File Name: difference between crystalline and noncrystalline materials .zip
Amorphous solid , any noncrystalline solid in which the atoms and molecules are not organized in a definite lattice pattern. Such solids include glass, plastic , and gel. Solids and liquids are both forms of condensed matter; both are composed of atoms in close proximity to each other.
A crystal or crystalline solid is a solid material whose constituents such as atoms , molecules , or ions are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification.
Examples of large crystals include snowflakes , diamonds , and table salt. Most inorganic solids are not crystals but polycrystals , i. Examples of polycrystals include most metals , rocks, ceramics , and ice. A third category of solids is amorphous solids , where the atoms have no periodic structure whatsoever. Examples of amorphous solids include glass , wax , and many plastics. Despite the name, lead crystal, crystal glass , and related products are not crystals, but rather types of glass, i.
Crystals are often used in pseudoscientific practices such as crystal therapy , and, along with gemstones , are sometimes associated with spellwork in Wiccan beliefs and related religious movements. The scientific definition of a "crystal" is based on the microscopic arrangement of atoms inside it, called the crystal structure. A crystal is a solid where the atoms form a periodic arrangement.
Quasicrystals are an exception, see below. Not all solids are crystals. For example, when liquid water starts freezing, the phase change begins with small ice crystals that grow until they fuse, forming a polycrystalline structure. In the final block of ice, each of the small crystals called " crystallites " or "grains" is a true crystal with a periodic arrangement of atoms, but the whole polycrystal does not have a periodic arrangement of atoms, because the periodic pattern is broken at the grain boundaries.
Most macroscopic inorganic solids are polycrystalline, including almost all metals , ceramics , ice , rocks , etc. Solids that are neither crystalline nor polycrystalline, such as glass , are called amorphous solids , also called glassy , vitreous, or noncrystalline.
These have no periodic order, even microscopically. There are distinct differences between crystalline solids and amorphous solids: most notably, the process of forming a glass does not release the latent heat of fusion , but forming a crystal does. A crystal structure an arrangement of atoms in a crystal is characterized by its unit cell , a small imaginary box containing one or more atoms in a specific spatial arrangement.
The unit cells are stacked in three-dimensional space to form the crystal. The symmetry of a crystal is constrained by the requirement that the unit cells stack perfectly with no gaps. There are possible crystal symmetries, called crystallographic space groups. These are grouped into 7 crystal systems , such as cubic crystal system where the crystals may form cubes or rectangular boxes, such as halite shown at right or hexagonal crystal system where the crystals may form hexagons, such as ordinary water ice.
Crystals are commonly recognized by their shape, consisting of flat faces with sharp angles. These shape characteristics are not necessary for a crystal—a crystal is scientifically defined by its microscopic atomic arrangement, not its macroscopic shape—but the characteristic macroscopic shape is often present and easy to see.
Euhedral crystals are those with obvious, well-formed flat faces. Anhedral crystals do not, usually because the crystal is one grain in a polycrystalline solid.
The flat faces also called facets of a euhedral crystal are oriented in a specific way relative to the underlying atomic arrangement of the crystal : they are planes of relatively low Miller index. As a crystal grows, new atoms attach easily to the rougher and less stable parts of the surface, but less easily to the flat, stable surfaces.
Therefore, the flat surfaces tend to grow larger and smoother, until the whole crystal surface consists of these plane surfaces. See diagram on right. One of the oldest techniques in the science of crystallography consists of measuring the three-dimensional orientations of the faces of a crystal, and using them to infer the underlying crystal symmetry. A crystal's habit is its visible external shape. This is determined by the crystal structure which restricts the possible facet orientations , the specific crystal chemistry and bonding which may favor some facet types over others , and the conditions under which the crystal formed.
By volume and weight, the largest concentrations of crystals in the Earth are part of its solid bedrock. Crystals found in rocks typically range in size from a fraction of a millimetre to several centimetres across, although exceptionally large crystals are occasionally found. Some crystals have formed by magmatic and metamorphic processes, giving origin to large masses of crystalline rock.
The vast majority of igneous rocks are formed from molten magma and the degree of crystallization depends primarily on the conditions under which they solidified.
Such rocks as granite , which have cooled very slowly and under great pressures, have completely crystallized; but many kinds of lava were poured out at the surface and cooled very rapidly, and in this latter group a small amount of amorphous or glassy matter is common. Other crystalline rocks, the metamorphic rocks such as marbles , mica-schists and quartzites , are recrystallized. This means that they were at first fragmental rocks like limestone , shale and sandstone and have never been in a molten condition nor entirely in solution, but the high temperature and pressure conditions of metamorphism have acted on them by erasing their original structures and inducing recrystallization in the solid state.
Other rock crystals have formed out of precipitation from fluids, commonly water, to form druses or quartz veins. Evaporites such as Halite mineral , gypsum and some limestones have been deposited from aqueous solution, mostly owing to evaporation in arid climates. Many living organisms are able to produce crystals, for example calcite and aragonite in the case of most molluscs or hydroxylapatite in the case of vertebrates. The same group of atoms can often solidify in many different ways.
Polymorphism is the ability of a solid to exist in more than one crystal form. For example, water ice is ordinarily found in the hexagonal form Ice I h , but can also exist as the cubic Ice I c , the rhombohedral ice II , and many other forms.
The different polymorphs are usually called different phases. In addition, the same atoms may be able to form noncrystalline phases. For example, water can also form amorphous ice , while SiO 2 can form both fused silica an amorphous glass and quartz a crystal. Likewise, if a substance can form crystals, it can also form polycrystals. For pure chemical elements, polymorphism is known as allotropy.
For example, diamond and graphite are two crystalline forms of carbon , while amorphous carbon is a noncrystalline form. Polymorphs, despite having the same atoms, may have wildly different properties.
