4 aggregate states of matter in physics. Properties of substances in different states of aggregation. Comparative characteristics of amorphous and crystalline substances
Aggregate states. Liquids. Phases in thermodynamics. Phase transitions.
Lecture 1.16
All substances can exist in three states of aggregation - solid, liquid and gaseous... The transitions between them are accompanied by an abrupt change in a number of physical properties (density, thermal conductivity, etc.).
The state of aggregation depends on the physical conditions in which the substance is located. The existence of several states of aggregation in a substance is due to differences in the thermal motion of its molecules (atoms) and in their interaction under different conditions.
Gas- the state of aggregation of matter, in which the particles are not bound or very weakly bound by the forces of interaction; the kinetic energy of the thermal motion of its particles (molecules, atoms) significantly exceeds the potential energy of interactions between them, therefore the particles move almost freely, completely filling the vessel in which they are located, and take its shape. In a gaseous state, a substance has neither its own volume nor its own form. Any substance can be converted into gaseous by changing pressure and temperature.
Liquid- the state of aggregation of matter, intermediate between solid and gaseous. It is characterized by a high mobility of particles and a small free space between them. This leads to the fact that liquids retain their volume and take the shape of a vessel. In a liquid, molecules are very close to each other. Therefore, the density of the liquid is much higher than the density of gases (at normal pressure). Liquid properties in all directions are the same (isotropic) with the exception of liquid crystals. When heating or a decrease in density, the properties of a liquid, thermal conductivity, and viscosity change, as a rule, in the direction of approaching the properties of gases.
The thermal motion of liquid molecules consists of a combination of collective vibrational motions and the occasional jumps of molecules from one equilibrium position to another.
Solid (crystalline) bodies- the state of aggregation of matter, characterized by the stability of the form and the nature of the thermal motion of atoms. This movement is the vibrations of atoms (or ions) that make up a solid. The vibration amplitude is usually small compared to the interatomic distances.
Properties of liquids.
The molecules of a substance in a liquid state are located almost closely to each other. Unlike solid crystalline bodies, in which molecules form ordered structures throughout the entire volume of the crystal and can perform thermal vibrations around fixed centers, liquid molecules have greater freedom. Each molecule of a liquid, as well as in a solid, is "clamped" on all sides by neighboring molecules and performs thermal vibrations about a certain equilibrium position. However, from time to time, any molecule can move to an adjacent vacant place. Such jumps in liquids occur quite frequently; therefore, the molecules are not attached to specific centers, as in crystals, and can move throughout the entire volume of the liquid. This explains the fluidity of liquids. Because of the strong interaction between closely spaced molecules, they can form local (unstable) ordered groups containing several molecules. This phenomenon is called short order.
Due to the close packing of molecules, the compressibility of liquids, that is, the change in volume with a change in pressure, is very small; it is tens and hundreds of thousands of times less than in gases. For example, to change the volume of water by 1%, you need to increase the pressure approximately 200 times. Such an increase in pressure as compared to atmospheric pressure is achieved at a depth of about 2 km.
Liquids, like solids, change their volume when the temperature changes. For not very large temperature ranges, the relative volume change Δ V / V 0 proportional to the temperature change Δ T:
| |
The coefficient β is called temperature coefficient of volumetric expansion... This coefficient for liquids is tens of times greater than that of solids. For water, for example, at a temperature of 20 ° C β in ≈ 2 · 10 –4 K –1, for steel - β st ≈ 3.6 · 10 –5 K –1, for quartz glass - β q ≈ 9 · 10 - 6 K –1.
Thermal expansion of water has an interesting and important anomaly for life on Earth. At temperatures below 4 ° C, water expands with decreasing temperature (β< 0). Максимум плотности ρ в = 10 3 кг/м 3 вода имеет при температуре 4 °С.
When water freezes, it expands, so the ice remains floating on the surface of the freezing body of water. The temperature of the freezing water under the ice is 0 ° С. In denser layers of water at the bottom of the reservoir, the temperature is about 4 ° C. Thanks to this, life can exist in the water of freezing reservoirs.
The most interesting feature of liquids is the presence free surface... Liquid, unlike gases, does not fill the entire volume of the vessel into which it is poured. An interface forms between the liquid and the gas (or vapor), which is in special conditions compared to the rest of the liquid mass. Molecules in the boundary layer of a liquid, unlike molecules in its depth, are not surrounded by other molecules of the same liquid on all sides. The forces of intermolecular interaction acting on one of the molecules inside the liquid from the side of neighboring molecules are, on average, mutually compensated. Any molecule in the boundary layer is attracted by molecules inside the liquid (forces acting on a given liquid molecule from the side of gas (or vapor) molecules can be neglected). As a result, a certain resultant force appears, directed deep into the liquid. Surface molecules are drawn into the liquid by the forces of intermolecular attraction. But all molecules, including those of the boundary layer, must be in a state of equilibrium. This equilibrium is achieved due to a slight decrease in the distance between the molecules of the surface layer and their nearest neighbors inside the liquid. With a decrease in the distance between the molecules, repulsive forces arise. If the average distance between molecules inside the liquid is r 0, then the molecules of the surface layer are packed somewhat more densely, and therefore they have an additional store of potential energy in comparison with the inner molecules. It should be borne in mind that due to the extremely low compressibility, the presence of a more densely packed surface layer does not lead to any noticeable change in the volume of the liquid. If the molecule moves from the surface to the interior of the liquid, the forces of intermolecular interaction will do a positive job. On the contrary, in order to pull a certain number of molecules from the depth of the liquid to the surface (i.e., to increase the surface area of the liquid), external forces must do positive work A ext, proportional to the change in Δ S surface area:
| A ext = σΔ S. |
The coefficient σ is called the coefficient of surface tension (σ> 0). Thus, the surface tension coefficient is equal to the work required to increase the surface area of a liquid at a constant temperature by one unit.
