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RegelationRegelation is the phenomenon of melting under pressure and freezing again when the pressure is reduced. Many textbooks and websites claim that regelation can be demonstrated by looping a fine wire around a block of ice and attaching a heavy weight to it. The pressure exerted on the ice slowly melts it locally, permitting the wire to pass through the entire block. The wire's track will refill as soon as pressure is relieved, so the ice block will remain solid even after wire passes completely through. This experiment is possible for ice at –10 °C or cooler. It has also been suggested that the heating of the wire under pressure and tension may also play a role.[1] Additional recommended knowledgeIf 1 mm diameter wire is used, over an icecube 50 mm wide, the area the force is exerted on is 50 mm2. This is 50 x 10-6 m2. Regelation was discovered by Michael Faraday. Regelation occurs only for substances, such as ice, that have the property of expanding upon freezing, for the melting points of those substances decrease with increasing external pressure. The melting point of ice falls by 0.0072 °C for each additional atm of pressure applied. For example, a pressure of 500 atmospheres is needed for ice to melt at –4 °C. [2]
Examples of Regelation
Notes
Categories: Heat | Thermodynamics |
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Regelation". A list of authors is available in Wikipedia. |