Chloe K.
Robinson
a,
Melissa
Weinrich
b and
Scott E.
Lewis
*a
aUniversity of South Florida, 4202 E. Fowler Ave., Tampa, Florida 33620, USA. E-mail: slewis@usf.edu
bUniversity of Northern Colorado, 501 W 20th St., Greeley, Colorado 80639, USA
First published on 17th March 2025
Electrostatic potential maps (EPM) have the potential to support organic chemistry students in seeing reaction mechanisms through the perspective of electrostatic attraction. Prior to any pedagogical changes, foundational knowledge on how students use EPMs in particular contexts would be needed to inform how to integrate EPMs into instruction. This study describes an exploration into how organic chemistry students use EPMs during two card sort tasks. Seventeen undergraduate organic chemistry students participated in an interview that included an open and closed card sort. The interviews were inductively coded to identify students’ usage of EPMs, and usage change based on the open sort compared to the closed sort. Viewed from a resources framework, this study demonstrated how students’ use of EPMs shifted depending on the task structure. Variations were observed both among students and within students between tasks in terms of whether EPMs were utilized and when utilized whether information from EPMs were used in isolation or integrated with other chemistry concepts. The results of this study imply that more formal integration of EPMs into instruction and assessment would be needed for students who did not use EPMs. Instruction that models and assesses translation of representations may begin activating a more integrated perspective of EPMs which could be productive for students who had an isolated use of EPMs. The introduction of EPMs independent of specific chemistry tasks (e.g. during a general introduction of molecular representations) could lead some students to focus only on explicit features of the EPM representation and not tie features of the representation to their existing chemical knowledge.
Several studies conclude EPMs are not taught as a traditional model for examining the molecular behavior of chemicals or understanding the drive of electron attraction behind molecular mechanisms. Hinze and colleagues (2013b) found that organic chemistry textbooks regularly incorporated EPMs within them, but rarely include conceptual support for interpreting EPMs nor practice problems involving EPMs. Without contextual information and practicing opportunities for navigating these relatively novel representations, EPMs may be ignored by students (Hinze et al., 2013a,b). Popova and Jones (2021) interviewed 13 chemistry instructors across the US about their teaching and found that instructors tend to omit instructions necessary for students to conceptually apply representational tools to chemical phenomena. The underutilization of less common representations, such as EPMs, creates a learning environment in which students prioritize more frequently utilized representations of chemical species such as chemical formulas and line angle models.
With the benefits of EPMs emphasized in the literature, using EPMs in courses may be advantageous for student learning. Properly integrating this learning tool requires understanding how students implement EPMs into their own thought processes. Understanding where students begin with their representational understanding and what information they extract from representations on their own is important for teaching purposes, as visualizations are not automatically converted into knowledge and students may not initially understand how to utilize a novel representation (Rapp and Kurby, 2008). Additionally, Ainsworth (2006) argued learners are faced with difficulties upon exposure to a novel representation because they must encode and relate it to what it represents before accessing the benefits. As a result, many have argued that practice and chemical knowledge is required to support the use of representations (Kozma and Russell, 1997; Schwonke et al., 2009; Hinze et al., 2013a,b). However, students may be disinclined to use unfamiliar representations. For example, in a study where students were tasked with identifying partial charges and determining molecular attractions, 12 of 18 participants avoided EPMs due to unfamiliarity, while students who adopted the EPMs had greater success with answering problems (Hinze et al., 2013a,b). The current study seeks to understand how students use EPMs across distinct problem types, which can serve as a first step in designing practice that would promote the use of EPMs when problem solving.
In this work, to examine how task changes influence students’ considerations, this study investigated how students come to utilize EPMs as they move from an unstructured task (open-card sort) versus a structured task (closed-card sort). The open-card sort was designed to assess students’ utility of EPMs when no explicit task is given, while the closed-card sort task was designed to identify students’ considerations when working with an explicit goal in chemistry. These tasks may be analogous to instruction presenting EPMs without a particular utilization (e.g. during an introductory lesson on varying representations) versus introducing EPMs as a tool for working on a particular problem type. Comparing student responses across these tasks can provide guidance for introducing EPMs within instruction based on students’ utility development. Here utility refers to how students recognized, employ, and derive value from EPMs as a representational tool for understanding and solving problems. It encompasses whether EPMs are integrated with other chemical concepts and features or used in isolation.
