Macroscopic and Microscopic Views of a Chemical Reaction - Chemistry LibreTexts
Chapter 2. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Macroscopic, Microscopic, and Submicroscopic. Macroscopic . Macroscopic can be seen by the eye or BIGGER. Microscopic is through a " normal" microscope (x. Submicroscopic is too small to clearly. The three levels of representation are macroscopic, microscopic, and symbolic. The microscopic, sometimes called submicroscopic or particulate that exist at the particulate level and their relationship to one another.
Because these particles are microscopic and invisible to the naked eye, the particulate level is sometimes called the, submicroscopic, microscopic or molecular level. The particulate level is the most valuable level to chemists. Once chemists understand how molecules behave at the molecular level, they can take advantage of this behavior to design materials with unique properties.
This level uses symbols to describe the invisible particles that exist at the particulate level and their relationship to one another. We can express this relationship as: We can write a balanced chemical equation for this reaction as: Keep in mind that a model is not the actual thing is representing. It is an approximation to help us study and predict the properties and behavior of the actual thing. In science, models can be abstract, conceptual, mathematical, and graphical.
When we write each level on one of the vertices of a triangle, we get what we call the Triplet Representation. The triplet representation was proposed by a well known chemical educator called Alex Johnstone. It can help us in many ways. First, it hints at the idea that when we study a chemical substance or phenomena, we should at least think about it at the macroscopic- particulate- and symbolic- level. What does that mean? When it exists as pure liquid it is colorless. When it exists as solid like ice or snow it is white.
When it exists as a gas, it is invisible. At the particulate level, water consists of two hydrogen atoms united bonded with one oxygen atom. Depending on energy, temperature, and attractive forces, water molecules can arrange at the molecular level to form solid, liquid or gas. At the symbolic level, water is depicted as H2O, where H: The subscripts reflect the ratio in which these two different atoms always react to form water.
Throughout the text, discussions team up with illustrations to bring home this central theme. Models are explained at the observable level and then from a close-up, molecular point of view.
To bridge the mind-boggling size gap between these two levels of reality, the first edition broke new ground in chemical illustration with an art program that juxtaposed the macroscopic and atomic views, and, wherever meaningful, the symbolic view in the form of the balanced equation. Examination of elementary general chemistry texts over the last decade reveals an increasing use of multiple representations.
An example described as a hallmark by Silberberg is shown in Figure 5. Figure 5 A three level illustration from M. In general, the use of sub-micro diagrams in assessment 16 has developed more slowly than the introduction of the use of the diagrams in text books.
Three case studies are presented each identifying a particular conceptual or instructional difficulty and a suggested pedagogical approach that addresses the difficulty. Developing skills in interpreting and constructing sub-micro diagrams with students from educationally disadvantaged backgrounds The conceptual difficulty is a lack of ability to relate the three levels of representation.
The strategy uses diagrams to link the sub-micro and the macro level, introduces the sub-micro level before teaching the symbolic conventions; and encourages students to draw and annotate their own drawings of the sub-micro level. Davidowitz teaches chemistry to students identified by the University of Cape Town as being from educationally disadvantaged backgrounds.
Instruction therefore, focuses on the use of teaching resources such as Figure 6 which introduces the relationship between the sub-micro and macro level at the start of the course prior to the use of any symbolic representations such as chemical formulae.
what is the difference between macroscopic and submicroscopic? | Yahoo Answers
This strategy intentionally focuses on diagrams at the sub-micro level to provide students with a foundation on which to build ideas such as atoms and molecules, elements, compounds and mixtures. Students are encouraged to engage with these concepts during the tutorial sessions where they work through a problem set in which they have to classify representations in terms of both the phase and composition of the substance. They are also presented with samples of substances and asked to draw the corresponding sub-micro representations which present a much greater challenge than simply identifying observable features presented to them.
Atoms touching, ordered or regular arrangement Colourless liquid, no fixed glucose shape; sweet taste. Glucose in water is an water example of a mixture. Molecules touching, no ordered arrangement; glucose molecules are found in between the water molecules Figure 6 An introduction to conventions commonly used in sub-micro representations 19 Sub-micro representations are used extensively in teaching the mole concept, stoichiometry, solubility and chemical equilibrium at UCT 1.
The following examples are typical of the questions used to probe links between the sub-micro and symbolic levels of representations as part of the assessment practice for this course. For example, students were asked to balance the equation shown in Figure 7. Key A B2 Figure 7 Balancing an equation presented as sub-micro particles In order to answer this question students had to identify the product as AB and realise that a balanced equation is always written using the smallest whole numbers ratios for reactants and products.
These 1 UCT; abbreviation for University of Cape Town, South Africa 20 results of the UCT study suggest that allowing students to engage with the material using multiple representations as recommended by Johnstone and Devetak et al. While some of the questions in text books make use of diagrams to probe conceptual understanding, very few questions require students to construct diagrams.
