Monday, March 9, 2015

My Own Winter Term Comment

At NAIS Conference with my friend and mentor Ellen on the last day of the winter term.
I just finished writing winter term comments for my students.  I thought it only fitting to write one for myself.  Here it is.  I think I got an A- for the term.

Sharon had a good winter term with her chemistry students.  This term she was faced with the significant challenge of teaching the mole concept to her honors chemistry students.  Although this is a challenging unit to teach for many reasons, (including, but not limited to, the fact that kids just don't understand it, and it can be a bit dry) Sharon rose to the occasion with a new stuffed mole to lift everyone's spirits.  This class mascot served as good moral support for the students as they worked through mole problems on white boards and in the lab.  She also chose to start the AP Chemistry term with electron configurations and periodic trends.  What was she thinking?  Coupling this abstract unit with the mole concept is virtually a perfect storm for frustration because these are the least exciting parts of any chemistry course.  There was an audible sigh of relief from Sharon and her students when both classes moved on to the next topics.  The celebration was short lived in her AP class when the students learned that kinetics and equilibrium were on the agenda for the rest of the term.  Even though her students were having difficulty with the integrated rate laws, Sharon was once again in her element with this data-drive, lab-based unit.  She continued the article review project this term with only the honors classes.  Although she started the term with a renewed sense of purpose for this science literacy project, she had difficulty sustaining the attention for details needed to really pull it off.  Her improvements to the project this term included a shared google doc to track the articles each student chose, student choice of a week for their due date rather than one day in the term, blocking out vacation weeks and mid-term weeks from the schedule, and allowing students to work with a partner on the assignment.  These changes were steps in the right directions for implementing a rich experience for the students, but she lacked the follow through necessary to really pull it off.  However, the article tweets on the class Twitter feed were very popular amongst her followers and often favorited and retweeted.  Overall, Sharon conducted her classes with attention to safety, an eye for fun, and an intensity that helped to warm the hearts of her students during this ridiculously cold and snowy New England winter.

Wednesday, February 11, 2015

Equilibrium Games are a Win

Water transfer equilibrium analogy.
I haven't taught equilibrium for nearly ten years!  This time around I decided to tackle the conceptual understanding of equilibrium first with three different analogies and a POGIL activity before even mentioning the words "equilibrium expression".  The outcome has been very positive from my perspective, even though my AP Chemistry students are not always eager to volunteer to be a reactant or a product in my activities.

The first thing I did was show the students the "Red Pill or Blue Pill" clip from the Matrix.  I likened equilibrium with taking the red pill because you have to open your eyes to the real world of chemistry.  We can no longer pretend that every reaction goes all the way to completion!  Maybe this scared the kids more than amused them, but I found it very funny.

Using two different sizes of straws to transfer water.
The first equilibrium analogy we did was the famous water transfer reaction with two different sized cups.  I labeled two large bowls "reactants" and "products".  The reactant side was filled half way with blue water and the product side was empty at the beginning of the reaction.  Two students volunteered to transfer water from reactants to products or from products to reactants, each using a different sized beaker (I used a 50 mL and 250 mL beaker).  When the reaction began, the product to reactant transfer was very small, but steady gained in volume as the reaction progressed.  Meanwhile the reactant to product transfer started large and gradually shrank.  After every 5 or 6 transfers we tested to see if we had reached equilibrium by measuring the volume of water transferred in each direction.  This simple and fun demo was an excellent kick off to the conceptual understanding of equilibrium.  When it was over my students understood that equilibrium is reached when the forward and reverse rates are equal, not necessarily when the amount of reactant and product are equal.

Now the students were ready to put some numbers to their water transfer equilibrium analogy.  The students conducted the classic experiment with two graduated cylinders and two different sized straws.  They used the straws to transfer water from one graduated cylinder to the other, each time measuring the volume in the two cylinders.  (By the way, McDonalds has really large straws that are perfect for this activity.)  The result is a beautiful graph of the concentration of the "reactants" and "products" as they approach equilibrium.  It only took about six transfers for the system to reach equilibrium, which was just about all the patience my students had for the water transfer with drinking straws.  I loved how the volume in each graduated cylinder was different at equilibrium, even though the amount of water transferred was the same.
Checking the volumes at equilibrium.