Groups were established from coding task 1 and 3 separately and grouping participants with similar coding patterns. These groupings were then further defined across the tasks from their EPM utility in tasks 1 and 3, highlighting the utility changes from one task to another. After these groups were made, students’ conceptual understanding of the chemistry topics being discussed through the resources perspective, was analyzed based on isolated and integrated reasoning, which further characterized and distinguished the groups. Isolated reasoning describes problem solving where the resources activated, namely the chemistry concepts, are explained by explicit features of a representation independently of other representational features or conceptual resources. Conversely, integrated reasoning describes problem solving where the resources activated are done so by a combination of explicit features of representations and chemistry conceptual knowledge to provide an explanation of chemistry phenomenon.
These reasoning types align with aspects of Schonborn and Anderson's visual literacy framework (2010) in that three interdependent factors are required for successful interpretation of a representation: the conceptual factor, the mode of representation, and the reasoning or sensemaking factor. Specifically, isolated reasoning consists of students incorporating a conceptual factor (resource) independently from other existing factors such as reasoning and the mode of representation, leading to unsuccessfully interpreting or implementing certain representations. Integrated reasoning consists of incorporating a conceptual factor (a resource) and the mode of representation together to incorporate the reasoning factor for the existence of a chemical concept which ultimately leads to successful interpretation and utility of representations (Schönborn and Anderson, 2010).
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Fig. 2 Four groups differing in EPM utility in Open & Closed Sort. EPM = electrostatic potential map; LA = line-angle diagrams; CF = chemical formula. |
“The most polar would be [EPM of ethoxide], just due to the fact that it has this area of really high density, and then another end which has really low electron density. […] And then [EPMs of propylamine & ethanol] are both similar in that regard. Yeah, they have four carbons each and then they each have three carbons and then some other more electronegative atom on one end.”
A similar result is seen with Clara when explaining her category,
“This [category] is less dense. And if it's super red on one end and super blue on the other, then it's probably a higher difference in electron density is probably more polar molecule […] they all have a charged or partially charged part of the molecule like the nitrogens, the oxygens, and the bromines.”
This thought process of identifying polar molecules using the EPMs was also similar with Charlie, Caden, and Candice. Color can be shown to be integrated with the atomic identities to explain a region of polarity within a polar molecule through electron density, as in Candice's statement about propylamine, “the [EPM of propylamine] has the nitrogen that's why it has the red spot there,” shortly after discussing how nitrogen grabs electrons from carbon. These students were cued to polarity by the concentration of electron density as demonstrated by the integration of color distribution and the atomic identities contained within the chemical formula.
Electronegativity and stability were also mentioned as additions to polarity. Carter mentioned stability as a consideration for sorting, stating, “electrostatic potential can kind of show how different regions of areas that would readily bond to other things. And so that's kind of what I was thinking about. Like, which of these things would, is the most readily reactive versus what is pretty stable. So [CH2CHCH2−] does have a little section of higher electron density that is towards one of the edges, but it's pretty uniform.” Charlie, Carter, and the other students integrated information from both the chemical formula and EPMs to draw conclusions on various molecular properties, with an overall focus on molecular polarity.
When switching to the closed sort, these students continued to integrate the colors to describe the electron density and relate to nucleophilicity, similarly to the connection to polarity. For example, Candice explained nucleophilicity and nucleophilic molecules similarly to how polarity was determined:
“So, since the red regions have more electrons in them, a higher density, then that would make that spot more nucleophilic.”
The students focused on the color distribution and concentration to determine a molecule as having nucleophilic characteristics. Caden discussed recognizing a nucleophilic molecule from integrating both the line angles and the EPMs:
“Having them [LAs] all drawn out, it's kind of easy to see where the lone pairs would lie and then also with the colored images [EPMs], I think that generally if it has more electron density in one area, it's kind of a nucleophile too.”
