Single crystalline form of solid Insulin.

Solid is one of the three classical states of matter (the others being gas and liquid). It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a gas does. The atoms in a solid are tightly bound to each other, either in a regular geometric lattice (crystalline solids, which include metals and ordinary water ice) or irregularly (an amorphous solid such as common window glass).

The branch of physics that deals with solids is called solid-state physics, and is the main branch of condensed matter physics (which also includes liquids). Materials science is primarily concerned with the physical and chemical properties of solids. Solid-state chemistry is especially concerned with the synthesis of novel materials, as well as the science of identification and chemical composition.

Metamorphic banded gneiss

Microscopic description[link]

Model of closely packed atoms within a crystalline solid.

The atoms, molecules or ions which make up a solid may be arranged in an orderly repeating pattern, or irregularly. Materials whose constituents are arranged in a regular pattern are known as crystals. In some cases, the regular ordering can continue unbroken over a large scale, for example diamonds, where each diamond is a single crystal. Solid objects that are large enough to see and handle are rarely composed of a single crystal, but instead are made of a large number of single crystals, known as crystallites, whose size can vary from a few nanometers to several meters. Such materials are called polycrystalline. Almost all common metals, and many ceramics, are polycrystalline.

Schematic representation of a random-network glassy form (left) and ordered crystalline lattice (right) of identical chemical composition.

In other materials, there is no long-range order in the position of the atoms. These solids are known as amorphous solids; examples include polystyrene and glass.

Whether a solid is crystalline or amorphous depends on the material involved, and the conditions in which it was formed. Solids which are formed by slow cooling will tend to be crystalline, while solids which are frozen rapidly are more likely to be amorphous. Likewise, the specific crystal structure adopted by a crystalline solid depends on the material involved and on how it was formed.

While many common objects, such as an ice cube or a coin, are chemically identical throughout, many other common materials comprise a number of different substances packed together. For example, a typical rock is an aggregate of several different minerals and mineraloids, with no specific chemical composition. Wood is a natural organic material consisting primarily of cellulose fibers embedded in a matrix of organic lignin. In materials science, composites of more than one constituent material can be designed to have desired properties.

Classes of solids[link]

The forces between the atoms in a solid can take a variety of forms. For example, a crystal of sodium chloride (common salt) is made up of ionic sodium and chlorine, which are held together by ionic bonds. In diamond or silicon, the atoms share electrons and form covalent bonds. In metals, electrons are shared in metallic bonding. Some solids, particularly most organic compounds, are held together with van der Waals forces resulting from the polarization of the electronic charge cloud on each molecule. The dissimilarities between the types of solid result from the differences between their bonding.

Metals[link]

The pinnacle of New York's Chrysler Building, the world's tallest steel-supported brick building, is clad with stainless steel.

Metals typically are strong, dense, and good conductors of both electricity and heat. The bulk of the elements in the periodic table, those to the left of a diagonal line drawn from boron to polonium, are metals. Mixtures of two or more elements in which the major component is a metal are known as alloys.

People have been using metals for a variety of purposes since prehistoric times. The strength and reliability of metals has led to their widespread use in construction of buildings and other structures, as well as in most vehicles, many appliances and tools, pipes, road signs and railroad tracks. Iron and aluminium are the two most commonly used structural metals, and they are also the most abundant metals in the Earth's crust. Iron is most commonly used in the form of an alloy, steel, which contains up to 2.1% carbon, making it much harder than pure iron.

Because metals are good conductors of electricity, they are valuable in electrical appliances and for carrying an electric current over long distances with little energy loss or dissipation. Thus, electrical power grids rely on metal cables to distribute electricity. Home electrical systems, for example, are wired with copper for its good conducting properties and easy machinability. The high thermal conductivity of most metals also makes them useful for stovetop cooking utensils.

The study of metallic elements and their alloys makes up a significant portion of the fields of solid-state chemistry, physics, materials science and engineering.

Metallic solids are held together by a high density of shared, delocalized electrons, known as "metallic bonding". In a metal, atoms readily lose their outermost ("valence") electrons, forming positive ions. The free electrons are spread over the entire solid, which is held together firmly by electrostatic interactions between the ions and the electron cloud.^[1] The large number of free electrons gives metals their high values of electrical and thermal conductivity. The free electrons also prevent transmission of visible light, making metals opaque, shiny and lustrous.

More advanced models of metal properties consider the effect of the positive ions cores on the delocalised electrons. As most metals have crystalline structure, those ions are usually arranged into a periodic lattice. Mathematically, the potential of the ion cores can be treated by various models, the simplest being the nearly free electron model.

Minerals[link]

A collection of various minerals.

Minerals are naturally occurring solids formed through various geological processes under high pressures. To be classified as a true mineral, a substance must have a crystal structure with uniform physical properties throughout. Minerals range in composition from pure elements and simple salts to very complex silicates with thousands of known forms. In contrast, a rock sample is a random aggregate of minerals and/or mineraloids, and has no specific chemical composition. The vast majority of the rocks of the Earth's crust consist of quartz (crystalline SiO₂), feldspar, mica, chlorite, kaolin, calcite, epidote, olivine, augite, hornblende, magnetite, hematite, limonite and a few other minerals. Some minerals, like quartz, mica or feldspar are common, while others have been found in only a few locations worldwide. The largest group of minerals by far is the silicates (most rocks are ≥95% silicates), which are composed largely of silicon and oxygen, with the addition of ions of aluminium, magnesium, iron, calcium and other metals.

Ceramics[link]

Si₃N₄ ceramic bearing parts

Ceramic solids are composed of inorganic compounds, usually oxides of chemical elements. They are chemically inert, and often are capable of withstanding chemical erosion that occurs in an acidic or caustic environment. Ceramics generally can withstand high temperatures ranging from 1000 to 1600 °C (1800 to 3000 °F). Exceptions include non-oxide inorganic materials, such as nitrides, borides and carbides.

