As simple as making hot dogs: Using analogies to teach limiting and excess reagents in high school chemistry

Cleo Christie-David

Barker College Analogies are commonly used to communicate complex, and often abstract, topics in science education. There is limited research into the effect of analogy on how students respond to exam-style questions. This research investigates the potential benefit of using analogy as a teaching model in chemistry with a controlled study involving 34 Year 10 students at a co-educational independent high school in Sydney, Australia. One video used the analogies of hot dogs and burgers, and the other video relied solely upon traditional chemistry examples to explain the concept of limiting and excess reagents. The students were asked exam style questions which required them to recall and explain limiting and excess reagents qualitatively and answer practical questions quantitatively. Although the literature suggested that analogy would have more positive effects, the results failed to enhance this claim. Whilst there were somewhat higher levels of sophistication in responses from the analogy treatment, it was not enough to suggest that analogical reasoning was more beneficial than traditional methods but presents avenues for further research

Literature Review

Analogy is an effective tool used in education which involves giving real-life examples to enable students to understand abstract ideas, especially in the sciences. Analogies can be tools of both discovery and the transfer of knowledge as they evoke mental images that are concrete for unsophisticated thinkers (Aubusson, Treagust & Harrison, 2009; Harrison & Treagust, 1993). For example, the recipe of a hot dog from the components of a sausage and bun can become an analogy for the reactants and products in a chemical reaction. Analogies can be valuable tools in conceptual learning by facilitating a cognitive understanding of the abstract to welcome higher-order thinking (Duit, 1991; Richland & Simms, 2015; Sutula & Krajcik, 1988).

Successful use of analogy

For an analogy to be successful, there must be correspondence between the analogy and the abstract idea involving similar features relating to either “concepts, principles or formulas” (Glynn et al., 1989, p.383). The correspondence is a form of mapping one idea to another with a systematic comparison, either verbally or visually between common and uncommon features (Aberšek, 2016; Aubusson et al., 2009). Through this mapping, analogies allow what is familiar to be used to make the “unfamiliar accessible and understandable” (Aubusson et al., 2009, p.212; Richland & Simms, 2015). For example, the winds of a bird can be used as an analogy for how the wings of a plane work or the human eye is analogous to how a camera operates.

Unsuccessful use of analogy

However, analogies can also create misconceptions where there are differing and misleading features between the abstract and target knowledge (Champagne et al., 1985; Dilber & Bahattin, 2008; Thiele & Treagust, 1992), or where students are unfamiliar with the analogy (Gentner & Gentner, 1983; Nagel, 1961). Orgill and

Figure 1: Incorporation of analogy in new knowledge (Source: Thiele & Treagust, 1992)

Bodner (2004) suggest that the transfer of irrelevant components, i.e. analogies, between the existing and target knowledge domains can cause the development of misconceptions, which sees students incorporate the analogy into their response. This leads to the argument that analogies are not as useful in the classroom as the literature suggests and as expected (Duit, 1991; Harrison & Treagust, 1993).Thiele and Treagust (1992) have modelled the distinction between a desired and undesired effect of analogies in supporting the formation of target knowledge from existing knowledge (Figure 1). Dilber and Bahattin (2008) elaborate on the undesirable effects when students are unable to separate the analogy from the target and conceptual knowledge becomes incorrect. To exemplify the difference between the desired and undesired effect, if you were to use the analogy of ‘time is money’; the desired effect would be to find the similarities between time and money i.e. that it is valuable and can be wasted; the undesired effect would be to not distinguish the differences and assume that time itself has a monetary value. Harrison and Treagust (1993) explain that these alternative conceptions cause students to visualise the concept in a different matter to what is intended by the teachers, and due to the visual nature are left unchallenged. Such the use of analogies in teaching must address the teaching method rather than the individual thought process of the student (Harrison & Treagust, 1993).