These students consistently made conceptual inferences based on the electron distribution to indicate molecular behaviors. For students who integrated EPMs with chemical concepts when explaining their open sort, the context change to closed-sort did not impact their reasoning or utility of representational features. This suggests that these five students may potentially utilize EPMs across varying contexts. Additionally, everyone except Candice recognized that the closed sort molecules were duplicates of one another. This is summarized by Clara who questioned, “[EPM & LA of propylamine] look the same. Yeah, it's the same molecule. Okay, so the same strength of nucleophilicity. Are these all the same? Okay.” The recognition of molecular duplicates among the line angle and EPMs demonstrates representational translation and may be related to the employment of integrated reasoning. The use of EPMs integrated with chemical formulas and line angles in both environments also suggests that these students understand chemistry in a way that makes them open to implementing new features from the EPMs with features from familiar representations to establish those conceptual chemical explanations. The colors may serve as enrichment to students' conceptual explanations and understanding when integrated with other explicit features for electron density and therefore assist in explaining and understanding polarity and nucleophilicity.
For these students, EPM colors were used in isolation from other representational features during the open sort to describe partial charges and polarity. Ian determined the polarity or lack thereof within a molecule from the color distribution alone:
“Based on where the red is on some of them, the red is really prevalent only on one side and some of them, they're spread out, which means they're non-polar.”
Ian used colors in isolation for determining polarity by focusing on the areas of color concentration, indicating a polar compound is one with a fair amount of red and a nonpolar compound is one with relatively even color distribution. The explanations of a polar molecule are limited to identification due to the isolated use of colors.
Iris focused on color intensity instead of color distribution and inferred charge intensity:
“I am thinking about the intensity of the charges. So, I sorted, based on having the most electrostatic potential, and there's a lot of green in here, and yellows, which are indicating there isn't a strong positive strong negative charge really at play. Of course, some of them have that little bit of intense color, but overall, there's a lot of those medium colors of orange, yellow, and green present, whereas in my left category, there are those strong vibrant blues and reds which indicate a strong positive and negative charge at play.”
Iris used colors to identify charges, but no other chemical properties or identities were used to justify the charge assignments. Similarly, Iyla focused on the areas of color concentration, defining those areas as regions of charges of the molecules,
“With [EPM of propylamine, CH 2 CHCH 2 − , & (CH3)3C+], I saw more green, which I know is more neutral, so I put those in the middle.”
The colors serve as indicators for polarity or charge based on color presence or concentration alone, and thus EPMs were used with reasoning isolated from other chemical features and as a result, explicit explanations of chemistry concepts were not present. Unlike students who consistently used EPMs in an integrated way, students here chiefly utilized the EPMs for developing their categories, with little to no references to the chemical formula.
Students who used isolated reasoning of colors in the open sort diminished their use of EPMs in the closed sort. Their approach to the nucleophilicity sorting relied on the isolated use of line angle features as a primary deciding factor while EPM usage was limited to assisting with memorized characteristics. Iris explicitly indicated a focus on the line angle's “potential charges and how much of an electrophile and nucleophile these would be.” However, when analyzing propylamine said:
“it looks overall to not be very nucleophilic or electrophilic with the EPMs just because of that giant green spot with the CH3, CH2, CH2. But in the NH2 section, you can obviously see that the hydrogens and nitrogen are very different with their charge potentials,”
and concluded: “It doesn't exactly match up the way I had expected.” Iris briefly referred to EPMs when requiring support with regards to nucleophilic characteristics in propylamine and decided to place that molecule in the “neither” category after considering both representations. Specifically, Iris struggled with the identity of propylamine concluding that “CH chains are quite neutral” and then seeing the EPM have an area of high color contrast. While she considered both arguments, she did not combine the two features together to conclude its electronic property. Instead, with two conflicting ideas she did not move forward in making a decision with that molecule, denoting it as neither an electrophile nor a nucleophile. Ian invoked a heuristic in determining nucleophilicity and electrophilicity:
“These are all I think nucleophiles: [ethoxide & CH 3 COCH 2 − ] have a negative charge so that makes them nucleophilic especially the [ethoxide] with the negative charge on the O that makes it extremely nucleophilic and then […] this one [2-butanone] also has an O. So that's also like a nucleophilic.”
