Active learning materials for teaching electrochemistry
Active learning materials for teaching electrochemistry
Thomas J. Wenzel 0
0 Department of Chemistry, Bates College , Lewiston, ME 04240 , USA
1 Thomas J. Wenzel
Research shows that active classroom environments in which
students work in small groups on questions or problems posed
by the instructor are effective at promoting learning [
One of the tracks in the primary program supported by the US
National Science Foundation aimed at improving
undergraduate education is titled BEngaged Student Learning.^ The
conclusion from these studies and reports is that instructors should
move away from a classroom environment that is entirely
dependent on the use of lectures.
One reason for the relative ineffectiveness of lectures for
developing complex subject matter is that students often drift
on and off task. This results in incomplete notes and gaps in
their ability to follow the logic of the presentation [
degree to which participants drift off task increases further into
a lecture [
16, 18, 19
]. Excellent note-taking ability, auditory
skills, and a high working memory capacity are needed for
effective learning in a lecture; however, many people do not
have these attributes [
]. Probing the entire audience’s
understanding of the material being presented is difficult. Many
students may not appreciate that they do not actually understand
the material being presented. Finally, many lecture participants
are inhibited from asking or answering questions [
The inadequacy of lectures at promoting learning is
apparent if one considers what is known about how people learn.
Cognitive scientists have found that knowledge is constructed
in the mind of the learner [
]. During this construction
process, new knowledge is connected to knowledge the
learner already possesses [
]. Telling students the link
between new topics and prior knowledge, as occurs in a lecture,
is less effective than providing a format in which students
must draw on their own knowledge first. Asking students to
make appropriate connections between a new topic and prior
knowledge may also show that many students have incorrect
ideas and beliefs about fundamental concepts . It is
important that students with help from the instructor confront
their misconceptions to promote more effective learning.
Active classroom learning involves the use of pedagogies
where students engage with the material by working in small
groups on questions or problems on the topic being developed.
Unfortunately, there is a dearth of active learning materials
available to instructors of analytical chemistry courses.
Electrochemistry is a subject area covered in many
undergraduate chemistry courses. In this article, I will describe a set of
active learning materials suitable for the coverage of
electrochemistry in the undergraduate analytical chemistry curriculum.
These materials are freely available to instructors and students
through the Active Learning site of the Analytical Sciences
Digital Library . Because materials are under the Creative
Commons Copyright, instructors can use the entire unit on
electrochemistry, any portions of the unit, or modify the materials in
any way they wish to suit their own needs. They can freely
distribute these materials or modified versions to their students.
Active learning materials
The materials developed for active learning of electrochemistry
consist of a set of learning objectives, in-class question sets,
textual material to support the in-class questions, and an
instructor’s manual . Group work on in-class questions is effective
for covering electrochemistry because students have prior
knowledge from introductory-level courses that they need to
draw upon to understand and answer the questions. The
instructor’s manual provides guidance to help instructors more
effectively use the in-class question sets. Topics covered in the
module on electrochemistry include basic concepts (the relationship
between chemical energy and electrochemical potential,
electrochemical cells) and electrochemical methods of analysis
(ion-selective electrodes, electrodeposition, coulometry,
titrimetry, and anodic stripping, linear sweep, differential pulse
linear sweep, and cyclic voltammetry. A set of assessment
questions and answers for the unit that align with the different
learning levels in Bloom’s taxonomy [29, 30] are not on the
ASDL site but are available from the developer of the module
on request. My approach when using these materials is to have
students work in groups of 3–4 on the in-class questions before
giving them the text from the module that provides the answers
to those questions.
For those who cover electrochemical topics not included in
the module discussed herein, there are two other resources
available on the ASDL site that are freely available under
the Creative Commons Copyright [31, 32]. Chapter 11 of
the online textbook Analytical Chemistry 2.1 covers a wide
array of electrochemical topics . A text resource on basic
electrochemistry topics covers fundamentals, voltammetric
methods, and aspects of the hardware needed to conduct
electrochemical measurements .