In SI, the surface tension is measured in joules per meter square (J / m 2) or in newtons per meter (1 N / m = 1 J / m 2).
Consequently, the molecules of the surface layer of the liquid have an excess in comparison with the molecules inside the liquid potential energy... Potential energy E p of the liquid surface is proportional to its area: 
(1.16.1)
It is known from mechanics that the equilibrium states of a system correspond to the minimum value of its potential energy. Hence it follows that the free surface of the liquid tends to reduce its area. For this reason, a free drop of liquid takes on a spherical shape. The fluid behaves as if forces are acting tangentially to its surface, reducing (pulling) this surface. These forces are called surface tension forces.
The presence of surface tension forces makes the surface of the liquid similar to an elastic stretched film, with the only difference that the elastic forces in the film depend on its surface area (i.e., on how the film is deformed), and surface tension forces do not depend on the surface area liquids.
Surface tension forces tend to shrink the film surface. Therefore, we can write: (1.16.2)
Thus, the surface tension coefficient σ can be defined as the modulus of the surface tension force acting on the unit length of the line bounding the surface ( l is the length of this line).
Due to the action of surface tension forces in liquid droplets and inside soap bubbles, excess pressure Δ p... If you mentally cut a spherical drop of radius R into two halves, then each of them must be in equilibrium under the action of surface tension forces applied to the cut boundary 2π R and overpressure forces acting on the area π R 2 sections (Figure 1.16.1). The equilibrium condition is written as
Near the boundary between a liquid, a solid and a gas, the shape of the free surface of a liquid depends on the forces of interaction of liquid molecules with solid molecules (interaction with gas (or vapor) molecules can be neglected). If these forces are greater than the forces of interaction between the molecules of the liquid itself, then the liquid wets surface of a solid. In this case, the liquid approaches the surface of the solid at a certain acute angle θ, which is characteristic of the given pair of liquid - solid. The angle θ is called edge angle... If the forces of interaction between molecules of a liquid exceed the forces of their interaction with molecules of a solid, then the contact angle θ turns out to be obtuse (Fig. 1.16.2 (2)). In this case, they say that the liquid does not wet surface of a solid. Otherwise (angle - sharp) liquid wets surface (Figure 1.16.2 (1)). At full wettingθ = 0, for complete non-wettingθ = 180 °.
Capillary phenomena called the rise or fall of liquid in small diameter tubes - capillaries... Wetting liquids rise through the capillaries, non-wetting liquids go down.
Figure 1.16.3 shows a capillary tube of a certain radius r lowered by its lower end into a wetting liquid of density ρ. The upper end of the capillary is open. The rise of liquid in the capillary continues until the force of gravity acting on the column of liquid in the capillary becomes equal in magnitude to the resulting F n surface tension forces acting along the interface between the liquid and the capillary surface: F t = F n, where F t = mg = ρ hπ r 2 g, F n = σ2π r cos θ.
This implies: 
With complete wetting θ = 0, cos θ = 1. In this case
With complete non-wetting θ = 180 °, cos θ = –1 and, therefore, h < 0. Уровень несмачивающей жидкости в капилляре опускается ниже уровня жидкости в сосуде, в которую опущен капилляр.
Water almost completely wets the clean glass surface. Conversely, mercury does not completely wet the glass surface. Therefore, the level of mercury in the glass capillary drops below the level in the vessel.
The most common knowledge about three states of aggregation: liquid, solid, gaseous, sometimes remember about plasma, less often liquid crystal. Recently, a list of 17 phases of a substance, taken from the famous () Stephen Fry, has spread on the Internet. Therefore, we will tell you more about them, because you 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. can be continued. At the same time, it should be understood that the degree of compression of the substance and its pressure (with some reservations for such unexplored hypothetical states such as quantum, radial, or weakly symmetric) increase from the gaseous state (No. 11), the most "unclenched", to both sides of the list. a visual graph of the phase transitions of matter is shown.
1. Quantum- the state of aggregation of a substance, achieved when the temperature is lowered to absolute zero, as a result of which internal connections disappear and matter disintegrates 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 called "Bose condensate", or simply "back") occurs when you cool a chemical element to extremely low temperatures (usually to a temperature slightly above absolute zero, minus 273 degrees Celsius , Is the theoretical temperature at which everything stops moving).
This is where completely strange things begin to happen to the substance. Processes normally only seen at the atomic level now take place on a scale large enough to be observed with the naked eye. For example, if you put the “backing” in a beaker and provide the required temperature, the substance will begin to crawl up the wall and eventually will get out by itself.
Apparently, here we are dealing with a futile attempt by the substance to lower its own energy (which is already at the lowest of all possible levels).
Slowing down the atoms using cooling equipment produces a singular quantum state known as a Bose condensate, or Bose-Einstein condensate. 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 a mass (Einstein's manuscript, which was considered lost, was discovered in the library of Leiden University in 2005 ). The result of the efforts of Bose and Einstein was the concept of Bose gas obeying Bose-Einstein statistics, which describes the statistical distribution of identical particles with integer spin, called bosons. Bosons, which are, for example, and 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 force 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. Fermion 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 the proper angular momentum (spin). Bosons have integer spins, while fermions have multiples of 1/2 (1/2, 3/2, 5/2). Fermions obey the Pauli exclusion principle, according to which two fermions cannot have the same quantum state. There is no such prohibition for bosons, and therefore they have the opportunity to exist in one quantum state and thereby form the so-called Bose-Einstein condensate. The 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 (called Cooper pairs), which then form a Bose condensate.
