Teaching Physical Chemistry Without Lectures or the Power of Cooperative Learning in Chemistry Julanna V. Gilbert Department of Chemistry & Biochemistry

Physical Chemistry Junior/senior level course for chemistry/biochemistry majors Requirements: 1yr calculus, 1 yr physics, general chemistry & equilibrium systems. Introduction to Physical Chemistry –Thermodynamics –Applications Physical Chemistry II –Kinetics –Quantum Mechanics Physical Chemistry III –Spectroscopy –Photochemistry –Statistical Mechanics

Why not just lecture? Student perspective 6Material tends to be presented too quickly. 6Limited access to other students & the instructor outside class time. 6Class time may not provide opportunity for students to discuss what they need to discuss (which varies by student). 6Little time for individualized help during class. 6Students need to learn how to learn on their own

Why not just lecture? Instructor perspective DMost students don’t or can’t answer questions during class. DMay not find what students are really learning until an exam. DIndividualized help difficult, tend to “lecture at everyone”. DHard to know when misconceptions exist, don’t hear from most of the students. DStudents need to learn how to learn on their own

Class Format FMeets for two 2-hr sessions per week FClass divided into groups FEach group completes a “worksheet” during class FWorksheets lead students through the material Student Groups FAs much diversity as possible – set by instructor & explained to students FThree students per group (optimum size) FRotate the “scribe” duty.

Grading Group work (worksheets) – 40% of total grade Individual work (homework + exams) – 50% of grade Peer review – 10% of grade

Typical Session PStudents are eager to start working on the worksheets (really!). PStudents refer to their textbooks, talk to each other, ask the instructor questions. PRoom gets noisy, groups interact with each other, instructor circulates to monitor progress and answers questions. PSometimes class is stopped to clear up common misconceptions that arise. Class time is defined by the students’ needs first, not by the need to cover a given amount of material.

Tools 0Textbook 0Excel, MathCad 0Course web site 0Syllabus, Worksheets, Review sheets 0Discussion forums 0Internet resources 0The students’ minds

Examples of materials created for Thermodynamics

Physical Chemistry I, Fall 2003 INTRODUCTION Tues Sept 9Worksheet 1: Calculus review, Introduction to exact and inexact differentials (Further information 1.5 & 1.7) Thurs Sept 11Worksheet 2: Real and ideal gases (Chapter 1) THERMODYNAMICS - THE FIRST LAW Tues Sept 15Worksheet 3: Work, heat and the first law of thermodynamics (Chapter ) Thurs Sept 18Worksheet 4: Enthalpy & heat capacities, the equipartition of energy theorem (Chapter 2.5 – 2.6, handout) Tues Sept 23Worksheet 5: Understanding thermochemistry & enthalpies and fun with thermodynamic relationships (Chapter , Chapter 3) Thurs Sept 25 Discussion and review Tues Sept 31 Exam # 1

Physical Chemistry I, Fall 2003 THERMODYNAMICS - THE SECOND LAW Thurs Oct 2Worksheet 6: Spontaneous direction of processes, Carnot cycles, entropy, & the second law of thermodynamics (Chapter 4.1 & 4.2) Tues Oct 7 Worksheet 7:  S for processes involving gases, phase transitions, and chemical reactions, entropy & probability, the third law of thermodynamics (Chapter 4.3 & 4.4) Thurs Oct 9 Worksheet 8: Predicting spontaneous processes: Gibbs & Helmholtz energies - (Chapter 4.5 & 4.6, Thermodynamics in a Nutshell) Tues Oct 14Worksheet 9: Properties of the Gibbs energy and more fun with thermodynamic relationships (Chapter 5 & Thermodynamics in a Nutshell) APPLICATIONS OF THERMODYNAMICS Thurs Oct 16Worksheet 10: Phase diagrams for pure substances (Chapter ) Tues Oct 21Worksheet 11: Thermodynamic description of mixtures (Chapter ) Thurs Oct 23 Discussion and review Tues Oct 28 Exam #2

Finding expressions for PV work. All of the PV expressions for work in one table. Makes it easy for students to grasp how to know when to use what expression for calculating work. Allow students to concentrate on the system and meaning.

E. Finding expressions for PV work. Fill in the table below - show your work. (The entries in the1st column will be identical – likewise for the entries in the 2 nd column.) PROCESS DifferentialIntegralP ext Evaluate integral Free expansion dw = -P ext dV -  P ext dV P ext = 0 w =-  P ext dV w = -P ext  dV w =0 since P ext = 0 Expansion against a constant external pressure, any gas Reversible isothermal expansion, ideal gas Reversible isothermal expansion, VDW gas A change at constant volume any gas Adiabatic expansion, ideal gas dw = -P ext dV -  P ext dV P ext = P int = nR T/ V STOP! T is not constant! We must find a new relationship between T and V to evaluate the integral:  (nRT/V) dV. We will find this relationship in a later worksheet.

