When a substance freezes, what happens to the thermal energy?

When a substance freezes, it undergoes a phase change from a liquid to a solid. During this process, the molecules within the substance lose kinetic energy, which results in a decrease in thermal energy. This lost thermal energy is released into the surrounding environment.

As the liquid cools and transitions to a solid state, the molecules slow down and move closer together, forming a more ordered structure. The release of thermal energy is what allows this structural rearrangement to occur. This phenomenon is crucial in understanding how substances interact with their environment during phase changes, and it illustrates the principle that energy must be conserved during such transformations.

The other options do not accurately describe the behavior of thermal energy during freezing. For instance, thermal energy does not remain constant; it decreases and is thus released. Moreover, it does not increase during freezing, as that would suggest that the substance is gaining energy rather than losing it. Lastly, the idea that thermal energy is absorbed contradicts the fundamental concept of heat release during the freezing process.