Penny transfer equilibrium activity.
The third activity on the opening day of equilibrium involved another transfer reaction, but this time with pennies.  The students labeled one dish "reactants" and another dish "products".  Staring with 42 pennies, they transferred pennies at a fixed rate in both directions.  Once again, the reaction started with all reactants and it gradually reached equilibrium in approximately six transfers.  In this activity, the students kept the transfer rates constant (1/4 for the forward reaction and 1/3 for the reverse reaction), but they experimented with changing the initial conditions.  They tried starting with more reactants, all products and no reactants, and an even split between products and reactants.  They also added reactants to a system at equilibrium to see how that would change the equilibrium "concentrations".  Through these variations of the penny transfer analogy, the students could see with their own eyes (and data), how a reversible reaction will reach equilibrium from many different starting conditions.

On Day Two of our equilibrium unit, I split the kids into groups of three or four and gave them a POGIL to work through.  The POGIL activity inched them a little closer toward the equilibrium expression because the examples were based on a chemical reaction ( A <-> B).  This activity is also data driven, similar to the penny and the straw water transfer, but using moles of A and B.  Each student was given a different set of starting conditions for one of two equilibrium systems.  By sharing their results, the class derived the results necessary to calculate the ratio of products to reactants.  The POGIL was the perfect transition from the reversible reaction concept to an equilibrium expression calculation using molarity, and determining the increase and decrease of the species in the system.
The class agenda for Day Three of the equilibrium unit.

On Day Three I taught the kids how to write an equilibrium expression and use it for calculations.  I was so pleased at how quickly they mastered this new skill.  I believe that the two days of hands-on activities and equilibrium analogies gave them the perfect conceptual groundwork for understanding the equilibrium expression.

Adding stress to the system by inhibiting the decomposition reaction.
The fourth and final equilibrium analogy was the "tank equilibrium".  The forward reaction volunteer assembled a film canister from a canister and a lid.  The reverse reaction volunteer took the canister apart.  All of this wass happening in a fish tank.  This fun game was the perfect introduction to Le Chatelier's Principle.  At some point in the "reaction", I dumped more product into the mixture.  The  reverse reaction picked up steam and generated reactants more quickly.  Later, I blind folded just the reverse reaction volunteer to see how this would change the equilibrium conditions.  Overall, this demo was a lot of fun and sparked the conversation about stress on a system.

Tomorrow we will head into the lab for the AP Chemistry lab kit exploring Le Chatelier's Principle using real chemical reactions.

Note:  these activities are all available on the Flinn e-learnig video library.

Sunday, February 8, 2015

Kinetics and Guided Inquiry Are Not Good Friends

I just wrapped up a three week unit on kinetics with my AP Chemistry students.  As part of the unit we attempted two kinetics experiments from the set of sixteen recommended labs in the AP Curriculum.  The first one was the Rate of Decomposition of Calcium Carbonate, and the second one was the Kinetics of Crystal Violet Fading.  Both of these experiments exposed the students with the data-driven nature of rate laws, using two different techniques.  The difficulty I faced was trying to push my students towards inquiry without telling them what to do!  Let's face it, teachers like to tell their students what to do.  When a lab group starts floundering, I nearly have to restrain myself to keep from bailing them out too soon.  But with the kinetics experiment, my students struggled to understand how to collect the data in a reproducible and consistent way.  With only one week of kinetics under their belts, my students struggled to understand what data to collect, and then what to do with it to derive a rate law for the reaction.  Add equipment difficulties to the conceptual challenge of this experiment and the results can be very frustrating and confusing to my chemistry students.

The first lab we tackled was the Rate of Decomposition of Calcium Carbonate.  I used the Flinn kit and lab handout, Publication No. 7648.  The experiment is actually pretty straight-forward:  students react solid calcium carbonate, in the form of marble chips, with hydrochloric acid.  The goal of the lab is to determine the order of the reaction with respect to HCl.  By changing the [HCl] the students can plot the data and determine the effect of the concentration on the rate of a reaction and calculate the order, in the end writing the rate law for the reaction.    In the introductory activity the students all ran the experiment using 6M HCl.  The reaction rate was monitored by measuring the gas produced from the reaction using a plastic syringe to trap the gas.  We ran into problems right away!  Only one group got decent results.  The syringes leaked or stuck to the sides, which prohibited them from getting an accurate measure of the volume of gas produced.  The one lucky group with the working apparatus was so pleased with their work; they had a lovely graph of the progress of the reaction.  The other three groups fooled around with their apparatus until the leaking stopped and the plunger was free to move, eventually resulting in something that resembled a typical graph of reaction rate over time.  At the end of day one, only one group walked away smiling, the other three were very frustrated and annoyed that their apparatus failed.  (Next time I'll try water displacement to collect the gas.)

