Rethinking Quant: The Importance

of Analytical Thinking

David HarveyPercy L. Julian Professor

Chemistry & BiochemistryDePauw University

Greencastle, INharvey@depauw.edu

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Papers/Symposia on Education in Analytical Chemistry in the Journal of Chemical Education

A Plea for Rationally Coordinated Courses in Analytical Chemistry (Brinton, 1924)

The Training of Analysts (Clarke, 1937)

Developments in the Teaching of Analytical Chemistry (Picketts, 1943)

Analytical Chemistry – How It Should be Taught (Bremner, 1951)

Education Trends in Analytical Chemistry (Symposium, 1960)

Present Status of the Teaching of Analytical Chemistry (Symposium, 1979)

We Analytical Chemistry Teachers Don’t Get No Respect (Hirsch, 1987)

Keeping a Balance in the First Analytical Course (Kratochvil, 1991)

Teaching Analytical Chemistry in the New Century (Symposium, 2001)

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What is the Role of the Quant Course?

Is it to… …develop a fundamental understanding of

equilibrium chemistry and laboratory skills in solution chemistry?

…study modern, instrumental analytical techniques and applications?

…learn to solve real problems and to work as part of a small research team?

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Other Factors Affecting the Design of the Quant Course

Institutional Resources available instrumentation computational technology operating budget

Student Profile academic strengths and weaknesses balance between majors and non-majors career goals

Departmental Curricular Needs Where is equilibrium chemistry covered? Is there a dedicated advanced analytical lab? Is the analytical class a service course? Institutional commitment to vocational training? How does the department meet the CPT guidelines?

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Analytical Chemistry at DePauw University Before Fall

2001

Year Fall Spring

1 Principles of Chemistry I Principles of Chemistry II

2Organic Chemistry IQuantitative Analysis

Organic Chemistry IIInorganic Chemistry

3 Physical Chemistry I Physical Chemistry II

4 Advanced Inorganic Chemistry Instrumental Analysis

Recommended Curriculum for a Chemistry Major

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Analytical Chemistry at DePauw University Beginning

Fall 2001

Chem 120: Structure & Function of Organic Molecules

Chem 130: Structure & Properties of Inorganic Compounds

Chem 240: Structure & Function of Biomolecules

Chem 260: Thermodynamics, Equilibria, and Kinetics

Chem 170: Stoichiometric Calculations

Chemical Reactivity Chemical Analysis

Chem 351: Chemometrics

Chem 352: Analytical Equilibria

Chem 353: Instrumental Methods

Chem 450: Method Development Lab

Theoretical and Computational Chemistry

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Institutional, Departmental, and Student Context

Institution private, undergraduate, residential university 2400 students very selective

Department 8.33 full-time faculty (1.33 in analytical) 80 declared majors (8 chemistry, 72 biochemistry) excellent operating budget and institutional support strong instrumentation in all major areas

Student Audience 24 students/section; 3 sections/year ~50% of students are chemistry or biochemistry majors ~70% fulfilling requirements for health science programs ~10% are first-year students and ~20% are juniors or seniors

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Course Philosophy

…to create an environment that develops a student’s capacity to look at problems through the lens of analytical chemistry; that is, to think as an analytical chemist?

“Can we teach analytical thinking? The answer is that we cannot. It is a thought process and each individual has a varying thought process. However, we can exercise the student’s thought processes by continually exposing him to real analytical problems during the course of his education.”

S. Siggia J. Chem. Educ. 1967, 44, 545-546

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Chem 260: Class Structural Detail

class: 14 weeks at 3 x 60 minutes

Main Topics “Big 3” topics are foundational to analytical chemistry additional topics common to “Principles of Chemistry II” are left to

other courses 8-10 days available to focus on additional analytical content

Additional Analytical Content ladder diagrams for visualizing equilibrium chemistry data analysis exercises

uncertainty in measurements statistical comparison of data sets modeling data outliers

pre-lab planning time

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Chem 260: Lab Structural Detail

lab: 14 weeks at 1 x 180 minutes team of three students instrument suite: Vernier LabPro data interface with pH, ORP,

temperature probes and drop counter; Ocean Optics USB-2000 visible spectrometer

data stored on network drive

Case Studies in Ethics (1 week)

