RESEARCH
www.rsc.org/cerp | Chemistry Education Research and Practice
Determination of students’ alternative conceptions about chemical
equilibrium: a review of research and the case of Turkey
Haluk Özmen
Received 3rd April 2007, Accepted 27th December 2007
DOI: 10.1039/b812411f
This study aims to determine prospective science student teachers’ alternative conceptions of the
chemical equilibrium concept. A 13-item pencil and paper, two-tier multiple choice diagnostic
instrument, the Test to Identify Students’ Alternative Conceptions (TISAC), was developed and
administered to 90 second-semester science student teachers enrolled in CHEM 102 Chemistry II
course in spring 2006, after they received fourteen 50-minute regular course instruction concerning
the equilibrium. The content validity of the test was established by the panel consisting of
lecturers. The Spearman-Brown reliability for the test was 0.71. Analysis of the results collected
with the TISAC show that students did not acquire a satisfactory understanding of the chemical
equilibrium concept. For the first tier of the test items, the range of correct answer was 48.8% to
78.8%. When both tiers were combined, the correct response was reduced to a range of 22.2% to
48.8%. In this study, seventeen alternative conceptions were also identified through analysis of the
TISAC. These conceptions were grouped under the headings of the application of Le Chatelier’s
principle, reliability of the equilibrium constant, heterogeneous equilibrium, and the effect of a
catalyst.
Keywords: chemical equilibrium, alternative conceptions, Turkish prospective student teachers
Introduction
Research has shown that children bring to lessons preexisting
conceptions about scientific phenomena and how natural
events occur, and ideas that can interfere with students’
learning of correct scientific principles or concepts, and
interpret any new information from the viewpoint of these
existing ideas and beliefs (Posner et al., 1982; Palmer, 1999).
This realization has caused science educators to be
increasingly
concerned
about
discovering
students’
difficulties prior to, during or after the instruction in
conceptualizing scientific knowledge, and suggesting ways of
remedying these. A number of terms are used for these ideas
constructed in students’ minds, such as alternative
conceptions (Gonzalez, 1997), misconceptions (Nakhleh,
1992), alternative frameworks (Gonzalez, 1997; Taber, 2001),
conceptual frameworks (Southerland et al., 2001), and
spontaneous knowledge (Pines and West, 1986). Taber (2000)
and Özmen (2004) have summarized these terms in detailed
reviews. Also, Taber (2002) discussed in detail the
prevention, diagnosis and cure of students’ misconceptions in
chemistry. In this study, for simplicity, the term of alternative
conception is used to describe any conceptual difficulties,
which are different from or inconsistent with the accepted
scientific definitions.
It is not surprising that students’ ideas concerning chemical
phenomena have become a popular research area, because of
the abstract nature of many chemical concepts and the
difficulty of the language of chemistry. Many students at all
Karadeniz Technical University, Fatih Faculty of Education, Department
of Science Education, 61335 Sögütlü-Trabzon-TURKEY.
E-mail: [email protected]
This journal is © The Royal Society of Chemistry 2008
levels struggle to learn chemistry, and many do not succeed
(Nakhleh, 1992). Research shows that from their first formal
exposure to chemistry, many students do not correctly
understand fundamental chemical concepts (Gabel et al.,
1987). Although there are many concepts with which students
have difficulty, chemical equilibrium is considered to be one
of the most difficult and important topics in the general
chemistry curriculum (Garnett et al, 1995; Quilez-Pardo and
Solaz-Portoles, 1995; Solomonidou and Stavridou, 2001),
owing to its abstract character and its demand of the mastery
of a large number of subordinate concepts (Quilez-Pardo and
Solaz-Portoles, 1995), and because of its essential role in
developing an understanding of other areas of chemistry such
as acid-base behavior, solubility, and oxidation-reduction
reactions (Voska and Heikkinen, 2000). Bilgin (2006) stated
that chemical equilibrium presents particular opportunities for
the development of alternative conceptions. Chemistry
teaching is textbook oriented and based on blackboard
presentations, and on chemistry problem solving using
algorithmic strategies. Students learn the taught rule by heart
and they try to apply it without understanding, fixating on the
pervasive set of reasoning rule-rote recalling algorithm
(Quilez, 2004a). Although these rules sometimes help to
answer the questions correctly, various empirical studies
concluded that students as well as teachers often use and
apply them erroneously (Bucat and Fensham, 1995). Because
the examinations are generally based on algorithmic problem
solving, students are passing examinations and continuing into
higher years of study with little conceptual understanding of
basic chemistry concepts. This weak understanding on basic
chemistry concepts lead to the development of alternative
conceptions at further educational level.
Chem. Educ. Res. Pract., 2008, 9, 225–233 | 225
A review of relevant literature
In the chemistry education literature, there have been
numerous studies concentrating on determining and
classifying students’ understanding related to chemical
equilibrium in the past three decades, and they indicate that
some students retain many alternative conceptions about this
concept (Bergquist and Heikkinen, 1990; Quilez-Pardo and
Solaz-Portoles, 1995; Thomas and Schwenz, 1998; Tyson et
al, 1999; Voska and Heikkinen, 2000; Solomonidou and
Stavridou, 2001; Chiu et al., 2002; Kousathana and Tsaparlis,
2002; Quilez, 2004a, b; Piquette and Heikkinen, 2005; Bilgin,
2006). Although these studies were conducted with subjects of
different age levels, similar alternative conceptions were
identified.
Although there is plenty of information on this in the
international literature, there are few studies focused on
determining students’ alternative conceptions at all levels on
this topic in Turkey, because teaching and learning chemistry,
and in general teaching and learning science, is a new
research area. Studies related to the determination of
alternative conceptions are generally focused on secondary
school students; studies involving university students are few.
To remedy this, we decided to study Turkish first year
university students’ alternative conceptions on chemical
equilibrium. In addition to the determination of the alternative
conceptions, possible methods to overcome them are
discussed in this study.
Method
Subjects
The subjects of this study were ninety prospective studentteachers in their first year of a four-year study in the
Department of Science Teacher Education. The study was
conducted at the end of the second semester in spring 2006.