The first set of in-class questions asks the students to define
the terms oxidation, reduction, oxidizing agent, and reducing
agent and describe what is meant by a half reaction. They are
asked to provide examples or write an appropriate expression
for these and then determine whether it is possible to write an
equilibrium expression for a half reaction. Most students are
familiar with these concepts through a prior course in general
and/or organic chemistry.
The second set of in-class questions is designed to have the
students reflect back on the concept of chemical energy that
they learned something about in general chemistry and
perhaps physical chemistry depending on their year of study. This
is achieved by having students consider a simple reaction of A
rearranging to product B under the constraint that the sum of
the concentrations of A and B is always 2 M. Students are
asked to draw a plot for the value of G along a reaction
coordinate for different amounts of A and B for the example where
the reaction has a large or small equilibrium constant.
Exploring these plots allows us to examine the reason for
using ΔG instead of G, the need for defining a standard state
requiring the use of ΔGo values, and the convention of using
negative values of ΔG for a reaction that favors products and
positive for a reaction that favors reactants. Also, it allows us
to revisit the relationship in Eq. 1 that they have seen earlier in
the chemistry curriculum.
ΔG ¼ RTlnK þ RTlnQ
Providing students with the relationship between
electrochemical potential and free energy allows us to write and
examine the Nernst equation. A presentation and discussion
of the electrochemical series is then possible.
Students taking an analytical chemistry course have usually
learned about the basic design of electrochemical cells in a
prior course, so the next set of questions asks them to describe
what they remember about an electrochemical cell, explain the
processes responsible for conduction of electricity in an
electrochemical cell, describe the purpose of a salt bridge and what
would be put inside a salt bridge, and situations that would
result in the irreversibility of an electrochemical process. For
the latter question, students often propose that an
electrochemical reaction that forms a gaseous product would be
irreversible, allowing us to discuss ways to design an electrochemical
system such that the gas will not escape the cell. The concept
of an overpotential is usually something that students have not
considered in any prior courses.
With an understanding of the Nernst equation and
electrochemical cell, students are given a set of conditions for the
reaction and asked to calculate the standard state potential and
equilibrium constant. Then, they are asked to calculate the cell
potential for a set of non-standard state conditions. Finally,
since one of the half reactions includes H+, they are asked to
calculate the cell potential at higher pH to examine the
significant effect that pH has on cell potential.
Having developed background concepts of
electrochemistry, the remainder of the unit addresses a number of
electroanalytical methods. The first is on ion-selective
electrodes. For this topic, students are given the text in advance
and expected to read it in preparation for the class where we
discuss the topic. Each of the ensuing areas is prefaced with
a brief discussion of the nature of how the method is
performed, and then students are given questions to work on in
groups aimed at developing additional attributes of the
technique. For electrogravimetry or coulometry, this involves
determining whether certain species at certain concentrations
will interfere with the plating of an analyte. One important
point of this calculation is for the students to realize that the
reduction potential needed to plate a metallic species
increases as the concentration decreases, making it more likely
that other species might interfere. For coulometry, the
students are first asked to draw the plot that would be obtained
for current as a function of time if a constant potential is
applied, and then asked how they relate the outcome of the
plot to concentration. The next question asks them to
identify the advantages of coulometry over electrogravimetry.
In addition to classical redox titrations using a
colorimetric indicator, the methods of coulometric,
amperometric, and potentiometric titrations are covered. Having
discussed a classical redox titration and the way in which
a coulometric titration is performed, students are asked to
describe the advantages of using a coulometric titration.
Having described the methodology for performing an
amperometric titration, students are asked to draw the plot
that would be obtained if each of the following occurred
using a reducing potential: (1) only the analyte undergoes
a reduction at the applied potential, (2) only the titrant
undergoes a reduction at the applied potential, and (3)
both the analyte and titrant undergo a reduction at the
The example of the titration of iron(II) with cerium(IV) is
used to develop an understanding of a potentiometric titration.
The concept of a junction potential has been previously
discussed in the development of electrochemical cells and
ion-selective electrodes. The first questions are aimed at
getting students to appreciate which half reaction is best for
calculating the junction potential before and after the equivalence
point. Students then calculate the junction potential at
different points of the titration.
