What bodies are called amorphous? Amorphous substances. Crystalline and amorphous state of matter. Application of amorphous substances

Solids are divided into amorphous and crystalline, depending on their molecular structure and physical properties.

Unlike crystals, the molecules and atoms of amorphous solids do not form a lattice, and the distance between them fluctuates within a certain range of possible distances. In other words, in crystals, atoms or molecules are mutually arranged in such a way that the formed structure can be repeated throughout the entire volume of the body, which is called long-range order. In the case of amorphous bodies, the structure of molecules is preserved only relative to each one such molecule, a pattern is observed in the distribution of only neighboring molecules - short-range order. An illustrative example is presented below.

Amorphous bodies include glass and other substances in a glassy state, rosin, resins, amber, sealing wax, bitumen, wax, as well as organic substances: rubber, leather, cellulose, polyethylene, etc.

Properties of amorphous bodies

The structural features of amorphous solids give them individual properties:

1. Weak fluidity is one of the most well-known properties of such bodies. An example would be glass drips that have been sitting in a window frame for a long time.
2. Amorphous solids do not have a specific melting point, since the transition to a liquid state during heating occurs gradually, through softening of the body. For this reason, the so-called softening temperature range is applied to such bodies.

1. Due to their structure, such bodies are isotropic, that is, their physical properties do not depend on the choice of direction.
2. A substance in an amorphous state has greater internal energy than in a crystalline state. For this reason, amorphous bodies are able to independently transform into a crystalline state. This phenomenon can be observed as a result of glass becoming cloudy over time.

Glassy state

In nature, there are liquids that are practically impossible to transform into a crystalline state by cooling, since the complexity of the molecules of these substances does not allow them to form a regular crystal lattice. Such liquids include molecules of some organic polymers.

However, with the help of deep and rapid cooling, almost any substance can transform into a glassy state. This is an amorphous state that does not have a clear crystal lattice, but can partially crystallize on the scale of small clusters. This state of matter is metastable, that is, it persists under certain required thermodynamic conditions.

Using cooling technology at a certain speed, the substance will not have time to crystallize and will be converted into glass. That is, the higher the cooling rate of the material, the less likely it is to crystallize. For example, to produce metal glasses, a cooling rate of 100,000 - 1,000,000 Kelvin per second will be required.

In nature, the substance exists in a glassy state and arises from liquid volcanic magma, which, interacting with cold water or air, quickly cools. In this case, the substance is called volcanic glass. You can also observe glass formed as a result of the melting of a falling meteorite interacting with the atmosphere - meteorite glass or moldavite.

