Equilibrium Activities for High School Chemistry Classrooms
The Cadre II Equilibrium team will present with this paper; computer animations, classroom hands on
activities, and computer simulations which were chosen and used by its members in order to introduce and
better explain the concept of chemical equilibrium to their students within the high school classroom. Also
presented will be the methods and discussion with student/teacher feedback for each.
Team 8 Equilibrium AKA: Team Gonk consists of members with a range of eight and a half to thirty years
of teaching experience. Each member teaches at least one chemistry one class with a class load consisting
also of biology, physics, general science, and advanced chemistry. The members are Jeff Heinrich (BA
Chemistry) from Rowva High School, Todd Keating (BS Chemistry, MA Science Education) from
Charleston High School, Bryan McMillan (BS Biology) from Dieterich High School; and Teresa
Butterfield (BS Biology, MS Science Education) and Julie Morris (BA Biology) both from Manteno High
School. This paper is a result of our participation in the ICLCS (Institute for Chemistry Literacy through
Computational Science) program at the University of Illinois. This is an NSF research based program
targeted at rural high school chemistry teachers and their students.
ABSTRACT:
Teaching equilibrium within the high school chemistry classroom can be challenging. Equilibrium is a
dynamic system that looks static at the macro level. Looking at the atomic levels through computer
simulations allows students to visualize the dynamic system. This paper describes hands-on activities, as
well as computer animations and simulations that were developed and used by high school teachers and
students in order to explain the concept of equilibrium. Teacher-student feedback is described for each
activity. Each activity includes teacher instructions and/or worksheets which can be found in the
documents section of our post.
Bucket Equilibrium Demo – This is an activity recommended to be an introduction to equilibrium.
Methods:
A great visual demonstration of how equilibrium works uses buckets of water and student volunteers. Two
buckets represent the reactants and products. The amount of water in the buckets is adjusted for the
multiple steps of the activity. Students move water between the buckets with cups at an equal rate to
represent the forward and reverse reaction. This activity explores what happens when only reactants are
present, when there are equal amounts of reactants and products, when there are more reactants than
products, when products are removed and when reactants are added.
Results:
Each student was able to participate in the water exchanges and get their “hands wet”. They were able to
visually see what happens in each of the scenarios described in the methods. One problem was that when
the reactant was being added, even though that should drive the reaction to the product side, the reactants
appeared to be increasing. Removing the product had a similar effect.
Discussion:
The bucket demonstration is a good visual for seeing how changing the concentration of reactants and
products affects the equilibrium position in a reaction. The demonstration had to be rewritten so that the
amount of reactant added was limited and the student adding the reactant then participated in moving
reactant into the product bucket.
©2011 University of Illinois Board of Trustees • http://islcs.ncsa.illinois.edu/copyright
Dogfight – This is also an introductory activity but it does not work out as well as the Bucket Demo.
Methods:
Another component of our ice cube is an activity entitled ‘Dogfight’. The idea is to introduce students to
the general concept of dynamic equilibrium using a fun and familiar activity. Students divide into groups
on opposite sides of the room and proceed to launch paper airplanes back and forth. The planes going from
left to right would represent the forward reaction, while the plane traveling from right to left represent the
reverse. Photos would be taken at regular intervals. Several trials could be run starting with different
numbers of planes on each side of the room. Analysis of the photos would allow the ‘rate’ of the forward
and reverse reactions to be calculated for each photo. We developed an Excel spreadsheet to tabulate and
chart these rates. Ideally, the rates would soon become nearly equal and stay that way until the end of the
trial.
Results:
Unfortunately, the data obtained in this activity was poor. The pictures contained such small numbers of
planes in the air that the calculated rates had a tendency to fluctuate wildly. As a result, the data didn’t
represent a typical system at equilibrium.
Discussion:
We feel that the number of students that would be required in order to produce reasonable data is too large
for this activity to be used in a standard chemistry class. Possibly this activity could be modified in order to
produce reliable and consistent results by combining results from multiple sections of students. On the
positive side, it was noted that even though the data obtained was of poor value, many of the students
gained insight to the concept of equilibrium and were able to accurately describe what ideal results would
have looked like.
Chemical Equilibrium Simulation – This simulation may be used as an inquiry or reinforcement
activity for gas phase equilibrium. Teacher instructions, student worksheet and a sample Excel
spreadsheet are included in the ice cube for this simulation.
Methods:
One of the activities that we developed for our ICE cube uses a chemical equilibrium simulation at
http://www.chem.arizona.edu/~jpollard/fido/fido.html. Using the guide we developed, students adjust the
features of the simulation making predictions, observations, and calculations. Students collect data from the
simulation as they learn about the effects of changing temperature and volume on equilibrium. They also
calculate the equilibrium constant (K) for the different settings. Some of the participants also created Excel
spread sheets to do the calculations and graph data.
Results:
Students learned that the equilibrium constant (K) will change with a temperature change. The data they
collected at really high temperatures gave them a K value of 0, since the reaction went to completion at
really high temperatures. The K values they calculated for changes in volume were very close to each
other, but they were not equal. The expected result was that the K values would be equal.
