Main general education

Line UMK A. V. Peryshkin. Physics (7-9)

Introduction: state of aggregation of matter

The mysterious world around us never ceases to amaze. An ice cube thrown into a glass and left at room temperature will turn into a liquid in a matter of minutes, and if this liquid is left on the windowsill for a longer time, it will completely evaporate. This is the easiest way to observe the transitions of one state of aggregation of a substance into another.

State of aggregation - a state of a substance that has certain properties: the ability to maintain shape and volume, to have a long-range or short-range order, and others. When it changes aggregate state of matter there is a change in physical properties, as well as density, entropy and free energy.

How and why do these amazing transformations take place? To understand this, remember that everything around is made up of. Atoms and molecules of various substances interact with each other, and it is the connection between them that determines what is the state of matter of matter.

There are four types of aggregates:

gaseous,

It seems that chemistry reveals its secrets to us in these amazing transformations. However, it is not. The transition from one state of aggregation to another, as well as or diffusion, are physical phenomena, since these transformations do not change the molecules of the substance and their chemical composition is preserved.

gaseous state

At the molecular level, a gas is a randomly moving, colliding with the walls of the vessel and with each other, molecules that practically do not interact with each other. Since the gas molecules are not interconnected, the gas fills the entire volume provided to it, interacting and changing direction only when they hit each other.

Unfortunately, it is impossible to see gas molecules with the naked eye and even with a light microscope. However, the gas can be touched. Of course, if you just try to catch gas molecules flying around in the palm of your hand, then you will not succeed. But surely everyone saw (or did it themselves) how someone pumped air into a car or bicycle tire, and from soft and wrinkled it became inflated and elastic. And the apparent "weightlessness" of gases will be refuted by the experiment described on page 39 of the textbook "Chemistry Grade 7" edited by O.S. Gabrielyan.

This is because the closed limited volume of the tire gets a large number of molecules, which become crowded, and they begin to hit each other and the tire walls more often, and as a result, the total effect of millions of molecules on the walls is perceived by us as pressure.

But if the gas occupies the entire volume provided to it, why then does it not fly off into space and spread throughout the universe, filling interstellar space? So, something still retains and limits the gases by the atmosphere of the planet?

Quite right. And this - gravitational force. In order to break away from the planet and fly away, the molecules need to develop a speed that exceeds the "escape speed" or second space velocity, and the vast majority of molecules move much more slowly.

Then the following question arises: why do gas molecules do not fall to the ground, but continue to fly? It turns out that thanks to solar energy, air molecules have a solid supply of kinetic energy, which allows them to move against the forces of gravity.

The collection contains questions and tasks of various directions: settlement, qualitative and graphic; technical, practical and historical character. Tasks are divided into topics in accordance with the structure of the textbook “Physics. Grade 9 "authors A. V. Peryshkin, E. M. Gutnik and allow you to implement the requirements stated by the Federal State Educational Standards for meta-subject, subject and personal results learning.

liquid state

By increasing the pressure and/or decreasing the temperature, gases can be converted into a liquid state. At the dawn of the 19th century, the English physicist and chemist Michael Faraday succeeded in converting chlorine and carbon dioxide, compressing them at very low temperatures. However, some of the gases did not succumb to scientists at that time, and, as it turned out, it was not a lack of pressure, but an inability to reduce the temperature to the necessary minimum.

Liquid, unlike gas, occupies a certain volume, but it also takes the form of a filled vessel below the surface. Visually, the liquid can be represented as round beads or cereals in a jar. The molecules of a liquid are in close interaction with each other, but freely move relative to each other.

If a drop of water remains on the surface, after a while it will disappear. But we remember that thanks to the law of conservation of mass-energy, nothing disappears and does not disappear without a trace. The liquid will evaporate, i.e. will change its state of aggregation to gaseous.

Evaporation - is the process of transformation of the state of aggregation of a substance, in which molecules, whose kinetic energy exceeds the potential energy of intermolecular interaction, rise from the surface of a liquid or solid.

