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THE EDUCATIONAL VALUE OF CHEMICAL
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IN THE COLLEGE PREP CHEMISTRY CLASSROOM

presented by

KATHERINE E. HAGERMAN

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THE EDUCATIONAL VALUE OF CHEMICAL DEMONSTRATIONS
IN THE COLLEGE PREP CHEMISTRY CLASSROOM

By

Katherine E. Hagerman

A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
MASTERS OF SCIENCE
Physical Science-Interdepartmental

2010

Dr. Merle Heidemann

 

 

 

ABSTRACT
THE EDUCATIONAL VALUE OF CHEMICAL DEMONSTRATIONS
IN THE COLLEGE PREP CHEMISTRY CLASSROOM

Bv

Katherine E. Hagerman
The educational value of chemical demonstrations in a college prep chemistry classroom
was tested to determine whether or not demonstrations merit the required time and
resources. Students were divided into three test groups, each of which used a different
engagement method for the presentation of the demonstrations. One group was given
materials specific to the demonstration to help guide them through the process of
prediction, discussion and application of observations. The second group was given the
same generic worksheet for each demonstration. The third group was not given any
supplemental materials. Assessment data for the three groups was collected from
pretest, posttest and survey questions. The data set was analyzed and compared to a
control group of students who did not see demonstrations. Students who had a higher
level of engagement during the demonstration process performed better than the

control group.

 

ACKNOWLEDGEMENTS

I would like to acknowledge Dr. Merle Heidemann for her flexibility, support and
guidance on this project.

Thank you to my family for their constant support and understanding during the four
years it has taken to complete this program. Thanks to my husband, Chris, and my
children Colin and Evan, for their patience during this project and the summers and

weekends it has consumed. Thank you to my parents and in-laws for their numerous

hours of babysitting and proof-reading.

I also extend my sincere gratitude to my friend, Shanna Tury, who has discussed at

length virtually every aspect of this project. I am very lucky to have such a dear friend
with whom I can discuss anything, especially science.

 

TABLE OF CONTENTS

List of Tables .......................................................................................... v
List of Figures ......................................................................................... vi
Introduction ........................................................................................... 1
Statement of Problem and Rationale ................................... 1
Classroom Demographics ....................................................... 4
Literature Review ..................................................................... 5
Scientific Background .............................................................. 10
Implementation of Unit ....................................................................... 15
The Demonstrations: Gas Laws ............................................ 19
The Demonstrations: lMFs and Phase Changes ................. 26
Results .................................................................................................... 29
Statistical Analysis ................................................................... 42
Conclusion ............................................................................................. 43
Appendices
A. Consent/Assent Form ...................................................... 50
B. Survey ................................................................................ 52
C. Assessments and Rubrics ................................................ 53
D. Demonstration Materials ................................................ 58
E. Results of Assessments and Surveys ............................. 82
Bibliography .......................................................................................... 86

LIST OF TABLES

Table 1. Research Project Demonstrations and Related Chemical Principles ............. 16
Table 2. Demonstration 1 pretest and posttest assessment data ................................ 34
Table 3. Demonstration 1 average scores on daily summary ...................................... 34
Table 4. Demonstration 2 pretest and posttest assessment data ................................ 34
Table 5. Demonstration 3 pretest and posttest assessment data ................................ 35
Table 6. Demonstration 3 average scores on daily summary35
Table 7. Demonstration 4 pretest and posttest assessment data ................................ 36
Table 8. Demonstration 5 pretest and posttest assessment data ................................ 37
Table 9. Demonstration 6 pretest and posttest assessment data ................................ 37
Table 10. Demonstration 7 pretest and posttest assessment data .............................. 38
Table 11. Demonstration 8 pretest and posttest assessment data .............................. 38
Table 12. Demonstration 9 pretest and posttest assessment data .............................. 39

 

LIST OF FIGURES

Figure 1. Graphical comparison of pretest and posttest scores .................................... 32

vi

INTRODUCTION
Statement of Problem and Rationale

A typical high school chemistry teacher uses a variety of techniques to introduce
students to the world of chemistry. Laboratory activities, lecture, discussions and
demonstrations are all typically employed to help students learn chemical concepts.
Chemistry is a unique subject in that it covers phenomena that can be colorful, flashy
and occasionally explosive. Students are expected to test and observe many chemical
relationships in the lab, but not all reactions are appropriate for a laboratory setting.
Safety concerns, cost and limited resources are common reasons a teacher may elect to
present material as a class demonstration rather than as a student laboratory activity.
The goal of this study is to determine if demonstrations are an educationally valuable
instructional tool in a chemistry classroom.

At the end of each school year I have given the students in my college prep
chemistry classes the opportunity to complete an opinion survey after the final exam.
The purpose of the survey was to provide perspective about students’ experiences in
the class over the previous year. The students used any time remaining after the final
exam to complete the survey and were told that the surveys would not be read until
after grades had been finalized. The survey contained questions that asked for opinions
on topics such as teaching style, lab activities, general likes and dislikes and any
improvements or suggestions for future years. Most students gave reasonable, well
thought-out responses that helped me reflect on my teaching that year and consider

new ideas for the future. One question was ”In this class we should do more...” and

students completed the statement indicating which type of activity they would have
liked more of. Students most commonly indicated that they would have liked to have
seen more chemical demonstrations presented to the class.

The number of demonstrations presented in this college prep chemistry has
varied from year to year. Demonstrations were valuable for students to see and
experience, but were not my first priority in planning lessons and activities. I treated
them as something extra when time and resources allowed.

Increasing the number of chemical demonstrations presented to my classes was
not a simple task and there were many factors to consider. Most of the chemical
demonstrations I had been using required some preparation time. Many included
chemical reactions that necessitated making solutions, weighting reagents and
preparing the necessary equipment for multiple presentations. Demonstrations often
required the use of consumable chemical resources and therefore added extra expense.
Demonstrations also had many safety considerations. They could only be performed
after having been practiced and while following all of the necessary safety precautions.

The 2006 revisions to the Michigan High School Content Expectation increased
the amount of required content and therefore decreased the available class time for
demonstrations and other similar activities. After considering the survey responses,
increasing the number of demonstrations presented to my classes was warranted, but
the time and money constraints of doing so needed to be taken into account.

This led to a desire to evaluate the educational value of chemical

demonstrations. I suspected that students wanted to see more demonstrations

 

because they liked to be entertained. They wanted to see something on fire or change
color in an unexpected way. They were drawn to the entertainment aspect of
demonstrations, but were not really focused on the relevant chemical content to which
it was related. I needed to determine if there was a way to incorporate chemical
demonstrations into my curriculum that did not require additional class time and remain
content oriented. Could demonstrations be used as effectively and efficiently for
teaching students the required content as lecture and practice?

In the summer of 2009, I began developing demonstrations, assessments and
surveys that could be used to measure the educational value of demonstrations in the
college prep chemistry classroom. I developed lessons and worksheets to accompany
the demonstrations to try to make them more of an educational tool rather than just a
source of entertainment for students. I hypothesized that if students were required to
make predictions, discuss, think critically and perform data analysis as part of the
demonstration process, then demonstrations could be a better, educationally useful
tool. If the data collected showed that chemical demonstrations impact student
learning in chemistry and provide more than just entertainment value, than the extra

time and expense they require would be justified.

 

CLASSROOM DEMOGRAPHICS

This research project was implemented at Hartland high school during the 2009-
2010 school year. Hartland High School is located in rural/suburban Livingston County,
Michigan near the intersection of US-23 and M59. The school contains approximately
2000 students in grades 9-12.

College Prep Chemistry is the third year science course for most students,
following completion of earth science and biology. Completion of a chemistry or physics
course is required for Michigan Merit Credit and for graduation. College Prep is the
higher level of the two first-year chemistry courses available at Hartland High School.
The majority of students enrolled in College Prep Chemistry are juniors, with a few
sophomores who tested out of a previous science course or doubled-up on science
classes. A small number of seniors take College Prep Chemistry after having taken
physics or anatomy as a junior.

During the 2009-2010 school year, ten sections of college prep chemistry were
taught, three of which were included in this study. Hartland High School uses a
traditional six hour per day schedule. Each section met once per day for approximately
55 minutes. Each section had a total of thirty-one students. Of the 93 college prep

t“ -6"‘ hour sections used in the study, 56 consented to

students enrolled in the 4
participate. 25 students were from 4th hour, 13 were from 5th hour and 18 were from

6th hour. Of the 56 participating students, 13 were sophomores, 39 were juniors and 4

were seniors. Thirty-eight of the participating students were female and 17 were male.

 

LITERATURE REVIEW

Presenting chemical demonstrations is a standard activity for many chemistry
teachers. Each year at the Michigan Science Teachers’ Association annual conference
numerous sessions are devoted to chemical demonstrations new and old. When asking
former chemistry students what they remember from their time in chemistry class,
many will recount a favorite demonstration they saw that has remained in their memory
for years afterward, but not the related chemical explanation. Television programs such
as The Late Show with David Letterman will often include a segment of chemical
demonstrations presented by high school chemistry teachers. Chemical demonstrations
have the power to show people the flashy, colorful, explosive and unexpected nature of
chemical reactions not normally seen.

The state of secondary education in Michigan has changed significantly in the
past few years, possibly affecting the role of classroom demonstrations. The 2006 High
School Content Expectations for chemistry were expanded to cover substantially more
material than in previous years in the same or less amount of time. In addition,
Michigan’s poor economy has led to a decrease in funding provided to most schools.
These conditions have caused chemistry teachers to re-evaluate and prioritize the
content of their classes, including demonstrations. Do demonstrations in chemistry
classes have enough educational value to be considered worth the extra preparation
time and cost, compared to other teacher-led activities?

In ’Demonstrations as a Teaching Tool in Chemistry: Pros and Cons’, Beall (1996)

summarized the comments of educators who felt that chemical demonstrations were

not worth the time they required and provided only entertainment rather than
education. This position was confirmed in the research of Pohl (2005) who found that
demonstrations were the least helpful instructional method used in his classroom. He
stated “much of the class put away their learning for ”the show” and were not actually
thinking about what they were learning.”

Others see chemical demonstrations as a means of generating excitement for
chemistry. Comancho—Zapata (1997) found that students reported being more
interested in science after a series of demonstrations was added to the science
curriculum. In his explanation of lecture demonstrations as ”exocharmic” or charm
generating, Bodner (2001) wrote that the curiosity stimulated by seeing demonstrations
can lead students to investigate the science behind them. _

Although demonstrations can stimulate curiosity, the role of a chemistry teacher
is to educate students, not just to entertain them. Bodner (2001) added that even
though students may be charmed by a demonstration, that does not guarantee they
have learned anything from it. In his master’s thesis research, Pohl (2005) found
students indicating in surveys that they felt demonstrations were the best learning
activity, but his assessment data showed that it was the least helpful. Although his
students enjoyed the entertainment, or charm of a demonstration, that was not enough
to generate long-term understanding or retention of the concepts. Crouch, et.al (2004)
found that traditionally presented demonstrations, where students sit as passive
observers and hear the instructor’ 5 explanation, are ineffective at teaching students the

scientific concepts.

