In one of my last blog posts I wrote of how I sometimes enjoy ending a unit with a series of demonstrations and using them to elicit a dialog between the students and myself to check for understanding. It is always a fascinating experience to hear the misconceptions that many students have the day before the test.

My kinetics unit has a very good review lecture where I take the kids through the six factors that affect reaction rate (concentration, temperature, agitation, catalysts, surface area, and nature of the reactants) by showing them demonstrations that illustrate each of the factors.  Most importantly I am trying to get my students to engage in a detailed discussion of what is happening at the molecular level. My whole approach is based on the idea of “Effective Molecular Collisions”. What is it that we can do to produce more collisions and speed up a chemical reaction? I have a phrase that I keep using over and over again: “the species must hit, they must hit hard enough, and hit in the right place”. How can these six factors help with that?

I use light sticks to illustrate the effect temperature has and ask them why light sticks in cold water glow dimmer and ones in hot water glow brighter to try to elicit a discussion of the speed at which the molecules are moving. My main point is the faster molecules at the higher temperature hit harder, more often, and because of the increased number of collisions there is an increase chance of it being in the right orientation to produce a reaction.

To discuss agitation I have a demo that is sometimes called “The Blue Bottle” or the “Traffic Light Reaction". When it is shaken in a closed flask oxygen gas in the flask collides with a mixture of dextrose and base to cause color changes in different acid base indicators. I have even seen some instructions that allow you to try and tailor it to your schools colors in one demo book but I can’t seem to recall which one. I like to point out to the students that most young kids learn these first two factors while watching people cook. Raise the temperature and mix the pot to help cook things faster. My main point here is that if we were not shaking the bottle the molecules would not be hitting as often. Especially since the oxygen is in the gas phase and not exposed to the entire volume of the solution.

Chemistry Comes Alive - Blue Bottle

To discuss surface area I have often shown a candle making contact with a block of wood, then a paper towel, and then Lycopodium powder. This is a little dangerous and maybe one I should rethink. I am not sure I want to show the old classic empty paint can version of this demo and teach students how to make an impromptu bomb. Showing a metal like magnesium in ribbon versus turnings reacting with HCl can illustrate the point nicely. My main point here is that the greater surface area provides more likely points of collision.

Chemistry Comes Alive - Lycopodium powder

For catalysts I have a great demo that shows the decomposition of tartrate ion in hydrogen peroxide. The catalyst is cobalt chloride and it changes to a deep green color while reacting (illustrating a visible activated complex) and then returns to its red color. Ironically the AP Biology teacher in the next room watched me do this one day and is now incorporating it into his lessons on enzymes. My main point here is that the cobalt provides a catalytic intermediate and surface for the reaction to happen on.

Chemistry Comes Alive - Decomposition of tartrate ion in hydrogen peroxide

For the kind of eclectic idea of the nature of reactants I show several things that do react and several that don’t. I like to put copper in water (no reaction), show a precipitation reaction, and even the classic freeze a beaker to a board reaction. In a very large lecture hall I have even done this by explodingballoons of (1) helium, (2) hydrogen, and (3) hydrogen and oxygen in a 2:1 mix. This is not for the inexperienced teacher. My main point being that some things will not react fast (or at all) no matter what you do.

Chemistry Comes Alive - Precipitation

To illustrate concentrations effect on a reaction I like to use the iodine clock reaction. I have a student help me run several mixtures in a row where I start with 50 mL of the first solution (A) and 50 mL of the second solution (B) and time the appearance of blue color. We then do the same thing with only 40 mL of solution A that has been diluted with 10 mL of distilled water to maintain a constant volume. We continue with 30, 20, and 10 mL samples each diluted with enough distilled water to make a constant volume of 50 mL. Each one takes longer than the previous one and we plot the data (mL A versus time) to get a nice curve. I ask my students to predict how many mLs of A would be needed for a reaction of a specific time that I choose and have them predict from their graphs. I like to tell them that it is a “group quiz” and if they are correct they will get 50 points. For every second they are off I will reduce their score by ten points. It can get some heated debate started in the room. My main point here being that increasing the number of molecules present increases the chance of a reaction.

Chemistry Comes Alive - Iodine Clock

Depending on the time I have available for this lecture I have several other kinetics demos I like. I show “Hooberman Balls” to illustrate activation energy, the Old Nassau Clock reaction to show intermediates, and even an Oscillator to show the same thing. For rate determining steps I use a stack of funnels on a ring stand and pour water through them into a bucket. I learned that one from a Flinn workshop.

I have been doing these demonstrations for many years. My personality has allowed me to come up with many anecdotes about them that are high school appropriate. I am sure that all of you have your own ways of tailoring these demos to your stories. 

I am very grateful to Don Showalter of the University of Wisconsin at Stevens Point for showing me how to bring these specific reactions together. Also Larry Quimby and Lanny Larsen of my school (Francisco Bravo Medical Magnet High School) spent many years dong them with me and helping me develop the presentations. In fact we often brought all three of our classes together in one room to team-teach these days. It has proved to be a very effective method of reviewing having three teachers all together in the same room at the same time. I have a great love now for team teaching.

I have attached a file to this blog post that I use to set the lecture up. It has the recipes and equipment lists for the way I do the lecture. It also contains a copy of the graph we pass out for the iodine clock experiment. As always with any experiment or lab be sure to follow the necessary safety practices and remember the five P’s. Prior practice prevents poor presentations. I have provided a basic outline of the activities and materials below. You can find more detailed directions online, in a demo book or in some of the videos linked here. 

As always you can follow all my NErDy adventures on Twitter @morganchem

I have a confession to make: I don’t really understand how to correctly predict the electronic configurations (EC) of every element and ion. 

Until recently, I thought I had everything figured out.  In fact, for quite a long time I have believed that I knew – at least in principle – how to predict the EC of any element or ion. Having read several articles in the Journal of Chemical Education on this subject,^1,2 I understood that the ground state EC of an atom or ion is a function of the lowest energy arrangement of ALL electrons in that atom or ion. I understood that confusion arises in predicting EC when the focus is placed solely on the energy of the very last electron (or last few electrons) being “placed in” orbitals during the “building up” of the atom or ion.

But I also held a misconception regarding EC: I thought that the 4s orbital was ALWAYS higher in energy than the 3d orbital. My justification for this erroneous belief came from information in two papers published in JCE^1,2. I won’t bog you down with all the details, but keep in mind that the title of one of these papers is “4s is Always Above 3d!”¹ However, I learned that this idea is incorrect during a conversation on Twitter with Dave Doherty. Dave alerted me to another publication in JCE which claims that in K and Ca, the 4s orbital is lower in energy than the 3d!³ After reflecting on that conversation with Dave, the arguments in these various JCE publications, and the data contained within, I concluded that my understanding was wrong. 4s is NOT always above 3d!

What is my point in sharing all of this with you? Well, consider that I have been teaching science and chemistry for over 20 years, I have a Ph.D. in physical chemistry, and I still don’t completely understand what is going on with EC. It is my strong suspicion that other teachers of science and chemistry also struggle with completely understanding this material and explaining it to students. There appears to be no way to present the concept of EC to students in a manner that is easy to grasp and faithful to physical reality at the same time.  Consider that one author has argued that five concepts are needed to understand “The Full Story of the Electronic Configurations of the Transition Elements”³: d-orbital collapse, d vs. s electron repulsions, s-Rydberg destabilization, configurations and states in free and bound atoms, and relativistic spin-orbit coupling. I don’t know about you, but these concepts are going to be tough for my students to understand – and present challenges to my intellectual horsepower, too! Eric Scerri has written extensively on the electronic configurations of the elements, and he has noted that “contrary to what some educators may wish for, there is no simple qualitative rule of thumb that can cope with this complicated situation”.⁴

I shared with Dave my frustrations on this subject.  I communicated with him my desire to present the prediction of the EC of elements and ions to my students in a manner that:

1. Is understandable to both teachers and students alike.

2. Chemical educators can generally agree upon.

3. Is faithful to physical reality as much as possible.

4. Can be justified with theory that both teachers and students can understand.

Dave met my challenge head on, and put together some ideas on how to present a coherent and accurate picture of electron configuration. I encourage you to read his article, Clarifying Electron Configurations! 

