In what state of aggregation is the substance? The fourth state of matter
State of aggregation- this is the state of a substance 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 distinguished.
IN gaseous In this state, the distance between the atoms and molecules of the substance is large, the interaction forces are small and the particles, moving chaotically in space, have a large kinetic energy that exceeds the potential energy. A material in a gaseous state has neither its own shape nor volume. Gas fills all available space. This state is typical for substances with low density.
IN liquid state, only short-range order of atoms or molecules is preserved, when individual areas with an ordered arrangement of atoms periodically appear in the volume of the substance, but the mutual orientation of these areas is also absent. Short-range order is unstable and under the influence of thermal vibrations of atoms it can either disappear or appear again. Liquid molecules do not have a specific 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 its volume. The liquid can occupy only part of the volume of the vessel, but flow freely over the entire surface of the vessel. The liquid state is usually considered intermediate between a solid and a gas.
IN hard In a substance, the arrangement of atoms becomes strictly defined, naturally ordered, the forces of interaction between 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 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, var, which are outwardly in a solid state, although in fact they flow slowly, like a liquid. Amorphous bodies, unlike crystalline ones, do not have a specific melting point. Amorphous solids occupy an intermediate position between crystalline solids and liquids.
Most solids have crystalline a structure characterized by the orderly arrangement of atoms or molecules in space. The crystal structure is characterized by long-range order, when the elements of the structure are periodically repeated; with short-range order there is no such correct repetition. A characteristic feature of a crystalline body is the ability to maintain its shape. A sign of an ideal crystal, the model of which is a spatial lattice, is the property of symmetry. Symmetry refers to the theoretical ability of the crystal lattice of a solid body to align with itself when its points are mirrored from a certain plane, called the plane of symmetry. The symmetry of the external shape reflects the symmetry of the internal structure of the crystal. For example, all metals have a crystalline structure and are characterized by two types of symmetry: cubic and hexagonal.
In amorphous structures with a disordered distribution of atoms, the properties of the substance in different directions are the same, that is, glassy (amorphous) substances are isotropic.
All crystals are characterized by anisotropy. In crystals, the distances between atoms are ordered, but in different directions the degree of ordering may not be the same, which leads to differences 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 properties of objects that have a certain material volume: sizes - from several millimeters to tens of centimeters. These objects with a structure identical to the crystal cell are called single crystals.
Anisotropy of properties manifests itself 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, the molecules of which can be arranged in an orderly manner with the formation of supramolecular structures in the form of packs, coils (globules), fibrils, etc., occurs in a certain temperature range. The complex structure of molecules and their aggregates determines the specific behavior of polymers when heated. They cannot go into a liquid state with low viscosity and 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 when the temperature changes, which manifests itself in the process of deformation of the polymer. In Fig. Figure 9 shows the dependence of deformation on temperature.
Rice. 9 Thermomechanical curve of an amorphous polymer: t c , t T, t p - glass transition, fluidity and onset of chemical decomposition temperatures, respectively; I - III - zones of glassy, highly elastic and viscous flow 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 transforms into a highly elastic state ( zone II), and its deformation in the glassy and highly elastic states is reversible. Heating above the pour point t t transfers the polymer to a viscous flow state ( zone III). The deformation of a polymer in a viscous flow state is irreversible. An amorphous polymer with a spatial (network, cross-linked) structure does not have a viscous flow state; the temperature region of the highly elastic state expands to the temperature of polymer decomposition t R. This behavior is typical for materials such as rubber.
The temperature of a substance in any state of aggregation characterizes the average kinetic energy of its particles (atoms and molecules). These particles in bodies possess mainly the kinetic energy of vibrational movements 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 energetically that the rigid bonds in the polymer are broken and the crystals are destroyed - they turn into a liquid state. The temperature at which the 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 an individual 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, substances are in thermodynamic equilibrium. A change in the state of aggregation can be accompanied by an abrupt 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 copper melts (1083 o C) it turns into a liquid in which the atoms have only short-range order. At a pressure of 1 atm, copper boils at 2310 o C and turns into gaseous copper with randomly arranged copper atoms. At the melting point, the saturated vapor pressures of the crystal and the 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 a system, separated from other parts physical interface boundaries (in cast iron: graphite + iron grains; in water with ice: ice + water).Components systems are the different phases that make up a given system. System components- these are the substances that form all the phases (components) of a given system.