>>Physics: Amorphous bodies

Not all solids are crystals. There are many amorphous bodies. How are they different from crystals?
Amorphous bodies do not have a strict order in the arrangement of atoms. Only the nearest neighbor atoms are arranged in some order. But there is no strict repeatability in all directions of the same structural element, which is characteristic of crystals, in amorphous bodies.
In terms of the arrangement of atoms and their behavior, amorphous bodies are similar to liquids.
Often the same substance can be found in both crystalline and amorphous states. For example, quartz SiO 2 can be in either crystalline or amorphous form (silica). The crystalline form of quartz can be schematically represented as a lattice of regular hexagons ( Fig. 12.6, a). The amorphous structure of quartz also has the appearance of a lattice, but of irregular shape. Along with hexagons, it contains pentagons and heptagons ( Fig. 12.6, b).
Properties of amorphous bodies. All amorphous bodies are isotropic, that is, their physical properties are the same in all directions. Amorphous bodies include glass, resin, rosin, sugar candy, etc.
Under external influences, amorphous bodies exhibit both elastic properties, like solids, and fluidity, like liquids. Thus, under short-term impacts (impacts), they behave like solid bodies and, under a strong impact, break into pieces. But with very long exposure, amorphous bodies flow. You can see this for yourself if you are patient. Follow the piece of resin that is lying on a hard surface. Gradually the resin spreads over it, and the higher the temperature of the resin, the faster this happens.
Atoms or molecules of amorphous bodies, like molecules of a liquid, have a certain time of “settled life” - the time of oscillations around the equilibrium position. But unlike liquids, this time is very long.
So, for var at t= 20°C “settled life” time is approximately 0.1 s. In this respect, amorphous bodies are close to crystalline ones, since jumps of atoms from one equilibrium position to another occur relatively rarely.
Amorphous bodies at low temperatures resemble solid bodies in their properties. They have almost no fluidity, but as the temperature rises they gradually soften and their properties become closer and closer to the properties of liquids. This happens because with increasing temperature, jumps of atoms from one equilibrium position to another gradually become more frequent. Certain melting point Amorphous bodies, unlike crystalline ones, do not.
Liquid crystals. In nature, there are substances that simultaneously possess the basic properties of a crystal and a liquid, namely anisotropy and fluidity. This state of matter is called liquid crystal. Liquid crystals are mainly organic substances whose molecules have a long thread-like or flat plate shape.
Let us consider the simplest case, when a liquid crystal is formed by thread-like molecules. These molecules are located parallel to each other, but are randomly shifted, i.e., order, unlike ordinary crystals, exists only in one direction.
During thermal motion, the centers of these molecules move randomly, but the orientation of the molecules does not change, and they remain parallel to themselves. Strict molecular orientation does not exist throughout the entire volume of the crystal, but in small regions called domains. Refraction and reflection of light occurs at the domain boundaries, which is why liquid crystals are opaque. However, in a layer of liquid crystal placed between two thin plates, the distance between which is 0.01-0.1 mm, with parallel depressions of 10-100 nm, all the molecules will be parallel and the crystal will become transparent. If electrical voltage is applied to some areas of the liquid crystal, the liquid crystal state is disrupted. These areas become opaque and begin to glow, while the areas without tension remain dark. This phenomenon is used in the creation of liquid crystal television screens. It should be noted that the screen itself consists of a huge number of elements and the electronic control circuit for such a screen is extremely complex.
Solid state physics. Humanity has always used and will continue to use solids. But if previously solid state physics lagged behind the development of technology based on direct experience, now the situation has changed. Theoretical research leads to the creation of solids whose properties are completely unusual.
It would be impossible to obtain such bodies by trial and error. The creation of transistors, which will be discussed later, is a striking example of how understanding the structure of solids led to a revolution in all radio engineering.
Obtaining materials with specified mechanical, magnetic, electrical and other properties is one of the main directions of modern solid state physics. Approximately half of the world's physicists now work in this area of ​​physics.
Amorphous solids occupy an intermediate position between crystalline solids and liquids. Their atoms or molecules are arranged in relative order. Understanding the structure of solids (crystalline and amorphous) allows you to create materials with desired properties.

???
1. How do amorphous bodies differ from crystalline bodies?
2. Give examples of amorphous bodies.
3. Would the glassblowing profession have arisen if glass had been a crystalline solid rather than an amorphous one?

G.Ya.Myakishev, B.B.Bukhovtsev, N.N.Sotsky, Physics 10th grade

If you have corrections or suggestions for this lesson,

« Physics - 10th grade"

In addition to solids that have a crystalline structure, which is characterized by a strict order in the arrangement of atoms, there are amorphous solids.

Amorphous bodies do not have a strict order in the arrangement of atoms. Only the nearest neighbor atoms are arranged in some order. But there is no strict repeatability in all directions of the same structural element, which is characteristic of crystals, in amorphous bodies. In terms of the arrangement of atoms and their behavior, amorphous bodies are similar to liquids. Often the same substance can be found in both crystalline and amorphous states.

Theoretical studies lead to the production of solids whose properties are completely unusual. It would be impossible to obtain such bodies by trial and error. The creation of transistors, which will be discussed later, is a striking example of how understanding the structure of solids led to a revolution in all radio engineering.

Obtaining materials with specified mechanical, magnetic, electrical and other properties is one of the main directions of modern solid state physics.

