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Most liquids freeze by crystallization, formation of crystalline solid from the uniform liquid. This is a first-order thermodynamic phase transition, which means that as long as solid and liquid coexist, the temperature of the whole system remains very nearly equal to the melting point due to the slow removal of heat when in contact with air, which is a poor heat conductor.
It is also possible to freeze food by immersion in the warmer (at −70 °C (−94 °F)), but cheaper, liquid carbon dioxide, which can be produced by mechanical freezing (see below). [ 8 ] Most frozen food is instead frozen using a mechanical process using the vapor-compression refrigeration technology similar to ordinary freezers .
Freeze-drying is among the methods used to preserve animals in the field of taxidermy. When animals are preserved in this manner they are called "freeze-dried taxidermy" or "freeze-dried mounts". Freeze-drying is commonly used to preserve crustaceans, fish, amphibians, reptiles, insects, and smaller mammals. [31]
Various dried foods in a dried foods store An electric food dehydrator with mango and papaya slices being dried. This is a list of dried foods.Food drying is a method of food preservation that works by removing water from the food, which inhibits the growth of bacteria and has been practiced worldwide since ancient times to preserve food.
Fractional freezing is a process used in process engineering and chemistry to separate substances with different melting points. It can be done by partial melting of a solid, for example in zone refining of silicon or metals, or by partial crystallization of a liquid, as in freeze distillation, also called normal freezing or progressive freezing.
In the above equation, T F is the normal freezing point of the pure solvent (273 K for water, for example); a liq is the activity of the solvent in the solution (water activity for aqueous solution); ΔH fus T F is the enthalpy change of fusion of the pure solvent at T F, which is 333.6 J/g for water at 273 K; ΔC fus p is the difference ...
Flash freezing techniques are used to freeze biological samples quickly so that large ice crystals cannot form and damage the sample. [5] This rapid freezing is done by submerging the sample in liquid nitrogen or a mixture of dry ice and ethanol. [6]
Photograph taken 21 March 2010 in Norwich, Vermont. Frost heaving (or a frost heave) is an upwards swelling of soil during freezing conditions caused by an increasing presence of ice as it grows towards the surface, upwards from the depth in the soil where freezing temperatures have penetrated into the soil (the freezing front or freezing boundary).