The activity had two parts: Part-I-Forces, which introduces the forces as the underlying principles of bonding, and Part-II-Energy, which builds the energy explanations upon the concept of forces. Most participants were in the tenth grade, majoring in chemistry.
In Israel, all the students study a basic- sciences or chemistry course in tenth grade. Students who choose to major in chemistry study more advanced topics for three years — 10th, 11th and 12th grade.
Participants were sampled opportunistically; they all showed willingness and interest in participating in the research. Internal Review Board at the Faculty of Education at the University of Haifa was obtained for the study, as was the approval of the Ministry of Education's chief scientist. Full consent was given by all participants and their parents. At the time of the interviews, all students had already learned the topic of chemical bonding; the topic was taught using the octet rule approach.
The meetings took place either during recess at school or outside of school hours at the interviewer's house or at the student's school. The first author conducted all the interviews. During the hands-on activities, she answered clarifying questions about how to work with the software. She explained to the students in advance that she would not be allowed to answer questions about chemistry.
The questions were created in-house and refined through several pilot studies. During the interviews, students were asked to use gestures. According to Goldin-Meadow and Wagner , gestures that accompany speech convey the entire idea, whereas speech conveys several separate ideas, consisting of collected words and fragmented expressions.
For each student a row the knowledge elements columns that were mentioned were highlighted Fig. The columns and rows were then arranged by descending use. The use of visualizations in educational research supports understanding of how mental models develop and change in context and how knowledge and strategies are constructed Hmelo-Silver et al. The visual clustering indicates a strong shift in the group pattern. We identified six types of nesting that compose the six mental models used by students to describe chemical bonding Fig.
The sketches on the right side of the figure depict the mental models Fig. Following the sketches from top to bottom shows how each of the added knowledge elements enriches the next mental model in the hierarchy and leads to a more complete and scientific view of the chemical bond. Repulsive forces are added by only those students who also explicitly mentioned the distance between atoms, resulting with a mental model of atoms that are apart, or that there is some distance between them.
Finally, dynamic descriptions can take place only after a full force-based model is understood, that is, including both attractive and repulsive forces and understanding that they act simultaneously. To analyze their processes of learning, we compared their screen-capture videos and their activity guide responses at three points in time. Critical events were selected from the two activity guides: discovering repulsion, identifying the forces, and relating to energy changes Table 5.
For both of them this interaction between atoms was unusual and disjointed. They were surprised and even embarrassed as they could not understand what was happening. As we have shown previously in the findings Fig. Ella could not separate the phenomena into a combination of attraction and repulsion.
She could not accept the idea that attraction and repulsion act simultaneously. Consequently, she did not compare attraction and repulsion. This might be related to her idea about the source of repulsion, the octet rule:. As we will show, this will prevent her from relating the relationships between forces to the distance between atoms and, later on, to changes in energy.
In contrast, Miki understood the dynamic relationships between the atoms. We can see how the visualization of the forces — size, direction, and the relationships between them — supported Miki and most students in understanding the forces as the principles underlying chemical bonding. During the activity, Ella could not use forces to explain the energy changes, or interpret the minimum of the energy curve as an equilibrium of equal forces.
This results from her lack of understanding of repulsion as a force. Thus, she could not compare attraction and repulsion to make sense of the well in the energy curve.
Ella did not know how to respond to question 10 Fig. In explaining the phenomena she was experiencing, she talked only about attractive forces. She could not abstract the concept of repulsion from her experiences with the simulation. As a result, she could not explain why energy is required to break the bond. By contrast, when Miki ran the simulation and observed the resulting energy curve, he immediately made the connection to forces with no additional prompt.
While moving the atoms, he said:. So the thing that happens here [energy curve going down] is that attraction is bigger than repulsion until reaching a state of bonding; and when we approach too much then the repulsion is larger and the atoms escape from each other.
Continuing with the activity guide, Miki used the forces and the energy curve to explain his answers:. Interviewer: Has working with the simulation changed your understanding of chemical bonding?
Ella: Yes, it confused me a little bit. Ella: Because I did not think about attractive and repulsive forces.
Ella's gestures reflect that she could not apply the new knowledge element of repulsion. In representing the atoms with her hands, she brings them together until they touch — in both the pretest and the posttest interviews, showing attraction without repulsion Fig.
Miki: It completely changed my understanding. In the previous [pretest] interview I tried to search for the words and the concepts in order to explain and also… it was disconnected from reality because I did not refer to the forces between the atoms at all.
I referred only to the stability which I defined as the fact that the atom has a certain number of electrons in the energy levels. Which is correct, it exists, but what really holds the bond is the attractive and repulsive forces between the atoms. So yes, it changed my understanding.
Interviewer: Do you remember what in the simulation changed your understanding? What helped you? Miki: I think that when I saw the arrows there was a moment that I saw the arrows and I understood that… at a certain stage, the attraction and the repulsion are equal and this is the most stable state. Because in the beginning, I thought that when I [the atom in the simulation] come closer and closer and closer and it is simply repelled, a bond is not being formed, this is what I thought at the beginning.
