Solid-Liquid Equilibrium
In this section, we explore the solid-liquid equilibrium using the example of ice and water in a perfectly insulated thermos flask at 273K and atmospheric pressure. At this temperature, the ice and water are in a stable equilibrium state where their masses remain constant over time. This equilibrium, however, is dynamic; it includes continuous molecular activity at the boundary where ice meets water. In this state, water molecules collide with the ice, causing some to adhere to its surface, while molecules from the ice transition into the liquid phase.
Key Features of the Equilibrium:
- Constant Mass: The total mass of ice and water does not change because the rates at which water melts into ice and ice melts into water are equal.
- Dynamic Nature: Despite the constancy in mass, there is a significant transfer of molecules between the phases.
- Specific Conditions: The equilibrium occurs at specific temperatures and pressures, explicitly detailing that at normal atmospheric pressure, the temperature where the solid and liquid phases coexist is termed the normal melting point or freezing point.
- Simultaneous Processes: The dynamic equilibrium can be understood as two opposing processes occurring concurrently at equal rates, which keeps the quantities of ice and water stable.