Traditional ceramic raw materials include clay minerals such as kaolinite, more recent materials include aluminium oxide (alumina). The modern ceramic materials, which are classified as advanced ceramics, include silicon carbide and tungsten carbide. Both are valued for their abrasion resistance, and hence find use in such applications as the wear plates of crushing equipment in mining operations.

Most ceramic materials, such as alumina and its compounds, are formed from fine powders, yielding a fine grained polycrystalline microstructure which is filled with light scattering centers comparable to the wavelength of visible light. Thus, they are generally opaque materials, as opposed to transparent materials. Recent nanoscale (e.g. sol-gel) technology has, however, made possible the production of polycrystalline transparent ceramics such as transparent alumina and alumina compounds for such applications as high-power lasers. Advanced ceramics are also used in the medicine, electrical and electronics industries.

Ceramic engineering is the science and technology of creating solid-state ceramic materials, parts and devices. This is done either by the action of heat, or, at lower temperatures, using precipitation reactions from chemical solutions. The term includes the purification of raw materials, the study and production of the chemical compounds concerned, their formation into components, and the study of their structure, composition and properties.

Mechanically speaking, ceramic materials are brittle, hard, strong in compression and weak in shearing and tension. Brittle materials may exhibit significant tensile strength by supporting a static load. Toughness indicates how much energy a material can absorb before mechanical failure, while fracture toughness (denoted K_Ic ) describes the ability of a material with inherent microstructural flaws to resist fracture via crack growth and propagation. If a material has a large value of fracture toughness, the basic principles of fracture mechanics suggest that it will most likely undergo ductile fracture. Brittle fracture is very characteristic of most ceramic and glass-ceramic materials which typically exhibit low (and inconsistent) values of K_Ic.

For example of applications of ceramics, the extreme hardness of Zirconia is utilized in the manufacture of knife blades, as well as other industrial cutting tools. Ceramics such as alumina, boron carbide and silicon carbide have been used in bulletproof vests to repel large-caliber rifle fire. Silicon nitride parts are used in ceramic ball bearings, where their high hardness makes them wear resistant. In general, ceramics are also chemically resistant and can be used in wet environments where steel bearings would be susceptible to oxidation (or rust).

Radial rotor made from Si₃N₄ for a gas turbine engine

As another example of ceramic applications, in the early 1980s, Toyota researched production of an adiabatic ceramic engine with an operating temperature of over 6000 °F (3300 °C). Ceramic engines do not require a cooling system and hence allow a major weight reduction and therefore greater fuel efficiency. In a conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts. Work is also being done in developing ceramic parts for gas turbine engines. Turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. However, such engines are not in production because the manufacturing of ceramic parts in the sufficient precision and durability is difficult and costly. Processing methods often result in a wide distribution of microscopic flaws which frequently play a detrimental role in the sintering process, resulting in the proliferation of cracks, and ultimate mechanical failure.

Glass ceramics[link]

A high strength glass-ceramic cooktop with negligible thermal expansion.

Glass-ceramic materials share many properties with both non-crystalline glasses and crystalline ceramics. They are formed as a glass, and then partially crystallized by heat treatment, producing both amorphous and crystalline phases so that crystalline grains are embedded within a non-crystalline intergranular phase.

Glass-ceramics are used to make cookware (originally known by the brand name CorningWare) and stovetops which have both high resistance to thermal shock and extremely low permeability to liquids. The negative coefficient of thermal expansion of the crystalline ceramic phase can be balanced with the positive coefficient of the glassy phase. At a certain point (~70% crystalline) the glass-ceramic has a net coefficient of thermal expansion close to zero. This type of glass-ceramic exhibits excellent mechanical properties and can sustain repeated and quick temperature changes up to 1000 °C.

Glass ceramics may also occur naturally when lightning strikes the crystalline (e.g. quartz) grains found in most beach sand. In this case, the extreme and immediate heat of the lightning (~2500 °C) creates hollow, branching rootlike structures called fulgurite via fusion.

Organic solids[link]

The individual wood pulp fibers in this sample are around 10 µm in diameter.

Organic chemistry studies the structure, properties, composition, reactions, and preparation by synthesis (or other means) of chemical compounds of carbon and hydrogen, which may contain any number of other elements such as nitrogen, oxygen and the halogens: fluorine, chlorine, bromine and iodine. Some organic compounds may also contain the elements phosphorus or sulfur. Examples of organic solids include wood, paraffin wax, naphthalene and a wide variety of polymers and plastics.

Wood[link]

Wood is a natural organic material consisting primarily of cellulose fibers embedded in a matrix of lignin. Regarding mechanical properties, the fibers are strong in tension, and the lignin matrix resists compression. Thus wood has been an important construction material since humans began building shelters and using boats. Wood to be used for construction work is commonly known as lumber or timber. In construction, wood is not only a structural material, but is also used to form the mould for concrete.

Wood-based materials are also extensively used for packaging (e.g. cardboard) and paper which are both created from the refined pulp. The chemical pulping processes use a combination of high temperature and alkaline (kraft) or acidic (sulfite) chemicals to break the chemical bonds of the lignin before burning it out.

Polymers[link]

STM image of self-assembled supramolecular chains of the organic semiconductor quinacridone on graphite.

One important property of carbon in organic chemistry is that it can form certain compounds, the individual molecules of which are capable of attaching themselves to one another, thereby forming a chain or a network. The process is called polymerization and the chains or networks polymers, while the source compound is a monomer. Two main groups of polymers exist: those artificially manufactured are referred to as industrial polymers or synthetic polymers (plastics) and those naturally occurring as biopolymers.

