Using Online Homework in Physical Chemistry Courses
C. M. Woodbridge
This paper was completed and submitted in partial fulfillment of the Master Teacher Program, a 2-year faculty
professional development program conducted by the Center for Teaching Excellence, United States Military
Academy, West Point, NY, 2009.
Introduction
Physical Chemistry. Those two words strike, if not terror, than at least knee-knocking fear into
the hearts of most undergraduate chemistry majors. To say that Physical Chemistry is not a
popular course is a gross understatement. Although, PChem it is not the capstone course in a
chemistry major, it is reasonably close. This course requires intimate knowledge of a significant
amount of material: Calculus, Physics, General Chemistry, Organic Chemistry, and Analytical
Chemistry. This is probably the first course in the chemistry major that requires the synthesis of
knowledge from a wide range of topics.
Most undergraduate physical chemistry courses are a one-year survey involving four
primary top ics: Thermodynamics, Kinetics, Quantum M echanics, and Statistical M echanics.
While these are all rather ambitious subjects on their own, many concepts in PChem involve
expanding on ideas learned in introductory chemistry. For example, in General Chemistry,
students are usually required to memorize or recognize the equation used to calculate the
enthalpy of reaction under standard conditions:
∆ rxn H o =
∑n ∆
i
products
f
H io −
∑n ∆
i
reac tan ts
f
H io
<1>
Comment [C1]:
When they get to PChem, we explain where the equation comes from (and frequently derive it
from first princip les, e.g., dH = dU + PdV + VdP for a system which only undergoes PV work 1)
with the idea that students will no longer have to simply memorize this equation. Why then,
does PChem inspire such terror into the heart of undergraduate and graduate students alike?
There have been more studies about factors which influence student success in General
Chemistry courses.2-4 Some factors which have been studied previously are math ability,
background in chemistry , and, surp risingly, student attitudes. These studies5 “demonstrate that
p erformance in general chemistry improves with increased formal reasoning and processing,
better mathematics skills, more previous chemistry courses, better self-rating and attitudes about
the course, and higher scores on placement exams.” Factors contributing to student difficulties
in general chemistry 3 (as identified by the instruction staff) are presented in Figure 1. Since, in
my opinion, PChem is an exp ansion on topics students encountered previously in general
chemistry , I would expect that similar factors would influence success in a physical chemistry
course. The only excep tion in Figure 1 would be “cultural shock” since, presumably, juniorlevel students are no longer new to the university system.
Although there are relatively few students about factors influencing success in a physical
chemistry courses, these few studies find a correlation between success and mathematical
background.2, 6-9 One study 9 has presented perceptions of students and faculty on what causes
learnin g difficulties. These perceptions are shown in Figure 2 (student perceptions) and Figure 3
(faculty p ercep tions). There seems to be good overlap between the concerns of both faculty and
students.
Overall, I agree with the many of the students’ views shown in Figure 2. Although
PChem was a course I looked forward to in college, based on my undergraduate experience, the
2
course was based heavily on deriving equations with no accompanying discussion about the
concep ts and we used handouts our instructor wrote so we didn’t have a text. I made few
connections between the course material and everyday life and if there were connections
between the lecture and the labs, I frequently missed them. As an instructor (TA or professor), I
made a conscious effort to try and avoid perpetuating these negative experiences in my courses.
3
Learning Difficulties
Staff
Course
Students
Power relationships
Cohort Number
Motivation
Fragmentation
Study Skills
Difficult Concepts
Preparation
Content Overload
Cultural shock
General Ability
Prior learning
Conceptions
Methods
Prior experience
Math
Lab
Vocabulary
Figure 1: Perceptions of student difficulties in general chemistry by the instruction staff.
Adapted from Ref. 3.