Materials consisting of two or more phases are dispersed systems Dispersed 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 low temperatures (at high temperatures gelatin turns into a sol). A hydrosol is a dispersion in water, an aerosol is a dispersion in air.
Status 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 describing transformations is limited to considering the equilibrium state. Equilibrium state thermodynamic system is characterized by the invariance of thermodynamic parameters (temperature and concentration, since in technological treatments R= const) in time and the absence of flows of energy and matter in it - with constant external conditions. Phase equilibrium- the equilibrium state of a thermodynamic system consisting of two or more phases.
To mathematically describe the equilibrium conditions of a system, there is phase rule, derived by Gibbs. It connects the number of phases (F) and components (K) in an equilibrium system with the variability 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), to which various arbitrary (in a certain range) values can be given so that new phases do not appear and old phases do not disappear .
Gibbs phase rule equation:
C = 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., only one external parameter can be changed (for example, temperature);
For a three-phase state, the number of degrees of freedom is zero, i.e., the temperature cannot be changed 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 is completed and one phase remains - the solid crystal. After the end of crystallization (Ф = 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 phase diagram. The phase diagram of water is a system with one component H 2 O, therefore the largest number of phases that can simultaneously be in equilibrium is three (Fig. 10). These three phases are liquid, ice, steam. The number of degrees of freedom in this case is zero, i.e. Neither the pressure nor the temperature can be changed without any of the phases disappearing. 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 three phases coexist is called the triple point ( O).
Curve OS separates the vapor and liquid regions and represents the dependence of saturated water vapor pressure on temperature. The OS 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 boiling curve.
Fig 10 Diagram of the state of water
Curve OB separates the liquid region from the ice region. It is the solid-liquid equilibrium curve and is called the melting curve. This curve shows those interrelated pairs of temperature and pressure values at which ice and liquid water are in equilibrium.
Curve O.A. called a sublimation curve and shows the interrelated pairs of pressure and temperature values at which ice and water vapor are in equilibrium.
A phase diagram is a visual way of representing the regions of existence of different phases depending on external conditions, such as pressure and temperature. State diagrams are actively used in materials science at various technological stages of product production.
A liquid differs from a crystalline solid by low viscosity values (internal friction of molecules) and high fluidity values (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 interactions 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, 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 dissolved substance 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.
When cooled under conditions of low rate of formation of crystallization centers and a strong increase in viscosity, a glassy state may occur. Glasses are isotropic solid materials obtained by supercooling molten inorganic and organic compounds.
There are many known substances whose transition from a crystalline state to an isotropic liquid occurs through an intermediate liquid crystalline state. It is typical for substances whose molecules have the shape of long rods (rods) with an asymmetric structure. Such phase transitions, accompanied by thermal effects, cause abrupt changes 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 wristwatches, visual equipment, etc.
The main states of aggregation include plasma- partially or fully ionized gas. Based on the method of formation, two types of plasma are distinguished: thermal, which occurs when gas is heated to high temperatures, and gaseous, which is formed during electrical discharges in a gaseous environment.
Plasma-chemical processes have taken a strong place in a number of branches of technology. They are used for cutting and welding refractory metals, synthesis of various substances, plasma light sources are widely used, the use of plasma in thermonuclear power plants is promising, etc.
Questions about what a state of aggregation is, what features and properties solids, liquids and gases have, are discussed in several training courses. There are three classical states of matter, with their own characteristic structural features. Their understanding is an important point in understanding the sciences of the Earth, living organisms, and industrial activities. These questions are studied by physics, chemistry, geography, geology, physical chemistry and other scientific disciplines. Substances that, under certain conditions, are in one of three basic types of state can change with an increase or decrease in temperature and pressure. Let us consider possible transitions from one state of aggregation to another, as they occur in nature, technology and everyday life.
What is a state of aggregation?