To be effective, a demonstration should not be a stand-alone, passive activity. In
an explanation of why he presented demonstrations, Shakhashiri (1984) wrote, ”To
approach demonstrations simply as chances to show off dramatic chemical changes or
only to impress students with the ”magic” of chemistry is to fail to appreciate the
opportunity they provide to teach scientific concepts and descriptive properties of
chemical systems.”

Tanis (1984) agreed with the idea that demonstrations are best used as a starting
point for discussion and inquiry. Roadtruck (1993) cautioned teachers that
demonstrations must include student interaction to be considered educationally
relevant. He classified demonstrations as only a stepping off point for effective
instruction.

Many chemical educators agree that the methods used for presenting
demonstrations are as important as the demonstrations themselves. Roadtruck stated
that the demonstrator must require students to question, predict, explain and test as
part of the demonstration process. O’Brien (1991) wrote that “Teacher instruction
without student construction has been characterized as words transferred from the
lecturer’ 5 notes to the students’ notebooks without passing through the minds of
either.”

In a collection of thoughts about chemical education, Bent (1980) reminded
teachers that it is important to begin a demonstration not by saying ”Now I will show
you...” but rather ”Let’s see what happens when...” in order to stimulate learning. In

research survey data from six thousand physics students, Hake (1998) found that

students performed best when actively engaged in the discovery of the concepts
through a demonstration as opposed to more passive instructional methods.

Demonstrations can be a useful tool for confronting students’ misconceptions if
the students are an interactive part of the process. Zimrot and Ashkenazai (2007)
developed an instructional model to measure the effectiveness of lecture
demonstrations at targeting specific student misconceptions in chemistry. The model
they employed required students to make predictions about the results of a
demonstration before seeing it. After recording observations, students discussed the
outcome with a classmate and made predictions about a second, similar demonstration.
The data showed that students were better able to confront and replace
misconceptions with the correct chemical explanations after engaging in this process of
prediction and discussion. Students who were not actively engaged performed about as
well on assessments as those who did not see the demonstrations at all. Similar results
were obtained by Ashkenazi and Weaver (2007) when studying lecture demonstrations
used to teach the concept of solvent miscibility. Demonstrations were developed to
help students differentiate seemingly similar but fundamentally different chemical
concepts. The authors concluded that an interactive discussion method is necessary in
order for students to refine their scientific knowledge enough to disregard
misconceptions and apply the correct explanations.

Crouch et al. (2004) also assert that the method by which a demonstration is
presented determines its effectiveness. For their research, they presented lecture

demonstrations in two modes; 1) observe and 2) predict and discuss. The results were

compared to a control group of students who didn’t see the demonstrations. Students
who were required to predict and discuss events performed better on assessments and
had better long-term retention of knowledge than those who passively observed the
demonstrations.

This literature review shows that demonstrations have more than just
entertainment value for students. Demonstrations can increase learning if students are
an interactive, rather than just passive, part of the demonstration process. Students
who are required to observe, predict and discuss their observations will have a better
understanding of the concepts than student who just watch passively. To provide the
best instruction, demonstrators must develop materials to include interaction as a part

of the demonstration process.

 

SCIENTIFIC BACKGROUND

This research project was conducted over the course of two units of study during
the second semester of college prep chemistry. The units covered the properties of
gases and the gas laws, intermolecular forces and phase changes. Each of these topics
has a variety of well known demonstrations and the underlying chemical concepts of
each can easily be qualitatively and quantitatively observed.

The properties of the particles in a sample of gas are described by the
assumptions of Kinetic Molecular Theory (KMT). KMT makes the assumption that gas
particles are in constant, random motion. This means that, except at very low
temperatures or very high pressures, gas particles in a sample will move apart to fill
their entire container equally. This causes gas particles tohave a much lower density
and a higher compressibility than a liquid or solid form of the same material.

KMT also assumes that the average motion (kinetic energy) of the particles
depends on the temperature of the gas. As the temperature of a gas sample is
increased, the particles will move faster and the average kinetic energy will increase. In
addition, KMT assumes that kinetic energy is not lost when particles of a gas collide.
Energy can be transferred between particles but there is no net gain or loss.

Gas particles are also assumed to have no forces of attraction between them.
This means that they will easily glide past one another with a fluid motion similar to
those in a liquid.

The Gas Laws are a compilation of the mathematical relationships between the

variables of temperature, pressure, volume and number of particles in a sample of a gas.

10

 

The Gas Laws are used to predict and calculate the way one variable will change in
response to the change of another. The Gas Laws can be used to describe many real-
world observations of gas samples.

Boyle’s Law compares the relationship between the pressure and volume of a
gas sample at constant temperature. The law states that as pressure is increased
volume is decreased and mathematically there is an inverse relationship between the
two variables. Boyle’s Law is often experienced during a change in altitude in an
airplane. As the altitude of the plane increases the atmospheric pressure will
decreases. As a result, the gas particles in the ear spaces move apart and create a
sensation of discomfort until the inner and outer pressure is again equalized.

Charles’ Law describes the direct relationship between volume and temperature
of a gas sample at a constant pressure. If temperature is increased, volume will
increase. This can be observed by studying a hot air balloon. As the air particles inside
the balloon are heated, their total volume increases, according to Charles’ Law. An
increase in volume causes a decrease in density and the warmer particles inside the
balloon become less dense than the cooler particles outside and the balloon rises.

Gay-Lussac’s Law explains that a direct relationship exists between pressure and
temperature when the volume of a gas is held constant. As temperature increases, so
will pressure. This explains why sealed aerosol cans have strict temperature
requirements and become very dangerous at high temperatures.

Graham’s Law of Effusion describes the behavior of gas particles as they move

through small holes or pores. In general, the rate of gas effusion depends on particle

11

mass. Heavier particles will effuse more slowly. Graham’s Law explains why a balloon
filled with helium will deflate faster than one filled with air. Helium particles are less
massive and therefore effuse from the balloon at a faster rate.

One way to produce gas particles is by generating them in a chemical reaction.
The Law of Conservation of Mass explains that the amount of reactants converted in the
reaction will dictate the amount of products produced in the reaction. A balanced
chemical equation is used to show the mathematical relationship between the amount
of particles (in males) of reactants and the amount of particles of products. If the
amounts of reactants present do not correspond to the ratio given in the balanced
equation, the reaction will only continue until one of the reactants is fully converted.
The reactant that is consumed first is known as the limiting reactant and it can be used
to calculate the amount of gas produced.

The conditions at which a substance becomes a gas are dependent on its
intermolecular forces (lMFs). IMFs are the attractions that are present between the
molecules within a substance and are a result of the arrangement of electrons within
each molecule. Molecules that have a symmetrical electron arrangement have no
polarity because the electron charge is spread evenly around the molecule. Because of
the even charge distribution there is very little attraction from one nonpolar molecule to
another.

Molecules with an uneven electron arrangement are considered polar, having
regions of overall negative charge and regions of overall positive charge. The positive

region of one molecule attracts the negative region of another molecule, producing an

12

intermolecular force of attraction. A greater force of attraction between molecules is
indicative of a greater molecular polarity.

lMFs are classified into three main types. The weakest type of IMF is known as
London Dispersion Forces. When two molecules move close to each other, they can
cause a change in electron arrangement. The electrons in one molecule repel the
electrons in the other, inducing a temporary polarity. The slight increase in polarity is
enough to cause an attraction between molecules. The more electrons within the
molecule, the greater the increase in polarity and the stronger London Dispersion
Forces.

Molecules that are polar have a stronger IMF known as dipole-dipole attractions.
Dipole-dipole forces are the permanent attraction between molecules that have an
asymmetrical electron arrangement. When the molecules contain a hydrogen atom
bonded to an oxygen, nitrogen or fluorine atom the polarity of the electrons in the
molecule increases and so does the strength of the IMFs. This strongest type of IMF is
known as hydrogen bonding.

The strength of intermolecular forces is responsible for the amount of energy
required for a phase change. The greater the forces of attraction between molecules,

the more energy that is required to separate them. Molecules that contain hydrogen

bonding, such as water (H20), will have a higher boiling point than a molecule with only

London Dispersion forces such as methane (CH4). Water will also have a higher freezing

point and a slower rate of evaporation. By comparing the size and shape of molecules,

13

predictions can be made about the relative strengths of the intermolecular forces
between them and thus the amount of energy required for a phase change.

In addition to IMFs and temperature, phase changes can also be affected by
changes in pressure. A phase diagram shows the relationship between temperature,
pressure and phase for a substance. For a given substance, the state of matter is
dependent on both temperature and pressure. For example, at 25°C and 1 atm (room
conditions) water is a liquid. Water can be converted a vapor by an increase in
temperature, a decrease in pressure, or a combination of the two. Any point on the line
between liquid and vapor on a phase diagram is considered a boiling point. The point
on the line at 1 atm is considered the normal boiling point because it corresponds to the
atmospheric pressure present at sea level.

The Michigan High School Content Expectation P4p1 requires that students be
able to state the properties and arrangement of gas particles and how they differ from
the particles in a liquid or a solid. Students are also required to understand the
mathematical relationship between variables of pressure, temperature, volume and
number of particles for a sample of a gas for standard C4.5x. Expectation C43 and C45
require that chemistry students learn intermolecular forces and how they relate to
phase changes. In addition, students should use molecule size and polarity to predict

the relative boiling points for a given set of molecules.

14

IMPLEMENTATION OF PROJECT

The purpose of this study was to test the educational value of chemical
demonstrations in a college prep chemistry classroom. I chose this project to see
whether or not demonstrations impact student understanding of the chemical concepts
or rather, if they simply provide excitement or entertainment for the students. My
initial prediction was that students must be engaged in the demonstration process by
making predictions, recording observations and discussing results in order to learn
chemical concepts from the demonstrations. My previous experience with presenting
chemistry demonstrations was that students would sit back and watch the show, not
realizing that I expected demonstrations to be another method of teaching the
concepts. I also found that students would perform poorly on assessment questions
related to the specific demonstrations, which illustrated to me that the demonstration
process was not really an educational one.

To test my hypothesis, I began the project by surveying students to discover
their perceptions about chemical demonstrations in the classroom. The survey
questions (Appendix B) asked students whether they felt demonstrations were
important in a chemistry classroom and what purpose they served. I also asked
students how helpful they thought demonstrations were for learning as compared to
lecture, labs, homework and textbook reading. Finally, I gave students different
examples of types of demonstrations that can be done and asked their opinions about

when each type should be used.

15

 

A set of demonstrations was developed to be presented to students over the
course of two units of study. The demonstrations related to the topics of the gas laws,
intermolecular forces and phase changes. I chose demonstrations that I knew to be
reliable for classroom presentations as well as new ones that related to the relevant
chemical concepts. I organized a set of about twelve demonstrations, nine of which
(Table 1) were included in the final project data (Appendix D).

Table 1. Research Project Demonstrations and Related Chemical Principles

 

 

 

Demonstration Objectives and Chemical Principles
1) Limiting Reactant & The limiting reactant will determine the amount
Carbon Dioxide of product formed in a reaction. Gas volume
Production can be used as a measurement of the amount of
product formed.
2) Properties of Gases Gases exhibit the physical properties of mass,

fluidity and compressibility.