4
Learning Difficulties
Student
Course
Staff
Concern re:
concept usability
(11%)
Course is
cumulative (19%)
Teacher-centered
instruction (44%)
No motivation and
interest (37%)
Abstract concepts
(52%)
No teaching
strategy (11%)
Uncertainty about
concepts (15%)
Overload of course
content (41%)
Inadequate
examples in
lectures (26%)
Course is too
mathematical (33%)
Inadequately
prepared lectures
(26%)
Inconsistency in
exams/lecture/lab
(37%)
No deep
understanding
(37%)
Lack of everyday
applicability (26%)
Lack of resources
(22%)
Figure 2: Students’ perceptions of their difficulties in PChem. Percentages reported come from
students’ responses on survey questions. Adapted from Ref. 9.
I also agree with the majority of the issues identified by the faculty presented in Figure
3.9 One of the most frustrating obstacles to overcome is the lack of student motivation. Since
PChem is not usually anyone’s favorite class, motivational issues are significant. Motivational
issues are comp licated by the broad range of abilities of the students in a class. For example, I
had a class of 7 students at Hillsdale College. The “bottom” of my class was a group of two
students who scored B/B- marks on the examinations. In this class, there were some real
sup erstars. It was very hard for these students to be earning Bs while the rest of their classmates
5
were earnin g As and they felt dumb. Designin g examinations and problem sets that would
challen ge the top of the class without making the “bottom” of the class feel dumb or overlooked
was a real ch allen ge.
Learning Difficulties
Student
Staff
Course
Successful students
inhibit motivation
Lack of time and
support
Abstract concepts
Lack of motivation
Lack of professional
development
Exams promote
memorization
Tricks rather than
understanding
Overload of
teaching work
Teacher-centered
teaching
Socio-economic
conditions
Too many different
things to do
Overload of course
content
Differences in
background
Lack of resources
Overlooked
students
No tutorials or
tutors
Overcrowded
classes
Figure 3: Faculty p erceptions of student difficulties in PChem. Adapted from Ref. 9.
Both students and faculty mention the lack of resources available. While there are many
PChem books to choose from, there are relatively few lab manuals (two I know of and a third
that is out of p rint). Very few books come with a “course packet” that can be loaded in course
management software like Blackboard but most come with an accompanying solutions manual
for students and instructors. M any institutions use Atkins’ text and this comes with the most
supporting resources: solutions manual (instructor and student versions), an e-book, copies of the
6
figures/tables in the text for instructors to use in lectures, and the ARIS homework system
contains questions from Atkins. If you choose another book (e.g., M cQuarrie and Simon), all the
figures from the text are available from the publisher to be downloaded. This is in stark contrast
to the volumes of resources available for a General Chemistry text. For example, Silberberg
(p ublished by M cGraw Hill) comes with a test bank, a package that can be uploaded to
Blackboard, a student study guide, a student solutions manual, an instructor’s solutions manual,
online homework, CDs containing animations, pre-made PowerPoint slides, downloadable
figures and tables from the text, and the list just goes on. Can students and instructors manage
without all these resources? Certainly. However, it would be nice to have some additional
resources (besides another physical ch emistry book) to direct students to when they need help.
Students also look for tricks to solve p roblems and tricks to aid in memorization of
material rather than looking for a deep understanding of the material. M emorization and tricks
may have worked in previous chemistry courses and they may have even gotten reasonable
grades using these methods, but in PChem these methods typically stop working. Students need
to have a strong understanding of the concepts as well as be able to solve problems; since there
are many equations presented in a given chapter of a physical chemistry textbook, the student has
to determine which one is the correct equation to use in a particular situation. Without an
understanding of the underly ing concepts, students are going to consistently make silly mistakes
like try ing to app ly the ideal gas law to a system in which one is asked to calculate the
temp erature of ice. In other words, students have to not only know the equation but also the
restrictions that come along with the equation; without this additional knowledge, all the tricks in
the world aren’t going to help students.
7
Homework that incorporates both conceptual problems and mathematical problems is, I
think, one of the best predictors for success in the course. “Success” may be measured in terms
of a score on a graded event or student satisfaction that they are “getting it.” Additionally, I have
been using Blackboard to do online homework assignments in CH480, Physical Chemistry for
Life Sciences. I chose this method over more traditional pencil and paper methods since students
are able to get instant feedback on their work. Granted, the feedback is limited to whether or not
the answer is correct, but this is more feedback than traditional pencil-and-paper homework sets
get since I allow students an unlimited number of attempts on their homework. This is the third
time I have used Blackboard in this manner – p reviously, I used this method in a similar course
offered during the summer at the University of Nebraska-Lincoln. Subsequent sections of this
p ap er will describe the assessment methods used to determine whether online homework was
beneficial in PChem as well as the results obtained for CH480 during the fall of 2008.