Monomers can have various chemical substituents, or functional groups, which can affect the chemical properties of organic compounds, such as solubility and chemical reactivity, as well as the physical properties, such as hardness, density, mechanical or tensile strength, abrasion resistance, heat resistance, transparency, color, etc.. In proteins, these differences give the polymer the ability to adopt a biologically active conformation in preference to others (see self-assembly).

Household items made of various kinds of plastic.

People have been using natural organic polymers for centuries in the form of waxes and shellac which is classified as a thermoplastic polymer. A plant polymer named cellulose provided the tensile strength for natural fibers and ropes, and by the early 19th century natural rubber was in widespread use. Polymers are the raw materials (the resins) used to make what we commonly call plastics. Plastics are the final product, created after one or more polymers or additives have been added to a resin during processing, which is then shaped into a final form. Polymers which have been around, and which are in current widespread use, include carbon-based polyethylene, polypropylene, polyvinyl chloride, polystyrene, nylons, polyesters, acrylics, polyurethane, and polycarbonates, and silicon-based silicones. Plastics are generally classified as "commodity", "specialty" and "engineering" plastics.

Composite materials[link]

Simulation of the outside of the Space Shuttle as it heats up to over 1500 °C during re-entry

A cloth of woven carbon fiber filaments, a common element in composite materials

Composite materials contain two or more macroscopic phases, one of which is often ceramic. For example, a continuous matrix, and a dispersed phase of ceramic particles or fibers.

Applications of composite materials range from structural elements such as steel-reinforced concrete, to the thermally insulative tiles which play a key and integral role in NASA's Space Shuttle thermal protection system which is used to protect the surface of the shuttle from the heat of re-entry into the Earth's atmosphere. One example is Reinforced Carbon-Carbon (RCC), the light gray material which withstands reentry temperatures up to 1510 °C (2750 °F) and protects the nose cap and leading edges of Space Shuttle's wings. RCC is a laminated composite material made from graphite rayon cloth and impregnated with a phenolic resin. After curing at high temperature in an autoclave, the laminate is pyrolized to convert the resin to carbon, impregnated with furfural alcohol in a vacuum chamber, and cured/pyrolized to convert the furfural alcohol to carbon. In order to provide oxidation resistance for reuse capability, the outer layers of the RCC are converted to silicon carbide.

Domestic examples of composites can be seen in the "plastic" casings of television sets, cell-phones and so on. These plastic casings are usually a composite made up of a thermoplastic matrix such as acrylonitrile butadiene styrene (ABS) in which calcium carbonate chalk, talc, glass fibers or carbon fibers have been added for strength, bulk, or electro-static dispersion. These additions may be referred to as reinforcing fibers, or dispersants, depending on their purpose.

Thus, the matrix material surrounds and supports the reinforcement materials by maintaining their relative positions. The reinforcements impart their special mechanical and physical properties to enhance the matrix properties. A synergism produces material properties unavailable from the individual constituent materials, while the wide variety of matrix and strengthening materials provides the designer with the choice of an optimum combination.

Semiconductors[link]

Semiconductor chip on crystalline silicon substrate.

Semiconductors are materials that have an electrical resistivity (and conductivity) between that of metallic conductors and non-metallic insulators. They can be found in the periodic table moving diagonally downward right from boron. They separate the electrical conductors (or metals, to the left) from the insulators (to the right).

Devices made from semiconductor materials are the foundation of modern electronics, including radio, computers, telephones, etc. Semiconductor devices include the transistor, solar cells, diodes and integrated circuits. Solar photovoltaic panels are large semiconductor devices that directly convert light into electrical energy.

In a metallic conductor, current is carried by the flow of electrons", but in semiconductors, current can be carried either by electrons or by the positively charged "holes" in the electronic band structure of the material. Common semiconductor materials include silicon, germanium and gallium arsenide.

Nanomaterials[link]

Bulk silicon (left) and silicon nanopowder (right)

Many traditional solids exhibit different properties when they shrink to nanometer sizes. For example, nanoparticles of usually yellow gold and gray silicon are red in color; gold nanoparticles melt at much lower temperatures (~300 °C for 2.5 nm size) than the gold slabs (1064 °C);^[2] and metallic nanowires are much stronger than the corresponding bulk metals.^[3][4] The high surface area of nanoparticles makes them extremely attractive for certain applications in the field of energy. For example, platinum metals may be provide improvements as automotive fuel catalysts, as well as proton exchange membrane (PEM) fuel cells. Also, ceramic oxides (or cermets) of lanthanum, cerium, manganese and nickel are now being developed as solid oxide fuel cells (SOFC). Lithium, lithium–titanate and tantalum nanoparticles are being applied in lithium ion batteries. Silicon nanoparticles have been shown to dramatically expand the storage capacity of lithium ion batteries during the expansion/contraction cycle. Silicon nanowires cycle without significant degradation and present the potential for use in batteries with greatly expanded storage times. Silicon nanoparticles are also being used in new forms of solar energy cells. Thin film deposition of silicon quantum dots on the polycrystalline silicon substrate of a photovoltaic (solar) cell increases voltage output as much as 60% by fluorescing the incoming light prior to capture. Here again, surface area of the nanoparticles (and thin films) plays a critical role in maximizing the amount of absorbed radiation.

Biomaterials[link]

Collagen fibers of woven bone

Many natural (or biological) materials are complex composites with remarkable mechanical properties. These complex structures, which have risen from hundreds of million years of evolution, are inspiring materials scientists in the design of novel materials. Their defining characteristics include structural hierarchy, multifunctionality and self-healing capability. Self-organization is also a fundamental feature of many biological materials and the manner by which the structures are assembled from the molecular level up. Thus, self-assembly is emerging as a new strategy in the chemical synthesis of high performance biomaterials.