The force of atmospheric pressure is equivalent
to 14.7 psi at sea level.

3) PVT Relationships A sample of gas particles exhibits a
mathematical relationship between the variables
of pressure, temperature and volume.

 

The PVT relationships can be related to many
real world situations involving gases.

 

 

 

 

4) Graham’s Law of The rate of effusion is dependent on the
Effusion molecular mass of the gas.
5) Hot Air Balloons A temperature increase results in a density
decrease for a gas sample.
6) Gas Densifl Gas density is dependent on molar mass.
7) Gas Stoichiometry The volume, temperature and pressure of a gas

produced in a chemical reaction can be used to
calculate the amount of the limiting reactant
used in the reaction.

8) Rate of Evaporation The rate of evaporation for a sample of gas
particles is dependent on the strength of the
intermolecular forces.

9) Phase Diagrams Phase changes can occur as a result of both
changes in temperature and pressure.

 

 

 

 

 

 

16

 

I developed and administered a pretest (Appendix C) over the chemical
principles I planned to demonstrate in class. The pretest questions were designed to
test student understanding of the concepts, rather than the specific procedural details
of the demonstrations themselves. Most of the questions were multiple choice format,
but also included were some short answer questions, calculation based questions and
questions where students were expected to draw molecular diagrams to illustrate
concepts.

To test the project hypothesis, I set up three methods for presenting
demonstrations in class. The first method required students to complete a specific,
guided worksheet for their data and observations as the demonstrations were
presented. A specific worksheet was developed for each demonstration that required
students to make predictions, record observations, draw diagrams and summarize the
demonstrations and its related chemical concepts. This group is referred to as the SW
group for the project.

In the second method, students were given a generic demonstration sheet
(Appendix D) that asked them to record observations and summarize the demonstration
and its concepts. The same generic worksheet was used for each demonstration. This
group is referred to as the GW group for the project.

For the third method, students were not given any additional materials or
guidance during the demonstrations. At the end of each hour, students were required
to complete a short summary (Appendix D) of the demo and its concepts. The purpose

of the summary was to have some data for day to day comparisons between the three

17

 

different methods of engaging students in demonstrations. Students in this group are
referred to as the NW group for the project.

The demonstrations were presented to my 4‘", 5th and 6th hours. In order to try
to eliminate the normal variations in performance between classes, a plan was
established so that each class would use each of the three methods in rotation. For
example, 4th hour got the specific work sheet for the first demonstration, the generic
sheet for the second and no worksheet for the third. Therefore, all students
participated in each demonstration method for the project. All students were told at
the beginning of the project that they could take extra notes if they desired and that any

of the demonstration results and concepts were subject to appear on tests and quizzes.

18

 

THE DEMONSTRATIONS: Gas Laws

The first seven demonstrations for this project related to the content studied
during the Gas Laws Unit. The demonstrations were chosen to help students
understand the relationship between the variables of temperature, pressure, volume
and number of particles in a sample of gas particles.

1) The first demonstration for the project was related to carbon dioxide
production and the concept of a limiting reactant. Students were presented with four
flasks, each filled with an equal amount of vinegar. For the demonstration, the baking
soda was emptied from the first balloon and students observed the carbon dioxide
production and the resulting diameter of the balloon. Students in the SW method group
were asked to record predictions about the size of the balloons for the next three flasks.
The second balloon had double the diameter of the first and the third balloon had
double the diameter of the second as expected. Many students predicted the fourth
balloon would double in volume again because the baking soda was again doubled, but
the diameter was the same as the third balloon.

At first, students were disappointed, expecting a giant balloon for the fourth
flask; then, not getting one led them to believe something had gone wrong. They were
instructed to look more closely at the flask for any evidence that could explain what had
happened. They noticed that the fourth flask contained excess baking soda and the
other three did not. At this point students were instructed to write a balanced equation
for the reaction and generate a chart of the mole values to look for any patterns. After

completing the chart students were able to see that the fourth balloon did not contain

19

 

any more carbon dioxide that the third balloon because vinegar had become the limiting
reactant.

This demonstration served as both a review of stoichiometry and an introduction
to the study of gases. Students were to realize that gases are still subject to the
mathematical relationships in stoichiometry and that the amount of gas particles
produced is related to the amount of reactants, just like a solid precipitate would be.

2) The second set of demonstrations covered Kinetic Molecular Theory and
properties of gases. A series of six short demonstrations was adapted to Illustrate mass,
density, fluidity, compressibility and the force of air pressure. Gas particle mass was
demonstrated by using a microgram balance to find the mass of an empty syringe, a
syringe filled with air and a syringe filled with an equal volume of water. Students then
used the data to calculate the densities and the number of molecules (assuming air is
mostly nitrogen gas) of both the air and water samples.

To test compressibility, pressure was applied to the water and air filled syringes
and the volume changes were noted for each. The syringes were passed around the
classroom for students to observe for themselves.

To illustrate fluidity, a burning candle was placed on the demonstration table
and quickly extinguished with a puff of air from a two liter plastic bottle. The candle was
relit and moved about two meters away. It was easily extinguished again at the greater
distance. The purpose of this demonstration was to show that air particles are fluid and

will move past one another easily, similar to the way liquid particles do.

20

 

A set of three demonstrations was presented to show the force of atmospheric
pressure. The goal was to illustrate for students the relative force of atmospheric
pressure at sea level (1 atm or 14.7 psi). Given a choice of a ping pong ball, basketball,
beach ball or bowling ball sitting on a table, students in the specific worksheet group
were asked to predict which most closely presses on the table with a force equivalent to
that of the force of atmospheric pressure. Next, a meter stick was placed on a lab table
with 50 cm on the lab and 50 cm sticking off the side. A piece of poster board was
placed over the half of the meter stick on the bench. A volunteer student hit the
uncovered end of the ruler, easily breaking it in half. Students expected that hitting the
ruler would cause the poster board to catapult into the air, but rather, the air pressing
on the surface of the poster board was enough to hold it down and break the ruler
instead. We then measure the surface area of the poster board and calculated the air
pressure that was pushing down on it.

For the second part of the air pressure demonstration an aluminum pop can was
filled with a few milliliters of water and put it on a hotplate. When the water was
boiling and the can was sufficiently filled with vapor it was inverted it into a container of
ice water. The change in temperature caused the vapor in the can to condense. With
few gas particles remaining inside the can the force of atmospheric pressure easily
crushed it in less than 1 second.

The final demonstration of the day used the force of atmospheric pressure to
inflate a balloon inside a flask. Similar to the pop can, a small amount of water was

placed in an Erlenmeyer flask and heated to boiling. When the flask was sufficiently

21

filled with vapor an empty balloon was placed over the opening. As expected, the
balloon started to inflate with water vapor. Next, it was. removed from the heat. As the
water cooled and condensed the balloon deflated and then reinflated inside-out on the
inside of the flask.

Students in the SW group were required to draw diagrams illustrating the gas
particles in both the pop can and the balloon demonstrations. Most students expected
the can to crush but did not understand why. Also, students expected the balloon to
deflate, but were surprised to see it reinflate inside the flask. By having students draw
the water molecules in each stage of the demonstrations I expected them think through
each process and realize that the force of gas particles in the atmosphere is quite
significant.

3) The third day of demonstrations illustrated pressure, volume and
temperature relationships as described in Boyle’s, Charles’ and Gay-Lussac’s Gas Laws.
Relatively simple demonstrations were chosen so that students would not get confused
with more complex procedural details. To illustrate the relationship between pressure
and volume, a marshmallow Peep was placed in a flask which was connected to a
vacuum pump. As the flask was evacuated, the volume of the Peep increased.

As a second pressure/volume demonstration a Cartesian diver was set up in a
sealed two Liter bottle of water. The diver started out at the top of the water and as the
bottle was squeezed the diver sank to the bottom. When the pressure was released the

diver rose back to the top.

22

To demonstrate the relationship between temperature and volume, three
balloons were inflated to equal volume. One was placed one in hot water and one in
liquid nitrogen, leaving the third as a control. The warmer balloon expanded and the
liquid nitrogen balloon decreased in volume significantly.

The relationship between pressure and temperature was demonstrated by
placing a LCD temperature strip inside a plastic bottle. The bottle cap was altered so
that it had a tire valve stem inserted through a hole drilled in the center. A tire pump
with a pressure gage was used to add air to the bottle. Students monitored the
pressure and temperature changes as air was added to the bottle over the course of two
to three minutes. As the pressure in the bottle increased, so did the temperature
reading on the LCD strip.

Students assigned to the SW method group were asked to make predictions
before each demonstration. Some were easy, such as knowing that a balloon in hot
water will expand, but few predicted that the Cartesian diver would sink when the
bottle was squeezed. The SW students were also asked to relate each demonstration to
a real-world example, such as SCUBA diving or changes in car tire pressures.

4) Demonstrations on the fourth day related to Graham’s Law and effusion. To
demonstrate the general concept of effusion, balloons containing vanilla, strawberry
and peppermint extracts were passed around the classroom. Students noticed that
each of the balloons had an odor and after more careful observations were able to
detect the separate scents. They were told that extracts had been placed inside each

balloon and asked how they were able to detect them outside the balloon.

23

To illustrate Graham’s Law and rate of effusion, one balloon was filled with air
and another with an equal volume of helium. For the next two days students observed
the relative diameters of the balloon to compare the rates of effusion of the two gases.
The helium balloon decreased in volume much faster than the air filled balloon.

Students in the SW group were required to describe effusion based on their
balloon observations. Students also had to predict rates of effusion and then perform
the Graham’s law calculations to support their observations.

5) The fifth day of demonstrations related to gas density. A mylar balloon
partially filled with helium was heated with a hair dryer. As the temperature increased
the volume of the gas also increased, as explained by Charles’ Law. As the volume
increased, the density decreased and the hot helium balloon floated to the ceiling. As it
cooled, it sank back down and the process was repeated. It was also explained to
students that although the principles are the same, the demonstration set-up was not
an exact replica of a hot air balloon, but sometimes alterations are necessary to make
thing work easily at a different scale.

6) The concept that different types of gases have different densities was the
basis for the next demonstration. Of course, students know that a helium balloon will
float and an air-filled balloon will not; however, they are not able to explain why or
predict what other gases will do. Soap bubbles filled with methane were compared to
soap bubbles filled with carbon dioxide. The methane bubbles rose to the ceiling and

the carbon dioxide bubbles sank to the floor.

24

Students in the SW group were required to make predictions about whether the
gases would sink or float. After recording their observations they performed Charles’
Law and density calculations to support their data.

7) The last of the gas law demonstrations related back to chemical reactions and
stoichiometry. A piece of magnesium ribbon was reacted with hydrochloric acid to
produce hydrogen gas. The gas was collected in a graduated cylinder via water
displacement and the volume of hydrogen gas formed was measured. Students used
the data to calculate the original mass of the magnesium metal used in the reaction.