American scientists have attempted to obtain a kind of molecule from fermion atoms with deep cooling. The difference from real molecules was that there was no chemical bond- 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 formed pairs of fermions, 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. In the course of the experiment, a gas of potassium-40 atoms was cooled to 300 nanokelvin, while the gas was contained in a so-called optical trap. Then an external magnetic field was imposed, with the help of which it was possible to change the nature of interactions between atoms - instead of a strong repulsion, a strong attraction began to be observed. When analyzing the influence of the magnetic field, it was possible to find its 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 fermion condensate.
4. Superfluid substance- a state in which a substance has virtually no viscosity, and during flow 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" of superfluid helium from the vessel along its walls against the force of gravity. Of course, there is no violation of the law of conservation of energy. In the absence of friction forces, only gravity, the forces of interatomic interaction between helium and the walls of the vessel and between helium atoms act on helium. 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-Siong Kim from the University of Pennsylvania intrigued the scientific world with the statement that they had managed to obtain a completely new state of helium - a superfluid solid. In this state, some helium atoms in the crystal lattice can flow around others, and thus helium can flow through itself. The "superhardness" effect was theoretically predicted back in 1969. And now in 2004 - as if it was an experimental confirmation. However, later and very interesting experiments showed that not everything is 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 United States was simple and elegant. Scientists placed a test tube upside down in a closed reservoir of liquid helium. Some of the helium in the test tube and in the reservoir was frozen in such a way that the boundary between liquid and solid inside the test tube was higher than in the reservoir. In other words, in the upper part of the test tube there was liquid helium, in the lower part - solid, it smoothly passed into the solid phase of the reservoir, 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 talk about solid superfluid helium. And in principle, in three of the 13 experiments, the level difference actually decreased.
5. Superhard substance- an aggregate state in which matter is transparent and can "flow" like a liquid, but in fact it is devoid of viscosity. Such fluids 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 the researchers using helium-4 and helium-3. They were cooled to almost 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 more than 60 times pressure, and then the glass filled with the substance was placed on a rotating disk. At a temperature of 0.175 degrees Celsius, the disk suddenly began to spin more freely, which, according to scientists, indicates that helium has become a superbody.
6. Solid- the aggregate state of matter, characterized by the stability of the form and the nature of the thermal motion of atoms, which perform small vibrations around the equilibrium positions. The stable state of solids is crystalline. Distinguish between solids with ionic, covalent, metallic and other types of bonds between atoms, which determines the variety of their physical properties. Electrical and some other properties of solids are mainly determined by the nature of the movement 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 - into diamagnets, paramagnets and bodies with an ordered magnetic structure. Research into the properties of solids has united into a large area - solid state physics, the development of which is stimulated by the needs of technology.
7. Amorphous solid- condensed aggregate state of matter, characterized by isotropy of physical properties due to the disordered arrangement of atoms and molecules. In amorphous solids, atoms vibrate around randomly located points. In contrast to the crystalline state, the transition from solid amorphous to liquid occurs gradually. Various substances are in the amorphous state: glasses, resins, plastics, etc.
8. Liquid crystal Is a specific aggregate state of a substance in which it simultaneously exhibits the properties of a crystal and a liquid. Immediately it is necessary to make a reservation that not all substances can be in a liquid crystal state. However, some organic matter possessing complex molecules can form a specific aggregate state - liquid crystal. This state occurs when crystals of some substances melt. When they melt, a liquid crystal phase is formed, which differs from ordinary liquids. This phase exists in the range from the melting point 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 is fluid 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. Incomplete spatial ordering of the molecules that form a liquid crystal is manifested in the fact that in liquid crystals there is no complete order in the spatial arrangement of the centers of gravity of 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.
Required property liquid crystals, bringing them closer to ordinary crystals, is the presence of the order of the spatial orientation of molecules. This 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 must have elongated shape... In addition to the simplest named ordering of the molecular axes, 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 in the physics of liquid crystals and their applications is currently being carried out on a broad front in all the most developed countries of the world. Domestic research is concentrated in both academic and industrial research institutions and has a long tradition. The works of V.K. Fredericks to V.N. Tsvetkova. In recent years, the vigorous study of liquid crystals, Russian researchers have also made a significant contribution to the development of the theory of liquid crystals in general and, in particular, of the optics of liquid crystals. Thus, 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 were faced with 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 he synthesized, cholesteryl benzoate, he found that at a temperature of 145 ° C, the crystals of this substance melt, forming a turbid liquid, strongly scattering light. As the heating continues, upon reaching a temperature of 179 ° C, the liquid clears up, that is, it begins to behave optically like an ordinary liquid, for example water. Cholesteryl benzoate exhibited unexpected properties in a cloudy phase. Examining this phase under a polarizing microscope, Rey-nitzer discovered 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, which combines the features of a solid state (retention of volume, a certain tensile strength) and gaseous (variability of shape). A liquid is characterized by 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 interaction energy. The thermal motion of liquid molecules consists of oscillations about equilibrium positions and relatively rare jumps from one equilibrium position to another, which is associated with the fluidity of the liquid.
10. Supercritical fluid(SCF) - 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 a supercritical state are intermediate between its properties in the gas and liquid phases. So, SCF has a high density, close to a liquid, and a low viscosity, like gases. In this case, the diffusion coefficient has an intermediate value between liquid and gas. Supercritical substances 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, you can change its properties in a wide range. So, you can get a fluid that is close in properties to either a liquid or a gas. Thus, the dissolving ability 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 ability of the fluid (at constant temperature). In the case of temperature, the envy of the properties of the fluid is somewhat more complicated - at a constant density, the dissolving ability of the fluid also increases, however, near the critical point, a slight increase in temperature can lead to a sharp drop in density, and, accordingly, in the dissolving ability. Supercritical fluids mix indefinitely with each other, therefore, 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 substances Tc (mix) = (mole fraction A) x TcA + (mole fraction B) x TcB.
