Thursday, March 1, 2018

International Cooking with Chemistry #2 - Bananas Foster

After reading Chemistry in Your Kitchen by Matthew Hartings this summer I decided to see if my International Baccalaureate students would be willing to have my learn how to cook a dish with their families.  Periodically my students will have a potluck during their core days where they miss their classes all day working on external assignments and there tends to be a wide variety of international cooking on display.  
In December of 2017 (ugly Christmas sweater day to be precise) I got to do a great dish to connect with chemistry; Bananas Foster (thank you Flanigans!).  Bananas Foster originated in Louisiana.  It is made by mixing butter and brown sugar on low heat before adding bananas and dark rum.  The rum is then ignited after briefly being heated.  Interestingly the alcohol in the rum does not completely burn.2  I had yet to ever cook using the flambe technique and this is a very approachable dish.  It also has a lot of experimentation to try.  The first thing I noticed when eating is that there is a substantial amount of dark rum flavor left after burning.  So I am in the process of now experimenting with what different alcohols taste like.  Thus far I have tried making Bananas Foster with gin and it tasted good.  Not only did I think so but my expert neighbor from the South confirmed.  I will later try it with vodka and maybe a clear rum as well.  I did not notice any difference with the flame although I would love to see if a distinction could be made using higher level equipment.    
Later in the year our IB Chemistry HL 2 class did the internal assessment where every students constructs their own personal chemistry experiment, does the experiment and writes a formal report to be submitted to IB as part of their grade.  One student did an experiment where they compared heating vodka with lighting vodka on fire to see how much alcohol remained for each.  The results showed that heating was more effective than igniting the alcohol although more results would have improved the certainty of that result.  
Figure 1:  Brown sugar and butter are mixed under low heat


Figure 2:  Stir the butter and brown sugar thoroughly (ugly Christmas sweater optional)


Figure 3:  Add in the bananas before adding the liquor and ignition.


Figure 4:  The finished product that I made using gin in place the dark rum





#1 - Paneer

#2 - Bananas Foster
#3 - ???
Sources -
2. Hanson, Christine E.; Kwasniewski, Mishi T.; Sacks, Gavin L; Decoupling the effects of heating and flaming on chemical and sensory changes during flambe cooking International Journal of Gastronomy and Food Science V. 1 (2) June 2012 p.90-95 https://www.sciencedirect.com/science/article/pii/S1878450X13000024

Saturday, February 3, 2018

International Cooking With Chemistry 3 - IB Group IV Project

IB students were tasked with creating an experiment or set of experiments that analyzed international foods from different scientific perspectives (usually biology and chemistry).  Students used a variety of experimental methods utilizing creativity in their methods.  Pop Rocks (Spain) were dissolved in a hydroxide solution and then titrated to measure the amount of carbon dioxide present (Figure 14).  Another group tested the various components of Bakkalava to determine which had the biggest impact on the boiling point of the mixture (Figure 1).  One group tested how to make the perfect macaron (Figure 4, Figure 5).  They detailed the mechanism by which potassium bitartrate influences the protein structures and how this affects the texture and height.  Students used tea to investigate caffeine and tannin amounts, then connected these experiments with biology by examining heart rate after consumption (Figure 6).  
Students testing dough and yeast (Figure 7) found great data showing how yeast affected the rise of the dough (Figure 8).  Students gathered some brave volunteers to test which foods (Figure 13) reduced the affects of capsacain in spicy foods (peanut butter was typically the best). Students made Fraisier (French strawberry cake) with varying amounts of baking soda (Figure 9).  Students tested textures of various foods after a variety of experiments to simulate cooking (Figure 2, Figure 3, Figure 10).  And even though students researched ice cream and gelato (Figure 11, Figure 12) we still spent the next day making candy canes (Figures 15-17).  During our candy making one group even added in citric acid and ended up with sour gummy candy that was delicious.  


