system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do thermos flask bottles advertise 24hrs cold and 12hrs hot. Shouldn't it be the same amount of time for temps in both directions?
gpt
The difference in temperature determines how fast heat transfers.

Ice water at 0 C is 25 degrees C from 25 C room temperature.

Hot water at 80-100 C is 55-75 degrees C from 25 C room temperature.

Hot water is more than double the temperature difference of cold water, so it changes temperature faster. Thus, the water inside will remain hot for a shorter time than cold water remains cold.