SW students were asked to predict what would happen in the demonstration
and what the data could be used to find. They also discussed other variables that could
be solved for, such as gas density. In addition, students had to predict how an error in
the temperature or pressure data would affect the mass result and prove their
prediction with more calculations.

At this point in the project, the study of gases was finished. Students completed
the unit assessment which included the same questions that were given on the pretest.
In order to expose each class to the different research methods an equal number of
times, two more demonstrations were presented during the next unit, for a total of nine

demonstrations.

25

THE DEMONSTRATIONS: Intermolecular Forces and Phase Changes

The second unit of study included in the project related to the concepts of
intermolecular forces and phase changes. A pretest with questions about concepts I
expected to demonstrate in class was developed and administered.

8) The first demonstration for the second unit showed the relationship between
rate of evaporation and intermolecular forces. As the demonstration took place, I
explained to the class that evaporation is an endothermic process and that a greater
temperature decrease indicates a faster rate of evaporation. The process was repeated
and data were collected for six different organic compounds. Students were then able
to make correlations between the properties of the molecule, the types of
intermolecular forces and the rate of evaporation.

Students in the SW group for this demonstration had to make predictions about
the relative temperature changes for the molecules before each was tested. They had
to support their predictions with reasoning that included structural characteristics and

intermolecular forces. At first students simply relied on IMF type as a predictor of

evaporation rate, but the final trial compared methanol (CH30H) with hexane (C5H14).

Methanol molecules form the stronger hydrogen bonds between them whereas hexane
molecules have only London Dispersion forces of attraction. Most students predicted
hexane would evaporate faster but in fact it was the slowest of all the molecules used.
This lead students to go back and reexamine their data to see what other variables
could be considered. They discovered that the strength of IMFs is also dependant on

the total number of electrons. Although London forces are overall a weaker attraction

26

than hydrogen bonds, hexane has many more electrons and thus can form attractions
stronger than the single hydrogen bond in methanol. Students also had to graph their
data and make predictions about evaporation rates for other similar molecules.

9) The final demonstration for this project illustrated phase diagrams and how
phase is dependent on both temperature and pressure conditions. This topic was
chosen for a demonstration because students’ everyday experience with phase changes
are mostly with water at roughly 1 atm of pressure. Students often use water as a

frame of reference that can lead to many misconceptions, for example assuming that for

something to be frozen it must be colder than 0°C.

For the first part of the demonstration a five gallon glass bottle was filled with
water. Students were asked to predict how long it would take for the water to boil. The
bottle was connected to the vacuum pump and the air was evacuated from the
container. With the decrease in vapor pressure the water began to boil in less than one
minute. Based on the observations, the class examined phase diagrams and plotted the
initial and final pressure and temperature values for the water and its corresponding
phase change.

For the second part of the demonstration students compressed butane filled
syringes until condensation occurred. Students also examined a phase diagram for
butane and examined the related points from the demonstration.

The final demonstration for phase diagrams started with solid iodine added to a
beaker, covered with a watch glass and gently warmed on a hot plate. SW students

made predictions about what would happen to the iodine, most predicting it would

27

melt. However, at atmospheric pressure iodine will undergo sublimation, changing
directly from a solid to a purple vapor. This led students to want to examine the phase
diagram to see that in fact pure iodine does not exist as a liquid at 1 atm.

Students in the GW and NW study groups were shown all the same
demonstrations as the SW group, but were not asked to make predictions or discuss
results. They viewed the game graphs and calculations but were not required to do
them on their own. Some students took notes for themselves and others chose to only
watch the demonstrations instead. All groups were required to summarize the
demonstrations and the related concepts at the end of each hour. For each
demonstration all of the worksheets were collected and copied for research purposes.
The originals were returned to the students to be used for test preparation. At the end
of the study, another unit assessment was administered for IMFs and phase changes
and included the items given on the pretest. Students were also asked to write a
summary of how beneficial the demonstrations were for helping them learn and

remember the chemical concepts.

28

RESULTS

The goal of this project was to test the educational value of demonstrations in
the chemistry classroom. Further, I wanted to investigate whether students who were
more involved in the demonstration process performed better on assessments than
those who were more passive observers. To test these hypotheses, I collected and
compared pretest and posttest data from questions relating to concepts presented in
the demonstrations. Students were also surveyed on their opinions about the role of
demonstrations in the classroom. Daily summaries were collected from all students as a
day to day comparison of the effect of demonstrations on student learning.

For each demonstration, students were initially divided into three groups, SW
GW and NW as described in the Implementation of Project section. After the data were
collected a fourth analysis group was added to serve as an ad hoc control.

During the six weeks of data collection, a significant number of students were
absent for one or more of the nine demonstrations used in the project. Most were
absent for school related reasons and a different set of students were absent for each
demonstration. The number absent ranged from four to fifteen.

Absent students still learned the related material but did not actually see the
demonstrations in class and were not given a make-up opportunity. Pretest and
posttest data scores for absent students were separated into a fourth group for
comparison with the other three demonstration methods.

Before seeing any of the project demonstrations students were surveyed about

the role of demonstrations in chemistry and how they should be included (Appendix B).

29

97.7% of students responded that it is important for demonstrations to be included in
chemistry class. When questioned about the purpose of demonstrations, 77.9% felt the
purpose should be to learn about concepts, 20.9% felt the purpose of demonstrations is
to generate excitement about chemistry and the remaining 2.2% felt demonstrations
should be for entertainment only.

The final survey question described four different types of demonstrations that
are typically done in chemistry: demonstrations to provide entertainment only,
demonstrations to illustrate a chemical concept, demonstrations to provide data and
observations for analysis, or demonstrations to introduce a lab or activity. 50% of
students indicated that they most preferred demonstrations that illustrate a concept in
class. 29.1% of students preferred demonstrations for entertainment and the remaining
20% of students were divided between demonstrations with a worksheet and
demonstrations to introduce an activity.

A majority of students viewed demonstrations with a worksheet or those related
to the concepts as being the best for learning the material and the most helpful for
answering test questions. When responding about entertainment demonstrations, no
students considered them most helpful for learning or answering test questions but
62.8% of students classified them as the most memorable.

Overall, the survey data showed that students like demonstrations and feel they
are important to learning chemistry. They also showed that students would prefer to
learn from demonstrations that are flashy and entertaining as well as educational.

Although students indicated they would like the learning process to be entertaining, the

30

survey results show that they also realize that activities done in class should be ones
that address the concepts and prepare them to be successful on assessments.

Data from the pretest and posttest scores were analyzed for evidence of the
effectiveness of demonstrations on learning in general and also for improvements
between the SW, GW, NW and Control groups. Each of the nine demonstrations used in
the project had one or more questions about its content on the pretest. The same
questions were used again on the posttest. The data were evaluated for improvement
in the percentage of total points earned from the pretest to the posttest for each of the
four analysis groups. A t-test was then used to evaluate the percentage increase data
between each pair of analysis groups for statistical significance.

Overall, students who saw demonstrations in class had a larger improvement on
posttest scores than students who were absent for the demonstrations (Fig.1). Over the
course of the study the average improvement from pre to posttest for the control group
was 17.96%. The average improvement for students who saw demonstrations of any
method was 32.14%. This shows that students who saw the demonstrations performed
much better than students who were absent. Student comments at the end of the
project also supported this finding. Many students commented that while taking the
unit assessment they felt they were able to remember what they saw in the
demonstrations and use that to help them answer the questions.

To test the effectiveness of the three demonstration methods employed for the
project, the student pretest and posttest scores were separated by method. The total

percentage of points earned on the pretest and posttest were calculated as well as an

31

improvement (Fig. 1). The specific worksheet method group earned 36.6% of points
possible on the pretest and 66.3% of points possible on the post test for an overall
improvement of 30.0%. The generic worksheet method group earned 33.3% of possible
points on the pretest and 66.8% of possible points on the post test for an improvement
of 33.5%. The No Worksheet method earned 34.6 % of the points on the pretest and

67.5% of possible points on the posttest for an improvement of 32.9%

 

 

so r—m—h— —_--—--—-~-———.

 

70 L.._-,. -1 7.--. -1 _.- _ 11_#____-_# . . _

so ,__‘_-,__,c.--_ .. _--,--.--__, _.__-____ __.___..._

 

 

 

so l_______ J \1_~W _, 7 77”“ ’ ‘,,_.,--_ _, __- _" f' __ GP :_ I”

40
30
20
10

 

 

Control SW GW NW Combined

I Pretest % Posttest % I Improvement %

 

Figure 1. Graphical comparison of pretest and posttest scores by type of
worksheet as compared to the control group. Combined data is for all students
that saw demonstrations.

 

 

 

A comparison of just the pretest and posttest showed that there is not a real
difference between demonstration methodologies. All three groups had about the
same pretest and posttest scores. Although the overall data indicated that

demonstrations are beneficial to student understanding, they do not support my

32

hypothesis that the engagement method by which demonstrations were presented
affected student performance.

In order to determine if there were differences between the methodologies of
student engagement, the data set for the individual demonstrations and questions was
examined. For the nine demonstrations used in the study, the specific improvement
method group showed the greatest improvement for five of the demonstrations and the
generic and no worksheet groups each had the greatest improvement for two of the
demonstrations. Examining the data for the individual demonstrations shows that there
may, in fact, be a benefit for students who are given a specific, guided approach to
classroom demonstrations. The data set was evaluated to see the effect of the three
modes of engagement on student learning for each demonstration. The pretest and
posttest scores were evaluated for improvement and compared to the control group
improvement. For some of the demonstrations, additional analysis of the daily
summaries was done to see the short term effects of the three engagement methods.

For the first demonstration, Limiting Reactants and Carbon Dioxide Production,
students were required to turn in a summary of the demonstration and its related
chemical concepts. The summaries were scored according to a three point rubric.

Three points were awarded for students who correctly explained the limiting reactant
and how it related to the amount of gas in each balloon. Two points were earned for
mentioning the limiting reactant concept but not applying it to the specific results.

Students who simply summarized the procedure earned one point.

33

Table 2. Demonstration 1: Limiting Reactants and Carbon Dioxide Production pretest and
posttest assessment data by engagement method

Control % SW % GW % NW %

Pre Post Increase Pre Post Increase Pre Post Increase Pre Post Increase

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

45 45 0 57 69 12 58 72 14 72 79 8

 

Table 3. Demonstration 1: Average scores on daily summary out of three possible points.

SW GW NW
Daily Summary Average Score , 2.5 2.2 1.9

 

 

 

 

 

 

 

 

The results show that there is a short term benefit for students who are more
active participants in the demonstration process (Table 3). The most notable difference
in the summaries was that students who were given a worksheet commonly cited their
observations and data in their explanations. Students who simply watched and took
notes on their own did not include details about the specific reaction they saw.

Although the type of presentation made a difference on the short term
formative assessment, the results were more equal for the posttest at the end of the
unit (Table 2). Students who did not see the demonstration had 0% improvement.
Students in the specific group had a 12% improvement, the generic group has 14%
improvement and students without a worksheet had 8% improvement. Students who
were given supplemental materials performed better that those who were not and
much better than students who did not see the demonstration at all.

Table 4. Demonstration 2, Properties of Gases: Pretest and posttest assessment data by
engagement method.

