How many of you could recite, word for word, a definition you learned in school? When you first memorized the definition, you could state “inertia is a property of matter”, or “density is mass over volume”. However, you struggled to apply it to a new situation and maybe you were unsure of how to construct a model of what it meant.

As an educator, I have examined different approaches to help students build their vocabulary as a way of developing concepts. In the past, I gave students a list of vocabulary words to define using their textbook, or I simply gave them the definition through direct instruction. Even after these "riveting" lessons, their assessments demonstrated they lacked conceptual understanding despite being able to regurgitate a textbook perfect definition.

We know there is evidence that the textbook definitions do not help students because textbooks do little to engage students and do not help them use the terms in an authentic way and therefore retain the information¹. Additionally, teaching a dictionary definition assumes the definitions are situated in the dictionary, rather in the concept. Students only see the term as a dictionary definition without understanding how the concept developed or the applications of the term. For example, a student defining the Law of Conservation of Mass as “matter is neither created nor destroyed, simply rearranged” might not see its connection to balancing chemical reactions or Avogadro’s Hypothesis. By limiting students’ ability to develop their own definitions, the word itself can be limited to a definition and may not become a fully developed concept².

Figure 1: Vocabulary Card Sort document*

After I moved to Modeling Instruction^TM several years back, I put more emphasis on having students develop their own definitions. The goal was to have students situate their learning in an engaging and authentic activity and apply it to another context. After a paradigm lab or classroom demonstration, my students whiteboarded their data and analysis. Their board often included a particle diagram, a definition, and a symbolic representation. Afterward, in the resulting class discussion, students would come up with a working definition for terms such as volume, density, and pressure.

Until this year, I still hadn’t found a way for the students to develop definitions of terms such as pure substances, mixtures, elements, and compounds. The classroom activities, demonstrations, and video clips still had not solidified the terms for my students and they often remained confused at identifying particle diagram models. Textbook definitions might help some students in terms of rote memorization, but did not help them build a mental model of these terms. This time, I decided to have my student try a card sort to address the weakness I observed.

Figure 2: Sorting particle diagram cards into Pure Substance and Mixtures

I gave my students baggies of cards that had category titles and particle diagrams (figure 1). I instructed them to first find the labels for Pure Substances and Mixtures and put the category titles Elements and Compounds aside. Then, they took all the particle diagram cards out and sorted them into Pure Substances and Mixtures (figure 2). At first students thought they could easily sort the cards, but I began to walk around and asked them questions about their thinking. “Can you explain why you chose to put this card under Pure Substance?”

“What are the similarities that you see among the cards you put under Mixture?”

“What makes these cards different from each other?”

“Does it matter that this card has particles stuck together and this other card does not?”

“What difference does it make if the particles are drawn close together or spread far apart?”

This led to the students’ detailed discussions about why they put the diagrams into specific groups.

Figure 3: Sorting compound and element cards

My students then took the previously set aside category cards of Compounds and Elements and resorted all the images (figure 3). I once again circulated and asked questions about their choices, what were similar and what was different. This time, the students had more detailed conversations.

My students then divided their whiteboards into four quadrants.  In each quadrant they described the characteristics of the different categories and drew particle diagrams to give examples.

Figure 4: Student Whiteboard Example #1

When they finished, my students stood up in a circle and displayed their whiteboards (figures 4 and 5). The students used their evidence from classroom experiments, demonstrations, and discussions to justify their categories. Even after time within their groups, students still displayed misconceptions. They commonly described a pure substance as “one thing” and affirmed that a compound could never be separated into its components. The term “pure” generated an image of something unadulterated - unique - so to them it meant only having one type of particle.

Figure 5: Student Whiteboard Example #2

On the other hand, I found students had built clearer mental models about characteristics of mixtures. Therefore, I used their evidence and explanations to guide them in developing strong definition of the term. They discussed how they separated iron filings from sulfur using a magnet and developed procedures to separate sand, salt, and water. They concluded the components of mixtures maintained their own properties and their composition varied.

We took their model of mixtures and applied it to compounds. They had seen iron could not be separated from iron sulfide using a magnet indicating a new substance was created and it had different properties than its components. They had also used electrolysis to separate water into hydrogen and oxygen and tested for the different gases. They knew water didn’t make a popping noise with a burning splint and it definitely didn’t burn brighter with a glowing splint. Using this evidence, it seemed more likely that a compound was something new and not merely a mixture of two different substances. If a compound was not a mixture, it needed placement in another category. After the class came to consensus on all four definitions, they wrote them on their paper, drew a particle diagram, and gave an example.

The following assessment question showed a greater number of my students achieved proficiency on this learning objective than they had in previous years (figure 6). By making my students do the work of developing their own definitions, they situated their learning in the experience of seeing patterns and drawing conclusions. They internalized the terms and constructed strong mental models that they applied to different units.

Figure 6: Assessment question for objective 4.1

While not every unit can use a card sort, I found this was a quick, engaging, and authentic activity that allowed the students to be placed at the center of their own learning, to develop stronger models, and achieve the proficiency to help them succeed in chemistry.

*Download the Card Sorting Cards: 

sorting_activity.docx

sorting_activity.docx

1. Roth, W.-M.; McGinn, M.K. Review of Educational Research 1998, 68 (1), 35-59.

2. Brown, J. S.; Collins, A.; Duguid, P. Educational Researcher 1988, 18 (1), 39–42.

Chemistry is difficult to learn. Walk into any chemistry classroom, and you’ll be soon confronted with many abstract concepts. Abstract ideas have no physical form, and as a result, they are difficult to understand. Topics like the mole, quantum numbers, and the atom are tricky to comprehend unless they are related to something more concrete.

An analogy serves the purpose of bridging an abstract idea to familiar knowledge, and there are many favorites in chemistry education.

• A recipe for baking a cake can be used to grasp stoichiometry.
• Familiar units like the 'dozen' help students understand the mole.
• Preparing ‘smores’ (a classic campfire treat) aids comprehension of limiting reactants (see image 1).

Image 1: Students understand limiting reactants better with an analogy like 'smores.'

What Is An Analogy?

Simply stated, an analogy is a comparison between a familiar domain of knowledge and one that is not. The familiar domain is commonly referred to as the “analog,” and the “target” represents the unfamiliar. An analogy is used effectively when the knowledge held in the familiar domain is transferred to the unfamiliar domain, making it easier to learn.¹

Figure 1: The features of an analog are used to comprehend the target.

In a previous post, I provided a brief overview of pedagogical content knowledge (PCK), a unique form of teacher knowledge.^2,3 As a component of PCK, analogy use is a specialized teacher skill. However, teachers do not always apply analogies correctly, and misuse can actually interfere with student learning and lead to misconceptions.¹

Tips for More Effective Analogies

1. Teach Students About Analogy

Analogies are common in everyday life; however, students do not necessarily know why we use them or how they work. Although students learn how to define and recognize analogies in other courses, it’s still beneficial to teach students about analogy use in the context of science - tools to access complex ideas. As an example, the solar system is a common analogy for the atom. This particular analogy is an excellent reference for understanding the purpose and limitations of an analogy. Relating the solar system to the atom helps learners understand the different subatomic particles; the planets are analogous to the electrons, and the sun is analogous to the nucleus. However, the solar system is a limited analog because electrons exist in a cloud of probability rather than a discrete orbit. An analogy is merely a resemblance of the reality, rather than reality itself. So, before using an analogy, teach analogy.⁴

2. Analogies Should Be Simple and Easy to Remember

Students become confused and stop paying attention when analogies are too complex or lengthy. Since it's often not until the end of the analogy that the analog-target relationship is clarified, students must remain focused for the entire explanation. Students report a preference for simple analogies because they present a comprehensible idea to which they can fall back on when information becomes more complex. Students don’t even mind if an analogy is “stupid” as long as it is easy to remember and is something they can refer back to as support for further learning.¹

3. The Best Analogies Are Familiar

Ideally, analogies build on pre-existing and relevant knowledge. The more the students relate to the analog, the more effective the analogy will be. Analogies that use familiar topics and language increase the likelihood that students will engage with a difficult topic. For instance, students are three to four times more likely to pay attention to the familiar language of an analogy than to new scientific language. Furthermore, students are more interested when new information is connected to real-world experiences, especially when it impacts their daily lives.⁵

4. The Purpose of the Analogy Must Be Clear

Many students resort to mechanical use of an analogy, rather than a deep understanding of the target concept. This mistake often results when a student learns about the analogy without connecting the analog to the target knowledge. For instance, when asked to the describe the function of mitochondria, many students respond, “it's the powerhouse of the cell,” but they are unable to explain why this is an appropriate analogy. Adding to this problem, students who supply an acceptable analogy on an assessment are often rewarded with a correct response, even though they have not communicated a true understanding of the target. To increase its power, it's best to introduce the target concept before an analogy is used. Teach students that the analogy is not the target knowledge; rather, it's a tool to reach new knowledge.¹

5. Explain the Relationship Between the Analogy and Target Concept

Many students have difficulty seeing a connection between an analog and the target concept, yet, instructors often assume that all students have the ability to make those links. Teachers frequently create their own analogies after significant contemplation of a certain concept.  Consequently, they understand the relationship with the target better than anyone else. Since students are brand new to the concept, they are not able to recognize the same relationships, opening the door to misconceptions and a limited understanding of the target concept. So, prevent confusion by explaining how an analogy helps better understand the target concept.¹

6. Explain the limitations of the analogy

Analogies never completely describe the target concept, and many students can’t identify limitations. As a result, inappropriate ideas are often applied to the target, leading to additional misconceptions. With practice, students should be able to recognize limitations for themselves. Until then, when using analogies, it's wise to point out and discuss their limitations.¹

7. Use Visuals

Pictures and diagrams enhance the relationship between the analog and a target concept (see image 2). Visuals bring focus to the key aspects of the analog and make the analogy more memorable. As previously stated, abstract concepts have no physical form and as a result, they are difficult to learn. Pictures and diagrams assist learners when learning abstract ideas because they provide a concrete reference when constructing new knowledge. Chemistry is more abstract than other sciences; thus, it is necessary to use more visuals. This fact is evident by the increased use of pictorial analogies in chemistry textbooks compared to other science textbooks. An analysis of secondary science textbooks found that chemistry textbooks contained the highest level of pictorial analogies (29%) compared to an average of 16% in all science textbooks.⁶ Whenever the opportunity presents itself, supplement analogies with visual, especially when teaching particularly abstract concepts.

Image 2: Example of a pictorial analogy used to help learners understand activation energy.

8. Save Analogies for the Difficult and Challenging Concepts

When asked to describe situations in which analogies are not useful, students expressed that analogies aren’t necessary when concepts are “easy.” From the students’ point of view, they do not want extra, unnecessary information when they are trying to learn the important course material. On the other hand, students find analogies helpful when they are learning difficult concepts. So, save analogies for difficult concepts and help to avoid unnecessary information that could take the focus away from the course content.¹

Effective analogies are vital for teaching chemistry because it is such an abstract subject. With a little extra reflection and intentionally regarding analogy use, you can prevent misconceptions and improve student learning.

Please leave a comment; I would love to hear some of your favorite analogies for teaching chemistry.

References

1. Orgill, M., & Bodner, G. (2004). What research tells us about using analogies to teach chemistry. Chemistry Education Research and Practice, 5(1), 15-32.
2. Shulman, L. S. (1986). Those who understand: Knowledge growth in teaching. Educational researcher, 15(2), 4-14.
3. Shulman, L. (1987). Knowledge and teaching: Foundations of the new reform. Harvard educational review, 57(1), 1-2.
4. Brown, S., & Salter, S. (2010). Analogies in science and science teaching. Advances in Physiology Education, 34(4), 167-169.
5. Lemke, J. L. (1990). Talking science: Language, learning, and values. Ablex Publishing Corporation, 355 Chestnut Street, Norwood, NJ 07648 (hardback: ISBN-0-89391-565-3; paperback: ISBN-0-89391-566-1).
6. Curtis, R. V., & Reigeluth, C. M. (1984). The use of analogies in written text. Instructional Science, 13(2), 99-117.

In this article, I would like to introduce a procedure which involves the removal of copper from a solution through a process known as biosorption. I covered something similar in a previous ChemEd X blog¹, but in this article I will be running the experiment by using a different analytical method.

Biosorption is a method that can be used for the removal of pollutants from wastewater, especially those that are not easily biodegradable (heavy metals and industrial dyes)². Basically, it is a passive uptake of pollutants and it can be highly efficient and cost effective³.

It involves the use of waste adsorbents (they can be living biological ones⁴ as well) which are able to bind the toxic substances; cheap materials can be used and because of that this technique is likely to be a promising one. In terms of an industrial perspective, several other methods such as membrane filtration, nanotechnology treatments and electrochemical processing can be used to remove pollutants from wastewaters.

