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1、Student Learning in Thermodynamics: Exploring the Chemistry/Physics Connection,David E. Meltzer Department of Physics and Astronomy Iowa State University Ames, IowaSupported in part by National Science Foundation grant DUE #9981140,酒店设计 http:/,Collaborator Thomas J. Greenbowe Department of Chemistry
2、 Iowa State University,Our Goal: Investigate learning difficulties in thermodynamics in both chemistry and physics courses,First focus on students initial exposure to thermodynamics (i.e., in chemistry courses), then follow up with their next exposure (in physics courses). Investigate learning of sa
3、me or similar topics in two different contexts (often using different forms of representation). Devise methods to directly address these learning difficulties. Test materials with students in both courses; use insights gained in one field to inform instruction in the other.,Outline,1. The physics/ch
4、emistry connection 2. First-semester chemistry: state functions heat, work, first law of thermodynamics 3. Second-semester physics: heat, work, first law of thermodynamics cyclic process 4. Second-semester chemistry: second law of thermodynamics Gibbs free energy,Initial Hurdle: Different approaches
5、 to thermodynamics in physics and chemistry,For physicists: Primary (?) unifying concept is transformation of internal energy U of a system through heat absorbed and work done; Second Law analysis focuses on entropy concept, and analysis of cyclical processes.For chemists: Primary (?) unifying conce
6、pt is enthalpy H H = U + PV(H = heat absorbed in constant-pressure process) Second law analysis focuses on free energy (e.g., Gibbs free energy G = H TS),Our Goal: Investigate learning difficulties in thermodynamics in both chemistry and physics courses,First focus on students initial exposure to th
7、ermodynamics (i.e., in chemistry courses), then follow up with their next exposure (in physics courses). Investigate learning of same or similar topics in two different contexts.,Initial Hurdle: Different approaches to thermodynamics in physics and chemistry,For physicists: Primary (?) unifying conc
8、ept is transformation of internal energy U of a system through heat absorbed and work done;For chemists: Primary (?) unifying concept is enthalpy H H = U + PV(H = heat absorbed in constant-pressure process),How might this affect physics instruction?,For many physics students, initial ideas about the
9、rmodynamics are formed during chemistry courses.In chemistry courses, a particular state function (enthalpy) comes to be identified - in students minds - with heat in general, which is not a state function.,Initial Objectives: Students understanding of “state functions” and First Law of Thermodynami
10、cs,Diagnostic Strategy: Examine two different processes leading from state “A” to state “B”:,Sample Populations Introductory courses for science majors,First-semester Chemistry Fall 1999: N = 426 Fall 2000: N = 532 Second-semester Physics Fall 1999: N = 186 Fall 2000: N = 188 Second-semester Chemist
11、ry Spring 2000: N = 47 Spring 2000, Interview subjects: N = 8,Results of Chemistry Diagnostic:,Is the net change in (a) temperature T; (b) internal energy E of the system during Process #1 greater than, less than, or equal to that for Process #2? (Answer: Equal to)Second version results in brackets
12、T during Process #1 is: greater than: .61% 48%less than:3% 3% T for Process #2.equal to:34% 47%E during Process #1 is: greater than: .51% 30%less than:2% 2% E for Process #2.equal to:43% 66% Students answering correctly that both T and E are equal: 20% 33%,Physics Diagnostic,Given in second semester
13、 of calculus-based introductory course. Traditional course; thermal physics comprised 18% of course coverage. Diagnostic administered in last week of course: Fall 1999: practice quiz during last recitation; N = 186 Fall 2000: practice quiz during final lecture; N = 188,Samples of Students Answers (A
14、ll considered correct),“U = Q W. For the same U, the system with more work done must have more Q input so process #1 is greater.”“Q is greater for process 1 since Q = U + W and W is greater for process 1.”“Q is greater for process one because it does more work, the energy to do this work comes from
15、the Qin.”“U = Q W, Q = U + W, if U is the same and W is greater then Q is greater for Process #1.”,Results, Fall 1999 N = 186,Results, Fall 2000 N = 188,Students Reasoning on Work Question Fall 2000: N = 188,Correct or partially correct . . . . . . . . . . . . 56% Incorrect or missing explanation .
16、. . . . . . 14% Work is independent of path . . . . . . . . . . 26% (majority explicitly assert path independence) Other responses . . . . . . . . . . . . . . . . . . . . 4%,Of the students who correctly answer that W1 W2 :,Fall 2000: 70% of total student sample 38% correctly state that Q1 Q2 41% state that Q1 = Q2 16% state that Q1 Q2,Of the students who assert that W1 = W2 :,