Dave Doherty develops physically accurate, 3D particle models of atomic and molecular structure, chemical reactions, and other chemical concepts and the Atomsmith software⁵ that allows students and teachers to interact with and “perform experiments” on these models. He can be reached at ddoherty@bitwixt.com. He uses @Atomsmith1 on Twitter to share ideas about chemistry education and he uses @AtomNMolecules to challenge college chemistry professors on topics such as electron configuration.

References:

1. Pilar, F. L. 4s is Always Above 3d!, J. Chem. Educ., 1978, 55, 2 – 6.

2. Reed, J. L. The Genius of Slater’s Rules, J. Chem. Educ., 1999, 76, 802 – 804.

3.  Schwarz, W. H. E. The Full Story of the Electron Configurations of the Transition Elements, J. Chem. Educ., 2010, 87, 444 – 448.

4. Scerri, E. The trouble with the aufbau principle, 2013, http://www.rsc.org/eic/2013/11/aufbau-electron-configuration.

5. Atomsmith Classroom, Bitwixt Software Systems, www.bitwixt.com. Available for Mac and Windows computers, and as an online HTML5 app for browsers on all platforms.

The Aufbau Principle: the (n + l) Rule

We’ve all seen and use the so-called Aufbau Diagram (Figure 1). It is a mnemonic used to remember the order of “filling” of atomic orbitals during the construction of the ground state electron configurations of the elements. The presentation of this diagram is largely disconnected from any physical meaning. Here’s what we tell our students: “Memorize the diagram, learn to use it, and you’re guaranteed to get the right answer.”

Aufbau Diagram

Figure 1. The Aufbau Diagram: Atomic orbitals are filled starting at 1s and continuing, from the upper left, in the order indicated by the arrows.

Is there a way to connect this diagram to its physical meaning? Yes! That is the goal of this article.

How was this diagram constructed in the first place? It turns out that it is a representation of a method of predicting the “order of filling” called the Madelung rule, which is also called the (n + l) rule. The “n” and “l” in the (n + l) rule are the quantum numbers used to specify the state of a given electron orbital in an atom.  n is the principal quantum number and is related to the size of the orbital. l is the angular momentum quantum number and is related to the shape of the orbital.

Here’s how the (n + l) rule works. The (relative) energies of the orbitals can be predicted by the sum of n + l for each orbital, according to the following rules:

a. Orbitals are filled in order of increasing (n + l), which represents the relative energy.
b. If two orbitals have the same value of (n + l), they are filled in order of increasing n.

The diagram in Figure 1 is the result of these rules.

Figure 2 is a version of the diagram that displays the dependence on (n + l) for each orbital, where E represents the relative energy of the orbitals. The orbitals are filled according to the values of E for each orbital: E=1 for 1s, E=2 for 2s, E=3 for 2p and 3s, and so on. According to rule (b) above, when two orbitals have the same E, such as E=3 for 2p and 3s, the orbital with lower n (2p) is filled first.

Detailed Aufbau Diagram

Figure 2. An Aufbau diagram that illustrates the (n+l) rule.

The (n + l) rule is a remarkably clever and useful tool. It correctly predicts the order of orbital energies through element 20 (calcium). It also correctly predicts many electron configurations beyond that. And here we arrive at a very important point: predicting the relative energies of each orbital is not the same thing as predicting correct electron configurations. More on this point later.

Why does the (n + l) rule work? It’s not magic and now we’ll discuss the connection between the rule and its physical meaning. To understand the connection, we need to start with how the quantum numbers n and l are related to the energy of an orbital. We’ll use 3D models (actually 2D images of the 3D models) of atomic orbitals to demonstrate. [Sorry to disappoint those looking for a deep dive into quantum mechanical calculations. These models are visual representations of the results of those calculations.]

In Figure 3, we see a representation of the orbitals occupied by the electrons in the ground state of the element krypton (for clarity, the orbitals have been separated from one another). Notice that as the quantum number n increases (from 1 to 4 in krypton), so does the overall size of the orbital.

Electronic Configuration of Krypton

Figure 3. the electron configuration of krypton. (Generated using the Electron Configuration Lab of Atomsmith Classroom¹)

How is the size of the orbital related to its energy? Recall that the potential energy of attraction between protons and electrons, which have opposite charges, depends on the distance between them: the closer an electron gets to the protons in the nucleus, the lower its energy will be. Compare the sizes of the 1s (n = 1) and 4s (n = 4) orbitals (Figure 3). Because the 1s orbital is smaller, the average distance of an electron to the nucleus will be smaller than that of the electrons in the 4s orbital. That’s the connection – the higher n is, the higher the energy of the orbital. 

What about the l in the (n + l) rule? As mentioned above, l, the angular momentum quantum number, determines the shape of an orbital. In all orbitals for which n > 1, there are areas, called nodes, in which it is extremely unlikely to find an electron. There are two types of nodes: radial and planar (or angular).  Figure 4 illustrates the radial node in a 2s orbital (l = 0) and a planar node in a 2p orbital (l = 1). Note that radial node (Figure 4, center) does not cross the nucleus, whereas planar nodes (Figure 4, right) do. s orbitals (which all have l = 0) contain only radial nodes. All other orbitals (p, d, f, etc., for which l > 0) contain both radial and planar nodes.

2s and 2p orbitals

Figure 4. Left: 2s and 2p orbitals, overlapped. Center: radial node (l = 0) in a 2s orbital (green circle). Right: a planar node (l = 1) in a 2p orbital (green line). The 2s and 2p orbitals (center and right) have been “sliced” in Atomsmith’s Orbital Lab.

The total number of nodes (radial + planar) in an orbital is equal to (n – 1). Of these, l nodes are planar.

How does the number of planar nodes affect the energy of an orbital? Look again at the radial and planar nodes in Figure 4: the planar node crosses the nucleus – where the positively charged protons are. Radial nodes do not cross the nucleus. 

If a node is an area where an electron is not likely to be found, then electrons in orbitals with planar nodes are likely to be found farther from the nucleus (on average). As we discussed earlier, large distances from the nucleus means higher energy. Thus, the higher the value of l, the more planar nodes an orbital has, and the higher the orbital energy.

So the (n + l) rule is a way to account for the two main factors that affect the relative energies of atomic orbitals: the size of the orbital (depends on n) and the number of planar nodes (= l). In cases where (n + l) is the same for two orbitals (e.g., 2p and 3s), the (n + l) rule says that the orbital with lower n has lower energy. In other words, the size of the orbital has a larger effect on orbital energy than the number of planar nodes.

Like all Models, Push Aufbau (n + l) Far Enough and it Fails.

The (n + l) rule is a model. And, as we tell our students, all models have limits. The (n + l) rule works quite well up to Z = 20, calcium (Z is the atomic number).  What does “works well” mean? It successfully predicts two things: 

1. the relative energies of the orbitals
2. the order in which the orbitals are occupied

It may not be obvious that these two things are different. But they are, and the differences start to matter at Z = 21, scandium – the beginning of the transition metals.

For Z = 20, calcium, the (n + l) rule says:

• the 4s orbital is lower energy than the 3d orbital
• the 4s orbital is occupied and the 3d orbitals are not (1s² 2s² 2p⁶ 3s² 3p⁶ 4s²).

These are both correct!

For Z = 21, scandium, the (n + l) rule says:

• the 4s orbital is lower energy than the 3d orbital
• the 4s orbital is occupied and one 3d orbitals is occupied (1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹).