After some discussion of the results and the goal of the experiment on Day 2, we charged ahead to the guided inquiry part of the experiment.  In this phase of the lab, the students were asked to design an experiment to determine the effect of concentration on the reaction rate.  It was obvious to me:  run the experiment again with different concentrations of HCl (and I just happen to have 2 M , and 4 M HCl prepred for you...).  The only catch was that two of the groups had to monitor the rate of the reaction by measuring the loss of mass of the system, while the other two groups were required to measure the volume of gas produced (just like the introductory activity).  To make it fair, I had the groups draw from the lucky beaker to determine what direction they would go with the experiment :  mass or volume (I included one "wild card" allowing the group to choose).  At first, the groups that drew the mass cards were annoyed that they had to change the experiment.  However, the leaky gas collecting apparatus made for a very difficult experiment for the groups who got the volume cards.   Even the lucky group from Day 1 was foiled by leaky and uncooperative syringes in the guided inquiry phase.  Adapting the experiment to measuring mass took some tweaking, but produced decent results if the reaction mixture was stirred consistently.  The volume groups limped along with the experiment, getting mostly straight line plots for their reaction progress, rather than a graceful curve.  In the end, the data proved to be consistent in three of the four lab teams regardless of the technique they used.

I walked away from this experiment with another good reminder of how difficult inquiry is for both the students and the teachers.  These students in my AP Chemistry class are the best science students in the school, who are experts at solving problems in class.  However, when I put them in the lab without step-by-step instructions, they struggle to create a solution.  What I need is MORE TIME to develop the lab skills and hands-on problem solving that the students gain from inquiry.

In the interest of time, I decided to use a step-by-step procedure to conduct the Kinetics of Crystal Fading experiment.  In this experiment, the students used spectroscopy to monitor the color change over time of the blue dye when it reacts with hydroxide ions.  I have a set of Vernier colorimeter probes in my lab, and the software package on Logger Pro includes this experiment.  I chose to go with the "standard lab experience" for the spectroscopy data collection.  I'm so glad I made this choice because something happens to students when you say the word spectroscopy.  They get this fearful look on their faces and they groan audibly.  Why do they dread this wonderful lab technique so much?  Maybe it's the "black box" effect, with this machine taking readings that they don't understand.  Maybe it's the quantity of data produced that they have to graph.  Maybe it's the new terminology that throws them off.  I'm not sure, but I saw it happen to my students with this experiment.   Even with step-by-step instructions, the lab took two days to complete!  The nice outcome here is that all the groups got beautiful data from the experiment that they could analyze using the integrated rate law graphing technique. I was happy to have real data to analyze, rather than another set from the book.  I'll save the guided inquiry for another day, and just tell them how to do the spectroscopy experiment for now.  Maybe I'll have them design their own lab using this technique AFTER the AP exam.

Thursday, January 29, 2015

When Kids Cheat...

Cheating is such a frustrating part of my job.  I know that kids cheat on homework assignments and lab reports.  So I have to work to safeguard my assignments from mindless regurgitation of facts.  I need to create assignments with answers that cannot be googled.  I have to make up ways for students to demonstrate their knowledge that is different from what I did last year because most of my assessments are electronic and "out there" on student machines.  With my AP Chemistry class, I have to record all the past questions I've used to prevent reuse in less than four years.  And, shame on me for assigning the questions from the lab kits, those answers are all easily googled in seconds.  I have moved toward collaborative lab report writing because the most frequent cheating cases were from one lab partner copying another.  Now I have students write the report together, in class, so that they can develop their ideas as a team.  Working towards "cheat proof" assignments only gets me so far.  What really bothers me about the academic dishonesty problem is the emphasis on earning a grade rather than actual learning.