All the students took Chemistry I and Chemistry II courses in
two semesters. Each course involved four 50 minutes lectures
and two 50 minutes laboratory sessions per week and was
compulsory for all undergraduate students in the first and
second-semester of the first year, respectively. All the
students enrolled on the courses had completed the study of
the chemical equilibrium concept, which was discussed in
fourteen 50-min lectures in Chemistry II in the second
semester. They also took Analytical Chemistry and Organic
Chemistry in the third and fourth semesters. There are no
chemistry courses in third and fourth years. Therefore,
Chemistry II is the last course in which chemical equilibrium
is taught.
Instrument
One of the methods to diagnose alternative conceptions is to
develop multiple choice responses to questions based on
students’ reasoning, including alternative conceptions. This
type of questions is called the two-tier multiple choice
question in related literature (Peterson et al., 1989). Such
questions allow researchers to determine the reason behind the
choice of the students and are readily available to teachers.
Accordingly,
the
Test
to
Identify
Students’
226 | Chem. Educ. Res. Pract., 2008, 9, 225–233
Table 1 Percentage of each response combination for item 4 on TISAC
Choice of
first tier
a
b
c
1
17.7
1.1
2.2
2
3.3
3.3
21.1
Reason (%)
3
–
15.5
–
4
32.2*
–
–
Total
53.2
19.9
23.3
Note: Question 4 was:
Consider the following reaction that is in a state of equilibrium in a blue
solution.
CoCl42-(aq) + 6H2O (l)
Co(H2O)62+(aq) + 4Cl-(aq)
pink
blue
What will be observed if water is added to this system?
(a) *the solution turns pink
(b) the solution becomes more blue
(c) the solution remains unchanged
Reason:
(1) to counter the increase in amount of water present the system will
form more Co(H2O)62+(aq)
(2) liquids are not included in the expression for K and hence the ratio of
products to reactants will not be disturbed
(3) the forward reaction has a higher mole ratio than the backward
(4)* the ratio of concentration of products compared to reactants as
expressed by Q will decrease and more Co(H2O)62+(aq) will form
*Correct choice and reason.
Alternative Conceptions (TISAC) was developed and used to
determine students’ alternative conceptions and learning
difficulties on the target concept in this study. The TISAC
includes 13 two-tier multiple choice questions, as originally
used by Peterson et al. (1989). The first tier consisted of a
content question in multiple-choice format with three choices.
The second tier consisted of four possible reasons for a
possible answer to the first part: three erroneous reasons and
one correct reason. In developing the process, while some of
the questions were taken from the literature (Tyson et al.,
1999) and used with minor revisions, some others (Voska and
Heikkinen, 2000; Huddle et al., 2000; Piquette and Heikkinen,
2005) were re-designed in accord with the two-tier multiple
choice format. The rest of the questions were developed by
the researcher. Table 1 offers an example of an item (Tyson et
al., 1999) that assesses understanding of the application of Le
Chatelier’s principle, as well as the item analysis.
Scoring the items
An item was scored as correct on the TISAC when both the
desired content and reason were selected. Items were
evaluated for both correct and incorrect response
combinations selected. For example, Table 2 shows response
combinations selected by the students in an item dealing with
the application of Le Chatelier’s principle. 32.2% of the
student teachers selected the desired correct answer
combination.
Results and discussion
Table 2 summarizes the characteristics of TISAC, and a copy
of the test is presented in Appendix. The reliability of the test
was estimated to be 0.71 using the Spearman-Brown formula
(Ferguson and Takane, 1989). The difficulty indices ranged
from 0.23 to 0.86, providing a wide range of difficulty items.
This journal is © The Royal Society of Chemistry 2008
Table 2 Characteristics of the Test to Identify Students’ Alternative
Conceptions (TISAC)
Areas
evaluated
Table 3 Percentages of content choice and correct combination
Items
1
2
3
4
5
6
7
8
9
10
11
12
13
Approach to equilibrium: items 3, 7 and 8
Application of Le Chatelier’s principle: items 4, 12 and 13.
Constancy of the equilibrium constant: items 1, 5 and 11
Heterogeneous equilibrium: items 2 and 9
Effect of a catalyst: items 6 and 10
Number of
13
items
Response Two-tier multiple-choice
format
First tier: content knowledge
Second tier: reason for the content response
Time to
25 to 35 minutes
complete test
Discrimination
Mean
range (items)
indices
0.48
0.30-0.39 (3)
0.40-0.49 (5)
0.50-0.59 (2)
0.60-0.69 (2
0.70-0.79 (1)
Difficulty
Mean
range (items)
indices
0.45
0.20-0.29 (2)
0.30-0.39 (2)
0.40-0.49 (4)
0.50-0.59 (2)
0.60-0.69 (1)
0.70-0.79 (1)
0.80-0.89 (1)
Spearman0.71
Brown
The discrimination indices ranged from 0.32 to 0.76. A value
of 0.30 was established as a minimum, and those greater than
0.30 were considered acceptable without the need for further
revision of the test items (Peterson et al., 1989). The content
validity of the test was established by a commission
consisting of a professor and three assistant professors in
chemistry education, and also five lecturers who teach
chemistry in a different department of the university.
Analysis of the results collected with the TISAC show that
students did not acquire a satisfactory understanding of the
chemical equilibrium concept. For the first tier of the test
items, the range of correct answer was 48.8% to 78.8% (Table
3). When both tiers were combined, the correct response was
reduced to a range of 22.2% to 48.8%.
As seen in Table 3, the percentages of correct responses to
the first parts of the questions (content choice) are generally
above 50%. Unfortunately, it is not possible to say same thing
for the correct answer combination. By referencing Gilbert
(1977), Odom and Barrow (1995) stated that if a multiplechoice item has four to five distractors, understanding is
considered satisfactory if 75% of the students answer the item
correctly. With a two-tier item with two selections on the first
tier and four selections on the second one, there is 8.3 %
chance of guessing the correct answer combination. Because
none of the student teachers scored above 75% on the correct
answer combination (Table 3), the results of the study suggest
that student teachers did not acquire a satisfactory
understanding of the chemical equilibrium concept.
t
This journal is © The Royal Society of Chemistry 2008
Content Choice
58.8
75.5
54.4
53.2
56.6
62.2
76.6
56.6
78.8
73.3
48.8
55.5
61.1
Combination
32.2
47.7
23.3
32.2
34.4
26.6
45.5
24.4
48.8
36.6
22.2
27.7
46.6
.