Assessment procedures used with first year students at UCT during the first semester of included having students construct diagrams. The questions shown in Figures 8 and 9 were used in class tests as formative assessment.
To answer the question shown in Figure 8 students had to interpret the diagram which is a more challenging exercise with a higher intellectual demand than the conventional style of question shown in Figure 9. The question shown in Figure 9 can be answered using only the symbolic level of representation. Consider the mixture of N2 and H2 shown in the diagram. Key Hydrogen d Draw a microscopic representation of the contents of the container after the reaction. Nitrogen Figure 8 Stoichiometry question based on a sub-micro diagram of the reactants.
The following reaction can be used to generate hydrogen gas from methane, CH4. Figure 9 A typical stoichiometry question on limiting reagents and amount of product formed in a reaction. In determining the limiting reagent, however, there were a lower number of correct responses than for the question in Figure 9 based on stoichiometry. The difference in performance is even greater for part c of both questions which essentially involves a determination of the amount of product formed in the reaction.
Students are clearly capable of solving stoichiometry problems using an algorithmic-style problem-solving template, Figure 10, while they find it more difficult to do so using sub-micro representations despite the opportunities to practice using the sub-micro representations in tutorials.
This finding demonstrates the greater intellectual challenge involved in interpreting the diagrams relative to problems involving only symbols as noted by de Jong and van Driel and Treagust et al. Just over a quarter of the cohort were able to draw a 23 correct representation of the reaction mixture, namely ammonia and the agent in excess. Almost a fifth of students drew a suitable sub-micro representation of the product molecules but did not include the reagent in excess.
About one third of the responses contained a wide variety of incorrect sub-micro representations. Two commonly occurring examples are shown in Figure Based on their responses to the question in Figure 8 above, the UCT cohort appear to have a better understanding of basic concepts of equations and reactions than students in a study reported by Mulford and Robinson These authors developed an instrument to investigate common alternative misconceptions about topics found in the first semester of traditional chemistry courses.
One of their test items focussed on the understanding of chemical formulae and equations using a sub-micro diagram for the reaction of sulphur and oxygen to produce sulphur trioxide. Students 24 were asked to choose the diagram which showed the results after the mixture had reacted as completely as possible according to the balanced equation shown.
2.3: Macroscopic and Microscopic Views of a Chemical Reaction
It could be argued that students may experience difficulties in understanding unfamiliar sub- micro diagrams which may contribute to their poor performance in answering questions as reported in the study by Mulford and Robinson These authors believe that this is not the case since the diagrams used as distractors for the question on sulphur trioxide were generated by students during the design of their instrument.
Interviews with students revealed that none of them had any difficulties in understanding the representations. Having students draw their mental model of the product of the reaction reveals misconceptions in understanding of the particulate nature of matter which could then be addressed in the classroom.
In addition her understanding of the subatomic level seemed to be interfering with her understanding at the atomic and molecular level. Another student, who had more chemical background knowledge, discussed his understanding of the representations: Why did you think this one was a compound referring to Figure 12 Student A The lines represented a bond.
Oh OK and you said the bonds mean a compound and then you looked at it twice, and what did you realise? Second time you looked at it you said it was an element — why did you say it was an element?
What do the circles represent? To me they represent an element. This student equated lines with bonds, and he associated bonds with compounds, forgetting that elements can also have bonds. He also equated circles with elements not atoms. Lastly another student, who was able distinguish the reality from the representation, did not relate the two at all.
I honestly have no idea when it comes to things like that. Yeah, So the real thing is so remote from the symbolic that… Student B: This student had no chemistry background knowledge and did not think about matter in a particulate way. This student did not link to the macro and sub-micro levels simultaneously but used them independently.
These results reveal difficulties that some students have in identifying the 26 significant components of chemical diagrams and the conventional symbolism that are used. To achieve this outcome, teachers can: Consistent with a constructivist approach, these suggested strategies 27 require students to demonstrate their understanding and receive feedback.
In this way, the diagram becomes an active tool rather than a passive tool for learning. There are three important facts that need to be understood in order to gain a better understanding of the sub-micro level: Figure 5 illustrates These three aspects are illustrated in Figure 5: Based on these three important facts, teachers and instructors must create opportunities for their students to learn to interpret sub-micro diagrams which are a feature of modern learning materials.
The conventions used in the sub-micro representations should be taught explicitly. Assessment in chemistry commonly emphasises numerically based problems, so reference to the sub-micro level can be marginalised or considered to be less important. An alternative 28 approach is to provide students with greater exposure to a variety of chemical diagrams of different formats. Having students construct their own diagrams has been shown to be effective in revealing their understanding of particular concepts.
Diagrams are a valuable teaching tool but should not be used in isolation since research has recommended the need to link sub-micro diagrams to other levels of representations in chemistry.
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What’re the Three Levels of Representation in Chemistry?
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