A case study is a guided inquiry activity that embeds problem-solving within a simulated real-world context. Case studies tend to be more challenging than traditional word problems because they are presented in a longer form, commonly as a story. In general, students work in small groups to retrieve data from the case and then solve the underlying dilemma.^{1}

The Golden Drain^{2} is a case study developed by Sharma and Wolfgang where students work to uncover a company’s lost revenue due to the error of a new employee. In this instance, the case is communicated to students via a transcript from a meeting between the new employee and their boss. The transcript presents the problem to be solved and contains all of the required data to find a solution. Guiding questions were included with the original publication, which were slightly modified in the shared document. The modifications were made for use in a high school classroom, whereas the original study was presented in a first-year undergraduate classroom.

This activity is easily differentiated by providing student groups with more or less supplementary information and guiding questions.

**References**

1. Lantz, J., & Walczak, M. (1997). The elements of a chemistry case: Teaching chemistry using the case discussion method. *The Chemical Educator*, 1(6), 1-22.

2. Sharma, A. K., & Wolfgang, D. E. (2016). The Golden Drain: A Stoichiometry Case Study for General Chemistry. *Chem. Educ.*, 21, 77-80.

Stoichiometry

Limiting Reactants

Percent Yield

Printed copies of the student document (found in Supporting Information).

- OPTIONAL -- start the class with a few related questions for a bell ringer assignment. Include one limiting reactant problem and one percent yield problem.
- Before forming student groups, distribute a copy of the transcript to each student.
- Ask for two volunteers to read the transcript (one to read the boss’s part and one to read Fred’s part).
- Instruct the rest of the students to follow along and underline or highlight important information as the transcript is read.
- After reading the transcript, split students up into groups of 3 with the following roles:
- Communications Specialist -- shares on behalf of their group during whole class discussion
- Calculator -- responsible for ensuring that all the calculations are correct by double or triple checking each question
- Manager -- responsible for writing on the provided analysis questions

- Distribute one copy of the analysis questions to each group.
- As student groups work to solve the analysis questions, move around the room to help move struggling groups in the right direction.
- Every 10-15 minutes, stop the group work and have students share some of their solutions and faciliate a short discussion.
- At the end of the activity, allow each group to share their recommendations about Fred.

**Editor’s Note: **Log into your ChemEd X account to access the Student and Teacher Document. Don't have an account? Free registration is available HERE.

Included with the student document (found in Supporting Information).

No preparation required for this activity (other than printing the student copies).

Sharma, A. K., & Wolfgang, D. E. (2016). The Golden Drain: A Stoichiometry Case Study for General Chemistry. Chem. Educ, 21, 77-80.

## NGSS

Engaging in argument from evidence in 9–12 builds on K–8 experiences and progresses to using appropriate and sufficient evidence and scientific reasoning to defend and critique claims and explanations about natural and designed worlds. Arguments may also come from current scientific or historical episodes in science.

Engaging in argument from evidence in 9–12 builds on K–8 experiences and progresses to using appropriate and sufficient evidence and scientific reasoning to defend and critique claims and explanations about natural and designed worlds. Arguments may also come from current scientific or historical episodes in science.

Evaluate the claims, evidence, and reasoning behind currently accepted explanations or solutions to determine the merits of arguments.

Mathematical and computational thinking at the 9–12 level builds on K–8 and progresses to using algebraic thinking and analysis, a range of linear and nonlinear functions including trigonometric functions, exponentials and logarithms, and computational tools for statistical analysis to analyze, represent, and model data. Simple computational simulations are created and used based on mathematical models of basic assumptions. Use mathematical representations of phenomena to support claims.

Mathematical and computational thinking at the 9–12 level builds on K–8 and progresses to using algebraic thinking and analysis, a range of linear and nonlinear functions including trigonometric functions, exponentials and logarithms, and computational tools for statistical analysis to analyze, represent, and model data. Simple computational simulations are created and used based on mathematical models of basic assumptions. Use mathematical representations of phenomena to support claims.

Students who demonstrate understanding can use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.

*More information about all DCI for HS-PS1 can be found at https://www.nextgenscience.org/dci-arrangement/hs-ps1-matter-and-its-interactions and further resources at https://www.nextgenscience.org.

Students who demonstrate understanding can use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.

Assessment does not include complex chemical reactions.

Emphasis is on using mathematical ideas to communicate the proportional relationships between masses of atoms in the reactants and the products, and the translation of these relationships to the macroscopic scale using the mole as the conversion from the atomic to the macroscopic scale. Emphasis is on assessing students’ use of mathematical thinking and not on memorization and rote application of problem - solving techniques.