8
Assessment Methods
The methods described below were used to assess student performance in CH480 and the success
of using online homework assignments. The students’ background in general chemistry was
considered. There are three possible tracks: 101/102 (regular); 151/152 (advanced); or
validation. Which track a student took was comp ared to the students’ course grade in order to
assess whether this had an impact on their performance in CH 480.
Students’ performance on graded events were ranked as “Excellent” (> 76%),
“Satisfactory ” (64-75%), or “Poor” (<64%). Graded events evaluated in this manner included
the p re-lesson HW, WPRs, and the TEE. Pre-lesson HW was based largely on students’
knowledge of fundamental concepts from p re-requisite courses. A small percentage of the work
(30%) was based on more sophisticated concepts outlined in the reading. WPRs and TEEs
contained questions drawn from fundamental concepts as well as 480-level applications of this
knowledge.
In-class work was also evaluated using p eriodic one-minute papers10 and lingering
questions papers (aka “muddiest point".9 Each lesson had an “earn back” opportunity where
students wrote a one-minute p ap er, lingerin g question paper, or took a short quiz covering
concep ts I felt they hadn’t yet mastered. Student work was ranked as “Excellent,”
“Satisfactory,” or “Poor” in each case. Rankings for quizzes were based on the percentages
given in the p receding p aragrap h while rankings for the papers were based on the following:
Excellent = good question or good summary of the main point at the CH480 level; Satisfactory =
good question or good summary of the main p oint at the CH101-102 level; Poor = question or
summary indicates they missed the point of the lesson entirely.
9
Blackboard provides a wealth of statistics as well: the number of attempts a student used
to comp lete an assignment, what time they began an assignment, and all their responses. While
Blackboard doesn’t retain information about how long a student worked on an assignment, it is
easy to get a “flavor” of this by comparing start times.
10
Results
In the fall of 2008, 30 firsties were enrolled in CH480, Physical Chemistry for Life Sciences. All
students were life science majors and most planned to either go to medical school or hoped to
branch M edical Service Corps. In this class, 18 students took CH101-102, 6 took CH151-152,
and 6 validated the general chemistry sequence. The grade distribution for each of the different
tracks is p resented in Table 1 below. None of the students who validated or took advanced
general chemistry received a mark below a B, which suggests that students' backgrounds do have
an imp act on their success in physical chemistry.
Table 1: Number of students receivin g nominally an A, B, or a C in CH480 sorted by the general
chemistry sequence they took.
A
B
C
CH101-102
4
10
4
CH151-152
4
2
0
Validation
4
2
0
When comp aring students' scores on homework, WPRs and TEEs, scores which remain
the same or increase from homework to WPR to TEE would suggest students learned the
material or retained what they learned. Homework sets included both calculations and
concep tual questions. Students were allowed to submit each homework set an unlimited number
of times in Blackboard and they were given some (albeit minimal) feedback which included
whether their answers were correct and some generic hints on approaching a correct answer.
11
Table 2: Comparison of course averages from homework to WPR to TEE. The events are colorcoded as follows: green = > 76%; yellow = 64-75%; red = < 64%.. The average for WPRs
includes only those students who took all four WPRs.