Table 4 Percentages of students’ alternative conceptions
Alternative Conceptions
Approach to equilibrium
Forward reaction goes to completion before the reverse
reaction starts
When there are equal concentrations of substances on both
sides of an equation, chemical equilibrium has been reached
The rate of forward reaction is greater than the reverse
reaction rate
Equilibrium reactions go on until all the reactants are
consumed
At equilibrium, no reaction occurs
Application of Le Chatelier’s principle
Le Chatelier’s principle can be applied in the initial state
before the reaction has reached equilibrium
When a substance is added to equilibrium mixture,
equilibrium will shift to the side of addition
When the temperature is changed, whether the reaction is
endothermic or exothermic does not affect the direction of
the equilibrium shift
When the temperature is increased, more products form
Constancy of the equilibrium constant
An increase in temperature always increases the numerical
value of Keq
Equilibrium constant, Keq, will increase with increasing
temperature in an exothermic reaction
When more products are added to an equilibrium system at
constant temperature, Keq will increase
The numerical value of Keq changes with amounts present of
reactants or products
Heterogeneous equilibrium
Le Chatelier’s principle can be applied in all systems,
including heterogeneous equilibrium systems
Increasing the amount of a solid ionic substance that is at
equilibrium causes more dissolved ions to be produced
% of
students
32.2
23.3
26.6
42.2
45.5
13.3
12.2
17.7
23.3
17.7
12.2
37.7
11.1
16.6
22.2
Seventeen alternative conceptions were identified through
analysis of items on the TISAC. These were grouped under
the headings: the application of Le Chatelier’s principle,
constancy of the equilibrium constant, heterogeneous
equilibrium, and effect of a catalyst. Table 4 shows the
proportions of the students showing them.
Chemical equilibrium is a difficult concept in which
students in all levels have alternative conceptions. Here,
students’ alternative conceptions are grouped under five
categories and discussed below in detail.
Chem. Educ. Res. Pract., 2008, 9, 225–233 | 227
Approach to equilibrium
In this research, 32.2% of students believed that forward
reaction goes to completion before the reverse one starts,
26.6% of them believed that the rate of forward reaction is
greater than the reverse reaction rate before and after the
equilibrium, which may be true until the equilibrium is
established but it is not true at equilibrium. 42.2% of them
believed that equilibrium reactions go on until all the
reactants run out, and 45.5% of them believed that no reaction
occurs at equilibrium (see Table 4). Similar alternative
conceptions were reported by Wheeler and Kass (1978),
Hackling and Garnett (1985), Banerjee (1991), and Griffiths
(1994). As time passes, reactants are being turned into
products and product is being turned into reactants at the same
rate (Russo and Silver, 2006). Based on this knowledge, we
conclude that the idea that the rate of forward reaction is
always greater than the reverse reaction, including at
equilibrium, which is held by 26.6% of the students, is an
alternative conception. In the literature, Hackling and Garnett
(1985) reported a similar finding. Similarly, Niaz (1995)
reported an alternative conception that after the reaction has
started, the rate of forward reaction increases with time and
that of the reverse reaction decreases, until equilibrium is
reached. These findings show that students do not have an
appropriate understanding about the equality of the rate of
forward and reverse reactions at equilibrium.
Another alternative conception is that when there are equal
concentrations of substances on both sides of an equation,
chemical equilibrium has been reached which is held by
23.3% of the participants. These students think that
concentrations of reactants and products become equal at
equilibrium. Hackling and Garnett (1985) and Huddle and
Pillay (1996) reported a similar alternative conception. This
idea may result from the explanation of equilibrium state
when, while explaining the equilibrium, we say that when the
rates of forward and reverse reactions become equal, dynamic
equilibrium is established, and there are no further changes in
concentrations (Russo and Silver, 2006). Probably students
interpret this statement that the concentration of reactants and
products become equal at equilibrium. As a result, the
concentrations themselves may vary, but the ratios between
the concentrations in a given situation do not.
Application of Le Chatelier’s principle
One of the alternative conceptions determined in this study is
that Le Chatelier’s principle can be applied in the initial state
before the reaction has reached equilibrium which is held by
13.3% of the participants. In the literature, Solomonidou and
Stavridou (2001) reported a similar alternative conception.
They stated that students made overextended use of the Le
Chatelier’s law, as they applied it in predicting the evolution
of a system of initial substances before the system had
reached chemical equilibrium. However, this principle is only
used when the system is at equilibrium. With this point,
another alternative conception of the students is that when a
substance is added to an equilibrium mixture, the equilibrium
will shift to the side of addition, which is held by 12.2% of
them. Moving from the Le Chatelier’s principle, we can say
228 | Chem. Educ. Res. Pract., 2008, 9, 225–233
that if we introduce more of one reactant, the reaction will
proceed to the right side that consumes this reactant, and vice
versa. This shows the erroneousness of the students’ ideas.
Another way to disturb equilibrium is to change the
temperature, and we can use Le Chatelier’s principle to
predict the direction of the shift. Two alternative conceptions
related to the effects of temperature change on a system at
equilibrium were determined. One of them is that when the
temperature is changed, whether the reaction is endothermic
or exothermic does not affect the direction of the equilibrium
shift, which is held by 17.7% of the student teachers, and the
other is that when the temperature is increased, more products
form, which is held by 23.3% of the participant. Voska and
Heikkinen (2000) reported a similar alternative conception
that when the temperature is changed, the direction of an
equilibrium shift can be predicted without knowing whether
the reaction is endothermic or exothermic.