Here’s where the (n + l) rule first fails. #2 (the occupation) is correct, but #1 is incorrect. For transitions metals, 3d is lower in energy than 4s! Figure 5 shows the relationship between orbital energy and atomic number (Z). Notice that the curves of the 4s and 3d orbital energies cross at Z = 21. 

4s vs. 3d Energies

Figure 5. The relationship between orbital electronic energy and atomic number (Z).

However, and this is an important point: even though the (n + l) rule gets the orbital energies wrong, it still gets the electron configuration (orbital occupancies) right!

How is it possible that, for transition metals, the 3d orbitals are lower in energy, but they are not preferentially occupied?

The short answer is that the orbital energies are not the only important factor in determining how the orbitals are occupied. The long answer? It’s complicated – very complicated.

Prof. Dr. W.H. Eugen Schwarz, a theoretical chemist at the University of Siegen in Germany has published a number of papers on this very subject. His results are clearly beyond the scope of any introductory chemistry course, but we hope to give you a flavor of how other factors besides orbital energies may influence the occupancy of atomic orbitals in an electron configuration.

Schwarz elucidates five factors that influence the electron configuration of transition metals:²

1. d-orbital collapse
2. d versus s electron repulsions
3. s Rydberg destabilization
4. configurations and states in free and bound atoms
5. relativistic spin-orbit coupling

We’ll look exclusively at the second factor: d versus s electron repulsions.

Let’s consider titanium (Z = 22). Its electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d², which the (n + l) rule correctly predicts. If the electron configuration depended solely on the orbital energies, we would expect: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁴ – with no electrons in the 4s orbital.

Why don’t the last four electrons preferentially occupy the 3d orbitals, which are lower in energy than the 4s orbitals?

Consider Figure 6a, where we see models of the 4s and 3d orbitals, separated in Atomsmith Classroom’s Electron Configuration Lab. If the electron configuration of titanium was      1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁴, four of the five 3d orbitals would contain one electron each. And the 4s orbital would be unoccupied.

In Figure 6b, the 3d and 4s orbitals have been superimposed on one another around the nucleus. Just as protons and electrons attract each other due to their opposite charges, electrons repel each other because they have the same charge. This repulsion results in a higher energy – things are simply getting crowded.

What can the electrons do to minimize these repulsions? Notice that the 4s orbital is larger than the 3d orbitals. If two of these electrons find their way into the 4s orbital instead of 3d orbitals, they have more space to spread out to minimize the repulsion. This is the basis of Schwarz’s “d versus s electron repulsions.”

4s and 3d Orbitals, Expanded

Figure 6a. The 4s and 3d orbitals separated.

fig06b_collapsed_white.png

Figure 6b. 4s and 3d orbitals overlapped.

How Can You Use This?

Let’s summarize what we’ve discussed so far:

Up to Z = 20 (calcium), the (n + l) rule (and the Aufbau diagram) correctly predicts:

• Orbital energy levels

The order of occupancy of the orbitals

• The physical meaning of the (n + l) rule (and its ability to make these predictions) is related to the size (n) and shape (l) of a given orbital.

For Z > 20 (starting at the transition metals):

• The (n + l) rule is not able to correctly predict orbital energy levels.
• Even when we know the orbital energies, this knowledge is not sufficient to predict the order of filling. Other factors, such as “d vs. s electron repulsions” (crowding) must be considered. (Schwarz discusses four more of these).
• Although its physical meaning is no long sufficient, the (n + l) rule still correctly predicts the order of filling. Except where it doesn’t and we invoke “exceptions.” 

The first point to be taken from this is that the (n + l) rule is a model and that it works… until it doesn’t. If you choose to teach it as a model and connect it to some of the physical meaning discussed above, it’s a great example of how models can be both useful and also fail.

The “story” outlined above has the potential to be much more fulfilling for your students than “Memorize the diagram, learn to use it, and you’re guaranteed to get the right answer.” But it’s a tough story to tell by just waving your hands. You need a model to tell it, and the model needs the following features:

1. Students must understand the basics of coulomb interactions: opposite charges are lower in energy when they are close together; the repulsions of like charges result in increased energy.
2. Representations of the atomic orbitals that are physically accurate in both size (n) and shape (l)
3. 3D is better than 2D
4. The orbitals should be separable and superimposable
5. Interactivity is desirable

You can’t tell this story without the ability to show your students the relative sizes and shapes (i.e., the nodes) of the orbitals (#2). Pictures of the orbitals in a textbook can work for many students; but all students will benefit from the ability to interactively observe (#5)  the sizes and shapes in 3D (#3), and to separate and superimpose them (#4; Figures 6a and 6b) so that they can gain an appreciation for how crowded an atom really is.

The Aufbau principal, first envisioned by Niels Bohr in 1920, and its implementation as the (n + l) rule is a very useful abstraction. Connected to its physical meaning, it can become part of powerful mental model that students can draw on to build (and explain) their understanding of the structure of the atom. This kind of connection demonstrates the real promise of 3D particulate representations of atomic and molecular structure and phenomena. Many more of these kinds of stories will be told. 

Author's note: The idea for this article arose from a discussion between the author and Tom Kuntzleman. Tom describes this interaction in a blog post, Conversations, Confessions, Confusions (and hopefully some Clarity) on Electronic Configurations.

References:

1. Atomsmith Classroom, Bitwixt Software Systems, www.bitwixt.com(link is external). Available for Mac and Windows computers, and as an online HTML5 app for browsers on all platforms.
2. Schwarz, W. H. E. The Full Story of the Electron Configurations of the Transition Elements, J. Chem. Educ., 2010, 87, 444 – 448.

            With the end of the school year approaching, educators are not only developing their semester exams, they are preparing for the upcoming school year as well. Although each individual educator has their own approach to improving their curriculum, many will be spending their summer aligning their curriculum to the Next Generation Science Standards. Currently eighteen states have adopted the Next Generation Science Standards, with additional states developing their own modified version. The idea of revising curriculum for each and every course can be daunting as educators try to identify a common theme that can be applied throughout the entire department. So where do we start? How do we thread a common theme for the professional development provided in our subject area?

            As a chemistry educator I have spent the last year working with colleagues to align our chemistry standards with NGSS. After reviewing the standards it was apparent that our chemistry department would require a shift in our instructional approach but where do we begin?

            A resource that I have found essential to developing our revised instructional approach is Brian J. Reiser’s “What Professional Development Strategies Are Needed for Successful Implementation of the Next Generation Science Standards?”. Reiser provides a thorough explanation of the interconnected goals of core ideas, practices, and coherence, and the resulting shifts in instructional strategy that should occur. In addition, he provides the reader with several challenges that educators may face when implementing the NGSS Framework such as; how to structure a lesson, how to develop explanatory models, developing an argument and reaching a consensus, and building classroom culture. This document provides justification for each instructional shift and provides ideas on how to develop curriculum in which students are continuously building on their explanatory model.

            Although this document can be an excellent resource for any individual educator I suggest sharing it with your department. According to Reiser, “the application of these ideas need to be connected to particular subject matter contexts, such as helping teachers investigate how to help students develop explanatory accounts using the particle model of matter, or evidence based arguments” (p.13). If all professional learning communities, or departments, are on the same page then professional development can then be adapted from the ideas and standards for each curriculum. I strongly recommend implementing the ideas from this resource into your curriculum, whether or not your state has adopted the Next Generation Standards or not.  

Work Cited:

I have been on a mission lately to make scientists out of my students. I am long past my fears that they are not capable of discovering the world for themselves or that they won’t learn the content if we spend too much time on science practices. What I have to work on now is orchestrating the experience. The pedagogy underlying Modeling Instruction has become the backbone for much of my instruction lately. This method of instruction not only gives my students an engaging, authentic scientific experience but has resulted in deeper content knowledge.