For example, diamond is among the hardest substances known, while graphite is so soft that it is used as a lubricant. Polyamorphism is a similar phenomenon where the same atoms can exist in more than one amorphous solid form.
Crystallization is the process of forming a crystalline structure from a fluid or from materials dissolved in a fluid. More rarely, crystals may be deposited directly from gas; see thin-film deposition and epitaxy. Crystallization is a complex and extensively-studied field, because depending on the conditions, a single fluid can solidify into many different possible forms. It can form a single crystal , perhaps with various possible phases , stoichiometries , impurities, defects , and habits.
Or, it can form a polycrystal , with various possibilities for the size, arrangement, orientation, and phase of its grains. The final form of the solid is determined by the conditions under which the fluid is being solidified, such as the chemistry of the fluid, the ambient pressure , the temperature , and the speed with which all these parameters are changing.
Specific industrial techniques to produce large single crystals called boules include the Czochralski process and the Bridgman technique.
Other less exotic methods of crystallization may be used, depending on the physical properties of the substance, including hydrothermal synthesis , sublimation , or simply solvent-based crystallization. Large single crystals can be created by geological processes.
For example, selenite crystals in excess of 10 meters are found in the Cave of the Crystals in Naica, Mexico. Crystals can also be formed by biological processes, see above. Conversely, some organisms have special techniques to prevent crystallization from occurring, such as antifreeze proteins.
An ideal crystal has every atom in a perfect, exactly repeating pattern. The types and structures of these defects may have a profound effect on the properties of the materials.
A few examples of crystallographic defects include vacancy defects an empty space where an atom should fit , interstitial defects an extra atom squeezed in where it does not fit , and dislocations see figure at right. Dislocations are especially important in materials science , because they help determine the mechanical strength of materials.
Another common type of crystallographic defect is an impurity , meaning that the "wrong" type of atom is present in a crystal. For example, a perfect crystal of diamond would only contain carbon atoms, but a real crystal might perhaps contain a few boron atoms as well. These boron impurities change the diamond's color to slightly blue. Likewise, the only difference between ruby and sapphire is the type of impurities present in a corundum crystal.
In semiconductors , a special type of impurity, called a dopant , drastically changes the crystal's electrical properties. Semiconductor devices , such as transistors , are made possible largely by putting different semiconductor dopants into different places, in specific patterns. Twinning is a phenomenon somewhere between a crystallographic defect and a grain boundary. Like a grain boundary, a twin boundary has different crystal orientations on its two sides. But unlike a grain boundary, the orientations are not random, but related in a specific, mirror-image way.
Mosaicity is a spread of crystal plane orientations. A mosaic crystal consists of smaller crystalline units that are somewhat misaligned with respect to each other. In general, solids can be held together by various types of chemical bonds , such as metallic bonds , ionic bonds , covalent bonds , van der Waals bonds , and others.
None of these are necessarily crystalline or non-crystalline. However, there are some general trends as follows. Metals are almost always polycrystalline, though there are exceptions like amorphous metal and single-crystal metals. The latter are grown synthetically.
A microscopically-small piece of metal may naturally form into a single crystal, but larger pieces generally do not. Ionic compound materials are usually crystalline or polycrystalline. In practice, large salt crystals can be created by solidification of a molten fluid, or by crystallization out of a solution. Covalently bonded solids sometimes called covalent network solids are also very common, notable examples being diamond and quartz. Weak van der Waals forces also help hold together certain crystals, such as crystalline molecular solids , as well as the interlayer bonding in graphite.
Polymer materials generally will form crystalline regions, but the lengths of the molecules usually prevent complete crystallization—and sometimes polymers are completely amorphous.
A quasicrystal consists of arrays of atoms that are ordered but not strictly periodic. They have many attributes in common with ordinary crystals, such as displaying a discrete pattern in x-ray diffraction , and the ability to form shapes with smooth, flat faces. Quasicrystals are most famous for their ability to show five-fold symmetry, which is impossible for an ordinary periodic crystal see crystallographic restriction theorem.
Amorphous and crystalline are two states that describe typical solids in chemistry. Using X-ray diffraction experiments, the structure of solids can be categorized into crystalline or amorphous non-crystalline. Solids are among the three basic states of matter that include liquids and gases. They are characterized by a rigid structure of molecules, ions and atoms arranged in an orderly or non-orderly manner. These orderly or non-orderly arrangements have led to the categorization as amorphous and crystalline and this article unfolds the key differences between the two terms. A crystalline solid is that in which the constituent particles are orderly arranged in a three-dimensional pattern called the crystal lattice with uniform intermolecular forces, and the particles intersect at angles characteristic of the crystal. The internal structure has a distinct geometric shape, and it shows a clear cleavage when cut anywhere in the structure.
A crystal or crystalline solid is a solid material whose constituents such as atoms , molecules , or ions are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification. Examples of large crystals include snowflakes , diamonds , and table salt. Most inorganic solids are not crystals but polycrystals , i. Examples of polycrystals include most metals , rocks, ceramics , and ice.
The most basic difference between crystalline solids and noncrystalline solids (NCS) is that a long-range order in the distribution of atoms (ions) or molecules exists in the first case but not in the second. Any real suhstance, including noncrystalline material, is inhomogeneous regardless of its form or scale.
Polymers are unlike other types of materials because of their high molecular weight. Molecular weight is the value used to express the size of a molecule. Water, for example, has a molecular weight of 18 atomic mass units.
The key difference between crystalline and noncrystalline solids is that crystalline solids have an evenly distributed three-dimensional arrangement of atoms, ions , or molecules whereas non-crystalline solids do not have a consistent arrangement of particles. They have differences in their geometries and other physical properties as well. Overview and Key Difference 2.
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