The word of Latin origin "aggrego" translated into Russian means "to join". The scientific term refers to the state of the same body, substance. The existence of solids, gases and liquids at certain temperatures and different pressures is characteristic of all the shells of the Earth. In addition to the three basic states of aggregation, there is also a fourth. At elevated temperature and constant pressure, the gas turns into plasma. To better understand what a state of aggregation is, it is necessary to remember the smallest particles that make up substances and bodies.
The diagram above shows: a - gas; b—liquid; c is a solid body. In such pictures, circles indicate the structural elements of substances. This is a symbol; in fact, atoms, molecules, and ions are not solid balls. Atoms consist of a positively charged nucleus around which negatively charged electrons move at high speed. Knowledge about the microscopic structure of matter helps to better understand the differences that exist between different aggregate forms.
Ideas about the microcosm: from Ancient Greece to the 17th century
The first information about the particles that make up physical bodies appeared in Ancient Greece. The thinkers Democritus and Epicurus introduced such a concept as the atom. They believed that these smallest indivisible particles of different substances have a shape, certain sizes, and are capable of movement and interaction with each other. Atomism became the most advanced teaching of ancient Greece for its time. But its development slowed down in the Middle Ages. Since then scientists were persecuted by the Inquisition of the Roman Catholic Church. Therefore, until modern times, there was no clear concept of what the state of matter was. Only after the 17th century did scientists R. Boyle, M. Lomonosov, D. Dalton, A. Lavoisier formulate the provisions of the atomic-molecular theory, which have not lost their significance today.
Atoms, molecules, ions - microscopic particles of the structure of matter
A significant breakthrough in understanding the microworld occurred in the 20th century, when the electron microscope was invented. Taking into account the discoveries made by scientists earlier, it was possible to put together a coherent picture of the microworld. Theories that describe the state and behavior of the smallest particles of matter are quite complex; they relate to the field of To understand the characteristics of different aggregate states of matter, it is enough to know the names and characteristics of the main structural particles that form different substances.
- Atoms are chemically indivisible particles. They are preserved in chemical reactions, but are destroyed in nuclear reactions. Metals and many other substances of atomic structure have a solid state of aggregation under normal conditions.
- Molecules are particles that are broken down and formed in chemical reactions. oxygen, water, carbon dioxide, sulfur. The physical state of oxygen, nitrogen, sulfur dioxide, carbon, oxygen under normal conditions is gaseous.
- Ions are the charged particles that atoms and molecules become when they gain or lose electrons—microscopic negatively charged particles. Many salts have an ionic structure, for example table salt, iron sulfate and copper sulfate.
There are substances whose particles are located in space in a certain way. The ordered mutual position of atoms, ions, and molecules is called a crystal lattice. Typically, ionic and atomic crystal lattices are characteristic of solids, molecular - for liquids and gases. Diamond is distinguished by its high hardness. Its atomic crystal lattice is formed by carbon atoms. But soft graphite also consists of atoms of this chemical element. Only they are located differently in space. The usual state of aggregation of sulfur is solid, but at high temperatures the substance turns into a liquid and an amorphous mass.
Substances in a solid state of aggregation
Solids under normal conditions retain their volume and shape. For example, a grain of sand, a grain of sugar, salt, a piece of rock or metal. If you heat sugar, the substance begins to melt, turning into a viscous brown liquid. Let's stop heating and we'll get a solid again. This means that one of the main conditions for the transition of a solid into a liquid is its heating or an increase in the internal energy of the particles of the substance. The solid state of aggregation of salt, which is used for food, can also be changed. But to melt table salt, a higher temperature is needed than when heating sugar. The fact is that sugar consists of molecules, and table salt consists of charged ions that are more strongly attracted to each other. Solids in liquid form do not retain their shape because the crystal lattices are destroyed.
The liquid aggregate state of the salt upon melting is explained by the breaking of bonds between the ions in the crystals. Charged particles that can carry electrical charges are released. Molten salts conduct electricity and are conductors. In the chemical, metallurgical and engineering industries, solids are converted into liquids to produce new compounds or give them different forms. Metal alloys have become widespread. There are several ways to obtain them, associated with changes in the state of aggregation of solid raw materials.