Evaporation from the surface of solids is called sublimation or sublimation. The easiest way to observe sublimation is to use naphthalene to control moths. If you smell a liquid or a solid, then evaporation is occurring. After all, the nose captures the fragrant molecules of the substance.

Liquids surround a person everywhere. The properties of liquids are also familiar to everyone - this is viscosity, fluidity. When it comes to the shape of a liquid, many people say that a liquid has no definite shape. But this only happens on Earth. Due to the force of gravity, a drop of water is deformed.

However, many have seen astronauts catching water balloons of various sizes in zero gravity. In the absence of gravity, the liquid takes the form of a ball. A provides the liquid with a spherical shape force surface tension. Soap bubbles are a great way to get acquainted with the force of surface tension on Earth.

Another property of a liquid is viscosity. Viscosity depends on pressure, chemical composition and temperature. Most liquids obey Newton's law of viscosity, discovered in the 19th century. However, there are a number of highly viscous liquids that, under certain conditions, begin to behave like solids and do not obey Newton's law of viscosity. Such solutions are called non-Newtonian fluids. The simplest example of a non-Newtonian fluid is a suspension of starch in water. If you act on a non-Newtonian fluid with mechanical forces, the fluid will begin to take on the properties of solids and behave like a solid.

Solid state

If, in a liquid, unlike a gas, the molecules no longer move randomly, but around certain centers, then in the solid state of matter atoms and molecules have a clear structure and look like lined up soldiers on parade. And thanks to the crystal lattice, solids occupy a certain volume and have a constant shape.

Under certain conditions, substances that are in the state of aggregation of a liquid can turn into a solid, and solids, on the contrary, when heated, melt and turn into a liquid.

This is because when heated, the internal energy increases, respectively, the molecules begin to move faster, and when the melting temperature is reached, the crystal lattice begins to break down and the aggregate state of the substance changes. For most crystalline bodies, the volume increases during melting, but there are exceptions, for example, ice, cast iron.

Depending on the type of particles that form the crystal lattice of a solid, the following structure is distinguished:

molecular

metal.

For some substances change in aggregate states occurs easily, as, for example, with water, other substances require special conditions (pressure, temperature). But in modern physics, scientists distinguish one more independent state of matter - plasma.

Plasma - ionized gas with the same density of both positive and negative charges. In wildlife, plasma is found in the sun, or during a lightning flash. The northern lights and even the familiar bonfire, which warms us with its warmth during a foray into nature, also refers to plasma.

Artificially created plasma adds brightness to any city. Neon advertising lights are just low-temperature plasma in glass tubes. Conventional fluorescent lamps are also filled with plasma.

Plasma is divided into low-temperature - with an ionization degree of about 1% and a temperature of up to 100 thousand degrees, and high-temperature - ionization of about 100% and a temperature of 100 million degrees (this is the state in which plasma in stars is).

Low-temperature plasma in fluorescent lamps familiar to us is widely used in everyday life.

High temperature plasma is used in reactions thermonuclear fusion and scientists do not lose hope of using it as a substitute for atomic energy, but the control in these reactions is very difficult. And an uncontrolled thermonuclear reaction proved to be a weapon of colossal power when, on August 12, 1953, the USSR tested a thermonuclear bomb.

Buy

To check the assimilation of the material, we offer a small test.

1. What does not apply to states of aggregation:

liquid

light +

2. The viscosity of Newtonian fluids is subject to:

Boyle-Mariotte law

the law of Archimedes

Newton's law of viscosity +

3. Why the Earth's atmosphere does not fly away into outer space:

because gas molecules cannot develop the second cosmic velocity

because the gravity of the earth acts on the gas molecules +

both answers are correct

4. What does not apply to amorphous substances:

• sealing wax

• iron +

5. When cooling, the volume increases at:

• ice +

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Introduction

1. Aggregate state of matter - gas

2. Aggregate state of matter - liquid

3. Aggregate state of matter - solid

4. The fourth state of matter is plasma

Conclusion

List of used literature

Introduction

As you know, many substances in nature can be in three states: solid, liquid and gaseous.