Effective teaching using analogy

Research is limited as educational research on analogy only became a significant field in the late 1980s (Aubusson et al., 2009). There has been little experimental research on the way students draw on analogy in the absence of a teacher (Aubusson et al., 2009; Duit, 1991; Thiele & Treagust, 1992), hence, examination style questions will be used as a post-test in this present study. However, the question remains on whether analogies are both interpreted and applied in the way in which they are intended by educators. The currently supported view by academics is that “when learners construct their own knowledge, it is both transferable to and usable in later learning situations” (Thiele & Treagust, 1992, p.3; Sutula & Krajcik, 1988). The relational reasoning of analogy is considered by Richland and Simms (2015) to be the “cognitive underpinning of higher order thinking”, promoting advanced reasoning (p. 177). According to Fredricks et al. (2004), it is thought that in constructing one’s own knowledge, their cognitive engagement will promote a deeper understanding as well as a willingness to further the complexity. Engagement is imperative in instilling the “willingness to exert the effort necessary to comprehend complex ideas and master difficult skills" (Fredricks et. Al, 2004, p.60). Such the increased engagement when using analogy in classroom instruction can have benefits on the motivation and dedication of students in education (Fredricks et. Al, 2004; Richland & Simms, 2015).

Analogies and Chemistry Education

Analogies can be particularly helpful in science due to the highly abstract nature of theories and models (Harrison & Treagust, 1993; Nagel, 1961; Muniz & Oliver-Hoyo, 2014; Richland & Simms, 2015). They can serve as “initial models, or simple representations, of scientific concepts” which drive as both inspiration and explanations for scientific discovery (Aberšek, 2016, p. 4; Kaiser, 1989). Analogies engage students in scientific thinking in classroom settings through learning and teaching as well as textbooks (Aberšek, 2016; Richland & Simms, 2015; Metsala & Glynn, 1996; S˛endur et. al, 2011). Analogy is generally considered beneficial in chemistry education as it can be “utilized as motivation for the connection of concepts such that students create and maintain a rich, holistic viewpoint of science overall" (Muniz & Oliver-Hovo, 2014, p. 25). In chemistry education, analogies are particularly helpful in providing a bridge between unfamiliar and abstract concepts and preconceived knowledge (Thiele & Treagust, 1992). Chemistry often deals with scientific phenomena such as particles, energy and matter which are invisible to the naked eye and unfamiliar (Aubusson et al., 2009; Dilber & Bahattin, 2008; Duit, 199; Muniz & Oliver-Hoyo, 2014; Richland & Simms, 2015). Often visualisations are used to help students with these concepts, however, without the “aligning and mapping between this representation and the natural phenomenon,” can fail to be as effective as analogical reasoning (Richland & Simms, 2015, p. 185). In a chemistry education context, the desired model of bridging analogy gives students the opportunity to develop inferences, prompts conceptual change and moves from original ideas about a target phenomenon to reformulate them based on comparison with the analogy itself (Richland & Simms, 2015). The concept of limiting and excess reagents was chosen as it is a topic that is typically taught through the simple analogy of a recipe. Analogical reasoning of a recipe appeals to all as it is not a niche analogy and such it is easily understood and brief. Limiting and excess reagents is also a preliminary topic, and such, the Year 10s did not have any prior knowledge on the topic that would compel the sophistication of their answers.

Scientific research question

When learning high school chemistry content with analogy, it is more beneficial than learning chemistry traditionally?

Scientific hypothesis

That in incorporating analogy into instruction on limiting and excess reagents, in high school chemistry, will lead to a positive difference in how they answer exam-style questions.

Methodology

Two different video lessons introducing the Chemistry content of limiting and excess reagents were presented to two randomly selected groups of Year 10 students at a co-educational independent high school in Sydney, Australia – one video involved analogy (Video A: Analogy), whilst the other was traditionally scientific (Video B: Traditional).