Liquid is one of the basic states of aggregation
If you pour 50 ml of water into a round-bottomed flask, you will notice that the substance will immediately take the shape of a chemical vessel. But as soon as we pour the water out of the flask, the liquid will immediately spread over the surface of the table. The volume of water will remain the same - 50 ml, but its shape will change. The listed features are characteristic of the liquid form of existence of matter. Many organic substances are liquids: alcohols, vegetable oils, acids.
Milk is an emulsion, i.e. a liquid containing droplets of fat. A useful liquid resource is oil. It is extracted from wells using drilling rigs on land and in the ocean. Sea water is also a raw material for industry. Its difference from fresh water in rivers and lakes lies in the content of dissolved substances, mainly salts. When evaporating from the surface of reservoirs, only H 2 O molecules pass into a vapor state, dissolved substances remain. Methods for obtaining useful substances from sea water and methods for its purification are based on this property.
When the salts are completely removed, distilled water is obtained. It boils at 100°C and freezes at 0°C. Brines boil and turn into ice at other temperatures. For example, water in the Arctic Ocean freezes at a surface temperature of 2 °C.
The physical state of mercury under normal conditions is liquid. This silvery-gray metal is commonly used to fill medical thermometers. When heated, the mercury column rises on the scale and the substance expands. Why is alcohol tinted with red paint used, and not mercury? This is explained by the properties of liquid metal. At 30-degree frosts, the state of aggregation of mercury changes, the substance becomes solid.
If the medical thermometer breaks and the mercury spills out, then collecting the silver balls with your hands is dangerous. It is harmful to inhale mercury vapor; this substance is very toxic. In such cases, children need to turn to their parents and adults for help.
Gaseous state
Gases are unable to maintain either their volume or shape. Let's fill the flask to the top with oxygen (its chemical formula is O2). As soon as we open the flask, the molecules of the substance will begin to mix with the air in the room. This occurs due to Brownian motion. Even the ancient Greek scientist Democritus believed that particles of matter are in constant motion. In solids, under normal conditions, atoms, molecules, and ions do not have the opportunity to leave the crystal lattice or free themselves from bonds with other particles. This is only possible when a large amount of energy is supplied from outside.
In liquids, the distance between particles is slightly greater than in solids; they require less energy to break intermolecular bonds. For example, the liquid state of oxygen is observed only when the gas temperature decreases to −183 °C. At −223 °C, O 2 molecules form a solid. When the temperature rises above these values, oxygen turns into gas. It is in this form that it is found under normal conditions. Industrial enterprises operate special installations for separating atmospheric air and obtaining nitrogen and oxygen from it. First, the air is cooled and liquefied, and then the temperature is gradually increased. Nitrogen and oxygen turn into gases under different conditions.
The Earth's atmosphere contains 21% by volume oxygen and 78% nitrogen. These substances are not found in liquid form in the gaseous envelope of the planet. Liquid oxygen is light blue in color and is used to fill cylinders at high pressure for use in medical settings. In industry and construction, liquefied gases are needed to carry out many processes. Oxygen is needed for gas welding and cutting metals, and in chemistry for oxidation reactions of inorganic and organic substances. If you open the valve of an oxygen cylinder, the pressure decreases and the liquid turns into gas.
Liquefied propane, methane and butane are widely used in energy, transport, industry and household activities. These substances are obtained from natural gas or during cracking (splitting) of petroleum feedstock. Carbon liquid and gaseous mixtures play an important role in the economies of many countries. But oil and natural gas reserves are severely depleted. According to scientists, this raw material will last for 100-120 years. An alternative source of energy is air flow (wind). Fast-flowing rivers and tides on the shores of seas and oceans are used to operate power plants.
Oxygen, like other gases, can be in the fourth state of aggregation, representing a plasma. The unusual transition from solid to gaseous state is a characteristic feature of crystalline iodine. The dark purple substance undergoes sublimation - it turns into a gas, bypassing the liquid state.
How are transitions made from one aggregate form of matter to another?
