For freezing as a method of food preservation, see frozen food. Frozen food is food preserved by the process of Freezing. Freezing food is a common method of Food preservation which slows both food decay and by For a TV series of the same name, see Freezing (TV series). Freezing is a BBC comedy series starring Hugh Bonneville and Elizabeth McGovern about an otherwise successful couple in their forties who find themselves For freezing in terms of computers, see hang (computing)

In physics and chemistry, freezing is the process whereby a liquid turns to a solid when cold enough. This article is about the computer malfunction called hanging. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties Liquid is one of the principal States of matter. A liquid is a Fluid that has the particles loose and can freely form a distinct surface at the boundaries of A solid' object is in the States of matter characterized by resistance to Deformation and changes of Volume. The freezing point is the temperature at which this happens. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Melting, the process of turning a solid to a liquid, is almost the exact opposite of freezing. Melting is a process that results in the phase change of a substance from a Solid to a Liquid. All known liquids undergo freezing when the temperature is lowered with the sole exception of helium, which remains fluid at absolute zero and can only be solidified under pressure. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Superfluidity is a phase of matter or description of Heat capacity in which unusual effects are observed when Liquids, typically of Helium-4 Absolute zero is the point at which molecules do not move (relative to the rest of the body more than they are required to by a quantum mechanical effect called Zero-point For most substances, the melting and freezing points are the same temperature, however, certain substances possess differing solid-liquid transition temperatures. For example, agar melts at 85 °C (185 °F) and solidifies from 31 °C to 40 °C (89. Agar or agar agar is a Gelatinous substance derived from Seaweed. 6 °F to 104 °F); this process is known as thermal hysteresis. Antifreeze proteins (AFPs or ice structuring proteins (ISPs refer to a class of Polypeptides produced by certain vertebrates plants fungi and bacteria that permit

Contents 1 Crystallization 2 Supercooling 3 Vitrification 4 Freezing of biological fluids 5 Food preservation 6 References 7 See also

Crystallization

Main article: Crystallization

Most liquids freeze by crystallization, formation of crystalline solid from the uniform liquid. Crystallization is the (natural or artificial process of formation of solid Crystals precipitating from a homogeneous --> identical Solution Crystallization is the (natural or artificial process of formation of solid Crystals precipitating from a homogeneous --> identical Solution In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating This is a first-order thermodynamic phase transition, which means that as long as solid and liquid coexist, the equilibrium temperature of the system remains constant and equal to the melting point. In Thermodynamics, phase transition or phase change is the transformation of a thermodynamic system from one phase to another The melting point of a solid is the temperature range at which it changes state from solid to Liquid. Crystallization consists of two major events, nucleation and crystal growth. Nucleation is the onset of a Phase transition in a small region Crystal growth is a major stage of a crystallization process, after the Nucleation stage Nucleation is the step where the molecules start to gather into clusters, on the nanometer scale, arranging in a defined and periodic manner that defines the crystal structure. A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a Periodicity is the quality of occurring at regular intervals or periods (in Time or Space) and can occur in different contexts A Clock marks In Mineralogy and Crystallography, a crystal structure is a unique arrangement of Atoms in a Crystal. The crystal growth is the subsequent growth of the nuclei that succeed in achieving the critical cluster size.

Supercooling

Main article: Supercooling

In spite of the second law of thermodynamics, crystallization of pure liquids usually begins at lower temperature than the melting point, due to high activation energy of homogeneous nucleation. The second law of Thermodynamics is an expression of the universal law of increasing Entropy, stating that the entropy of an Isolated system which The melting point of a solid is the temperature range at which it changes state from solid to Liquid. In Chemistry, activation energy, also called midnight energy, is a term introduced in 1889 by the Swedish scientist Svante Arrhenius, that is defined Nucleation is the onset of a Phase transition in a small region The creation of a nucleus implies the formation of an interface at the boundaries of the new phase. Some energy is expended to form this interface, based on the surface energy of each phase. Surface energy quantifies the disruption of intermolecular bonds that occurs when a surface is created If a hypothetical nucleus is too small, the energy that would be released by forming its volume is not enough to create its surface, and nucleation does not proceed. Freezing does not start until the temperature is low enough to provide enough energy to form stable nuclei. In presence of irregularities on the surface of the containing vessel, solid or gaseous impurities, pre-formed solid crystals, or other nucleators, heterogeneous nucleation may occur, where some energy is released by the partial destruction of the previous interface, rising the supercooling point to be near or equal to the melting point. Nucleation is the onset of a Phase transition in a small region The melting point of water at 1 atmosphere of pressure is very close to 0 °C (32 °F, 273. Water is a common Chemical substance that is essential for the survival of all known forms of Life. 15 K), and in the presence of nucleating substances the freezing point of water is close to the melting point, but in the absence of nucleators water can super cool to −42 °C (−43. Nucleation is the onset of a Phase transition in a small region 6 °F, 231 K) before freezing. Under high pressure (2,000 atmospheres) water will super cool to as low as −70°C (−94°F, 203 K) before freezing^[1]. The Standard atmosphere is an international reference pressure defined as 101325 Pa and formerly used as unit of Pressure (symbol atm

