Final answer:
Dry ice sublimes in a freezer, turning from a solid to a gas. Its lifespan varies based on the freezer's insulation and the amount of dry ice, but it will eventually sublime fully over time.
Step-by-step explanation:
Dry ice, or solid carbon dioxide, sublimes rather than melts at atmospheric pressures, going directly from a solid to a gas at –78°C. When dry ice is placed in a freezer, its lifespan depends on the insulation of the freezer and the amount of dry ice used. Generally, dry ice will last longer in a well-insulated freezer, as it keeps the surroundings colder and allows for slower sublimation.
However, even in these conditions, it would eventually sublime fully due to the nature of solid carbon dioxide. Additionally, regular ice cubes made of H₂O also demonstrate sublimation by slowly shrinking in a freezer. This process redeposits on the colder elements of the freezer, resulting in a need for periodic defrosting, which is minimized by reducing the temperature in the freezer, especially frost-free models.