Physics quiz question: cool metal, warm water heat exchange

Physics 205A Quiz 7, fall semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Example 14.5

A 25 g iron sample at room temperature (25° C) is placed in 200 g of water at 80° C to reach thermal equilibrium. The specific heat of iron is 0.44 kJ/(kg·K). The specific heat of water is 4.19 kJ/(kg·K). The __________ had the greatest change in internal energy once thermal equilibrium is reached.
(A) 25 g iron sample.
(B) 200 g of water.
(C) (There is a tie.)
(D) (Not enough information is given.)

Correct answer (highlight to unhide): (C)

As the two components of this system reach thermal equilibrium, the amount of heat given up by the 200 g of water is exactly equal to the amount of heat taken in by the 25 g iron sample.

Student responses
Section 70854, 70855
(A) : 16 students
(B) : 16 students
(C) : 15 students
(D) : 0 students

Success level: 31%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.42