Physical properties[link]

Physical properties of elements and compounds which provide conclusive evidence of chemical composition include odor, color, volume, density (mass per unit volume), melting point, boiling point, heat capacity, physical form and shape at room temperature (solid, liquid or gas; cubic, trigonal crystals, etc.), hardness, porosity, index of refraction and many others. This section discusses some physical properties of materials in the solid state.

Mechanical[link]

Granite rock formation in the Chilean Patagonia. Like most inorganic minerals formed by oxidation in the Earth's atmosphere, granite consists primarily of crystalline silica SiO₂ and alumina Al₂O₃.

The mechanical properties of materials describe characteristics such as their strength and resistance to deformation. For example, steel beams are used in construction because of their high strength, meaning that they neither break nor bend significantly under the applied load.

Mechanical properties include elasticity and plasticity, tensile strength, compressive strength, shear strength, fracture toughness, ductility (low in brittle materials), and indentation hardness. Solid mechanics is the study of the behavior of solid matter under external actions such as external forces and temperature changes.

A solid does not exhibit macroscopic flow, as fluids do. Any degree of departure from its original shape is called deformation. The proportion of deformation to original size is called strain. If the applied stress is sufficiently low, almost all solid materials behave in such a way that the strain is directly proportional to the stress (Hooke's law). The coefficient of the proportion is called the modulus of elasticity or Young's modulus. This region of deformation is known as the linearly elastic region. Three models can describe how a solid responds to an applied stress:

• Elasticity – When an applied stress is removed, the material returns to its undeformed state.
• Viscoelasticity – These are materials that behave elastically, but also have damping. When the applied stress is removed, work has to be done against the damping effects and is converted to heat within the material. This results in a hysteresis loop in the stress–strain curve. This implies that the mechanical response has a time-dependence.
• Plasticity – Materials that behave elastically generally do so when the applied stress is less than a yield value. When the stress is greater than the yield stress, the material behaves plastically and does not return to its previous state. That is, irreversible plastic deformation (or viscous flow) occurs after yield which is permanent.

Many materials become weaker at high temperatures. Materials which retain their strength at high temperatures, called refractory materials, are useful for many purposes. For example, glass-ceramics have become extremely useful for countertop cooking, as they exhibit excellent mechanical properties and can sustain repeated and quick temperature changes up to 1000 °C. In the aerospace industry, high performance materials used in the design of aircraft and/or spacecraft exteriors must have a high resistance to thermal shock. Thus, synthetic fibers spun out of organic polymers and polymer/ceramic/metal composite materials and fiber-reinforced polymers are now being designed with this purpose in mind.

Thermal[link]

Normal modes of atomic vibration in a crystalline solid.

Because solids have thermal energy, their atoms vibrate about fixed mean positions within the ordered (or disordered) lattice. The spectrum of lattice vibrations in a crystalline or glassy network provides the foundation for the kinetic theory of solids. This motion occurs at the atomic level, and thus cannot be observed or detected without highly specialized equipment, such as that used in spectroscopy.

Thermal properties of solids include thermal conductivity, which is the property of a material that indicates its ability to conduct heat. Solids also have a specific heat capacity, which is the capacity of a material to store energy in the form of heat (or thermal lattice vibrations).

Electrical[link]

Video of superconducting levitation of YBCO

Electrical properties include conductivity, resistance, impedance and capacitance. Electrical conductors such as metals and alloys are contrasted with electrical insulators such as glasses and ceramics. Semiconductors behave somewhere in between. Whereas conductivity in metals is caused by electrons, both electrons and holes contribute to current in semiconductors. Alternatively, ions support electric current in ionic conductors.

Many materials also exhibit superconductivity at low temperatures; they include metallic elements such as tin and aluminium, various metallic alloys, some heavily doped semiconductors, and certain ceramics. The electrical resistivity of most electrical (metallic) conductors generally decreases gradually as the temperature is lowered, but remains finite. In a superconductor however, the resistance drops abruptly to zero when the material is cooled below its critical temperature. An electric current flowing in a loop of superconducting wire can persist indefinitely with no power source.

A dielectric, or electrical insulator, is a substance that is highly resistant to the flow of electric current. A dielectric, such as plastic, tends to concentrate an applied electric field within itself which property is used in capacitors. A capacitor is an electrical device that can store energy in the electric field between a pair of closely spaced conductors (called 'plates'). When voltage is applied to the capacitor, electric charges of equal magnitude, but opposite polarity, build up on each plate. Capacitors are used in electrical circuits as energy-storage devices, as well as in electronic filters to differentiate between high-frequency and low-frequency signals.

Electro-mechanical[link]

Piezoelectricity is the ability of crystals to generate a voltage in response to an applied mechanical stress. The piezoelectric effect is reversible in that piezoelectric crystals, when subjected to an externally applied voltage, can change shape by a small amount. Polymer materials like rubber, wool, hair, wood fiber, and silk often behave as electrets. For example, the polymer polyvinylidene fluoride (PVDF) exhibits a piezoelectric response several times larger than the traditional piezoelectric material quartz (crystalline SiO₂). The deformation (~0.1%) lends itself to useful technical applications such as high-voltage sources, loudspeakers, lasers, as well as chemical, biological, and acousto-optic sensors and/or transducers.

Optical[link]

Materials can transmit (e.g. glass) or reflect (e.g. metals) visible light.

Many materials will transmit some wavelengths while blocking others. For example, window glass is transparent to visible light, but much less so to most of the frequencies of ultraviolet light that cause sunburn. This property is used for frequency-selective optical filters, which can alter the color of incident light.

