Intro Chem Benchmark Quizzes

[kevin_revell]

Like most professors, my traditional grading scheme looks something like this:

Assessment	Points
Unit Exams (4)	400 pts.
Lab:	200 pts.
Homework:	100 pts.
Final Exam	200 pts.

The problem with this classic approach is that it is too easy for students to miss foundational skills.  Consider an example from a non-majors intro course:  A student struggles with unit conversions – and performs poorly on that part of one exam.  This gap causes him to also struggle with stoichiometry later in the course.  But he does well on the qualitative portions, and is diligent with his homework and lab.  Ultimately, he gets enough partial credit to pass the class with a C.  But he still can’t convert between units.  And at some point in his career, this gap will hurt him.

So instead, let’s begin with a question:  “What should every student who passes this class be able to do?” 

To address this issue, I introduced benchmark quizzes in my organic classes in the fall of 2016 (I wrote about these here and here).   After exceptional results, I’m adapting the strategy to my intro chem classes this semester.

First, I designed 10 key learning benchmarks.  Throughout the semester, I am giving 10 quizzes – one for each benchmark.  The quizzes are pass-fail, with no partial credit.  However, the students will have three attempts to pass each benchmark.   Further, the quizzes are tethered to the student’s homework grade.  In order to “unlock” their homework grade, they must pass 6 of the 10 benchmarks.  The quizzes are very direct, and students have an example quiz available to them beforehand. 

Here are my benchmarks:

Benchmark	Description
1	Convert between units, including metric prefixes.  Relate density, mass, and volume.
2	Determine the number of protons, neutrons, and electrons in an atom.  Write symbols for atomic number and mass number.
3	Write electron configurations for atoms.  Identify valence configurations.
4	Identify ions and charges by name.  Correctly write the formulas for ionic compounds.  Correctly name ionic and binary covalent compounds.
5	Balance chemical equations
6	Solve mole-to-mole and gram-to-gram stoichiometry problems.
7	Solve stoichiometry problems using fuel value or reaction enthalpy.
8	Draw Lewis structures for covalent molecules and ions.  Identify the electronic geometry around a central atom.
9	Use the ideal gas law to solve for P,V,n, or T.
10	Relate grams, moles, volume, and molarity for solutions.

I plan to administer these quizzes at the beginning of each lab period.   Students who have not passed previous quizzes can re-take the earlier quizzes at the same time.  Here are two examples of the sample quizzes I shared with the students.

Implementing this comes with some logistical challenges:  I have both morning and evening classes, with a little over 200 students total.  However, by making the quizzes pass-fail, I remove the need to mark up the quizzes or agonize over partial credit.  Passes go in one pile, fails in another.  I think I can move through them quickly.

I’m looking forward to giving the first benchmarks this week.  I’ll update as the semester progresses.