions of particles of very high energies.
Quark-gluon plasma was obtained experimentally at the RHIC accelerator at Brookhaven National Laboratory in 2005. The maximum plasma temperature of 4 trillion degrees Celsius was obtained there in February 2010.
16. Strange substance- state of aggregation, in which matter is compressed to the limit values of density, it can exist in the form of "quark soup". A cubic centimeter of matter in this state would weigh billions of tons; besides, it will turn any normal substance with which it comes into contact into the same "strange" form with the release of a significant amount of energy.
The energy that can be released during the transformation of the substance of the core of a star into a "strange substance" will lead to a super-powerful explosion of a "quark nova" - and, according to Leahy and Wyed, it was precisely this explosion that astronomers observed in September 2006.
The process of formation of this substance began with an ordinary supernova, into which a massive star turned. As a result of the first explosion, a neutron star was formed. But, according to Leahy and Wyed, it did not last long - as its rotation seemed to be slowed down by its own magnetic field, it began to shrink even more, with the formation of a clot of "strange stuff", which led to an even more powerful than in a normal supernova explosion, the release of energy - and the outer layers of the substance of the former neutron star, flying into the surrounding space at a speed close to the speed of light.
17. Strongly symmetrical matter- this is a substance compressed to such an extent that the microparticles inside it are layered on top of each other, and the body itself collapses into a black hole. The term "symmetry" is explained as follows: Let's take the aggregate states of matter known to everyone from the school bench - solid, liquid, gaseous. For definiteness, consider an ideal infinite crystal as a solid. It has a certain, so-called discrete symmetry with respect to translation. This means that if the crystal lattice is shifted by a distance equal to the interval between two atoms, nothing will change in it - the crystal will coincide with itself. If the crystal is melted, then the symmetry of the resulting liquid will be different: it will increase. In a crystal, only points that were distant from each other at certain distances, the so-called nodes of the crystal lattice, in which identical atoms were located, were equivalent.
The liquid is homogeneous throughout its volume, all its points are indistinguishable from one another. This means that liquids can be displaced by any arbitrary distances (and not just some discrete ones, as in a crystal) or rotated by any arbitrary angles (which cannot be done in crystals at all) and it will coincide with itself. Its degree of symmetry is higher. The gas is even more symmetrical: the liquid occupies a certain volume in the vessel and there is an asymmetry inside the vessel, where there is liquid, and points where it is not. The gas, on the other hand, occupies the entire volume provided to it, and in this sense all its points are indistinguishable from one another. Nevertheless, here it would be more correct to speak not about points, but about small, but macroscopic elements, because at the microscopic level there are still differences. At some points in time there are atoms or molecules, while others do not. Symmetry is observed only on average, either in some macroscopic volume parameters, or in time.
But there is still no instantaneous symmetry at the microscopic level. If the substance is compressed very strongly, to pressures that are unacceptable in everyday life, compressed so that the atoms were crushed, their shells penetrated each other, and the nuclei began to touch, symmetry arises at the microscopic level. All nuclei are the same and pressed against each other, there are not only interatomic, but also internuclear distances, and the substance becomes homogeneous (strange substance).
But there is also a submicroscopic level. Nuclei are made up of protons and neutrons that move around inside the nucleus. There is also some space between them. If you continue to compress so that the nuclei are also crushed, the nucleons will tightly press against each other. Then, at the submicroscopic level, symmetry will appear, which is not even inside ordinary nuclei.
From what has been said, one can see a quite definite trend: the higher the temperature and the higher the pressure, the more symmetrical the substance becomes. Based on these considerations, a substance compressed to a maximum is called strongly symmetrical.
18. Weakly symmetrical matter- a state opposite to strongly symmetrical matter in its properties, which was present in the very early Universe at a temperature close to the Planck temperature, perhaps 10-12 seconds after the Big Bang, when strong, weak and electromagnetic forces were a single superforce. In this state, matter is compressed to such an extent that its mass is converted into energy, which begins to inflate, that is, expand without limit. It is not yet possible to achieve energies for the experimental production of superpower and the transfer of matter to this phase under terrestrial conditions, although such attempts were made at the Large Hadron Collider in order to study the early universe. Due to the absence of gravitational interaction in the composition of the superforce that forms this substance, the superforce is not sufficiently symmetrical in comparison with the supersymmetric force, which contains all 4 types of interactions. Therefore, this state of aggregation received such a name.
19. Radiation matter- this, in fact, is no longer a substance, but energy in its purest form. However, it is this hypothetical state of aggregation that a body that has reached the speed of light will take. It can also be obtained by heating the body to the Planck temperature (1032K), that is, by dispersing the molecules of the substance to the speed of light. As follows from the theory of relativity, when the speed reaches more than 0.99 s, the mass of the body begins to grow much faster than with "normal" acceleration, in addition, the body lengthens, warms up, that is, it begins to radiate in the infrared spectrum. When crossing the threshold of 0.999 s, the body radically changes and begins a rapid phase transition up to the beam state. As follows from Einstein's formula, taken in full, the growing mass of the final substance is made up of masses that are separated from the body in the form of thermal, X-ray, optical and other radiation, the energy of each of which is described by the next term in the formula. Thus, a body approaching the speed of light will begin to radiate in all spectra, grow in length and slow down in time, thinning to the Planck length, that is, upon reaching speed c, the body will turn into an infinitely long and thin beam moving at the speed of light and consisting of photons that have no length, and its infinite mass will completely turn into energy. Therefore, such a substance is called radiation.