The Nutshell Sheet A one-page organizational scheme for equilibrium thermodynamics. Demystifies the math for students so they can concentrate on the content

Equilibrium Thermodynamics in a Nutshell EnergyEnthalpyGibbs EnergyHelmholtz Energy 1. Write the state function definition dU =H =G =A = 2. Write the differential form of the state function 3. Write the differential form assuming a reversible process (dq rev =TdS), and PdV work only 4. Write the exact differential with the “natural variables” (from 3) 5. Write the new relationships (from 3 & 4) 6. Apply Euler's criterion for exact differentials to the expression in 4 above 7. Write the new relationships from 5 & 6 (called Maxwell's Relations) 8. Determine the condition for equilibrium

EQUILIBRIUM THERMODYNAMICS IN A NUTSHELL Energy EnthalpyGibbs EnergyHelmholtz Energy 1. Write the state function definition dU = dq + dw H = U + PV G = H - TS A = U - TS 2. Write the differential form of the state function dU = dq + dwdH = dU + PdV +VdPdG = dH – TdS – SdT dA = dU – TdS – SdT 3. Write the differential form assuming a reversible process (dq rev =TdS), and PdV work only dU = TdS – PdVdH =TdS – PdV +PdV + VdP dH = TdS + VdP dG = dU+PdV+VdP – TdS – SdT dG = TdS –PdV +PdV + VdP – TdS – SdT dG = VdP – SdT dA = TdS – PdV – TdS – SdT dA = -PdV-SdT 4. Write the exact differential with the “natural variables” (from 3) dU = (  U/  S) V dS + (  U/  V) S dV dH = (  H/  S) P dS + (  H/  P) S dP dG = (  G/  P) T dP + (  G/  T) P dT dA = (  A/  V) T dV + (  A/  T) V dT 5. Write the new relationships (from 3 & 4) T = (  U/  S) V –-P = (  U/  V) S T = (  H/  S) P V = (  H/  P) S V = (  G/  P) T –S = (  G/  T) P –P = (  A/  V) T –S = (  A/  T) V 6. Apply Euler's criterion for exact differentials to the expression in 4 above (  U 2 /  S  V)= (  U 2 /  V  S) (  H 2 /  S  P)= (  H 2 /  P  S) (  G 2 /  P  T)= (  G 2 /  T  P) (  A 2 /  V  T)= (  A 2 /  T  V) 7. Write the new relationships from 5 & 6 (called Maxwell's Relations) (  T/  V)s = – (  P/  S) V (  T/  P) S = (  V/  S) P (  V/  T) P = – (  S/  P) T (  P/  T) V =(  S/  V) T 8. Determine the condition for equilibrium dU=0 at constant V and S dH=0 at constant P and S dG=0 at constant P and T dA=0 at constant V and T

The third “law” of thermodynamics Hard for students to grasp. Work the exercise in class so there is lots of interaction between instructor and students. Students get it!!

Find S for lead at various T’s using Excel Visualization of: –C P,T experimental data –The 3rd Law of Thermodynamics (lim T  0 S  0) –dS = (C P /T)dT,  S =  (C P /T)dT and  S = S T -S 0 –  S is the area under the curve of C P /T vs. T.

Physical Chemistry II Mathcad exercises 8Particle in a 2-dimensional box 8Plots of wavefunctions 8Solving rate equations

General impressions of teaching without lectures 5Find out what students are really learning 5Get students to talk in class about chemistry 5Intervene frequently to minimize misconceptions 5Provide more individualized help

Does it work???

Lots of qualitative feedback from students suggests “yes”. – Students answer questions in class, are able to think “on their feet” – Students gain self-confidence, are willing to ask questions in class – Students come up with creative problem solving methods – Students are fully engaged with the course material.

Comparison of exam averages from lecture-based and group-based methods in Physical Chemistry I

Comparison of Exam Averages Physical Chemistry III

What the instructor experiences  Instructor gets all kinds of questions from students.  Additional grading.  More interaction with students.  Students get used to participating.  Students who miss a lot of sessions get left behind in many ways.

What do the students say?

Students’ Comments  (first 2 years) Need lectures & shorter worksheets  Course seemed too easy – Gilbert thinks everyone can learn thermodynamics but that’s just not true.  (last year & this year) I thought I would want lectures, but I prefer the groups. I learned more this way especially since the course is so difficult.  I leaned a lot, I tried hard.  I like the format & learned a lot even though it was tough.  Use of worksheets enables us to get a better grasp on what we are covering.

Conclusions  Requires the instructor to determine which course topics are truly essential and how to guide students through them.  Students discover that they and their peers can work together to gain understanding of even complicated concepts.  Students become active participants and take responsibility for learning the material  Students are definitely better able to demonstrate their learning with this format than with the lecture format