The general concepts of voltammetric methods are
described in a brief lecture and then students are asked to
consider how electrostatic migration can be eliminated in an
electrochemical cell and why samples analyzed by voltammetric
methods are usually purged with nitrogen or another inert gas
before the analysis and maintained under an inert atmosphere
during the analysis.
For anodic stripping voltammetry (ASV), students are
asked to consider the analysis of a solution that contains
Cd(II) and Pb(II), given the voltage profile that is applied as
a function in time in Fig. 1, and asked to draw a plot of the
current that would be measured in the deposition and stripping
steps. They are reminded that a microelectrode is used, which
is particularly important to consider in the deposition step.
Earlier in the unit, the importance of using an electrode with
a large surface area in electrogravimetry and coulometry was
emphasized. After arriving at a suitable plot of current as a
function of the applied potential, students are asked to
determine what feature of the plot can be related to the
concentration of the metal and describe advantage(s) that
ASV offers over coulometry or electroplating.
For linear sweep voltammetry (LSV), students are asked to
draw the current that would be measured for a solution
consisting of Cd(II) and Zn(II) for the voltage profile shown
in Fig. 2. The problem indicates that the concentration of
Cd(II) is about twice as large as that of Zn(II) and that the
solution is stirred. They are then asked what feature of the plot
can be related to concentration and what feature can be used to
identify the species.
They are then given the voltage profile in Fig. 3 for
differential pulse linear sweep voltammetry (DPLSV), a description
of when the current is sampled and what is plotted, and asked
to draw the resulting plot. The name of the method is only
identified for the students after they have worked in their
groups to satisfactorily draw the plot that is obtained.
Finally, they are asked to identify advantages of DPLSV over
For cyclic voltammetry (CV), students are given the
voltage profile in Fig. 4 and asked to draw a plot of the current
(yaxis) versus voltage (x-axis) that would be measured for a
solution in which Fe(III) in ferricyanide (Fe(CN)63−) is
reduced to Fe(II) during the reducing phase of the CV voltage
profile. They are asked to contrast the plot that would be
obtained for an (1) electrochemical reaction that is chemically
irreversible and forms an electrochemically inactive product
and (2) a reversible chemical reaction in which only the
reverse reaction has an overpotential, but the potential
eventually is sufficient to complete the reverse reaction. Finally,
assuming a reducing potential is applied, the students are asked
to propose a reaction mechanism that would explain the CV
shown in Fig. 5 in which the first voltage cycle is shown as a
solid line, the second voltage cycle is shown as a dotted line,
and the third voltage cycle gives the same output as the dotted
The instructor has an especially important role in the effective
use of active learning exercises described herein. The in-class
exercises consist mostly of broad, open-ended questions where
students need to consider knowledge from prior courses or from
earlier parts of the unit that apply to the questions. Tips for
effective facilitation of exercises of this nature have been
described in a prior report on an active learning exercise for
molecular and atomic spectroscopy  and are included in the
instructor’s module that accompanies the electrochemistry
module. The in-class questions and accompanying textual
material described herein can easily be modified to suit a particular
instructor’s needs and interests. Furthermore, only a portion of
the materials need be used. The materials described herein are
available through the Active Learning site on the Analytical
Sciences Digital Library [27, 28] under the Creative
Commons Copyright, enabling instructors to use all, some, or
modified portions of them for free with their students.
Funding information I thank the National Science Foundation for
supporting this work through a Transforming Undergraduate Education
in STEM Award (DUE-1118600).
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Wenzel TJ . Active learning materials for molecular and atomic spectroscopy . Anal Bioanal Chem . 2014 ; 406 : 5245 - 8 . Thomas J. Wenzel is the Charles A. Dana Professor of Chemistry at Bates College in Lewiston, ME. He currently carries out research with the aid of undergraduate students in the area of chiral NMR shift reagents . His research accomplishments were recognized with the 2010 American Chemical Society Award for Research at an Undergraduate Institution . He is active in efforts to reform the undergraduate analytical chemistry curriculum to include inquiry- and project-based experiences. His educational activities were recognized through receipt of the 1999 J.C. Giddings Award for Excellence in Education sponsored by the Analytical Division of the American Chemical Society . More information about his activities can be found at http://www.bates.edu/ chemistry-biochemistry/faculty/thomas-wenzel/.