Unlike crystalline solids, there is no strict order in the arrangement of particles in an amorphous solid.
Although amorphous solids are capable of maintaining their shape, they do not have a crystal lattice. A certain pattern is observed only for molecules and atoms located in the vicinity. This order is called close order . It is not repeated in all directions and is not stored in long distances, like crystalline bodies.
Examples of amorphous bodies are glass, amber, artificial resins, wax, paraffin, plasticine, etc.
Features of amorphous bodies
Atoms in amorphous bodies vibrate around points that are randomly located. Therefore, the structure of these bodies resembles the structure of liquids. But the particles in them are less mobile. The time they oscillate around the equilibrium position is longer than in liquids. Jumps of atoms to another position also occur much less frequently.
How do crystalline solids behave when heated? They begin to melt at a certain melting point. And for some time they are simultaneously in solid and liquid state until all the substance melts.
Amorphous solids do not have a specific melting point . When heated, they do not melt, but gradually soften.
Place a piece of plasticine near the heating device. After some time it will become soft. This does not happen instantly, but over a certain period of time.
Since the properties of amorphous bodies are similar to the properties of liquids, they are considered as supercooled liquids with very high viscosity (frozen liquids). At normal conditions they cannot flow. But when heated, jumps of atoms in them occur more often, viscosity decreases, and amorphous bodies gradually soften. The higher the temperature, the lower the viscosity, and gradually the amorphous body becomes liquid.
Ordinary glass is a solid amorphous body. It is obtained by melting silicon oxide, soda and lime. By heating the mixture to 1400 o C, a liquid glassy mass is obtained. When cooling liquid glass does not solidify like crystalline bodies, but remains a liquid, the viscosity of which increases and the fluidity decreases. Under normal conditions, it appears to us as a solid body. But in fact it is a liquid that has enormous viscosity and fluidity, so low that it can barely be distinguished by the most ultrasensitive instruments.
The amorphous state of a substance is unstable. Over time, it gradually turns from an amorphous state into a crystalline state. This process in different substances passes with at different speeds. We see candy canes becoming covered in sugar crystals. This does not take very much time.
And for crystals to form in ordinary glass, a lot of time must pass. During crystallization, glass loses its strength, transparency, becomes cloudy, and becomes brittle.
Isotropy of amorphous bodies
In crystalline solids physical properties vary in different directions. But in amorphous bodies they are the same in all directions. This phenomenon is called isotropy .
An amorphous body conducts electricity and heat equally in all directions and refracts light equally. Sound also travels equally in amorphous bodies in all directions.
The properties of amorphous substances are used in modern technologies. Special interest cause metal alloys that do not have a crystalline structure and belong to amorphous solids. They are called metal glasses . Their physical, mechanical, electrical and other properties differ from those of ordinary metals for the better.
Thus, in medicine they use amorphous alloys whose strength exceeds that of titanium. They are used to make screws or plates that connect broken bones. Unlike titanium fasteners, this material gradually disintegrates and is replaced over time by bone material.
High-strength alloys are used in the manufacture of metal-cutting tools, fittings, springs, and mechanism parts.
An amorphous alloy with high magnetic permeability has been developed in Japan. By using it in transformer cores instead of textured transformer steel sheets, eddy current losses can be reduced by 20 times.
Amorphous metals have unique properties. They are called the material of the future.
Have you ever wondered what the mysterious amorphous substances? They differ in structure from both solids and liquids. The fact is that such bodies are in a special condensed state, which has only short-range order. Examples of amorphous substances are resin, glass, amber, rubber, polyethylene, polyvinyl chloride (our favorite plastic windows), various polymers and others. These are solids that do not have a crystal lattice. These also include sealing wax, various adhesives, hard rubber and plastics.
Unusual properties of amorphous substances
During cleavage, no edges are formed in amorphous solids. The particles are completely disordered and are located on close range to each other. They can be either very thick or viscous. How are they affected by external influences? Under the influence of different temperatures, bodies become fluid, like liquids, and at the same time quite elastic. In case external influence does not last long, substances amorphous structure may at powerful blow break into pieces. Long-term influence from outside leads to the fact that they simply flow.
