The ice in the freezer evaporates through a process known as sublimation. Sublimation is the phase transition in which a substance changes directly from a solid state to a gaseous state without passing through the liquid phase. This process occurs when the surrounding conditions are right, particularly when there is low humidity and sufficient energy (heat) to facilitate the transformation.
When the freezer is operating, it continuously removes heat from the interior, causing the temperature to drop below the freezing point of water. As a result, any ice or frost inside the freezer will start to sublimate into water vapor (gas) rather than melting into liquid water. The water vapor is then removed from the freezer through the venting system or defrost mechanisms, and it dissipates into the surrounding environment.
Sublimation is why ice cubes "shrink" over time in the freezer without leaving a pool of water like melting ice would. The ice slowly transforms into water vapor, and this process is accelerated when the freezer goes through its defrost cycles. The defrost cycle typically raises the temperature inside the freezer momentarily, allowing any frost or ice to sublimate more quickly.
It's worth noting that modern freezers often have an automatic defrost feature that periodically heats up the freezer to remove excess ice buildup. This helps prevent excessive ice accumulation, maintains the efficiency of the appliance, and ensures proper airflow for optimal cooling. If a freezer does not have an automatic defrost feature, it may require manual defrosting to remove accumulated ice or frost buildup.