Why does an ice cube melt in the mouth

The temperature of the mouth is about 37 °C, so an overly simple explanation of why ice melts in the mouth is to say that the mouth is warmer than the transition temperature T(mM). And, being warmer, the mouth supplies energy to the immobilized water molecules, thereby allowing them to break free from those bonds that hold them rigid. In this process, solid H20 turns to liquid H20 - the ice melts. 

Incidentally, this argument also explains why the mouth feels cold after the ice has melted, since the energy necessary to melt the ice comes entirely from the mouth. In consequence, the mouth has less energy after the melting than before this statement is wholly in accord with the zeroth law of thermodynamics, since heat energy travels from the hot mouth to the cold ice. Furthermore, if the mouth is considered as an adiabatic chamber (see p. 89), then the only way for the energy to be found for melting is for the temperature of the mouth to fall. 

In the thermodynamic sense, a phase is defined as part of a chemical system in which all the material has the same composition and state. Appropriately, the word comes from the Greek phasis, meaning appearance . Ice, water and steam are the three simple phases of H20. Indeed, for almost all matter, the three simple phases are solid, liquid and gas, although we must note that there may be many different solid phases possible since H20(S) can adopt several different crystallographic forms. As a related example, the two stable phases of solid sulphur are its monoclinic and orthorhombic crystal forms. 

Ice is a solid form of water, and is its only stable form below 0 °C. The liquid form of H20 is the only stable form in the temperature range 0 T 100 °C. Above 100 °C, the normal, stable phase is gaseous water, steam . Water s normal melting temperature 7(meit) is 0°C (273.15 K). The word normal in this context implies at standard pressure p . The pressure has a value of 105 Pa. This temperature T tneiu is often called the melting point because water and ice coexist indefinitely at this temperature and pressure, but at no other temperature can they coexist. We say they reside together at equilibrium. 

Two or more phases can coexist indefinitely provided that we maintain certain conditions of temperature T and pressure p. The normal boiling temperature of water is 100 °C, because this is the only temperature (at p = p°) at which both liquid and 

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