Control % SW % GW % NW %

Pre Post Increase Pre Post Increase Pre Post Increase Pre Post Increase

 

 

 

60 55 -5 50 85 35 54 84 30 52 86 34

 

 

 

 

 

 

 

 

 

 

 

 

 

 

34

 

For the second demonstration, Properties of Gases, students in the specific
group had an improvement of 35% from the pretest to the posttest (Table 4). Students
in the generic group improved 30%, students without a worksheet improved 34% and
the control group actually had a decrease in their scores by 5%. The fact that the
control group scored lower on the posttest than on the pretest illustrates the important
visual aspect of chemical demonstrations. At the end of the unit students commented
that remembering the gas properties they saw demonstrated in class helped them to
answer questions on their test. Clearly, students who did not see the demonstrations
were at a disadvantage.

Table 5. Demonstration 3, Pressure, Volume & Temperature Relationships: Pretest and posttest
assessment data by engagement method

Control % SW % GW % NW %

Pre Post Increase Pre Post Increase Pre Post Increase Pre Post Increase

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4O 80 4O 35 77 42 23 64 41 32 72 40

 

Table 6. Demonstration 3: Average scores on daily summary out of three possible points.

SW GW NW
Daily Summary Average Score . 2.5 2.1 2.0

 

 

 

 

 

 

 

 

The third demonstration illustrated the relationships between pressure, volume,
temperature and the gas laws. The specific group improved by 42%, the generic group
improved by 41%, the no worksheet group and the control group both improved by 40%
(Table 5). The improvement was almost the same for all three demonstration methods
and students who did not even see them. This was most likely because the gas laws
were a central theme of the unit and the demonstrations were just one of many

techniques used to teach the concepts. Although different techniques were used for

35

the demonstration, all students completed the lecture, labs and homework assigned for
the topic.

To try to determine the effectiveness of the three teaching methods for this
demonstration, the daily summaries were graded using a three point rubric (Table 6).
One point was earned for summarizing the procedural details of the demonstration.
Two points were earned for relating the demonstrations to the individual gas laws.
Three points were earned for describing the mathematical relationship between the
variables. Again, the daily formative data shows that students benefit when they are

more actively engaged in the demonstration process.

Table 7. Demonstration 4, Graham’s Law and Effusion: Pretest and posttest assessment data by
engagement method.
moi % sw % ow % NW %

Pre Post Increase Pre Post Increase Pre Post Increase Pre Post Increase

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

43 85 42 I4 86 72 23 92 69 21 57 36

 

The fourth demonstration illustrated Graham’s Law and compared rates of
effusion for helium and nitrogen gases. The pretest and posttest data for this activity
showed a large difference between students who participated in the process and those
who did not (Table 7). The data show a definite increase for the two groups who were
given supplemental materials and the no worksheet group actually had less
improvement that students who did not see the demonstration at all.

The difference between the pretest and posttest data shows that not only is it
important for students to have a visual component to the demonstration but that

calculations and applications are important. All of the students in each method group

36

saw the same demonstrations, but only students in the specific and generic groups were
required to apply the data to other situations.

Table 8. Demonstration 5, Hot Air Balloons: Pretest and posttest assessment data by
engagement method.

Control % SW % GW % NW %
Pre Post Increase Pre Post Increase Pre Post Increase Pre Post Increase

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

42 58 I6 44 67 23 37 81 44 18 82 64

 

The data for the hot air balloon demonstration are anomalous as compared to
the other demonstration data. For this demonstration the group that did not
participate had the greatest increase, but it was partly due to having significantly lower
scores on the pretest (Table 8).

A comparison of the posttest scores for the hot air balloon demonstration still
shows that the no worksheet group performed the best on the posttest assessment.
Overall, the data for this activity show that the specific worksheet was least helpful for
students. This could be due to the design of the worksheet itself, which was not very
detailed for this activity. Perhaps it did not lead students to draw any additional
conclusions that they would not have developed on their own.

Table 9. Demonstration 6, Gas Density: Pretest and posttest assessment data by engagement
method.

Control % SW % GW % NW %

Pre Post Increase Pre Post Increase Pre Post Increase Pre Post Increase

 

 

 

81 81 O 43 77 34 53 72 19 58 77 19

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The Gas Density data (Table 9) are quite different from the Hot Air Balloon
demonstration data, though they were done the same day. The gas density data

support my hypothesis that students in the SW group will have the greatest increase in

37

assessment scores. Students were very engaged in this demonstration, as the falling

carbon dioxide filled soap bubbles can be quite dramatic.

Table 10. Demonstration 7, Magnesium and Hydrochloric Acid: Pretest and posttest
assessment data by engagement method.

Control % SW % GW % NW %

Pre Post Increase Pre Post Increase Pre Post Increase Pre Post Increase

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

10 55 45 34 49 15 31 64 33 27 63 36

 

Results from the Magnesium and Hydrochloric Acid demonstration were
unexpected (Table 10), in that students who saw the demonstration and participated
with the specific worksheet only improved by 15%. The fact the control group had the
best improvement leads me believe that there were other factors that determined
student success on this topic. This demonstration addressed the relationship between
stoichiometry and gases, 3 central concept in the unit. I suspect that the posttest
question really measured the students’ proficiency with stoichiometry, rather than the
effect of the demonstration had on helping students learn the material as compared to
other instructional methods. In addition, the control group had the lowest pretest

scores which also contributed to a larger improvement.

Table 11. Demonstration 8, Rate of Evaporation: Pretest and posttest assessment data by

engagement method.
Control % SW % GW % NW %
Pre Post Increase Pre Post Increase Pre Post Increase Pre Post Increase

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0 l3 l3 8 35 27 13 57 44 4 33 29

 

Results for the Rate of Evaporation demonstration were inconsistent (Table 11).
In this case, seeing the demonstration improved the scores, but the improvement

between the three test methods was inconsistent. The generic worksheet group had

38

 

the greatest improvement, and the specific group had about the same as those without
a worksheet. It appears that the specific worksheet did not help students but the
generic worksheet did.

The day this demonstration was presented a fire drill occurred during the
presentation to the generic group. This required the demonstration to be done over
two days, which gave this group more time to work with the data. Perhaps introducing
the material one day and coming back to it again a second day helped the students in
this group gain a better understanding of the concepts and perform better on the

posttest.

Table 12. Demonstration 9, Phase Diagrams: Pretest and posttest assessment data by

engagement method.
Control % SW % GW % ' NW %
Pre Post Increase Pre Post Increase Pre Post Increase Pre Post Increase

 

 

 

28 50 22 29 67 38 21 53 32 31 57 26

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The Phase Diagram demonstration was the final demonstration of the project
(Table 12). Students saw a series of three phase changes related to pressure and
temperature and the corresponding phase diagrams. Students in the specific group had
the greatest improvement at 38% increase from the pretest to the posttest. All three
methods had a greater improvement that the control group which increased by 22%.

The data for this demonstration show that students who saw the demonstration
had a better understanding of the chemical concepts than students who were absent.
They also support the hypothesis that students who are given materials will perform

better than students who are not and that if the materials require students to make

39

predictions and apply the concepts to other situations they will have a better
understanding of the material.

According to this analysis, students in the specific worksheet group had the
greatest improvement 5 times, the generic group had the greatest improvement twice,
the no worksheet group improved the most for one demonstration and the control
group also had the greatest improvement for one demonstration. This indicates that
there is some rationale for instructors to hold students more accountable during the
demonstration process. Students who were required to make predictions, record data
and observation, support conclusions with calculations and apply their results to new
situations performed better on assessments a majority of the time.

For some instances where the pretest and posttest data did not support the
hypothesis, evaluation of the daily summative assessment data (Tables 3 and 6) showed
that at the end of the demonstration, students who used the specific worksheets were
better able to articulate the results of the demonstration and its related chemical
concepts. This also points to a benefit of student interaction during demonstrations.

The summative data from student surveys support the hypothesis that students
will perform better if they have more involvement in the demonstrations process.
Students commented that they found the visual aspect of demonstrations useful for
remembering the relationships between variables for the gas laws. Students also liked
that the demonstration guide had been prepared for them so they knew what

information was considered the most important.

40

Survey comments also indicated that some students were disappointed that they
were expected to record data and observations during the demonstrations. They
frequently asked why they were expected to do anything and could not just watch. This
attitude reflects my earlier experiences where students viewed demonstration time as
more for entertainment and less for learning. Although I explained to students that the
material covered in the demonstrations was likely to appear on tests, some students
said they would not have recorded information if they were not required to. Even
students in a college prep level class need to be held accountable for all of the class
activities to be successful.

In summary, the primary data analysis for this project consisted of comparing
pretest and posttest scores for questions related to the chemical concepts presented to
students over nine days of classroom demonstrations. The majority of the data
supports the project hypothesis that students will understand the concepts better when

they are required to participate in the demonstration process.

41

STATISTICAL ANALYSIS

Data were also statistically analyzed for the project by using a t-test to compare
the improvement data between the three research method groups and the control
group for the study. Generally, t-test analyses with a p value less than 0.05 are
considered statistically significant. The first t-test analysis was a comparison of
improvement for the nine demonstrations by students in the control group compared to
improvement of all other students who saw the demonstrations. The results show a
value of p = 0.038, indicating that the data used in the project analysis is statistically
different.

A t-test was also done to compare the performance of each of the three research
methods to the control group. The t-test for the SW and control group comparison
showed a value of p = 0.040. The t-test for the GW and control group comparison
showed a value of p = 0.005. The t-test for the NW and control group comparison
showed a value of p = 0.039. All of the improvement scores used for this study fall

within that range when compared to the control group improvement data.

42

CONCLUSION

The idea for this project developed from the request by students to see more
demonstrations in their college prep chemistry class. Though often exciting, chemical
demonstrations consume resources and both instructional and teacher preparation
time. The goal of this project was to determine whether chemical demonstrations have
enough educational value to justify the cost and time required to implement them in
the classroom. The hypothesis of this project predicted that demonstrations which
involve students by means of making predictions, analyzing data and applying results to
new situations are more effective educational tools than demonstrations where
students are passive observers.

To test the hypothesis students were divided into three groups: 1) SW, 2) GW,
and 3) NW. In the SW group students were given materials to help them participate in
the data collection and analysis part of the demonstrations. A specific worksheet was
developed for each of the nine days of demonstrations included in the study. Students
in the GW group were given a generic worksheet for recording observations and
summarizing the concepts. The same sheet was used for each demonstration. The NW
group was not given any supplemental materials.

Data were collected for nine different classroom demonstrations. Scores on
pretest and posttest questions were analyzed for improvement on each of the three
groups. The improvement for each research method was compared to a control group
of students who were absent for the demonstrations. Daily summaries were also

collected for all students at the end of each demonstration. The summaries were

43

analyzed on a three point scale for understanding of the chemical concepts presented in
the demonstrations. In addition, students responded to survey questions by indicating
their preferences about including demonstrations as part of regular classroom
instruction.

