What effect does a different starch have on gluten-free bread? Time to test that. GFB#03 will use potato starch in place of the tapioca starch of GFB#01 and GFB#02. Since the method used for GFB#01 has already been determined to be a little lacking, I’ll be following the GFB#02 procedure… I mean recipe.

Ingredients:

3/4 cup brown rice flour

3/4 cup potato starch

1/3 cup ground flaxseed meal

1 teaspoon xanthan gum

1 teaspoon dry yeast

1/2 tablespoon sugar

1/2 teaspoon salt

1 cup 110F water

All dry ingredients were combined in the bowl of a stand mixer with the paddle mixer. {This is a change from GFB#02 which used a dough hook. Since I’m not really developing a gluten network by kneading, the dough hook isn’t really doing anything other than mixing which the paddle does better.} The dry ingredients were mixed for ~1 minute, then the water was added. The dough was mixed for 1-2 minutes, then the bowl was scraped down and the dough was mixed for another 1-2 minutes. The dough was transferred directly into a loaf pan {another slight deviation from GFB#02} and allowed to rise for ~1 hour. The risen loaf was put in a preheated 400F oven. For ~40 minutes until the internal temperature was 200F. Turned out onto a wire rack to cool.

Evaluation:

Similar to GFB#02. The loaf didn’t rise quite as much (but not significantly different) and the finished loaf looks virtually identical. The crumb is definitely less sticky/gummy than GFB#02, and I don’t think I get the same aftertaste as with previous loaves, there’s a much cleaner finish to the flavor. The crust is the same.Image

Revisions in the next iteration:

I think the flaxseed meal is making the loaf more dense and moist and causing some of the texture issues I’m trying to fix. I used it because I happened to have most of a bag in the freezer and wanted to use some of it up. I think I’ll try a batch without the flaxseed meal. To replace some of the body that the flaxseed meal provides, I think I’ll bump up the rice flour a bit. I’m pretty sure that I’m going to have to add some other ingredients to the ultimate “best” loaf… from a number of the recipes I’ve found online, it looks like egg, oil, baking powder and buttermilk might be necessary to both improve the texture of the finished loaf and round out the flavor.

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As another class ends, I am once again faced with assigning grades. {Notice, I say “assigning” grades, not “giving” grades.} In every class there are students who work very hard, and are really pushing to the limits of their abilities, but don’t achieve scores that result in the grades they want. In some cases, they will make the case “But I worked really hard, that should count for something!”, and in many of those cases I really want to agree with them. If a student is really putting forth a complete and honest effort in my class, there’s a part of me that wants to massage the grade cutoffs so the student gets at least that magical “C” that will allow him or her to move along and not have to repeat the course.

Naturally, this internal debate is different for different courses. If I’m teaching a general education course (basic science, environmental science, etc) whose goal is simply to engage the students in a constructive, and sometimes foreign, thought process that will make them more informed citizens, then giving some recognition just for effort is appropriate. Then comes the “real” course that I teach, General Chemistry. Gen Chem is the entry point for a number of science majors, and although it certainly has some of the same outcomes as a gen ed course, it also should have a very specific minimal skill set that should be expected/required to pass the class. Hard work and effort, while admirable, shouldn’t really count for anything without results in a foundational course like Gen Chem. That’s not to say that no one should pass Gen Chem without mastering every subtle detail of equilibrium or redox chemistry. If a student is finishing up Gen Chem II, I think it’s reasonable to expect that he or she can do a few things almost flawlessly, my brainstorming list might be…

write a chemical formula
calculate a formula mass/molecular weight
convert between grams and moles
understand why it’s important to convert between grams and moles
write a balanced chemical equation
understand the idea of a limiting reagent/reactant
calculate theoretical yield
understand solutions and concentration units/calculations

Ideally, there should be more things on that list, but I’m trying to limit it to the absolutely essential minimum skills that a student would need to continue in science classes. Another spin on that is, what would be embarrassing for students not to know when they walked in to the first day of Organic Chemistry? If the Organic instructor came to me and said that none of my former students could calculate a molar mass, then what was the point of them spending a year in my Gen Chem class?

I have toyed with the idea of using this concept in my Gen Chem II final exam. The first question would be a “qualifying” or “scaling” question that addresses the minimal fundamental knowledge they should have to pass Gen Chem. If they can’t answer that question, they don’t pass the course. That’s pretty harsh, but I’m not thoroughly convinced that it’s unreasonable. To soften it a bit, I’ve considered the “scaling” option – their performance on that first 10pt or 20pt question would be used as a multiplier for their score on the rest of the final exam. Only get 15/20 on the scaling question? Then your final exam score is multiplied by 0.75. Again, maybe that’s harsh, but I’m not sure it’s unreasonable. One argument against this is that it over-rewards the good students (who will on average have a higher multiplier) and over-penalizes the poor students, although that also serves to spread the students’ scores out a little more, making it easier to set grade cutoffs. This would be in some ways similar to the adaptive testing algorithms used for some online standardized tests, so it would seem to pass some minimal pedagogical scrutiny…

I guess the reason I’m pondering this right now (as I do at the end of every semester) is that Gen Chem has the reputation of being a “weeder class”. That makes me the person who either has to: a) lower the standards of my grade assignments to pass students along up the chain; or b) be the person who destroys the hopes and dreams of dozens of optimistic young students who think they will be doctors or dentists or physical therapist. Going with option “a” doesn’t make me feel good about the future, but going with option “b” doesn’t make me feel good about the present. It looks like there’s a rock, and there’s a hard place, and I appear to be nestling right there in between them.