For some purposes, both the optical and mechanical properties of a material can be of interest. For example, the sensors on an infrared homing ("heat-seeking") missile must be protected by a cover which is transparent to infrared radiation. The current material of choice for high-speed infrared-guided missile domes is single-crystal sapphire. The optical transmission of sapphire does not actually extend to cover the entire mid-infrared range (3–5 µm), but starts to drop off at wavelengths greater than approximately 4.5 µm at room temperature. While the strength of sapphire is better than that of other available mid-range infrared dome materials at room temperature, it weakens above 600 °C. A long standing trade-off exists between optical bandpass and mechanical durability; new materials such as transparent ceramics or optical nanocomposites may provide improved performance.

Guided lightwave transmission involves the field of fiber optics and the ability of certain glasses to transmit, simultaneously and with low loss of intensity, a range of frequencies (multi-mode optical waveguides) with little interference between them. Optical waveguides are used as components in integrated optical circuits or as the transmission medium in optical communication systems.

Opto-electronic[link]

A solar cell or photovoltaic cell is a device that converts light energy into electrical energy. Fundamentally, the device needs to fulfill only two functions: photo-generation of charge carriers (electrons and holes) in a light-absorbing material, and separation of the charge carriers to a conductive contact that will transmit the electricity (simply put, carrying electrons off through a metal contact into an external circuit). This conversion is called the photoelectric effect, and the field of research related to solar cells is known as photovoltaics.

Solar cells have many applications. They have long been used in situations where electrical power from the grid is unavailable, such as in remote area power systems, Earth-orbiting satellites and space probes, handheld calculators, wrist watches, remote radiotelephones and water pumping applications. More recently, they are starting to be used in assemblies of solar modules (photovoltaic arrays) connected to the electricity grid through an inverter, that is not to act as a sole supply but as an additional electricity source.

All solar cells require a light absorbing material contained within the cell structure to absorb photons and generate electrons via the photovoltaic effect. The materials used in solar cells tend to have the property of preferentially absorbing the wavelengths of solar light that reach the earth surface. However, some solar cells are optimized for light absorption beyond Earth's atmosphere as well.

References[link]

v t e States of matter Solid Liquid Gas / Vapor Plasma Low energy Bose–Einstein condensate · Fermionic condensate · Quantum Hall · Rydberg matter · Strange matter · Superfluid · Supersolid High energy Degenerate matter · QCD matter · Quark–gluon plasma  · Supercritical fluid Other states Colloid · Glass · Liquid crystal · Magnetically ordered (Antiferromagnet, Ferrimagnet, Ferromagnet) · String-net liquid · Superglass Transitions Boiling · Boiling point · Condensation · Critical line · Critical point · Crystallization · Deionization · Deposition · Evaporation · Flash evaporation · Freezing · Ionization · Lambda point · Melting · Melting point · Regelation · Saturated fluid · Sublimation · Supercooling · Triple point · Vaporization Quantities Enthalpy of fusion · Enthalpy of sublimation · Enthalpy of vaporization · Latent heat · Latent internal energy · Trouton's ratio · Volatility Concepts Binodal · Compressed fluid · Cooling curve · Equation of state · Leidenfrost effect · Mpemba effect · Order and disorder (physics) · Spinodal · Superconductivity · Superheated vapor · Superheating · Thermo-dielectric effect

Solid Snake (ソリッド・スネーク, Soriddo Sunēku^?), real name David (デイビッド, Deibiddo^?),^[2][3] is a fictional character and the protagonist of Konami's Metal Gear series. Created by Hideo Kojima, Snake is introduced in the first game of the series, Metal Gear from 1987. Snake has appeared in the majority of subsequent games and spin-offs. Japanese voice actor Akio Ōtsuka voices Snake in Japanese, while actor and screenwriter David Hayter provides the English voice of the character.

Introduced in Metal Gear, Solid Snake is a combination of spy, special operations soldier, and mercenary commando of FOXHOUND – a black operations and espionage unit. He is tasked with disarming and destroying the latest incarnation of Metal Gear, a bipedal nuclear weapon-armed mecha. Controlled by the player, Solid Snake must act alone, supported via radio by commanding officers and specialists. While during his first two appearances Snake's designs were references to Hollywood films, by Metal Gear Solid he was given a consistent design by artist Yoji Shinkawa alongside an established personality.

The character of Solid Snake has been well-received by critics to the point he appeared in several lists of best characters in gaming history. His development in the series has been praised although his accelerated aging in Metal Gear Solid 4: Guns of the Patriots resulted in mixed reactions.

Description[link]

This section may contain original research. Please improve it by verifying the claims made and adding references. Statements consisting only of original research may be removed. More details may be available on the talk page. (December 2010)

While during his debut appearances, Solid Snake's visual appearances were references to popular actors, he was given his own consistent design in Metal Gear Solid. Such design shows him as a an brown haired adult wearing dark sneaking suit as well as a bandana. This appearance suffered little changes in the sequel besides the fact Snake was older but during the beginning of the Plant Chapter he disguises himself wearing a uniform and bleaches his hair. By Metal Gear Solid 4, Solid Snake suffered a notable change as a result of his accelerated aging which makes him look like an elder. Nevertheless, he still wears his sneaking suit for missions and has access to different disguises to look like other characters as well as his younger self.