One thing I have struggled with is how to capture that scientific experience. How do I give my students constructive, quantifiable feedback on their scientific habits? How do I incorporate a more formal writing process that addresses the Common Core ELA standards? Some of those questions have been answered through the recently-published Argument-Driven Inquiry in Chemistry, published by NTSA. Filled with thirty “Investigation” and “Application” labs that span the curriculum, this resource helps to formalize the scientific experience. The authors’ suggested instructional methods parallel Modeling Instruction, including self-designed lab procedures and white boarded circle discussions. The labs and accompanying resources then take those Claim-Evidence-Reasoning whiteboard conversations and formalize them into an investigation report.

The lab scenarios are simple, yet engaging. When we did a version of Lab 17 (Limiting reactants), students were seeking out the ideal ratio of vinegar to baking soda. One student remarked “This is the coolest lab ever!” as we mixed these two reactants together much as he probably did in preschool. Students were actively seeking data that would provide them a means to answer the question. They were independently critiquing each other’s data and conclusions. They were asking if they could perform new and different trials to try and gather more conclusive data. When they completed their reports, they really wanted me to be convinced that their claim was correct. They were genuinely proud of their work.

I have particularly enjoyed the investigation report rubric. While there are certainly formatting considerations in lab reports, to me the most important aspect is the content. While the rubric does seek to address format and writing style, the emphasis is on the student’s articulation of their thinking. Do my students’ reports show that they can connect all the dots from a question posed to a procedure that will provide valid data? Can my students analyze their data in a way that allows them to draw a conclusion? More broadly, can my students consider a question that’s a little beyond the forefront of their knowledge and use their skills as scientists to move their understanding forward? I can use the rubric to answer those questions.

This publication is also available as an e-book. NSTA members may be able to purchase this book at a discounted price through the NSTA Science Store.

Organic chemistry was when I fell in love with chemistry. Also known as Chem 210 at the University of Michigan, it was the first time I actually started to connect what was going on at the nanoscopic level to the macroscopic world. Since then, I’ve been hooked.

As a teacher, I have grown a lot over seven years (including student teaching). How do I get my students to make connections to the nanoscopic without, you know, curved arrow mechanisms? I have been fortunate throughout the years to piece by piece gain new perspectives that I thought I’d summarize and share with you - in fact, I’ve effectively rearranged my whole first year chemistry course to be built upon a progressively more in depth view of the nanoscopic. In this post, I will focus on only my reactions unit. This is in the second semester after students learn about the mole and empirical formula.

In our reactions unit in the second semester, we go all in.

1. First, students learn how to balance, classify reaction types, and predict products.

This part is where my former mentor, Julie Andrew of CU Boulder, really helped take this unit to the next level. She shared a lab with me (that I’ve edited from her original document) where not only do students practice predicting products, but they get practice in experiencing when predictions fail. Some of the reactions are designed so that they get results that DON’T match their predictions. This allows for students to (1) make a real conclusion if their predictions matched their observations and (2) ask new questions that lead me to showing splint tests. Here is an example. When students predict the products for the reaction of hydrochloric acid and sodium bicarbonate, they predict sodium chloride and carbonic acid, since they see it as a double replacement. This is 100% valid based on what they have learned. However, this is what actually happens: HCl + NaHCO3→ NaCl + H2O + CO2.

In our whole class debrief, we go through EVERY reaction after they share their data on the board. I tell them they are smart for making that prediction once they find it fails- it’s what scientists do ALL the time- make predictions based on prior knowledge to sometimes find that they were wrong. It is helpful to give them the "maybe" option. See a sample class data set below- this gave us great ways to start class conversations.

B. Here’s where we dive into the nanoscopic - the animation project. I introduce the project, and then do a few lessons first.

1. 1. Lesson: Dissolving - ionic vs covalent compounds (edited from a posted PHET - credit is within the document). My students really struggled with the vocabulary of dissolve vs. dissociate, even though they could find errors in particulate diagrams. So the next day, this was their warm up. It was quite telling (PS- yes the phosphate has dissolved in water and has dissociated from the sodium. However, the phosphate ion itself doesn’t dissociate further).

2. 2. Notes: Redox vs. Precipitation Reactions

   3. Now, groups of 2-4 students choose two reactions from their previous lab to make animations to connect the nano and macroscopic representations. They must choose a precipitation reaction and a redox reaction. Here is a link to the videos they made.

One Bigger Con:

1. Time. It takes time to teach this and time to make the animation. I have posted a pseudo-POGIL-style PHET activity below that prepared students for animations. I also posted the project guidelines (thank you Julie Andrew at CU Boulder for the nuts and bolts of this!!!!!). Word of the wise: google slides is also awesome, and in some cases, more awesome than ChemSense referenced in the instructions.

A Few Pros:

1. Time “lost” in this project reaps benefits in dividends in stoichiometry. This is the first year (!!!) I’ve taught stoichiometry with BCA tables and the animation projects before were an unintentionally amazing scaffold. I have NEVER seen my students so successful with stoichiometry as I’m seeing now, and my hunch is that the animation projects helped make the BCA tables more accessible.

2. I sent the animations to MEL Science. They haven’t gotten back to us yet, but my students were pretty stoked to send off the animations to a company for feedback.

I hope this is helpful and sparks ideas for the future, and I’d love to hear more of what you do too!

What am I doing to help kids achieve?

How do I know when they are there?

What is the evidence?

  I am facing what many teachers are facing. It is AP week, I am trying to continue "as usual" with doing labs and learning but this time of year is anything but "as usual". There is a rates lab we do this time of year which is a good lab, rather involved with a significant amount of set up and work. I got an idea for a slightly different rates lab from Bob Worley. I found a similar large scale version from Flinn Scientific. Thanks to Bob, I decided to do a microscale version.

  Here is the lab. Students take a solution of sodium thiosulfate and add a few drops of hydrochloric acid. The reaction ends with sulfur forming and making the solution cloudy. There is a suggested series of reactions that occur before the sulfur forms. There are some concerns with doing this on a large scale. First, there is a good chance of getting sulfur dioxide which smells bad and can form sulfuric acid. Second, it is hard to know exactly when the reaction ends.

  Here is what the students did on a microscale. We counted drops of sodium thiosulfate. In our system, 20 drops of 0.1 M sodium thiosulfate and 2 drops of 1 M HCl had a reaction that lasted about 2 minutes. Students did other reactions with fewer drops of sodium thiosulfate and more drops of water (18 drops of sodium thiosulfate, 2 drops of water....16 drops of sodium thiosulfate and 4 drops of water etc...). The also tested substances, like copper, to see if it would act as a catalyst. Although we did not get to it, I also examined temperature on my own. Instead of using hot water baths, I placed the chemicals in a microwave for about 15 seconds. The solutions heated up just enough to show a difference in the reaction rate (caution..do not heat the sodium thiosulfate above 60 degrees). This was simple, quick, easy and gave great results. Students also counted the drops of solution that would make 1 mL so they could use this as a conversion to calculate the concentrations of the diluted solutions. Here is the part about this lab that I really liked. I had students use their cell phones and a watch to capture the reaction on video so they could go back and compare the reactions to determine the time for them to finish. Here is the video.

  If they had trouble seeing how each reaction ended and the times, they could go back as many times as they needed and watch the video. Overall, the data was not bad. I would probably try this again next year with a few tweeks. I wanted it to be more inquiry but we just did not have the time to fully investigate or have students develop their own experiments, but you could do it and on a microscale it is O.K. if mistakes are made. Also, because of the small scale, the sulfur dioxide was not a problem. Give it a try...let me know what you think....