Changes in the aggregate state of substances are not associated with chemical transformations, these are physical phenomena. As the temperature increases, many solids melt and turn into liquids. A further increase in temperature can lead to evaporation, that is, to the gaseous state of the substance. In nature and economy, such transitions are characteristic of one of the main substances on Earth. Ice, liquid, steam are states of water under different external conditions. The compound is the same, its formula is H 2 O. At a temperature of 0 ° C and below this value, water crystallizes, that is, turns into ice. As the temperature rises, the resulting crystals are destroyed - the ice melts, and liquid water is again obtained. When it is heated, evaporation is formed - the transformation of water into gas - even at low temperatures. For example, frozen puddles gradually disappear because the water evaporates. Even in frosty weather, wet laundry dries, but this process takes longer than on a hot day.
All of the listed transitions of water from one state to another are of great importance for the nature of the Earth. Atmospheric phenomena, climate and weather are associated with the evaporation of water from the surface of the World Ocean, the transfer of moisture in the form of clouds and fog to land, and precipitation (rain, snow, hail). These phenomena form the basis of the World water cycle in nature.
How do the aggregate states of sulfur change?
Under normal conditions, sulfur is bright shiny crystals or light yellow powder, i.e. it is a solid substance. The physical state of sulfur changes when heated. First, when the temperature rises to 190 °C, the yellow substance melts, turning into a mobile liquid.
If you quickly pour liquid sulfur into cold water, you get a brown amorphous mass. With further heating of the sulfur melt, it becomes more and more viscous and darkens. At temperatures above 300 °C, the state of aggregation of sulfur changes again, the substance acquires the properties of a liquid and becomes mobile. These transitions arise due to the ability of the atoms of an element to form chains of different lengths.
Why can substances be in different physical states?
The state of aggregation of sulfur, a simple substance, is solid under ordinary conditions. Sulfur dioxide is a gas, sulfuric acid is an oily liquid heavier than water. Unlike hydrochloric and nitric acids, it is not volatile; molecules do not evaporate from its surface. What state of aggregation does plastic sulfur have, which is obtained by heating crystals?
In its amorphous form, the substance has the structure of a liquid, with insignificant fluidity. But plastic sulfur simultaneously retains its shape (as a solid). There are liquid crystals that have a number of characteristic properties of solids. Thus, the state of a substance under different conditions depends on its nature, temperature, pressure and other external conditions.
What features exist in the structure of solids?
The existing differences between the basic aggregate states of matter are explained by the interaction between atoms, ions and molecules. For example, why does the solid state of matter lead to the ability of bodies to maintain volume and shape? In the crystal lattice of a metal or salt, structural particles are attracted to each other. In metals, positively charged ions interact with what is called an “electron gas,” a collection of free electrons in a piece of metal. Salt crystals arise due to the attraction of oppositely charged particles - ions. The distance between the above structural units of solids is much smaller than the sizes of the particles themselves. In this case, electrostatic attraction acts, it imparts strength, but repulsion is not strong enough.
To destroy the solid state of aggregation of a substance, effort must be made. Metals, salts, and atomic crystals melt at very high temperatures. For example, iron becomes liquid at temperatures above 1538 °C. Tungsten is refractory and is used to make incandescent filaments for light bulbs. There are alloys that become liquid at temperatures above 3000 °C. Many on Earth are in a solid state. These raw materials are extracted using technology in mines and quarries.
To separate even one ion from a crystal, a large amount of energy must be expended. But it is enough to dissolve salt in water for the crystal lattice to disintegrate! This phenomenon is explained by the amazing properties of water as a polar solvent. H 2 O molecules interact with salt ions, destroying the chemical bond between them. Thus, dissolution is not a simple mixing of different substances, but a physicochemical interaction between them.
How do liquid molecules interact?
Water can be a liquid, a solid, and a gas (steam). These are its basic states of aggregation under normal conditions. Water molecules consist of one oxygen atom to which two hydrogen atoms are bonded. Polarization of the chemical bond in the molecule occurs, and a partial negative charge appears on the oxygen atoms. Hydrogen becomes the positive pole in the molecule, attracted by the oxygen atom of another molecule. This is called "hydrogen bonding".
The liquid state of aggregation is characterized by distances between structural particles comparable to their sizes. Attraction exists, but it is weak, so the water does not retain its shape. Vaporization occurs due to the destruction of bonds that occurs on the surface of the liquid even at room temperature.
Do intermolecular interactions exist in gases?