Constancy of the equilibrium constant
Although students think that the numerical value of Keq
changes with amounts of reactants or products present, which
is held by 11.1% of them, we know that the numerical value
of the equilibrium constant for a reaction is the same for all of
the infinite number of equilibrium positions as long as the
temperature does not change. These students also think that
the numerical value of equilibrium constant depends on the
concentrations and changes with the amounts of reactants or
products present. Students also think that when more products
are added to an equilibrium system at constant temperature,
Keq will increase, which is held by 37.7% of them. Voska and
Heikkinen (2000) reported a similar alternative conception.
Three alternative conceptions were determined related to
the effect of temperature change on equilibrium conditions
and equilibrium constant. These are; an increase in
temperature always increases the numerical value of Keq,
which is held by 17.7%, equilibrium constant and equilibrium
constant, Keq, will increase with increasing temperature in an
exothermic reaction, which is held by 12.2% of the student
teachers. Similar alternative conceptions reported in the
related literature (Hackling and Garnett, 1985; Voska and
Heikkinen, 2000).
Heterogeneous equilibrium
Item 9 in TISAC was about the effect to the position of the
equilibrium and equilibrium constant of adding excess of a
solid reactant to a system at equilibrium. The CaCO3-CaOCO2 system is typical of heterogeneous equilibria. In this
item, students were asked about the effects of adding more
CaCO3 and CaO separately to the closed container at
equilibrium. Related to the two additions, two alternative
conceptions were identified. Firstly, 16.6% of the participants
believe that Le Chatelier’s principle can be applied in all
systems, including heterogeneous equilibrium systems. These
students applied Le Chatelier’s principle in both additions,
and arrived at the wrong conclusions. This alternative
conception has been reported in the literature (Wheeler and
Kass, 1978; Gorodetsky and Gussarsky, 1986; Banerjee, 1991;
Kousathana and Tsaparlis, 2002). Secondly, 22.2% of the
This journal is © The Royal Society of Chemistry 2008
students believed that increasing the amount of a solid ionic
substance that is at equilibrium causes more dissolved ions to
be produced. However, we know that adding or removing a
solid to the system at equilibrium does not change the
equilibrium state if the solid is present originally when the
system is in the equilibrium state (Umland, 1993).
Effect of a catalyst
Two similar alternative conceptions were identified in this
research. One of this is that a catalyst affects the rates of the
forward and reverse reactions differently, which is held by
22.2% of the participants, and the other is that a catalyst
speeds up only the forward reaction, which is held by 17.7%
of them. Similar alternative conceptions have been reported
previously (Hackling and Garnett, 1985; Gorodetsky and
Gussarsky, 1986; Voska and Heikkinen, 2000). Existence of
these
alternative
conceptions
reflects
incomplete
understanding by students of the existence of a common
reaction pathway and transition state for the forward and
reverse reactions.
Conclusion and implications for teaching
The study of the students’ answer to the test items revealed
that only a minority of them (22.2% to 48.8%) had
satisfactory conceptions and understanding about the chemical
equilibrium concept (see Table 3). Results show that students
had difficulties in representing and conceiving the dynamic
nature of chemical phenomena, and especially those involving
chemical equilibrium situations. A similar result has been
reported by Solomonidou and Stavridou (2001). According to
research data, participants have various alternative
conceptions ranging from 11.1% to 45.5%. A majority of
them had inappropriate understanding of the approach to
equilibrium, and they manifested serious difficulties in
conceiving the shift of equilibrium and the constancy of the
equilibrium constant, and they misapplied Le Chatelier’s
principle to explain the effects of temperature, concentration,
and catalyst. Although students took several chemistry
courses during their previous schooling in order to learn
various science concepts, including chemical equilibrium, the
presence of alternative conceptions in their explanations
indicates their fragmented understanding of these abstract
concepts. Research findings provide evidence that
misunderstandings of the concepts related to chemical
equilibrium are widespread at various levels of education,
including among prospective chemistry teachers (Pedrosa and
Dias, 2000).
What should we do to make teaching more effective and to
remediate alternative conceptions?
One of the most fruitful outcomes of the studies on students’
alternative conceptions is to alert teachers to students’
difficulties in conceptualizing science knowledge, and hence
suggest more effective strategies for improving classroom
instruction. Before teaching a concept such as chemical
equilibrium, for example, the teachers should be able to check
the literature to find out what is known about alternative
conceptions that students may bring to class, and which
This journal is © The Royal Society of Chemistry 2008
teaching methods are the best in correcting them. Once a
student’s particular alternative conceptions are identified, the
teacher can help her/him to achieve an understanding of the
scientifically accepted concept (Piquette and Heikkinen,
2005).
Because there are several alternative conceptions
determined in the literature related to chemical equilibrium,
alternative conceptions identified in this study may be less
important for an international audience than for a Turkish
audience. But, as stated by Quilez-Pardo and Solaz-Portoles
(1995), although there are many alternative conceptions
determined and known, research results have little effect on
the actual classroom practice, and many chemistry teachers
continue to teach their subjects as if none of these researches
had been undertaken and, as a result of this, there is a gap
between research and teaching. The key problem is that
teachers expect research to be presented to them in a form
they can readily apply because they are too busy doing their
job to read the research literature (De Jong, 2000). For this
reason, to explore and use research findings to improve
chemistry learning, it is important to develop diagnostic
instruments as well as improving curricular resources and
teaching approaches.
Studies indicate that students experience difficulty in
understanding
the
submicroscopic
and
symbolic
representations because these representations are abstract and
can not be experienced (Griffiths and Preston, 1992;
Chandrasegaran et al., 2007). Students often are not able to
translate one given representation into another because of
their limited conceptual knowledge and poor visual-spatial
ability (Keig and Rubba, 1993). For example, traditional
teaching methods cannot supply to student the adequate
representations of systems of substances at equilibrium related
to empirical and the atomic level, manifested serious
difficulties in conceiving the initial situation of a system at
chemical equilibrium and the equilibrium shift. For improved
conceptual understanding, it is important to help students see
the connections between the submicroscopic, symbolic and
macroscopic representations (Gabel, 1999).
The goal of most science education researchers is to help
students to learn science subjects in the most appropriate way
(Bilgin and Geban, 2006). There are a few convenient ways of
this when describing and explaining chemical phenomena,
especially
chemical
equilibrium.
