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Amorphous bodies are Crystalline bodies are Properties of Amorphous bodies, how they differ from crystals Solid state physics Liquid crystals Examples
Slide 3
Amorphous bodies
Amorphous bodies are bodies 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)
Slide 4
Crystal bodies
Crystalline bodies are bodies that do not soften, 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 part of the body that has not yet melted (solid).
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Examples
Amorphous substances include glass (artificial and volcanic), natural and artificial resins, glues and other rosin, sugar candy and many other substances. All these substances become cloudy over time (glass “devitrifies,” candy “candied,” etc.). This clouding is associated with the appearance inside the glass or candy of small crystals, the optical properties of which are different from those of the surrounding amorphous medium.
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Properties
Amorphous bodies do not have a crystalline structure and, unlike crystals, do not split to form crystalline faces; as a rule, they are isotropic, that is, they do not exhibit different properties in different directions, and do not have a specific melting point.
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Amorphous bodies, how they differ 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 SiO2 can be in either crystalline or amorphous form (silica).
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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 crystalline. Liquid crystals are mainly organic substances whose molecules have a long thread-like or flat plate shape. Soap bubbles are a prime example of liquid crystals
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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 you apply liquid crystal to some areas electrical voltage, then the liquid crystalline 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.
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Solid state physics
Obtaining materials with specified mechanical, magnetic, electrical and other properties is one of the main directions of modern solid state physics. Amorphous solids occupy an intermediate position between crystalline solids and liquids. Their atoms or molecules are located in relative order
. Understanding the structure of solids (crystalline and amorphous) allows you to create materials with desired properties.
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Concept of amorphous substance
Amorphous substances (from ancient Greek ἀ “non-” and μορφή
"type, form") do not have a crystalline structure and
unlike crystals, they do not split with
the formation of crystalline faces; usually -
isotropic, that is, they do not detect different
properties in different directions, do not have
a certain melting point. To amorphous
substances belong to glass (artificial and
volcanic), natural and artificial
resins, adhesives, etc. Glass - solid state
amorphous substances. Amorphous substances can
be either in a glassy state (with
low temperatures), or in a melt state
(at high temperatures). Amorphous substances
transform into a glassy state when
temperatures below the glass transition temperature T. At
temperatures above T, amorphous substances lead
molten state. Viscosity of amorphous
materials - continuous function of temperature:
the higher the temperature, the lower the viscosity of the amorphous
substances.
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Amorphous bodies
dashes, solids,
atomic lattice
which it does not have
crystalline
structures.
An amorphous body is not
has a long range
in order
arrangement of atoms and
molecules.
For amorphous bodies
characterized by isotropy
properties and lack
certain point
melting: at
increase
temperature
amorphous bodies
gradually
soften and higher
temperature
glass transition (Tg)
turn into liquid
state. Properties of amorphous bodies
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Under external influences, amorphous bodies exhibit
simultaneously elastic properties, like solids, and
fluidity, like a liquid. So, for short-term
impacts (impacts), they behave like solid bodies and when
strong impact breaks into pieces. But at very
upon prolonged exposure, amorphous bodies flow.
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In nature there are substances that simultaneously have
basic properties of crystal and liquid, namely
anisotropy and fluidity. This state of matter
called liquid crystal. Liquid crystals
are mainly organic substances whose molecules
have a long filamentous or flat plate shape.
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Amorphous bodies occupy an intermediate position between
crystalline solids and liquids. Their atoms or
molecules are arranged in relative order. Features of amorphous bodies
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A characteristic feature of amorphous bodies
is their isotropy, i.e. independence
all physical properties (mechanical,
optical, etc.) from the direction. Molecules and
atoms in isotropic solids
are located chaotically, forming only
small local groups containing
several particles (short-range order). In its own way
the structure of amorphous bodies is very close to
liquids. If an amorphous body is heated, then
it gradually softens and turns into
liquid state. (Fig. A - molecular
crystalline body lattice; rice. B –
molecular lattice of an amorphous body) It's interesting that...
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Amorphous
body the same way
is and
resin. If
break it down into
small parts and
the resulting
mass
fill the vessel
then through
for a while
the resin will merge into
one whole and
will take shape
vessel.
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Amorphous bodies-bodies which, when heated, gradually soften and become more viscous.
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Solids
Crystalline Amorphous - Does not have a crystal lattice; -Do not have a melting point; -Isotropic; -Have fluidity; -Able to transform into crystalline and liquid states; -They only have short-range order. Examples are glass, sugar candy, resin.
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The structure of amorphous bodies. Research using an electron microscope shows that in amorphous bodies there is no strict order in the arrangement of their particles. Take a look at the picture showing the arrangement of particles in amorphous quartz. These substances consist of the same particles - molecules of silicon oxide SiO2. Particles of amorphous bodies vibrate 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.
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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 transform a unit mass of a substance into a liquid at the melting temperature 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. Melting process 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.
