Freezing Point Depression Flashcards
What is freezing point depression?
Freezing point depression is the decrease in the temperature at which a liquid turns into a solid when a solute is added.
How does the presence of a solute affect the chemical potential in a solution?
The presence of a solute reduces the chemical potential, lowering the solidification (crystallization) temperature.
What phenomenon allows water to cool below 0 °C without freezing when sodium chloride is added?
The freezing point depression caused by the dissolved sodium chloride.
Describe the process that occurs as a soluble sugar solution cools to thermodynamic equilibrium.
As the solution cools, water crystallizes into ice, increasing the concentration of sugar in the unfrozen solution until it exceeds saturation.
What happens to the viscosity of the unfrozen solution as cooling continues beyond the freezing point?
The viscosity of the unfrozen phase increases significantly, impeding molecular motion and leading to the formation of a glassy state.
Why is freezing point depression important in the context of ice cream production?
It prevents the formation of large ice crystals, resulting in a smoother texture and better quality in frozen desserts.
What occurs at T4 in the cooling of a sugar solution?
At T4, crystallization stops, and the viscosity increases, forming a glassy state without further crystallization.
Explain the relationship between cooling and crystallization in a sugar solution.
As the solution cools, the crystallization of water into ice depletes available water for dissolving sugar, which raises the sugar concentration in the remaining unfrozen solution.
what is T1
Initial temperature of the solution before any cooling begins.
T2?
The temperature at which the solution reaches thermodynamic equilibrium and begins to cool, where water starts crystallizing into ice.
T3?
The temperature at which the solution continues to cool as ice forms. The sugar concentration in the unfrozen solution increases due to the crystallization of water, but crystallization may slow or stop as viscosity increases.
T4?
The temperature where crystallization stops completely, and the unfrozen phase becomes highly viscous, potentially forming a glassy state. At this point, further cooling does not lead to additional crystallization.