Of those innovative procedures, it seems that chemical precipitation is the most applied one since it features simplicity and quite safe operations. Its major drawback is that it is an excessive sludge production which actually needs a further treatment. Ion exchange and electrolytic recovery are successfully employed methods; however, they need a more sophisticated knowledge and maintenance to carry out the procedure in a proper and convenient way⁵.

Figure 1: lemon and orange peel powders

Reading some articles about this topic, it came out that some citrus fruit peels also can be used to conduct a wastewater treatment⁶; the pectin contained in the peelsis able to bind heavy metals such as lead, cadmium copper etc (see figure 1). Pectin is present in high quantities in the cell wall of a number of fruits and vegetables and it seems that carboxylate groups present in its structure, play a dominant role in heavy metals binding by fruit pectin. Therefore, I decided to test the capacity of lemon and orange peels to remove copper from a water solution.

Why copper? That heavy metal is present in many chemistry labs (in general as copper II sulphate) and its determination in a solution is quite easy by carrying out an iodometric titration; in addition, is not as hazardous as other heavy metals (cadmium, lead etc.) so its disposal is not a big issue. I found this experiment useful when it came to teach students about redox titrations; the topic is interesting and the experiment is fun since the solutions students are analyzing pass through a nice range of colors. In addition, the stoichiometry behind the whole process is not as straightforward as a classical titration (such as a strong acid-strong base one), therefore the experiment has to be planned more carefully by students; they should write down the reactions and figure them out in terms of moles and concentrations.

Equipment & Chemicals

• Lemon peel powder
• Orange peel powder
• 0.01 M Sodium thiosulphate - Na2S2O3 • 5H2O solution (it has to be standardized)
• 0.001 M Potassium iodate - KIO3 standard solution
• Potassium iodide - KI 0.02 g/ml
• Starch solution
• 2 M Hydrochloric acid - HCl solution
• 0.005 M Copper(II) sulphate pentahydrate - CuSO4 • 5H2O solution (concentration has to be exactly defined)
• Glassware (burette, Erlenmeyer flasks)

Experimental Procedure

This procedure has been planned out to minimize the production of generated waste such as copper I iodide.

The general procedure involves these steps:

1. Getting both the lemon and orange powders (I got that online since the product was available in a very fine form).
2. Preparation of a standard sodium thiosulphate solution.
3. Determination of the copper II content in a stock solution (through iodometric titration) by using the standardized solution indicated in Point 2
4. Addition of a certain amount of lemon peel powder in the copper II sulphate solution; that mix will be stirred overnight and filtered later.
5. Determination of the residual copper II contained in the solution (prepared in Point 4) through iodometric titration.

Technical details and calculations are reported in the Supporting Information file.

Standardization of Sodium Thiosulphate Solution

The preparation of the standard sodium thiosulphate solution is based on the following reactions:

Reaction 1: First reaction takes place between iodate (IO₃^-) with excess of iodide (I^-) in acid environment; since iodine (I₂) is produced, the solution turns brown/dark-brown.

IO₃^-+ 5 I^-+ 6 H⁺→ 3 I₂ + 3 H₂O

Reaction 2: Iodine is titrated with sodium thiosulfate standard; the solution eventually turns pale yellow. After the addition of starch, the solution turns blue/dark-blue (formation of the iodine-starch complex). Continuing the titration, the solution eventually turns colorless because of the consumption of iodine with subsequent formation of iodide ions; that is the endpoint.

2S₂O₃^2-+ I₂  → 2I^-+ S₄O₆^2-

Color changes happening during the process are shown in the picture below:

Figure 2: from left to right: 1.) Solutions of KIO₃ after the addition of KI and HCl. 2.) Solution immediately before the endpoint. 3.) Solution after the addition of starch. 4.) And of titration (color intensity depends on the amounts of chemicals used).

In Table 1 are reported the results I got (concentration of KIO₃ standard solution is 9.8130 x 10^-4 M):

Table 1: Sodium thiosulphate standardization data

In terms of technical aspects, determination of the concentration of copper II in the stock solution, is actually the same. The only different thing is the formation of copper I iodide (CuI) which appears as a white precipitate. Of course, depending on the concentrations used the amount of precipitate is different. As I said before, I didn’t want to manage too much waste; therefore, I used small amounts of chemicals. Moreover, I found that a significant amount of copper I  iodide makes the titration harder to carry out (in presence of this precipitate, the pale yellow color of reduced iodine is not easy to see and mistakes are around the corner).

Determination of Copper II Sulphate Concentration

Reactions involved are the following (color sequence is the same as that shown in Figure 2):

Reaction 3: This reaction takes place (in acid environment) between Cu₂⁺ ions and I^- ions:

2Cu²⁺+ 4I^- →  2CuI_(s) + I₂

The presence of these two products makes the solution cloudy (copper I iodide is a solid) and brown/dark-brown (see Reaction 1) at the same time.

Reaction 4: This reaction involves the reduction of the iodine produced in Reaction 3 with the sodium thiosulphate standard solution. Solution eventually turns pale-yellow (as described in Reaction 2) so starch has to be added in order to detect the endpoint more accurately:

2S₂O₃^2-+ I₂   →  2I^-+ S₄O₆^2-

We notice that we are titrating the iodine generated in Reaction 3; moreover, the stoichiometric ratio between the thiosulphate ions and the copper (II) ions is 1:1. Final results are in the table below:

Table 2: Copper II Sulphate Standardization Data

Effect of Citrus Peel Addition on Copper II Concentration

The final step is the addition of the lemon and orange peel powder into two different standardized solutions of copper II sulphate. In 50 ml of each solution, I added 1 g of each powder and I stirred the mixture overnight; that is followed by a filtration step in order to clear up the mixture. Another iodometric titration allows us to figure out the effect of the peels on the solution tested. Of course, the addition of the lemon powder gives rise to a cloudy suspension and a slight change of color could happen as well. Although a good filtration clears up the liquid (see Figure 3), tiny particles can pass through the filter (that especially happened for the lemon peel powder solution which looks cloudy even after filtration).

Figure 3: left - copper solutions after the addition of peel powder; right - copper solutions after filtration

The yellowish color of these solutions could make the titration harder in terms of color changes; luckily, iodine brownish color takes over and the titration can be carried out with no significant difficulties (in any case, I would suggest you to slowly add the titrant in order not to overshoot the endpoint).

In the table down below I reported the concentration of copper before and after the biosorption process (concentrations are in mol/L and mg/ml):

Table 3: effect of lemon and orange powder on the concentration of copper(II) sulphate in the solution

Given these results, we can calculate the biosorption capacity by using the following formula:

Figure 4: Biosorption capacity of lemon and orange powder

According to the graph, lemon peels seem to be slightly better than the orange ones. I do think though that results are also dependent on the concentration of the peels as well as other factors (pH, temperature etc) so these aspects should be investigated further.

Of course, several different fruit peel powders can be tried out (kiwi, banana, apple etc); I decided to try lemon and orange ones in order to focus on some citrus fruit first but I will probably consider the possibility to test other varieties along with some variations in terms of pH, temperature etc. In addition, other methods such spectrometry can be used.

By doing this experiment, I hope I have given you some inspiration for new topics to cover in your lessons! As usual, I’m open to suggestions and advice. Happy experimenting!

References

1. Amato, A., Removal of a Dye by Adsorption on a Low-Cost Material – A Quick Test, ChemEd X blog post published 6/15/18
2. Pennesi, C.; Rindi, F.; Totti; C., Beolchini; F. Marine Macrophytes - Biosorbents,   https://www.researchgate.net/publication/265097030_Marine_Macrophytes_Biosorbents - Omega-3 Fatty Acids Produced from Microalgae (pp.597-610) from Springer Handbook of Marine Biotechnology (2015)
3. Silke Schiewer; Santosh B. Patil; Modeling the effect of pH on biosorption of heavy metals by citrus peels. Journal of Hazardous Materials 157 (2008) 8–17
4. F. Pagnanelli; M. Petrangeli Papini; M. Trifoni; and F. Vegliò. Environ. Sci. Technol., 2000, 34 (13), pp 2773–2778
5. M.A.Barakat. Arabian Journal of Chemistry (2011) 4, 361–377
6. Khairia M. Al-Qahtan. Journal of Taibah University for Science 10 (2016) 700–708

I’m a jigsaw puzzle fan. But, I’m a bit particular about my puzzles. I like photos rather than illustrations. It needs to be large enough to take awhile, but not so big that it takes up house space for weeks. It needs to be challenging, but not irritatingly so (those with great swathes of green hills or blue sky with all the pieces nearly identical, for example).

I’m also a fan of puzzles in the classroom. Occasionally a jigsaw, but more often individual puzzles with letters or shapes. They don’t require content knowledge, but help to build a student’s willingness to try different things and stick to a task, even if they would prefer to find the solution instantly. I like to have them on hand as a fun but still useful filler. (Sarah Carter’s offerings at Math Equals Love blogare some favorites).

O’Halloran’s Puzzle to Build Organic Molecules with Sticky Notes (available to JCE subscribers*) is something I can add to the rotation, as a science-specific puzzle. Students each receive a sticky note with an element symbol and bonds extending from it. There are seven separate molecule templates to visit, and students work together to figure out the correct locations for the sticky note squares. The bonding must be chemically correct, and the sticky part of the square must remain at the top (no rotating). For example, one square shows a carbon with a single bond to the left and a triple bond to the right. That student knows to look for another triple bond. When I tested it, I chose not to use sticky notes. Other options would be cards (laminated if they will be reused) on a chalkboard or whiteboard with magnets to rearrange them, with the cards marked to show which side is the top.

The author states that there is only one correct classroom solution (see figure 1). However, there are possibilities that are still allowed based on the guidelines. You can see that my daughter, a junior chemistry student, came up with some variations the first time working through the puzzle as an individual (see figure 2). O’Halloran mentions, “If students begin assembling uncommon molecules (hydrazines, alkoxyamines, etc.), then gently steer them toward common molecules.”

Figure 1: Reprinted with permission from Puzzle to Build Organic Molecules with Sticky Notes, Kevin P. O’Halloran. Journal of Chemical Education, 96 (4), 725-728. Copyright 2019 American Chemical Society.

Figure 2: An additional “solution” that still follows activity guidelines (from this author).

Although the puzzle does link to categories of organic compounds, it can be used even if students are not familiar with them. O’Halloran describes its use as “a good bridge between students learning Lewis dot diagrams in general chemistry and learning functional groups and classes of organic compounds in organic chemistry. … It can also be used as a primer before teaching these topics in class.” It makes students aware that there is a variety of organic compounds. Although the JCE keywords do not include high school, I could see using it there and even at the middle school level. In the American Chemical Society’s free Middle School Chemistrycurriculum that I use, it would fit at the end of chapter 4, after students use Lewis dot diagrams.

More from the April 2019 Issue

Mary Saecker’s JCE 96.04 April 2019 Issue Highlights has a bonus this month. In addition to its usual unpacking of the latest Journal issue, she heads to the archives to share resources for April’s Chemists Celebrate Earth Week 2019 theme “Take Note: The Chemistry of Paper.” There are several JCE Classroom Activities in the list. With their use of materials from the grocery store and ready-to-use instructor and student handouts, they’re easy to use with classes or for outreach. I’m partial to Colorful Lather Printing. Even after having done it hundreds of times at Journal booths, the wonder and beauty of it never grows old.

What else have you used from the Journal in your classroom? Share! Start by submitting a contribution form, explaining you’d like to contribute to the Especially JCE column. Then, put your thoughts together in a blog post. Questions? Contact us using the ChemEd X contact form.

            *See Accessing Cited Articles

"In honor of the International Year of the Periodic Table this series of articles details the Element of the Month project developed by Stephen W. Wright (SWW), Associate Research Fellow at Pfizer Inc., and Marsha R. Folger (MRF), chemistry teacher (now retired) at Lyme – Old Lyme High School in Connecticut. Read The Element of the Month - An Introduction for an overview of the project and links to the other articles in the series." - Editor 

The third element highlighted in our Element of the Month program is nitrogen. While the relevance of nitrogen to the students’ lives is generally obvious to them, it is likely that the students have little familiarity with nitrogen despite the fact that they are usually aware that they walk in an atmosphere that is about three quarters nitrogen.

Occurrence in Nature

Students will respond that nitrogen is to be found as the uncombined element in the air, which is correct. In fact nitrogen is the most abundant free element on Earth. We ask how much of the atmosphere is nitrogen to remind them that nitrogen forms about 78% of the atmosphere, a point to which we will refer later. We then ask where else nitrogen is to be found in nature, and generally a little more prodding is required to provoke the answer that nitrogen is found in proteins.