11. Gaseous- (French gaz, from the Greek chaos - chaos), the state of aggregation 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, evenly filling in the entire volume provided to them in the absence of external fields.
12. Plasma- (from the Greek. Plasma - sculpted, shaped), the state of matter, which is an ionized gas, in which the concentrations of positive and negative charges are equal (quasineutrality). The vast majority of the substance of the Universe is in the state of plasma: stars, galactic nebulae and the interstellar medium. Plasma exists near the Earth in the form of the solar wind, magnetosphere and ionosphere. High-temperature plasma (T ~ 106-108K) from a mixture of deuterium and tritium is being investigated for the purpose of controlled thermonuclear fusion. Low-temperature plasma (T Ј 105K) is used in various gas-discharge devices (gas lasers, ion devices, MHD generators, plasmatrons, plasma engines, etc.), as well as in technology (see Plasma metallurgy, Plasma drilling, Plasma technology) ...
13. Degenerate substance- 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 extremely high temperatures and pressures, they lose their electrons (they go into electron gas). In other words, they are completely ionized (plasma). The pressure of such a gas (plasma) is determined by the pressure of the electrons. If the density is very high, all the 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 the lower energy levels are filled with electrons. Such a gas is called degenerate. In this state, electrons exhibit degenerate electron pressure, which opposes the forces of gravity.
14. Neutronium- the state of aggregation, into which matter passes at ultrahigh pressure, which is unattainable in the laboratory, but exists inside neutron stars. During the transition to the neutron state, the electrons of a substance interact with protons and turn into neutrons. As a result, the substance in the neutron state consists entirely of neutrons and has a density of the order of the nuclear one. In this case, the temperature of the substance should not be too high (in energy equivalent, no more than a hundred MeV).
With a strong increase in temperature (hundreds of MeV and above), various mesons begin to be produced and annihilated in the neutron state. With a further increase in temperature, deconfinement occurs, and the substance passes into the state of a quark-gluon plasma. It no longer consists of hadrons, but of quarks and gluons that are constantly being born and disappearing.
15. Quark-gluon plasma(chromoplasm) - the 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 matter in hadrons is in the so-called colorless ("white") state. That is, quarks of different colors cancel each other out. Ordinary matter has a similar state - 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, "quasineutral". That is, the entire cloud of matter as a whole remains neutral, and its individual particles cease to be neutral. Exactly the same, apparently, can happen with hadronic matter - at very high energies, color is released and makes matter "quasi-colorless."
Presumably, the substance of the Universe was in the state of a quark-gluon plasma in the first moments after the Big Bang. Now quark-gluon plasma can be formed for a short time by 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- the state of aggregation, in which matter is compressed to the limit values of density, it can exist in the form of a "quark soup". A cubic centimeter of matter in this state will weigh billions of tons; moreover, it will transform 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 matter of the star's core into "strange matter" will lead to a super-powerful explosion of the "quark nova" - and, according to Leahy and Wyed, it was his astronomers who observed in September 2006.
The process of the 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 Uyed, 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 matter", which led to an even more powerful than during an ordinary supernova explosion, the release of energy - and the outer layers of the substance of the former neutron star, scattering into the surrounding space at a speed close to the speed of light.
17. Strongly symmetrical substance 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 black hole... The term "symmetry" is explained as follows: Let's take the aggregate states of matter known to everyone from school - solid, liquid, gaseous. For definiteness, consider an ideal infinite crystal as a solid. It has a certain so-called discrete symmetry with respect to transfer. This means that if you move the crystal lattice 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 the crystal, only points were equivalent, which were distant from each other at certain distances, the so-called nodes of the crystal lattice, in which there were identical atoms.
The liquid is homogeneous throughout its volume, all its points are indistinguishable from one another. This means that a liquid can be displaced at any arbitrary distance (and not only at some discrete, as in a crystal) or rotated at any arbitrary angles (which cannot be done in crystals at all) and it will coincide with itself. The degree of its symmetry is higher. The gas is even more symmetric: the liquid occupies a certain volume in the vessel and asymmetry is observed inside the vessel, where there is liquid, and points where it is not. Gas occupies the entire volume provided to it, and in this sense, all its points are indistinguishable from one another. Yet here it would be more correct to speak not about points, but about small, but macroscopic elements, because there are still differences at the microscopic level. At some points at a given time there are atoms or molecules, while others do not. Symmetry is observed only on average, either over some macroscopic volume parameters, or over time.
But there is still no instant symmetry at the microscopic level. If the substance is compressed very strongly, up to pressures that are unacceptable in everyday life, compress 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, not only interatomic, but also internuclear distances are absent, and the substance becomes homogeneous (strange substance).
But there is also a submicroscopic level. Nuclei are made up of protons and neutrons that move inside the nucleus. There is also some space between them. If you continue to squeeze so that the nuclei will be crushed too, the nucleons will be tightly pressed 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 tendency: the higher the temperature and the higher the pressure, the more symmetrical the substance becomes. Based on these considerations, the substance compressed to the maximum is called strongly symmetric.
18. Weakly symmetric substance- a state opposite to a strongly symmetric substance in its properties, which was present in a 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 superpower. In this state, matter is compressed to such an extent that its mass is converted into energy, which begins to influence, that is, to expand indefinitely. It is not yet possible to reach energies for the experimental obtaining of superpower and transfer of matter into 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 super-force that forms this substance, the super-force is not sufficiently symmetric in comparison with the supersymmetric force, which contains all 4 types of interactions. Therefore, this state of aggregation has received such a name.