Try it at home small experiment using resin. Place it on a hard surface and you will notice that it begins to flow smoothly. That's right, it's substance! The speed depends on the temperature readings. If it is very high, the resin will begin to spread noticeably faster.
What else is characteristic of such bodies? They can take any form. If amorphous substances in the form of small particles are placed in a vessel, for example, in a jug, then they will also take the shape of the vessel. They are also isotropic, that is, they exhibit the same physical properties in all directions.
Melting and transition to other states. Metal and glass
The amorphous state of a substance does not imply the maintenance of any certain temperature. At low values the bodies freeze, at high values they melt. By the way, the degree of viscosity of such substances also depends on this. Low temperature promotes reduced viscosity, high temperature, on the contrary, increases it.
For substances of the amorphous type, one more feature can be distinguished - the transition to a crystalline state, and a spontaneous one. Why is this happening? The internal energy in a crystalline body is much less than in an amorphous one. We can notice this in the example of glass products - over time, the glass becomes cloudy.
Metallic glass - what is it? The metal can be removed from the crystal lattice during melting, that is, a substance with an amorphous structure can be made glassy. During solidification during artificial cooling, the crystal lattice is formed again. Amorphous metal has amazing resistance to corrosion. For example, a car body made from it would not need various coatings, since it would not be subject to spontaneous destruction. An amorphous substance is a body atomic structure which has unprecedented strength, which means that the amorphous metal could be used in absolutely any industrial sector.
Crystal structure of substances
In order to have a good understanding of the characteristics of metals and be able to work with them, you need to have knowledge of the crystalline structure of certain substances. The production of metal products and the field of metallurgy could not have developed so much if people did not have certain knowledge about changes in the structure of alloys, technological techniques and operational characteristics.
Four states of matter
It is common knowledge that there are four state of aggregation: solid, liquid, gaseous, plasma. Amorphous solids can also be crystalline. With this structure, spatial periodicity in the arrangement of particles can be observed. These particles in crystals can perform periodic motion. In all bodies that we observe in a gaseous or liquid state, we can notice the movement of particles in the form of a chaotic disorder. Amorphous solids (for example, metals in a condensed state: hard rubber, glass products, resins) can be called frozen liquids, because when they change shape, you can notice such characteristic feature, like viscosity.
Difference between amorphous bodies and gases and liquids
Manifestations of plasticity, elasticity, and hardening during deformation are characteristic of many bodies. Crystalline and amorphous substances in to a greater extent have these characteristics, while liquids and gases do not have such properties. But you can notice that they contribute to an elastic change in volume.
Crystalline and amorphous substances. Mechanical and physical properties
What are crystalline and amorphous substances? As mentioned above, those bodies that have a huge viscosity coefficient can be called amorphous, and their fluidity is impossible at ordinary temperatures. And here heat, on the contrary, allows them to be fluid, like a liquid.
Substances seem completely different crystalline type. These solids may have their own melting point, depending on external pressure. Obtaining crystals is possible if the liquid is cooled. If you do not take certain measures, you will notice that in a liquid state, various centers crystallization. In the area surrounding these centers, solid formation occurs. Very small crystals begin to connect with each other in a random order, and a so-called polycrystal is obtained. Such a body is isotropic.
Characteristics of substances
What determines physical and mechanical characteristics tel? Important have atomic bonds, as well as the type of crystal structure. Crystals ionic type characterized by ionic bonds, which means a smooth transition from one atom to another. In this case, the formation of positively and negatively charged particles occurs. Ionic bond we can watch on simple example- such characteristics are characteristic of various oxides and salts. Another feature of ionic crystals is low thermal conductivity, but its performance can increase noticeably when heated. At the nodes of the crystal lattice you can see various molecules that are distinguished by strong atomic bonds.
Many minerals that we find throughout nature have a crystalline structure. And the amorphous state of matter is also nature in pure form. Only in this case the body is something shapeless, but crystals can take the form of beautiful polyhedrons with flat edges, and also form new solid bodies of amazing beauty and purity.
What are crystals? Amorphous-crystalline structure
The shape of such bodies is constant for a particular compound. For example, beryl always looks like a hexagonal prism. Try a little experiment. Take a small crystal table salt cubic shape (ball) and put it in a special solution as saturated as possible with the same table salt. Over time, you will notice that this body has remained unchanged - it has again acquired the shape of a cube or ball, which is characteristic of table salt crystals.