Four Preliminary Labs (4 weeks) introduce instrumentation, software, and important analytical concepts detailed procedures provided focus on communicating results

Four 2-3 Week Project Labs (9 weeks) no (or minimal) procedure provided statement of goals and issues to consider students design experiment

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Preliminary Labs (and Analytical Content) Preparing Solutions

uncertainty in measurements summary statistics

Newton’s Law of Cooling fitting theoretical models to data significance testing

Determination of Acetic Acid in Vinegar pH calibration and measurement acid-base titrations primary vs. secondary standards

Characterizing an Oscillating Reaction Beer’s law calibration using external standards boxcar filters and ensemble averaging

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Project Labs (with goals)

Decomposition of H2O2 determine H for reaction verify that Fe3+ is acting as a catalyst

Thermodynamics of Ca(OH)2 Solubility determine G, H, and S for the solubility reaction determine the effect of temperature on solubility

Acid Dissociation Constants of Organic Dyes determine pKa for synthetic and/or natural organic dyes

Kinetics of the Bleaching of Dyes determine rate law for the reaction explore the effect of pH on the reaction’s rate

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Newton’s Law of Cooling Prior to lab

in-class data analysis exercise on measurement uncertainty lab experiment evaluating accuracy and precision for dispensing 10 mL

of reagent using various types of glassware

Experimental Details two temperature probes five trials with each variable initial temperatures

Data Analysis model data using y = Ae-Ct + B determine values for for T0, Ts, and k compare expected values to determined values compare two probes evaluate appropriateness of Newton’s law

T(t) = T0 + (T0 – Ts)e-kt

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Confusion with Error Analysis an average Ts of 23.19oC with a standard

deviation of ±0.58oC is not in agreement with an expected value of 22.7oC

an average Ts of 23.19oC (±0.58oC) with one probe is not the same as an average Ts of 22.38oC (±0.55oC) for a second probe

data analysis exercise on comparing data

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Data Analysis Exercise on Regression Geometer’s Sketchpad

Anscombe data sets

warming of cold probe

cooling of warm probe

Project lab on bleaching of dyes

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Characterizing an Oscillating Reaction ostensible goal for students is to

follow the BZ oscillating reaction spectrophotometrically

practical goal is to provide an introduction to visible spectroscopy

signal-to-noise ratio ensemble averaging boxcar smoothing Beer’s law external standards calibration curves

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Project Lab 1Thermodynamics of the Decomposition of H2O2

Project Goals What is the value of H for the reaction? Demonstrate experimentally that the role of Fe3+ is catalytic.

Issues to Consider To determine whether there is a relationship between two variables

you must ensure that all other variables remain fixed. A calorimeter will absorb some of the heat released during the

reaction. You will need to establish if the amount of heat absorbed by your calorimeter is significant and, if so, determine how to make an appropriate correction.

What are the properties of a catalyst? In determining a value for H you inevitably will make some

assumptions. What assumptions might you make? How can you minimize their impact on your analysis?

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Verifying that Fe3+ is not Consumed During the Decomposition of H2O2

each spectrum is average of 16 scans

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Project Lab 3Acid Dissociation Constants for Organic Dyes Project Goal

Determine the pKa of two organic dyes by adapting the procedure from G. G. Patterson, “A Simplified Method for Finding the pKa of an Acid-Base Indicator by Spectrophotometry,” J. Chem. Educ., 1999, 76, 395-398.

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Using Ladder Diagrams to Foster Intuitive Thinking

pHpH = pKa = 3.17

F–

HF

4.17

2.17Buffer Region

• class: simplify equilibrium problems, such as pH dependent solubility of CaF2

• lab: control the speciation of weak acids by controlling pH

HPLC retention of p-aminobenzoic acid

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Anthocyanin Dye in Cranberry Juice

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Student Response “I liked that way we tied the labs in with the

class…it helped me understand the material.”

“[The course] bridged the gap between chemistry in the lab and chemistry in the classroom.”

“Labs really pushed my critical thinking and writing abilities…I liked the way [the course] flows…everything is connected.”

“I have learned a lot in this class…on the whole, I have gained a sense of clarity, and dare I say confidence. Confidence to know that if I don’t get something, I can figure it out.

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Acknowledgments Camille and Henry Dreyfus Foundation

DePauw University

Nicole Sweet (DPU ’04)

Sharon Crary

Chem 260 students