Thinking Like a Chemist

The May 2016 issue of the Journal of Chemical Education is now available online to subscribers. Topics featured in this issue include: assessment & learning theories, science literacy & chemical information, engaging young chemists in chemistry, analysis of real-world samples, organic chemistry in the classroom and lab, computational chemistry in the laboratory, thermodynamics, kinetics projects, understanding hydrophobic & hydrophilic materials.

Assessment & Learning Theories

Cover

Expertise in chemistry requires not only content knowledge, but also an ability to recognize and organize information based on underlying principles in the field. In Thinking Like a Chemist: Development of a Chemistry Card-Sorting Task To Probe Conceptual Expertise Felicia E. Krieter, Ryan W. Julius, Kimberly D. Tanner, Seth D. Bush, and Gregory E. Scott describe an instrument wherein participants sort a set of cards containing chemistry problems, which allows an exploration of how individuals with different levels of training organize chemical information. The dendrogram depicted on the cover shows that chemistry faculty tended to organize concepts around predictable, underlying principles, while novices tended to organize around superficial features.

Assessing how students learn is also examined in: 

Establishing the Validity of Using Network Analysis Software for Measuring Students’ Mental Storage of Chemistry Concepts ~ Kelly Y. Neiles, Ivy Todd, and Diane M. Bunce

Investigating General Chemistry Students’ Metacognitive Monitoring of Their Exam Performance by Measuring Postdiction Accuracies over Time ~ Morgan J. Hawker, Lisa Dysleski, and Dawn Rickey

Editorial

In the Editorial It Is Time To Say What We Mean, Melanie M. Cooper argues that it is now time to be more specific about what is meant when effective pedagogical approaches and the desired outcomes are discussed. One approach she discusses is to adopt the scientific practices from the Framework for Science Education.

Commentary

Why Teach Molality in General Chemistry? ~ Faisal A. Omar, Benjamin L. Dreher, and Nathan S. Winter

Science Literacy & Chemical Information

Transforming Undergraduate Students into Junior Researchers: Oxidation–Reduction Sequence as a Problem-Based Case Study ~ Tiina Saloranta, Jan-Erik Lönnqvist, and Patrik C. Eklund

Developing Students’ Critical Thinking, Problem Solving, and Analysis Skills in an Inquiry-Based Synthetic Organic Laboratory Course ~ Marisa G. Weaver, Andrey V. Samoshin, Robert B. Lewis, and Morgan J. Gainer

Review and Comparison of the Search Effectiveness and User Interface of Three Major Online Chemical Databases ~ Neelam Bharti, Michelle Leonard, and Shailendra Singh

Integrating the Liberal Arts and Chemistry: A Series of General Chemistry Assignments To Develop Science Literacy ~ Diane M. Miller and Demetra A. Chengelis Czegan

Literature-Based Problems for Introductory Organic Chemistry Quizzes and Exams ~ Kevin M. Shea, David J. Gorin, and Maren E. Buck

Using Student-Made Posters To Annotate a Laser Teaching Laboratory ~ Cindy Samet

Engaging Young Chemists in Chemistry

Evaluating a College-Prep Laboratory Exercise for Teenaged Homeschool Students in a University Setting ~ Daniel A. Hercules, Cameron A. Parrish, and Daniel C. Whitehead

Tournament of Young Chemists in Ukraine: Engaging Students in Chemistry through a Role-Playing Game-Style Competition ~ Denis Svechkarev and Oleksiy V. Grygorovych

Obtaining and Investigating Amphoteric Properties of Aluminum Oxide in a Hands-On Laboratory Experiment for High School Students ~ Kinga Orwat, Paweł Bernard, and Anna Migdał-Mikuli

Analysis of Real-World Samples

Demonstrating the Presence of Cyanide in Bitter Seeds while Helping Students Visualize Metal–Cyanide Reduction and Formation in a Copper Complex Reaction ~ Giorgio Volpi

Using Differential Scanning Calorimetry To Explore the Phase Behavior of Chocolate ~ Michael J. Smith

Determination of Sulfate by Conductometric Titration: An Undergraduate Laboratory Experiment ~ Jennifer Garcia and Linda D. Schultz

Organic Chemistry in the Classroom and Lab

A Mailman Analogy: Retaining Student Learning Gains in Alkane Nomenclature ~ Jessica Orvis, Diana Sturges, Shannon Rhodes, Ki-Jana White, Trent W. Maurer, and Shainaz M. Landge

Beyond Clickers, Next Generation Classroom Response Systems for Organic Chemistry ~ Kevin M. Shea

Laboratories

Synthesis of a Parkinson’s Disease Treatment Drug, the R,R-Tartrate Salt of R-Rasagiline: A Three Week Introductory Organic Chemistry Lab Sequence ~ Noberto Aguilar, Billy Garcia, Mark Cunningham, and Samuel David

Azeotropic Preparation of a C-Phenyl N-Aryl Imine: An Introductory Undergraduate Organic Chemistry Laboratory Experiment ~ Lee J. Silverberg and David J. Coyle , Kevin C. Cannon , Robert T. Mathers and Jeffrey A. Richards , John Tierney

Reaction of Orthoesters with Amine Hydrochlorides: An Introductory Organic Lab Experiment Combining Synthesis, Spectral Analysis, and Mechanistic Discovery ~ Shahrokh Saba and James A. Ciaccio

A Hydrazine-Free Wolff–Kishner Reaction Suitable for an Undergraduate Laboratory ~ Philippa B. Cranwell and Andrew T. Russell

Combinatorial Solid-Phase Synthesis of Aromatic Oligoamides: A Research-Based Laboratory Module for Undergraduate Organic Chemistry ~ Amelia A. Fuller

Computational Chemistry in the Laboratory

Integration of Computational Chemistry into the Undergraduate Organic Chemistry Laboratory Curriculum ~ Brian J. Esselman and Nicholas J. Hill

A Simple Molecular Dynamics Lab To Calculate Viscosity as a Function of Temperature ~ Logan H. Eckler and Matthew J. Nee

Thermodynamics

A Student-Constructed Galvanic Cell for the Measurement of Cell Potentials at Different Temperatures ~ Anna Jakubowska

Measuring Vapor Pressure with an Isoteniscope: A Hands-On Introduction to Thermodynamic Concepts ~ Wenqian Chen, Andrew J. Haslam, Andrew Macey, Umang V. Shah, and Clemens Brechtelsbauer

Correct Use of Helmholtz and Gibbs Function Differences, ΔA and ΔG: The van’t Hoff Reaction Box ~ Leslie Glasser

Comment on “An Alternative Presentation of the Second Law of Thermodynamics” ~ Howard DeVoe

Reply to “Comment on ‘An Alternative Presentation of the Second Law of Thermodynamics’” ~ Sangyoub Lee, Kyusup Lee, and Jiyon Lee

Kinetics Projects

Synthesis and Decomposition Kinetic Studies of Bis(lutidine)silver(I) Nitrate Complexes as an Interdisciplinary Undergraduate Chemistry Experiment ~ Vishakha Monga, Guillaume Bussière, Paul Crichton, and Sailesh Daswani

The Alcohol Dehydrogenase Kinetics Laboratory: Enhanced Data Analysis and Student-Designed Mini-Projects ~ Todd P. Silverstein

Distilling the Archives: Understanding Hydrophobic & Hydrophilic Materials

This issue includes a way to demonstrate Electrophoretic Separation in a Straight Paper Channel Delimited by a Hydrophobic Wax Barrier by Chunxiu Xu, Wanqi Lin, and Longfei Cai. Past issues of the journal include a number of articles on understanding hydrophobic and hydrophilic materials, including:

Hydroglyphics: Demonstration of Selective Wetting on Hydrophilic and Hydrophobic Surfaces ~ Philseok Kim, Jack Alvarenga, Joanna Aizenberg, and Raymond S. Sleeper (Tom Kuntzleman wrote an enthusiastic blog about this paper.)

