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Temperature vs time plots, showing the Mpemba Effect. The Mpemba effect is the observation that a liquid (typically water) that is initially hot can freeze faster than the same liquid which begins cold, under otherwise similar conditions. There is disagreement about its theoretical basis and the parameters required to produce the effect. [1] [2]
In this scenario, the transition temperature is known as the calorimetric ideal glass transition temperature T 0c. In this view, the glass transition is not merely a kinetic effect, i.e. merely the result of fast cooling of a melt, but there is an underlying thermodynamic basis for glass formation. The glass transition temperature:
where m is the atomic mass, ν is the frequency, u is the average vibration amplitude, k B is the Boltzmann constant, and T is the absolute temperature. If the threshold value of u 2 is c 2 a 2 where c is the Lindemann constant and a is the atomic spacing, then the melting point is estimated as
Melting points and glass transition temperatures for most polymers are available from standard compilations, and the method can show polymer degradation by the lowering of the expected melting temperature. T m depends on the molecular weight of the polymer and thermal history. [citation needed]
Ice has a semi-liquid surface layer; When you mix salt onto that layer, it slowly lowers its melting point.. The more surface area salt can cover, the better the chances for melting ice.. Ice ...
An ice surface in fresh water melts solely by free convection with a rate that depends linearly on the water temperature, T ∞, when T ∞ is less than 3.98 °C, and superlinearly when T ∞ is equal to or greater than 3.98 °C, with the rate being proportional to (T ∞ − 3.98 °C) α, with α = 5 / 3 for T ∞ much greater than 8 ...
Just like glaciers have carved the land, leaving behind features like valleys and boulder fields, geologists have suspected that ice shelves along the ocean could do the same to the seafloor.
Values of the Biot number smaller than 0.1 imply that the heat conduction inside the body is much faster than the heat convection away from its surface, and temperature gradients are negligible inside of it. This can indicate the applicability (or inapplicability) of certain methods of solving transient heat transfer problems.