 

As the last week of my summer Gen Chem class is about to begin, I was thinking about just how fast this class flies by and started looking at some actual numbers. It’s a little shocking. My summer Gen Chem class is 5 weeks long with a total of 31 calendar days from the beginning of the first class period to the beginning of the final exam. That’s

31 x 24 x 60 = 44640minutes.

Sounds like a lot. During that time, we have 18 class periods that are each 130minutes long for a total of 2340minutes. For the 31 days that students are in my class, they spend just over 5% of all their time in class. {By the way, so do I!} The hardest part of the summer class schedule is that there’s not a lot of time to absorb/process the information from class. If we use the oft-cited “2 hours of homework/studying for every hour of class time” guideline, then a student should spend 5000-6000minutes studying during this class. If we also budget 7 hours of sleep per night, that’s around 13000minutes of sleep. And there’s probably an hour a day spent on assorted hygiene activities. Checking the running budget:

Minutes available:

44640

In class

-2340

Study time

-5500

Sleep

-13000

Hygiene

-2000

Balance:

21800

That balance works out to just under 12 hours per day during the 31 calendar days of the class. That doesn’t sound too bad unless we consider that students might be taking another class, or might have to work, or might have family obligations.

Although this side of the analysis might look a little bleak, everyone knows that a 5-week summer class is going to be pretty intense for a student. What about the other side? This is a foundational course for a variety of science majors, so there are a certain set of topics that have to be addressed in the course. I can’t just decide to drop a couple topics because I don’t feel like taking the time for them. It wouldn’t do my students any good to be GREAT at kinetics but have no clue how to approach an equilibrium or vice versa, so how does that budget work out? I have 2340minutes of class time. I give 4 exams that are ~65minutes each in the summer class, that’s 260minutes gone. Each class period is 130minutes; expecting the students (and me!) to stay on-task for 130 minutes is a little ambitious, so I typically plan for a 5-minute break during each of the 18 classes, that’s 90 minutes, and brings the available class time down to just under 2000minutes. I like to have the students do some group work on problems during class every day, let’s assume a 70% “my time” to 30% “group work” split. That means I have 1400minutes to do everything I need to do in the class.

There are 10 topics to cover in my Gen Chem II class:

1) States of matter (properties, heating/cooling curves, phase diagrams, heat capacity, enthalpy of phase change);

2) Solutions (concentration units, colligative properties);

3) Gas Laws;

4) Kinetics (Rates, rate laws, mechanisms);

5) Equilibrium (including Ksp);

6) Acids and Bases (definitions, strength, Ka/Kb);

7) Titrations and Buffers;

8) Thermodynamics (entropy, Gibb’s Free Energy, fuels, coupled system);

9) Redox Chemistry (oxidation number, balancing redox, voltaic cells);

10) Nuclear Chemistry (isotopes, radiation, balancing rxns, half-life)

OK, I made that into 10 so the math was easier… some of those topics are a bit more expansive than others, but they all have some significant content. 2000minutes, 10 topics, 200 minutes per topic. Equilibrium in 200 minutes. Kinetics in 200minutes. How many minutes is the Arrhenius equation worth? So yes, the summer class is intense. It’s intense for the students and it’s intense for the instructor. And in 4 days, it will all be over for another year.

Studying chemistry should not be a game of Trivial Pursuit. I have said any number of times in my classes that I don’t think my students should devote a whole lot of mental capacity to memorizing long lists of equations and formulas and constants, and I believe that is absolutely true. Then I disturbing epiphany. I expect students to memorize a select list of polyatomic ions. And I expect them to memorize certain fundamental properties of water (boiling point, melting point, density). And metric conversions and fundamental relationships. So as I nestle into the saddle of my high horse and look down on instructors who try to turn chemistry (or any field) into a game of Trivial Pursuit, I have to wonder just where I personally draw the line between what must be memorized and what should be looked up.

Students should “memorize” things that they use often. In a sense, they aren’t deliberately memorizing these things, but after looking them up often enough, they just sink in. I never consciously decided to memorize the atomic mass of nitrogen, but after looking up the value, writing it down, and plugging it into a calculator a few thousand times, I “memorized” that nitrogen is 14.007g/mol. The things that I expect students to “memorize” are the things that I would hope they either have enough experience with before starting my class, or things that they should get enough exposure to if they are studying effectively for my class. By the time a student is in Gen Chem II, that student should have seen and written nitrate and carbonate and sulfate enough times that they should be second nature. Similarly, dancing the decimal point through metric conversions should be as automatic as breathing.