Figure 1: Nitrogen containing products

Uses

We open this part of the discussion with the conclusion that nitrogen’s primary use then is that it is essential for life as a constituent of amino acids and therefore proteins. In fact, the “amino” term in the name “amino acid” is a nod to the nitrogen content. It follows, therefore, that some of nitrogen’s other uses are directed toward getting the element incorporated into proteins since humans lack the ability to synthesize amino acids. Nitrogen is the primary component of fertilizers. What else do we use nitrogen compounds for? We solicit ammonia, explosives and pyrotechnics, and certain plastics, such as nylon and Kevlar, as answers. We have on display items that contain nitrogen compounds (see figure 1). These can be items such as a pair of stockings, a container of fertilizer, a jar of protein supplement powder, a can of tuna, a bottle of household ammonia, a bottle of an ammonia-containing cleaner such as a glass cleaner, and if permitted, a box of highway flares. For safety and convenience, these containers may be empty and stored in a small box from year to year.

Figure 2: Ampule of nitrogen gas

Physical Properties

Clearly nitrogen is a gas at room temperature (figure 2). When asked, students will usually recall that liquid nitrogen is extremely cold. In fact its boiling point is -196 °C. We ask the students what such extreme cold would be useful for. Some possibilities include flash freezing of food or preserving tissue specimens. At this point, we announce that we have some liquid nitrogen and we proceed to do some cryogenics demonstrations to show what happens to items that contain water when frozen to such low temperatures. Wearing cryogenics gloves or ski gloves in addition to customary lab safety wear, we start with a few grapes, which are held in the liquid nitrogen until bubbling subsides and then placed on a block of wood and smashed with a hammer.¹ We repeat the process with a marshmallow, which generally produces much amusement. A tennis ball comes next, which can either be broken with a hammer or thrown on the floor. Students will be more surprised to see that a balloon touched to the surface of liquid nitrogen becomes deflated.² They will quickly understand why as we engage them to explain what they are observing as the experiment proceeds. Further, this process can be repeated. Lastly we freeze a carnation or two and crush the frozen blooms in the palm of a gloved hand. It is possible to hammer a nail with a frozen banana but this demonstration takes some time for the banana to freeze and requires some practice to establish the technique of hammering and the choice of appropriate nails and wood.³

Figure 3: Production of ammonia from nitrogen and hydrogen gases

Chemical Properties

Nitrogen is inert and does not support combustion. We show that a burning splinter of wood and a birthday candle are extinguished when lowered into a jar filled with nitrogen. We emphasize the strength of N-N triple bond and explain that’s why most nitrogen is found uncombined in the air, because any nitrogen that does end up as the element is essentially in an energy “hole” from which it is difficult to escape. The inert nature and low cost of nitrogen are useful when you want an oxygen free atmosphere around something, for example when welding or packaging salad mixes. On the board, we show the equation for converting nitrogen to ammonia, and emphasize that energy is needed to make the reaction go forward (figure 3). We note that the reaction is carried out by chemical factories to make ammonia for fertilizers, and also by certain bacteria, and that’s how nitrogen gets from the atmosphere into the food chain.

Video 1: Ammonia Fountain* 

Ammonia

For these experiments we have been fortunate to have access to a small cylinder of anhydrous ammonia gas. We emphasize that ammonia is a gas, with a boiling point of -33 °C, not a liquid as found in the supermarket. It has a pungent and familiar odor. We show how amazingly soluble ammonia gas is by passing ammonia gas from the cylinder (noting that it is a colorless gas) into an empty, stoppered 500 mL Erlenmeyer flask. The outlet is passed into a 1 L beaker of water containing a little phenolphthalein. When ammonia begins to pass into the beaker, the water will turn pink showing that the solution has become alkaline. Then we shut off the ammonia supply and watch as the pink water is pushed back from the beaker into the Erlenmeyer flask, practically filling the flask. The ammonia fountain if a favorite demonstration of many chemistry instructors (see video 1 above).⁴Why does that happen? We emphasize the very high solubility of ammonia in water and note that 1 mL of water will dissolve nearly 1300 mL of the gas at room temperature. Most students will have never observed the phenomenon of a highly water soluble gas before. We note that the water solution of ammonia in the Erlenmeyer flask is the usual form of ammonia that consumers encounter.

Figure 4: The “Poor Man’s ammonium fountain set up

Many teachers would like to perform the ammonium fountain demonstration, but don't have the glassware shown in video 1. See what some call the "poor man's ammonium fountain" in figure 4. 

Figure 5: The reaction of ammonia and hydrochloric acid results in a cloud of ammonium chloride.

Being a base, ammonia combines with acids. We write the equation for the reaction of ammonia with hydrochloric acid on the board, and then place a few milliliters of diluted ammonium hydroxide on some paper toweling in an evaporating dish, and a few milliliters of diluted hydrochloric acid on some paper toweling in a second evaporating dish (alternatively, the two pieces of paper toweling may be placed side by side in the same evaporating dish).⁵A cloud of white ammonium chloride “smoke” will appear, and we explain that this is formed from the reaction between the two gases escaping from the two solutions (see figure 5).

Figure 6: Some of the nitrogen oxides found in nature

Nitrogen Oxides

We explain that, under appropriate conditions, nitrogen will form compounds with oxygen. At the board, we show the formulas for the three nitrogen oxides (figure 6). It’s NO₂ that often makes urban atmospheres hazy and yellow, and note that we’ll discuss NO₂ further later on. Students will usually have some familiarity with nitrous oxide, N₂O. We note that nitrous oxide is colorless but not odorless or tasteless – it actually has a rather sweet taste. We also note that is the only other gas besides oxygen that gives a positive glowing splint test, which was demonstrated last month. In fact nitrous oxide supports combustion fully as well as oxygen. Why might that be? We emphasize the stability of the N₂ molecule and can see that N₂O is almost N₂! If a source of nitrous oxide is available, the glowing splint test may be performed in a jar of nitrous oxide, demonstrating that N₂O supports combustion.⁶ 

We note that nitrogen - oxygen bonds are found in nitrates too. What products contain nitrates? We solicit gunpowder, fireworks and explosives for answers. We explain that nitrogen wants to form strong N-N triple bonds, not weak N-O bonds, thus nitrates easily lose their oxygen atoms to reducing agents, and this is how pyrotechnics and explosives work. We demonstrate the oxidizing power of nitrates by dropping small charcoal pieces, one at a time, into a small porcelain evaporating dish containing potassium nitrate that has been heated to melting over a gas burner.⁷ We shut off and remove the burner immediately prior to adding the charcoal pieces.

The combustion of nitrocellulose, used in modern propellants, may be demonstrated byigniting pieces of a broken ping pong ball.⁸ A video showing the combustion of ping pong balls may be found in Tom Kuntzleman's ChemEd X blog post, A Simple, yet Dramatic Chemistry Experiment with Ping Pong Balls.⁹

Nitric Acid

We always make sure that we have time remaining to discuss nitric acid and reenact Ira Remsen’s investigation of it. We explain that concentrated nitric acid is a very corrosive acid and powerful oxidizing agent. We show, by equations previously written on the board, that nitric acid converts toluene into TNT and cellulose into nitrocellulose, which are explosives that we just talked about.

Figure 7: Ira Remsen Equation

At this point we perform Ira Remsen’s copper / nitric acid experiment (see the equation in figure 7), reading aloud his description of the experiment but explaining that, for safety, we will perform the experiment in a 1 L flask in a fume hood and not on the teacher’s desk!¹⁰ We pour 5 mL of concentrated nitric acid into the flask and add a penny. If desired, the experiment may be projected by video camera to improve visibility. The immediate fuming of the liquid, the rich blue color of copper(II) nitrate, and the clouds of red –brown NO₂ gas never fail to impress the class. We dilute the reaction with a large volume of water in the hood to stop the reaction, then pour the mixture through a funnel to recover the penny, which may be shown to the class after washing and drying. In a bit of humorous theater, we produce an old pair of cotton pants bearing numerous acid holes and claim them to belong to Remsen himself. Lastly, we hand out copies of the paper below as the students leave the classroom. Readers can download a pdf of the script below. You can view a smaller scale version of this demo in video 2 below.

Video 2: A few drops of concentrated nitric acid are place on a pre-1982 copper penny.*

The Story of Ira Remsen¹¹

“While reading a textbook on chemistry, I came upon the statement, ‘nitric acid acts upon copper.’ I was getting tired of reading such absurd stuff and I determined to see what this meant. Copper was more or less familiar to me, for copper cents were then in use. I had seen a bottle marked ‘nitric acid’ on a table in the doctor’s office where I was then ‘doing time!’ I did not know its peculiarities, but I was getting on and likely to learn. The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words ‘act upon’ meant. Then the statement, ‘nitric acid acts upon copper,’ would be something more than mere words. All was still. In the interest of knowledge I was even willing to sacrifice one of the few copper cents then in my possession. I put one of them on the table; opened the bottle marked ‘nitric acid’; poured some the liquid on the copper; and prepared to make an observation. But what was this wonderful thing which I beheld? The cent was already changed, and it was no small change either. A greenish blue liquid foamed and fumed over the cent and over the table. The air in the neighborhood of the performance became colored dark red. A great colored cloud arose. This was disagreeable and suffocating—how should I stop this? I tried to get rid of the objectionable mess by picking it up and throwing it out of the window, which I had meanwhile opened. I learned another fact—nitric acid not only acts upon copper but it acts upon fingers. The pain led to another unpremeditated experiment. I drew my fingers across my trousers and another fact was discovered. Nitric acid acts upon trousers. Taking everything into consideration, that was the most impressive and, relatively, probably the most costly experiment I have ever performed. It resulted in a desire on my part to learn more about that remarkable kind of action. Plainly the only way to learn about it was to see its results, to experiment, to work in a laboratory.”

the_story_of_ira_remsen.pdf

the_story_of_ira_remsen.pdf

*more videos from the ChemEd X Collection are available by subscription

References and Notes

1. (a) Conant, James Bryant; Black, Newton Henry New Practical Chemistry; Macmillan: New York, 1940; pp. 267-268; (b) Summerlin, Lee R.; Borgford, Christie L.; Ealy, Julie B. Chemical Demonstrations: A Sourcebook for Teachers Volume 2, 2nd ed.; American Chemical Society: Washington, DC, 1988; pp 20-21.

2. A video showing the behavior of a balloon in liquid nitrogen may be found in Tom Kuntzleman's ChemEd X blog post, Chemical Mystery #4: The Case of the Misbehaving Balloon. 

3. The banana must be held in the hand protected by heavy, cold weather gloves. We use roofing nails which have large heads and pound them into a very soft piece of pine. Even so, the banana will usually shatter quickly.

4. Several versions (including the one shown) of the ammonia fountain can be found on the ChemEd X Video page. See also (a) Ford, Leonard A. Chemical Magic, 2nd ed.; Dover: Mineola, NY, 1993; pp 33; (b) Conant, James Bryant; Black, Newton Henry New Practical Chemistry; Macmillan: New York, 1940; pp. 282.

5. (a) Ford, Leonard A. Chemical Magic, 2nd ed.; Dover: Mineola, NY, 1993; pp 91; (b) Conant, James Bryant; Black, Newton Henry New Practical Chemistry; Macmillan: New York, 1940; pp. 285.

6. Conant, James Bryant; Black, Newton Henry New Practical Chemistry; Macmillan: New York, 1940; pp. 303.

7. Stone, C. H., J. Chem. Educ., 1943, 20 (4), 200.

8. Summerlin, Lee R.; Borgford, Christie L.; Ealy, Julie B. Chemical Demonstrations: A Sourcebook for Teachers Volume 2, 2nd ed.; American Chemical Society: Washington, DC, 1988; pp 105.

9. Tom Kuntzleman's ChemEd X blog post, A Simple, yet Dramatic Chemistry Experiment with Ping Pong Balls.

10. See Michael Morgan's ChemEd X blog post, My First Day Demonstration. 

11. The script was published in F. H. Getman, "The Life of Ira Remsen,"Journal of Chemical Education 1940, pp 9-10.

Note that nitric acid is usually made and sold as a 70% solution in water (70 grams of HNO₃ in 100 grams of solution), containing about 16 moles or 990 grams of nitric acid per liter.

What: 2YC₃ (Two-Year College Chemistry Consortium) summer conference in conjunction with the 50^th ACS Central Regional Meeting (CERM)

Where: Midland, MI

When: June 4-5, 2019

Registration:https://acscerm2019.org/

Registration Cost: $49 (by April 30); $99 (after April 30)

Greetings ChemEd Xchange Community:

My name is Scott Donnelly, editor for the Two Year College (TYC) component of ChemEd Xchange. This is my first of what likely will be many contributions over the coming years. Since this is my inaugural post as the TYC editor perhaps I should let you all know a bit about myself and my educational philosophy.