Homework
WPRs
Tee MC
TEE Calc
TEE
Thermodynamics 84.80%
71.83%
64.67%
63.40%
64.03%
Kinetics
82.32%
81.43%
58.33%
68.20%
63.27%
Quantum
88.62%
85.41%
57.83%
75.50%
66.67%
App lications
72.30%
64.85%
69.00%
66.93%
TOTAL
86.29%
75.40%
71.65%
79.81%
65.54%
Based on the data shown in Table 2, instead of scores increasing or remaining nearly unchanged
as time went on, scores went down. The drops were not insignificant either; for example,
averages dropp ed at least 10% from the homework to the WPR to the TEE in, for example,
Thermodynamics. This trend, in my opinion, has more to do with the available resources for
each grad ed exercise than students' knowledge actually decreasing over time. On homework,
students are allowed to consult their books, their notes, their classmates, online resources posted
in Blackboard, and me. In p rincip le, they have an unlimited amount of time to complete each
homework set as well. On WPRs and the TEE, however, the students are under time pressure
and are only allowed to use a single, double-sided exam data sheet. This type of trend is also
seen in other PChem classes, as shown in Table 3.
12
Table 3 Comp arison between physical chemistry courses taught at Hillsdale College, University
of Nebraska-Lincoln, and USM A.
# semesters
Hillsdale
10
8.2
13.1
86.1
Course
Avg.
89.7
UNL
10
29.6
12.4
84.7
79.6
USMA
1
30
40
86.2
84.9
85.7 + 0.8
85 + 5
Average
Avg. #
students
# HW sets
HW Avg.
Data p resented in Table 3 from Hillsdale College comprises 5 years of a 2-semester Physical
Chemistry sequence taken only by Chemistry majors; the course includes a lab component. Data
from UNL comp rises 4 semesters of the first semester of a year-long Physical Chemistry
sequence taken by Chemistry, Biochemistry, and Chemical Engineering majors with no lab
comp onent as well as 6 semesters of a one-semester Physical chemistry course geared towards
Biochemistry majors. Neither UNL course has an accompanying lab. The one-semester course
focuses p rimarily on Thermodynamics and Kinetics; a small unit (2 lessons) on spectroscopy
was included. Courses taught at UNL and Hillsdale were conducted in a traditional lecture
format. Interestingly , only the Hillsdale courses show an increase going from the homework to
the WPR to the final grade. These students did p aper and pencil homework sets and had one
problem set p er chapter. They did far fewer problems than either online course, which seems to
suggest that dong more p roblems and including conceptual problems does not seem to improve
retention of the material.
In addition to comp aring course averages on various graded events, student performance
on individual top ics was tracked. Three problems on the TEE came almost verbatim from
13
previous WPRs. Student performance on these problems was compared between similar
problems on HW and WPRs. The results are presented in Table 4.
Table 4: Percentage of students who earned at least 90% of the points on a graded event for the
topic indicated. Percentages correspond to students attempting the problem and not the class as a
whole.
HW
WPR
TEE
% on TEE
pH of adenosine
0
17
17
63.40
Analysis of mechanism
93
13
9
68.20
Particle in a box
79
40
24
66.60
The thermodynamics question, pH of adenosine, improved dramatically between the homework
and the WPR and students at retained their knowledge about this problem for the TEE. In
contrast, the p ercentage of students who did well on the quantum mechanics question (particle in
a box) and the kinetics question (analysis of a mechanism) dropped dramatically as time went on.
The kinetics question on the HW has a very high score because of the level of the question asked
was more at the 102 level rather than the 480 level. The decrease in demonstrated knowledge
seems to occur no matter how the data are analyzed.
14
Discussion
The answer to the question about whether online homework improves students' success on
physical chemistry seems to be “no” or “very little” based on the data presented here. Why,
then, do textbook comp anies continue to sp end money to develop and promote online homework
systems ran gin g from simple test banks which can be added to course management systems like
Blackboard or sophisticated interactive sessions like those in Aris or WebAssign? Just like
athletic p ractice or practicing musical instruments, students need to drill with chemistry
problems and test their fundamental knowledge. Online homework seems to me to be a
reasonable alternative to the pencil and paper type of homework. The data in Table 5 seems to
support this.
Table 5: Comp arison of average homework and course scores in a one-semester Physical
Chemistry course.
# semesters
Avg. #
Avg. # HW
HW Avg.
Course
Students
sets
Avg.