All students in this group used a heuristic of a negative charge indicating nucleophilicity without considering features from other representations to explain why molecules were nucleophilic or electrophilic. Ian concluded that the EPM's value had already been exhausted as all the molecules provided were polar and his perception was that EPMs did not provide more utility after that determination, based on the prior isolated use of colors. He noted “none of [the EPMs] were symmetrical in any way. There were charges on them, and they were all polar molecules.” Abandonment of EPMs is equally seen with Iyla where although EPMs were initially used to guide the open sort, she instead focused on atomic identities for electronegativity clues in the closed sort task:
“Chlorine, I know is a good leaving group, so that would make [LA of 1-chloropropane] more [of] a strong electrophile. And it would want to leave.”
This demonstrates that Iyla knows chlorine is a good leaving group and the presence of chlorine was taken from the representation, but there is no explicit indication of other conceptual resources to conclude the leaving group properties of chlorine, indicating isolated use of line-angle representations. Here, the EPMs were not utilized in the closed sort. These students concluded nucleophilicity assignments from the chemical formula and line angles, with EPMs used only when students expressed confusion with assigning nucleophilicity to line-angle structures. Essentially, when the EPMs were used, the colors served to be identifiers of polar molecules without explanation. The change from the open to closed sort showed these students picking features for descriptions individually instead of in combination with other chemical properties, in contrast with students who consistently utilized the EPMs. A tentative conclusion is that students who invoke EPMs without chemical concepts may more readily abandon EPMs when heuristics that use more familiar representations such as line-angle diagrams are available. Further, only one student from this group, Ian, made explicit note that the molecules of EPMs and line angles were duplicates, which suggests that isolated reasoning of EPMs may also be indicative of eschewing representational translations.
“I did try to look at the electrostatic maps, but it wasn’t working out. […] Because I feel like there's supposed to be a trend. But my placement of cards, there is not any significant trend, so I just stuck to ionic, polar or non-polar.”
and similarly with Beth:
I didn't look much at the EPM, but I think it was mostly the one where it hindered me the most in visual… looking at it would have been [EPM of an enolate] and [EPM of an acyl chloride]. It was hard to see the EPM there.”
Beth attempted to use the EPM but found it difficult to visualize two of the molecules that share similar structures. She did not make connections between the coloring differences and therefore sorted primarily by the chemical formula in isolation from other representational features. Brandon and Beau also explicitly stated that they did not see a valuable connection among the molecules when looking at the EPMs. Within the open sort, these students individually focused on negative or positive charges, atoms, or functional groups inferred from the chemical formula of a molecule. For example, Bailey explained her process of determining polarity:
“Well, I know CO 2 is often nonpolar. For these ones, the CH 3 –CH bonds there's a lot of them and I think in one of the classes [an instructor] mentioned that just because there's an oxygen in there doesn't make it polar.”
She used atoms of the chemical formula and heuristics to determine molecular polarity but did not detail the cause of molecular polarity nor the properties that emerge from polarity, unlike observations with the students who consistently integrated features. Students in this group conveyed initial hesitation with EPMs and sorted by isolated, and visually distinctive features from chemical formula such as the number of carbons, structure, or the atom types. For example, Bryn sorted by charge:
“Now that we have charges – we have [EPM of CH 2 CHO − ] minus, [EPM of ethoxide] minus, so [EPM of CH 2 CHCH 2 − ] minus. So, this [group] is just a negative.”
These students did not integrate characteristics of the EPMs within their open sort. In comparison to students who initially used isolated reasoning with EPM colors, it is possible that the students discussed here did not feel a need for utilization of colors when chemical formula and heuristics can be used to identify polarity or charges.
These students who relied on chemical formula in the open sort began integrating the colors of EPMs with other features when sorting molecules on nucleophilicity. Five of the six integrated the EPMs for categorizing molecular structures, while Bryn categorized first with line angles and then integrated EPMs to support her conclusions. These students focused on charges and atomic identities, in combination with the EPM colors as an indication of electron density, to determine if molecules were nucleophilic or electrophilic. Beau combined information from the charges of the chemical formula and line angles with EPM colors:
“For [LA of 1-chloropropane], it doesn't have a positive charge, but I knew Cl was a good leaving group and if Cl is going to leave then that third carbon would become positive, and the same thing would go for [EPM of 1-chloropropane]. Because in the electric cloud, […] saw the darker blue, which told me that would lean towards the positive side more, so if that Cl did leave, it would be able to react with the nucleophile.”
