During an experiment, ice and water were placed in a perfectly insulated thermos flask at 0 °C. Describe this system when it phase reaches equilibrium.

(See explanation for further details)

Explanation:

An insulated thermos indicates that there is no heat interactions between system and surroundings and there is a thermodynamic equilibrium between water and ice.

The mechanic equilibrium means that water and ice have the same pressure and thermal equilibrium means that water and ice have the same temperature. Given the existence of phase change, it means that phase with greater specific heat storage a major portion of heat. Water has a specific heat greater than in ice, which according to the First Law of Thermodynamics, there is less water than ice.