As a teacher I work very hard to create engaging learning experiences for kids.  My heart goes into labs and demonstrations to find many ways to help kids to learn difficult chemistry concepts.  But there's always that point where the fun stops and the kids have to demonstrate what they've learned.  Inevitably there's the question, "Is this on the test?"  I know that sounds so cliche, but kids ask it all the time!   To say my kids are grade motivated is an understatement.  Kids in my class will ask to revise their work, do test corrections, or re-work homework problems.  I should be thrilled by this extra effort, but in the end it's just another attempt to earn a grade, not learn the chemistry.  Do kids actually care about learning?  The pressure to get an A on their transcript is very real and in the forefront of my students minds.  Somewhere along the way they traded in their excitement for learning for stress about GPA.   I wish that I could infuse them with some of the joy that comes from learning something new.  Wouldn't it be great if I could tap into the curiosity and excitement that you see in an elementary school classroom, the same energy these high schoolers had only a few years ago.

When kids cheat on their work, I am reminded that my job as a teacher is a complicated balancing act.  I want to foster exciting learning opportunities while upholding a standard of mastery of the chemistry.  All of this is happening in short segments of time that, for my students, is crammed between five other demanding classes with teachers just as eager to inspire and motivate them to master their subjects.  Place that in the context of a boarding school experience that includes sports, dorm life, and social events, and it's no wonder kids are looking for a quick way to get to the end of an assignment.  Drinking from the fire hose, you might say.  Throw in the competition for college admissions and you have the perfect storm of stressed out teenagers.  In the face of what seems like an impossible task, I am trying to keep my focus on learning.  I want to challenge my students to learn; and if they enjoy the process, great, and if they walk away thinking "Chemistry is pretty cool", then I've succeeded. 

Wednesday, January 14, 2015

Blow the Lid Off of Magnesium Oxide Lab

Magnesium reacting with oxygen in a red-hot crucible
Photo by Julia Paneyko
Every chemistry student makes magnesium oxide in the lab in their introductory course.  My students do it twice in my lab program:  once in the study of chemical reactions (types of chemical reactions lab) and then again in the mole unit.  High school chemistry students around the world are determining the chemical formula of magnesium oxide in this classic experiment.  I use this experiment as my first "mole concept application".

The procedure is very simple:  heat magnesium in a crucible until it is fully reacted with oxygen.  Use the mass data of the magnesium before reaction and product after reaction to calculate the mole ratio of Mg and O in the compound.  This mole ratio is the experimental chemical formula of magnesium oxide.  My "go to" procedure for this lab is found in ChemTopic Labs Volume 7:  Molar Relationships & Stoichiometry by Flinn.  In Flinn's version of the lab, there are detailed instructions to heat the magnesium with the lid on, then open the lid every three minutes, and then heat it some more with the lid at a tilt.  All of this manipulation of the crucible lid invariably results in at least one dropped and broken lid each lab period.  And, the results of the lab are usually not that great, with many groups getting ratios other than the expected 1:1.

My students are heating their crucibles with lids off.
This year I decided to try the lab with no lid on the crucible during the heating process.  It seems only obvious to let the maximum amount of air into the reaction by just leaving it open for the whole reaction.  I was a little nervous that burning magnesium might pop out of the crucible, but that didn't happen all day.  The hardest part of the experiment was adjusting the bunsen burner so that it would get hot enough to start the reaction.  Most of the reactions burned at a steady rate, without a big flare up of bright light.  Once the reactions were completed without any safety issues, my students crunched the numbers.

Here's where the big payoff was obvious.  The lab results were much better this year, with most groups getting the expected 1:1 ratio without the need for sad stories about experimental errors in the conclusion.  Taking the lid off resulted in better results, more interesting observations during the reaction, and better results for the chemical formula for magnesium oxide.

Wednesday, January 7, 2015

Mole Art

My new mole is making friends in class.
As a new teacher I thought that I would never be like my quirky science teacher colleagues, but after nearly twenty years of teaching chemistry, I have developed a weakness for “Mole Art”.  I love the element of fun that mole art brings to my teaching environment.  My students get a little glimpse into my soul when I bring in a new hand-made mole to decorate my classroom. 