Instructional Material

Both videos explained the concept of limiting and excess reagents, sharing the same explanations and chemical examples, whilst Video B (Traditional) used solely chemical examples, Video A (Analogy) used an analogy of constructing hot dogs and burgers from their constituent parts. To ensure that the same scientific terms were used, parts of the videos were identical. The videos were both between 6:30 and 7:30 minutes in length to approximately mitigate the variable of time and were presented by the same Chemistry teacher. A detailed summary of the identical and corresponding content can be found in Figure 2 and full videos are available on YouTube.1

Implementation

34 Year 10 students were chosen as they would not yet have encountered limiting reagents in science. During a Science class, students followed a link which randomly assigned them to either the analogy or traditional video which they watched on their own device. In order to investigate the realities of analogy use in exam-question situation after the video, all students then participated in an identical post-test with a combination of both quantitative and qualitative questions that challenged their knowledge and understanding of the concept. Two key questions are included in Figure 3.

1 Video A: http://bit.ly/BCChemistryA Video B: http://bit.ly/BCChemistryB

Analysis methodology

The responses were then collected, randomized and declassified from treatment and control, in order to avoid confirmation bias when the results were reviewed. The quantitative answers and simpler qualitative responses were marked either correctly or incorrectly. The main qualitative response, where students were asked to “Explain how to find the limiting and excess reagents in chemistry”, was assessed on sophistication through the criteria of the accuracy, length and depth of the responses and given a mark out of 5. Finally, the responses were re-identified as being completed by students who had watched the analogy and traditional chemistry videos, and strong differences or similarities were sought, particularly associated with the desired and undesired effect from Thiele & Treagust’s 1992 model. The quantitative data was used to make graphs and averages in order to identify immediate trends.

Results

Answers to exam-style questions

When given a question of similar difficulty to the examples in the videos, 15 students in the analogy treatment were able to find the limiting reagent, however, only 13 could both name the excess reagent and calculate how many atoms of the reagent would be left over. The traditional treatment saw similar numbers where again 15 students could find the limiting reagent, whilst only 12 could find the excess reagent.

Students were asked in part B of the extension question “Which is the excess reactant, and how many atoms will be remaining once the reaction has completed as much as possible”. Only 2 students from the traditional treatment were able to answer both the excess reagent and the number of atoms remaining correctly. It is not enough evidence to say that Video B was more beneficial as there were also two respondents from the traditional treatment that failed to answer the first qualitative question (explaining limiting and excess reagents) and instead wrote “I don’t really know just guessing” and “I was really confused by this video and don’t really understand”.

Video A (analogy) Explanation of how a lack of hot dog buns limits the amount of hot dogs assembled. Video B (traditional) Explanation of how a lack of Sodium ions limits the amount of Sodium Chloride formed.

Defining Limiting and Excess Reagents

Chemistry Question #1: “In the sodium chloride reaction, if there are 4 sodiums and 1 chlorine available. How many sodium chlorides can be produced?”

Worked Solution (using analogy): Worked Solution (using visualisation of atoms):

Explanation of how a lack of burger meat limits the amount of burgers produced. Explanation of how a lack of magnesium ions limits the amount of magnesium chloride produced.

Chemistry Question #2: “In the magnesium chloride reaction, if there are 3 magnesiums and 4 chlorine available. How many magnesium chlorides can be produced?”

Worked solution (using analogy): Worked Solution (using visualisation of atoms):

Revision of definitions of limiting and excess reagents

Figure 2: A flowchart of the analogy and traditional videos with similarities and differences

Figure 3: Two key questions from the post-test worksheet that allowed for both quantitative and qualitative responses.

Student explanations

In the post test, students were asked to qualitatively “Explain how to find the limiting and excess reagents in chemistry”. In the analogy treatment, 7 people mentioned ‘chemistry’ in their response which, while somewhat trivial, it does suggest an ability to separate the analogy from the target chemistry knowledge. In the traditional treatment only 4 people mentioned ‘chemistry’ in their response.