The interaction of particles of matter in the solid state is most pronounced. The distance between molecules is approximately equal to their own sizes. This leads to a sufficiently strong interaction, which practically deprives the particles of the opportunity to move: they oscillate around a certain equilibrium position. They retain their shape and volume.

The properties of liquids are also explained by their structure. Particles of matter in liquids interact less intensively than in solids, and therefore they can change their location abruptly - liquids do not retain their shape - they are fluid.

A gas is a collection of molecules moving randomly in all directions independently of each other. Gases do not have their own shape, they occupy the entire volume provided to them and are easily compressed.

There is another state of matter - plasma.

The purpose of this work is to consider the existing aggregate states of matter, to identify all their advantages and disadvantages.

To do this, it is necessary to perform and consider the following aggregate states:

2. fluids

3. solids

3. Aggregate state of matter - solid

Solid, one of the four states of aggregation of matter, which differs from other states of aggregation (liquids, gases, plasmas) the stability of the form and the nature of the thermal motion of atoms that make small vibrations around the equilibrium positions. Along with the crystalline state of T. t., there is an amorphous state, including the glassy state. Crystals are characterized by long-range order in the arrangement of atoms. There is no long-range order in amorphous bodies.

In this section, we will look at aggregate states, in which the matter surrounding us resides and the forces of interaction between the particles of matter, characteristic of each of the aggregate states.

1. Solid State,

2. liquid state And

3. gaseous state.

Often a fourth state of aggregation is distinguished - plasma.

Sometimes, the plasma state is considered one of the types of gaseous state.

Plasma - partially or fully ionized gas, most often present at high temperatures.

Plasma is the most common state of matter in the universe, since the matter of stars is in this state.

For each state of aggregation 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 (the atoms lose some of their electrons) and pass into the state plasma.

Gas

gaseous state(from Dutch. gas, goes back to other Greek. Χάος ) characterized by very weak bonds between its constituent particles.

The molecules or atoms that form the gas move randomly and, at the same time, they are at large (in comparison with their sizes) distances from each other for the majority of the time. Consequently interaction forces between gas particles are negligible.

The main feature of the gas is that it fills all available space without forming a surface. Gases always mix. Gas is an isotropic substance, that is, its properties do not depend on direction.

In the absence of gravity pressure the same at all points in the gas. In the field of gravitational forces, density and pressure are not the same at each point, decreasing with height. Accordingly, in the field of gravity, the mixture of gases becomes inhomogeneous. heavy gases tend to settle lower and more lungs- to go up.

The gas has a high compressibility- when the pressure increases, its density increases. As the temperature rises, they expand.

When compressed, a gas can turn into a 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 only be liquefied at temperatures below 4.2K.

There are gases that, when cooled, pass into a solid body, 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 called sublimation.

Solid

Solid State in comparison with other states of aggregation characterized by shape stability.

Distinguish crystalline And amorphous solids.

Crystalline state of matter

The stability of the shape of solids is due to the fact that most of the solids have crystalline structure.

In this case, the distances between the particles of the substance are small, and the interaction forces between them are large, which determines the stability of the form.

It is easy to verify the crystalline structure of many solids by splitting a piece of matter and examining the resulting fracture. Usually, at a break (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 the substance can be established using a microscope.

Crystal forms

Each substance forms crystals perfectly defined form.

The variety of crystalline forms can be summarized in seven groups:

1. Triclinic(parallelepiped),

2.Monoclinic(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 right 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 hexagonal prisms and bipyramid.

Natural crystals, as well as crystals obtained artificially, rarely correspond exactly to theoretical forms. Usually, when the molten substance solidifies, the crystals grow together and therefore the shape of each of them is not quite correct.

However, no matter how unevenly the crystal develops, no matter how distorted its shape, the angles at which the crystal faces converge in the same substance remain constant.

Anisotropy

Features of crystalline bodies are not limited to the shape of crystals. Although the substance in a crystal is perfectly homogeneous, many of its physical properties - strength, thermal conductivity, relation to light, etc. - are not always the same in various directions within the crystal. This important feature of crystalline substances is called anisotropy.

Internal structure of crystals. Crystal lattices.