Pencil & p ap er (UNL)
4
32
9.75
88.5
83.4
Blackboard (UNL)
2
31
22.5
85.6
81.4
Blackboard (USM A)
1
30
40
86.2
84.9
Blackboard Total
3
30.5
31.2
85.9 + 0.4
83.2 + 2
87 + 1
83 + 2
Overall
Students who did p encil and p ap er homework had a course average which was 6% below their
homework average, which suggests that their exam scores brought their grades down. In
contrast, students who did Blackboard homework had course averages which were 2% lower
than their homework averages so the negative impact of exams on their overall average was
much less. While students’ knowledge of how to solve particle-in-a-box problems seemed to
15
decrease with time in CH480, their course grade didn’t drop very much (~3%) compared to their
homework grade. Homework was only 15% of their overall grade and examinations were 55%
of their overall grade. At the end of the day, it would seem the CH480 students demonstrated
reasonable comp etence with the material in the course overall.
So why was there no clear trend of imp rovement from homework to WPR to TEE in
CH480? Homework works if students work homework properly . One study 2 shows a
correlation between homework scores and success; anecdotal evidence supports this. There
seem to be three main problems with homework: 1) copying and wargaming in Blackboard; 2)
time management; and 3) student attitudes about PChem. These attitudes prevail whether
homework is assessed online or via pencil and paper assignments. Fundamentally, everything
comes down to time -- students were not convinced that homework is "physical chemistry
practice" just as a daily PT routine is practice for the bi-annual PT tests and therefore students
tried to get the most points for the minimum input of time. The analogy between problemsolving and athletic practice seems to be particularly apt at USMA and it is an analogy that has
been around for awhile.11
The online homework assignments can be classified into four categories: calculation (C),
mostly calculations (MC), mostly short answer (M SA), and short answer (SA). Calculation
questions were numerical calculations where students had to enter a number. Short answer
questions were either true/false, multiple choice, or fill in the blank. Course averages were
59.4%, 54.1%, 79.3%, and 90.1% for C, M C, M SA, and SA, respectively. Overall, the more
calculations p resent in the homework, the more the average dropped. I would have expected M C
to have a higher p ercentage than C, but there were 5-6 students who never did calculations on
these M C assignments but they had to attempt a calculation to get any points on the C type
16
assignments. This data fits the "most points for the least time" model very well. Additionally,
there were 5-6 students who would only submit one attempt on a homework assignment and take
whatever score they earned on the assignment whether it was good or bad. There were students
in this group who took this to the extreme of not going back and changing incorrect true/false
answers.
Copying and wargaming (i.e., goin g through all possible answers on true/false and
multiple choice questions without much thought) are perceived to be time-saving devices. These
behaviors will lead to individual students having high HW scores, lower WPR scores and lower
scores on the TEE. Frankly copy ing can be a p roblem whether students do online homework or
paper and pencil homework. While I have no p roblem with students collaborating with one
another, I do caution them that copying is a poor choice since they will not be able to rely on
their classmates during examination conditions.
Students did comment that they didn’t like Blackboard because they didn’t know why
their answers were wrong. This was p roblematic for most students as they did not start the
homework assignments until after 5pm the night before it was due; at that time, I was usually
home and unavailable on e-mail or for AI. To be fair, Blackboard is a passive system and
doesn’t understand that the answers 0.003, .003, and 3E-3 are the same so the students have a
good point. I would go back and give them credit for correct answers that Blackboard marked
wrong due to a simple notation issue, I understand why it was hard for them to decide whether
their answer was wrong because of notation or their answer had a more serious problem. To try
and alleviate these issues, I p ut ranges on numerical answers in order to eliminate rounding
errors and (most) issues with significant figures. I also tried to put cues in the text of the
problem about the typ e of answer Blackboard was expecting (e.g., use scientific notation, yes/no
17
etc.). I was also very proactive about checking work as it was submitted and contacting students
to let them know that their answer was wrong due to a rounding error or a mathematical error or
a more serious error. Some students felt that was sufficient help but others disagreed. And yet,
there were some students who thought Blackboard was OK (from HW #40 – PChem Top 5 i.e., 5
best things about PChem):
• HW every lesson kinda makes you read the material
• Although I initially was against use of blackboard for homework assignment, I am
now a fan of the hw assignments for they prepare you for the WPRs and are a good
test of reading material.