Figure 1:  Chemistry and Biology of Bakkalava
Figure 2:  Chemistry and Biology of kibbeh
Figure 3:  Chemistry and Biology of noodles
Figure 4: Chemistry and Biology of macarons
Figure 5:  Protein denaturing, air bubbles and cream of tartar for the perfect macaron
Figure 6:  Chemistry and Biology of Tea
Figure 7:  Chemistry and Biology of yeast and dough
Figure 8:  Great correlation between dough rising and increasing quantities of yeast
Figure 9:  Chemistry and Biology of Fraisier
Figure 10:  Chemistry and Biology of seviche
Figure 11:  Chemistry and Biology of Ice Cream
Figure 12:  Anthocyanins, skatole, alginate stabilizers and other relevants structures for ice cream
Figure 13:  Chemistry and Biology of spicy



Figure 14:  Chemistry and Biology of Pop Rocks
Figure 15:  A batch of candy cane mix now ready to shape and color
Figure 16:  Shaping the mixture into candy canes

Figure 17:  More candy canes being made


Sunday, January 21, 2018

Do people with lighter skin have different sunscreen needs?


We spent a class period researching in groups and a class period discussing our findings.  The prompt was to construct an argument that skin color matters for sunscreen use and an argument that skin color does not matter.  From there our groups diverged greatly as they built up arguments and pertinent explanations.  
Figure 1:  Whiteboard 1 explores the mechanism by which UV light causes DNA mutations


The wide variety of information in the various whiteboards led to some great discussion on content as well as generic science.  We discussed if knowing the mechanism of DNA damage by UV light is relevant so long as we see the data in Whiteboard 2 (below).  Students split but offered mostly arguments that mechanism knowledge is highly relevant to evaluate the conclusions from the data of skin cancer rates.  Multiple examples were offered such as some races might be located where they experience different exposure to sunlight, different races might also use different amounts of sunscreen on average and reporting of race can be inconsistent.  In general most students felt that just knowing skin cancer rates is insufficient and could be correlation without causation.  
We also talked about the mechanism by which UV light originates and under what conditions an electron can accelerate so much that it produces such high frequency light.  We connected the emission and absorption of light with the Balmer series for hydrogen.  We reviewed the spacing of energy levels and I instructed about the differences in energy level spacings for gaseous atoms/ions compared to molecular excitations.  We connected this later with Whiteboard 6 by talking about how a slight adjustment to a molecule can cause a minor change in the frequencies of light absorbed and how pigments and dye research often utilizes electron rich and electron deficient functional groups to shift color.   
Figure 2:  Whiteboard 2 found cancer rates based on race

Figure 3:  Whiteboard 3 went full “Natural News” to locate some arguments against
sunscreen



This board led to a good discussion on sources of scientific information, how sources manipulate data and experiment into “clickbait” articles.  We posed the question “Are any of these things actually bad or do they just sound bad?”  For example, if sunscreen ingredients are present in breastmilk, is that bad or is it so infrequent and low in concentration that it is irrelevant?  We talked about how the FDA does not have jurisdiction over supplements and how labels for supplements are sometimes shown to be incorrect.  We also compared this board to the risks of not wearing sunscreen using Whiteboard 2 (above).  
Figure 4:  Whiteboard 4 summarized different wavelengths of UV light and nanoparticles
used for sunscreens

Figure 5:  Whiteboard 5 looks at melanin and interactions of sunscreens with UV light

Figure 6:  Whiteboard 6 looks at different chemical structures utilized in sunscreens


Conclusions that students made included that the SPF data they saw suggested that anything over SPF 50 was a marketing scam and was less healthy than using SPF 50 or lower.  We concluded that the mechanisms by which electrons change motion during electronic transitions in molecules are incredibly difficult to visualize and that this uncertainty can be problematic for understanding.  We concluded that everyone exposed to sun should wear sunscreen because melanin mostly protects from sunburn but not from DNA damage.  We saw a variety of organic molecules used to absorb UV light as well as alternatives such as ZnO nanoparticles.  We started our discussion by looking at how 11 cis-retinal converts into 11 trans-retinal when absorbing visible light and this is the mechanism by which our brain becomes aware of light hitting our retinas.  We talked about the breaking of the pi bond before the rotation occurs and later compared this to potential changes in molecular structure when UV light is absorbed by molecules in sunscreen.  
As a teaching lesson I was highly pleased with the variety of topics to discuss and the variety of information students used to make arguments.  Students looked at chemical structures, DNA damage mechanisms, skin cancer data, sunburn data and how UV light itself varies.  We identified what type of light escapes the sun as a subject that requires more research.  We will continue to use this topic throughout our review.  We saw connections to organic chemistry, quantum chemistry, periodic trends and bonding.  It was interesting to the majority of students.  Some students asked what it was like to be sunburned because they had never experienced it before and most students had limited ideas coming into the discussion but left with much better knowledge.  

