Applying Equilibrium Concepts

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SWBAT apply equilibrium concepts to a real world situation via a reading passage.

Big Idea

Applying LeChatelier's principle is important in addressing real-world problems such as food production.


Planning today's lesson had multiple stresses upon the teacher:

  1. We are in the midst of equilibrium and LeChatelier shifts, one of the most challenging topics in regular chemistry.
  2. Tonight is prom, so I will be missing about 1/3 of my students as they prepare for the evening.
  3. There are also two field trips removing more of my students from class.
  4. Our lab conclusions from the previous day left much to be desired, so work on equilibrium must continue.

This perfect storm of circumstances means that I need to maximize the value of today's lesson with something that can be completed outside of class, addresses LeChatelier shifts, and makes equilibrium meaningful to students.

Last year, one of my colleagues found the Haber reading used in today's lesson.  This year, a different colleague adapted it to a close reading exercise by embedding the questions.  Our unit test has a passage with embedded questions on the equilibrium reactions between hemoglobin and oxygen and hemoglobin and carbon monoxide.  We avoided testing on the Haber process as we knew we would teach with it a lot.  This passage is good to orient students to this type of reading and also as an activity that satisfies the constraints on the day listed above.

This simple reading is standards packed, starting with HS-PS1-6: Refine the design of a chemical system by specifying a change in conditions that would produce increased amounts of products at equilibrium.

Students are also obtaining and evaluating information (Science and Engineering Practice 8).  From this reading, students are reinforcing that "systems can be designed to cause a desired effect" (Cause and Effect Cross Cutting Concept) and that "much of science deals with constructing explanations of how things change and how they remain stable" (Stability and Change Cross Cutting Concept) and learning that "systems can be designed to do specific tasks." (Systems and System Models Cross Cutting Concept)

Opening Discussion

5 minutes

When the period begins, the inevitable question arises: "Are we having a free day?"  This results from students looking around and recognizing that in two of my four classes, there is less than 50% attendance.

I ask, "Do we ever have a completely free day?" and students smile slyly and say "No, we always have something to do." I explain that the lab conclusions from the previous day leaves a lot to be desired, but that I will be returning them in our next class when everyone is back.  I explain that there is one required part today, and then the rest is student choice. 

I show students the Haber process reading and explain that this is a reaction we have talked about, and that students will need to read and highlight the passage, and answer the questions.

After they complete the reading and questions, they have three choices:

  1. Complete and turn in missing work.
  2. Revise their reaction rates poster if they have not yet.
  3. Work on assignments for another class.

I explain that if they can't find something to do in those options, I can get them some practice sheets on balancing chemical equations.  Students assure me they have options they can work with.

Reading and Application

25 minutes

I pass out the Haber Process Reading and let students get to work.  Someone asks if they can listen to music while reading and working and I allow it as it helps them to focus.  I remind students to read carefully, as all of the questions can be answered from the reading.  My students have a tendency to skim and scan as detailed here.

While students are working I circulate the room checking in with them.  When they ask for assistance, I help explain the meaning of various terms in the reading and the questions.

Some students do not ask for assistance, and really struggle with answering the questions.  Others only answer parts of the question.  In this student example, the student simply restates the third question rather than find the "how" from the passage.

This student did pretty well on the backside, but missed the second part of question 2 and mixed up "ammonia" with the more general "fertilizers" at the end of the paragraph above it.

For next year, I am going to separate the questions out, and have the students read and highlight the passage first.  Students will have to show me their annotations as proof of reading before providing the questions.  In this case I think a lot of students rushed through due to the empty classroom and had their minds anywhere but chemistry.

Student Choice Time

20 minutes

When students finish their reading and questions they have three options:

  1. Complete missing assignments
  2. Revise poster from their Reaction Rate Investigation
  3. Do work for another class

This is the only in-class opportunity I provide for students to revise their reaction rate posters, so many students choose that option, particularly as that grade is in our 65% weighted assessment category.

While students are working I am circulating the room to ensure they are doing something productive, either for my class or another. 

The students who are revising their posters have some questions about what needs to be done to improve, and how to submit the work.  I have the students put the changes and additions on separate paper and submit it to me with their graded rubric so I can evaluate any improvements to their grade.