The data analysis provided a variety of results. The general analysis showed that
students who saw demonstrations performed better on the final assessment than those
who did not. It also showed that students in the generic group had the most
improvement from pretest to posttest (Figure 1). These results supported the
hypothesis that demonstrations can improve student performance, but not that the SW
group would have the most improvement (Figure 1).

Pohl (2005) found that seeing demonstrations did not increase student
performance on assessments. His data analysis showed that students who saw
demonstrations had no greater improvement that those who did not. Beall (1996) also
confirmed that demonstrations were not worth the necessary preparation time and
expense. Their findings contrast the analysis for this project, which showed that there is
an educational benefit for students who see chemical demonstrations over those who
do not.

More specific analysis of the pretest and posttest scores evaluated the
improvement by each test group for each of the nine demonstrations. This analysis
showed that the specific group did have the most improvement for five of the nine
demonstrations. The NW group had the least improvement the majority of the time.

These results agree with those of Crouch (2004) who found that demonstrations where

44

students are passive observers are ineffective at teaching students the scientific
concepts.

Although the data analysis for each of the individual demonstrations supported
my hypothesis, l was a bit disappointed that the overall average improvement for all
demonstrations combined (Figure 1) did not. There were two demonstrations in
particular, The Magnesium and Hydrochloric Acid demo and The Rate of Evaporation
demo, that seem to be outliers. Considering possible reasons for this led me to evaluate
the demonstrations themselves more carefully. Both covered concepts that were ”big
ideas” in their respective units. The Magnesium and hydrochloric Acid demonstration,
for example, addressed the concepts of gas stoichiometry and the ideal gas law. These
concepts were also extensively covered in the lecture notes, the homework and in the
laboratory.

In reflection, it may be difficult to tell the role the demonstration itself actually
played in students’ overall understanding of the material. I suspect that most likely the
posttest questions were really testing their overall understanding of gas stoichiometry
from the gas laws unit in general. A better analysis of the effect of the demonstrations
themselves may have been obtained by giving students an assessment shortly after the
demonstrations, rather than at the end of the unit.

The other outlier demonstration, Rate of Evaporation, required students to
watch as the Vernier technology produced a graph of temperature change vs time for

six volatile organic compounds. Students had to analyze molecular structure and make

45

predictions about which compounds would have the greatest temperature change and
thus the greatest rate of evaporation.

The specific materials for this demonstration were perhaps the most complete
that I used for the entire project in terms of SW student prediction and discussion as
part of the demonstration process. Students had to make and discuss predictions and
use their observations to revise predictions for the next trial. They had to draw
molecular structures and graph their data to look for overall trends. Although students
couldn’t actually see molecules evaporate, the demonstration did incorporate a visual
element by displaying the real-time temperature graph for the class.

To see that the specific group did not have the greatest improvement from the
pretest to the posttest (Table 12), led me to consider other factors that may have
contributed to the posttest data. The Rate of Evaporation demo also addressed
concepts that were covered extensively during the unit on intermolecular forces and
phase changes. Students analyzed the same set of six organic compounds numerous
times in lecture, homework and the lab, including a lab activity on rate of evaporation.
To see the actual impact of the demonstration materials on the SW group, questions
that related to the demonstration itself rather than just the overall concepts, should
have been included as part of the posttest.

A demonstration that was a better representation of the project goals was the
Graham’s Law and Effusion demonstration. For these concepts, the demonstrations
were the only method of instruction used to teach the concepts. It was a good

reflection of the project goals because students were only able to rely on their

46

experience with the demonstration to answer the posttest questions. The data analysis
for this demonstration shows that students who were in the SW group had the greatest
improvement, closely followed by students in the GW group. Improvement by students
in the NW and control groups was significantly lower. The results of the more specific
analysis for the Graham’s Law demonstration agree with those of Hake (1998) who
found that students performed best when actively engaged in the discovery of concepts
as opposed to more passive instructional methods.

The data analysis for this project leads me to recommend that if further study of
this hypothesis is done it should include concepts that can better be isolated as
demonstrations. Demonstrations similar to those for effusion or gas density were more
appropriate than those that related to the more central themes of the unit. Choosing to
include demonstrations that related to main concepts made the overall analysis difficult
to interpret. Although I felt the demonstrations were beneficial to students, it was
difficult to extract the role of the three engagement methods themselves from the more
general assessment question data.

Another surprising aspect of the project was the performance of students in the
GW group. Classroom observations led me to subjectively conclude that this group
would have the least improvement of the three research method groups. It seemed
that students found the generic worksheet cumbersome because it only asked for a
description of the demo, result and a brief summary. Students were not given specific
questions or provided with supplemental materials to help them understand the

concepts. Students seemed unsure as to where to record extra observations or other

47

related information and were often seen going back and forth between the worksheet
and their own notebook.

The other two research method groups did not seem to experience this issue.
The SW group had the necessary resources and direction for each demonstration. The
NW group did not, so students who chose to do so recorded everything in their own
notebook without having to go back and forth to a separate sheet.

I expected that the discontinuity of the GW engagement method would cause
confusion for students and thus lower their posttest scores. However, this group had
the highest overall average improvement and the highest individual improvement for
two of the nine demonstrations. The improvement for the GW group was also greater
than the NW group for six of the nine demonstrations. In these cases students were not
hindered by the confusion of the generic worksheet.

Overall, this project was a success. A majority of students submitted comments
stating how much they enjoyed seeing the demonstrations that were included in the
project. This suggests that demonstrations can, in fact, make teaching and learning
chemistry ”exocharmic,” which Bodner (2001) felt could increase interest and possibly
lead students to investigate the science behind the demonstrations.

My initial goal was to determine whether or not demonstrations have enough
educational value to compensate for the additional time and resources they require.
Working on this project forced me to continuously research and prepare a series of
demonstrations and allot class time for their presentation. It also required the

preparation of specific supplemental materials for each of the demonstrations used in

48

this study. Although the monetary cost was not great, the amount of preparation time
devoted to the demonstrations was substantial. The data analysis shows that students
do benefit when demonstrations are included as part of the instructional process.
Students benefit somewhat because they like to see demonstrations and find them
entertaining. However, students can benefit greatly if they are held accountable for
active learning as part of the demonstration process. Students who made predictions
and evaluated their observations for further application benefitted more from the
process from the demonstration process that those who sat as passive observers.

The use of chemical demonstrations is justified as being educationally valuable in
the college prep chemistry classroom. I plan to use the materials I developed for this
project, perhaps with some revisions to encourage students to think more deeply about
their observations. Demonstrations can be a valuable instructional tool if presented in a
way that incorporates them as part of the learning process, rather than just as

entertainment.

49

APPENDIX A

The Educational Value of Chemical Demonstrations in a College Prep Chemistry
Classroom

MASTER’S THESIS RESEARCH PROJECT CONSENT FORM

Mrs. Hagerman

Hartland High School

Dear Parent or Guardian,

As a student in my College Prep Chemistry class, your child is being asked to participate
in the thesis research project for my master’ 5 degree from the Division of Science and
Math Education at Michigan State University. The research will focus on how chemical
demonstrations affect student comprehension of the chemical concepts presented in
class. The project will use a variety of methods to incorporate chemical demonstrations
into the class presentations. The research will attempt to determine the best method
for performing demonstrations in a chemistry classroom.

The data used for the project will be in the form of routine class work such as student
homework, surveys, pre-and post tests and quizzes. The data collected for the project
will remain confidential and your child’s privacy will be protected to the maximum
extent allowable by law. Your child’s identity will not be attached to any of the data
analyzed in the research and will not be identified in any of the images used in the thesis
presentation. The only risk to students in the study is that there is no educational value
to observing chemical demonstrations as part of the normal classroom process. I may
discover through the project that demonstrations serve only as entertainment and are
not an educational use of class time. The amount of instructional time spent on
demonstrations will be small compared to other activities, so overall risk is considered
minimal. However, if demonstrations prove to be an effective teaching tool, student
learning will increase as a result of the study.

Participation in this research project is voluntary. There will be no penalty for those not
willing to participate, though they will still be required to complete all assignments.
Consent forms will be sealed during the data collection and stored in the main office. I
will not know until the end of the project the names of students who chose to
participate. At any time during the research you may request that your child’s data not
be included. Requests to withdraw before grades are posted for assignments included
on the study should be made to Mr. Lawrence Pumford, Dean of Students. Those
wishing to withdraw from the study after grades are posed may inform me directly.
Students will not be required to complete certain assessments, such as surveys, that are
not part of normal classroom instruction. I will not know until after grades are
completed the identities of students who answered survey questions.

50

If you are willing to have your student participate in the study, please complete the
attached form and return it to me by October 1, 2009. If you have any questions about
the project please contact me by email at katehagerman@hartlandschools.us or by
phone at (810) 626-2323. You may also contact the program director, Dr. Merle
Heidemann, at heidemaZ@msu.edu or (517) 432-2152 ext 107.

If you have any questions about the roles and rights of a research participant, would like
to obtain information or offer input, or would like to register a complaint about this
study, you may contact, anonymously if you wish, the Michigan State University/s
Human Research Protection Program at 517-355-2180, Fax 517-432-4503, or email
irb@msu.edu or regular mail at 202 Olds Hall, MSU, East Lansing, MI 48824.

Thank you,

Kate Hagerman

I voluntarily agree to have participate in Mrs.
Hagerman's thesis research study. (Print student name)

Please check all that apply:
DATA:

I give Mrs. Hagerman permission to use data generated from my child’s work in
College Prep Chemistry. All data from my child Will remain confidential.

I do not wish to have my child’s work used in this thesis research project. I
acknowledge that my student’s work will be graded in the same manner
regardless of participation.

IMAGE:

I give Mrs. Hagerman permission to use images of my child through video and
photography during her work on this thesis project. My student will not be
identified in these images.

I do not wish to have my student’s image used at any time during this thesis
project.

 

(Parent/Guardian signature) (Date)

I voluntarily agree to participate in this thesis project.

 

(Student signature) (Date)

51

APPENDIX B

College Chemistry 09/10 DEMO SURVEY

Do you think it is important to include chemical demonstrations in a chemistry
class?

A. Yes

B. No

C. Unsure at this point.

What is the purpose of chemical demonstrations in chemistry class?
A. to get students excited about learning chemistry

B. for entertainment only

C. to help students learn concepts

Which activity is the best for helping students learn material?
A. class notes/lecture ’

B. labs

C. demonstrations

D. homework

E. reading the textbook

There are four ways of doing demonstrations that will generally be used in this
class. They are:

1. demonstrations for entertainment only

2. demonstrations that show a concept currently covered in class

3. demonstrations with a worksheet to record and analyze observations

4. demonstrations that are an introduction to a lab or group activity

Of the four types, which do you feel:
A. is the style you most prefer
B. is the best for learning the material

C. is the most helpful for answering test questions
D. is the most memorable

52

APPENDIX C
Gas Laws Pretest/Posttest Questions 8: Rubric
Answer the following to the best of your ability.

1. Air pressure is caused by the force of air particles pushing against the surface of
objects, such as a desk. If four types of balls were sitting on a desk and making contact
with about one square in of the surface, which would push on the desk with a force
closest to the force of the air pushing on a square inch of the desk surface?

