Physics clicker question: temperature and temperature changes

Physics 5A, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Problems 13.2, 13.4, Conceptual Question 13.3

Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the start of their learning cycle:

[0.6 participation points.] Which one of the following temperatures is the warmest?
(A) 10° C.
(B) 10 K.
(C) 10° F.
(D) (I'm lost, and don't know how to answer this.)

Sections 4987, 4988
(A) : 5 students
(B) : 14 students
(C) : 0 students
(D) : 0 students

Correct answer: (A)

The coldest temperature is (B), which is most nearest to absolute zero (perhaps demonstrating the students' unfamiliarity with the Kelvin scale). Between (A) and (C), 10° F is below freezing (32° F), while 10° C is above freezing (0° C), so response (A) is the warmest temperature.

[Follow-up question]

[0.6 participation points.] Which one of the following temperature changes represents the largest amount of cooling?
(A) –10° C.
(B) –10 K.
(C) (Both changes in temperature corresponds to the same amount of cooling.)
(D) (Both the initial and final temperatures need to be given.)
(E) (I'm lost, and don't know how to answer this.)

Sections 4987, 4988
(A) : 10 students
(B) : 10 students
(C) : 2 students
(D) : 1 student
(E) : 0 students

Correct answer: (C)

Apparently these students are not at all familiar with temperature scales and changes in temperatures (preoccupied on an impending semi-comprehensive midterm on chapters previous to this introduction to thermodynamics?). It is pointed out to them after these clicker questions that T (°C) ≠ T (K), but they are related by an "offset":

T (°C) = T (K) - 273.15.

However, even though these temperatures are not equivalent, changes in these temperatures are, such that:

delta_T (°C) = delta_T (K).

Students are warned that this property of temperature changes will come in handy throughout thermodynamics (expansion, heat, etc. calculations).