Rethinking Quant: The Importance of Analytical Thinking

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Rethinking Quant The Importance of Analytical
Thinking

• David Harvey
• Percy L. Julian Professor
• Chemistry Biochemistry
• DePauw University
• Greencastle, IN
• harvey_at_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 Dont 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
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 170 Stoichiometric Calculations
Chem 240 Structure Function of Biomolecules
Chem 260 Thermodynamics, Equilibria, and Kinetics
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
  students 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 students 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
• Newtons 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
• Beers law
• calibration using external standards
• boxcar filters and ensemble averaging

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Project Labs (with goals)

• Decomposition of H2O2
• determine DH for reaction
• verify that Fe3 is acting as a catalyst
• Thermodynamics of Ca(OH)2 Solubility
• determine DG, DH, and DS 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 reactions rate

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Newtons Law of Cooling
T(t) T0 (T0 Ts)e-kt

• 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 Newtons law

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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

• Geometers 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
• Beers law
• external standards calibration curves

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Project Lab 1Thermodynamics of the Decomposition
of H2O2

• Project Goals
• What is the value of DH 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 DH 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

• class simplify equilibrium problems, such as pH
  dependent solubility of CaF2
• lab control the speciation of weak acids by
  controlling pH

4.17
Buffer Region
2.17
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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
  classit 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 abilitiesI liked the way the course
  flowseverything is connected.
• I have learned a lot in this classon the whole,
  I have gained a sense of clarity, and dare I say
  confidence. Confidence to know that if I dont
  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