The Rest of the Limiting Reactant Story

 
In December my classes wrapped our study of reactions and stoichiometry with a test just before our winter vacation.  I didn't have enough time to get to limiting reactant problems, so that was first on the agenda when we returned in January.  Coincidentally, that same week our school re-opened our learning center which had been re-imagined during first semester and transformed into The Hub, part library/part collaboratory.  I took advantage of the intersection of those situations to change up my treatment of limiting reactants.  My process prior to this year had been standard: start with a hands-on activity to introduce the concept, lecture on how to solve problems, practice in the lab the next day, quiz on day 3.  

Here is what I did this year:

Day 1:  Students met me in a campfire mediascape classroom in The Hub.  I passed out iPads and introduced the app StoichSim.  This simple but powerful app shows mass relationships in reactions by representing masses as bars that increase or decrease in size as the reactants are used and the products are formed.  I gave the students a set of questions to think about while they used the app and gave them some group work time.  Then we reconvened as a big group.  I used Reflector by Air Squirrels to mirror 4 iPads onto the TV in the mediascape so students could see the answers to all the questions for four reactions at a time.  That way they could see that the answers to their discussion questions were the same no matter which reaction they considered.

Day 2:  Students met me in the Learn Lab in The Hub.  This classroom features 4 tables, each with computers and the ability to mirror to the TV at the table's end.  After a brief intro, students were grouped for problem solving with a notes page and access to screencasts that show how to solve limiting reactant problems.  As a group, they could decide if they wanted to solve first and watch the screencast as a double-check or watch the screencast and take notes as we had traditionally or something in between.  Students, as a group, could choose the method they liked best.  I circulated to answer questions and provide help.  It was interesting to me that in one class everyone immediately turned on the screencast, but in the class right after that one, not one group began with the screencast.  They had two practice problems to try for homework.


Day 3:  Students completed one of the limiting reactant labs that I have used in past years.  Students dissolve two compounds in water and mix them, forming a precipitate.  They filter to isolate it and let it dry overnight.  They completed one more homework problem that night.

Day 4:  They took the quiz and finished the lab.  I wrote about my quiz here.  It included a standard limiting reactant question and a question that asked students to draw pictures to represent a limiting reactant problem.

 

 

So how did it go?

 

The data:  I finished grading the lab and the quiz this weekend.  My students averaged an 89% on the lab (2% higher than last year) and 87% on the quiz (3% lower than last year).  Some anecdotal observations:  Several students told me that they went back and watched the screencasts several times, so making those helped students who wanted extra help.  I asked one of my best students what he thought of learning this content.  He told me that he thought it went fine, but he still likes it best when I lead the class as a whole. 

There were some mitigating factors.  First, three snow days wrapped around a weekend.  And they occurred between Day 2 and Day 3, so some content was more than likely lost between the day they first solved problems and the day they took the quiz.  And I was absent on quiz day, so some students may have had questions that they didn't get answered.  And we were in The Hub on the first day it opened, in a classroom with glass walls.  My students did a great job paying attention despite the fact that they felt they were in a fishbowl, but the distractions may have detracted from the lessons.

Overall, I don't really know if this was better or worse than what I have done before.  The results seem about the same, but it was fun to try something a little different.  I really enjoyed teaching in these unusual spaces.  The change of scenery and furniture helped me imagine the lessons in a different way.  It was nice to step out of my cramped classroom and a little bit out of my comfort zone.  Stay tuned for more of the story as it unfolds this year.