Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 14.39
[Version 1]
[10 points.] An ice sample (0.0° C) is placed onto a 5.00 kg aluminum block at 1.0° C. As a result, the entire ice sample melts to 0.0° C water. As this system reached a thermal equilibrium of 0.0° C, was heat transferred from the ice sample to the aluminum block, or from the aluminum block to the ice sample, or were both transfers simultaneously taking place? Explain your answer using the properties of heat, temperature, and thermal equilibrium.
Solution and grading rubric:
- p = 10/10:
Correct. Heat transfers from warmer to cooler temperature objects. The aluminum temperature decreases, and thus is losing heat, while the ice melts (while its temperature remains constant), and thus is gaining heat. Discusses how each object loses or gains heat, such that the direction of the transfer is certain. - r = 8/10:
As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes. May confuse heat with internal energy (heat transfers due to a difference in energy rather than temperature). - t = 6/10:
Nearly correct, but argument has conceptual errors, or is incomplete. Has heat flowing from aluminum to ice, but claims that internal energy of ice is unchanged (or Q_ice = 0) as its temperature remains constant. - v = 4/10:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Has heat transferring from the ice to the aluminum, or has heat transferring from the aluminum causing the ice temperature to rise, or states that heat was transferred simultaneously from aluminum to ice and vice versa. At least has some discussion of temperature gradient, temperature/phase changes, and/or internal energy changes. - x = 2/10:
Implementation/application of ideas, but credit given for effort rather than merit. Statement of heat direction with little or substantive discussion. - y = 1/10:
Irrelevant discussion/effectively blank. - z = 0/10:
Blank.
Grading distribution:
Section 72177
p: 8 students
r: 0 students
t: 2 students
v: 1 student
x: 1 student
y: 1 student
z: 0 students
[Version 2]
[10 points.] An aluminum cylinder at room temperature (25.0° C) is dropped into a hole in a block of ice at 0.0° C. As this system reached a thermal equilibrium of 0.0° C, was heat transferred from the ice block to the aluminum cylinder, or from the aluminum cylinder to the ice block, or were both transfers simultaneously taking place? Explain your answer using the properties of heat, temperature, and thermal equilibrium.
Grading distribution:
Sections 70854, 70855
p: 28 students
r: 4 students
t: 8 students
v: 7 students
x: 1 student
y: 0 students
z: 0 students
A sample "p" response (from student 3334):
Another sample "p" response (from student 9626):
A sample "r" response (from student 0570):
A sample "t" response (from student 2468):
Another sample "t" response (from student 5256):
A sample "v" response (from student 1889):
Another sample "v" response (from student 4590):
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