The gaseous state of a substance differs from liquid and solid in a number of parameters. There are large gaps between the structural particles of gases, much larger than the sizes of molecules. In this case, the forces of attraction do not act at all. The gaseous state of aggregation is characteristic of substances present in the air: nitrogen, oxygen, carbon dioxide. In the picture below, the first cube is filled with gas, the second with liquid, and the third with solid.
Many liquids are volatile; molecules of the substance break off from their surface and go into the air. For example, if you bring a cotton swab dipped in ammonia to the opening of an open bottle of hydrochloric acid, white smoke appears. A chemical reaction between hydrochloric acid and ammonia occurs right in the air, producing ammonium chloride. What state of aggregation is this substance in? Its particles that form white smoke are tiny solid crystals of salt. This experiment must be carried out under a hood; the substances are toxic.
Conclusion
The state of aggregation of gas was studied by many outstanding physicists and chemists: Avogadro, Boyle, Gay-Lussac, Clayperon, Mendeleev, Le Chatelier. Scientists have formulated laws that explain the behavior of gaseous substances in chemical reactions when external conditions change. Open patterns were not only included in school and university textbooks on physics and chemistry. Many chemical industries are based on knowledge about the behavior and properties of substances in different states of aggregation.
Introduction
1. The physical state of the substance is gas
2. The physical state of the substance is liquid
3.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 exist in three states: solid, liquid and gaseous.
The interaction between particles of a substance is most pronounced in the solid state. The distance between molecules is approximately equal to their own sizes. This leads to a fairly strong interaction, which practically makes it impossible for the particles 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 intensely than in solids, and therefore 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, 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. liquids
3.solids
3. State of matter – solid
Solid, one of the four states of aggregation of a substance, different from other states of aggregation (liquids, gases, plasma) stability of shape and the nature of the thermal motion of atoms performing small vibrations around equilibrium positions. Along with the crystalline state of thorax, there is an amorphous state, including a glassy state. Crystals are characterized by long-range order in the arrangement of atoms. There is no long-range order in amorphous bodies.
I think everyone knows the 3 main states of matter: liquid, solid and gaseous. We encounter these states of matter every day and everywhere. Most often they are considered using the example of water. The liquid state of water is most familiar to us. We constantly drink liquid water, it flows from our tap, and we ourselves are 70% liquid water. The second physical state of water is ordinary ice, which we see on the street in winter. Water is also easy to find in gaseous form in everyday life. In the gaseous state, water is, as we all know, steam. It can be seen when, for example, we boil a kettle. Yes, it is at 100 degrees that water changes from liquid to gaseous.
These are the three states of matter that are familiar to us. But did you know that there are actually 4 of them? I think everyone has heard the word " plasma" And today I want you to also learn more about plasma - the fourth state of matter.
Plasma is a partially or fully ionized gas with equal densities of both positive and negative charges. Plasma can be obtained from gas - from the 3rd state of aggregation of a substance by strong heating. The state of aggregation in general, in fact, completely depends on temperature. The first state of aggregation is the lowest temperature at which the body remains solid, the second state of aggregation is the temperature at which the body begins to melt and become liquid, the third state of aggregation is the highest temperature, at which the substance becomes a gas. For each body, substance, the temperature of transition from one state of aggregation to another is completely different, for some it is lower, for some it is higher, but for everyone it is strictly in this sequence. At what temperature does a substance become plasma? Since this is the fourth state, it means that the temperature of transition to it is higher than that of each previous one. And indeed it is. In order to ionize a gas, a very high temperature is required. The lowest temperature and low ionized (about 1%) plasma is characterized by a temperature of up to 100 thousand degrees. Under terrestrial conditions, such plasma can be observed in the form of lightning. The temperature of the lightning channel can exceed 30 thousand degrees, which is 6 times higher than the temperature of the surface of the Sun. By the way, the Sun and all other stars are also plasma, most often high-temperature. Science proves that about 99% of all matter in the Universe is plasma.
Unlike low-temperature plasma, high-temperature plasma has almost 100% ionization and a temperature of up to 100 million degrees. This is truly a stellar temperature. On Earth, such plasma is found only in one case - for thermo-nuclear fusion experiments. Controlling the reaction is quite complex and energy-intensive, but uncontrolled reaction is quite early - behaved like a weapon of colossal power - a thermo-nuclear bomb, tested by the USSR on August 12, 1953.