A Bit About Myself: I'm an outdoor enthusiast (preferring a forest or lake or canyon- bugs included- to four walls anytime), am a hobbyist woodworker, have recently taken up the ancient art of archery (recurve and flatbows), love to canoe (Voyageurs National Park is at the top of the list), teach a Zombie Apocalypse wilderness survival class at 'my' college, am a Search And Rescue (SAR) deputy, would have chosen- if I could do it all over again- to be a mapmaker/cartographer instead of a chemistry faculty, and once I retire want to begin a second career as a national park ranger (preferably in Glacier or North Cascades National Parks). What better way to make a small amount of money than take people on leisurely hikes across and through breath-taking landscapes.    

Educational Philosophy: With missionary zeal I've taught the gospel of general and organic chemistry at Arizona Western College (AWC) in Yuma, AZ since 1995. During the past 24 years I've had a variety of faculty and quasi-administrative positions. Like many of you I've seen instructional ideas come and go while some though have endured and now are commonly interpreted as 'Business as usual.'Having taught the full spectrum of chemistry classes full-time to over 5000+ students, I postulate- based on empirical experience and observations- that there really is no one teaching style or method that always (the key word) delivers a constantly high educational "bang for the buck" ratio. Not surprisingly, as I've experienced numerous times a specific teaching method or approach for a certain topic will fail perhaps miserably one semester while the next semester with a different group of students the same method is a rousing success.

Predicting the success or failure- however such indicators are defined by the faculty doing the method- of a particular teaching method with some acceptable degree of accuracy or even predictability is- to me at least via my 'boots on the ground' experience- not reliable. For me after doing this for nearly a quarter of a century the best way to find out the efficacy of a teaching method is rather straight forward- 1) keep it relatively simple, 2) then try it, 3) modify if necessary, and 4) try it again before possibly forgoing it if deemed by the faculty as unsuccessful after repeated attempts. Any teaching method, even the highly criticized and in some instances vilified lecture approach, when done properly and well, will, for most motivated students, be effective in accomplishing its intended outcomes.

Cheerio...SJD

Three Dimensional Assessments

Next Generation Science Standards (NGSS) or some version of the standards have been adopted in many states across the country. The phenomenon based teaching style called for in the standards, have raised questions about the ways in which three dimensional student learning should be assessed. My district recently provided a professional development session focused on utilizing three dimensional formative assessments in the classroom. The ideas I learned in the session as well an an activity for students to engage in formative assessment are outlined below.

What are Formative Assessments?

Formative assessments are utilized by educators to stay aware of what students actually know or do not know about a topic as well and provide evidence of student learning. When utilizing formative assessments with the end educational outcome in mind the teacher and student engage in a process of evaluating what learning has taken place and evaluate and fine-tune the next piece of learning that needs to occur. Formative assessments have no point values attached to them and are “low stakes” means for me to continually check in with my students. When designing these assessments, inclusivity and the equality of the various types of learners need to be kept in mind so that the interest and prior knowledge of all students are addressed. For example, a students lack of exposure or prior knowledge about a phenomena should not impede their ability to correctly answer the task at hand. Thus the assessments should be relevant to the learners and promote self- reflection, self- learning and social learning and are deliberate tools to measure what actions need to be taken to promote the process of learning science, as opposed to summative assessments which measure what students have learned with focus on a particular product. Formative assessments should be utilized throughout the unit and the following model can be used to guide the process. The teacher clarifies the intended learning goal and then provides a task and will elicit evidence of student learning. The teacher and student can then interpret that evidence and act on the evidence to clarify or modify the learning goal (see figure 1).

Figure 1: The Formative Assessment Process (Adapted by Simpson & McCulloch from Ruiz-Primo & Furak 2007)

Types of Formative Assessment

• Data Driven Decision Making- uses benchmark assessment to identify areas of improvement
• Strategy Focused- tools and practices that can be routinely used by the teacher to provide feedback and engage the students in learning
• Cognitive- examines the social nature of learning to assess how students knowledge is utilized as they  engage in practices similar to those that a disciplinary expert in that subject would
• Cultural- the teacher elicits information that students bring with them from outside the classroom including their knowledge, interests and experiences and applies this way of knowing, being and learning in the natural world that is specific to science.

How to Provide Formative Assessments

• On the fly check ins
  • Conversations with and between students
• Curriculum embedded
  • Exit-tickets
  • Do-Nowes
  • Criterion based rubrics to evaluate student performance

Formative assessments should not be graded for points or should have a low stake value. For instance: points for effort in the grade. The purpose is to examine a student performance in a way that is manageable for the teacher.

Redox Formative Assessment

One of the tools I have found most beneficial for use as a means of formative assessment is the set of probes that Page Keeley has written for various topics. I collaborate with chemistry teachers in my area and recently, we wrote our own probes for oxidation and reduction (see figure 2). I decided to try them out for my oxidation and reduction unit as a formative assessment to find out what students initial conceptions were at the onset of the topic as well as to circle back to at the end of the unit as evidence of student learning.

Figure 2: Example redox probe

Students read the probe and had to choose one or more answers they agreed with and described their thinking as well as provided an explanation for their answer. Student then placed a yellow sticky note for the first choice, a blue sticky note for the second choice, and a green sticky note on the wall to show their prediction. The purpose of the post-its was to have a quick visual representation of students’ initial conceptions. The whiteboard was divided into three columns: 1, 2 and 3. The students then were broken up into groups, where  they met in a designated area with other classmates that shared the same first choice. As a group, the students came up with an argument to support the group’s rationale for the best answer. A group member was chosen to write the group’s rationale on a large whiteboard.

In the reaction between aluminum and copper(II) chloride oxidation is occurring.

How would you describe oxidation?

1. Only metals can be oxidized.
2. Oxidation is the loss of electrons.
3. Oxygen is required for oxidation to occur.

Student are asked to again describe their thinking and provide an explanation for their answer. Students revisited with their group, and added more points to support their argument. If students no longer agreed with their  group’s argument, they could move to a group that better fit their view.

Students are then given one final probe.

During the Haber process, ammonia is synthesized from nitrogen gas and hydrogen gas, oxidation is occurring.

How would you describe oxidation?

1. Only metals can be oxidized.
2. Oxidation is the loss of electrons.
3. Oxygen is required for oxidation to occur.

Student were asked to again describe their thinking and provide an explanation for their answer.  Students revisited with their group, and added more points to support their argument. If students no longer agreed with their group’s argument, they could move to a group that better fit their view. A spokesperson from each group then shared each group’s points and the whiteboards were left until more information was learned and we could re-visit each phenomena as a class following additional instruction. At the end of the unit, students were required to write a reflection of how their learning and initial conceptions changed over the course of the unit. All students stated that the phenomena helped keep them engaged in the learning. One student explained that while the learning of oxidation numbers in the beginning of the unit was tedious and he did not enjoy it, at least he knew the intended outcome would help him understand something he did care about, uncovering the answers to the phenomena.

Resources

ACESSE Resource A - Introduction to Formative Assessment to Support Equitable 3D Instruction, OER Commons - Open Educational Resources (accessed 4/25/19)

Black, P., & Wiliam, D. (2009). Developing the theory of formative assessment. Educational Assessment, Evaluation and Accountability (formerly: Journal of Personnel Evaluation in Education), 21(1), 5.

Garrison, C., & Ehringhaus, M. (2007). Formative and summative assessments in the classroom.

Keeley, P. (2015). Science formative assessment, volume 1: 75 practical strategies for linking assessment, instruction, and learning. Corwin Press.

Keeley, P., Eberle, F., & Dorsey, C. (2005). Uncovering student ideas in science: Another 25 formative assessment probes(Vol. 3). NSTA press.

Ruiz‐Primo, M. A., & Furtak, E. M. (2007). Exploring teachers' informal formative assessment practices and students' understanding in the context of scientific inquiry. Journal of research in science teaching, 44(1), 57-84.

Shepard, L. A. (2000). The role of assessment in a learning culture. Educational researcher, 29(7), 4-14.

This is Part 2 of a 5-part series on National Board Certification in Chemistry. This post will focus on Component 1 - The Test.*

As a teacher, I am used to administering tests, not taking them. So, as I waited to take my National Board Assessment, I was nervous. Thoughts were running through my head, "Did I study enough? Will they ask me something I don't know? Wait - Is this what my students feel like?"

Component 1 of National Board Certification is a computer-based assessment testing content and pedagogical knowledge related to an area of expertise. It includes three essays weighted at 6.67% each and a multiple-choice section weighted at 20% of the overall National Board score. Component 1 (highlighted in yellow in Figure 1) is the largest percentage of the total National Board score at 40% as it is one of two performance-based tasks. An area of expertise in Chemistry, Biology, Physics, or Earth and Space Science will be the focus of your assessment. While questions will be answered from all areas of science, more in-depth questions will be asked in the area of expertise.

Despite my nerves, I earned some of my highest National Board scores in Component 1. While I cannot discuss questions on the assessment, I can share how I prepared for the assessment and what I would do differently.

Figure 1: Breakdown of National Board Score

Multiple Choice Section

There are 45 multiple choice questions to answer in 60 minutes. These questions test your knowledge of Science Practices (20%), Content Knowledge of Chemistry, Biology, Physics, and Earth and Space Science (45% in expertise area and 15% from other areas), and Curriculum and Instruction (20%). The National Board Component 1 Instructions contains some sample questions to use as practice. The area of expertise I selected was Chemistry. I currently teach AP Chemistry, Honors Chemistry, and Chemistry. I have taught Physical Science and Biology in the past. While I could walk into any Chemistry or Biology class and “chalk talk” any topic on the fly, I was not as strong with Physics or Earth and Space Science content. I had short conversations with my Earth Science and Physics colleagues after school about common misconceptions. I did borrow an AP Physics textbook to study, but returned it the next day joking, “I think I will just plan on getting these questions wrong if they ask me.” I took a few old National Chemistry Olympiad tests to help me study for the Chemistry content questions and I utilized AAAS assessments online to practice questions focusing on common student misconceptions in all areas of science. I wouldn’t do anything differently next time. It was actually kind of fun taking this part of the test - crazy, right?!

Essay Section

There are three essay questions to complete in 90 minutes (30 minutes each). The first essay is called Data Analysis and essentially asks you to analyze a student lab report. The second essay is called Contexts of Science and asks you to connect a historical moment in science to various scientific disciplines and society. The last essay is called Development of Scientific Concepts and asks you to describe how to best teach a concept. There are sample questions of each type of essay in the National Board Component 1 Instructions and online through the Component 1 Tutorial. The tutorial is especially helpful in minimizing technology stress on the day of the test. I spent more time preparing for the essay questions compared to the multiple-choice section. At first glance, I thought the essay questions were pretty straight-forward until I tried typing out my answers in 30 minutes. When my 30-minute timer went off the first time, I was only halfway through my response. I had to re-adjust my strategy for answering essay questions. I needed to find ways to shorten my answers. I asked myself, “Am I clearly answering what is asked in the question? Am I justifying when they question is not asking me to justify? Am I repeating thoughts? Is there a shorter way of saying this?” I also analyzed the essay rubrics in the National Board Component 1 Instructions to make sure I was addressing the necessary Science Standards in my answers when appropriate. If I had to do it again, I would have spent even more time practicing typing-out key phrases to the essay questions. I would have reached out to an English teacher to help me make my sentences more succinct. It was a challenge getting all my thoughts typed into one 30-minute essay.

The Day of the Test

Finally, I want to discuss the level of security for this assessment. When I signed up to take Component 1, I thought I would be able to take the test online at a local college (across the street from me). I was surprised to learn Component 1 was taken at an official Pearson Testing Center. My closest center was 45 minutes away. The waiting room was filled with university students taking various board exams. Testing slots are only available on certain days and times. When you receive your email from National Board to sign up for your testing day, sign up right away to reserve the best date, time and location. I found many of the testing times fell during the school day and would require me to take a personal day to take the test. By signing up early, I was able to select a day two weeks after school ended, so I could have time to prepare. The National Board’s Assessment Center Policy and Guidelines will help you learn more about the logistics of Component 1.

Component 1 of National Board Certification is a chance to “show off” all the wonderful content and pedagogical knowledge you have acquired and mastered over your teaching career. While I found parts of the preparation nerve-racking, I also found it rewarding when my scores validated my mastery of chemistry content. Good luck in your studies! Next month I will discuss Component 2 of National Board Certification – The Differentiation Portfolio.

*Read Part 1 of this series My Hero's Journey to National Board Certification.