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Similarities and differences. In physics, only crystalline bodies are usually called solids. Amorphous bodies are considered to be very viscous liquids. They do not have a specific melting point; when heated, they gradually soften and their viscosity decreases. Crystalline bodies have a certain melting point, unchanged at constant pressure. Amorphous bodies are isotropic—the properties of the bodies are the same in all directions. Crystals are anisotropic. The properties of crystals are not the same in different directions.
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Crystals. Studying internal structure crystals using x-ray radiation made it possible to establish that particles in crystals have correct location, i.e. form a crystal lattice. - The points in the crystal lattice corresponding to the most stable equilibrium position of the particles of a solid are called crystal lattice nodes. In physics, a solid means only those substances that have a crystalline structure. There are 4 types of crystal lattice: ionic, atomic, molecular, metal. 1. the nodes contain ions; 2.atoms; 3.molecules; 4.+ metal ions
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Amorphous bodies. Amorphous bodies, in contrast to crystalline bodies, which are characterized by long-range order in the arrangement of atoms, have only short-range order. Amorphous bodies do not have their own melting point. When heated, an amorphous body gradually softens, its molecules change their nearest neighbors more and more easily, its viscosity decreases, and at a sufficiently high temperature it can behave like a low-viscosity liquid.
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Types of deformation. A change in the shape and size of a body is called deformation. The following types of deformation exist: 1. deformation of longitudinal tension and longitudinal compression; 2. all-round tensile and all-round compression deformation; 3.transverse bending deformation; 4.torsional deformation; 5.shear deformation;
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Each of the described types of deformation may be greater or lesser. Any of them can be assessed by absolute deformation ∆a numerical change in any size of a body under the influence of force. Relative deformation Ɛ (Greek epsilon) is a physical quantity that shows what part of the original size of the body a is the absolute deformation ∆a: Ɛ=∆L/L Ɛ= ∆a / a Mechanical stress is a quantity characterizing the action of internal forces in a deformed solid. σ= F / S [Pa]
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Hooke's law. Elastic modulus. Hooke's law: mechanical stress in an elastically deformed body is directly proportional to the relative deformation of this body. σ=kƐ The value k, which characterizes the dependence of mechanical stress in a material on the type of the latter and on external conditions, is called the elastic modulus. σ=EƐ σ=E (∆L/L) E – elastic modulus “Young’s modulus”. Young's modulus is measured by the normal stress that must arise in the material when a relative deformation equal to unity, i.e. when the sample length is doubled. The numerical value of Young's modulus is calculated experimentally and entered into the table. Thomas Young
Solids are characterized by constant shape and volume and are divided into crystalline and amorphous. Crystalline bodies (crystals) are solids whose atoms or molecules occupy ordered positions in space. Particles of crystalline bodies form a regular crystalline spatial lattice in space.
Crystals are divided into: single crystals - these are single homogeneous crystals that have the shape of regular polygons and have a continuous crystal lattice; polycrystals - these are crystalline bodies fused from small, chaotically located crystals. Most solids have a polycrystalline structure (metals, stones, sand, sugar). Crystals are divided into: single crystals - these are single homogeneous crystals that have the shape of regular polygons and have a continuous crystal lattice; polycrystals - these are crystalline bodies fused from small, chaotically located crystals. Most solids have a polycrystalline structure (metals, stones, sand, sugar).
Anisontropy of crystals Anisotropy is observed in crystals - the dependence of physical properties ( mechanical strength, electrical conductivity, thermal conductivity, refraction and absorption of light, diffraction, etc.) on the direction inside the crystal. Anisotropy is observed mainly in single crystals. In polycrystals (for example, in a large piece of metal), anisotropy does not appear in the normal state. Polycrystals consist of a large number of small crystal grains. Although each of them has anisotropy, due to the disorder of their arrangement, the polycrystalline body as a whole loses its anisotropy.
There can be different crystalline forms of the same substance. For example, carbon. Graphite is crystalline carbon. Pencil leads are made from graphite. But there is another form of crystalline carbon, diamond. Diamond is the hardest mineral on earth. Diamond is used to cut glass and saw stones, used for drilling deep wells, diamonds are necessary for the production of the finest metal wire with a diameter of up to thousandths of a millimeter, for example, tungsten filaments for electric lamps. Graphite is crystalline carbon. Pencil leads are made from graphite. But there is another form of crystalline carbon, diamond. Diamond is the hardest mineral on earth. Diamond is used to cut glass and saw stones, and is used for drilling deep wells; diamonds are necessary for the production of the finest metal wire with a diameter of up to thousandths of a millimeter, for example, tungsten filaments for electric lamps.
Isotropy is observed in amorphous bodies - their physical properties the same in all directions. Under external influences, amorphous bodies exhibit both elastic properties (when impacted, they break into pieces like solids) and fluidity (with prolonged exposure, they flow like liquids). At low temperatures, amorphous bodies resemble solids in their properties, and at high temperatures they are similar to very viscous liquids. Amorphous bodies do not have a specific melting point, and therefore no crystallization temperature. When heated, they gradually soften. Amorphous solids occupy an intermediate position between crystalline solids and liquids. Physical properties