Plasma is classified not only by temperature and degree of ionization, but also by density and quasi-neutrality. Collocation plasma density usually means electron density, that is, the number of free electrons per unit volume. Well, with this, I think everything is clear. But not everyone knows what quasi-neutrality is. Plasma quasineutrality is one of its most important properties, which consists in the almost exact equality of the densities of the positive ions and electrons included in its composition. Due to the good electrical conductivity of plasma, the separation of positive and negative charges is impossible at distances greater than the Debye length and at times greater than the period of plasma oscillations. Almost all plasma is quasi-neutral. An example of a non-quasi-neutral plasma is an electron beam. However, the density of non-neutral plasmas must be very small, otherwise they will quickly decay due to Coulomb repulsion.
We have looked at very few terrestrial examples of plasma. But there are quite a lot of them. Man has learned to use plasma for his own benefit. Thanks to the fourth aggregate state of matter, we can use gas-discharge lamps, plasma televisions, zoo-rami, arc-electric welding, laser-rami. Conventional gas-discharge fluorescent lamps are also plasma. There is also a plasma lamp in our world. It is mainly used in science to study and, most importantly, see some of the most complex plasma phenomena, including filamentation. A photograph of such a lamp can be seen in the picture below:
In addition to household plasma devices, natural plasma can also often be seen on Earth. We have already talked about one of her examples. This is lightning. But in addition to lightning, plasma phenomena can be called the northern lights, “St. Elmo’s fire,” the Earth’s ionosphere and, of course, fire.
Notice that fire, lightning, and other manifestations of plasma, as we call it, burn. What causes such a bright light emission from plasma? Plasma glow is caused by the transition of electrons from a high-energy state to a low-energy state after recombination with ions. This process results in radiation with a spectrum corresponding to the excited gas. This is why plasma glows.
I would also like to talk a little about the history of plasma. After all, once upon a time only such substances as the liquid component of milk and the colorless component of blood were called plasma. Everything changed in 1879. It was in that year that the famous English scientist William Crookes, while studying electrical conductivity in gases, discovered the phenomenon of plasma. True, this state of matter was called plasma only in 1928. And this was done by Irving Langmuir.
In conclusion, I want to say that such an interesting and mysterious phenomenon as ball lightning, which I have written about more than once on this site, is, of course, also a plasmoid, like ordinary lightning. This is perhaps the most unusual plasmoid of all terrestrial plasma phenomena. After all, there are about 400 different theories about ball lightning, but not one of them has been recognized as truly correct. In laboratory conditions, similar but short-term phenomena were obtained in several different ways, so the question about the nature of ball lightning remains open.
Ordinary plasma, of course, was also created in laboratories. This was once difficult, but now such an experiment is not particularly difficult. Since plasma has firmly entered our everyday arsenal, they are experimenting a lot on it in laboratories.
The most interesting discovery in the field of plasma was experiments with plasma in zero gravity. It turns out that plasma crystallizes in a vacuum. It happens like this: charged plasma particles begin to repel each other, and when they have a limited volume, they occupy the space that is allotted to them, scattering in different directions. This is quite similar to a crystal lattice. Doesn't this mean that plasma is the closing link between the first state of matter and the third? After all, it becomes plasma due to the ionization of the gas, and in a vacuum the plasma again becomes solid. But this is just my guess.
Plasma crystals in space also have a rather strange structure. This structure can only be observed and studied in space, in the real vacuum of space. Even if you create a vacuum on Earth and place plasma there, gravity will simply compress the entire “picture” that forms inside. In space, plasma crystals simply take off, forming a three-dimensional three-dimensional structure of a strange shape. After sending the results of observing plasma in orbit to scientists on Earth, it turned out that the vortices in the plasma strangely repeat the structure of our galaxy. This means that in the future it will be possible to understand how our galaxy was born by studying plasma. The photographs below show the same crystallized plasma.
That's all I would like to say on the topic of plasma. I hope it interested and surprised you. After all, this is truly an amazing phenomenon, or rather a state - the 4th state of matter.
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- and short-range order, and others. A change in the state of aggregation can be accompanied by an abrupt 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.