The external shape of a 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 spatial frame formed by intersecting straight lines. At the points of intersection of the lines - lattice nodes are the centers of the particles.

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 - in ionic compounds, metallic - in metals and their alloys.

Atomic crystal lattices

At the nodes of atomic lattices are atoms. They are connected to each other covalent bond.

There are relatively few substances that have atomic lattices. They belong to diamond, silicon and some don't organic compounds.

These substances are characterized by high hardness, they are refractory and practically insoluble in any solvents. These properties are due to their durability. covalent bond.

Molecular crystal lattices

Molecules are located at the nodes of molecular lattices. They are connected to each other intermolecular forces.

There are a lot of substances with a molecular lattice. They belong to nonmetals, with the exception of carbon and silicon, all organic compounds with non-ionic bond 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.

Ionic crystal lattices

In the nodes of ionic lattices, positively and negatively charged ions are located, alternating. They are connected to each other by forces electrostatic attraction.

Ionic compounds that form ionic lattices include most salts and a small number of oxides.

By strength ionic lattices inferior to atomic, but exceed molecular.

Ionic compounds have relatively high melting points. Their volatility in most cases is not great.

Metallic crystal lattices

At the nodes of metal lattices there 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 many of their properties: plasticity, malleability, metallic luster, high electrical and thermal conductivity.

There are substances in whose crystals two kinds of interactions between particles play a significant role. So, in graphite, carbon atoms are connected to each other in the same directions. covalent bond, and in others metallic. Therefore, the graphite lattice can also be considered as nuclear, And How metal.

In many inorganic compounds, for example, in BeO, ZnS, CuCl, the connection between the particles located at the lattice sites is partially ionic, and partly covalent. Therefore, lattices of such compounds can be considered as intermediate between ionic And atomic.

Amorphous state of matter

Properties of amorphous substances

Among solid bodies there are those in which no signs of crystals can be found in the fracture. For example, if you break a piece of ordinary glass, then its break will be smooth and, unlike the breaks of crystals, it is limited not by flat, but by oval surfaces.

A similar picture is observed when splitting pieces of resin, glue and some other substances. This state of matter is called amorphous.

Difference between crystalline And amorphous bodies is particularly pronounced in their relation to heating.

While the crystals of each substance melt at a strictly defined temperature and at the same temperature a transition from a liquid state to a solid occurs, 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 lack 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 placed on a flat surface spreads in a warm room for several weeks, taking the form of a disk.

The structure of amorphous substances

Difference between crystalline and amorphous state of matter is as follows.

Ordered arrangement of particles in a crystal, reflected by the unit cell, is preserved in large areas of crystals, and in the case of well-formed crystals - in their entirety.

In amorphous bodies, order in the arrangement of particles is observed only in very small areas. Moreover, in a number of amorphous bodies even this local ordering is only approximate.

This difference can be summarized as follows:

• crystal structure is characterized by long-range order,
• structure of amorphous bodies - near.

Examples of amorphous substances.

Stable amorphous substances include glass(artificial and volcanic), natural and artificial resins, glues, paraffin, wax and etc.

Transition from an amorphous state to a crystalline one.

Some substances can be in both crystalline and amorphous states. Silicon dioxide SiO 2 occurs in nature in the form of well-formed quartz crystals, as well as in the amorphous state ( flint mineral).

Wherein the crystalline state is always more stable. Therefore, a spontaneous transition from a crystalline to an amorphous substance 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 is 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 for a time on the order of fractions or tens of milliseconds. For glasses, a much lower cooling rate is sufficient.

Quartz (SiO2) 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-grained structure, in contrast to volcanic glass, which has frozen on the surface and is 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, according to others - to solid bodies.

With gases, liquids are brought together, first of all, by their isotropy And fluidity. The latter determines the ability of the liquid to easily change its shape.

However high density And low compressibility liquids brings them closer to solid bodies.

The ability of liquids to easily change their shape indicates the absence of hard 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, 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 the 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 oscillate relative to these positions.