Milli Mole
It started about seven years ago when I discovered a stuffed mole pattern in ChemTopic Labs Volume 7:  Molar Relationships & Stoichiometry by Flinn.  The pattern is very easy and quick to make.  I made three immediately: a custom designed mole for every chemistry teacher at my school.  The department chair got a mole in school colors with a “P” on the side for Pomfret.  My other colleague got a mole made out of her college school colors, adorned with flowers so everyone could tell it was a “she-mole”.  I named my first mole Milli, and I even gave her a rabbit fur hat (made out of fur that fell off of our rabbit pelt when I was demonstrating the polarity of water).  I manage to find reasons to have my mole in class throughout the year. I bring her out on the first day that I introduce the mole, and then again when my students learn molarity. 
The image of a one molar solution will always stay fresh in their minds when then think of Milli sitting in a one-liter beaker.  But wait, I can double the concentration by adding one of her mole friends to the beaker.  The site of the two moles crammed into a one-liter beaker always makes me laugh out loud.  My students quickly realize that not only do I like to make things by hand, but I also enjoy bad jokes! 
A one molar solution!

My new Mole Doorstop, the latest addition to the mole art collection.
My latest mole creation is a wonderful mole doorstop, which was inspired by a great book called Faux Taxidermy Knits by Louise Walker.  This fun book is a must read for every knitter.  The mole doorstop was very fun to make; and it knit up in just one day!  When it is finished, the mole is emerging from a mound of dirt as if to say hello to everyone.  The base is filled with rocks to weigh it down so that it will function as a doorstop.  I made the new mole just in time for the start of the mole unit.  On the first day of the mole concept, I split my class into small groups to do the POGIL activity called “Relative Mass and the Mole”.  (POGIL Activities for High School Chemistry by Laura Trout)  One of my students came up to the front of the room and brought the mole back to his table for inspiration.  I saw him with his arm around the mole during class, as if he wanted to include the mole in the group discussion.  When the novelty wears off, I’ll put him to work as a doorstop, but for now he is located on the front table to greet my students when they come to class for more mole calculations. 

A two molar solution!

In addition to the mole doorstop and the fuzzy mole friends I have made, I also have a handsome mole mobile hanging in the room.  I call it the molebile.  Two years ago our Head of School charged us to “make your space your own” at the start of the school year.  He said, “Give your classroom some personality and make it a fun learning environment”.  I knew exactly what I had to do:  make more moles.  For this mole art piece, I used the same stuffed mole pattern from Flinn to make a set of moles in bright colors. 
The original "molebile".
I have bins of fabric scraps for just this kind of spontaneous project.  I found some antiquated glassware in our stock room to serve as the perfect vehicle for the bright moles.  I always enjoy the moment when my students finally understand the molebile, usually a few days (or weeks) after I introduce the concept. 
The second "Molebile" I made for my friend in the lab upstairs.

Mole art is just one of the ways that I try to make chemistry a fun and memorable experience for my students.  I never underestimate the value of a good sense of humor in the science classroom.

The class mole, Bernard Martin, is giving some inspiration during the mole test.

Monday, December 8, 2014

Building Batteries: Electrochemistry in the Fall Term!

Electrochemistry in the Fall!

My students loved building batteries.
Every teenager in my class has an electronic device that is powered by a battery.  You would have difficulty finding a more relevant chemistry topic to the typical teenager!  This year I decided to move electrochemistry to the fall term because it is the perfect follow up to the Six Types of Chemical Reactions Unit (ChemEd Workshop). With the Chemical Reactions unit still fresh in their minds, I presented electrochemistry as a “spotlight” on the single displacement reaction.  This two-week unit was the perfect opportunity to introduce the activity series of metals, oxidation and reduction, and standard reduction potentials in an engaging and relevant series of hands-on activities.

The activity series of metals was the bridge between the single displacement reaction and the galvanic cell.  The students conducted a micro scale study of the reactivity of common metals.   (Flinn ChemTopic Labs:  Oxidation and Reduction We set up a series of reactions between metals and salt solutions, with hydrochloric acid included, to create an activity. The working knowledge of the relative reactivity of these common metals was the backbone of the galvanic cells that they will construct in the lab later in the week. 

