Conversion Guidelines
Thruout our vehicle for illustration will be Calorimetry of Proton Transfer Reactions.
· Get in touch with your research mode (query/discover), rather than your teacher mode (exposit/verify)
· Identify a concept
For example: Level 1 Equilibrium; Level 2 Thermo; Level 3 Enthalpy
· Select an experiment that meets these criteria:
you like it
it addresses the identified concept(s)
data is collected using simple/reliable apparatus (can you make it both simpler and better? Can you
make it smaller?)
good data results from good technique (try it out)
it is amenable to data pooling
data lends itself to discovery analysis (whenever possible, by graphical methods); i.e., it shows
trends that allow the student to generalize from the specific
generalizations from the experiment can be tested by further relatively simple experiments
· Boil the experiment down to its essence; express this in one or two sentences. For example,
"Determine the enthalpy change for reaction of HCl with NaOH by measuring the temperature change that occurs when a specified number of moles of HCl reacts with a specified number of moles of NaOH."
· Identify the verification aspects of the experiment for ultimate modification
In this case the student is instructed to
1. "determine" (actually verify) the D H of
2. reaction of HCl with NaOH by
3. measuring D T
· Identify focus questions that the essential experiment (acid/base thermodynamics) could be used to answer, and pick one. The questions should address key aspects of the selected concept or a sub-concept of that selected. Also the question should be framed to encourage student hypotheses. NOTE: this is a step that requires creativity, so it cannot be "algorithmized."
Suggestions?
What is the relationship between D T and the amount of acid (reacting with a fixed amt of base)?
What is the relationship between D T and the formula for the acid?
Do all acids/base reactions involve the same D H?
What concept is addressed by each of these questions?
Concept: q = D H = CPD T
Concept: stoichiometry; extensive nature of D H
Concept: Hess' Law
· Identify multiple sets of experimental conditions to insure a lot of data. If possible, the data should be amenable to graphical analysis or tabular presentation that is striking. Some imagination is required here too.
Suggestions?
each student group can be given a different volume of acid to react with base;
groups can be given different acids altogether.
SHOW A DATA PLOT HERE.
· Formulate follow-on questions and follow-on experiments to be addressed after students have induced a law, principle, or concept. Often these will ask the student to make a prediction based on the first-stage result, then test the prediction.
Suggestions?
How can we measure D H for formation of H2PO4- from H3PO4 by rxn with NaOH?
· Rebuild the experiment:
Change the Title (many titles anticipate the results)
Ex:
Determination of the Empirical Formula of Copper(I) Iodide (Szafran, Pike, Foster, page 115)
could become
The Empirical Formula of a Compound of Copper and Iodine.
Rework the goals (objectives) to be consonant with query/discovery.
Ex:
To verify Boyle's, Charles', and Graham's Laws experimentally.
To Determine the value of absolute zero. (Szafran, Pike, Foster, page125)
could become
To explore the relationships among the pressure, volume, and temperature of a gas.
To discover something interesting about temperature.
Rework the background discussion to emphasize experiment rather than theory. In particular, remove all information that would reveal the result. The outcome has to be a surprise (a discovery). The student should not be confined by preconceived notions about what s/he will discover.
Reduce the detailed procedural steps significantly so student must "think" about how to collect the data.
Reduce the discussion of calculation/data analysis significantly so student must "think" about how to use the data to answer the question.
Replace existing (probably algorithmic) questions with conceptual questions.
Structure the prelab to prepare the student for the required calculations, but do not give away the result!
In general, replace statements with questions!!!!!! Transfer responsibility from you to the students.
Note: the first 2 can be reversed. You may have a pet experiment; then you must decide what concept you want students to discover via the experiment. Often several alternative concepts can be addressed, depending on how the experiment is reconstructed. This is the approach you will have to use today, because we will give you an experiment to work on!