Question

1. aki is playing cards and is about to put one card on top of another. both cards are the same size and have the same number of molecules. the diagram above shows the cards now, before they touch each other. use the information in the diagram to answer the question.

how does the temperature of the top card compare with the temperature of the bottom card before the cards touch, and what will happen after the cards have been touching for a while?
a before the cards touch, the top card is cooler than the bottom card. once the cards are touching, the bottom card will transfer kinetic energy to the molec in the cooler top card until both cards reach the same temperature, which will be in between their sta ing temperatures.
b before the cards touch, the top card is hotter than the bottom card. once the cards are touching, the cooler bottom card will gain kinetic energy until both cards’ molecules have an energy of 28, because hotter things increase the temperature of cooler things.
c before the cards touch, the top card is hotter than the bottom card. once the cards are touching, the top card will transfer kinetic energy to the molecules in the cooler bottom card until both cards reach the same temperature, which will be in between their starting temperatures.
d before the cards touch, the two cards are different temperatures. once the cards are touching, both kinetic energy and cold energy will transfer between the molecules in the two cards until both cards reach the same temperature, which will be in between their starting temperatures.

Explanation:

First, we use the principle of thermal energy transfer: temperature is related to molecular kinetic energy, and energy transfers from higher kinetic energy (hotter) objects to lower kinetic energy (cooler) ones until thermal equilibrium (same temperature, between initial values) is reached.

• Option a incorrectly states the top card is cooler.
• Option b is wrong because molecules won't all reach an energy of 28, and the temperature equalizes to a value between initials, not a fixed energy.
• Option d is incorrect because there is no "cold energy"; only thermal (kinetic) energy transfers from hotter to cooler.
• Option c correctly identifies the top card as hotter first, and describes energy transfer to the cooler bottom card until both reach the same temperature between their starting values.

Answer:

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