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ACTIVITY in Review, Culminating Project, Stoichiometry. Last updated February 05, 2023.


In this activity, students will apply their chemistry knowledge in order to solve ten clues in an effort to determine a three-digit combination that will open a “lock.” This is ideal for a review activity, as the clues span a plethora of chemistry topics. The solution from each clue will be used to correctly write a chemical reaction and a corresponding stoichiometry calculation. Ultimately, by solving the stoichiometry calculation, the answer will match the numbers in the three-digit combination and open the “lock.”

Grade Level

High School

NGSS Alignment

This activity will help prepare your students to meet the performance expectations in the following standards:

  • HS-PS1-2: Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of a chemical reaction.
  • HS-PS1-7: Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.
  • Scientific and Engineering Practices:
    • Using Mathematics and Computational Thinking
    • Developing and Using Models
    • Analyzing and Interpreting Data
    • Engaging in Argument from Evidence


By the end of this activity, students should be able to:

  • Demonstrate a clear understanding of intermolecular forces, elements of the periodic table and their properties, identification of chemical reactions, nomenclature of organic compounds, molecular geometries, molar quantities, diatomic molecules, and laboratory glassware identification.
  • Calculate theoretical quantities using stoichiometry.

Chemistry Topics

This activity supports students’ understanding of:

  • Atomic Structure
  • Periodic Table
  • Intermolecular Forces
  • Nomenclature
  • VSEPR Models
  • Chemical Reactions
  • Molar Calculations
  • Stoichiometry


Teacher Preparation: 15 minutes
Lesson: 90 minutes


  • Printed copies of the following documents for each group:
    • The Student Letter Handout
    • The Student Clues Handout
  • 8-10 envelopes


  • No safety concerns in this activity

Teacher Notes

  • This activity is helpful to be used as a culminating review of topics in an honors chemistry class.
  • In preparation for this activity, the teacher should print several copies of “The Student Letter Handout” and “The Student Clues Handout.” One copy of each will be needed per group that is participating.
  • This activity is best when students are partnered in groups of two.
  • Students will first read the letter, which is written about a fictional person named Professor Tantalum W. Rhenium (Ta W Re).
  • Next, students should work through the 10 clues. The clues are numbered according to the date in the professor's laboratory notebook (01-Nov-2022 is the “01” or first clue). The laboratory notebook will give students a hint as to the topic to use to solve each clue.
  • If students are struggling to solve a clue, it is best to encourage them to move on to easier clues and come back when they gain some momentum. Before any frustration, the teacher can give hints as to what topic, ask leading questions, and confirm if students solve a clue correctly.
  • It is also best to instruct students to keep their solutions concealed from other groups.
  • After students solve all ten clues, they will put those clues together to form a chemical reaction and a stoichiometry problem.
  • Teachers should create approximately ten envelopes with different three-digit combinations written on each one and place them on the teacher lab bench. In nine of those envelopes, place a message that says, “You calculated wrong ... go back to the drawing board.” In the envelope with the correct answer, write a message such as, “You have solved Ta W Re’s treasure!” Typically, the group that solves this first is given a prize (such as candy, extra credit, a handshake, a high-five, or whatever you want). Teachers can do this however is best in their own classroom.
  • I encourage all teachers to simply act as facilitators and questioners during this activity. Try not to give the student groups any hints, unless a group is really struggling to move forward. My students love this escape room activity and the outside-the-box thinking that it presents. There is great satisfaction in solving a mystery as challenging as Professor Tantalum W. Rhenium!
  • An Answer Key document is provided for teacher reference. It shares information for solving each of the clues as well as how to solve the final stoichiometry problem in order to determine the 3-digit code for the “lock.”
  • Note: All graphics used on the “Clues Handout” are open source, Creative Common images, except for clue #8. The uses glassware images in this clue were created with Chemix software.