Later on, I understood that the bond is created in the most stable sta… in the nearest state so there is a bond. Miki's gestures reflect his conceptual learning. In the pretest, he brings his hands together until they touch, showing only attraction. In the posttest, he signifies the two forces as arrows with his fingers that work in the opposite direction, showing both repulsion and attraction Fig. To conclude, while these two students grew to appreciate the existence of repulsion in the chemical bond during the first task of the ELI-Chem simulation, only Miki — as an example to most students — succeeded in building the force-based model.
In comparison, Ella also took advantage of the simulation to learn about the repulsive force. However, she related repulsion to the octet rule explanation without the ability to build upon it or to replace it with the force-based mental model. Our findings show that learning with ELI-Chem overcomes two persistent hurdles that have been highlighted by several leading chemistry education researchers: 1 chemical bonding is based on attractive and repulsive forces, and 2 the relationships between these forces explain the energetics of chemical bonding.
Thus, interacting with the dynamic force-based representation is suitable for developing mental models that are more consistent and causal, and include a more scientific and comprehensive set of ideas. Understanding that there is a repulsion between atoms was odd for the students, reflecting that this interaction is outside of their bodily experiences in the world. Once students learned about repulsion, they could explore and understand the effect of the relationships between the forces on the distance between atoms.
Through their investigation, they discovered the state of dynamic equilibrium in which the opposing forces are equal. At this stage, the students had a runnable mechanistic mental model de Kleer and Brown, of chemical bonding — they were aware of the components and the relationships between them that could emerge into the single dynamic equilibrium of bonding.
Having this mental model in place enabled the integration of the energetic aspect expressed in term of forces. Understanding why energy is released during bond formation or why it is required to break a bond was feasible. The change in their understanding was reflected in two main points: 1 whereas in the pretest interviews they either could not explain their answers or used memorized rules of thumb, in the posttest interviews they were capable of constructing a causal explanation based on forces; and 2 whereas in the pretest interviews they used both correct and incorrect energy knowledge elements, reflecting a state of confusion, in the posttest interviews they used mostly the correct knowledge elements, indicating that their confusion had almost disappeared.
These changes indicate that after working with the ELI-Chem environment, students gained new knowledge elements upon which they could build causal explanations. As ST16 said in the posttest interview,. Now I understand that you have to invest energy to overcome the forces of attraction that are spontaneous between the atoms. And this [the simulation] allows me to understand this.
The second limitation is the sample size. In balancing the study's depth and breadth, we interviewed 21 high school chemistry students who described and explained their understanding of chemical bonding. These explanations were then analyzed through a knowledge elements perspective, aggregating in six mental models of chemical bonding.
The interviews were extensive and the analyses were in-depth using both top-down and bottom-up methods. Thus, in the balance between a larger sample to increase validity and the advantages of qualitative analyses in producing a deeper understanding of the phenomenon, the study was conducted with this number of students.
A related limitation concerns the analysis method used. With a large number of participants, one could do a factor analysis or clustering process with statistical software. However, this was not feasible in the present study because of the smaller sample. The uniqueness of this work stems mainly from the fact that the design of the learning environment, both the simulation and the activity, was based on a combination of three aspects: the scientific model of the chemical context, the principles of the pedagogical design and the results of a previous study into the process of learning.
Based on our findings, we make two main recommendations. One concerns both teaching chemical bonding, but more generally when teaching about dynamic equilibrium phenomena. Our recommendation is emphasizing the existence of the two opposing forces acting simultaneously in a chemical bond — attraction and repulsion. The technology of the computer simulation allows visualizing the forces and their relative magnitudes as they shift and combine with even minute movements of one atom with respect to another.
Teachers can demonstrate that the most stable state is a dynamic state in which the atoms are continuously attracted and repelled, moving around the point of equilibrium at bond-length.
Resulting from this, students do not fully grasp the studied concepts. Following this, the process of learning can be supported by presenting the missing parts and helping students construct a more consistent mental model. Envisioning or running a mental model takes place only when the system's entities are placed in space and their interactions are fully defined de Kleer and Brown, As students move an atom on the screen, they change the distance between the atoms.
For each distance, the attractive and repulsive forces, and the potential energy are calculated and displayed. The common expression of Lennard-Jones equation is: 1 where:. Thus, in the ELI-Chem model:. That means if we bring two magnets of similar poles north-north , south-south , then the two magnets repel each other. Use : This technology is used in MagLev Trains. MagLev is a lavitating train that works on magnets repulsion principle.
The train track and train wheels are similarly magnetized. So the train floats above the track. This reduces friction and gives the train more speed and smooth running capability. If two magnets with different polar sides north-south , south-north are brought near each other then attraction happens between them. Also magnets attract magnetic materials such as iron , nickel , Cobalt.
This property is very widely used in automotive , manufacturing industries. This principle of magnet is used in making compass. Read more about how to correctly acknowledge RSC content. Fetching data from CrossRef. This may take some time to load. Loading related content. Jump to main content. Jump to site search. You do not have JavaScript enabled. Please enable JavaScript to access the full features of the site or access our non-JavaScript page.
Issue 4, From the journal: Chemistry Education Research and Practice. Attraction vs. Asnat R. Levy a.
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