Passage
A cup of hot tea left on a table slowly cools until it is as warm as the room. Two students agreed that the drink cools and eventually reaches room temperature, but they disagreed about the main way it loses its heat.
Student 1: The drink cools mainly because heat spreads from it into its cooler surroundings. Being hotter than the room, the tea passes heat to the air around it and to the cup and table it touches, until everything reaches the same temperature. On this view, the tea cools fastest at first, when it is much hotter than the room, and more slowly as it nears room temperature; wrapping the cup in an insulating sleeve, which slows this spreading, should make it cool more slowly, and a lid over only the top would still let heat escape through the sides.
Student 2: The drink cools mainly because water evaporates from its surface, and evaporation carries heat away with the escaping vapor. On this view, a tight lid that stops evaporation should nearly halt the cooling; blowing across the surface, or using a wider cup with more exposed surface, should speed the cooling; and a nearly full cup with only a small opening should cool much more slowly.