Discussion:
This simulation and guide are a great visual tool for students to see how stresses on a system at equilibrium
affect equilibrium. The number of students who participated in the activity was 56. Their responses to the
activity were fairly positive. They like to see the changes in the simulation. They were frustrated, as were
the teachers leading the activity, with the K values for the volume changes, but since the values were pretty
close it still seems to be an acceptable activity to reinforce Le Chatelier’s Principle.
©2011 University of Illinois Board of Trustees • http://islcs.ncsa.illinois.edu/copyright
pKa of Acetic Acid from Titration Simulation – This would be recommended as an advanced
chemistry class activity as most introductory chemistry classes do not reach this concept. You may
find that it can be used at the end of chemistry one, or put in with a unit on gases as the simulation is
done in the gas phase. A worksheet for this activity is included in our ice cube.
Methods:
The simulation at
http://www.chem.iastate.edu/group/Grenbowe/sections/projectfolder/flashfiles/stoichiometry/a_b_phitir.ht
ml was used to collect pH and volume of base as a base was titrated into a weak acid. The students then
created an excel graph of their data and determined the Ka which they compared to the accepted value for
the Ka. The simulation also includes a self check for the students, for the calculation of the base used to
neutralize the acid.
Results:
The results of this activity were good. The ability to add one drop at a time or a stream at a time simulated
a real titration. The simulation contained a self-check in which the student calculated the concentration of
their analyte and entered their calculated molarity into the simulation. The simulation indicated whether or
not the molarity was correct. If it was not, the student had to repeat the titration until they were able to
calculate the proper molarity. The students all understood what to look for in obtaining an end point, how
to calculate the unknown molarity, and how to determine the Ka from graphed data by the time they
finished.
Discussion:
A ‘wet lab’ titration done in the lab is an important technique for students to be exposed to, but, the
simulation is a good tool for introducing titration. Doing the simulation also allows for more trials in less
time. The fact that the simulation has a self check for the base concentration forced the students to slow
down so that they didn’t overshoot the endpoint. This is a valuable lesson for students before going to the
lab to do a titration. The self-check also allowed for more accurate analysis of the data. The application of
Ka to the activity is for the advanced high school chemistry class. The application of excel to create the
graph reinforced that excel has many applications in chemistry. This activity was completed by eleven
advanced chemistry students.
Virtual Lab Titration
Methods:
Virtual Lab (http://www.chemcollective.org/vlab/vlab.php) is an applet that was used by the students to
simulate an acid-base titration. Virtual glassware was used, and pH data was collected and plotted,
constructing a plot of pH vs. volume of added base. The resulting titration plots were used to teach the
relationships between Ka values of various acids and the differing shapes of the titration curves and the
method and theory behind calculating the Ka values of the various acids.
Results:
The students performed this lab simulation and then mirrored these simulations on a wet lab, working in
pairs. The students had mixed feelings regarding this activity; the interpretation of the data seemed to be of
some value to them, but didn’t seem to have any advantage over interpreting the wet lab data. The students
were very enthusiastic regarding the mechanics of the simulation; going through the procedure graphically
on the computer helped them understand what they were to do in the wet lab procedure.
Discussion:
Sixteen students participated in this activity; all were successful in both the simulation and the subsequent
wet lab. It would be beneficial to differentiate between the usefulness of the simulation mechanics and the
interpretation of the simulation data so that this would be of more use than a pre-lab discussion.
©2011 University of Illinois Board of Trustees • http://islcs.ncsa.illinois.edu/copyright
Web-Based Animations
Methods:
Web-based animations, simulations and applets were incorporated into class discussions over various
topics. These were used most often when dealing with subject matter that involved the visualization of
particle behavior. Animations from, http://mw.concord.org/modeler/ and
http://iclcs.uiuc.edu/simulations.html were used in a high school chemistry class to help explain the concept
of chemical equilibrium.
Results:
Student response to these animations was very positive. Comprehension of the physical situations was
decidedly easier for the students. This was apparent in their subsequent questions and from the evaluative
comments.
Discussion:
It was found that any kind of particle visualization tool is helpful to the students when dealing with
molecular behaviors. Students thought that the visualizations were helpful enough to be used whenever
possible. They considered some to be more useful than others, but found some benefit in all of them.
Incorporating this type of activity in class discussions should be done regularly. Throughout the school
year, students would refer back to visualizations that were used for various topics in discussing other
topics. For example, students stated that the visualizations used for equilibrium were useful in
understanding other topics discussed in chemistry.
SUMMARY – We believe that the addition of computational tools to the traditional ‘wet lab’ will enhance
the understanding that students gain about equilibrium. Further, we believe that this applies to any topic in
which computational tools can be applied. New simulations and related tools are constantly being added to
the web. Resourceful teachers can select from the abundant supply and integrate them into their classroom
situation.
©2011 University of Illinois Board of Trustees • http://islcs.ncsa.illinois.edu/copyright