Solid are crystalline and amorphous bodies. Crystal - so in ancient times they called ice. 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 a superhard abrasive material.
Crystalline bodies are characterized by hardness, have a strictly regular position in space of molecules, ions or atoms, resulting in a three-dimensional periodic crystal lattice (structure). Outwardly, this is expressed by a certain symmetry of the shape of a solid body and its certain physical properties. In the external form, crystalline bodies reflect the symmetry inherent in the internalparticle packing. 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 also be equal in them (if they are located on the same straight line, then this distance will be the same along the entire length of the line). But for atoms lying on a straight line with a different direction, the distance between the centers of atoms will be different. This circumstance explains the anisotropy. Anisotropy is the main difference between crystalline and amorphous bodies.
More than 90% of solids can be classified as crystals. In nature, they exist in the form of single crystals and polycrystals. Single crystals - single, the faces of which 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, "grown" together somewhat chaotically. Polycrystals are metals, sugar, stones, sand. In such bodies (for example, a metal fragment), anisotropy usually does not appear due to the random arrangement of elements, although anisotropy is inherent in a single crystal of this body.
Other properties of crystalline bodies: a strictly defined temperature of crystallization and melting (the presence of critical points), strength, elasticity, electrical conductivity, magnetic conductivity, thermal conductivity.
Amorphous - having no shape. So this word is literally translated from Greek. Amorphous bodies are created by nature. For example, amber, wax, volcanic glass. Man 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 chaotic arrangement of molecules (atoms, ions) in the structure of the body. Therefore, the physical properties for any amorphous body are isotropic - the same in all directions. For amorphous bodies, there is no critical melting point; they gradually soften when heated and turn 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 break upon impact into shapeless pieces. At high temperatures, these same elements exhibit plasticity, becoming viscous liquids.
Now you know what crystalline bodies are!