3. - polyvinyl chloride, or the well-known plastic PVC windows. It is resistant to fires, as it is considered to be flame retardant, has increased mechanical strength and electrical insulating properties.
4. Polyamide is a substance with very high strength and wear resistance. It is characterized by high dielectric characteristics.
5. Plexiglas, or polymethyl methacrylate. We can use it in the field of electrical engineering or use it as a material for structures.
6. Fluoroplastic, or polytetrafluoroethylene, is a well-known dielectric that does not exhibit dissolution properties in solvents of organic origin. Wide temperature range and good dielectric properties allow it to be used as a hydrophobic or anti-friction material.
7. Polystyrene. This material is not affected by acids. It, like fluoroplastic and polyamide, can be considered a dielectric. Very durable against mechanical impact. Polystyrene is used everywhere. For example, it has proven itself well as a structural and electrical insulating material. Used in electrical and radio engineering.
8. Probably the most famous polymer for us is polyethylene. The material is resistant to impact aggressive environment, it does not allow moisture to pass through at all. If the packaging is made of polyethylene, there is no fear that the contents will deteriorate when exposed to heavy rain. Polyethylene is also a dielectric. Its application is extensive. Pipe structures, various electrical products, insulating film, sheaths for telephone and cable cables are made from it. power lines, parts for radio and other equipment.
9. Polyvinyl chloride is a high-polymer substance. It is synthetic and thermoplastic. It has a molecular structure that is asymmetrical. It is almost impervious to water and is made by pressing, stamping and molding. Polyvinyl chloride is most often used in the electrical industry. Based on it, various heat-insulating hoses and hoses for chemical protection, battery banks, insulating sleeves and gaskets, wires and cables. PVC is also an excellent replacement for harmful lead. It cannot be used as a high-frequency circuit in the form of a dielectric. And all because in this case the dielectric losses will be high. Has high conductivity.
Unlike crystalline solids, there is no strict order in the arrangement of particles in an amorphous solid.
Although amorphous solids are capable of maintaining their shape, they do not have a crystal lattice. A certain pattern is observed only for molecules and atoms located in the vicinity. This order is called close order . It is not repeated in all directions and does not persist over long distances, as with crystalline bodies.
Examples of amorphous bodies are glass, amber, artificial resins, wax, paraffin, plasticine, etc.
Features of amorphous bodies
Atoms in amorphous bodies vibrate around points that are randomly located. Therefore, the structure of these bodies resembles the structure of liquids. But the particles in them are less mobile. The time they oscillate around the equilibrium position is longer than in liquids. Jumps of atoms to another position also occur much less frequently.
How do crystalline solids behave when heated? They begin to melt at a certain melting point. And for some time they are simultaneously in a solid and liquid state, until the entire substance melts.
Amorphous solids do not have a specific melting point . When heated, they do not melt, but gradually soften.
Place a piece of plasticine near the heating device. After some time it will become soft. This does not happen instantly, but over a certain period of time.
Since the properties of amorphous bodies are similar to the properties of liquids, they are considered as supercooled liquids with very high viscosity (frozen liquids). Under normal conditions they cannot flow. But when heated, jumps of atoms in them occur more often, viscosity decreases, and amorphous bodies gradually soften. The higher the temperature, the lower the viscosity, and gradually the amorphous body becomes liquid.
Ordinary glass is a solid amorphous body. It is obtained by melting silicon oxide, soda and lime. By heating the mixture to 1400 o C, a liquid glassy mass is obtained. When cooled, liquid glass does not solidify like crystalline bodies, but remains a liquid, the viscosity of which increases and the fluidity decreases. Under normal conditions, it appears to us as a solid body. But in fact it is a liquid that has enormous viscosity and fluidity, so low that it can barely be distinguished by the most ultrasensitive instruments.
The amorphous state of a substance is unstable. Over time, it gradually turns from an amorphous state into a crystalline state. This process occurs at different rates in different substances. We see candy canes becoming covered in sugar crystals. This does not take very much time.
And for crystals to form in ordinary glass, a lot of time must pass. During crystallization, glass loses its strength, transparency, becomes cloudy, and becomes brittle.