Colorful Lather Printing ~ Susan A. S. Hershberger, Matt Nance, Arlyne M. Sarquis and Lynn M. Hogue

Bubble, Bubble, Toil and Trouble ~ JCE staff

On the Surface: Mini-Activities Exploring Surface Phenomena ~ JCE staff

Magic Sand ~ JCE Staff

Magic Sand: Modeling the Hydrophobic Effect and Reversed-Phase Liquid Chromatography ~ Ed Vitz

A Simple Flotation De-Inking Experiment for the Recycling of Paper ~ Richard A. Venditti

New Nanotech from an Ancient Material: Chemistry Demonstrations Involving Carbon-Based Soot ~ Dean J. Campbell, Mark J. Andrews, and Keith J. Stevenson

Preparation of Transparent Superhydrophobic Glass Slides: Demonstration of Surface Chemistry Characteristics ~ Jessica X. H. Wong and Hua-Zhong Yu


Going inside Colored Solutions: The Optical Microscope as a Tool for Studying the Chemistry of Hydrophilic and Hydrophobic Materials ~ Riam Abu-Much, Sobhi Basheer, Ahmad Basheer, and Muhamad Hugerat

The Molecular Boat: A Hands-On Experiment To Demonstrate the Forces Applied to Self-Assembled Monolayers at Interfaces ~ Charlene J. Chan and Khalid Salaita

JCE Always Contains Content That Will Make You Think

With 93 volumes of the Journal of Chemical Education to explore, you will always find something informative—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 a great time to submit a contribution to the Journal of Chemical Education. For some advice on becoming a Journal author, read Erica Jacobsen’s Commentary. In addition, numerous author resources are available on JCE’s ACS Web site, including: Author Guidelines, Document Templates, and Reference Guidelines. The Journal has recently issued a call for papers on Polymer Concepts across the Curriculum, so consider submitting a contribution to our next special issue.

I have no idea what the title is of the first Journal of Chemical Education article that I want to highlight this month. That’s because you haven’t written it yet.

JCE editor-in-chief Norb Pienta shares a call for papers for a special issue on “Polymer Concepts across the Curriculum,” with a submission deadline of October 24, 2016. Do you include polymer concepts and activities in your high school classroom? Have you given your own novel twist to previously shared polymer-themed demos or experiments? With the crush of content to cover in a given year, how have you made room for an “extra” topic like polymers? Or, have you gone all in and designed a high school course specifically dedicated to polymers? In her JCE 93.05 May 2016 Issue Highlights, Mary Saecker suggests writing an article as a summer project. In the last part of her post, she offers links to several resources useful to potential Journal authors. One of those is my commentary Become a Journal of Chemical Education Author (available to non-subscribers online) from several years ago. I outline obstacles you might encounter while preparing a submission, along with ways to overcome those obstacles. I’ll renew my particular encouragement to high school educators to submit to JCE. Consider polymers as one starting point.

Chemistry Throwdown

Reading the phrase “Role-Playing Game” in another article’s title brought to mind twenty-sided dice and Dungeons & Dragons. Further exploration into the article itself, Tournament of Young Chemists in Ukraine: Engaging Students in Chemistry through a Role-Playing Game-Style Competition (available to JCE subscribers), clarified the picture. The authors describe it in the context of science competitions and tournaments for middle school and high school students, with a long history of use in Russia and Ukraine. It starts with the release of open-ended problems well before the competition. They typically do not have a single solution, and some may not have a solution at all. Some examples from the article are:

Chronometer. Describe a construction of a chemical “stopwatch” that will work indefinitely and will produce a regular signal with a certain predefined time period.

Water Blanket. In the areas with hot and dry climate, the problem of water evaporation from the surface of open water reservoirs is very important. Suggest an environment-friendly and nontoxic composition and method of its deposition as an ultrathin layer on the water surface, which will prevent or decrease the loss of water due to evaporation.

Time Machine. How would you organize the production of the Aspirin pills in times of Julius Caesar?

The release kicks off a months-long period of intense preparation and research into possible solutions, using teamwork, literature searches, and discussions with science professionals. The tournament itself sounds like a chemistry throwdown, with solutions described during a presentation by a team’s Reporter, with questions taken from another team’s Opponent, with both of their performances evaluated by another team’s Reviewer. After discussion, the judges ask questions. Then it begins again, with another team sharing their solutions for critique and evaluation. The multiple skills brought together during such an endeavor are more than a competition—they are preparation for life after schooling, and not necessarily just those going into science fields. Researching a topic, developing creative solutions to an unexpected problem, working with a team, supporting your ideas, and presenting your work.

Intrigued? I was. The authors share a website with further information about the workings of the competition and sample solutions; it is currently only available in Russian and Ukrainian, but they also invite inquiries from those interested. I think it would be a sight to see, hopefully with young chemists rising to the challenge. For those who participate in other science competitions in the U.S., what do you think of this model?

The countdown has begun…6 full days and two exam days left. Summer is in sight! Exhale. Almost.

My school’s upper middle class student body is capable of more. Our new administrative team now strongly encourages all core content teachers to provide a summer assignment to prepare students for the first day of school. Outside of the summer reading for literature classes, we’ve never done this. I see the potential for class time-savings and improvement of student understanding. Will the students see the possibilities? What should I assign? Is it realistic to expect next year to begin differently?

The team of chemistry teachers met a few times, and we established a plan. It’s not too late to adjust! Do you have experience or advice?

Here is our current plan:

• All upcoming chemistry students will join a Schoology course, “Preparing for Chemistry: 2016-17.” The site will help us to track student access to the material. Do they wait until the night before school? Do only 15 of 400 students ever even join the course?
• Within the Schoology course, students will select their particular level of chemistry from a list of folders: on-level, honors, honors/AP combo, and AP chemistry. All students will have access to all preparation materials, however. Who knows? Someone may be planning to request a schedule change to move up a level, right?
• All of our first year students, on-level, honors, and honor/AP combo, will have similar summer assignments.
  
  • Units of Measurement: Students will watch my flipped classroom video tutorial addressing simple metric conversions and scientific notation and answer a five question online quiz. The required time commitment is 25:00 minutes.
    • We know this content has been taught in many previous science and math classes.
    • If students recognize a weakness requiring extra practice in this area, we have optional Khan Academy video links and our own worksheets with answer keys.
    • The online quiz will provide diagnostic data for teachers to use on day one of the new school year.
  • Density: Again, students will watch my video tutorial and answer a five question online quiz. The overall time commitment is just over 15 minutes.
    • Again, we know students have learned to calculate density. We are using this topic to force unit conversions, simple algebra, and critical reading of scientific word problems or data tables.
    • We will teach significant figures in class rather than as a part of the summer assignment. It seems too overwhelming. Thoughts?
    • Similar to the units of measurement lesson, students have access to tutorials and practice problems if they feel weak in the area.
    • Also, the online quiz may help teachers to diagnose possible algebra or problem-solving weaknesses early in the semester.
  • Dimensional Analysis: Rinse and repeat. Students will watch my video tutorial and answer a short online quiz. The overall time commitment is just over 15 minutes.
    • Our students learn to use dimensional analysis to convert units in ninth grade. This is another review for them.
    • Again, students will have access to additional tutorials and practice problems if they experience difficulty with dimensional analysis.
    • The online quiz asks learners to choose the appropriate conversion factor and determine the appropriate orientation of conversion factors. We hope to recognize common mistakes and correct them during the first week of the new semester.
  • Elements of the Periodic Table: Students will be asked to become familiar with common element names and symbols. We plan to use Quizlet to provide learning tools. No online quiz is required.
  • Honors/AP Combo Chemistry ONLY: Students will review simple graphing skills to prepare for graphing lab data.
    • Students will review graph titles, labeling each axis, and finding the line of best fit.
    • Students will use the R² value to choose the “best” straight line and review the slope intercept equation for the line.
    • Students will be encourage to learn to create and interpret simple graphs on their own calculators and in Excel.