The integration of the representations utilized allowed this student to determine that 1-chloropropane could act as an electrophile. Similarly, Beth and Bailey integrated charges, atomic identities, and colors of the EPM concurrently to draw conclusions regarding electron density. For example, positive charges with dark blue hues were used as an indication of low electron density that could participate in attracting nucleophilic molecules. Becca relied primarily on structure of the chemical formula and color intensity of the EPMs in determining nucleophiles and electrophiles:
“For nucleophiles, I was more focusing on how strong the red region is in comparison to the blue region. So, for [EPM of propylamine], it has a super strong red region and a very short blue region, and the rest of the molecule is green. So, I figured that would be a really strong nucleophile […] Like [EPM & LA of 2-butanone] originally, I thought would be nucleophiles because if you have a double bond connected to something, the double bond attacks and that's the characteristic of a nucleophile.”
Becca found utility in the EPMs, where color is related to electron density (mentioned earlier in her interview) and then high electron density is connected to nucleophilicity, and low to electrophilicity integrated with the structural feature of the line angles. Bryn used the line angles and chemical formula first to assign nucleophilicity and then integrated the EPMs to provide evidence of other concepts, such as electronegativity, to support the assignments:
“[…] The question is, which one's more electronegative? Because chlorine I would guess… […] If we look at the pictures, this is very red. Ok. So I’m going to try to use that EPM to say that this [2-butanone] goes here [stronger than 1-chloropropane].”
She began to seek support by integrating the EPMs to assist in determining the levels of electronegativity when using isolated atoms was not clear.
These students overcame their hesitancy in working with EPMs when the task changed to the structured task. The contextual change from open sort to closed sort is presumed to have prompted the students to integrate EPM with chemical concepts when asked to predict nucleophilicity. This is also evidenced by four of the six students in this group who explicitly acknowledged the molecules of EPMs were replicated as line angle representations. Becca mentioned, “See the more that I'm going through it, the more that I'm realizing, that the line structures that you gave me are the exact same as the ones with the potential maps.” These students' usage of the EPMs integrated with chemical concepts mirrored what the first group described, with recognition of duplicates occurring more often when integrated reasoning was activated. However, these students did not see the utility of EPMs within the open-sort task.
“I'm not really sure if I'll be able to, categorize them [EPMs] in an efficient manner because I don't think that my understanding of the diagrams even provided in the lecture notes are decent and we don't really need to use them in our tests or homeworks.”
Similarly, Naomi's preference remained with the chemical formula representation also citing unfamiliarity:
“My teacher's mentioned [EPMs] in lecture basically. Usually, it's when he's explaining things to us, concepts to us why they react a certain way, we don't necessarily have to know it and understand it, at least not yet.”
Naomi seemed to similarly disregard the EPMs, not seeing them as necessary for understanding the chemistry knowledge that has been encountered thus far. There is a default to isolated use of the chemical formula in these students’ sorting strategy, and the utility remained throughout the two tasks. Students among this group typically did not go further than listing the explicit features present in the chemical formula. Naomi explained when describing the sort:
“My first group is ones that aren’t organic, so it doesn’t have carbons and hydrogens so, one of them only has […] hydrogen and oxygen, but it doesn’t have a carbon.”
This student identified explicit features, such as atomic identity, and used that in isolation as the focus of the sort, without invoking other chemical properties. Nolan similarly and predominately used the atoms of the chemical formula to determine molecules as polar or nonpolar. He does not describe causes for polarity and instead, discusses a heuristic for determining polarity through lone pair identification:
“When you're looking for example, ammonium or water, how to identify if the molecules polar or not. If the central atom has no lone pairs and electrons surrounding it are equal to each other then it's non-polar. Okay. And if it violates one of those restrictions, then it's polar.”
These students disregarded the EPMs and instead isolated explicit features from the chemical formula or used a heuristic without discussion of those concepts, as seen with Nolan and polarity. These students approached the open-sort task similarly to the third group in reliance on isolated features of chemical formula.
In the closed sort, these three students continued to avoid using the EPMs in contrast to the third group. The discomfort expressed by Neena, Naomi, and Nolan when utilizing the new learning tool, was attributed to inexperience and having a more solid foundation for the other representations, as these students continued to sort based off isolating explicit features in the line angle and chemical formula. Naomi stated,
“I remember going over it [EPM & LA of 2-butanone], but I don't remember which one it was overall. I remember that – I think it's a ketone on it – the oxygen is one and then the carbon is one. But I don't remember which one was more electronegative.”