Definitions of states of aggregation are not always strict. Thus, there are amorphous bodies that retain the structure of a liquid and have low 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, the broader concept of thermodynamic phase is used. Phenomena that describe transitions from one phase to another are called critical phenomena.
The state of aggregation 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 interaction of molecules to their average kinetic energy. Thus, for a solid 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, intermolecular distances are large, molecules hardly interact with each other and move almost freely, filling the entire volume. In liquids and solids - condensed matter - molecules (atoms) are located much closer to each other and interact more strongly.
This leads to liquids and solids maintaining 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 vibrations 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. The atoms of a solid undergo only small vibrations around the equilibrium state. There is both long- 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 container in which it is placed. Atoms or molecules of a liquid vibrate near an equilibrium state, locked by other atoms, and often jump to other free places. Only short-range order is present.
Melting- this is the transition of a substance from a solid state of aggregation (see Aggregate states of matter) to liquid. This process occurs when heated, when a certain amount of heat +Q is imparted to the body. For example, the low-melting metal lead changes from a solid 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 steel melting - 1300-1500°C).
If, while melting lead, you measure its temperature, you will find that at first it increases smoothly, but after a certain point remains constant, despite further heating. This moment corresponds to melting. The temperature remains constant until all the lead has melted, and only then begins to rise again. When liquid lead is cooled, the opposite picture is observed: the temperature drops until solidification begins and remains constant all the time until the lead passes into the solid phase, and then drops again.
All pure substances behave in a similar way. The constancy of the temperature during melting is of great practical importance, since it allows you to calibrate thermometers and make fuses and indicators that melt at a strictly specified temperature.
Atoms in a crystal oscillate around their equilibrium positions. With increasing temperature, the amplitude of vibrations increases and reaches a certain critical value, after which the crystal lattice is destroyed. This requires additional thermal energy, so the temperature does not increase during the melting process, although heat continues to flow.
The melting point of a substance depends on pressure. For substances whose volume increases during melting (and these are the vast majority), an increase in pressure increases the melting point and vice versa. When water melts, its volume decreases (therefore, when water freezes, it bursts pipes), and when pressure increases, ice melts at a lower temperature. Bismuth, gallium and some brands of cast iron behave in a similar way.
V. Gas- a state characterized by good compressibility, lack of ability to retain 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 larger than their sizes.
Plasma, often classified as an aggregate state of matter, differs from gas in the high degree of ionization of atoms. Most of the baryonic matter (about 99.9% by mass) in the Universe is in the plasma state.
city 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. Supercritical fluid has exceptionally high dissolving power.
d. Bose-Einstein condensate- is obtained as a result of cooling a Bose gas to temperatures close to absolute zero. As a result, some atoms find themselves 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. Fermion condensate- represents Bose condensation in the BCS mode of “atomic Cooper pairs” in gases consisting of fermion atoms. (In contrast to the traditional regime 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 higher.
Degenerate matter - Fermi gas Stage 1 Electron-degenerate gas, observed in white dwarfs, plays an important role in the evolution of stars. 2nd stage, the neutron state, matter passes into it at ultra-high pressure, which is not yet achievable in the laboratory, but exists inside neutron stars. During the transition to the neutron state, the electrons of the substance interact with protons and turn into neutrons. As a result, matter in the neutron state consists entirely of neutrons and has a density on the order of nuclear. 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 born and annihilate in the neutron state. With a further increase in temperature, deconfinement occurs, and the substance passes into the state of quark-gluon plasma. It no longer consists of hadrons, but of constantly being born and disappearing quarks and gluons. Perhaps deconfinement occurs in two stages.
With a further unlimited increase in pressure without increasing temperature, the substance collapses into a black hole.
With a simultaneous increase in both pressure and temperature, other particles are added to the quarks and gluons. What happens to matter, space and time at temperatures close to Planck’s is still unknown.
Other states
During deep cooling, some (not all) substances transform into a superconducting or superfluid state. These states, of course, are separate thermodynamic phases, but they can hardly be called new aggregate states of matter due to their non-universality.
Heterogeneous substances such as pastes, gels, suspensions, aerosols, etc., which under certain conditions demonstrate 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 .