Computer-assisted
instruction, simulations, conceptual change strategies,
analogy, laboratory activities, and etc. are among these
(Dagher, 1994; Chambers and Andre, 1997; Huddle et al.,
2000; Özmen, in press). One of the most important of them is
computer-assisted instruction. Computer software may contain
simulations and visualizations of experiments representing
systems at chemical equilibrium, and simulations of chemical
reactions related to atomic and symbolic levels. These
simplify visualization of the abstract concepts by the students.
Özmen (2008) suggests that teaching-learning of topics in
chemistry can be improved by the use of computer-assisted
instruction. Huddle et al. (2000) reported that brighter
students benefited greatly from the equilibrium games, in
which computer software addresses most of the major known
Chem. Educ. Res. Pract., 2008, 9, 225–233 | 229
alternative conceptions in chemical equilibrium, and includes
simulations. Computers may simplify doing experiments
related to chemical equilibrium and students may understand
abstract concepts such a way. In addition, the effects of the
different factors on equilibrium may be seen by doing
experiments and applications in a virtual environment. Since
most of the computer software is interactive, this creates
necessary opportunities for the students in terms of ‘doing and
learning’. Teachers can help students eliminate their
alternative conceptions by providing an adequate knowledge
base and clear understanding of these concepts by this way.
Another way of effective teaching is conceptual change
strategies. Conceptual change texts are one of the conceptual
change strategies and are used for changing students’
alternative conceptions, and focus on strategies to promote
conceptual change by challenging students’ alternative
conceptions, producing dissatisfaction, followed by a correct
explanation which is both understandable and plausible to the
students. In the literature, many studies in science education
relate to conceptual change text, including chemistry concepts
such as acids and bases, electrochemistry, solutions (Wang
and Andre, 1991; Yürük and Geban, 2001; Cakir et al., 2002;
Calik et al., 2007) and emphasize their effectiveness.
Although there are no studies that focus specifically on the
investigation of the effect of conceptual change texts on
students’ understanding of chemical equilibrium, personal
experience of the author in general chemistry lessons shows
that conceptual change texts may be very effective in the
teaching of such concepts. Preliminary observations,
experience and unpublished studies of the author confirm this
idea. Therefore, conceptual change texts, especially focused
on students’ alternative conceptions in chemical equilibrium,
should be developed and used in teaching these concepts.
Literature states that such texts are apparently particularly
effective in group-learning situations (Guzzetti et al., 1997).
And also, Bilgin and Geban (2006) reported the positive effect
of a cooperative learning approach based on conceptual
change condition on students’ understanding of chemical
equilibrium concepts. The amalgamation of the conceptual
change texts and cooperative group learning may be an
alternative way for effective teaching of chemical equilibrium
concepts.
Laboratory activity is another teaching way used in science
teaching. The literature suggests that students enjoy
laboratory work because it is more active, something they find
more motivating (Hart et al., 2000) and students have a
chance to engage in hands-on activities. Both science and
non-science majors are reported to find laboratory-based
activities to be motivating and exciting (Markow and
Lonning, 1998). There have been many studies reporting on
the effectiveness of the laboratory instruction (Hart et al.,
2000; Özmen et al. in press), and many authors believe that
laboratory work helps to promote conceptual change.
Therefore, laboratory activities should also be used to teach
some abstract concepts related to chemical equilibrium. For
example, the experiment of chromate/dichromate equilibrium
may be used to teach the application of the Le Chatelier’s
principle.
230 | Chem. Educ. Res. Pract., 2008, 9, 225–233
Finally, future researchers in collaboration with teachers
and curriculum developers should develop new teaching
materials about the chemical equilibrium and implement them
in classrooms in an experimental setting, so that they may
better understand the effects of different teaching techniques
and materials on alternative conceptions. Although the related
literature indicates that there is resistance to changing existing
conceptions in children’s mind, we cannot sit back and wait
for the misconceptions to be turned into the scientific
concepts without any effort.
Appendix
Items used in TISAC:
1. The following hypothetical reaction reaches equilibrium at 25ºC:
C (g) + D (g) . Once equilibrium has been reached, the
A(g) + B (g)
concentration of C is increased by the addition of more C. Assume that
the temperature remains constant. Which of the following can be said
about the numerical value of the equilibrium constant?
(a) decreases
(b) increases
(c) *remains unchanged
Reason
(1) the rate of reverse reaction increases and the rate of the forward
reaction decreases
(2) the rate of reverse reaction increases and the rate of forward
reaction stays the same
(3) *the ratio between products’ concentrations and reactants’
concentrations is constant at constant temperature
(4) the concentration of the products has been increased
2. Limestone decomposes to form quicklime and carbon dioxide as
CaO (s) + CO2 (g). What can we say about any
follow: CaCO3 (s)
equilibrium shift after removing some solid CaCO3 from the equilibrium
mixture?
(a) shift to the reactants’ side
(b) *will not shift the equilibrium
(c) will not be predictable
Reason
(1) the amount of CaCO3 is increased in the system and a new
equilibrium is established
(2) *because CaCO3 is solid, removing it does not affect the
equilibrium
(3) CO2 and CaO react to form more CaCO3 according to Le
Chatelier’s principle
(4) the amount of solid CaCO3 removed is not known
3. Carbon monoxide and hydrogen react according to the following
CH4 (g) + H2O (g) When 0.02 M CO and
equation. CO (g) + 3H2 (g)
0.03 M H2 are introduced into a vessel at 800 K and allowed to come to
equilibrium, what can we say about the rate of reverse and forward
reactions at equilibrium?
(a) *the rates are equal
(b) forward reaction rate is greater than the reverse one
(c) reverse reaction rate is greater than the forward one
Reason
(1) forward reaction goes to completion before the reverse reaction
starts
(2) *the rates of the forward and reverse reactions are equal when the
system reaches equilibrium
(3) as time passes, the concentrations of products increase
(4) at the beginning, the concentrations of the reactants are greater than
the concentrations of products
4. Consider the following reversible reaction that is in a state of
equilibrium in a blue solution.