For gases, the energy ratio is reversed, as a result of which the gas molecules are always in a state of chaotic motion and there are practically no cohesive forces between the molecules, 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 the application of structural analysis methods to liquids, it was found that the structure liquids are like amorphous bodies. Most liquids have short range order is the number of nearest neighbors for each molecule and their mutual arrangement approximately the same throughout the volume of the liquid.

The degree of ordering of particles in different liquids is different. In addition, it changes with temperature.

At low temperatures slightly above the melting point of a given substance, the degree of order in the arrangement of the particles of a given liquid is high.

As the temperature rises, it decreases and as the liquid heats up, the properties of the liquid more and more approach the properties of the 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 the crystalline state are classified as solids.

Likening amorphous bodies liquids, however, it should be remembered that in amorphous bodies, unlike ordinary liquids, particles have a slight mobility - the same as in crystals.

State of aggregation- a state of matter characterized by certain qualitative properties: the ability or inability to maintain volume and shape, the presence or absence of long-range and short-range order, and others. A change in the state of aggregation may be accompanied by a jump-like change in free energy, entropy, density, and other basic physical properties.
There are three main states of aggregation: solid, liquid and gas. Sometimes it is not entirely correct to classify plasma as a state of aggregation. There are other states of aggregation, for example, liquid crystals or Bose-Einstein condensate. Changes in the state of aggregation are thermodynamic processes called phase transitions. The following varieties are distinguished: from solid to liquid - melting; from liquid to gaseous - evaporation and boiling; from solid to gaseous - sublimation; from gaseous to liquid or solid - condensation; from liquid to solid - crystallization. A distinctive feature is the absence of a sharp boundary of the transition to the plasma state.
Aggregate state definitions are not always strict. So, there are amorphous bodies that retain the structure of a liquid and have little fluidity and the ability to retain shape; liquid crystals are fluid, but at the same time they have some properties of solids, in particular, they can polarize electromagnetic radiation passing through them. To describe various states in physics, a broader concept of a thermodynamic phase is used. Phenomena that describe transitions from one phase to another are called critical phenomena.
The aggregate state of a substance depends on the physical conditions in which it is located, mainly on temperature and pressure. The determining quantity is the ratio of the average potential energy of the interaction of molecules to their average kinetic energy. So, for a solid body this ratio is greater than 1, for gases it is less than 1, and for liquids it is approximately equal to 1. The transition from one state of aggregation of a substance to another is accompanied by an abrupt change in the value of this ratio, associated with an abrupt change in intermolecular distances and intermolecular interactions. In gases, the intermolecular distances are large, the molecules almost do not interact with each other and move almost freely, filling the entire volume. In liquids and solids - condensed media - molecules (atoms) are located much closer to each other and interact more strongly.
This leads to the preservation of liquids and solids of their volume. However, the nature of the movement of molecules in solids and liquids is different, which explains the difference in their structure and properties.
In solids in a crystalline state, atoms only vibrate near the nodes of the crystal lattice; the structure of these bodies is characterized by a high degree of order - long-range and short-range order. The thermal motion of molecules (atoms) of a liquid is a combination of small fluctuations around equilibrium positions and frequent jumps from one equilibrium position to another. The latter determine the existence in liquids of only short-range order in the arrangement of particles, as well as their inherent mobility and fluidity.
A. Solid- a state characterized by the ability to maintain volume and shape. Atoms of a solid body make only small vibrations around the state of equilibrium. There is both long-range and short-range order.
b. Liquid- a state of matter in which it has low compressibility, that is, it retains its volume well, but is not able to retain its shape. The liquid easily takes the shape of the vessel in which it is placed. Atoms or molecules of a liquid vibrate near the equilibrium state, locked by other atoms, and often jump to other free places. There is only short-range order.
Melting- this is the transition of a substance from a solid state of aggregation (see Aggregate states of matter) to a liquid. This process occurs during heating, when a certain amount of heat +Q is imparted to the body. For example, the low-melting metal lead passes from a solid state to a liquid state if it is heated to a temperature of 327 ° C. Lead easily melts on a gas stove, for example, in a stainless steel spoon (it is known that the flame temperature of a gas burner is 600-850 ° C, and the temperature melting of steel - 1300-1500°C).