Table 1 shows the quotes that encapsulate the emergent themes that arose when looking over the qualitative responses. In the analogy group, there was less of a tendency to use examples compared to the traditional group, and a focus on the misconception that the limiting reagent was “the first ingredient that is used up”. The traditional treatment saw a misconception that the element with the “larger number is excess and smaller number is limiting” which could have led to the inability to correctly answer the later extension question.

Table 1: Exemplar quotes from student responses when asked to explain limiting and excess reagents.

Analogy

“For example, in a hot dog if there were 5 buns and 3 sausages”

“The limiting reagent is the first ingredient that is used up in a chemical reaction”

“i.e. magnesium chloride (MgCl2)” “I was really confused by this video and don’t really understand”

“Larger number is excess and smaller number is limiting”

“Limiting: by how much there is less than the other element”

“e.g. 1Na + Cl -> 1NaCl” “For example: if there are 3 magnesium and chloride”

Traditional

The written answers, in response to the question ‘Explain how to find the limiting and excess reagents in Chemistry’, were assessed on their level of sophistication and given a rating out of five. These ratings amongst the treatment groups are graphed in Figure 5. An example of a 5-rated response which came out of the analogy treatment was, “In Chemistry, if you

need or want to find the limiting and/or excess reagent you need first the chemical equation and find out how many compounds can be made out of the elements you’re given. The limiting reagent will be the element you run out of first therefore being unable to make any more compounds, and the excess will be the left over element”. A 2-rated response, also from the analogy treatment, would be “Limiting = used all the atoms to create ions, therefore the reaction stops. Excess = the leftover atoms after the reaction stops”.

Analogy Traditional

7

5 6

5

4

2

0 1

0 1 2

1

0 1 2 3 4 5 RATING OF RESPONSE (5 = MOST SOPHISTICATED)

Figure 4: Graph comparing the sophistication of responses of the analogy and traditional group to the question “Explain how to find the limiting and excess reagents in chemistry”

Assessing treatments for helpfulness and interest After watching the video, students were asked about how helpful and interesting they found the instruction. Students were asked to choose a number on a scale from 1 to 9. The results for each treatment group are graphed in Figures 5 and 6.

10

8

6

4

2

0 Analogy Traditional

1 2 3 4 5 6 7 8 9

Score of Helpfulness

Figure 5: Graph of helpfulness of videos reported by students

In Figure 5, it can be seen that while most students in both treatment groups selected a high level of helpfulness (6-9 out of 9) there were three students in the traditional who only selected a score mid-score of helpfulness (4-6 out of 9) for the traditional treatment showing a larger differentiation in responses.

8

7

6

5

4

3

2 Analogy Traditional

1

0

1 2 3 4 5 6 7 8 9

Score of Interest

Figure 6: Graph of interest in videos reported by students

Figure 6 shows a large differentiation in the scores of interest for both treatment groups. However, the average score of interest for the analogy group was 6.59 and 6.24 for the traditional group. This small increase for the analogy group was also evident in the scores of helpfulness where the analogy average score was 7.94 and the traditional group score of 7.41.

Results

There is not significant evidence to suggest that one group answered questions more correctly however there is a tendency for students who watched the analogy video to offer more sophisticated answers (as seen in Figure 5 where 4 students in the analogy group had 5rated responses compared to 1 in the traditional group). Despite this trend, this data, with limited sample size, is not sufficient to draw the conclusion that teaching using the analogy would result in more sophisticated understanding.

Discussion

The literature led to the hypothesis that analogies are more beneficial than traditional instruction when used in science education (Duit, 1991; Richland & Simms, 2015; Sutula & Krajcik, 1988; Thiele & Treagust, 1992), there was very limited clear evidence for this in the results.