The magnesium-copper cell in the Hot Dog Clock demonstration  (Flinn ChemFax Publication No. 91335)     was the first galvanic cell they observed.   This cell is easy to construct “real time” and provides enough voltage to replace the AA battery in a clock, I used my chemistry clock, of course. I have the students write the half reactions on their white boards during the demonstration, identifying them as oxidation and reduction.  I reinforced the concept that electrons flow from the more active to less active metal, which is a direct application of their observations of the activity series of metals (both magnesium and copper were included in the activity series lab).  At the end of this demonstration the students have gained experience with the construction and chemistry of a simple galvanic cell.

Success!  Light is on!!!

Armed with a basic knowledge of how a battery works, I then gave the kids a design challenge with very few instructions.  I provided them with all the parts of the classic Daniel Cell:  copper and zinc electrodes, 1 M solutions of copper sulfate and zinc sulfate, and a 1 M solution of sodium nitrate for the salt bridge.  They used 24-well plates to construct a single Daniel cell, the salt bridge is a small piece of a cotton swab, alligator clips, and a multimeter.  Their goal was to construct a battery that will generate enough voltage to light a 2.6 V LED.  The students used a voltmeter to record the voltage of the cells as they construct them, and to monitor the voltage when more cells were added to the system.  This fun activity was complete when they took a photo of the lit LED connected to their battery.  The students really enjoyed this hands-on activity because they don’t know how many cells were required and they had to tinker with the system to get it to work.  You could hear cheers from lab teams when they got the LED to go on. A minimum of three cells in series was required to light the LED.  This year, I had one group of boys who took this challenge to the next level by constructing a battery that produced 10 volts!
10 Volts!

The final piece of this fun electrochemistry unit was another micro scale lab to explore the voltage of galvanic cells constructed from other metals. (Flinn reference here) We used silver, aluminum, iron, magnesium, copper, and zinc to create a galvanic cell “snow flake”.  The students constructed the snowflake out of filter paper, with a different metal electrode in each point.  The students soaked the tip of the filter paper by each electrode with a matching metal solution.  They soaked the center of the snowflake with sodium nitrate.  Using a voltmeter, they measured the cell potential for all the possible combinations.  The students used the sign of the voltage in each combination to determine the anode and cathode for each cell.  They learn how to calculate the theoretical cell potential of a standard cell for each galvanic cell they tested.  The desired outcome of this experiment is to get the students to make the connection between the standard reduction potential of each metal and the voltage obtained in a galvanic cell.

Exploring galvanic cells with my AP Chem students.
It was a lucky accident that my AP Chemistry class was studying electrochemistry at about the same   Most of my AP Students completed this electrochemistry unit in the spring last year, so they only needed a refresher course to get them up to speed on galvanic cells.  For this advanced group, I set out a series of metal electrodes and solutions and instructed them to construct galvanic cells and study their cell potential.  Each group took a different approach to these opne-ended instructions.  One groups decided to create series and parallel circuits using the same type of cell.  Another group decided to try as many combinations they could construct form the materials.  And a third group made four different cells, then connected them all in series to see how much loss was in the system.  All of the AP students experimented enough with these supplies to allow for a deeper understanding of the electrochemical circuit and the chemistry happening in each cell.
time as my Honors class.

Trying a range of electrodes in series.
The final piece of the electrochemistry exploration this fall was “electrolysis day”.  Sounds a little strange, but I wanted to emphasize the difference between an electrolytic cell and a galvanic cell.  I made an attempt to conduct a silver-plating reactions.  This one needs more work for next fall!  And I did an electrolysis demonstration of tin(II) chloride, which forms both tin and the tin(IV) ion, with a beautiful display of silvery crystals.  Then I finished off with the classis electrolysis demonstration with my Hoffman apparatus   All of these demos need some polishing before I do them again (no pun intended), it was a bit of a rush job to get them together for class.  We ended electrolysis day with some calculations of how much metal is plated if a current is passed through a solutions for a specified amount of time. 

Electrochemistry is an engaging and relevant topic that is a perfect fit for any high school chemistry class.  Moving this unit to the fall term was a successful experiment with positive outcomes for me and for the students.  I enjoyed watching the students dive deeper into chemical reactions.  My students enjoyed constructing batteries “from scratch” and harnessing the power of a chemical reaction.

Here are some examples of my student's lab reports from the battery labs.  These are creative google presentations that include student pictures from the labs and their results.

Lea and Alex's Battery Lab Report

 Khia and Aaron's Battery Lab Report

Rebecca and Josh's Battery Lab Report