Solid are crystalline and amorphous bodies. Crystal - as ice was called in ancient times. And then they began to call quartz and rock crystal a crystal, considering these minerals to be petrified ice. Crystals are natural and artificial (synthetic). They are used in the jewelry industry, optics, radio engineering and electronics, as supports for elements in ultra-precise devices, as an ultrahard abrasive material.
Crystal bodies are characterized by hardness, have a strictly regular position in the space of molecules, ions or atoms, as a result of which a three-dimensional periodic crystal lattice (structure) is formed. Outwardly, this is expressed by a certain symmetry of the shape of the solid and its specific physical properties. In their external form, crystalline bodies reflect the symmetry inherent in the internal "packing" of particles. This determines the equality of the angles between the faces of all crystals consisting of the same substance.
The distances from the center to the center between neighboring atoms will be equal in them (if they are located on one straight line, then this distance will be the same throughout the length of the line). But for atoms lying on a straight line with a different direction, the distance between the centers of the atoms will be different. This circumstance explains anisotropy. Anisotropy is the main thing that distinguishes crystalline bodies from amorphous ones.
More than 90% of solids can be attributed to crystals. In nature, they exist in the form of single crystals and polycrystals. Single crystals are single, whose faces are represented by regular polygons; they are characterized by the presence of a continuous crystal lattice and anisotropy of physical properties.
Polycrystals - bodies consisting of many small crystals that are “fused” among themselves somewhat randomly. Polycrystals are metals, sugar, stones, sand. In such bodies (for example, a metal fragment) anisotropy is usually not manifested due to the random arrangement of elements, although anisotropy is characteristic of a single crystal of this body.
Other properties of crystalline bodies: a strictly defined crystallization and melting temperature (the presence of critical points), strength, elasticity, electrical conductivity, magnetic conductivity, thermal conductivity.
Amorphous - not having a form. So this word is literally translated from Greek. Amorphous bodies are created by nature. For example, amber, wax,
volcanic glass. A person is involved in the creation of artificial amorphous bodies - glass and resins (artificial), paraffin, plastics (polymers), rosin, naphthalene, var.
Amorphous substances do not have a
crystal lattice due to the random arrangement of molecules (atoms, ions) in the body structure. Therefore, the
physical properties for any amorphous body are isotropic - the same in all directions. For amorphous bodies, there is no critical point for the melting point; they gradually soften when heated and pass into viscous liquids. Amorphous bodies are assigned an intermediate (transitional) position between liquids and crystalline bodies: at low temperatures they harden and become elastic, in addition, they can crack upon impact into shapeless pieces. At high temperatures, these same elements exhibit ductility, becoming viscous fluids.
Now you know what crystalline bodies are!