If, while melting lead, its temperature is measured, then it can be found that at first it gradually increases, but after a certain moment it remains constant, despite further heating. This moment corresponds to melting. The temperature is held constant until all the lead has melted, and only then does it begin to rise again. When liquid lead is cooled, the opposite is observed: the temperature drops until solidification begins and remains constant all the time until the lead passes into the solid phase, and then decreases again.
All pure substances behave in the same way. The constancy of temperature during melting is of great practical importance, since it allows calibrating thermometers, making fuses and indicators that melt at a strictly specified temperature.
Atoms in a crystal vibrate about their equilibrium positions. As the temperature rises, the oscillation amplitude increases and reaches a certain critical value, after which the crystal lattice is destroyed. This requires additional thermal energy, so during the melting process the temperature does not rise, although heat continues to flow.
The melting point of a substance depends on pressure. For substances whose volume increases during melting (and the vast majority of them), an increase in pressure increases the melting point and vice versa. At water, the volume decreases during melting (therefore, when it freezes, water breaks pipes), and when pressure increases, ice melts at a lower temperature. Bismuth, gallium and some grades of cast iron behave in a similar way.
V. Gas- a condition characterized by good compressibility, the lack of the ability to maintain both volume and shape. Gas tends to occupy the entire volume provided to it. Atoms or molecules of a gas behave relatively freely, the distances between them are much greater than their size.
Plasma, often referred to as a state of aggregation of matter, differs from gas in a high degree of ionization of atoms. Most of the baryonic matter (by mass approx. 99.9%) in the Universe is in the plasma state.
g. C supercritical fluid- Occurs with a simultaneous increase in temperature and pressure to a critical point, at which the density of the gas is compared with the density of the liquid; in this case, the boundary between the liquid and gaseous phases disappears. The supercritical fluid has an exceptionally high dissolving power.
d. Bose-Einstein condensate- is obtained by cooling the Bose gas to temperatures close to absolute zero. As a result, some of the atoms are in a state with strictly zero energy (that is, in the lowest possible quantum state). The Bose-Einstein condensate exhibits a number of quantum properties such as superfluidity and Fischbach resonance.
e. Fermionic condensate- is a Bose-condensation in the BCS mode of "atomic Cooper pairs" in gases consisting of fermion atoms. (In contrast to the traditional mode of Bose-Einstein condensation of compound bosons).
Such fermionic atomic condensates are "relatives" of superconductors, but with a critical temperature of the order of room temperature and above.
Degenerate matter - Fermi gas 1st stage Electron degenerate gas, observed in white dwarfs, plays an important role in the evolution of stars. The 2nd stage is the neutron state where 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. Perhaps deconfinement occurs in two stages.
With a further unlimited increase in pressure without an increase in temperature, the substance collapses into black hole.
With a simultaneous increase in both pressure and temperature, other particles are added to quarks and gluons. What happens to matter, space and time at temperatures close to the Planck temperature is still unknown.
Other states
During deep cooling, some (by no means all) substances pass into a superconducting or superfluid state. These states, of course, are separate thermodynamic phases, but they hardly deserve to be called new aggregate states of matter due to their non-universality.
Inhomogeneous substances such as pastes, gels, suspensions, aerosols, etc., which under certain conditions exhibit the properties of both solids and liquids and even gases, are usually classified as dispersed materials, and not to any specific aggregate states of matter .

State of aggregation- this is a state of matter in a certain range of temperatures and pressures, characterized by properties: the ability (solid) 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 isolated.

IN 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.

IN 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, but there is also no mutual orientation of these sections. 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.

IN solid substance, the order of arrangement of atoms becomes strictly defined, regularly ordered, the forces of interaction 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 distinguished 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. characteristic feature crystalline body is the ability to retain 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 body to be aligned 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 a given 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 component H 2 O, therefore largest number there are three phases that can simultaneously be in equilibrium (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, synthesizing various substances, they widely use plasma light sources, and the use of plasma in thermonuclear power plants etc.