Sunday, January 14, 2018

The Staff Meeting I Dread - Student Course Selections


A few years ago I had a student take the advanced chemistry class I was teaching.  They did not do well on the first few exams we took and eventually I checked over how they had done in chemistry.  Lo and behold their grade was quite low.  Now when I recruit for IB chemistry or AP chemistry I make it a point to tell the students first that if they did not do well in chemistry that they should take AP chemistry or IB chemistry.  Why go to college and struggle through the material alone when you can work through it with a high school teacher that is likely to be far superior at teaching and where you will move much slower through the material with a lot more assistance?  When I lead with this I often hear a few students laugh as I start the comment before quickly realizing the validity of my perspective.   
So you would think that the first thing that I would have done would have been to talk to the student about their struggles and their ambitions and goals of taking the class.  But this year I had an overwhelming amount of struggle going on from my students and myself teaching new classes.  So instead I deflected and would just get frustrated every time I had to grade another round of tests that had a demoralizing amount of wrong answers.  Then at the end of the year I was talking to the student about college plans.

Me “What are you doing next year for school?”
Students “I’m not sure”
Me “Do you want some advice”
Student “Yeah, well the thing is, I just really love chemistry so much.  It’s my favorite subject, but I’m so bad at it.  I want to major in it, but I don’t know what to do.”

Had my frustrations with their lack of success influenced how I taught this student?  If I had had a better perspective would that student not have those doubts?  I could have taught them better than I did but now they got to carry all of the weight of my decisions.  I was really disappointed in myself because even though I tell students that struggling students should take these classes I had never considered that a student could struggle and love the course.  What had happened to my idealism?  I love chemistry and I don’t love it because of how well I can do problems in it.  I love taking the best results and conclusions from the smartest people throughout history.  I love connecting the macroscopic level with models in the microscopic level so that students can understand what is happening.  Teaching and learning chemistry is my passion and I had missed a chance to share that with someone seeking just that.  
Every year there will be a staff meeting for our department where we talk about scheduling.  I dread this meeting.  Teachers somehow are systemically driven to develop philosophies that only student X belongs in a class and students that do not accomplish Y prior to the class are failures unworthy of learning that content.  There is an angry tone in this conversation and in my view it is because the conversation is unhealthy.  This meeting makes me feel like I've been trapped in the Stanford Prison Experiment and am stuck being a guard. We go to great lengths to prevent students from taking a variety of classes from AP courses to honors courses to regular chemistry.  I wish this were an isolated thing, but I am quite confident that it is systemic because I see it frequently on social media, at conferences and from many teachers beyond my own district.  But I believe very strongly that this mentality of exclusion is damaging and worthy of resistance.  Students in our district are exposed to it every time they sign up for classes starting in 6th grade.  There is an unrelenting pressure put on them that they are not good enough to be where they are and the mental health toll is a disaster.  Think of a student that has been told every year that if they are not at a level of success that they should not be learning about chemistry, or biology or trigonometry.  Now envision what happens if that student struggles in a unit.  Even if they had been successful in everything they had done to that point, any struggle signals to the student that they do not belong in that class.  The conversations we have about course selection likely make children unhealthy in how they learn and I believe also promote segregation based on race and gender.  
We need to stop leading students to evaluate what they should do based on their grades and external mechanisms.  Many would argue that grades are essential to this discussion, but we are talking about 11 year olds.  We are talking about 14 year olds.  How a 14 year old does should have no bearing on whether they can learn chemistry as a 15 year old.  And often the evaluations we do don’t even make sense.  Math skills are not essential to high school chemistry.  High school chemistry uses multiplication and adding.  Students that struggle with manipulations in chemistry class struggle because they do not understand the chemistry involved in the manipulations.  Biology success should have no bearing on how a student does in chemistry.  There are millions of people that were more successful than I was in biology both in high school and in college but only a handful of times have I felt out of place in chemistry or physics.  These perspectives are common and counter productive.  Teachers of struggling students resort to them because of being overwhelmed by the difficulty of teaching.  If a student is struggling with something we should be able to give them specific feedback, have the student improve and continue that cycle throughout the year.  Instead we give students overly simplistic directives to avoid having the conversations we aren’t prepared for.  Work harder, study more, read the text more, etc.  
Students, teachers, parents, counselors and administrators all contribute to the reduction of course selection.  And perhaps all of us suffer the consequences of this as well.  Counselors and administration often use course selection as a means to avoid dealing with problems in classes.  If a class is taught using extreme methods that are exclusive, we help that teacher exclude students rather than address the teaching methods.  This can cause parents to seek exclusivity as a sign of elite status rather than focusing on student achievement.  This can allow negative teacher perceptions to fester.  So let’s break this habit.  If you’re a student don’t allow yourself and your fellow students to be marginalized by course selection presentations.  Ask your teachers thoughtful questions and seek out their passion.  Do the same with counselors.  We all love what we do and chose our profession out of passion.  Help us find our spark again.  Guide us into talking about the best parts of classes rather than the worst so you can walk into a class confident you will learn valuable things rather than being nervous about grading policies.  At some point in your life, no one will care what grades you got at all.  For many of us, that is when we are 17 years old.  So let’s spend less effort maximizing our GPA for little to no benefit and more effort learning about the best accomplishments of humanity.  