A. ping pong ball

8. inflated beach ball holding 22.4 L of air

C. basketball

D. 15 lb bowling ball.

Answer: 0
1 point

2. Which of the following can be done using the force of atmospheric pressure to
accomplish the task? Circle all answers you believe to be correct.

A. crush a pop can

8. break a wooden ruler

C. inflate a balloon

D. crush a 55 gallon steel drum

All are correct.

3 points earned for selection of all four or any 3
2 points earned for selecting any 2

1 point earned for selecting any 1

3. For a demonstration, a chemistry teacher wants to fill balloons with increasing
amounts of CO; gas using baking soda and vinegar according to the equation below.
Describe some factors that should be considered to ensure each balloon is larger than
the one before.

NaHCO; + H(C2H302) ‘9 N3(C2H302) '1' H20 + C02

3 points earned for explaining that the limiting reactant will determine the amount of
gas

2 points earned for say that the amount of reactants will determine the gas production
1 point earned for variables of temperature or pressure

53

Four commonly used gas law equations are shown below. For items 4-8, choose the gas
law that best describes each situation. Choices may be used more than once or not at
all.

4. Car tire pressures have to be checked A. Boyle’s LawP1V1 = P2V2
after a drive to Florida
5. A propane tank gets frost on the outside B. Charles’s Law y; = k
as it is used for a gas grill in the summer T1 T2
6. Air filled balloons stay inflated better C. Gay-Lussac’s Law E; - 3;
than helium filled balloons T1 T2
7. The most important rule in scuba diving D. Graham’s Law 12; = VM;
is to never hold your breath r2 M2

8. Aerosol cans should never be exposed to fire

repose?!»
n>onn

point each

9. The teacher fills large size balloons with equal volumes of the following gases and
wants the balloons to sit on the lab counter. Circle the ones that should have to be
weighted down.

He N2 CH4 C02

2 points earned for selecting only He and CH4

1 point earned for selecting either He or CH4
1 point earned for selecting all four

11. A teacher wants to produce hydrogen gas by adding magnesium metal to
hydrochloric acid, according to the balanced equation below.

Mg + 2HCI -) MgCIz + H2

If the teacher wants to produce 8.0 Liters of gas at room conditions, what mass of
magnesium is required?

5 points earned for using the ideal gas law with correct calculations and units

4 points earned for using the ideal gas law with an incorrect calculation or unit
3 points earned for using the ideal gas law with an incorrect calculation and unit

54

2 points earned for a calculation using 22.4 Liters/mol
1 points earned for an attempt at a calculation

12. How does a hot air balloon work? Explain in detail using chemical principles.
3 points earned for correctly explaining the temperature, volume and density
relationships

2 points earned for describing the relationship for two of the three variables
1 point earned for a statement of hot air rises with no explanation

55

IMF and Phase Changes Pretest/Posttest Questions and Rubric
Answer the following to the best of your ability.

1. Which of the following liquids will have the greatest rate of evaporation?
A. H20 8. C5H12 C. C5H12 D. CH30H

1 point earned for choice B.

2. Which of the following factors can be used to measure the evaporation rate of
a liquid?
A. temperature change
B. boiling point elevation
C. viscosity
0. rate of effusion

1 point earned for choice A.

3. The physical properties of gases, liquids and solids are influenced the most by:
A. phase B. crystal structure
C. specific heat 0. intermolecular forces

1 point earned for choice D.

4. Which of the following temperatures would be considered valid boiling points for
water? Circle all that are correct.

0 O

32 c 100°C 373 K 25 c o c 298 K

3 points earned for choosing all or all except 0°C.
2 points earned for choosing any three
1 point earned for any 1 or two

6. Iodine forms iridescent purple crystals at room temperature. When heated
slightly the iodine crystals will undergo the process of sublimation. Draw models of the
iodine molecules before and after sublimation in the boxes below. Use ”I” to represent
an iodine atom.

 

 

sublimation

L
r

 

 

 

 

 

 

Before after

56

5 points earned for showing correct representation for solid and gas phases and
breaking only IMFs

4 points earned for showing correct representation for solid and gas phases and
breaking only IMFs, but not using ”I” to represent the atoms

3 points earned for breaking only IMF but showing the incorrect phase change
2 points earned for correct representation of phases

1 point earned for one correct phase representation

57

APPENDIX D

Limiting Reactant and Carbon Dioxide Production
Student Version

1. This demonstration involves the following chemical reaction. Is it balanced?
NaHCO; 'I' H(C2H302) -) N3(C2H302) + H20 + C02

2. Draw the four flasks set up on the demonstration counter. Label the contents of
each.

3. Predict what will happen when the baking soda in the first balloon is emptied into
the flask.

4. Record observations for the first flask.

5. Predict what will happen when the baking soda in the 2"d and 3“!l balloons is emptied
into each flask.

6. Record observations for the 2"“I and 3rd flasks.

7. Predict what will happen when the baking soda in the 4th balloon is emptied into the
flask.

58

8. Record observations for the 4th flask.

9. Complete the table for the amounts of moles of reactants and products in each trial.

N8HCO3 + H(C2H302) 9 N3(C2H302) + H2O + CO2

 

 

 

 

 

 

 

 

 

 

 

 

10. Summarize the demonstration and the chemical concepts involved.

59

Limiting Reactant and Carbon Dioxide Production
Teacher Version

Materials

4 250 mL Erlenmeyer Flasks
Baking soda

5% vinegar

4 large size balloons

1 plastic spoon for scooping

Set - Up
1. Fill four equal E-flasks with 200 mL of 5% vinegar.
2. Label four large-size balloons .25, .5, 1 and 2
3. Fill the balloons with .25 scoop, .5 scoop, 1 scoop and 2 scoops of baking soda,
respectively.
4. Stretch the opening of each balloon over the mouth of one of the flasks.

Procedure

1. Empty the .25 balloon into the vinegar in the flask. The balloon will fill slightly
with carbon dioxide gas.

2. Have students make a prediction about the volume of the next two balloons and
react each.

3. Have students predict the volume of the fourth balloon and react the contents.
When the reaction is complete excess baking soda should be present in the flask.

4. Complete the chart using the values on the balloons as moles.

60

Properties of Gases Demo Sheet
Student Version

Demo 1
a. Record mass of empty syringe . Record mass of filled syringe
b. What does this demonstration prove?
Demo 2
a. With a partner, list some examples of fluids.
b. Discuss whether air can be considered a fluid and explain why/why not.

c. Record observations:

b. What does this demonstration prove?

Demo 3
a. Record observations:

b. What does this demonstration prove?

Demo 4
a. Predict what happens when force is applied to the ruler?

b. Record observations

c. Explanation?

61

Demo 5 — Draw the contents of the can using dots for molecules and arrows to
represent the force of air pressure.

Initial During heating After Cooling

Predict what will happen when the can is added to the ice water.

Use the diagrams to explain your observations.

Demo 6 -
3. Draw the molecules in the system before, during and after the balloon is
added.

Summarize today’ s demonstrations and the chemical concepts involved.

62

Properties of Gases Demo Sheet
Teacher Version

Demo 1
Mass an empty syringe and an air-filled syringe on a microgram balance. A larger
syringe will give a better difference.

Demo 2

Light a small candle and place it on the demonstration counter. Use an empty 2 Liter
soda bottle to blow a puff of air and extinguish the candle. Relight the candle and
repeat from a distance of 1-2 meters. This takes practice to get the bottle height just
right to extinguish the candle.

Demo 3

Fill a syringe with a volume of water equal to the volume of air in the syringe from Demo
1. Cap each syringe. Pass the set around so students can compare the relative
compressibility of each.

Demo 4

Place a wooden meter stick on the lab counter with the 50 cm mark at the edge of the
counter. Place a piece of poster board over the half of the ruler on the counter so the
all 50 cm are covered. Have a student hit the uncovered end to the ruler with their fist.
The ruler will break under the force of the pressure from the fist at one end and the
pressure of air on the poster board at the other. This can be done with newspaper, but
is less reliable.

Demo 5

Place about 5-10 mL of water in an empty pop can and heat to boiling with a hot plate
or Bunsen burner. When the can is filled with water vapor, use beaker tongs to invert it
into a very cold ice water bath.

Demo 6

Add about 25 mL of water to a 500 mL Erlenmeyer flask and heat to boiling. When the
flask is filled with water vapor, place a large size balloon over the opening and continue
heating until the balloon inflates. Remove the flask from the heat. The balloon will
deflate and reinflate inside the flask.

63

PVT GAS LAWS DEMOS
Student Version

DEMO 1: Marshmallow Madness (pressure vs volume)
Predict what happens to the marshmallow when the vacuum pump is turned on.
Observations:
1. What happens to pressure in the chamber as the vacuum pump runs?
2. How does this change affect the air pockets in the marshmallow?
3. Write a statement relating pressure and volume.
DEMO 2: The Cartesian Diver
Carefully squeeze the bottle and watch what happens to the dropper inside.
Observations:
1. What happens to the pressure inside to bottle as it is squeezed?
2. What happens to the volume of air inside the dropper as the bottle is squeezed?
3. How does this change affect the density of the diver? Use the equation for

density to prove your answer.

4. Write a statement that summarizes all the processes/changes involved from
beginning to end.

APPLICATION: Why is the #1 rule of scuba diving to never hold your breath? Discuss
with a partner and write you answer below.

64

DEMO 3: Volume vs. Temperature
Predict what will happen to the balloons when exposed to warmer and cooler
conditions.

Observations:

1. Write a statement relating temperature and volume.

DEMO 4: Temperature vs Pressure
Predict what happens to temperature in the container as the pressure is decreased.

Observations:

Predict what happens to temperature in the container as the pressure is increased.

Observations:

1. Write a statement relating temperature and pressure.

APPLICATION
Explain why a sealed aerosol should never be thrown into a fire.

SUMMARY: Write a summary of today’ s demonstrations and the chemical concepts
involved.

65

PVT GAS LAWS DEMOS
Teacher Version

DEMO 1

Place a marshmallow in an E-flask and connect to a vacuum pump. Evacuate the flask
until the marshmallow stops expanding. Equalize the pressure to flatten the
marshmallow. This can also be done with a small marshmallow in a syringe.

DEMO 2
Set up a Cartesian diver in a 2 Liter bottle of water so the diver sinks when the bottle is
squeezed. Pass around for student observation.

DEMO 3
Inflate three balloons to equal volume. Place one on a beaker of warm water, the other
in a container of liquid nitrogen and keep the third as a control.

DEMO 4

Drill a hole in a 1 or2 L bottle cap so that a truck tire replacement valve stem will fit
securely in the hole. Affix an LCD temperature strip to the inside of the bottle. Cap the
bottle and attach a tire pump with a pressure gage to the valve stem. Note the
temperature change as the tire pump is used to increase the pressure.

Repeat the procedure, but this time place the LCD strip in a E-flask and connect it to a
vacuum pump. Note the temperature change as pressure is decreased.

66

Graham's Law and Effusion
Student Version

DEMO 1: Escaping Gases
Pick up and closely observe each balloon.

Observations :

Discuss with a partner possible reasons for your observations.

Predict how the observations would be different if a mylar balloon were used for the
demonstration.