• BB homework
And some advice to future CH480 students (from HW #36 – Letter to the future):
• Do the suggested p roblems for sure along with the assigned homeowrk [sic]…without it,
you will be unsuccessful.
• Also, use Blackboard to your advantage – not just for homework credit, but also as a
learnin g aid …. Stay up on the homework even if you do not understand because the
problems will come in handy when study ing for the big tests.
• The best advice I can give to a p -chem student (under Dr. Woodbridge) is to do the
homework assignments comp letely every night and try to figure out the equations
BEFORE going to class. Also, read the discussion boards and the Lesson slides – they
help a lot with the homework, often where Tinoco is incomprehensible. Knowing the
homework problems sets y ou up for success on the problem-solving portions of the
WPRs.
Desp ite some students’ dislike of the online homework and some well-thought out
constructive criticisms on their part, I would use it again. The usage statistics are invaluable as
they allow me to determine whether a given assign ment was too long or too hard or confusing. I
can tell approximately how long students sp end on a given assignment as well as how they are
approaching about the assignment. Prior to the lesson, I can review the assignment summary and
determine which p roblems they struggled with on and plan for this accordingly, which makes for
a more student-centered lesson. I do think the students who were focused on learning the
material did benefit from doing more p roblems than they would have done using paper and
18
pencil homework assignments. The students who copied other students or wargamed their way
through the short answer questions are, I think, the same students who would have copied other
students papers or turned in p artially comp lete submissions if we used pencil and paper
homework assignments. It is my opinion that the students looking for shortcuts or to minimize
their time have the wrong attitude about PChem – they are afraid of the course, not interested in
the course, they lack confidence that they can do well in this difficult course, etc. One paper7
notes that faculty expectations and students’ perceptions seem to be at odds; that certainly seems
to be the case here since I think online homework is great and useful while the average student
disagreed.
A search of the keyword “Physical Chemistry ” on the Journal of Chemical Education
website returns 1492 articles from the first issue until the April 2009 issue. Of these articles, the
majority are writeups of good lab exercises, good class exercises, or how best to communicate a
difficult concept in PChem. There are exp lanations of why premedical students should be
required to take p hysical chemistry and what content is appropriate for them12 as well as course
structure and content.13 Ironically, the course structure described in reference 13 hasn’t changed
much in the last 40 years. There are articles about how faculty should approach PChem so that
students get the most out of the course; these approaches include Keller-type systems.14-16 Most
recently , there has been a great deal of attention drawn to using M athematica17 to solve/approach
physical ch emistry problems and using Process-Oriented Guided Inquiry Workshops.18-19 We
the faculty are still struggling to make PChem palatable to students and yet hold them to a high
standard.
19
Conclusions
The use of online homework in CH480 met with mixed success. The students were not
necessarily big fans of online homework but I thought it made the course more student-centered
and provided a wealth of data about how students were approaching the homework.
Performance on graded ev ents decreased goin g from homework to WPR to the TEE rather than
increasin g but y et the drop between total homework averages and the course average is the
smallest in courses like CH480 where online homework is used. Whether this drop can be
attributed to the nature of the graded event (homework is unlimited resources and time with
many different questions vs. examin ations have limited resources and time and often only one
typ e of question on a top ic) or student attitudes toward PChem in general is unclear. Students
were satisfied with the course overall. Next year, I do plan to use online homework again. I do
plan to try and address the student concerns with regard to Blackboard as best I can and I plan to
modify the homework so that each homework set contains questions about fundamental concepts
students should have retained form p revious courses (~40%), questions about PChem-level
concepts and skills students should acquire from the reading (~20%) and questions from the
previous lesson which will allow them additional p ractice on key calculations.
20
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18. For examp le, Hinde R.J.; Kovac, J. Student Active Learning in Physical Chemistry. J.
Chem. Ed. 2001 78, 93-99.
19. Process Oriented Guided Inquiry Learning (POGIL) homepage. http://new.pogil.org/
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