When a liquid transitions to a solid, this process is known as freezing or solidification. In terms of thermodynamic quantities, we analyze two important changes: the change in enthalpy (ΔH) and the change in entropy (ΔS).
The sign of ΔH for this phase change is negative (ΔH < 0). This is because the process releases heat into the surroundings. As the liquid loses energy in the form of heat, it solidifies, indicating that energy is being released.
On the other hand, the sign of ΔS is also negative (ΔS < 0). Entropy is a measure of disorder; in a liquid state, the molecules are more disordered and have more freedom to move compared to the organized structure of a solid. As the liquid transitions to a solid, the system becomes more ordered, resulting in a decrease in entropy.
In summary, for the phase change of liquid to solid, ΔH is negative, indicating heat release, and ΔS is negative, reflecting a decrease in disorder.