freezing point

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Phase diagram of an "ordinary" substance and water

As freezing point , freezing point or fixed point those points are in a phase diagram referred to on the border between the states of aggregation "solid" and are "liquid". The best known freezing point is that of water . It forms or defines the zero point on the temperature scale, which is divided into degrees Celsius . If someone speaks of “freezing point” without further details, he usually means that of the purest water, i.e. 0 ° C.

The freezing point represents the conditions that exist during the phase transition of a substance from the liquid to the solid phase, which is known as freezing. The freezing point depends on the substance and is indicated by a freezing temperature at a certain pressure .

Freezing points are always given for pure substances . If other substances are dissolved in the liquid, this will lower the freezing point . A freezing point measurement can therefore be used to determine the purity of the substance.

It is possible to cool a liquid to a temperature a little below freezing without it solidifying. Such a supercooled liquid then suddenly solidifies with the slightest disturbance with just as spontaneous heating to the freezing point.

Freezing point of aviation fuels

For the evaluation of aviation fuel freezing point (dt. Translation of Freezing Point noted), but which is the melting point is different in the physical sense. The freezing point indicates the temperature at which paraffin, which was previously flocculated under defined conditions, just dissolves again.

See also

Individual evidence

  1. ISO 3013: 1997-09, Mineral oil products - Determination of the freezing point of aviation fuels.