CoCl42- (aq) + 6H2O (l)
Co(H2O)62+ (aq) + 4Cl- (aq)
pink
blue
What will be observed if water is added to this system?
(a) *the solution turns pink
(b) the solution becomes more blue
(c) the solution remains unchanged
Reason
This journal is © The Royal Society of Chemistry 2008
(1)
to counter the increase in the amount of water present the system
will form more Co(H2O)62+(aq)
(2) liquids are not included in the expression for K and hence the ratio
of products to reactants will not be disturbed
(3) the forward reaction has a higher mole ratio than the backward
(4) * the ratio of concentration of products compared to reactants as
expressed by Q will decrease and more Co(H2O)62+(aq) will form
5. In the first step of the Ostwald process for the synthesis of nitric
acid, ammonia is oxidized to nitric oxide by the reaction:
4NH3 (g) + 5O2 (g)
4NO (g) + 6H2O (g) , ∆H = - 905.6 kJ/mole. How
does the equilibrium constant vary with an increase in temperature?
(a) increases
(b) *decreases
(c) remains the same
Reason
(1) an increase in temperature always increases the numerical value of
Keq
(2) because the reaction is exothermic, the concentration of product
increases
(3) *the equilibrium will shift to the left with an increase in
temperature
(4) whether the reaction is endothermic or exothermic does not affect
the Keq
6. Sulphur dioxide and oxygen react to form sulphur trioxide in the
2SO3 (g). ∆H = - 197.78
following reaction: 2SO2 (g) + O2 (g)
kJ/mole. What can we say about the forward reaction rate compared with
the reverse reaction rate if a catalyst is added to system?
(a) higher
(d) lower
*(c) the same
Reason
(1) a catalyst increases the collisions between reactants’ particles and
produces more product
(2) *a catalyst lowers the activation energy for the forward and reverse
reactions by exactly the same amount
(3) a catalyst affects the rates of the forward and reverse reactions
differently
(4) because more products are produced, the reverse one speeds up
7. The equilibrium between sulphur dioxide gas, oxygen gas and
sulphur trioxide gas is as follows:
2SO3 (g) . If the reaction starts with the
2SO2 (g) + O2 (g)
concentration of 0.02 M SO2, 0.01 M O2 and 0.00 M SO3, and reaches
equilibrium at a constant temperature, what can we say about the
equilibrium concentrations of SO2 gas and O2 gas?
(a) *decrease
(b) become zero (c) remain unchanged
Reason
(1) equilibrium reactions go on until all of the reactants run out
(2) concentrations are constant because no reaction occurs at
equilibrium
(3) *as time passes, SO2 and O2 reactants are consumed, decreasing
their concentrations
(4) this system does not reach equilibrium because there is no SO3 at
the beginning
8. Suppose that 0.30 mol PCI5 is placed in a reaction vessel of volume
1000 mL and allowed to reach equilibrium with its decomposition
products: phosphorus trichloride and chlorine at 250ºC, when K eq= 1.8
PCI3(g) + CI2(g) . What can we say about the
for PCI5 (g)
concentration of the PCI3 gas and CI2 gas at equilibrium?
(a) higher than 0.30 M (b) *lower than 0.30 M (c) equals to 0.30 M
Reason
(1) concentrations of all species in the reaction mixture are equal at
equilibrium
(2) all the phosphorus pentachloride turns into the products
(3) *phosphorus pentachloride decomposes to an extent less than 100%
to produce phosphorus trichloride and chlorine
(4) because the total moles of the products is higher than the reactants’
ones
9. Calcium carbonate decomposes to form calcium oxide and carbon
CaO(s) + CO2 (g)
dioxide according to the equation: CaCO3 (s) + heat
After the system reaches equilibrium in a closed container, extra solid
CaCO3 is added to the equilibrium mixture. What will happen to the
concentration of carbon dioxide after addition?
(a) increases
(b) decreases
(c) *remains unchanged
Reason
(1) increasing the amount of CaCO3 (s) that is at equilibrium causes
more dissolved ions to be produced.
This journal is © The Royal Society of Chemistry 2008
because CaCO3 (s) is added to the reactants’ side, equilibrium will
shift the products’ side
(3) because CaCO3 (s) is added to reactants’ side, equilibrium will shift
the reactants’ side
(4) *the concentrations of pure solids, that is, the quantities in a given
volume or densities, are constant
10. Carbon monoxide reacts with oxygen to form carbon dioxide in
accordance with following reaction.
2CO2 (g), ∆H = - 566 kJ/mole. Suppose that you
2CO (g) + O2 (g)
have a reaction vessel containing an equilibrium mixture of [CO] = 0.30
M, [O2] = 0.20 M and [CO2] = 0.25 M. What will happen to the
concentration of CO2 if a catalyst is added to the equilibrium mixture?
(a) will be higher than 0.25
(b) will be lower than 0.25
*(c)
will be equal to 0.25
Reason
(1) a catalyst speeds up the forward reaction, increases the collision
between reactants’ particles and produces more product
(2) both the amounts of reactants and the amounts of products increase
(3) * a catalyst has no effect on the equilibrium composition of a
reaction mixture
(4) because a catalyst lowers the activation energy, more reactants turn
into the product
11. Consider the gaseous reaction of hydrogen with iodine;
2HI (g) . Suppose that we have a mixture of H2 (g) and I2
H2 (g) + I2 (g)
(g) at 700 K with the initial concentrations [H2] = 0.1 M and [I2] = 0.2 M.
When the system reaches equilibrium, the numerical value of equilibrium
constant equals, K eq = 57.0. If the initial concentration is 0.3 M H2 and 0.
3 M I2, what would say the numerical value of Keq when the system
reaches equilibrium?
(a) increases
(b) decreases
(c) *remains the same
Reason
(1) an increase in the concentrations of the reactants increases the
concentrations of the products
(2) *the numerical value of K eq does not depend on the initial
concentrations of the reactants
(3) the numerical value of K eq changes with amounts present of
reactants
(4) because more product will form, the numerical value of K eq
changes with the same ratio
12. If you have a 0.5 M solution of sodium dichromate (Na2Cr2O7) in
which the following equilibrium is established
Cr2O72— (aq) + H2O(l)
2CrO42— (aq) + 2H+ (aq)
yellow
orange
and you add 10 mL of 0.5 M solution of sodium dichromate to the
original solution what would you observe?
