Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Conceptual Question 14.20
[10 points.] Which possesses more total internal energy, the water within a large, partially ice-covered lake in winter, or a 6-cup teapot filled with hot tea? Explain using the properties of heat and internal energy?
Solution and grading rubric:
- p = 10/10:
Correct. At absolute zero (0 kelvins), there is zero total internal energy. It will take much more heat to bring a frozen lake from absolute zero to partially frozen 273 K, than it would to bring a teapot of ice from absolute zero to near/at 373 K, as mass predominates over the delta(T) factors. - 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. - t = 6/10:
Nearly correct, but argument has conceptual errors, or is incomplete. Recognizes mass and delta(T) factors are relevant, but chooses delta(T) as the determinant factor. - v = 4/10:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. - x = 2/10:
Implementation/application of ideas, but credit given for effort rather than merit. - y = 1/10:
Irrelevant discussion/effectively blank. - z = 0/10:
Blank.
Grading distribution:
Sections 30880, 30881
p: 12 students
r: 12 students
t: 11 students
v: 3 students
x: 0 students
y: 0 students
z: 1 student
A sample of a "p" response (from student 0402):
Another sample of a "p" response (from student 1830), also taking into consideration the heat put in starting from absolute zero as the amount of internal energy present:
Another sample of a "p" response (from student 1985), using a heat exchange argument between these two systems:
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