CITATIONS/ACKNOWLEDGEMENTS/SUPPORTING INFORMATION:

National Board for Professional Teaching Standards, National Board Component 1 Instructions, http://www.nbpts.org/wp-content/uploads/AYA_Science_Component1.pdf, Pearson, 2018 (accessed 4/29/19)

ACS National Chemistry Exams, https://www.acs.org/content/acs/en/education/students/highschool/olympia... (accessed 4/29/19)

American Association for the Advancement of Science, Project 2061, Science Assessments http://assessment.aaas.org/topics/1 (accessed 4/29/19)

Component 1 Online Tutorial, Pearson VUE, https://home.pearsonvue.com/nbpts (accessed 4/29/19)

National Board Science Standards, http://www.nbpts.org/wp-content/uploads/EAYA-SCIENCE.pdf,  (accessed 4/29/19)

National Board for Professional Teaching Standards, Assessment Center Policy and Guidelines, https://www.nbpts.org/national-board-certification/candidate-center/asse... (accessed 4/29/19)

This past school year, I had the opportunity to participate in the AACT Science Coaches program. When I applied for the program, I expected to be partnered with a professor, probably someone who had been in academia for quite awhile. I thought that this person could share their research with my students and maybe help me with some content questions. I was excited for the opportunity but I never thought my science coach would be interested in developing and executing lessons with me. Luckily for me, my experience ended up being nothing like what I expected.

I was paired with a PhD student from my alma mater who is part of lab in the photochemical sciences department. I soon found out that Travis, my science coach, was considering teaching high school science and he helped develop labs for the undergraduate chemistry courses at his university. Travis’ lab specifically worked with FLIR IR cameras that attach to smartphones. 

The first time we met, Travis brought his IR cameras and some props to show me what they could do. I knew that these tools would fit perfectly with the insulator challenge I give my freshmen in our thermal energy unit. In the past, students were challenged to build an insulator to keep a beaker of hot water warm. Students loved the activity and came up with very creative solutions but it was not very data driven. Travis and the IR cameras completely changed that. 

The insulator project started with Travis coming into my classroom for a day and teaching my freshmen about infrared radiation. This was perfect because waves are in the state standards for this class. Travis showed students how IR waves can be transmitted, blocked and reflected and even brought his invisibility cloak (space blanket) with him! In the photo below, you can see we were able to cast the screen from FLIR app to the CleverTouch board so the class could see the student behind the space blanket has become “invisible” and the student behind the trash bag is not (see figure 1). 

Figure 1: The Invisibility Blanket

After students were given an introduction to waves and IR cameras, they got to try them out themselves! We gave each team a beaker of hot water and access to all of the available insulator building materials. The students’ job for the rest of the class period was to collect data on how well each material blocked, transmitted or reflected infrared radiation using the IR cameras. These data would then drive their insulator building the next day. In the picture below, you can see the outline of a piece of material a student is holding up to their beaker of hot water. The material transmits infrared radiation. You can also see the reflection of the beaker on the black lab bench (see figure 2).

Figure 2: Observing and analyzing efficiency of insulating materials using an IR camera

Travis came back the next day and helped students build their insulators and evaluate their insulator effectiveness with the IR cameras. Students built their insulators, recorded the initial temperature of their water and took a starting picture with their IR cameras. Students took a few more pictures in between and then a final picture at the end with their final temperature reading. From the IR camera pictures, students were able to evaluate where heat was escaping from their insulators and reflect on what they could do better next time. In the pictures below, you can see this insulator was losing heat through the top (see figure 3 & 4). 

Figure 3 & 4: Testing student made insulators using IR camera

Thanks to this partnership with my science coach, my freshmen scientists were able to use technology to solve real world problems that they otherwise would not have had access to. I am very grateful for the partnership AACT provided me with my science coach and I encourage you to apply to the program!

You can learn more about the program and apply here. Applications are due May 9th! 
 

What: 224^th 2YC₃ Conference (2YC₃ = Two-Year College Chemistry Consortium)

When: August 23-24, 2019

Where:San Diego Miramar College

Faculty and exhibitors click here to learn more about conference registration, how and when to submit an abstract, travel and lodging info, campus and contact info, and sponsors and exhibitors. Registration for high school teachers is free.

Conference Points-Of-Contact:

Program Chair- Gary Smith (619.388.7888), glsmith@sdccd.edu

Local Arrangements Chair- Rebecca Bowers-Gentry (619.388.7241), rbowersg@sdccd.edu

Exhibits Chair- Cynthia Gilley (619.388.7938), cgilley@sdccd.edu

San Diego Miramar College is excited to host the 224^th 2YC₃ Conference. Do you have a unique way that you partner with your students, other faculty, universities, businesses, surrounding community, etc. to achieve student success? Are you using innovative approaches inside and/or outside of the classroom? We want you to come and share about what you are doing! Our hope is that these two days will be a celebration of the good work that is happening across a variety of two-year schools and highlight the amazing work happening in Chemistry Education. Through these connections, we also anticipate new partnerships being formed and innovative techniques being adopted into classrooms. Come celebrate, innovate, and collaborate!

Bill Hammack- never heard of him, right? I love his videos as he dissects the physics and chemistry of how things work. Nothing fancy or gimmicky. Just good ol' experimentation, acute observation, rational deduction, and contagious curiosity.

He does one of his best jobs (my opinion) with Michael Faraday's The Chemical History of a Candle. Can't get much better binge-watching than the videos listed below- poetic language, simple and elegant demos, and a common phenomenon, almost always ignored, yet relevatory in its own right about science, the knowable underpinnings of the physical world, and the critical interplay among insightful observations, proper experimentation, and logical deduction. Get a bowl (or two) of popcorn, your favorite beverage(s), and sit back and enjoy. 

And as a bonus you can watch the lectures with Commentary and download for free teaching and lecture guides and student activities (in pdf format).

The chelation reaction of nickel ions with the organic bidentate ligand dimethylglyoxime (DMG)¹ in an alkaline ammonia medium producing nickel dimethylglyoxime, Ni(DMG)₂, a red cherry or raspberry colour precipitate has been known since 1905 when it was discovered by Russian chemist Lev Aleksandrovich Chugaev (see figure 1). It was the first organic spot test reagent used to detect a metal ion and as a result DMG is known as Chugaev’s reagent.² 

The balanced ionic equation for this reaction:   

Ni²⁺_(aq) + 2C₄H₈N₂O_{2 (aq)}→ Ni(C₄H₇N₂O₂)_{2 (s)} + 2H⁺_(aq)

Figure 1: Structural equation from The Gravimetric determination of Nickel, Truman State University CHEM 222 Lab Manual³

This reaction is still very much in use today for the detection of nickel metal ions due to its striking colour formation. Both qualitative and gravimetric determinations of nickel are part of many chemistry courses. The reaction involves two dimethylglyoxime molecules acting as chelating agents to form the nickel dymethylglyoxime square planar complex. This reaction is very sensitive and can be used as a confirmation test for the presence of nickel II cations even in very low concentrations.

The same procedure can be easily applied to metal objects that regularly come in contact with the skin, for example coins, jewelry, earrings, spectacle frames, watch straps, etc. for the benefit of people that suffer from a kind of skin sensitivity or dermatitis called Nickel itch.

This contact allergy or allergic contact dermatitis (ACD) usually flares up when sweating. A red itchy rash develops on the skin that has been in contact with the metal. It is believed that the acids present in sweat dissolve a little of the nickel and it is the release of nickel ions that are responsible for causing nickel sensitization and ACD⁴ that can accentuate conditions such as skin erythema, eczema, etc. Only a certain amount of released ions will cause a reaction. For example, alloys such as many stainless steels contain nickel but do not release sufficient amounts of nickel ions to cause someone to become nickel sensitized or have nickel ACD reactions if they are already sensitive to nickel. In contrast, nickel plated jewellery will release vast amounts of nickel ions in contact with sweat from the skin and from everyday brushing, friction, abrasion, etc. especially when worn for extended periods of time.

It is not known why people develop allergies to nickel and there is no cure. The best course of action to prevent an allergic reaction is to avoid contact with products containing nickel and in this post we will to show how to make a cheap and quick nickel detection device at home or in the lab based on the reaction described above.

A video describing how to test for the presence of nickel in various coins using such a device can be watched below (no sound).⁵

The video shows a few drops of DMG, C₄H₆(NOH)₂, being added to a dilute solution of nickel II sulfate with a few drops of ammonia solution. Immediately, an insoluble bright red solid called nickel dimethylglyoxime, Ni(C₄H₈N₂O₂)₂, precipitates out of solution. Shortly after that, the cotton bud or Q-tip containing DMG and ammonia can be seen being rubbed against the surface of a coin. If nickel is present in the coin then the Q-tip turns red.

Even though commercial products exist to test metals for the presence of nickel⁶ a much simpler and cheaper version can be made at home or in the lab with readily available household ingredients.⁷ First, obtain some cotton buds or Q-tips and dip them in a solution of 1% dimethylglyoxime (DMG) in ethanol (vodka will work just as well) for 10 minutes. NOTE: DMG is a flammable irritant and can be difficult to obtain but a very small amount (1 g approx.) is needed to make a large stock of prepared buds. Once the buds have been soaking for at least 10 minutes, remove them and leave them to air dry. Once dry, they are ready to be used or can be stored in an air tight container labelled appropriately.

To test for the presence of nickel in the desired metal object add a few drops of dilute ammonia solution (household ammonia will work depending on concentration, higher concentrations produce faster results) to just wet the tip of the cotton. Clean the article with a moist tissue first and rub the tip on the coin or object for about a minute and observe if any pink-red colour appears. The intensity of the colour will depend on how much nickel is present or if it is freely available on the surface of the object (dark pink-red if made completely out of nickel or nickel plated) or light pink if alloyed with other metals. Interestingly, even when bound tightly in an alloy, the test will detect at least some of the nickel cations present. Coins made out of copper or zinc will show no red colour being formed but iron and steel coins/objects might produce a false positive as Fe²⁺ and Fe³⁺ ions interferes with the detection of Ni²⁺ using DMG because it forms a red-brown coloured iron hydroxide complex in alkaline conditions. To avoid this situation, a few drops of citric acid (lemon juice) can be added to convert the iron complex to a water-soluble colourless complex.⁸

For an excellent infographic on the composition of UK coins and to use as a comparison please see Compound Interest’s The Metals in UK Coins.⁹ Andy Brunning also created a similar poster for C&EN Periodic graphics: the compositions of U.S. coins.¹⁰

Since the majority of nickel on Earth is present in the molten iron core of the planet, the percentage mined each year comes mainly from outer space as iron/nickel meteorites from millions of years ago. Metallic meteorites have a nickel content ranging from 5 to 35% so it is possible to differentiate meteorites from other rocks and manmade iron samples also using this simple reaction.⁸

For an in depth analysis a control could be obtained in the form of a coin that is known to have no nickel metal at all. Secondly, a standard nickel II sulfate solution could be prepared to compare the coloured test samples visually followed by colorimetry analysis to determine the concentration of nickel in each sample.

To conclude the procedure shows an easy, convenient and cheap way for people suffering from skin irritation to limit and/or eliminate the risks of exposure to sources of nickel metal using some interesting classic chemistry.

EXTENSION

crystal_of_ni_compound.png

Figure 2: Needle-shaped crystals of Ni(DMG)₂ under 40x magnification

A drop of water containing Ni(DMG)₂ precipitate was placed on a microscope slide and examined under the microscope (see figure 2). Red needle-like crystals of the complex were observed. In order to grow larger crystals the precipitate was dissolved in hot dilute hydrochloric acid and left to evaporate slowly. Long brown needle-shaped crystals appeared after a day. When the crystals were crushed using a glass rod the familiar characteristic red cherry colour was observed (see figure 3).

crushed_ni_compound.png

Figure 3: Crushed crystals exhibiting the characteristic brilliant red colour of Ni(DMG)₂

Aknowledgements: I would like to thank Deanna Cullen and Tom Kuntzleman for reading a previous draft version of this post providing advice, suggestions and writing constructive comments to improve it. Their experience and support is invaluable to someone like me who does not post or write scientific articles regularly.