This group can be summarized as those who did not utilize EPMs and made conclusions about molecules based on isolating explicit features from the familiar representations. Similarly to students who reasoned by isolating features with EPMs and line angles, Nolan, Naomi, and Neena also did not recognize that the set of molecules were duplicates, with Naomi and Nolan recognizing a subset. Specifically, Nolan discovered three duplicate pairs and Naomi discovered one. This supports the earlier suggestion that isolated reasoning of a representation may also be indicative of eschewing representational translations.
Past work has shown that when presented EPMs, students were more likely to invoke electronic features (Farheen et al., 2024a,b; Nelsen et al., 2024) and causal reasoning when describing mechanisms (Farheen et al., 2024a,b). However, it was also shown that when students had access to information in addition to EPMs, students relied on more familiar representations such as chemical formula (Nelsen et al., 2024). Past work relied on students’ utilization of EPMs within structured tasks, while the resources framework predicts that a change in the task can change the resources activated by students. This study found that students were more likely to utilize EPMs with the structured, closed-sort task and were more likely to integrate EPMs with chemistry concepts in the structured task. With the open-sort task, students were more likely to use EPMs in isolation with other chemistry concepts. The use of chemistry concepts in isolation calls to question the meaningful use of EPMs by students in this situation. The visual literacy framework describes students who use a conceptual resource in isolation from other resources including the representation presented are unsuccessful in accessing the benefits of representations (Schönborn and Anderson, 2010).
Promoting students’ utilization of EPMs will become necessary to realize any learning gains from using EPMs. The current study found that promoting students’ utilization may face a few distinct challenges. First, students from the “No EPM Utility” group described both an unfamiliarity with EPMs and no need to learn EPMs within their instruction as reasons for not utilizing EPMs. These challenges suggest that more formal integration of EPMs into instruction and assessment would be needed to make the case for utility of EPMs to some students. Second, students in the “Isolated use of EPM” group relied on explicit features of EPMs without bridging these features to chemical concepts and activated resources. These students ultimately abandoned EPMs when given a structured chemistry task. Hence, instruction that structurally models and assesses translation of representations may begin activating a more integrated perspective of EPMs which could be productive for these students. Such instruction could begin with students given EPMs and identifying possible atomic identities or functional groups or identifying the corresponding line-angle or skeletal diagram rather than providing students with EPMs as an optional tool. Each of these instructional suggestions would require further testing. Ultimately, while eleven of the seventeen spontaneously integrated EPMs with chemistry concepts when explaining their closed-sort in this project, it suggests that such spontaneous integration cannot be relied on from an instructional standpoint.
Introducing EPMs within a defined chemistry task, such as ranking molecules on nucleophilicity or identifying nucleophile sites on molecules, would appear to have advantages over introducing EPMs without a defined chemistry task for some students. This finding corresponds with a recent study evaluating tutorials designed to increase students’ levels of explaining an SN1 reaction using EPMs and line angle representations that concluded further personalization of tutorials needs to occur to properly support students’ needs (Dood et al., 2020). Both the recent study in the literature and this current work suggests meaningful variations in how students interpret representations. The findings in the current study add to this by suggesting that more students see relations between EPMs and information from other representations (e.g. atomic identity) when they are engaging with EPMs in a defined task. The introduction of EPMs independent of particular chemistry tasks (e.g. during a general introduction of molecular representations) may lead some students to focus only on explicit features of the EPM representation for resource activation rather than integrating features of the representation to their existing chemical resources.