Sunday, December 3, 2017

International Chemistry In Your Kitchen #1 - Paneer

After reading Chemistry in Your Kitchen by Matthew Hartings this summer I decided to see if my International Baccalaureate students would be willing to have my learn how to cook a dish with their families.  Periodically my students will have a potluck during their core days where they miss their classes all day working on external assignments and there tends to be a wide variety of international cooking on display.  
In October I met with my first family (thank you Sharmas!) to learn how to cook Paneer.  I have grown up as a very picky eater and when you are a child that is a picky eater it becomes the mission of a select few to get you to try their casserole.  So I was very excited about paneer since it seemed like the perfect dish that was both new but not overwhelming to me.  
We boiled a very large quantity of milk and added some lime and vinegar to curdle the milk when it was just reaching boiling temperature.  
Figure 1:  Milk just before boiling

Figure 2:  The milk curdling after the addition of lime juice and vinegar

The acid bonds to phosphate groups on the casein proteins.  The casein has a hydrophilic and hydrophobic end.  The hydrophobic ends attract the same portion of other casein proteins and the hydrophilic ends attract to water because of the negative charge of the phosphate groups.  The acid reduces the attraction to water and causes the casein to clump as seen in Figure 2.  The mixture is then put into a towel allowing the excess liquid to drain.  The protein along with some trapped fats then link forming a block of paneer.  
Figure 3:  The paneer mixture is now forming while the excess liquid drains

Figure 4:  The paneer takes shape and can be cut into pieces

At this point we made a curry sauce using a variety of spices, tomatoes and onions.  The paneer was added to the curry sauce.  

Figure 5:  Paneer cooked in curry sauce

Figure 6:  The complete meal with paneer, lentil soup, yogurt, salad and naan.  

I had disorganized intentions behind doing this.  I had personal desires to learn how to cook more foods, and connect better with students and families in our IB program.  I had professional desires to connect chemistry and cooking and also chemistry with international mindedness.  The experience surpassed my expectations.  I learned about my students, got to eat an authentic Indian meal and it was completely vegetarian.  I learned you can purchase paneer at Costco and I also learned where to buy spices and groceries for preparing Indian food.  The concepts in this dish applied perfectly to the unit we learned next in class about acids and bases and we cooked paneer in class to reinforce the concept of acids as well as allow more students to experience an international dish.  We used citric acid rather than vinegar and it worked fine with no negative impact on the taste of the paneer.  Future possible experiments could focus on how the pressure applied to the cheese as it forms influences the final product or how concentration of acid affects the final product.  I believe the proteins clumping causes various components of the mixture including fats to get trapped and both of these experiments should influence what and how much gets trapped.  It would also be interesting to move a step further and add rennet and start developing cheeses.  