Solid Snake has been on the battlefield for most of his life,^[4] a hardened veteran, he has his emotions buried very deep inside himself. Every one of his missions has different motives.^[5] He is immediately shown as a loner^[6][7] and with no intentions of taking orders from anyone anymore,^[8] he shows no sign of longing for the army or the country he was part of.^[9]

Along with these traits he has a more human side, being flirtatious,^[10] self-sacrificing^[11] and with a strong belief that even on a battlefield friendship^[12] and love^[13] can flourish, and that violence is not glorious.^[14] Although the last bit is debatable due to statements from his enemies and at least one of his allies that he might enjoy all the killing, and even being labelled as being truly evil at one point.^[15][16][17]

[edit] Metal Gear series

[edit] Metal Gear games

Metal Gear, initially released in 1987, introduces Solid Snake, the rookie recruit of the elite special-forces unit FOXHOUND. Snake is sent by team leader Big Boss into the rogue nation Outer Heaven to rescue his missing teammate Gray Fox and discover who or what the "METAL GEAR" mentioned is.^[18][19] As his mission progresses he finds out that he has been set up; the leader of Outer Heaven is actually Big Boss, who intends to use Metal Gear—an experimental, nuclear-armed mecha—to establish Outer Heaven as a nuclear power.^[20] After destroying the Metal Gear itself, he then confronts Big Boss and defeats him.^[21]

In the sequel, titled Metal Gear 2: Solid Snake and initially released only in Japan for the MSX2, follows after the original Metal Gear rather than Snake's Revenge; indeed, all later games ignore the events of Snake's Revenge.^[22]

Metal Gear 2: Solid Snake sees Solid Snake once again called up to infiltrate a heavily fortified enemy base, this time in Zanzibarland. Zanzibarland has aggravated an international oil crisis and declared themselves a nuclear power by kidnapping Dr. Kio Marv, the creator of a bio-engineered algae that produces an oil substitute, and Dr. Pettrovich Madnar, the developer of the original Metal Gear.^[23] Snake infiltrates the base and discovers that Pettrovich and his former comrade Gray Fox have defected to Zanzibar Land, and that Zanzibar Land is led by Big Boss.^[24] Snake destroys their new Metal Gear D, and defeats his former comrades Gray Fox and Big Boss.^[25][26]

[edit] Metal Gear Solid games

Metal Gear Solid sees Solid Snake pulled out of retirement by Colonel Campbell in a mission to deal with FOXHOUND. Under the leadership of Liquid Snake, FOXHOUND has gone rogue, seizing Shadow Moses Island, an isolated American nuclear weapons disposal facility.^[27] Snake infiltrates the base and meets up with Meryl Silverburgh, a rookie soldier, and Dr. Hal "Otacon" Emmerich, the designer of Metal Gear REX. Snake defeats each member of FOXHOUND one by one, destroys Metal Gear REX, and confronts Liquid. Liquid reveals that he and Solid are twin brothers artificially conceived from Big Boss' genes during a government project designed to create the perfect soldier titled "Les Enfants Terribles", in which one brother was genetically modified to be superior over the other.^[28] Liquid harbors a strong resentment towards Snake since his brother was given their father's dominant "soldier genes" and Liquid was cast aside. After a grueling series of battles, Liquid dies from the Fox-Die virus that was previously implanted into Snake in order to wipe out FOXHOUND without risking any damage to Metal Gear REX and the Genome soldiers' bodies for retrieval.^[29] In the end, it is revealed that Liquid got Big Boss' superior "soldier genes", not Solid.^[30]

Solid Snake is the playable character of the extensive prologue sequence of Metal Gear Solid 2: Sons of Liberty, in which he is sent by the anti-proliferation organization Philanthropy to infiltrate a cargo tanker and photograph Metal Gear RAY, the latest Metal Gear model.^[31] During the operation, however, the Metal Gear RAY is hijacked and the tanker destroyed, with the apparently dead Snake framed for the deed.^[32] The remainder of Sons of Liberty follows the actions of the rookie FOXHOUND agent Raiden (the character now controlled by the player), who has been assigned to rescue the U.S. President and a number of other government officials being held hostage at a remote offshore oil shell facility. Solid Snake, who survived the explosion in the prologue, appears throughout the main portion of the game (initially adopting the pseudonym Iroquois Pliskin (イロコィ・プリスキン , Irokoi Purisukin^?), as a non-playable character who assists Raiden.^[33]

The PlayStation 3 game Metal Gear Solid 4: Guns of the Patriots features an aged Snake, once again the main protagonist and identified as Old Snake (オールド・スネーク, Ōrudo Sunēku^?) by the game. On account of his genetic code being a potential threat if it fell into enemy hands, he was designed with a short life span; as such, while Snake is only 42 years old, he has the body of an old man.^[34] In the game, he wears a sneaking suit outfitted with "Octocamo" technology, which allows him to blend with his environment, as well as a face mask which alters his appearance.^[35] Snake is once again enlisted by Campbell to defeat Revolver Ocelot who is following Big Boss' by taking control of the Patriots' A.I.s.^[36] Snake and his allies are forced to destroy the Patriots' A.I.s to stop Ocelot, and fights most of his soldiers, until killing Ocelot. Having learned that his rapid aging can cause an epidemic because of the FOXDIE virus mutating, Snake tries to commit suicide but changes his mind and is then confronted by the surviving Big Boss who reveals he can spend the rest of his life peacefully. After making up with Big Boss, Snake decides to live out the remainder of his life in peace.^[37]

In spinoffs[link]

Three Metal Gear spinoffs, which do not follow the storyline of the main Kojima-directed series, were directed by Shinta Nojiri.^[38] The first of these games is the Game Boy Color version of Metal Gear Solid (released in Japan as Metal Gear: Ghost Babel). In Ghost Babel, Solid Snake infiltrates a rebuilt Outer Heaven (now called Galuade) to defeat a FOXHOUND-like team of rogue agents called Black Chamber and destroy a stolen Metal Gear prototype, Gander. While the promotional art for the game was drawn by Yoji Shinkawa, the actual in-game character designs were done by Ikuya Nakamura.