The findings from this work also expand recent work in representational competence as it applies to molecular representations. Representational competence is a set of skills that allow a person to use single or multiple representations (Kozma and Russell, 2005). One skill within representational competence is translation, or the ability to make connections across different related representations (Ward et al., 2025). Eleven of the seventeen students made explicit mention during their closed sort that the molecules on the cards were duplicates. Eight of the eleven students who noted the duplicates also adopted integrated reasoning between the EPM and chemical properties. Conversely, three of the six students who did not explicitly note the duplicates adopted integrated reasoning with the EPMs. These findings suggest that training to promote translating between representations may be beneficial for students to integrate representations with their chemistry resources; future research would be needed to test this suggestion. Ward et al. (2025) found that representational competence may be better described as correlations between skills of interpretation, translation, and usage, instead of separately distinguished skills. Further they also showed that among organic chemistry students, representational competence varied and should not be assumed with instruction. The current project matches these findings as those who translated the EPMs (e.g. noting the duplication of molecules within the closed sort) also tended to be those who integrated EPMs in conjunction with chemistry knowledge suggesting a common skillset, and this skill was also not universally demonstrated. This work expands Ward and colleagues (2025) findings to EPMs as this representation was not explored in their work.
It can also be expected for some students to benefit from EPM utility when features are integrated with other representational features. Eleven of the seventeen participants found EPMs to be fruitful for integrating polarity or nucleophilicity with chemistry concepts. Students using EPM features integrated with chemistry concepts appear more likely to benefit from the use of EPMs, and the format of the context may promote this integration. Additionally, eight of the eleven students who integrated EPM features into their reasoning also accurately recognized all the molecular duplicates, indicating representational translation. Therefore, integrated reasoning may directly relate to the ability to make connections across multiple representations and potentially improve chemistry associated skills, offering an avenue for promoting integrated usage. This study suggests that if students are to be trained in sensemaking of chemistry with EPMs, establishing a context that requires a level of reliance on chemical principles may encourage students to go from isolated utility to integrated utility in thought processes, and therefore utilize EPMs in a beneficial way.
Code | Description | Example |
---|---|---|
Prompted – EPM utility | A prompt from interviewer that potentially causes a change in student's approach to sort where EPMs are then used or student states that they used EPMs after prompt when use was not otherwise present | (This ex would also be coded as No use of EPMs) |
Interviewer: “Were there any other chemistry concepts. That you were thinking about? You mentioned earlier that EPMs would make you think about polarity. Did you think about polarity at all?” | ||
P13: “Well, they all look polar, so not really, since none of them were symmetrical in any way. There were charges on them and they were all polar molecules.” | ||
Unprompted – EPM utility | Student begins to utilize the EPM on their own, not prompted by interviewer | (This ex would also be coded as use of color to describe ED to relate to nucleophilicity) |
“But then now looking at the electrostatic potential maps, and electron density. Yeah. Okay. So that, it's actually looking for… I’m trying to see or remember as well, just what…or see how these relate to each other as far as electrophilicity versus nucleophilicity goes, based on the electrostatic potential maps.” | ||
Prompted – no utility | An explicit statement of students not using EPMs after being prompted by the interviewer | Interviewer: “Did that [colors] influence how you grouped them at all? |
Interviewee: “I just…I think like in class we never really see the clouds as much, so I rely more heavily on the structure in the formula given, not the colors of the cloud around.” |
Combinatory code | Sub-code | Definition | Example |
---|---|---|---|
Atoms + color | Electronegativity | Students make connections between atoms from CF and colors to understand electron density/electronegativity in the molecules | “CO2 can have oxygen negative – red. And with the W, the carbon is very blue because it's going to be very positive” |
“Well, I can kind of make a connection to something because like at the end of the SH, its like popping up at the separate atom, and then here it's popping up at the Br and then there's red at the H, kind of showing which molecule has more, not more stability, but like in terms of O and Br, it would be like which atom is more electronegative” | |||
Polarity | Students make connections between atoms from CF and colors to understand polarity of the molecules | “Actually, this one does look, the T card looks pretty similar to these other ones where it's mostly the greens and blues and then the red bit where the oxygen is. So I’ll put the T card in the polar spot category.” | |
“M is an alkyl halide because it has a chlorine bonded to it then N has an amide group P has an OH group meaning that that's an alcohol and then X has a sulfide group. So they can be classified. These can be classified as polar, I would say because there's like a, um, as a diagram shows how like the electron density is highest at one pole and then the other one it's green. How green represents that there's not much electron density.” | |||
