Question

Multiple-Choice Questions
A box labeled Top Pan contains 9 low energy molecules, each marked 30. Below is another box labeled Bottom Pan containing 9 high energy molecules, each marked 70.
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2. Claude is in the kitchen cooking and is going to stack one pan on top of another pan. The two pans are the same size and have the same number of molecules. The diagram above shows the pans now, before they touch each other. Use the information in the diagram to answer the question.

How does the temperature of the top pan compare with the temperature of the bottom pan now, and what will happen after the pans have been touching for a while?

Responses

a
Before the pans touch, the bottom pan is hotter than the top pan. Once the pans are touching, the bottom pan will transfer kinetic energy to the molecules in the cooler top pan until both pans reach the same temperature, which will be in between their starting temperatures.
Before the pans touch, the bottom pan is hotter than the top pan. Once the pans are touching, the bottom pan will transfer kinetic energy to the molecules in the cooler top pan until both pans reach the same temperature, which will be in between their starting temperatures.

b
Before the pans touch, the bottom pan is hotter than the top pan. Once the pans are touching, the cooler top pan will gain kinetic energy until the molecules in both pans have an energy of 70, because hotter things increase the temperature of cooler things.
Before the pans touch, the bottom pan is hotter than the top pan. Once the pans are touching, the cooler top pan will gain kinetic energy until the molecules in both pans have an energy of 70, because hotter things increase the temperature of cooler things.

c
Before the pans touch, the bottom pan is cooler than the top pan. Once the pans are touching, the top pan will transfer kinetic energy to the molecules in the cooler bottom pan until both pans reach the same temperature, which will be in between their starting temperatures.
Before the pans touch, the bottom pan is cooler than the top pan. Once the pans are touching, the top pan will transfer kinetic energy to the molecules in the cooler bottom pan until both pans reach the same temperature, which will be in between their starting temperatures.

d
Before the pans touch, the two pans are different temperatures. Once the pans are touching, both kinetic energy and cold energy will transfer between the molecules in the two pans until both pans reach the same temperature, which will be in between their starting temperatures.
Before the pans touch, the two pans are different temperatures. Once the pans are touching, both kinetic energy and cold energy will transfer between the molecules in the two pans until both pans reach the same temperature, which will be in between their starting temperatures.

Answer 1

Answer: a

Reason: The bottom pan (molecules = 70) is hotter than the top pan (molecules = 30). When they touch, heat (kinetic energy) flows from the hotter pan to the cooler one until thermal equilibrium is reached. Because the pans have the same size and same number of molecules, the final average molecular energy will be the average (30+70)/2 = 50, i.e., a temperature between the starting temperatures.