19. Beam matter- this, in fact, is not a substance at all, but energy in its pure form. However, it is this hypothetical state of aggregation that a body will assume when it has reached the speed of light. It can also be obtained by heating the body to the Planck temperature (1032K), that is, by accelerating the molecules of the substance to the speed of light. As follows from the theory of relativity, when a speed of more than 0.99 s is reached, the body's mass begins to grow much faster than during "normal" acceleration, in addition, the body lengthens, heats up, that is, begins to radiate in the infrared spectrum. Upon crossing the threshold of 0.999 s, the body changes dramatically and begins a rapid phase transition up to the ray state. As follows from Einstein's formula, taken in full form, the growing mass of the final substance consists 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 emit in all spectra, grow in length and slow down in time, thinning to the Planck length, that is, upon reaching the speed c, the body will turn into an infinitely long and thin ray moving at the speed of light and consisting of photons that have no length, and its infinite mass will completely transform into energy. Therefore, such a substance is called ray.
State of matter
Substance- a really existing set of particles connected with each other by chemical bonds and under certain conditions in one of the aggregate states. Any substance consists of a collection of a very large number of particles: atoms, molecules, ions, which can combine with each other into associates, also called aggregates or clusters. Depending on the temperature and behavior of particles in associates (mutual arrangement of particles, their number and interaction in an associate, as well as the distribution of associates in space and their interaction with each other), a substance can be in two basic states of aggregation - crystalline (solid) or gaseous, and in transitional states of aggregation - amorphous (solid), liquid crystal, liquid and vapor. Solid, liquid crystal and liquid states of aggregation are condensed, and vapor and gaseous states are highly discharged.
Phase Is a set of homogeneous microregions characterized by the same ordering and concentration of particles and enclosed in a macroscopic volume of a substance bounded by the interface. In this understanding, the phase is characteristic only for substances in crystalline and gaseous states, since these are homogeneous states of aggregation.
Metaphase Is a set of dissimilar microregions that differ from each other in the degree of ordering of particles or in their concentration and are enclosed in a macroscopic volume of a substance bounded by the interface. In this understanding, metaphase is characteristic only for substances in heterogeneous transitional states of aggregation. Different phases and metaphases can mix between each other, forming one aggregate state, and then there is no interface between them.
Usually, the concepts of "ground" and "transitional" aggregate states are not separated. The concepts of "state of aggregation", "phase" and "mesophase" are often used interchangeably. It is advisable to consider five possible aggregate states for the state of substances: solid, liquid crystal, liquid, vapor, gaseous. The transition from one phase to another phase is called a first-order and second-order phase transition. Phase transitions of the first kind are characterized by:
An abrupt change in physical grandeur, describing the state of matter (volume, density, viscosity, etc.);
A certain temperature at which this phase transition occurs
A certain warmth, which characterizes this transition, because intermolecular bonds are broken.
Phase transitions of the first kind are observed during the transition from one state of aggregation to another state of aggregation. Phase transitions of the second kind are observed with a change in the ordering of particles within one aggregate state, characterized by:
A gradual change in the physical properties of a substance;
Changes in the ordering of particles of a substance under the influence of a gradient of external fields or at a certain temperature, called the temperature of the phase transition;
The heat of second-order phase transitions is equal and close to zero.
The main difference between the phase transitions of the first and second order is that the first-order transitions, first of all, change the energy of the particles of the system, and in the case of second-order transitions, the ordering of the particles of the system.
The transition of a substance from a solid state to a liquid is called melting and is characterized by a melting point. The transition of a substance from a liquid to a vapor state is called evaporation and is characterized by a boiling point. For some substances with a low molecular weight and weak intermolecular interaction, a direct transition from a solid to a vapor state is possible, bypassing the liquid state. This transition is called sublimation. All of these processes can also proceed in the opposite direction: then they are called freezing, condensation, desublimation.
Substances that do not decompose during melting and boiling can be, depending on temperature and pressure, in all four states of aggregation.
Solid state
At a sufficiently low temperature, almost all substances are in a solid state. In this state, the distance between the particles of a substance is comparable to the size of the particles themselves, which ensures their strong interaction and a significant excess of their potential energy over kinetic energy .. The movement of particles of a solid is limited only by minor vibrations and rotations relative to the position they occupy, and they have no translational motion ... This leads to internal orderliness in the arrangement of particles. Therefore, solids are characterized by their own shape, mechanical strength, constant volume (they are practically incompressible). Depending on the degree of ordering of the particles, solids are divided into crystalline and amorphous.
Crystalline substances are characterized by the presence of order in the arrangement of all particles. The solid phase of crystalline substances consists of particles that form a homogeneous structure characterized by a strict repeatability of the same unit cell in all directions. The unit cell of a crystal characterizes the three-dimensional periodicity in the arrangement of particles, i.e. its crystal lattice. Crystalline lattices are classified according to the type of particles that make up the crystal and the nature of the forces of attraction between them.
Many crystalline substances, depending on the conditions (temperature, pressure), can have a different crystal structure. This phenomenon is called polymorphism. Well-known polymorphic modifications of carbon: graphite, fullerene, diamond, carbyne.
Amorphous (shapeless) substances. This condition is typical for polymers. Long molecules easily bend and intertwine with other molecules, resulting in irregular particle arrangement.
The difference between amorphous and crystalline particles:
isotropy - the same physical and chemical properties of a body or environment in all directions, i.e. independence of properties from direction;
no fixed melting point.