References

1. Dimethylglyoxime (DMG) Safety Data Sheet, created by Global Safety Management Ink. (accessed 5/5/19)
2. Kauffman, G.B., Platinum Metal Rev., 1973, 17, (4).
3. The Gravimetric determination of Nickel, Truman State University CHEM 222 Lab Manual (accessed 5/5/19)
4. Quick and easy detection of nickel metal ions in coins, andycapo123 YouTube Channel, Published 4/25/19 (accessed 5/5/19)
5. Fact Sheet 1: Nickel Allergic contact dermatitis, The Nickel Institute. June 2016. (accessed 5/6/19)
6. The kit can be bought on Amazon: https://www.amazon.co.uk/gp/product/B00EWUS86C/ref=ox_sc_act_title_6?smi... or as MQuant Nickel test strips sold by Merck
7. DMG can be purchased from chemical suppliers but the author bought 10 g of DMG 99% from Ebay costing £6.50 (approx. $8.50). Enough to make hundreds of testing cotton buds.
8. Zamora, L.L., Zamora, S.L., Romero, M., Identifying extraterrestrial materials, Education in Chemistry magazine, March 9, 2015.
9. The Metals in UK Coins, Andy Brunning, Compound Interest, March 27, 2014. (accessed 5/6/19)
10. Periodic graphics: the compositions of U.S. coins, Andy Brunning, Chemical and Engineering News, Volume 94 Issue 28, July 11, 2016. (accessed 5/6/19)

For Further Information:

Brandl, Herbert, Trickkiste Chemie, Bayerischer Schulbuch Verlag, München, 1998.

Emsley, John, Nature’s Building Blocks An A-Z guide to the elements, Oxford University Press, 2003.

Whiteboards are great learning tools in a science classroom. Not only do students love to write on them, but they also allow for quick formative assessments, and they make collaboration convenient.

Additionally, whiteboarding may support the implementation of the Next Generation Science Standards (NGSS), particularly when it comes to using models. Scientific Modelling, an integral component of the NGSS, includes the use of diagrams, physical replicas, mathematical representations, analogies, and computer simulations to represent complex systems. By their nature, models are tentative because as students gather more knowledge, they can be refined. Whiteboards are an excellent resource for developing scientific models since students can easily draw diagrams, analyze data, and rearrange equations as they explore scientific phenomena.^1,2

Unfortunately, whiteboards can be expensive. I have seen costs of $10 - $20 for a single whiteboard. At this price, a class set could cost a couple of hundred of dollars.

However, with these instructions, you can make eight 24-in x 24-in whiteboards for less than $2.00 each! As a bonus, I have included instructions for simple whiteboard stands, which will cost an additional $1.86 for each stand.

The Whiteboards

Step 1 - Purchase a 4-ft x 8-ft sheet of Smooth White Hardboard

Figure 1: Sheets of smooth white hardboard

The whiteboards are cut from a 4-ft x 8-ft sheet of Smooth White Hardboard (figure 1). You can find this material in your local home improvement store. It should be located in the lumber area of the store. I purchased a sheet for $14.48 which is enough to make eight 24-in x 24-in whiteboards.

Step 2 - Cut the sheet of hardboard to size 

Figure 2: Cutting area

A 2-ft x 2-ft whiteboard is a nice size for group work. Plus, the material is pretty heavy, and I’ve found that any larger with this material is pretty cumbersome.

The major hardware stores like Lowe’s and Home Depot will cut the sheet for free. Just ring the bell on the side of the saw area (figure 2), and someone will assist you in short time.

Step 3 - Sand the edges

Figure 3: Sanding the edges

After the board is cut, the edges are pretty rough. It only took me about 10 minutes to smooth them out with some fine grit sandpaper (figure 3).

The Base (Bonus!)

Step 1 - Buy and cut a 2 x 8 x 16 pine board

Figure 4: Pine lumber

Next, I purchased a 2-in x 8-in x 16-ft board for the bases (figure 4). Once again, you can get it cut to size at the store. I had it cut into eight 2-ft sections.

Step 2 - Cut a slot down the middle

Figure 5: Adjusting the depth

You will need to take care of cutting the slot on your own. I set the cutting depth on my circular saw to about an inch (figure 5) and cut right through the middle (figure 6). The whiteboard didn’t quite fit in the slot, so I had to run through the middle a second time to widen it up.

Figure 6: The slot down the middle needs to be wide enough for whiteboard to fit.

Step 3 - Sand the edges

As with the whiteboards, the edges will need sanding (figure 7). These pieces took a lot longer, so you may want to enlist some students to help.

Figure 7: Sanding the board

Finally, you can assemble them by placing one whiteboard in each stand (figure 8).

Figure 8: Whiteboard and stand

I hope your new class set of whiteboards supports learning and collaboration in your classroom. I would love some tips on whiteboarding in the science classroom, so leave a comment and let me know how you use them in your courses.

Acknowledgments

DIY whiteboard construction isn't new, and teachers have been sharing instructions for some time. I was introduced to the idea by Lynnelle Buchanan, who presented at the Michigan Science Teachers Association Conference 2019 (Scientific Modelling).

References

1. Hestenes, D. (2013). Remodeling Science Education. European Journal of Science and Mathematics Education, 1(1), 13-22.

2. NGSS Lead States. 2013. Next Generation Science Standards: For States, By States. Washington, DC: The National Academies Press.

Take a flight. No, I’m not asking you to step on a plane. Take a page out of a wine and beer tasting approach as you look at the May 2019 issue of the Journal of Chemical Education.

Taste testing a flight of drinks—several selections, in smaller amounts—gives you a chance to sample a greater variety and compare the collection. The idea has even been extended to Dairy Queen treats this summer. Why choose when you can just have smaller amounts of several and decide what you think about what each offers?

The May issue contains a “flight” of articles (available to JCE subscribers*) for creating a chemistry-themed escape room in your classroom, showing you how three different groups of chemistry educators used the idea. If you haven’t heard of escape rooms before, Watermeier and Salzameda explain in Escaping Boredom in First Semester General Chemistry:

"In a typical escape room game, groups are first briefed with a storyline related to a series of puzzles they must solve. After the narrative is presented, the doors to a theme-decorated room are closed, “trapping” the students in the room. The group of students must then work together to solve several puzzles to escape the room within an allotted time. By using clues and problem-solving skills, players determine the solutions to one set of problems, and are then led to another set of riddles."

Article Flight

1. Escaping Boredom in First Semester General Chemistry
2. A Lab-Based Chemical Escape room: Educational, Mobile, and Fun!
3. Escape the Lab: An Interactive Escape Room Game as a Laboratory Experiment

My thoughts are below, but please, try the flight and see which might fit your taste!

Flight Notes

1. Escaping Boredom in First Semester General Chemistry

• Reviews topics to prep for final exam: density, unit conversions, significant figures, lab equipment, electronic configurations, periodic table, nomenclature, hybridization, balancing equations, thermodynamics.
• For general chemistry in college, but topics could work for high school.
• Authors worked with professional game designer from Escape Room Era.
• Linear path through seven stations, plus adjacent room—how to work out finishing? Authors have tips.
• Adjust story to fit high school? Has a “graduate advisor” as character.

Video 1: Escape room Video_english from Department of Science Teaching on Vimeo. (accessed 5/12/19)

2. A Lab-Based Chemical Escape room: Educational, Mobile, and Fun!

• Authors have fun introduction video (see video 1). 
• Topics are linked to 11^th/12^th grade chemistry curriculum.
• Authors created a kit that teachers can borrow, to then set up escape room at their own school.
• Non-linear path to solving mystery, so can accommodate more students simultaneously.
• Online supplement shows escape room photo for when students exit, just like commercial ones.

3. Escape the Lab: An Interactive Escape Room Game as a Laboratory Experiment

• Uses sequence of analytical instruments, so for higher level than high school.
• Could use some of the ideas: groups can ask for hints, but with a time penalty after a certain point.
• Good suggestions for items to use:
• “numeric-combination lock boxes, commonly used in real estate”
• “soda-can diversion safe” — looks like a soda can, but can be opened to reveal a clue
• 100-piece puzzle, with “clue … added to the back of the assembled puzzle”

General Thoughts

• Every article includes the use of personal protective equipment as part of it. Safety must be part of the experience.
• How are the puzzles reset, particularly if the room presents a non-linear path and there is a lot of student activity going on?
• An escape room could be an activity to connect a high school chemistry club with a college-level student chapter.
• If the goal is efficient, straightforward review, this is more elaborate. It can have other benefits though—promotion of teamwork among student groups and perseverance if an answer cannot be figured out quickly.

Have you tried an escape room in your classroom? Share! Start by submitting a contribution form, explaining you would like to contribute to the Especially JCE column. Then, put your thoughts together in a blog post. Questions? Contact us using the ChemEd X contact form.

*See Accessing Cited Articles

Encouraging Student Learning and Success

The May 2019 issue of the Journal of Chemical Education is now available online to subscribers. Topics featured in this issue include: microscale precipitation chemistry; making science personal; chemical escape rooms; teaching organic chemistry; peer learning; laboratory assessment; examining cognitive load; inquiry activities; exploring infrared spectroscopy; laboratory experiments; teaching resources; shaking the archives: the blue bottle experiment.

Cover: Microscale Precipitation Chemistry

Microscale and green chemistry methods have a major impact on the general chemistry laboratory experience. Precipitation reactions, once investigated in test tubes, can be performed with as little as two crystals and a 10-drop puddle of water, as described by Bob Worley, Eric M. Villa, Jess M. Gunn, and Bruce Mattson in Visualizing Dissolution, Ion Mobility, and Precipitation through a Low-Cost, Rapid-Reaction Activity Introducing Microscale Precipitation Chemistry. The photo sequence on the cover shows crystals of silver nitrate and potassium iodide, both carried by moistened toothpicks, and brought to the puddle where they can be seen to shrink in size as they dissolve. The ions migrate across the puddle and within 15 s a precipitate of silver iodide starts to form at the interface of the two local solutions. The precipitate continues to develop along the interface. (Photo credit: Peter Stone, Department of Chemistry, Creighton University.)

On ChemEd X: Chad Husting has previously commented on this “puddle chemistry” experiment in his blog post: Misconceptions and Struggles with Double Displacement reactions and dissolving... 

Making Science Personal

To encourage the persistence of underrepresented populations in STEM begins in gateway science courses like general chemistry, Stephanie N. Knezz shares her thoughts on Drawing a New Scientist: Why I Come Out to My Chemistry Class.

To show the role of science in our daily lives, Manuel F. Molina and José G. Carriazo explore Awakening Interest in Science and Improving Attitudes toward Chemistry by Hosting an ACS Chemistry FeSTiVAl in Bogotá, Colombia.

Chemical Escape Rooms

The popular genre of “escape rooms” is brought into the chemistry classroom in three articles in this issue, as discussed by Erica Jacobsen in Especially JCE: May 2019:

A Lab-Based Chemical Escape Room: Educational, Mobile, and Fun! ~ Ran Peleg, Malka Yayon, Dvora Katchevich, Mor Moria-Shipony, and Ron Blonder

Escape the Lab: An Interactive Escape-Room Game as a Laboratory Experiment ~ Matthew J. Vergne, Joshua D. Simmons, and Ryan S. Bowen

Escaping Boredom in First Semester General Chemistry ~ David Watermeier and Bridget Salzameda

Teaching Organic Chemistry

Improving College Student Success in Organic Chemistry: Impact of an Online Preparatory Course ~ Christian Fischer, Ninger Zhou, Fernando Rodriguez, Mark Warschauer, and Susan King

Assessment of Student Performance on Core Concepts in Organic Chemistry ~ Naha J. Farhat, Courtney Stanford, and Suzanne M. Ruder

Teaching an Undergraduate Organic Chemistry Laboratory Course with a Tailored Problem-Based Learning Approach ~ Luca Costantino and Daniela Barlocco

Peer Learning 

Impact of Peer-Led Team Learning and the Science Writing and Workshop Template on the   Critical Thinking Skills of First-Year Chemistry Students ~ Norda S. Stephenson, Imron R. Miller, and Novelette P. Sadler-McKnight

Exploring Peer Instruction: Should Cohort Clicker Responses Appear During or After Polling? ~ Russell J. Pearson

Writing as a Mode of Learning: Staged Approaches to Chromatography and Writing in the Undergraduate Organic Lab ~ Jennifer Clary-Lemon, Rachelle Gervacio, and Devin Latimer

Laboratory Assessment

Survey of Undergraduate Students’ Goals and Achievement Strategies for Laboratory Coursework ~ Stephanie Santos-Díaz, Sarah Hensiek, Taylor Owings, and Marcy H. Towns

Exit Interviews: Laboratory Assessment Incorporating Written and Oral Communication ~ Garland L. Crawford and Kathryn D. Kloepper

Examining Cognitive Load

Looking into the Black Box: Using Gaze and Pupillometric Data to Probe How Cognitive Load Changes with Mental Tasks ~ Jessica M. Karch, Josibel C. García Valles, and Hannah Sevian

Inquiry Activities

Teaching Polymer Theory through the Living Polymerization and Characterization of Poly(methyl methacrylate) and Poly(butyl methacrylate) Homo- and Copolymers ~ W. J. Koshut, A. M. Arnold, Z. C. Smith, Z. M. Wright, and S. A. Sydlik

Collaborative Learning Exercises for Teaching Protein Mass Spectrometry ~ Michelle L. Kovarik and Jill K. Robinson