How many problems does a person have to do for these things to really sink in, and is that number a reasonable expectation for a college student? Students will believe that it takes 10,000 hours of practice to become a good pianist or golfer, but they often think it’s crazy to spend 50 hours becoming proficient chemists. That’s 3-4 hours per week for a typical 15-week semester. If a student is taking a typical 15 credit load and spending 3-4 hours per week on each 3-credit class, that works out to 30-40 hours of class and study time per week. Reasonable? I would hope so. I know, there’s more to a student’s life than just going to class and studying, but if a student spends (on average) 6 hours per day in class or studying and 8 hours per day sleeping, that leaves 10 hours for work and personal time. {Uh-oh, this is starting to build up to a “kids these days!” rant, I’m going to stop before it builds momentum and completely changes the topic of this post.}

One way that some faculty walk this line is to allow the students to bring some sort of notes to the exam, a Periodic Table they can use as a “cheat sheet”. I’ve done this a couple times in upper-level classes, but I’m really not a fan. It seems like more of a contest between me and the students… can they guess the specific bit of trivia I’m going to put on the exam and put it on their cheat sheet? For my upper-level classes, the type of questions I ask aren’t really things that can be jotted down on a cheat sheet, they’re more descriptive and conceptual. At the same time, I don’t want my students to study by rote memorization, so as a compromise, the front page of their Gen Chem exams are all a formula and constant sheet that is the same for all students. {For example, http://www.drbodwin.com/teaching/exams/c210oe1a.pdf } No one has an advantage, no one has to worry about forgetting their cheat sheet, it seems like a good approach. It’s also similar to the approach used by standardized exams such as ACS exams, so I feel fairly confident that it’s a sound method.

One final point may seem to be a little off-topic, but I think it’s part of the same question/phenomenon, although it may be a bit of the grumpy-old-man rant. Some students have become a bit too reliant upon web searches, which makes them even less likely to devote time to properly studying. Anecdotally, I have had students in lab use a google search to do conversions. If they’re converting calories to joules or some other more exotic unit conversion, I’m thrilled to see their initiative, but in more than one case, I’ve had students use a web search conversion program to convert milliliters to liters or grams to milligrams. When I point out that this seems like an exceedingly trivial unit conversion that they should be able to do without the internet, some have pointed out that if the computer is available they might as well use it. On one hand, I agree. On the other, this is a screaming indication that these students are not engaging any higher-level thinking skills beyond the ability to type terms into a search engine. And in too many cases, they aren’t very good at picking good keywords to perform their search, again demonstrating that they’re not really engaging in constructive thought and critical thinking. {Wow, I crammed a disgusting number of pedagogy buzzwords in those last few sentences…}

The point here is that although an endless list of terms and equations for students to memorize doesn’t seem like a great way to approach chemistry (or any other subject), there’s got to be some minimal basic knowledge that we should be able to expect students to either memorize or know by repeated use. The key word there is “repeated”, as with all endeavors, practice, practice, practice.

A local news station called today and said they had a mysterious substance that they’d like some help identifying.  After a recent rain, a woman found some of this material on her patio.  It’s clear, colorless, “squishy” and doesn’t burn.  {Yeah, “squishy” might not be a super sciencey word, but it puts the right idea in your head.}  She was wondering if it came from the sky during the rain.  The news people brought a sample to campus and first ran into a biologist who confirmed that it wasn’t biological.  {An early guess over the phone was maybe snail eggs.}  Enter the chemists!

Mystery goo from the sky

Mystery goo sample in a glass vial

The gelatinous solid had no odor, and because I was quite confident that it wasn’t exceptionally hazardous, I picked up a piece.  It wasn’t oily, just wet and gooey.  No notable residue was left behind on my hand.  I was sorely tempted to taste it, but I didn’t.  I guessed that it was a hydrogel of some sort.  The reporter mentioned a garden and some potted plants, so I thought it must be a soil additive used for moisture retention.  {Similar to http://www.plantgel.com/}  I asked for a small sample to further analyze, my intention was  to put it in a vacuum dessicator overnight to dry it out and then maybe run a quick FTIR.

Before I put it in the dessicator, I thought I’d give in a wash with acetone.  After a few moments, the “goo” became slightly opaque and it began to shrink.  The acetone was pulling the water out of it quite nicely, so I left it to stir.  After about 20 minutes, it was pretty dehydrateded.

Mystery goo dehydrated

Acetone removed the water from the Mystery Goo, shrinking it and making it opaque.

I left it gently stirring overnight, I’ll finish the analysis tomorrow.

{According to the MSDS at http://www.plantgel.com/, their product is a polyacrylamide copolymer.  FTIR tomorrow should confirm.}