1. Identify and describe the property of gases particles that causes this occurrence.

DEMO 2

Predict what will happen to the volume of the two balloons over a period of 24 hours.

Record observations:

Use a Graham’s Law calculation to support your observations.

Summarize today’s demonstrations and the chemical concepts involved.

67

Graham's Law and Effusion
Teacher Version

DEMO 1

Add a few drops of cooking extract (vanilla, strawberry, mint, etc.) to a few balloons and
inflate. Pass the balloons around the classroom for student observation. One set of
balloons should last the entire day.

DEMO 2

Inflate one balloon with helium and another with an equal volume of air and plane them
on the demonstration counter for student observation. After 24 hours the helium
balloon will have a much smaller volume than the air-filled balloon. Students can use
nitrogen gas for the air balloon and get good results for their calculation.

68

HOT AIR BALLOONS AND GAS DENSITIES Demo Sheet
Student Version

DEMO 1: Gas bubbles

Predict whether bubbles of methane will float, sink or be neutrally buoyant in air.

Observations:

Predict whether bubbles of CO2 will sink or float in air.

Observations:

Discuss your observations with a partner. Try to find some differences between the two
gases that could explain the observations.

Include a calculation to support your answer.

69

DEMO 2: Hot Air Balloon

Predict what will happen when a helium balloon is heated.

Observations:

Draw a diagram of the particles in the balloon before and after heating.

Discuss with a partner which gas law equations could be applied to this situation and
why.

Explain your observations in terms of the gas laws, a calculation may be included.

Summarize today’ s demonstrations and the chemical concepts involved.

70

HOT AIR BALLOONS AND GAS DENSITIES Demo Sheet
Teacher Version

DEMO 1:
Methane Bubbles: Prepare a bubble mixture of about a 1:1 ratio of dish soap (Dawn
and Joy work well) and water. Add about a tablespoon of glycerol and stir.

Connect a 2ft piece of rubber tubing to a funnel at one end and to the gas jet at the
other end. Dip the funnel in the bubble mixture and gently turn on the gas. The
methane will form bubbles in the soap mixture that will separate and rise to the ceiling.
If desired, the bubbles can be igniteg using a burning splint or wax taper taped to the
end of a meter stick.

Carbon dioxide bubbles: Add dry ice pieces to an empty 2 Liter bottle. Add water to
the bottle and attach a piece of PVC pipe as a spout. Bubble the carbon dioxide through
the same bubble solution used in DEMO 1. The Carbon dioxide bubbles should separate
and fall to the floor.

DEMO 2:

Fill a mylar balloon about 2/3 full with helium. Add enough paperclips to the bottom of
the balloon so that it just rests on the lab counter. Use a hairdryer to heat the helium
gas in the balloon until it rises on its own. As it cools it will sink and the process can be
repeated.

71

Mg + HCI Demo Sheet
Student Version

1. Predict what will happen when the Mg metal and HCI react together. Write a
balanced equation to support your prediction.

2. Observations:

3. Use the volume of gas produced to calculate the original mass of magnesium.

Record the actual mass here: . Calculate the percent error.

Discuss with a partner possible sources of error.

4. Use the ideal gas law to find the mass of magnesium instead of 22.4 L/mol.

5. How does this affect the percent error?

6. Write a summary of the demonstration and the chemical concepts involved.

72

Mg 4» HCI Demo Sheet
Teacher Version

Materials:
1 -2 cm Mg ribbon, polished and massed
10 mL 6 M HCI

Thread

1 L beaker
25 mL graduated cylinder
Scrap of paper 10 cm x 10 cm

Procedure:

1.
2.
3.

Tie one end of the thread around the Mg ribbon.

Fill the beaker with about 800 mL of tap water.

Add the HCI to the graduated cylinder. Carefully fill the cylinder the rest of the
way with water. Try to keep the acid as a separate layer on the bottom of the
cyinder.

Place the Mg on top of the water in the cylinder and cover the top of the cylinder
with the scrap of paper. While holding the paper tightly, quickly invert the
cylinder into the beaker of water.

The acid will sink and react with the magnesium. The thread will keep the ribbon
from floating to the top of the water. As gas is produced it is collected in the
cylinder.

At the end of the reaction the pressure in the cylinder can be equalized with the
atmospheric pressure by moving the cylinder up or down so the water level is
the same inside and out.

73

Evaporation and Intermolecular Forces
Student Version

Background Information: Complete the following table.

 

Name

Formula

Structure

Total electrons

IMF

 

Ethanol

 

Propanol

 

Butanol

 

Pentane

 

Methanol

 

Hexane

 

 

 

 

 

 

Data Table 1

 

Name

t1

t2

At

 

Ethanol

 

 

Propanol

Predicted
At

Justification

 

 

Butanol

 

 

Pentane

 

 

Methanol

 

 

Hexane

 

 

 

 

 

 

 

 

 

74

 

 

4.

5.

6.

What factor is responsible for determining the rates of evaporation for butanol
and pentane? Support your answer with examples from the data.

a. Which of the alcohols studied has the strongest IMFs?
b. the weakest?

c. What factor is responsible for this? Support your answer with examples from
the data.

3. Which of the alkanes studied has the strongest IMFs?

b. the weakest?

c. What factor is responsible for this? Support your answer with examples from
the data.

Explain why evaporation is an endothermic process.

Explain why molecules with weaker IMFs evaporate faster.

Plot a graph of At values for the four alcohols vs the number of electrons.
Describe the trend.

 

Write a summary of the demonstration and the chemical concepts involved.

75

Evaporation and Intermolecular Forces
Teacher Version

Materials

Samples of ethanol, 1-propanol, butanol, pentane, methanol and hexane.
Temperature probe

Chromatography paper

Small rubber bands (the rolled up end of a water balloon works well)
Data interface, computer and projector.

Procedure

1. Wrap a 5-10 cm strip of chromatography paper to the end of the temperature
probe and place it in the first liquid. Record the initial temperature as t1.

2. Remove the temperature probe and note the temperature decrease that occurs
with evaporation record the final temperature after 1-2 minutes.

3. Repeat with the five remaining liquids, having students make predictions about
the At values.

4. If possible, connect the temperature probe to a computer interface and project

a graph of temperature vs time for students. The liquids and also be used two at
a time for faster data collection.

76

Phase Changes Demonstrations
Student Version

Draw a diagram representing the particles in a solid, liquid and gas below. Use dots to
represent the particles. Use dashed lines to represent IMFs.

 

 

 

 

 

 

 

 

 

 

 

 

Discuss with your partner how a substance can be altered to cause a phase change.
Record your ideas below.

Predict what will happen to the water when the vacuum pump is turned on.

Using the reference in your book, sketch a phase diagramfor H2O below.

Plot point R on the diagram to represent water at room conditions.

Draw a line to show the change that occurred with the vacuum pump.

77

Copy the phase diagram for butane given on the board. Label point R on the graph to

represent room conditions.

What changes can be made to condense butane?

How can this be done in class?

Record your observations of the iodine in the beaker.

Draw the iodine molecules (use the letter I to represent each iodine atom) before and

after heating.

 

 

heat

 

 

 

 

 

 

Now draw your prediction of the possible phase diagram for iodine.

How does your prediction compare to the actual? How is this diagram similar and
different to water and butane?

Write a summary of the demonstration and the chemical concepts involved.

78

Phase Changes Demonstrations
Teacher Version

Part 1

Fill a large, glass container with water and connect to a vacuum pump. Use the vacuum
pump to decrease the vapor pressure over the water cause it to boil at room
temperature.

Part 2
Fill a 60 mL syringe with butane and seal it with a syringe cap. Students can compress
the plunger until the butane condenses and release the pressure and see it boil.

Part 3

Place some iodine crystals in a 150 mL beaker and cover with a watch glass. Gently heat
on a hot plate until sublimation occurs. A few ice cubed added to the watch glass will
cause solid iodine crystals to deposit on the surface.

79

Demonstration Notes Sheet Name:

  

Demo Title:

Give a description of the demonstration set-up.

Record your observations and any relevant data.

Summarize the demonstration and the chemical concepts involved.

80

Demonstration Summary Sheet Name:

Summarize today’ s demonstrations and the chemical concepts involved.

 

Demonstration Summary Sheet Name:

Summarize today’s demonstrations and the chemical concepts involved.

 

81

APPENDIX E
College Chemistry 09/ 10 DEMO SURVEY RESULTS

Do you think it is important to include chemical demonstrations in a chemistry class?
A. Yes 97.7%

B. No 2.3 %

C. Unsure at this point. 0%

What is the purpose of chemical demonstrations in chemistry class?
A. to get students excited about learning chemistry 20.9%

B. for entertainment only 1.2%

C. to help students learn concepts 77.9%

Which activity is the best for helping students learn material?
A. class notes/lecture 32.1%

B. labs 22.6%
C. demonstrations 42.9%
D. homework 2.4%

E. reading the textbook 0%

There are four ways of doing demonstrations that will generally be used in this class.
They are:

1. demonstrations for entertainment only

2. demonstrations that show a concept currently covered in class

3. demonstrations with a worksheet to record and analyze observations

4. demonstrations that are an introduction to a lab or group activity

Of the four types, which do you feel:

A. is the style you most prefer
1. 29.1%
2. 50.0%
3. 10.4%
4. 10.5%
B. is the best for learning the material
1. 0%
2. 43%
3. 32.6%
4. 24.4%

82

C. is the most helpful for answering test questions
1. 0%
2. 30.2%
3. 52.3%
4 17.4%

D. isthe most memorable
1. 62.8%
2. 12.8%
3. 14.0%
4 10.5%

83

PROJECT DATA
Pretest (Pre), Posttest (Post) and Improvement (Imp) data by engagement method for each
demonstration.

 

 

 

 

 

 

 

Demo Control % SW Group % GW Group % NW Group %
Pre Post lmp Pre Post Imp Pre Post Imp Pre Post Imp
LR&CO2
45 45 0 57 69 12 58 72 14 72 79 8
Properties
of Gases 60 55 -5 50 85 35 54 84 30 52 86 34
PVT
Relation- 40 80 40 35 77 42 23 64 41 32 72 40
ships
Graham’s
Law 43 85 42 14 86 72 23 92 69 21 57 36
Hotau

Balloons 42 58 16 44 67 23 37 81 44 18 82 64

 

Gas
Density 81 81 0 43 77 34 53 72 19 58 77 19

 

Mg+HCI
10 55 45 34 49 15 31 64 33 27 63 36

 

Rate of
Evapora- 0 13 13 8 35 27 13 57 44 4 33 29
tion

 

Phase
Diagram 28 50 22 29 67 38 21 53 32 31 57 26

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

84

Comparison of Improvement Data Between Groups

Control

0
-5
40
42
16

0
45
13
22

p value

Specific
12
35
42
72
23
34
1 5
27
38
0.040198

Control

0

-5

40

42

16

0

45

1 3

22

85

Generic
14
30
41
69
44
19
33
44
32
0.005355

Control

0

-5

40

42

16

0

45

13

22

None

8

34

4O

36

64

1 9

36

29

26
0.03864

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