It must be remembered that not all bodies that exist on planet Earth have a crystalline structure. Exceptions to the rule are called “amorphous bodies.” How are they different? Based on the translation of this term - amorphous - it can be assumed that such substances differ from others in their shape or appearance. We are talking about the absence of the so-called crystal lattice. The splitting process that produces edges does not occur. Amorphous bodies are also distinguished by the fact that they do not depend on the environment and their properties are constant. Such substances are called isotropic.

A short description of amorphous bodies

From a school physics course, you can remember that amorphous substances have a structure in which the atoms in them are arranged in a chaotic order. Only neighboring structures where such an arrangement is forced can have a specific location. But still, drawing an analogy with crystals, amorphous bodies do not have a strict ordering of molecules and atoms (in physics this property is called “long-range order”). As a result of research, it was found that these substances are similar in structure to liquids.

Some bodies (for example, we can take silicon dioxide, whose formula is SiO 2) can simultaneously be in an amorphous state and have a crystalline structure. Quartz in the first version has the structure of an irregular lattice, in the second - a regular hexagon.

Property No. 1

As mentioned above, amorphous bodies do not have a crystal lattice. Their atoms and molecules have a short order of arrangement, which will be the first distinctive property of these substances.

Property No. 2

These bodies are deprived of fluidity. In order to better explain the second property of substances, we can do this using the example of wax. It's no secret that if you pour water into a funnel, it will simply pour out of it. The same will happen with any other fluid substances. But the properties of amorphous bodies do not allow them to perform such “tricks”. If the wax is placed in a funnel, it will first spread over the surface and only then begin to drain from it. This is due to the fact that molecules in a substance jump from one equilibrium position to a completely different one, without having a primary location.

Property No. 3

It's time to talk about the melting process. It should be remembered that amorphous substances do not have a specific temperature at which melting begins. As the temperature rises, the body gradually becomes softer and then turns into liquid. Physicists always focus not on the temperature at which a given process began to occur, but on the corresponding melting temperature range.

Property No. 4

It has already been mentioned above. Amorphous bodies are isotropic. That is, their properties in any direction are unchanged, even if the conditions of stay in places are different.

Property No. 5

At least once, every person has observed that over a certain period of time the glass began to become cloudy. This property of amorphous bodies is associated with increased internal energy (it is several times greater than that of crystals). Because of this, these substances can easily go into a crystalline state.

Transition to the crystalline state

After a certain period of time, any amorphous body transforms into a crystalline state. This can be observed in a person’s everyday life. For example, if you leave candy or honey for several months, you may notice that they both have lost their transparency. The average person will say that they are simply sugar-coated. Indeed, if you break the body, you will notice the presence of sugar crystals.

So, speaking about this, it is necessary to clarify that spontaneous transformation into another state is due to the fact that amorphous substances are unstable. Comparing them with crystals, you can understand that the latter are many times more “powerful”. This fact can be explained using the intermolecular theory. According to it, molecules constantly jump from one place to another, thereby filling the voids. Over time, a stable crystal lattice is formed.

Melting of amorphous bodies

The process of melting of amorphous bodies is the moment when, with an increase in temperature, all bonds between atoms are destroyed. This is when the substance turns into a liquid. If the melting conditions are such that the pressure is the same throughout the entire period, then the temperature must also be fixed.

Liquid crystals

In nature, there are bodies that have a liquid crystalline structure. As a rule, they are included in the list of organic substances, and their molecules have a thread-like shape. The bodies in question have the properties of liquids and crystals, namely fluidity and anisotropy.

In such substances, the molecules are located parallel to each other, however, there is no fixed distance between them. They move constantly, but are unwilling to change orientation, so they are constantly in one position.

Amorphous metals

Amorphous metals are better known to the average person as metallic glasses.

Back in 1940, scientists started talking about the existence of these bodies. Even then it became known that metals specially produced by vacuum deposition did not have crystal lattices. And only 20 years later the first glass of this type was produced. It did not attract much attention from scientists; and only after another 10 years did American and Japanese professionals, and then Korean and European ones, start talking about him.