Introducing NMR Spectroscopy Using Guided Inquiry and Partial Structure Templating ~ Erin M. Kolonko and Kristopher J. Kolonko

Computer-Aided Drug Design for Undergraduates ~ Dean J. Tantillo, Justin B. Siegel, Carla M. Saunders, Teresa A. Palazzo, Phillip P. Painter, Terrence E. O’Brien, Nicole N. Nuñez, Dustin H. Nouri, Michael W. Lodewyk, Brandi M. Hudson, Stephanie R. Hare, and Rebecca L. Davis

A Tale of Two Molecules: How the Heat Capacities of N₂(g) and F₂(g) Differ At High Temperature and Why Naïve Expectations Fail to Explain These Differences: A Spreadsheet Exercise for Physical Chemistry Students ~ Arthur M. Halpern and Robert J. Noll

Buffer Squares: A Graphical Approach for the Determination of Buffer pH Using Logarithmic Concentration Diagrams ~ Spiros A. Pergantis, Iakovos Saridakis, Alexandros Lyratzakis, Leonidas Mavroudakis, and Tamsyn Montagnon

Evaluation of Mulliken Electronegativity on CH₃NH₃PbI₃ Hybrid Perovskite as a Thought-Provoking Activity ~ Asiel N. Corpus-Mendoza, Paola M. Moreno-Romero, and Hailin Hu

Exploring Infrared Spectroscopy 

Inquiry-Based IR-Spectroscopy Activity Using iSpartan or Spartan for Introductory-Organic-Chemistry Students ~ Amy M. Balija and Layne A. Morsch

Developing Students’ Scientific Reasoning Abilities with an Inquiry-Based Learning Methodology: Applying FTIR Spectroscopy to the Study of Thermodynamic Equilibria in Hydrogen-Bonded Species ~ P. G. Rodríguez Ortega, R. Casas Jaraíces, Marta Romero-Ariza, and M. Montejo

Supporting the Teaching of Infrared Spectroscopy Concepts Using a Physical Model ~ Lyniesha C. Wright and Maria T. Oliver-Hoyo

Laboratory Experiments

Isolation and Derivatization of Sucralose from an Artificial Sweetener to Provide a Hands-On Laboratory Experiment Emphasizing Synthesis and Purification ~ Paige J. Monsen and Frederick A. Luzzio

Aqueous Dearomatization/Diels–Alder Cascade to a Grandifloracin Precursor ~ Emily A. Shimizu, Brett Cory, Johnson Hoang, Giovanni G. Castro, Michael E. Jung, and David A. Vosburg

Functionalization of Gold Nanoparticles for a Color-Based Detection of Adenosine in a Bioassay ~ Yoann Roupioz

Inorganic Phosphors for Teaching a Holistic Approach to Functional Materials Investigation: From Synthesis and Characterization to Applications of Thermo- and Mechanoluminescence ~ Paul C. Stanish, Howard Siu, and Pavle V. Radovanovic

Enhancing the Teaching of Corrosion to Chemical-Engineering Students through Laboratory Experiments ~ Javier Llanos, Ángel Pérez, and Antonio de Lucas-Consuegra

Improved Procedure for Bleach-Based Alcohol Oxidation in Undergraduate Laboratories ~ Edon Vitaku and Hamish S. Christie

Teaching Resources

Development and Production of Interactive Videos for Teaching Chemical Techniques during Laboratory Sessions ~ Sarah L. Cresswell, Wendy A. Loughlin, Mark J. Coster, and David M. Green

Using Control Charts Early in the Quantitative Analysis Laboratory Curriculum ~ Dane Scott and Daniel Firth

Overdriven Pulsed Light Emitting Diodes: An Inexpensive Excitation Source for Time-Resolved Luminescence Lifetime Measurements ~ Steven M. Drew, Deborah S. Gross, William E. Hollingsworth, Thomas Baraniak, Christopher M. Zall, and Kent R. Mann

Addition to “News from the Periodic Table: An Introduction to ‘Periodicity Symbols, Tables, and Models for Higher-Order Valency and Donor–Acceptor Kinships’” ~ Frank Weinhold

Shaking the Archives: The Blue Bottle Experiment

This issue includes a demonstration by Nicolas Dietrich, Kritchart Wongwailikhit, Mei Mei, Feishi Xu, Francisco Felis, Abderrahmane Kherbeche, Gilles Hébrard, and Karine Loubière that involves Using the “Red Bottle” Experiment for the Visualization and the Fast Characterization of Gas–Liquid Mass Transfer. It is a twist on the popular “blue bottle” experiment,  in which a solution containing glucose, NaOH, and methylene blue turns blue when shaken and becomes colorless while standing (a video of this can be seen as part of Michael Morgan’s ChemEd X post Kinetics Review). This demonstration was popularized by J. Arthur Campbell in 1963 as a way to introduce concepts of kinetics, mechanisms, catalysis, and steady-state conditions (Kinetics—Early and Often). Over the years, discussions of and variations on this demonstration have appeared on the cover:

bluebottlecovers.jpg

and in the pages of JCE:

The Blue Bottle Experiment Revisited: How Blue? How Sweet? ~ A. Gilbert Cook, Randi M. Tolliver, and Janelle E. Williams

The Blue Bottle Revisited ~ Walter R. Vandaveer IV and Mel Mosher

The Blue Bottle Reaction as a General Chemistry Experiment on Reaction Mechanisms ~ Steven C. Engerer and A. Gilbert Cook

Kinetics of Methylene Blue Reduction by Ascorbic Acid ~ Sarah Mowry and Paul J. Ogren

Greening the Blue Bottle ~ Whitney E. Wellman, Mark E. Noble, and Tom Healy

Out of the Blue (JCE Classroom Activity on the Blue Bottle) ~ Mark E. Noble

Variations on the “Blue-Bottle” Demonstration Using Food Items That Contain FD&C Blue #1 ~ Felicia A. Staiger, Joshua P. Peterson, and Dean J. Campbell

Blue Bottle Experiment: Learning Chemistry without Knowing the Chemicals ~ Taweetham Limpanuparb, Cherprang Areekul, Punchalee Montriwat, and Urawadee Rajchakit (See Erica Jacobsen's Especially JCE: June 2017 for a discussion of this article.)

Greening the Traffic Light: Air Oxidation of Vitamin C Catalyzed by Indicators ~ Urawadee Rajchakit and Taweetham Limpanuparb  

Rapid Blue Bottle Experiment: Autoxidation of Benzoin Catalyzed by Redox Indicators ~ Urawadee Rajchakit and Taweetham Limpanuparb 

Direct Visualization of Scale-Up Effects on the Mass Transfer Coefficient through the “Blue Bottle” Reaction ~ Patrick M. Piccione, Adamu Abubakar Rasheed, Andrew Quarmby, and Davide Dionisi

What Is Happening When the Blue Bottle Bleaches: An Investigation of the Methylene Blue-Catalyzed Air Oxidation of Glucose ~ Laurens Anderson, Stacy M. Wittkopp, Christopher J. Painter, Jessica J. Liegel, Rodney Schreiner, Jerry A. Bell, and Bassam Z. Shakhashiri

JCE: Encouraging Chemical Education 

With volumes of issues to explore, you will always find content that will shake or stir you—including the articles mentioned above, and many more, in the Journal of Chemical Education. Articles that are edited and published online ahead of print (ASAP—As Soon As Publishable) are also available.

Summer is almost here! Please consider submitting a contribution to the Journal of Chemical Education. Erica Jacobsen’s Commentary, Become a Journal of Chemical Education Author, gives great advice on writing for the Journal. In addition, numerous author resources are available on JCE’s ACS Web site, including: Information for Authors and Author Guidelines.

Time for a new chemical mystery! Watch the video below and see if you can use your chemical knowledge to figure out how this experiment is done.

My guess is that this trick will be easy for the chemistry teachers to figure out. However, I'll bet this experiment will stump most of your students! Let me know in the comments how you think I carried out this trick. I'll post the solution in a few days.

"In honor of the International Year of the Periodic Table this series of articles details the Element of the Month project developed by Stephen W. Wright (SWW), Associate Research Fellow at Pfizer Inc., and Marsha R. Folger (MRF), chemistry teacher (now retired) at Lyme – Old Lyme High School in Connecticut. Read The Element of the Month - An Introduction for an overview of the project and links to the other articles in the series." - Editor

The fourth element highlighted in our Element of the Month program is sulfur. For us, this meeting would occur in December. Sulfur plays an essential role in everyday life but it is likely that the students will have little familiarity with sulfur and its compounds. The inclusion of sulfur in the Element of the Month program allows them to make connections between sulfur and its many roles. The December class schedule is of course compressed due to the holidays, and the sulfur demonstrations are designed to be relatively simple to arrange.

Figure 1: Sample of elemental sulfur

Occurrence in Nature

Students will probably be unaware that a vast amount of sulfur occurs in the form of sulfate ion in seawater. Sulfur also occurs in numerous sulfide and sulfate minerals, some of which are important ores. Sulfur can be found as the free element in certain situations, and some students may know that sulfur is frequently associated with volcanoes and hot springs. We have large samples, of 100 to 300 g mass, of pyrite (“fool’s gold”, FeS₂), galena (PbS), gypsum (CaSO₄), and elemental sulfur (see figure 1). These are contained in clear plastic jars and passed around the class for inspection. We note that sulfur is also found in coal and petroleum. Lastly, we explain that sulfur occurs in the amino acid cysteine, which plays a key role in maintaining the three dimensional structure of proteins, especially hair, horn, and claws.

Uses

The largest use of sulfur is in the manufacture of sulfuric acid, which students will realize is “battery acid”. They will respond that they know that sulfuric acid is “strong”, but they will not know that sulfuric acid is and always has been the largest production volume industrial chemical. Sulfur and its compounds are used in vulcanizing rubber and in the manufacture of a great many chemicals. Many students will know that sulfur is a component of the old fashioned explosive black powder, and in matches and pyrotechnics. Most detergents are compounds of sulfur. On the lecture table, we display various products that contain sulfur, including a small tire such as a bicycle tire, a battery from a lawn tractor or other small vehicle, detergent, Plaster of Paris, a scrap of gypsum wallboard, Epsom salt, and match box.

Physical Properties

We take a few minutes to note that sulfur is bright yellow, odorless, insoluble in water, brittle, and does not conduct electricity. It melts at 115 °C, just above the boiling point of water.

Figure 2: Reaction of zinc and sulfur. A) Mixing zinc and sulfur, B & C) Two views of heated rod and zinc/sulfur mixture on heat resistant mat, D) Ignition of mixture, E & F) After ignition. Derived from Jerrold J. Jacobsen and John W. Moore. Chemistry Comes Alive: Vol. 3: Abstract of Special Issue 23 on CD-ROM, Journal of Chemical Education 1999 76 (9), 1311. DOI: 10.1021/ed076p1311.

Chemical Properties

We first explain that sulfur chemistry is noted for the various oxidation states that sulfur can take. On the board, we show the formulas and oxidation states of sulfur in sulfur (S, 0), sulfide (S^2-, -2), sulfite (SO₃^2-, +4), and sulfate (SO₄^2-, +6). We observe that sulfur can combine directly with some metals such as iron and zinc to form sulfides. We demonstrate the very exothermic reaction between zinc and sulfur to form zinc sulfide by mixing 4 grams of gray powdered zinc metal and two grams of yellow powdered sulfur.¹ We place the mixture on a heat resistant mat in the fume hood and ignite the mixture using a gasburner or heated rod (figure 2). After the reaction has cooled, we remove the mat and show the class the white product. We note that many of the transition metals form extremely insoluble sulfides and are often mined as their sulfide ores.

Figure 3: Precipitation of the sulfides of Cd, Pb, Mn and Zn in sodium sulfide solution

We show the precipitation of the sulfides of cadmium, lead, manganese, and zinc by placing aqueous solutions of these metals in large test tubes in a test tube rack and treating the solutions with a little dilute aqueous sodium sulfide solution (see figure 3).² Colorful sulfide minerals such as cinnabar (HgS, red), orpiment (yellow, As₂S₃), and stibnite (black, Sb₂S₃) were used as pigments in ancient times. We explain that sulfur also forms a sulfide compound with hydrogen, and ask the class if they know what that substance is. We explain that hydrogen sulfide is a colorless, flammable, poisonous gas that has a very familiar, rotten egg odor. As an aside, we note that burning rubber stinks because of organic sulfur compounds used to formulate the rubber. Some students will know that hair perm solutions smell, and we explain that this is also from sulfur compounds that are present. As a general rule, sulfides smell, while oxidized sulfur compounds generally are much less odorous.

Figure 4: A) Sulfur powder in spoon before reaction, B) Blue flame of burning sulfur in darkened room, C) Sulfur dioxide fog after addition of water and shaking of the flask, D) After addition of water and universal indicator.