Vitrification

Main article: Vitrification

Certain materials, such as glass or glycerol, may harden without crystallizing; these are called amorphous solids. Vitrification is a process of converting a material into a Glass -like Amorphous solid that is free from any Crystalline structure either by the quick removal Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many An amorphous solid is a Solid in which there is no Long-range order of the positions of the Atoms (Solids in which there is long-range atomic order are Amorphous materials as well as some polymers do not have a true freezing point as there is no abrupt phase change at any specific temperature. Instead, there is a gradual change in their viscoelastic properties over a range of temperatures. Viscoelasticity is the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. Such materials are characterized by a glass transition temperature which may be roughly defined as the "knee" point of the material's density vs. The glass transition temperature, T g is the temperature at which an Amorphous solid, such as Glass or a Polymer, becomes brittle temperature graph.

Freezing of biological fluids

Main article: Cryoprotectant

Most living organisms accumulate cryoprotectants such as anti-nucleating proteins, polyols, and glucose to protect themselves against frost damage by sharp ice crystals. A cryoprotectant is a substance that is used to protect Biological tissue from Freezing damage (damage due to Ice formation A cryoprotectant is a substance that is used to protect Biological tissue from Freezing damage (damage due to Ice formation Antifreeze proteins (AFPs or ice structuring proteins (ISPs refer to a class of Polypeptides produced by certain vertebrates plants fungi and bacteria that permit Frost is the solid deposition of Water vapor from saturated air Most plants, in particular, can safely reach temperatures of −4°C to −12°C. Certain bacteria, notably Pseudomonas syringae, produce specialized proteins that serve as potent ice nucleators, which they use to force ice formation on the surface of various fruits and plants at about −2°C^[2]. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Pseudomonas syringae is a rod shaped Gram-negative Bacterium with polar Flagella. The freezing causes injuries in the epithelia and makes the nutrients in the underlying plant tissues available to the bacteria. ^[3]

Food preservation

Main article: Frozen food

Freezing is a common method of food preservation which slows both food decay and the growth of micro-organisms. Frozen food is food preserved by the process of Freezing. Freezing food is a common method of Food preservation which slows both food decay and by Food preservation is the process of treating and handling Food in a way that preserves its edibility and nutrition value A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually Besides the effect of lower temperatures on reaction rates, freezing makes water less available for bacterial growth. The reaction rate or rate of reaction for a Reactant or product in a particular reaction is intuitively defined as how fast a reaction takes The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have

References

See also

• Flash freezing
• Frost
• Melting point, for a more detailed description of the physical process. Flash freezing refers to the application of Supercooling in various kinds of industries whereby objects are quickly frozen by subjecting them to Cryogenic temperatures Frost is the solid deposition of Water vapor from saturated air The melting point of a solid is the temperature range at which it changes state from solid to Liquid.
• Mpemba effect
• Nucleation
• Phase diagram
• Phase transition
• Supercooling

From	To
	Solid	Liquid	Gas	Plasma
Solid	Solid-Solid Transformation	Melting	Sublimation	-
Liquid	Freezing	N/A	Boiling/Evaporation	-
Gas	Deposition	Condensation	N/A	Ionization
Plasma	-	-	Recombination/Deionization	N/A

The Mpemba effect is the observation that in certain specific circumstances warmer Water freezes faster than colder water Nucleation is the onset of a Phase transition in a small region In Physical chemistry, Mineralogy, and Materials science, a phase diagram is a type of graph used to show the equilibrium conditions In Thermodynamics, phase transition or phase change is the transformation of a thermodynamic system from one phase to another A solid' object is in the States of matter characterized by resistance to Deformation and changes of Volume. Liquid is one of the principal States of matter. A liquid is a Fluid that has the particles loose and can freely form a distinct surface at the boundaries of This page is about the physical properties of gas as a state of matter In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound Melting is a process that results in the phase change of a substance from a Solid to a Liquid. Sublimation of an element or compound is a transition from the Solid to Gas phase with no intermediate liquid stage Boiling (also called ebullition) a type of Phase transition, is the rapid vaporization of a Liquid, which typically occurs when a liquid Evaporation is the process by which Molecules in a Liquid state (e Deposition is a process in which gas transforms into solid (also known as desublimation Condensation is the change of the physical state of aggregation (or simply state of matter from gaseous phase into liquid phase Ionization is the physical process of converting an Atom or Molecule into an Ion by adding or removing charged particles such as Electrons

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