Isotropy of amorphous bodies
In crystalline solids, physical properties vary in different directions. But in amorphous bodies they are the same in all directions. This phenomenon is called isotropy .
An amorphous body conducts electricity and heat equally in all directions and refracts light equally. Sound also travels equally in amorphous bodies in all directions.
The properties of amorphous substances are used in modern technologies. Of particular interest are metal alloys that do not have a crystalline structure and belong to amorphous solids. They are called metal glasses . Their physical, mechanical, electrical and other properties differ from those of ordinary metals for the better.
Thus, in medicine they use amorphous alloys whose strength exceeds that of titanium. They are used to make screws or plates that connect broken bones. Unlike titanium fasteners, this material gradually disintegrates and is replaced over time by bone material.
High-strength alloys are used in the manufacture of metal-cutting tools, fittings, springs, and mechanism parts.
An amorphous alloy with high magnetic permeability has been developed in Japan. By using it in transformer cores instead of textured transformer steel sheets, eddy current losses can be reduced by 20 times.
Amorphous metals have unique properties. They are called the material of the future.
A solid is one of the four fundamental states of matter other than liquid, gas and plasma. It is characterized by structural rigidity and resistance to changes in shape or volume. Unlike a liquid, a solid object does not flow or take the shape of the container in which it is placed. A solid does not expand to fill the entire available volume as a gas does.
Atoms in solid body are closely connected with each other, are in an ordered state at the nodes of the crystal lattice (these are metals, ordinary ice, sugar, salt, diamond), or are arranged irregularly, do not have strict repeatability in the structure of the crystal lattice (these are amorphous bodies, such as window glass, rosin, mica or plastic).
Crystal bodies
Crystalline solids or crystals have a distinctive internal feature- a structure in the form of a crystal lattice in which atoms, molecules or ions of a substance occupy a certain position.
The crystal lattice leads to the existence of special flat faces in crystals, which distinguish one substance from another. When exposed x-rays, each crystal lattice emits a characteristic pattern that can be used to identify a substance. The edges of crystals intersect at certain angles that distinguish one substance from another. If the crystal is split, the new faces will intersect at the same angles as the original.
For example, galena - galena, pyrite - pyrite, quartz - quartz. The crystal faces intersect at right angles in galena (PbS) and pyrite (FeS 2), and at other angles in quartz.
Properties of crystals
- constant volume;
- correct geometric shape;
- anisotropy - the difference in mechanical, light, electrical and thermal properties from the direction in the crystal;
- a well-defined melting point, since it depends on the regularity of the crystal lattice. Intermolecular forces holding solid together, are homogeneous, and it takes the same amount of thermal energy to break each interaction simultaneously.
Amorphous bodies
Examples of amorphous bodies that do not have a strict structure and repeatability of crystal lattice cells are: glass, resin, Teflon, polyurethane, naphthalene, polyvinyl chloride.
They have two characteristic properties: isotropy and lack of a specific melting point.
Isotropy of amorphous bodies is understood as the same physical properties of a substance in all directions.
In an amorphous solid, the distance to neighboring nodes of the crystal lattice and the number of neighboring nodes varies throughout the material. Therefore, to break intermolecular interactions, it is required different quantity thermal energy. Consequently, amorphous substances soften slowly over a wide range of temperatures and do not have a clear melting point.
A feature of amorphous solids is that when low temperatures they have the properties of solids, and with increasing temperature - the properties of liquids.
We must remember that not all bodies that exist on planet Earth have crystal structure. Exceptions to the rule are called “amorphous bodies.” How are they different? Based on the translation 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 environment, and their properties are constant. Such substances are called isotropic.
A short description of amorphous bodies
From school course Physicists can remember that amorphous substances have a structure in which the atoms in them are arranged in a chaotic order. Specific place can only have neighboring structures where such an arrangement is forced. 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 (as an example we can take silicon dioxide, whose formula is SiO 2) can simultaneously be in amorphous state and have crystal 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 placement, which will be the first distinctive feature 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 this process began to occur, but at 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 usual life person. 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 organic matter, and their molecules have a thread-like shape. The bodies about which we're talking about, 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 an ordinary person called 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. Special attention it did not cause 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, quite high level strength and corrosion resistance.