Amorphous metals are characterized by viscosity, a fairly high level of strength and resistance to corrosion.

MINISTRY OF EDUCATION

PHYSICS 8TH GRADE

Report on the topic:

“Amorphous bodies. Melting of amorphous bodies.”

8th grade student:

2009

Amorphous bodies.

Let's do an experiment. We will need a piece of plasticine, a stearine candle and an electric fireplace. Let's place plasticine and a candle at equal distances from the fireplace. After some time, part of the stearin will melt (become liquid), and part will remain in the form of a solid piece. During the same time, the plasticine will soften only a little. After some time, all the stearin will melt, and the plasticine will gradually “corrode” along the surface of the table, softening more and more.

So, there are bodies that do not soften when melted, but turn from a solid state immediately into a liquid. During the melting of such bodies, it is always possible to separate the liquid from the not yet melted (solid) part of the body. These bodies are crystalline. There are also solids that, when heated, gradually soften and become more and more fluid. For such bodies it is impossible to indicate the temperature at which they turn into liquid (melt). These bodies are called amorphous.

Let's do the following experiment. Throw a piece of resin or wax into a glass funnel and leave it in a warm room. After about a month, it will turn out that the wax has taken the shape of a funnel and even began to flow out of it in the form of a “stream” (Fig. 1). In contrast to crystals, which retain their own shape almost forever, amorphous bodies exhibit fluidity even at low temperatures. Therefore, they can be considered as very thick and viscous liquids.

The structure of amorphous bodies. Studies using an electron microscope, as well as using X-rays, indicate that in amorphous bodies there is no strict order in the arrangement of their particles. Take a look, figure 2 shows the arrangement of particles in crystalline quartz, and the one on the right shows the arrangement of particles in amorphous quartz. These substances consist of the same particles - molecules of silicon oxide SiO 2.

The crystalline state of quartz is obtained if molten quartz is cooled slowly. If the cooling of the melt is rapid, then the molecules will not have time to “line up” in orderly rows, and the result will be amorphous quartz.

Particles of amorphous bodies oscillate continuously and randomly. They can jump from place to place more often than crystal particles. This is also facilitated by the fact that the particles of amorphous bodies are located unequally densely: there are voids between them.

Crystallization of amorphous bodies. Over time (several months, years), amorphous substances spontaneously transform into a crystalline state. For example, sugar candies or fresh honey left alone in a warm place will become opaque after a few months. They say that honey and candy are “candied.” By breaking a candy cane or scooping up honey with a spoon, we will actually see the sugar crystals that have formed.

Spontaneous crystallization of amorphous bodies indicates that the crystalline state of a substance is more stable than the amorphous one. The intermolecular theory explains it this way. Intermolecular forces of attraction and repulsion cause particles of an amorphous body to jump preferentially to where there are voids. As a result, a more ordered arrangement of particles appears than before, that is, a polycrystal is formed.

Melting of amorphous bodies.

As the temperature increases, the energy of the vibrational motion of atoms in a solid increases and, finally, a moment comes when the bonds between atoms begin to break. In this case, the solid turns into a liquid state. This transition is called melting. At a fixed pressure, melting occurs at a strictly defined temperature.

The amount of heat required to convert a unit mass of a substance into a liquid at its melting point is called the specific heat of fusion λ .

To melt a substance of mass m it is necessary to expend an amount of heat equal to:

Q = λ m .

The process of melting amorphous bodies differs from the melting of crystalline bodies. As the temperature increases, amorphous bodies gradually soften and become viscous until they turn into liquid. Amorphous bodies, unlike crystals, do not have a specific melting point. The temperature of amorphous bodies changes continuously. This happens because in amorphous solids, as in liquids, molecules can move relative to each other. When heated, their speed increases, and the distance between them increases. As a result, the body becomes softer and softer until it turns into liquid. When amorphous bodies solidify, their temperature also decreases continuously.