(a) the solution becomes yellow
(b) the solution becomes deeper orange
(c) *the solution remains unchanged
Reason
(1) to counteract the increased amount of Cr2O72— (aq) the system will
form more CrO42— (aq)
(2) there will be more collisions between particles of Cr2O72— (aq) and
H2O(l)
(3) *there is no change in the concentration of any species
(4) because of increase in Cr2O72—, Q will be greater than Keq
13. Consider the following reversible reaction that is in a state of
equilibrium.
N2 (g)+3H2 (g)
2NH3 (g) , ∆H = - 92.4 kJ/mole
(2)
If the temperature of the system is increased, the equilibrium position will
(a) *shift to the left (b) shift to the right (c) remain unchanged
Reason
(1) when the temperature is increased, more products form
(2) *if the temperature is increased, more reactants are formed
(3) when the temperature is changed, whether the reaction is
endothermic or exothermic does not affect the direction of the
equilibrium shift
(4) temperature changes do not affect the system that is at equilibrium.
Chem. Educ. Res. Pract., 2008, 9, 225–233 | 231
References
Banerjee A. C., (1991), Misconceptions of students and teachers in
chemical equilibrium, Int. J. Sci. Educ., 13, 487-494.
Bergquist W. and Heikkinen H., (1990), Student ideas regarding chemical
equilibrium, J. Chem. Educ., 67, 1000-1003.
Bilgin I., (2006), Promoting pre-service elementary students’
understanding of chemical equilibrium through discussion in small
groups, Int. J. Sci. Math. Educ., 4, 467-484.
Bilgin I. and Geban O., (2006), The effect of cooperative learning
approach based on conceptual change condition on students’
understanding of chemical equilibrium concepts, J. Sci. Educ. Tech.,
15, 31-46.
Bucat B. and Fensham P., (1995), Teaching and learning about chemical
equilibrium, In Selected papers in chemical education research, pp.
167-171. IUPAC-Committee on Teaching Chemistry. Delhi: IUPACShatabdi Computers.
Calik M., Ayas A. and Coll R. K., (2007), Enhancing pre-service
elementary teachers’ conceptual understanding of solution chemistry
with conceptual change text, Int. J. Sci. Math. Educ., 5, 1-28.
Cakir Ö. Uzuntiryaki E. and Geban O., (2002), Contribution of
conceptual change texts and concept mapping to students’
understanding of acids and bases. Paper presented at the Annual
Meeting of the National Association for Research in Science
Teaching, April 6-10, 2002, New Orleans, LA.
Chambers S. and Andre T., (1997), Gender, prior knowledge, interest and
experience in electricity and conceptual change text manipulations in
learning about direct current, J. Res. Sci. Teach., 34, 107-123.
Chandrasegaran A. L., Treagust D. F. and Mocerino M., (2007), The
development of a two-tier multiple-choice diagnostic instrument for
evaluating secondary school students’ ability to describe and explain
chemical reactions using multiple levels of representation, Chem.
Educ. Res. Pract., 8, 293-307.
Chiu M. H., Chou C. C. and Liu C. J., (2002), Dynamic processes of
conceptual change: analysis if constructing mental models of
chemical equilibrium, J. Res. Sci. Teach., 39, 688-712.
Dagher Z., (1994), Does the use of analogies contribute to conceptual
change? Sci. Educ.,78, 601-614.
De Jong O., (2000), Crossing the borders: chemical education research
and teaching practice, U. Chem. Educ., 4, 29-32.
Ferguson G. A. and Takane Y., (1989), Statistical Analysis in Psychology
and Education, McGraw-Hill, New York.
Gabel D., (1999), Improving teaching and learning through chemistry
education research: a look to the future, J. Chem. Educ., 76, 548-554.
Gabel D. L., Samuel K. V. and Hunn D., (1987), Understanding the
particulate nature of matter, J. Chem. Educ., 64, 695-697.
Garnett P. J., Garnett P. J. and Hackling, M. W., (1995), Students’
alternative conceptions in chemistry: a review of research and
implications for teaching and learning, Stud. Sci. Educ., 25, 69-95.
Gilbert J. K., (1977), The study of student misunderstandings in the
physical sciences, Res. Sci. Educ., 7, 165-171.
Gonzalez F. M., (1997), Diagnosis of Spanish primary school students’
common alternative science conceptions, Sch. Sci. Math., 97, 68.
Gorodetsky M. and Gussarsky E., (1986), Misconceptualization of the
chemical equilibrium concept as revealed by different evaluation
methods, Eur. J. Sci. Educ., 8, 427-441.
Griffiths A. K., (1994), A critical analysis and synthesis of research on
students’ chemistry misconceptions, in Schmidt, H.-J. (ed).
Proceedings of the 1994 International Symposium Problem Solving
and Misconceptions in Chemistry and Physics, pp. 70-99. The
International Council of Association for Science Education
Publications.
Griffiths A. K. and Preston K. R., (1992), Grade-12 students’
misconceptions relating to fundamental characteristics of atoms and
molecules, J. Res. Sci. Teach., 29, 611-628.
Guzzetti B. J., Williams W. O., Skeels S. A. and Wu S. M., (1997),
Influence of text structure on learning counter-intuitive physics
concepts, J. Res. Sci. Teach., 34, 701-709.
232 | Chem. Educ. Res. Pract., 2008, 9, 225–233
Hackling M. W. and Garnett P. J., (1985), Misconceptions of chemical
equilibrium, Eur. J. Sci. Educ., 7, 205-214.
Hart C., Mulhall P., Berry A., Loughran J., and Gunstone R., (2000),
What is the purpose of this experiment? Or can students learn
something from doing experiments? J. Res. Sci. Teach., 37, 655-675.
Huddle P. A. and Pillay A. E., (1996), An in-depth study of
misconceptions in stoichiometry and chemical equilibrium at a South
African University, J. Res. Sci. Teach., 33, 65-77.