Sulfur forms compounds with oxygen too. For example, it burns in air to form sulfur dioxide. Sulfur dioxide in the environment comes from volcanoes, from burning coal or oil that contains sulfur, and from “roasting” metal sulfide ores. Sulfur dioxide is a colorless, toxic, dense gas, one that does not burn or support combustion. It has a choking, familiar smell that many associate with the smell of burning matches. We burn a bit of sulfur using a long handled deflagrating spoon in a 1 L flask in the darkened classroom, and we note that the sulfur burns with a clear blue flame (see figure 4). After a short while, we extinguish the sulfur and add a small amount of water, about 50 mL, to the flask. We stopper the flask and shake the flask, then gently release the stopper. An audible sound of air rushing into the flask demonstrates that sulfur dioxide is extremely water soluble.³ We add some universal pH indicator solution to the flask and show that the sulfur dioxide solution gives an acidic reaction with a pH indicator. Students will usually have heard of acid rain and this is an opportunity to make that connection. We will usually add some indicator to a large test tube of water as a control, and to a test tube of a dilute acid as well. If a bell jar or similar large container is available, one can show how sulfur dioxide may be used as a bleach. A red or violet carnation is placed under a bell jar with some burning sulfur in the fume hood (see figure 5).⁴ By the end of the class period, the carnation will have lost most of its color. We explain that the acidic solution formed from sulfur dioxide in water can be neutralized with a base, and the resulting salts are known as sulfites. These compounds are reducing agents and are frequently used as preservatives. For example, produce and wines may be preserved with sulfites. As a demonstration, we show the class two petri dishes, each containing a slice of very ripe apple or pear. One of the slices is untreated and brown, while the second half has been treated with a few drops of a sodium bisulfite solution and appears fresh. We will usually note that sulfites are used to manufacture cheap paper, but that paper made with sulfites will gradually deteriorate with age due to the acidic nature of sulfites and sulfur dioxide. Lastly we show the reduction of permanganate ion by sodium bisulfite solution by pouring some dilute potassium permanganate into a sodium bisulfite solution.⁵ 

Figure 5: A) A tired carnation, bell jar and dish with powdered sulfur,  B) Carnation and dish together under bell jar ready for ignition, C) After 30 minutes, D) Carnation is mostly bleached except wilted edges.

Sulfur’s most common oxidation state is +6, as found in the sulfate ion. Sulfate ion is found in nature as calcium sulfate (the mineral gypsum) and magnesium sulfate (the mineral epsomite, or Epsom salt). We note that gypsum is used to make plaster, drywall, and cement. We explain that sulfuric acid is made from SO₂ by oxidation to SO₃ followed by the reaction of SO₃ with water. Sulfuric acid is indeed a very strong acid, because it completely dissociates in water, with two protons per molecule. We make it clear that concentrated sulfuric acid is pure H₂SO₄, unlike many other concentrated acids found in the laboratory (such as HCl and HNO₃) which are actually solutions in water. We show the heat of dilution of sulfuric acid with water in a Pyrex flask, slowly adding 20 mL of concentrated sulfuric acid to 200 mL of water to produce a 20 °C temperature increase.⁶

Video 1: Dehydration of sucrose by sulfuric acid (accessed May 2019 subscription required) Derived from Gary Trammell, Jerrold J. Jacobsen, Kristin Johnson, and John W. Moore. Chemistry Comes Alive! Volume 5: Abstract of Special Issue 29, a CD-ROM for Organic and Biochemistry, Journal of Chemical Education 2001 78 (3), 423. DOI: 10.1021/ed078p423.

Next we demonstrate the charring of sugar by sulfuric acid by adding 35 mL of concentrated sulfuric acid to a 250 mL beaker containing a mixture of 35 g of granulated sugar and 35 g of confectioners’ sugar (see video 1).⁷ This is stirred with a glass stirring rod for a few seconds and then placed in the fume hood.

Figure 6: A) Sulfuric acid was used to write H₂SO₄, B) Use of a heat gun reveals the message

Lastly we write a “secret” message on a sheet of paper (see figure 6) using 3 M sulfuric acid and expose the message by heating the paper using a heat gun, while taking the opportunity to stress the need for laboratory safety and awareness around corrosive chemicals by reciting the following poem:⁸

Little Willie took a drink,

And lived to tell no more

For what he thought was H₂O

Was H₂SO₄

For cleaning up, we neutralize the diluted sulfuric acid solution resulting from the heat of dilution demonstration using magnesium hydroxide powder to permit disposal down the sink. Each 20 mL of concentrated sulfuric acid requires approximately 21 grams of magnesium hydroxide to fully neutralize the acid. The advantages of magnesium hydroxide powder are that almost every high school laboratory has this compound and if an excess is used, the pH of the solution remains neutral.

References and Notes

1. An excellent discussion of the presentation of this demonstration may be found in: Shakashiri, Bassam A. Chemical Demonstrations: A Handbook for Teachers, Vol. 1; University of Wisconsin Press: Madison, WI, 1983; pp 53-54.
2. See Abstract 18-24 in Alyea, Hubert N. Tested Demonstrations in Chemistry, 6th ed.; Journal of Chemical Education: Easton, PA: 1965; pp 40.
3. (a) See Abstract 19-16 in Alyea, Hubert N. Tested Demonstrations in Chemistry, 6th ed.; Journal of Chemical Education: Easton, PA: 1965; pp 42; (b) Shakashiri, Bassam A. Chemical Demonstrations: A Handbook for Teachers, Vol. 2; University of Wisconsin Press: Madison, WI, 1985; pp 184-189.
4. See Abstract 19-15 in Alyea, Hubert N. Tested Demonstrations in Chemistry, 6th ed.; Journal of Chemical Education: Easton, PA: 1965; pp 42. Bell jars are expensive and it is possible to use an inexpensive substitute. For example, the top may be cut off a large plastic water bottle and the bottle inverted over the carnation and burning sulfur. A disposable container such as a metal jar lid is used to hold the burning sulfur.
5. See Abstract 19-17 in Alyea, Hubert N. Tested Demonstrations in Chemistry, 6th ed.; Journal of Chemical Education: Easton, PA: 1965; pp 42.
6. Laboratory safety instructions always call for concentrated acid to be added into water, and note that the water should never be added to the acid. The origin of this practice lies in the density and the heat of dilution of concentrated sulfuric acid. When poured into water, concentrated sulfuric will sink to the bottom of the water where the heat of dilution may be dissipated by the bulk of the water. By contrast, if water is added slowly to concentrated sulfuric acid, the water floats on the sulfuric and immediately becomes so hot as to boil, frequently spattering acid out of the container.
7. Summerlin, Lee R.; Borgford, Christie L.; Ealy, Julie B. Chemical Demonstrations: A Sourcebook for Teachers Volume 2, 2nd ed.; American Chemical Society: Washington, DC, 1988; pp 122. We use a mixture of confectioner’s sugar and granulated sugar to optimize the time required and the height of the carbon pillar. If it is desired to clean the beaker, the charred sugar residue should be removed from the beaker while still very warm and the beaker soaked in water overnight.
8. The author (SWW) first found this poem in a high school yearbook belonging to the Aurora, NE class of 1916.

There is a lab that is called something like “The Mole Rocket Lab” or  “Micro Rockets”. Some of you may be familiar with the lab, but I wanted to write this post to share it with teachers who may not be aware of it. 

The Mole Rocket Lab is an excellent opportunity to engage students in collecting data and making decisions about the best mole ratio of gases to use in their rocket. I also want to share how I implement the lab, which may be different than others facilitate it. This lab is one of my favorite activities to do in my classes and I look forward to it every year. The lab is simple, requires limited supplies, students love it (i.e. high engagement level), and I have found it to really set students up for stoichiometry.

Video 1: Mole Rocket Lab, Flinn Scientific YouTube Channel, Bob Becker, 12/19/12. (accessed 5/22/19)

I follow the basic procedure demonstrated in video #1. Other descriptions of the lab can be easily found if you do a web search for “Micro Rocket Lab” or “Mole Rocket Lab”. There is a time investment to build the nozzles for the gas generators and the piezo ignition devices. But, after that initial investment lab set-up is fast and simple in future years. 

I have attached the handout I give my students when completing this lab. Before students begin the lab, it is necessary to demonstrate how to set up the gas generators, and to show them how to collect the hydrogen and oxygen gases at the desired ratios. Students think the water displacement technique for measuring and collecting the gas ratios is really cool. My class periods are 75 minutes, and this is plenty of time to demonstrate the procedure, for students to collect the data they need, have time to shoot rockets if they want or get started writing their conclusion.    

After students collect their data and start on their conclusion, students will most likely need help when completing the table on the lab handout to determine the left-over reactants. The video referenced above provides a description of how to complete the table (I use the same description, but don’t show students the video). I typically show students how to complete the table for one or two of the mixtures, and leave them to figure out the rest of the table. I instruct students to consider their experimental results together with the expected left-over reactants of each mixture they tested and then write their explanation to the question, “Why are some mixtures of hydrogen and oxygen more explosive than others?” Students may at first feel unsure how to answer the question, but after a brief moment of thought or discussion within their group are usually able to come up with an explanation with little or no further guidance. Students’ explanations are required to be supported with an argument that includes, at minimum, the bullet list of items in the lab handout.

In the past, I have had students make whiteboards and share their results and thoughts with each other before writing their own individual conclusions. However, most student groups tend to reach similar conclusions without too much variability, which isn’t conducive to rich discussion. Therefore, I haven’t found it to be worth the class time to have students share their results and discuss with each other before they write their own individual conclusions for this lab. It is definitely worthwhile to have students write their own individual conclusions while consulting with their group members.

For me, this lab is a keeper because it provides a strong connection of a mole ratio to a real reaction and also provides a brilliant introduction to the concepts of mole ratios and limiting reactants, setting students up really well for the stoichiometry unit.

Determination of Lewis Dot structures and visualization of the shapes of molecules using valence shell electron pair repulsion theory (VSEPR theory) is an example of an abstract concept that students often find difficult to learn. I have found it useful to have a single worksheet/packet that my students can add to as we cover Lewis dot structures, resonance, VSEPR shapes, polarity, and intermolecular forces.

These topics are typically covered in the “Chemical Bonding” and “Molecular Geometry” chapters of textbooks. Having one worksheet seems to allow students to connect one topic to another as we proceed with our lessons and build concepts. We save some class time by referring to columns already filled in instead of redrawing Lewis structures of molecules, for example. After completing this worksheet, I find that students are able to draw structures, assign shapes, describe the polarity and intermolecular forces present for almost any simple molecule or ion I give to them. The worksheet includes both molecules and ions and examples that follow and many that violate the octet rule. Students learn to identify the “best” Lewis dot structure by minimizing formal charge to create expanded octets. Students work in pairs and use the model kits seen in Figure 1. Figure 1 is a copy of the picture I give to students within the model kit that describes what each of the pieces represents. Along with these worksheets, students and I use the “Bear Essentials Of Polarity” comic book¹ to explore polarity and a number of PhET simulations to look at molecular shapes² and molecular polarity.³

Figure 1: Labeled Model Kits

Kinesthetic (tactile) learners seem to favor building molecules with the model kits while visual learners tend to state a preference for the PhET interactive simulations, but all learner styles seem to benefit by completing this worksheet. My students have improved their test scores by an average of 9.43% (±1.27, n = 495 post and n = 1230 pre-use) over these topics since I have used the single worksheet, molecular models and PhET simulations. The VSEPR Summary Sheet (found in Supporting Information) is given to students only after they have completed the PhET simulation “Molecule Shapes Interactive Simulation”.² After practicing with the models and other tools, I have students work some of the examples for Lewis Structures without the use of model kits or simulation software so they can learn how to write them out by hand. They do not have access to the PhET simulations during tests (although I do allow them to use the molecular model kits if they choose). If you are logged into your ChemEd X account, you will see the student worksheet and the teacher’s answer key in the Supporting Information. 

Figure 2: Example Lewis structure

Student misconceptions seem to derive from their lack of understanding of 2-dimensional representations of 3-dimensional structures. For example, students will often times see 4 bonds to a central atom in a central molecule and believe the bonds are 90° apart because they are thinking in 2-D (x,y) space. Using the model kits, students can see that the correct arrangement of those electron pairs is actually the 109.5° idealized angle. If a student (correctly) draws figure 2 as their Lewis structure, they will often assign the angle as 180° instead of <109.5.

Working with models helps them to visualize these situations in 3-D space more accurately. Another misconception that I frequently encounter occurs with octahedral molecules. Students hear the “octa-” prefix and assume 8 atoms are bonded to the central atom instead of 6. They are not experienced enough to understand that there are 8 faces to an octahedron, not 8 atoms.