Interestingly, there was some evidence to infer that the analogy had the undesired effect rather than the desired where one participant referred to the element as an “ingredient” (Thiele & Treagust, 1992). However, this undesired effect could be explained by the misconception that was created in both videos where we said that the limiting reagent was the element that was “all used up”. This is not an ideal definition; although, it is commonly used in early stages of learning limiting

and excess reagents in chemistry. It provides the basis of knowledge necessary for simpler questions, however, as the questions become harder it does not apply. This is a common problem in science where students are taught concepts with simple claims in order to form a basis of knowledge that can then be increased in difficulty (Thiele & Treagust, 1992; Zeitoun, 1984). Whilst the definition of “all used up” was not unreasonable to use for the experiment, with the extension question it became ineffective as the question did not see one of the elements “all used up” and therefore made it hard for students to conclude which the limiting reagent was. The majority of the students could not solve the extension question due to this misconception, however, 2 students from the traditional treatment were able to answer it correctly. Whilst this isn’t a significant difference, the analogy of a recipe could have reaffirmed this notion of “all used up” where the ingredients were used up. In order to address this misconception, future investigation should use the definition of “first to be used up” instead. More difficult ratios would be more beneficial as an easier question may not allow for differentiation in responses which is what was found in the first test group and why more difficult extension questions were introduced.

In the extension question majority of students were able to pick that oxygen was the excess reagent, however, could not get the number of oxygens left over correct, indicating that they had either misinterpreted the gas or were dependent on guessing oxygen as it was the largest number given. This variable had been predicted and it was attempted to be controlled including an example in the videos where there was more chlorine than magnesium, and yet magnesium was the limiting reagent. In the extension question, due to the higher level of difficulty, students may have been prone to pick the largest number rather than attempting to solve the equation themselves. A harder question was deliberately chosen to assess whether students were truly using higher order thinking as hypothesised (Duit, 1991; Richland & Simms, 2015; Sutula & Krajcik, 1988). The results indicate that students were rather guessing and dismiss that analogies were more beneficial, with no students in the analogy treatment obtaining a correct answer.

Future research

As there was minimal difference in short term assessment, future research could test the theory that learning analogy in classrooms approach has been effective in supporting creation of long-term memory easier to access on a later occasion (Richland & Simms, 2015). This could be done through a second test, delivered a few weeks after the first test to see if analogy has any impact on memory retention of scientific concepts.

The video should be changed to avoid the phrase “all used up”, even though it’s the commonly accepted phrase in most chemistry textbooks, it created a misconception that harboured the students from delving into the extension question that challenged their understanding. Student interviews could be more beneficial than surveys, through probing on comparison on the method on analogical teaching to their traditional methods of classroom teaching.

Conclusion

In my research project I investigated limiting and excess reagents in chemistry and how when students learn this abstract concept using the analogy of the components of a hot-dog they may be able to better understand chemistry exam questions. From my literature review, I found that analogy is a particularly helpful model in explaining chemistry concepts such as limiting and excess reagents, which are otherwise difficult to understand without attachments to real-world understandings, however they do not always have the desired effect and can occasionally confuse students. Using scientific principles, I designed a controlled experiment where 34 Year 10 science students were randomly allocated to watch one of two instructional videos on limiting reagents that I created in collaboration with my research supervisor. 17 watched a video which used the analogy of hot dogs and burgers, whilst the other 17 watched a traditional educational video. Quantitative and qualitative data was collected and assessed through a post-test. Despite my hypothesis that using analogy would improve understanding and responses on chemistry exam-style questions, there was minimal observable difference between the two groups. Future research might involve a delayed test to see whether students who watched the analogy video found the learning more memorable and applicable in the long term.

Acknowledgements

I would like to thank Dr Matthew Hill for his involvement and dedication to my vision throughout the supervision of my project. I would also like to thank Dr Katie Terrett for her feedback and motivation in morning classes. Thank you also to the Year 10 classes that participated in this study for their time and consideration.

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