What are we missing? Please share your wisdom. Do you “count” summer assignment grades? 

For my students and me, the AP Chemistry exam does not mark the end of the school year. Once the AP exam is over, my students are exhausted but our class continues to meet for three more weeks. Each year we complete a qualitative analysis lab, but this year we finished earlier than I anticipated. For the first time all year, I have the luxury of time. I decided to go back to one of the resources I wrote about previously - the International Chemistry Olympiad released exams. I have adapted some Laboratory Challenges from these previous exams. The first asks students to identify an unknown solid using a balloon and some string.

I recently stumbled across a blog about the use of BCA (Before Change After) tables for stoichiometry written by Lowell Thomson.  I was thrilled to discover ChemEd Xchange!  I wanted to share my journey, spurred on by my students, into the extensive use of the BCA approach in AP and IB chemistry.  I have attached some notes and the key for daily practice on how I apply the approach to titration curve calculations.  I have also included two videos to demonstrate the teaching method.  Note that I use the acronym BSA – Before Shift After – instead of BCA. 

I want to admit up front that BCA is a little more challenging on the front end in terms of student learning, especially for limiting reactant problems.  However, there is a huge win in terms of the amount of information and understanding obtained in the end.  When a colleague of mine (Daniel Haradem) decided to use them as well he came in and exclaimed that once he figured out the limiting and filled in the table all of the questions became trivial!  My students find that as well. 

A few compelling reasons to consider this method include the following.

(1) There is an improved understanding and determination of excess reactant remaining.  Students who are taught an algorithmic method to determine this have to rely on memorization to obtain the correct answer.  Sadly, most miss these questions at the AP level.

(2)  AP expects students to be able to draw or interpret particle diagrams showing all substances remaining in solution after a reaction has occurred.  Completion of a BCA table clearly shows ALL species present, including all products and the excess reactant remaining.   

(3) Smooth transition into equilibrium for common ion or acid base type questions.  This has been the biggest win for my class.  I believe the approach to titration curves has improved my students understanding of not only the quantitative aspects, but more importantly the qualitative aspects of acid base chemistry.

In terms of the difficulty with limiting reactants, I share three approaches with my students. The most accurate, but longest approach is to perform a quick stoichiometry problem from one reactant to another and compare the moles needed to the moles available.  For some reason, this is very challenging for some of my students.  If the mole ratio is simple, I encourage them to estimate this concept.  If students are not readily grasping either of these, I encourage them to guess – yes guess – the limiting reactant.  I have them fill in the chart for the reactants and if one of the answers is negative, they clearly guessed wrong.  A quick erase and re-calculation and they are back on track.  The video below shows an example of a limiting reactant problem that I worked for my 10^th grade pre-AP students.  Ensuring they have their mole ratio correctly can be a slight problem so I teach that it is to/from or that the limiting reactant coefficient is in the denominator. 

If all dilutions are accounted for, molarity can be used in a BCA table instead of moles.  For my AP & IB students I call this approach “DSE” for “Doc Saves Everyone”.  We use this as a checklist for all equilibrium.  The “D” stands for “dilution”.  The first question we ask is “did we add volume to volume?”  If the answer is yes we perform the appropriate dilutions.  I find that performing dilutions right away helps avoid loss of points from failure to divide by the total volume at the end.  The “S” stands for “stoichiometry”.  Do we have (1) strong acid/base (2) soluble salt or (3) an acid base neutralization?  The results of the dilution provide us with initial molarity values for our stoichiometry problem.  Finally, the “E” stands for “equilibrium”.  The results of the stoichiometry feed into the initial molarity for our equilibrium calculation.  The next video shows me working a point on the titration curve for my AP & IB students.  Of course there are shorter ways to do this particular point, but I like to show my students that this method will always provide a framework and valuable information along the way. I don’t introduce short-cuts that may by-pass understanding until students grasp the overall concept.  I welcome comments and ways to improve my students’ learning!

Chemistry education faculty at Stony Brook and Carnegie Mellon University want to help AP chemistry teachers adapt to the new AP curriculum, and will create a new website to help support teacher needs: the APChemCollaborative (APCC). Could you please take a moment and help us understand you and your needs better, so we can create a successful design? This survey should only take 5 minutes to complete.

CLICK HERE TO COMPLETE THE SHORT SURVEY

Thank you for your help!

What am I doing to help kids achieve?

How do I know when they are there?

What is the evidence?

  This Saturday there was a teacher's day at the Regional ACS meeting in Kentucky. It is tough showing up on a Saturday in May. It was worth the trip. There were wonderful workshops just for teachers on incorporating green labs, POGIL, Food Chemistry, Climate Change and a great lunch. As with most conferences, even the small ones, there is way more than I could put in one blog. Here is what impressed me the most. Several people from the national and local ACS made a point of doing whatever they could to reach out to teachers. As Dr. George Bodner said (and I am paraphrasing), the ACS first looked at what they could do to teachers. They then examined what they could to for teachers. Now they are asking, "How can we work WITH teachers."

  The answer is the American Association of Chemistry Teachers. Resources, webinars, publications, videos and simulations are growing on their site at a rapid pace. They have also received funding from many public foundations. The yearly cost is $50. Granted, on a teachers salary with a mortgage and kids to support, for some that is still a chunk of change. Ask your principal, PTA, department or, better yet, your local ACS if they will help spot you the dues. The worst thing that can happen is that they will say no. However, if you show them that it is the best professional development that you can get for $50, someone just might say yes. It cannot hurt to ask. The summer time is the perfect time to check out the site and try to work on that lab or demonstration that you always wanted to improve. Somehow, I am going to try to come up with the cash to sign up. Chemistry teachers rarely have a dedicated group who says, "Hey we like you and want to try to make your life and your student's lives a little easier and better." Can't hurt to give them a shot...

  Also, want to give a shout out to two fantastic ladies...Lynn Hogue and Linda Ford of the Cincinnati local ACS group who helped put the day together. I am sincerely grateful and I know my students will benefit from the great day you put together. Thanks again.

This past week, as part of our Thermochemistry unit, my students were completing one of my favorite Target Inquiry Labs entitled “ A Very Cool Investigation”.  We were using calorimeters, dissolving ammonium nitrate, and my students were recording the change in temperature using a digital thermometer.  Some of my students had noticed that with similar amounts of ammonium nitrate, some of the changes in temperature happened quickly while some of them happened much slower. I had noticed that some of the students added the salt slowly while others just dumped it in and some students stirred slowly while others were much more vigorous as if it was a contest to see who could get the lowest temperature based on how vigorously they stirred their solution.  However, with the digital thermometers, it would require a stopwatch to measure such a difference. Some students used their phone as a stopwatch but again it was mostly between a select group of students who saw this so called lowest possible temperature as fast as possible as a contest. 

           When my next class came in I asked one of the lab groups if they would like to test these different variables during their three trials. I had obtained a new wireless Temperature Sensor from PASCO and saw this as the perfect time to introduce it to my students. The sensor easily connected to the student’s iPad via Bluetooth after I had downloaded the free SPARKvue app. With a few directions, the students enjoyed the opportunity to let the sensor collect the data and then from the graph obtained on the iPad they were easily able to read the change in temperature. The added benefit of using the temperature sensor was that the graph included time. I decided to repeat this with several other lab groups since number one, I saw my other students become very curious in the new piece of equipment. Number two, I was able to save the data, then download for the next days lecture to initiate discussion. I knew I was going to use the infographic from Compound Chemistry regarding making chemical reactions happen faster and now with the use of the graph we had some data regarding an increase of concentration to back up our findings from lab, which led to a great introduction and discussion.  The temperature sensor was super easy to use and I hope to add more to get a class set. They sell for $39.00/each and require coin cell batteries. I also recommend checking out the other great wireless products from PASCO.