Glass, fused silica, and many polymers have an amorphous structure. Amorphous substances are less stable than crystalline ones, and therefore any amorphous body can eventually pass into an energetically more stable state - crystalline.
Liquid state
With an increase in temperature, the energy of thermal vibrations of particles increases, and for each substance there is a temperature, starting from which the energy of thermal vibrations exceeds the energy of bonds. The particles can make different movements, moving relative to each other. They still remain in contact, although the correct geometric structure of the particles is violated - the substance exists in a liquid state. Due to the mobility of particles, the liquid state is characterized by Brownian motion, diffusion and volatility of particles. An important property of a fluid is viscosity, which characterizes the inter-associative forces that impede the free flow of the fluid.
Liquids occupy an intermediate position between the gaseous and solid state of substances. More ordered structure than gas, but less than solid.
Steam and gaseous state
The vapor-gaseous state is usually not distinguished.
Gas - it is a highly discharged homogeneous system consisting of individual molecules far removed from each other, which can be considered as a single dynamic phase.
Steam - it is a highly discharged inhomogeneous system, which is a mixture of molecules and unstable small associates consisting of these molecules.
Molecular kinetic theory explains the properties of an ideal gas, based on the following provisions: molecules make continuous random motion; the volume of gas molecules is negligible compared to the intermolecular distances; forces of attraction or repulsion do not act between gas molecules; the average kinetic energy of gas molecules is proportional to its absolute temperature. Due to the insignificance of the forces of intermolecular interaction and the presence of a large free volume, gases are characterized by a high rate of thermal motion and molecular diffusion, the desire of molecules to occupy the largest possible volume, as well as high compressibility.
An isolated gas-phase system is characterized by four parameters: pressure, temperature, volume, amount of substance. The relationship between these parameters is described by the ideal gas equation of state:
R = 8.31 kJ / mol - universal gas constant.
In this section, we will look at aggregate states, in which the surrounding matter resides and the forces of interaction between the particles of matter, inherent in each of the aggregate states.
1. Solid state,
2. Liquid state and
3. Gaseous state.
The fourth state of aggregation is often distinguished - plasma.
Sometimes, a plasma state is considered a type of gaseous state.
Plasma - partially or fully ionized gas, most often existing at high temperatures.
Plasma is the most widespread state of matter in the universe, since the matter of stars is in this state.
For everybody aggregate state characteristic features in the nature of the interaction between the particles of a substance, which affects its physical and chemical properties.
Each substance can be in different states of aggregation. At sufficiently low temperatures, all substances are in solid state... But as they heat up, they become liquids, then gases... Upon further heating, they ionize (atoms lose some of their electrons) and pass into the state plasma.
Gas
Gaseous state(from Dutch.gas, goes back to ancient Greek. Χάος ) characterized by very weak bonds between its constituent particles.
The molecules or atoms forming the gas move chaotically and, for the most part of the time, they are at large (in comparison with their size) distances from each other. Therefore the interaction forces between gas particles are negligible.
The main feature of gas is that it fills all the available space without forming a surface. The gases are always mixed. Gas is an isotropic substance, that is, its properties are independent of direction.
In the absence of gravitational forces pressure at all points of the gas the same. In the field of gravitational forces, the density and pressure are not the same at every point, decreasing with height. Accordingly, in the field of gravity, the gas mixture becomes inhomogeneous. Heavy gases tend to sink lower and more lungs- to go up.
Gas has high compressibility- with increasing pressure, its density increases. When the temperature rises, they expand.
When compressed, gas can turn into liquid, but condensation does not occur at any temperature, but at a temperature below the critical temperature. The critical temperature is a characteristic of a particular gas and depends on the forces of interaction between its molecules. So, for example, gas helium can be liquefied only at temperatures below 4.2K.
There are gases that, when cooled, pass into a solid, bypassing the liquid phase. The transformation of a liquid into a gas is called evaporation, and the direct transformation of a solid into a gas is sublimation.
Solid
Solid state in comparison with other states of aggregation characterized by form stability.
Distinguish crystalline and amorphous solids.
Crystalline state of matter
The stability of the shape of solids is due to the fact that the majority of those in a solid state have crystalline structure.
In this case, the distances between the particles of the substance are small, and the forces of interaction between them are large, which determines the stability of the form.
It is easy to be convinced of the crystalline structure of many solids by splitting a piece of matter and examining the resulting fracture. Usually, on a fracture (for example, in sugar, sulfur, metals, etc.), small crystal faces located at different angles are clearly visible, gleaming due to the different reflection of light by them.
In cases where the crystals are very small, the crystal structure of a substance can be established using a microscope.
Crystal shapes
Each substance forms crystals of a completely definite shape.
The variety of crystalline forms can be summarized in seven groups:
1. Triclinnaya(parallelepiped),
2.Monoclinic(a prism with a parallelogram at the base),
3. Rhombic(rectangular parallelepiped),
4. Tetragonal(rectangular parallelepiped with a square at the base),
5. Trigonal,
6. Hexagonal(prism with the base of the correct centered
hexagon),
7. Cubic(cube).
Many substances, in particular iron, copper, diamond, sodium chloride, crystallize in cubic system... The simplest forms of this system are cube, octahedron, tetrahedron.
Magnesium, zinc, ice, quartz crystallize in hexagonal system... The main forms of this system are - hex prisms and bipyramid.
Natural crystals, as well as crystals obtained by artificial means, rarely exactly correspond to theoretical forms. Usually, when the molten substance solidifies, the crystals grow together and therefore the shape of each of them turns out to be not completely correct.
However, no matter how unevenly the crystal develops, no matter how distorted its shape, the angles at which the crystal faces converge for the same substance remain constant.
