Freezing



For freezing as a method of food preservation, see frozen food.

In physics and agar melts at 85 °C (185 °F) and solidifies from 31 °C to 40 °C (89.6 °F to 104 °F); this process is known as thermal hysteresis.

Crystallization

Main article: Crystallization

Most liquids freeze by crystal structure. 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 supercool to −42 °C (−43.6 °F, 231 K) before freezing. Under high pressure (2,000 atmospheres) water will supercool to as low as −70°C (−94°F, 203 K) before freezing[1].

Vitrification

Main article: Vitrification

Certain materials, such as glass or glass transition temperature which may be roughly defined as the "knee" point of the material's density vs. temperature graph.

Freezing of biological fluids

Main article: Cryoprotectant

Most living organisms accumulate cryoprotectants such as frost damage by sharp ice crystals. 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 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 reaction rates, freezing makes water less available for bacterial growth.

References

  1. ^ Jeffery, CA & Austin, PH (November, 1997), " ", Journal of Geophysical Research 102 (D21): pages 25269-25280, doi:10.1029/97JD02243,
  2. ^ Maki LR, Galyan EL, Chang-Chien MM, Caldwell DR (1974). "Ice nucleation induced by pseudomonas syringae". APPLIED MICROBIOLOGY 28 (3): 456-459. PMID 4371331.
  3. ^ Zachariassen KE, Kristiansen E (2000). "Ice nucleation and antinucleation in nature". CRYOBIOLOGY 41 (4): 257-279. PMID 11222024.

See also

Look up freezing in Wiktionary, the free dictionary.
From To
Solid Liquid Gas Plasma
Solid Solid-Solid Transformation Melting Sublimation -
Liquid Freezing N/A Evaporation -
Gas Deposition Condensation N/A Ionization
Plasma - - Recombination/Deionization N/A
 
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