Huddle P. A., White M. W. and Rogers F., (2000), Simulations for
teaching chemical equilibrium, J. Chem. Educ., 77, 920-926.
Keig P. F. and Rubba P. A., (1993), Translations of the representations of
the structure of matter and its relationship to reasoning, gender,
spatial reasoning, and specific prior knowledge, J. Res. Sci. Teach.,
30, 883-903.
Kousathana M. and Tsaparlis G., (2002), Students’ errors in solving
numerical chemical-equilibrium problems, Chem. Educ. Res. Pract.,
3, 5-17.
Markow P.G. and Lonning R.A., (1998), Usefulness of concept maps in
college chemistry laboratories: students’ perceptions and effects on
achievement, J. Res. Sci. Teach., 35, 1015-1029.
Nakhleh M. B., (1992), Why some students don’t learn chemistry?
Chemical misconceptions, J. Chem. Educ., 69, 191-196.
Niaz M., (1995), Relationship between student performance on
conceptual and computational problems of chemical equilibrium, Int.
J. Sci. Educ., 17, 343-355.
Odom A. L. and Barrow L. H., (1995), Development and application of a
two-tier diagnostic test measuring college biology students’
understanding of diffusion and osmosis after a course of instruction,
J. Res. Sci. Teach., 32, 45-61.
Özmen H., (2004), Some students` misconceptions in chemistry: a
literature review of chemical bonding, J. Sci. Educ. Tech., 13, 147159.
Özmen H., (2008), The influence of computer-assisted instruction on
students’ conceptual understanding of chemical bonding and attitude
toward chemistry: a case for Turkey, Comp. Educ., 51, 423-438
Özmen H., Demircioğlu G. and Coll R.K., (in press), A comparative
study of the effects of a concept mapping enhanced laboratory
experience on Turkish high school students’ understanding of acidbase chemistry, Int. J. Sci. Math. Educ.
Palmer D., (1999), Exploring to link between students’ scientific and
nonscientific conceptions, Sci. Educ., 83, 639-653.
Pedrosa M. A. and Dias M. H., (2000), Chemistry textbook approaches to
chemical equilibrium and student alternative conceptions, Chem.
Educ. Res. Pract., 1, 227-236.
Peterson R., Treagust D. F. and Garnett P., (1989), Development and
application of a diagnostic instrument to evaluate grade-11 and -12
students’ concepts of covalent bonding and structure following a
course of instruction, J. Res. Sci. Teach., 26, 301-314.
Pines L. and West L., (1986), Conceptual understanding and science
learning: an interpretation of research within a source of knowledge
framework, Sci. Educ., 70, 583-604.
Piquette J. S. and Heikkinen H. W., (2005), Strategies reported used by
instructors to address student alternate conceptions in chemical
equilibrium, J. Res. Sci. Teach., 42, 1112-1134.
Posner G. J., Strike K. A., Hewson P. W. and Gertzog W. A., (1982),
Accommodation of a scientific conception: towards a theory of
conceptual change, Sci. Educ., 66, 211-217.
Quilez J., (2004a), Changes in concentration and in partial pressure in
chemical equilibria: students’ and teachers’ misunderstandings,
Chem. Educ. Res. Pract., 5, 281-300.
Quilez J., (2004b), A historical approach to the development of chemical
equilibrium through the evolution of the affinity concept: some
educational suggestions, Chem. Educ. Res. Pract., 5, 69-87.
Quilez-Pardo J. and Solaz-Portoles J., (1995), Students’ and teachers’
misapplication of Le Chatelier’s principle: implications for the
teaching of chemical equilibrium, J. Res. Sci. Teach., 32, 939-957.
Russo S. and Silver M., (2006), Introductory Chemistry, Pearson
Benjamin Cummings, Third Edition, San Francisco.
Solomonidou C. and Stavridou H., (2001), Design and development of a
computer learning environment on the basis of students’ initial
This journal is © The Royal Society of Chemistry 2008
conceptions and learning difficulties about chemical equilibrium,
Educ. Inf. Tech., 6, 5-27.
Southerland S. A., Abrams E., Cummins C. L. and Anzelmo J., (2001),
Understanding students’ explanations of biological phenomena:
conceptual frameworks or P-prims?, Sci. Educ., 85, 328-348.
Taber K. S., (2000), Chemistry lessons for universities?: A review of
constructivist ideas, U. Chem. Educ., 4, 63-72.
Taber K. S., (2001), Constructing chemical concepts in the classroom:
using research to inform the practice, Chem. Educ. Res. Pract., 2, 4351.
Taber K. S., (2002), Chemical misconceptions: prevention, diagnosis and
cure. Vol. I, Theoretical Background, Vol. II, Classroom Resources.
Royal Society of Chemistry, London.
Thomas P. L. and Schwenz R. W., (1998), College physical chemistry
students’
conceptions
of
equilibrium
and
fundamental
thermodynamics, J. Sci. Educ. Tech., 35, 1151-1160.
Tyson L., Treagust D. F. and Bucat R. B., (1999), The complexity of
teaching and learning chemical equilibrium, J. Chem. Educ., 76, 554558.
This journal is © The Royal Society of Chemistry 2008
Umland J. B., (1993), General chemistry. West Publishing Company,
USA.
Voska K. W. and Heikkinen, H. W., (2000), Identification and analysis of
students’ conceptions used to solve chemical equilibrium problems,
J. Res. Sci. Teach., 37, 160-176.
Wang T. and Andre T., (1991), Conceptual change text versus traditional
text and application questions versus no questions in learning about
electricity, Cont. Educ. Psych., 16, 103-116.
Wheeler A. E. and Kass H., (1978), Student misconceptions in chemical
equilibrium, Sci. Educ., 62, 223-232.
Yürük N. and Geban Ö., (2001), Conceptual change text: a supplementary
material to facilitate conceptual change in electrochemical cell
concepts, Paper presented at the Annual Meeting of the National
Association for Research in Science Teaching, March, 25-28, 2001
St. Louis, MO.
Chem. Educ. Res. Pract., 2008, 9, 225–233 | 233