Anisotropy
The features of crystalline bodies are not limited only to the shape of the crystals. Although the substance in a crystal is completely homogeneous, many of its physical properties - strength, thermal conductivity, attitude to light, etc. - are not always the same in different directions within the crystal. This important feature of crystalline substances is called anisotropy.
Internal structure of crystals. Crystalline lattices.
The external shape of the crystal reflects its internal structure and is due to the correct arrangement of the particles that make up the crystal - molecules, atoms or ions.
This arrangement can be represented as crystal lattice- a lattice frame formed by intersecting straight lines. At the points of intersection of the lines - lattice nodes- the centers of the particles lie.
Depending on the nature of the particles located at the nodes of the crystal lattice, and on what forces of interaction between them prevail in a given crystal, the following types are distinguished crystal lattices:
1.molecular,
2.atomic,
3.ionic and
4.metal.
Molecular and atomic lattices are inherent in substances with a covalent bond, ionic - ionic compounds, metal - metals and their alloys.
Atoms are in the nodes of atomic lattices... They are related to each other covalent bond.
There are relatively few substances with atomic lattices. These include diamond, silicon and some inorganic compounds.
These substances are characterized by high hardness, they are refractory and insoluble in almost any solvents. These properties are due to their strength covalent bond.
Molecules are located at the sites of molecular lattices... They are related to each other intermolecular forces.
There are a lot of substances with a molecular lattice. These include non-metals, with the exception of carbon and silicon, all organic compounds with non-ionic communication and many inorganic compounds.
The forces of intermolecular interaction are much weaker than the forces of covalent bonds, therefore molecular crystals have low hardness, fusible and volatile.
At the sites of the ionic lattices are arranged, alternating positively and negatively charged ions... They are bound to each other by forces electrostatic attraction.
Compounds with ionic bonds that form ionic lattices include most salts and few oxides.
By strength ionic lattices inferior to atomic, but exceed molecular.
Ionic compounds have relatively high melting points. In most cases, their volatility is not great.
At the sites of metal lattices are metal atoms, between which electrons common to these atoms move freely.
The presence of free electrons in the crystal lattices of metals can explain their many properties: plasticity, malleability, metallic luster, high electrical and thermal conductivity
There are substances in the crystals of which two kinds of interactions between particles play a significant role. So, in graphite, carbon atoms are bonded to each other in the same directions. covalent bond, and in others - metal... Therefore, the graphite lattice can be considered as atomic, And How metal.
In many inorganic compounds, for example, in BeO, ZnS, CuCl, the connection between the particles located at the lattice nodes is partially ionic and partly covalent... Therefore, the lattices of such compounds can be regarded as intermediate between ionic and atomic.
Amorphous state of matter
Properties of amorphous substances
Among solids, there are those in the fracture of which no signs of crystals can be found. For example, if you crack a piece of ordinary glass, then its fracture will be smooth and, unlike crystal fractures, it is limited not to flat, but to oval surfaces.
A similar pattern is observed when pieces of resin, glue and some other substances are split. This state of matter is called amorphous.
Differences between crystalline and amorphous bodies is especially pronounced in their attitude to heating.
While the crystals of each substance melt at a strictly defined temperature and at the same temperature there is a transition from a liquid to a solid state, amorphous bodies do not have a constant melting point... When heated, the amorphous body gradually softens, begins to spread and, finally, becomes completely liquid. When cooled, it also gradually hardens.
Due to the absence of a specific melting point, amorphous bodies have a different ability: many of them flow like liquids, i.e. with prolonged action of relatively small forces, they gradually change their shape. For example, a piece of resin, laid on a flat surface, spreads for several weeks in a warm room, taking the shape of a disk.
The structure of amorphous substances
Differences between crystalline and amorphous the state of matter is as follows.
Orderly arrangement of particles in a crystal reflected by the unit cell is retained over large areas of crystals, and in the case of well-formed crystals - in their entirety.
V amorphous bodies orderliness in the arrangement of particles is observed only in very small areas... In addition, in a number of amorphous bodies even this local ordering is only approximate.
This distinction can be summarized as follows:
- crystal structure is characterized by long-range order,
- the structure of amorphous bodies - to the neighbors.
Examples of amorphous substances.
Stable amorphous substances include glass(artificial and volcanic), natural and artificial resins, adhesives, paraffin, wax and etc.
Transition from amorphous to crystalline state.
Some substances can be in both crystalline and amorphous state. Silicon dioxide SiO 2 occurs naturally as well-educated quartz crystals, as well as in the amorphous state ( mineral flint).
Wherein the crystalline state is always more stable... Therefore, a spontaneous transition from a crystalline substance to an amorphous one is impossible, and the reverse transformation - a spontaneous transition from an amorphous state to a crystalline one - is possible and sometimes observed.
An example of such a transformation is devitrification- spontaneous crystallization of glass at elevated temperatures, accompanied by its destruction.
Amorphous state many substances are obtained at a high rate of solidification (cooling) of the liquid melt.
For metals and alloys amorphous state is formed, as a rule, if the melt is cooled in a time of the order of fractions of tens of milliseconds. For glass, a much lower cooling rate is sufficient.
Quartz (SiO 2) also has a low crystallization rate. Therefore, the products cast from it are amorphous. However, natural quartz, which had hundreds and thousands of years to crystallize during the cooling of the earth's crust or deep layers of volcanoes, has a coarse-crystalline structure, in contrast to volcanic glass, frozen on the surface and therefore amorphous.
Liquids
Liquid is an intermediate state between a solid and a gas.
Liquid state is intermediate between gaseous and crystalline. According to some properties, liquids are close to gases, on others - to solids.