To update my previous blog, Classkick is becoming available on Chromebooks, Desktops, and Laptops very soon.  Click above to join the waiting list and get notified when this becomes available.

Thanks to Wendy Czerwinski for passing on to me the App: High School Chemistry: Practice Tests and Flashcards by Varsity Tutors.  The app is free and is worth passing on to your students or even using yourself if you are looking for question ideas. Topics include: Acid Base Chemistry, Titrations, Chemical Reactions, Equilibrium, Types of Reactions, Electrochemistry, Elements and Compounds, Compounds and Bonding, Elements and Atoms, Kinetics, Measurements, Units, Nuclear Chemistry, Phases of Matter, Gases and Gas Laws, Phase Diagrams, Solutions and Mixtures, Stoichiometry, The Periodic Table, and Thermochemistry and Energentics.  The app allows you to make flashcards by typing, use of a photo, or by audio dictation.  The app is compatible with iPhones, iPads, and the iPod Touch using iOS 7.0 or later.  

chem_tutor.jpg

I met Jenelle Ball in Denver, CO at the Spring 2015 National ACS meeting. She is soft spoken and easy to get to know quickly. Jenelle’s biographical information is impressive. She earned a BS and MS in chemistry. While in graduate school, she recognized a passion for the process of teaching and learning which led her to teach high school chemistry. Most of her career has been spent at Chico Senior High School in Chico, CA. She was also fortunate to have the opportunity to take a rare sabbatical from high school teaching and earn a MA degree in teaching and learning.

Jenelle has published many articles in the Journal of Chemical Education and is active in her local ACS section. She is a leader within her school district and in the wider chemistry education community. Jenelle received several other awards before being awarded the James Bryant Conant Award for excellence teaching high school chemistry in 2015. Even though she has taught for 30 years, she feels refreshed and inspired by this honor and has no immediate plans to change directions and leave her students behind. Chico Senior High students are lucky indeed.

You can read the Journal of Chemical Education commentary, Endowing Inspiration, co-authored by Jenelle and myself and also view a video interview recorded just two days before Jenelle was officially presented the 2015 Conant award.  

Find out more about past and present Conant Award recipients.

Have you ever seen experiments, such as the one here, that makes use of air pressure to crush a metal can? Such "can crush" demonstrations can be presented as a neat trick that you can do for your students. See the video below.

What do you suppose is the secret behind this trick? Hint: It has to do with chemistry!

Let me know your thoughts on how you think this experiment is done. I'll post the solution in about a week. 

What Is A Big Idea?

“Big Ideas” are statements of the main principles on which the curriculum is focused. Having a theme anchor the curriculum helps students make connections within the chemistry content and among other content areas. The concept of organizing science and chemistry content into “big ideas” has been a focus of several recent initiatives. AP chemistry (fig. 1) teachers have used "big ideas" for several years now. Similarly, the Next Generation Science Standards (fig. 2) that will be implemented within the next few years in many states also uses "big ideas". The Next Generation Science Standards separate science topics into physical, life and earth/space sciences. So, the big ideas under Physical Science allow teachers to make connections between chemistry and physics content. This stands in sharp contrast to the division of content that veteran teachers are accustom. A wealth of professional development activities offer to guide teachers toward using these “big ideas”.

Fig. 1. The AP Chemistry Curriculum is organized with six Big Ideas. Taken from the AP Chemistry Course Overview http://media.collegeboard.com/digitalServices/pdf/ap/ap-chemistry-course-and-exam-description.pdf

Fig. 2. The Next Generation Science Standards are divided into three categories: Physical Science, Life Science and Earth & Space Science. Each of these categories are further organized into several Big Ideas. Most traditional chemistry content can be found under the Physical Science category. http://www.nextgenscience.org/overview-topics

Call for Contributions

Chemical Education Xchange (ChemEd X) is interested in learning about the progress teachers have made, experiences that teachers have had, areas that are causing difficulty and more as they transition to this new organization. For this reason, we are initiating our first content specific Call for Contributions centered around the concept of “Big Ideas and Making Connections”.

Accepting contributions through July 18, 2016.

The deadline for making a contribution to this call is Monday, July 18, 2016. Authors are encouraged to read the ChemEd X Contribution Guidelines before creating their contribution.

Some examples of items that you might contribute:

• Have you used a resource that you would recommend that may help others work with Big Ideas? You might contribute a PICK review type manuscript. The PICK manuscript type is generally one to three paragraphs in length.
• Share your ideas in a Blog post. For the purpose of this Call, the minimum length of a Blog post should be four paragraphs. Blogs are edited by ChemEd X editorial staff, but might not be peer reviewed. Some items you might blog about include, but are not limited to:
  • Share your experience with the Big Ideas defined in the restructured AP chemistry curriculum, Next Generation Science Standards or your own state/district.
  • Explain how you organize/use Big Ideas in the chemistry curriculum.
  • Share the Big Ideas you use within a specific unit or throughout the entire course.
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In Chemical Mystery #6, I used chemistry to crush a metal can. To do so, concentrated sodium hydroxide solution (about 35% NaOH by weight) was added to a can that was almost completely filled with carbon dioxide gas. The can was then sealed. The carbon dioxide gas in the can reacted with the added sodium hydroxide:

2 NaOH(aq) + CO₂(g) --> Na₂CO₃(aq) + H₂O(l)        Equation 1

This chemical reaction removed the gas from the can. Of course this lowered the gas pressure inside the can. Once the pressure inside the can became low enough, the surrounding air pressure was able to push on the can, causing it to implode. The same effect was not observed in a can simply filled with air, because air contains very little carbon dioxide. The video below shows one way you can carry out this experiment.

So that’s how you can crush a can using chemistry, and also present a neat chemical trick! 

Congratulations to Andres Tretiakov and Bob Worley who both figured out how this experiment works. Bob likes to use plastic soda pop bottles as a less expensive alternative for this experiment, but I happen to think it’s a bit more impressive to use metal cans. For those interested, Flinn Scientific has published a procedure on how to carry out this experiment using plastic bottles¹.

There are a surprising number of concepts that can be taught while using this demonstration. Certainly one can discuss the gas laws and composition of the atmosphere when using this demonstration. Students could be challenged to identify reactions that might allow one to crush a can filled with air. This demonstration can also provide a reference point for one way chemistry is being used to combat climate change: sodium hydroxide, though application of Equation 1, is used as a reagent to remove carbon dioxide from the atmosphere^2-4. Finally, this experiment provides an example of a spontaneous reaction for which both the enthalpy and entropy changes are negative. Although I didn’t mention it in the video, the can becomes quite warm as a result of the reaction (negative enthalpy )and a gas is consumed (negative entropy). 

Are there any other concepts you think might relate to this particular experiment? I'd love to hear your thoughts in the comments below.

References:
1.    https://www.flinnsci.com/media/621027/91423.pdf
2.    http://scholar.harvard.edu/files/davidkeith/files/97.stolaroff.aircaptur...
3.    http://wordpress.ei.columbia.edu/lenfest/files/2012/11/ZEMAN_LACKNER_200...
4.    http://www.popsci.com/molika-ashford/article/2008-10/better-co2-scrubber

Today is my last full day of school for this academic year. I taught our school’s 1-semester Organic Chemistry course again this year and have been looking back on how I taught resonance. During our review since last week, resonance was labeled as one of the most tricky concepts (along with electron pushing in my opinion), despite lots of practice and instruction. My teaching sequence consists of defining and providing examples of conjugation (after learning about hybridization), delocalized electrons, and finally pushing electrons if conjugation exists. I remember from teaching at the college level that resonance was also a tricky topic for many undergraduates.

My question to you is this: If/when teaching organic chemistry, how do you present resonance for suitable comprehension and understanding?