Figure 7:  My students Manasi and Ritika along with Manasi's sister Tanvi after our meal

Monday, October 2, 2017

What students need to understand gases at the particle level

Student #1 - The gas particles expanded because there was empty space.
Student #2 - Gases like to fill their container.
Student #3 - The balloon filled up because there was a vacuum.

There is a common misconception or lack of conception about gas particle motion.  The ideas start when students are very young as we teach them about solids, liquids and gases very early.  To compensate for the fact that students are not ready for the particulate level at this age we use observations of what happens at the macroscopic level.  Liquids take the shape of the container but do not fill it.  Gases fill the container and take its shape.  Solids are unaffected by their container.  Even though we do not express the particle level (or do so very poorly) students will still formulate ideas about why these differences exist.  By the time students finally get to a chemistry class where they can connect the macroscopic and particulate levels there are significant obstructions in place.  
There are a number of demonstrations available to test these obstructions and misconceptions and get students thinking.  But teachers must be very wary of oversimplifying the demonstration and offering their own explanations.  This can cause students to reinforce their misconceptions.  Instead focus on observations and begin providing students with the tools to organize particle level pressure analysis based on speed/temperature, direction, number of particles, size of the container and surroundings.  For an example consider the demonstration where a balloon is blown up backwards using a flask with hot water.  
Initially the flask has mostly air in it at a similar pressure to the surrounding atmosphere.  As the flask is heated, steam pushes some of the air out leaving the flask to contain steam and some hot air.  There is a smaller density of particles in the flask than out because the higher speed creates a similar pressure with fewer particles.  If there were the same density of particles in the flask as outside then the higher speed would result in a greater pressure in the flask than the atmosphere.  A greater pressure would mean more frequent collisions with the the container, and also the hole which would lead to more particles leaving the flask than entering.  It is only when the particle density is smaller in the flask that the pressure will be the same.  
Now the balloon gets placed on the flask and the flask is removed from the hot plate.  The particles in the flask begin to slow down as the temperature drops.  This causes fewer collisions and smaller collisions and thus a drop in pressure occurs.  The external or atmospheric pressure is constant and thus becomes larger in pressure and the balloon is pushed in until the smaller volume in the flask reaches a similar pressure to the atmosphere again.  
In order for the student to properly analyze such a situation they really need to articulate multiple steps and critically analyze the number of particles, volume of container, speed of particles and how each of these affects the overall pressure.  This task can be aided by using particle level drawings but it is indeed a formidable task.  Most students being overwhelmed with this task resort to adding in human features to the particles instead.  The particles have less space so the air particles move in to fill the empty space.  An underlying feature of these student alternative conceptions is that particles will move towards an empty space but students do not realize why this occurs.  This is crucial to eradicating some of the structures that we begin with. To begin addressing this have students draw a simple diagram with multiple colors and motion in multiple directions such as in Figure 1 below.

20171002_073429.jpg
Figure 1:  Student representation of an initial state of a gas.  

Then instruct the students to determine where the particles will be a short time later (IE after the time needed to move the length of each arrow).  Have them draw four different diagrams in sequence showing the particles’ positions based on their motion.

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Figure 2:  Student works showing how the particles move about based on their initial positions and motions

Ask the students why the particles moved the way that they did.  Ask clarifying questions if needed such as should the particles change speeds, will the particles collide with the walls and other particles?  Try and emphasize that there is no special direction or cause of the motion but that the particles were just moving to begin with and thus changed where they were.
Now the plot twist.

Have the students restart on a new whiteboard if possible and draw a bunch of particles in one location such as in Figure 3 below.  

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Figure 3:  Students restart having all particles in 1 location (IE in a balloon)

Now have them complete the same process as before.  They should note that as the particles move about that the particles spread throughout the container because the motions are in different directions and there is nothing to oppose their motions.  