In Metal Gear Acid, Solid Snake must retrieve "Pythagoras" from the Lobito Physics and Research Laboratory, in order to satisfy hijackers who have kidnapped presidential candidate Viggo Hach. This mission is complicated by La Clown, an expert mimic who impersonates Solid Snake's contact Teliko, and subtle brainwashing that nearly convinces him that he is Hans Davis, a ruthless scientist that worked at the Lobito facility. He overcomes both and contacts the real Teliko, then destroys the latest model of Metal Gear, Metal Gear KODOQUE. The sequel, Metal Gear Acid 2, features a main character who is not the real Solid Snake, but a clone created from tissue samples of the Solid Snake from the original Metal Gear Acid, following the events of the Lobito Island mission; the Solid Snake from the original Acid is dead.

Though Snake does not explicitly appear in Metal Gear Solid: Portable Ops, he is mentioned, though not referred to by name; Elisa, a teenage German psychic with multiple personalities, has a prophetic vision of Naked Snake's future as she dies: she mentions that one of his sons will save the world after another son (Liquid Snake) brings it to ruin.^[39] He appears in his Metal Gear Solid 4 form as a recruitable character in Portable Ops Plus.^[40] He is also playable in an updated pack from Metal Gear Online.^[41]

Other appearances[link]

Solid Snake has appeared in a number of other games, including other Konami games, and more unusually, under license in games developed and published by other companies, such as Sony and Nintendo.

Hideo Kojima makes a habit of referencing his previous work. In the Kojima-produced Boktai 2: Solar Boy Django (and Boktai 3: Sabata's Counterattack), Snake appears as an unnamed character who sells items to the player. Konami's Evolution Skateboarding features Snake and Raiden as hidden characters, as well two stages set in the Big Shell (the Skateboarding minigame in Metal Gear Solid 2: Substance is a demo of Evolution Skateboarding composed exclusively of these elements).^[42]

Solid Snake also appears in both halves of a crossover between the Metal Gear and Ape Escape franchises: the Ape Escape monkeys appear with Solid Snake in the "Snake vs. Monkey" minigame featured in Metal Gear Solid 3: Snake Eater. In turn, Snake (voiced by Peter Lurie in the English version instead of David Hayter, his usual voice actor) appears in the corresponding Metal Gear Solid minigame featured in Ape Escape 3, where he is rescued by Pipo Snake. Snake's character design in this mini-game is taken directly from Naked Snake's.

He has also appeared in a pair of cross-company fighting games. In DreamMix TV World Fighters, Solid Snake appears as a playable character alongside other third-party characters such as Bomberman and Convoy (Optimus Prime). Similarly, in Super Smash Bros. Brawl, a popular fighting game from Nintendo, Solid Snake appeared alongside Nintendo-owned characters such as Mario and Donkey Kong, and Sega's Sonic the Hedgehog. According to producer Masahiro Sakurai, Snake's inclusion in Brawl was done under Kojima's request, who wanted Snake to be featured.^[43]

Snake has appeared as a playable character in the Nintendo DS game, New International Track & Field, alongside fellow Konami characters such as Sparkster and Simon Belmont, as well as new original characters.^[44] Also, Old Snake has appeared in the Japanese version of Scribblenauts, having been published by Konami in that region.^[45]

Customizations in Media Molecule's LittleBigPlanet for the PlayStation 3 allow the player character, Sackboy, to take on the appearance of Old Snake.^[46]

Creation and development[link]

Much as Metal Gear began as a pastiche of action movies of the time, Solid Snake began as a pastiche of contemporary action movie heroes. For example, on the cover artwork of the original Metal Gear, he resembles Michael Biehn in The Terminator, and the in-game portrait of Snake in Metal Gear 2: Solid Snake resembles Mel Gibson in the game's opening sequence.^[47] Solid Snake was even named after another fictional special forces operative: Snake Plissken, Kurt Russell's character in Escape from New York.^[48][49] In Guns of the Patriots, Snake is modeled after Lee Van Cleef, who appeared in Escape from New York.^[50] His real name, David, is a tribute to the film 2001: A Space Odyssey that has a character with the same name.^[51] Kojima later described Snake's role in the original Metal Gear as the "player's presence", contrasting the defined personality Solid Snake acquired in Metal Gear Solid.^[52]

In addition to expanding Solid Snake's backstory, as the first Metal Gear game to feature voice acting Metal Gear Solid established his characteristic voice and appearance.^[53] Yoji Shinkawa's Solid Snake design, characterized by his navy blue bandanna and "sneaking suit", would serve as the template for all future incarnations of Snake in later Metal Gear games. According to Shinkawa, Snake's physique in Metal Gear Solid was based on that of action star Jean-Claude Van Damme, while his facial appearance in the same game was inspired by actor Christopher Walken. Shinkawa described his rendition of Solid Snake from Metal Gear Solid as a "middle ground" between the younger Snake who graced the cover artwork of the first Metal Gear and the middle-aged Snake from the MSX2 version of Metal Gear 2.^[49][54] For the initial events from the Big Shell chapter from Metal Gear Solid 2, Snake's visual appearance was sightly modified with his hair being more blonde.^[55] Solid Snake became one of the characters easiest to draw by Shinkawa as he notes that his appearance is consistence, suffering minor changes across the games.^[56]

Various scenes from the games relate Snake's ideals with Hideo Kojima's. During Metal Gear Solid 2 Snake encourages Raiden to trust himself in making his own choices with the former representing the veteran developer and the latter the younger staff who are to decide whether a sequel to the series would be made without Kojima.^[51] In Metal Gear Solid 4, Snake tries to protect the next generation by stopping Ocelot which was representing by Kojima working with the staff to avoid bugs from occurying within the game.^[57] Kojima introduced the cloning origins of Solid Snake to Metal Gear Solid in order to provide Solid Snake with an adversary who would be his equal, since the story, being a continuation to the original MSX2 games, established Snake as an experienced soldier.^[58] Kojima explained that his decision to introduce a new playable character in Solid Snake's place for Sons of Liberty was done in order to develop Snake from another character's perspective, but also to avoid treating Snake as a rookie by having a new character be instructed via Codec instead.^[59]