Stability | Students make connections between atoms from CF and colors to understand stability of the molecules | “So aside from looking at charges, because not all of them have charges, the charges kind of like help me, I guess picture and understand it […] The less positive is, the more unstable its going to be” | |
Reactivity | Students make connections between atoms from CF and colors to understand reactivity | “I knew Cl was a good leaving group and if Cl is going to leave then that third carbon would become positive, and the same thing would go for [EPM of 1-chloropropane]. Because in the electric cloud, […] saw the darker blue, which told me that would lean towards the positive side more, so if that Cl did leave, it would be able to react with the nucleophile” | |
Charges + color (students must indicate they are speaking of charges, default to atoms) | Electronegativity | Students make connections between charges from CF and colors to understand electron density/electronegativity in the molecules | “I am thinking about the intensity of the charges. So I sorted, based on having the most electrostatic potential, and there's a lot of green in here, and yellows, which are indicating there isn't a strong positive strong negative charge really at play.” |
Polarity | Students connect the colors and charges of CF to polarity | “Um, I looked at the charges first, but next I did look at the colors. And that's because that's how I really determined if they're polar or non-polar. So I think that without the colors, my categories would definitely be different.” | |
Stability | Students connect the colors and charges to stability | N/A – this code was not applicable to the data | |
Reactivity | Students connect the colors and charges to reactivity | “I would imagine if you look at this and look for example S&O's you can say oh probably S is more reactive than O just by the sake of having one like in shape as a spear. […] it's a line in a ball and you can think that the line is going to be like more reactive into trying to touch something else instead of just having like a ball of concentrated red charge. That doesn't point in any given direction. It's just there.” |
EPM focused code | Definition | Example | |
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Color | Electronegativity | Student uses color alone to identify the electronegative areas in the molecules | “Let's see. And I also just and now that I know the difference, I think I know the difference. I could just differentiate by which ones seem to be more electronegative than the others based on the colors. So which ones exhibit more blue? Which ones exhibit more red?” |
“Well, I'm probably going to start to sort them by like where the electrons density is. Where it is more like centered and more like on the outside.” | |||
Polarity | Student uses color alone to describe the polarity of the molecules | “And it's leaving me right now. But you – I definitely know for a fact that if you're tipping more on one side than another, you definitely have a polar compound. And then if you see more of a mesh of colors, I want to assume that you're getting towards non polar and stability” | |
“And then I'm like, the ones where it's more dense, like in the middle or the ones more on top, and then. less denser on the bottom because it's all like the polar regions. And then these, like it's not as polar because it's more like muddled.” | |||
Partial charges | Student uses color alone to describe the partial charges of the molecules | “So I guess blue associates with positive. And as you get to red, which would be from green to yellow to red and that's why W is such a good reference, because you can see the clear cutness as you get to red, you're getting to partial negative and that's another thing. The partial charges, I think that's definitely related to this.” |
CF focused code | Definition | Example |
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Atoms | Student uses the atoms to describe sort without making conceptual connections | “I think this is how I would sort. I don't know if this makes sense, but I did like X, N, P, T because they have like the carbon hydrogen chain, but then they have another molecule. These two don't have. R&W don't have a carbon hydrogen chain.” |
Charges | Student uses the charges to describe sort without making conceptual connections | “Um, or negatively charged and positively charged species and then like neutral species. So there could be three ways of putting it which is again non-technical. So in that case, U, S, V these are negatively charged so they can be in one category. Okay? And then the positively charged are like O, and then H30, or actually, O and R and then everybody else's neutral and then among them, um, so there is again there could be like a very basic non-technical classifications form.” |
Polarity | Student describes polarity/electronegativity using only the CF | ““For non-polar…from CO2, it was more so the presence of the long chains of the CH stretch. And then for polar, it was a short chain of the CH stretch and then CO, which is pretty highly electronegative.” |
Structure | Student sorts based on pi bonds without making conceptual connections | “So kind of what's going through my head as I'm kind of looking at these three and going this one being a tertiary carbon and then this one doesn't because it has that pi bond” |
Geometry | Student sorts by spatial arrangement without making conceptual connections | “And then S for me is kind of out there where I could put S I could kind of put S with R and O in terms of what it would look like in linear space. But it's a little bit different because R and O actually have that pyramid formation and this one doesn't.” |
Stability | Student determines stability using atoms in the CF or structure | “Negative charge, the more nucleophilic it is, the more willing it is to bond to that positive charge for the stability to become neutral.” |
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