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Figure 4:  Gas particles starting in a confined space that become free to move around

Why did the gas particles fill the container?  Was it because they like to spread out?  Was there a big reason or did they just happen to be moving in a way where they would spread out for no reason other than they were already moving to do so?  The particles that stay in the corner bump and collide causing them to change directions while those moving away from the corner are not impeded.  There is no force needed for the particles to fill the container, there is no suction.  The gas fills the container solely because gas particles move and they are moving in various directions.  (AP Chemistry teachers might even have seen a professor express that it is equally likely that all particles could have all of the energy as an equally likely microstate as a somewhat even dispersal.  This is false because the initial conditions make it impossible for that to occur.)


20171002_131319.jpg
Figure 5:  Teacher representation of gas particles moving and a confined gas that was released moving.  The bottom image is a confined gas for comparison purposes.

In Figure 5 above one can see the difference between gas particles moving throughout an enclosed space and gas particles confined to one small section of a confined space.  Did the left corner exhibit “suction” towards the particles?  Did they move towards the empty space because they wanted to fill it?  Absolutely not.  Rather the fact that gas particles move in various directions as an intrinsic quality of the particles is all that is needed for the spread of particles to occur.  There is no differentiation between the top series and the bottom series in Figure 5.  There is no way for the empty space in the second series box 1 to pull or force the particles to move.  There is no such thing as a suction force.  A gas particle cannot be pulled.  But there is an interesting tendency for the gas to spread based on the particles various motions.  
A high-level discussion that may be appropriate is what happens when you breathe.  It is probably natural for most people to assume that when they take a deep breath in, that they pull air in.  If you breathe in right now it will appear to you that you are controlling the air.  But you are not.  Your lungs cannot exert a force on air outside of your body.  Only the particles touching your lungs can be affected by your lungs.  The air that moves in when you breathe in was already on its way towards your lungs, you just caused fewer particles to be restricting their motion in.  By expanding your lungs using your muscles, fewer particles leave your mouth and the same amount of air is still moving towards your mouth and lungs as before.  Thus a net flux of air in occurs.  But those particles weren’t sucked in, or pulled into your lungs.  
(This discussion might also bring up the misconception that air leaving a rocket causes the rocket to move forward, a common misconception from Newton’s 3rd law)
After discussing breathing I had students ask about slurping noodles and drinking out of a straw.  Both were fantastic additions to the discussion as slurping requires contact between the substance and this makes it possible to create a force on the noodle particles.  The straw of course is dependent on the external pressure.  Some follow up concepts worth using to assess are why do gases move from high pressure to low pressure and modifying that with varying temperatures.  For example, if a high temperature gas and low temperature gas have the same pressure, why is there not a net transfer of particles?  Would the densities of the gases be different?  What would happen if  the hot gas cooled down?  Do the collisions cause speeds to change?  Do all gas molecules in a sample move at the same speed?  
With a better understanding of why a gas will fill its container and a better model to work with students should now be ready to give a much better analysis of common gas law demonstrations.  If anyone does the 2-L with a nail in it or the notecard on a mason jar filled with water; both of these demonstrations rely on a small amount of water leaking.  This causes the trapped gas inside of the container to decrease in pressure because the space available increases from the small amount of water leaving.  This causes the pressure from the atmosphere to be greater by enough to balance the pressure of the weight of the water and trapped gas.  For the 2-L the water stays in as long as the cap remains on and for the notecard the notecard stays in place and prevents a student from being soaked.  
If you use a vacuum pump to show marshmallow, balloon or shaving cream expansion make sure to explain to the students how the vacuum pump is engineered to allow particles to leave the glass dome and get pushed out by the engine, but particles are prevented from re-entering the dome.  Vacuum filtration is always a much more visible representation of this that students that continue on to organic chemistry in college will likely see repeatedly.  
When I first did gas pressure demonstrations the goals were simple.  I wanted students to articulate that gas pressure was caused by collisions and that pressure could be exerted in multiple directions.  But now I want them to be able to get to the point where they do higher levels of analysis of what is happening during demonstrations.  I want them to organize when temperature changes and when it doesn’t.  I want them to identify when there is a difference in particle densities.  I also want them to avoid adding human qualities to gas particles and this exploration where students draw arrows and then follow them through like a comic book strip might just be the key to seeing that to fruition.  

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Figure 6: More student creations