By the time of Metal Gear Solid 4: Guns of the Patriots started development, Kojima told Shinkawa about his idea of making Snake look like an elder which surprised the designer. Once Shinkawa showed his artwork of Old Snake to the staff, they were all also surprised by the idea of playing as an old Solid Snake. However, as they were satisfied with end product as the staff started liking the character.^[57] In Guns of the Patriots one of Kojima's endings for the game would have had Snake and Otacon turn themselves in for breaking the law, and subsequently they would be convicted and executed.^[58] However, comments from Kojima's staff who were disappointed with his death resulted in the character's survival.^[60] According to Ryan Payton of Konami, Guns of the Patriots is the final canonical Metal Gear game to feature Solid Snake as the main character.^[61] Kojima himself stated that the series will continue but he does not want the character to be handled by anyone else.^[58]

In the games, Snake has been voiced by Akio Ōtsuka starting with Metal Gear Solid. Ōtsuka remembers being surprised during his debut as a result of the large amount dialogue Snake was given.^[62] In the English adaptations, Snake's role was made by David Hayter who found his work notable as he was originally a screenwriter and did not expect to become famous for dubbing a character.^[63] While Hayter comments having issues with some of Snake's lines in his first game, most notably a conversation regarding romance with Hal Emmerich, he stated he would talk about such things if he was asked again. By the time Metal Gear Solid 4 had its first trailers released, Hayter was frustrated by Snake's flinchs during his attempt of committing suicide based on the character's experience in the battlefield.^[64] For the crossover game Super Smash Bros, Hayter remembers having fun in voicing the character due to the comical lines Snake had to say.^[63]

Reception[link]

The character of Solid Snake has received positive response, ranking in various polls as one of the best video games characters in history. In an Oricon poll from 2008, he was voted as the fourth most popular video game character in Japan, tying with Nintendo's Pikachu.^[65] In a Famitsu poll done in February 2010, Snake was voted by readers as the most popular video game character.^[66] In the Guinness World Records Gamer's Edition from 2011, Snake was voted as the fourth most popular video game character.^[67] Also, Electronic Gaming Monthly listed him as number three as the Top Ten Video Game characters of all time.^[35]

Critics have often praised Snake's commitment to war as well as his appealing personality.^[35][68] Snake appeared in multiple GameFAQs "Character Battle" contests, and was runner-up in two, the "Character Battle V" in 2006,^[69] and the "Character Battle VII" in 2008.^[70] His character was amongst the last sixteen contestants on the greatest video game hero on GameSpot contest held in 2009, and lost out to Gordon Freeman on a tiebreaker.^[71] He was ranked seventeenth in UGO Networks's "Best Heroes in Entertainment."^[68] GameDaily listed him on their top 10 Smash Bros. characters list,^[72] while Play listed him as one of the characters they wanted to be playable in Mortal Kombat.^[73] Sites have also commented on his traits and appearance. 1UP listed him second in the "Top 5 Video Game Smokers" while GamesRadar placed him at the top of "The 10 manliest men in videogame history."^[74][75] Complex.com ranked him as fourth on the list of "Top 25 Pervs in Games".^[76] Solid Snake's endurance in the face of extreme punishment was even made the focus of a comedy article in the satirical newspaper, The Onion.^[77] The character customization in Soul Calibur 4 that allowed to create Snake was listed by UGO as one of the best ones from the series owing to his popularity within gamers.^[78] The character's Metal Gear Solid 2 design was at the bottom of the "8 Worst Game Character Makeovers" by GamePro, condemning his conversion in hairstyle in comparison to the one in Metal Gear Solid,^[79] and was also at the top of IGN's "Worst Videogame Haircuts".^[80] Before Metal Gear Solid 3: Snake Eater, Snake was thought to be the game's protagonist because of the physical resemblances between him and Naked Snake. However, later previews speculated how was it possible for Solid Snake to be in the game's settings, leading to the conclusion it was a young Big Boss.^[81][82][83] A comparison between Solid Snake's and Big Boss' characters was made by IGN's Phil Pirrello in articled called "Stars Thunderdome: Snake vs. Big Boss."^[84] David Hayter's performance as Snake's English voice actor has received praise to the point of being called one of the best ones in gaming as well as one of the character's most recognizable traits.^[85][86]

Snake's appearance in Metal Gear Solid 4 has received mixed opinions. Before it was released, various speculations were made regarding Snake's role. As he was the only who suffered from a drastic change in appearance, IGN commented that the most famous rumor was the one of Snake's body deteriorating across the game.^[87] Moreover, since it had been announced it would be his last appearance, IGN and GamesRadar wondered whether the character would die during the game and if Raiden would replace him following his death.^[88][89] GamesRadar commented that Snake was one of the few gaming characters that aged across video games.^[90] GamePro also listed Old Snake as one of the biggest surprises from Metal Gear Solid 4 as the character was found interesting in contrast to pessimistic thoughts they had before the game's release.^[91] GameDaily listed the "old hero" as one of their top 25 video game archetypes, using the old version of Snake as an example of this.^[92] Play gave praise to his moustache considering how highly detailed it is, and represents the change from Snake's character.^[93] On the other hand, 1UP placed him third in the article of "Top 5 Gracelessly Aging Characters" as it gave negative messages about aging.^[94]

References[link]