With gases, liquids are brought together, first of all, by isotropy and fluidity... The latter determines the ability of the liquid to easily change its shape.
but high density and low compressibility liquids brings them closer to solids.
The ability of liquids to easily change their shape indicates the absence of rigid forces of intermolecular interaction in them.
At the same time, the low compressibility of liquids, which determines the ability to maintain a constant volume at a given temperature, indicates the presence of, although not rigid, but still significant forces of interaction between particles.
The ratio of potential and kinetic energy.
Each state of aggregation is characterized by its own ratio between the potential and kinetic energies of particles of matter.
In solids, the average potential energy of particles is greater than their average kinetic energy. Therefore, in solids, particles occupy certain positions relative to each other and only vibrate relative to these positions.
For gases, the energy ratio is inverse, as a result of which the gas molecules are always in a state of chaotic movement and the adhesion forces between the molecules are practically absent, so that the gas always occupies the entire volume provided to it.
In the case of liquids, the kinetic and potential energies of particles are approximately the same, i.e. particles are connected to each other, but not rigidly. Therefore, liquids are fluid, but have a constant volume at a given temperature.
The structures of liquids and amorphous bodies are similar.
As a result of applying the methods of structural analysis to liquids, it was found that the structure liquids are like amorphous bodies... Most liquids have close order- the number of nearest neighbors for each molecule and their relative position are approximately the same in the entire volume of the liquid.
The degree of ordering of particles is different for different liquids. In addition, it changes with temperature.
At low temperatures, slightly exceeding the melting point of a given substance, the degree of orderliness of the arrangement of the particles of a given liquid is high.
As the temperature rises, it drops and as it heats up, the properties of a liquid are more and more close to those of a gas... When the critical temperature is reached, the distinction between liquid and gas disappears.
Due to the similarity in the internal structure of liquids and amorphous bodies, the latter are often considered as liquids with a very high viscosity, and only substances in a crystalline state are referred to as solids.
By likening amorphous bodies liquids, however, it should be remembered that in amorphous bodies, in contrast to ordinary liquids, particles have insignificant mobility - the same as in crystals.
Aggregate states of matter(from the Latin aggrego - I attach, I connect) - these are states of the same substance, transitions between which correspond to abrupt changes in free energy, density and other physical parameters of the substance.
Gas (French gaz, derived from the Greek chaos - chaos)- it state of aggregation, in which the forces of interaction of its particles filling the entire volume provided to them are negligible. In gases, the intermolecular distances are large and the molecules move almost freely.
Gases can be viewed as significantly superheated or low-saturated vapors. There is steam above the surface of each liquid. When the vapor pressure rises to a certain limit, called the saturated vapor pressure, the evaporation of the liquid stops, as the liquid becomes the same. A decrease in the volume of saturated steam causes portions of the steam rather than an increase in pressure. Therefore, the steam pressure cannot be higher. The saturation state is characterized by the saturation mass contained in 1m mass of saturated steam, which depends on the temperature. Saturated steam can become unsaturated if its volume is increased or the temperature is raised. If the temperature of the steam is much higher than the point corresponding to the given pressure, the steam is called superheated.
Plasma is a partially or fully ionized gas in which the densities of positive and negative charges are practically the same. The sun, stars, clouds of interstellar matter are composed of gases - neutral or ionized (plasma). Unlike other states of aggregation, plasma is a gas of charged particles (ions, electrons) that electrically interact with each other at large distances, but have neither short-range nor long-range orders in the arrangement of particles.
Liquid- This is the state of aggregation of matter, intermediate between solid and gaseous. Liquids have some features of a solid (retains its volume, forms a surface, has a certain tensile strength) and a gas (takes the form of a vessel in which it is located). The thermal motion of molecules (atoms) of a liquid is a combination of small vibrations around equilibrium positions and frequent jumps from one equilibrium position to another. At the same time, slow movements of molecules and their oscillations within small volumes occur, frequent jumps of molecules violate the long-range order in the arrangement of particles and cause fluidity of liquids, and small vibrations around equilibrium positions cause the existence of short-range order in liquids.Liquids and solids, unlike gases, can be viewed as highly condensed media. In them, the molecules (atoms) are located much closer to each other and the interaction forces are several orders of magnitude greater than in gases. Therefore, liquids and solids have a significant limited opportunities for expansion, they certainly cannot occupy an arbitrary volume, and at constant they retain their volume, in whatever volume they are placed. Transitions from a more structured state of aggregation to a less ordered one can also occur continuously. In this regard, instead of the concept of an aggregate state, it is advisable to use a broader concept - the concept of a phase.
Phase is called the set of all parts of the system that have the same chemical composition and being in the same state. This is justified by the simultaneous existence of thermodynamically equilibrium phases in a multiphase system: a liquid with its own saturated vapor; water and ice at the melting point; two immiscible liquids (mixture of water with triethylamine), differing in concentration; the existence of amorphous solids that retain the structure of the liquid (amorphous state).
Amorphous solid state of matter is a kind of supercooled state of a liquid and differs from ordinary liquids by a significantly higher viscosity and numerical values kinetic characteristics.
Crystalline solid state of matter- This is an aggregate state, which is characterized by large forces of interaction between particles of matter (atoms, molecules, ions). Particles of solids vibrate about average equilibrium positions, called the nodes of the crystal lattice; the structure of these substances is characterized by a high degree of ordering (long-range and short-range order) - ordering in the arrangement (coordination order), in the orientation (orientational order) of structural particles, or in the ordering of physical properties (for example, in the orientation of magnetic moments or electric dipole moments). The region of existence of a normal liquid phase for pure liquids, liquid and liquid crystals is limited from the side of low temperatures phase transitions respectively into a solid (crystallization), superfluid and liquid-anisotropic state.
