Question

Cup A and cup B are identical. They contain equal volumes of soup at equal temperatures. Both cups are put in a refrigerator. Cup A has a lid, but cup B does not. Which statement best explains why cup A will cool more slowly than cup B?

A. Water vapor won’t be able to escape from cup A.
B. The most energetic water molecules from cup A will escape more rapidly.
C. No molecules will be able to evaporate at the surface of cup B.
D. No molecules will be able to evaporate at the surface of cup A.

Answer 1

The correct answer is:

• A. Water vapor won’t be able to escape from cup A.

The presence of a lid on cup A prevents water vapor (evaporation) from escaping. Evaporation is a cooling process, and if water vapor can't escape, the cooling rate is slowed down. In contrast, cup B without a lid allows water molecules to evaporate from the surface, leading to a faster cooling process.