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In this activity, students will work collaboratively to apply their chemistry knowledge in order to “escape the room.” They will work to solve four clues that span a plethora of topics ranging from Atomic Structure all the way up to Stoichiometry. These four clues will point them to four chemical reactions to conduct on a small-scale basis that will correspond with a four-digit combination to a lock. This engaging activity is not only fun for all students but also allows for interactive and collaborative review.

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 chemical properties.
  •  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
    • Analyzing and Interpreting Data
    • Engaging in Argument from Evidence
    • Obtaining, Evaluating, and Communicating Information


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

  • Demonstrate a clear understanding of atomic structure, periodic trends, ionic and covalent naming and formula writing, chemical reaction types, molar calculations, and stoichiometric calculations.
  • Conduct small-scale chemical reactions and make qualitative observations.
  • Calculate theoretical quantities using stoichiometry.

Chemistry Topics

This activity supports students’ understanding of:

  • Atomic Structure
  • Periodic Table
  • Ionic Compounds
  • Covalent Molecules
  • Nomenclature
  • VSEPR Models
  • Chemical Reactions
  • Mole Calculations
  • Stoichiometry
  • Limiting Reactants


Teacher Preparation: 30 minutes
Lesson: 90 minutes



  • Always wear safety goggles when handling chemicals in the lab.
  • Students should wash their hands thoroughly before leaving the lab.
  • When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.
  • See SDS information for all chemicals used in this activity.
  • All chemical reactions are being conducted by small-scale laboratory means, which requires only 1 or 2 drops of each chemical substance. This minimizes danger, waste, extra work, and clean-up.

Teacher Notes

  • This activity is helpful to be used as a review of first-semester topics in a Chemistry Honors class or culminating the Stoichiometry Unit in a first-year Chemistry course.
  • In preparation for this activity, the teacher should print several copies of the “Combination Lock Clues” handout (one will be needed per group that is participating). This handout is divided into 5 sections (the five clues needed by students to open the combination lock). The teacher should cut out each of the clues, keeping multiple copies of the same clue type stacked together. Throughout the notes below the teacher will be directed as to where the various “Combination Lock Clues” should be placed in a chemistry classroom.
  • Students should be placed in groups of two or three and each group is given the Escape Room student packet which is made up of:
    • Escape Room Letter handout
    • Escape Room Clue 1 handout
    • Escape Room Clue 2 handout
    • Escape Room Clue 3 handout
    • Escape Room Clue 4 (components from page 2 are cut out and placed in a Ziplock bag)
  • Students will first read the Escape Room Letter which is written from a fictional person named Professor Tantalum W. Rhenium (Ta W Re).
  • Next, students should work through the Clue 1 handout, which provides a list of 24 review questions/clues. They will write their answers to each question in the corresponding space. When completed the shaded letters of the answer section can be written in order starting with answer 1 to reveal the phrase, “Check Grad Cylinder Cabinet.” When students discover this information, they should go to the graduated cylinder cabinet in the classroom to find the first clue for use in the small-scale lab portion of this Escape Room activity—eventually helping them to open the 4-digit combination lock that holds the treasure!
    • Note: The teacher should place copies of the first clue from the “Combination Lock Clues” handout inside the graduated cylinder cabinet in their classroom/lab for each group to find upon completion of the Clue 1 handout. This clue reads: “Mix Phenolphthalein with NaOH”.
  • After successfully solving the first clue, students will move to the Clue 2 handout, which lists the sequence “1C D6 7G H9 10K” at the top of the page. Using a ruler and the element symbol images on the handout, students can draw a line between each corresponding number and letter in the sequence to reveal the answer, “Check Fire Blanket.” When students discover this information, they should go to the fire blanket in the classroom to find the second clue for use in the small-scale lab portion of this Escape Room activity—eventually helping them to open the 4-digit combination lock that holds the treasure!
    • Note: Again, the teacher should place copies of the second clue from the “Combination Lock Clues” inside the fire blanket for each group to find upon completion of the Clue 2 handout. This clue reads: “Mix Barium Chloride with Sodium Sulfate.
  • Next, students should work through the Clue 3 handout. Every question on the handout results in a numerical answer. These answers then correspond to a letter given in the code list on the left-hand side. An example of how to use this coding system is the first stoichiometry problem results in 9 grams of H2O, using the code list on the left students can see that the number “9” corresponds to the letter “I”. When they have answered each question correctly and decoded each answer, the answers will reveal the statement “In Fume Hood.” When students discover this information, they should go to the fume hood in the classroom to find the third clue for use in the small-scale lab portion of this Escape Room activity—eventually helping them to open the 4-digit combination lock that holds the treasure!
    • Note: Again, the teacher should place copies of the third clue from the “Combination Lock Clues” inside the fume hood for each group to find upon completion of the Clue 3 handout. This clue reads: “Mix Bromothymol Blue with Hydrochloric Acid
  • Finally, students will work through the Clue 4 handout. Students should first read the letter associated with Clue 4, and then will need to assemble the pieces of a limiting reactant stoichiometry problem that has been placed in a Ziplock bag. Using stoichiometry, the students will calculate 147 grams for the MgO. Referring back to the letter that is part of Clue 4, students should determine to look on page 147 of the book provided in the clue.
    • Note: I have the book “Elements of the Universe” by Glenn Seaborg in my classroom, and place copies of the fourth clue from the “Combination Lock Clues” clue on page 147 of the book for students to find. This clue reads: “Mix Hydrogen Peroxide with Potassium Iodide with Starch.”
    • Teachers can edit the letter associated with Clue 4 in order to use a different book if this particular book isn’t readily available.
  • Students will then take the clues of what substances to mix and perform four small-scale laboratory experiments. Each combination of solutions will result in a different color. These colors will correspond to the combination lock numbers on the bottom of the Escape Room Letter that they read at the start of the activity. These colors/numbers can be changed as needed by the teacher, to match the specific combination for a lock that is used.
  • Small-scale chemistry laboratories are relatively safe, time-efficient, easy to set up, and environmentally sound.  I put the solutions in Flinn Polyethylene dropper bottles and clearly label each chemical solution. Small Erlenmeyer flasks that are clearly labeled with Beryl disposable pipets (clearly labeled as well) can also be used. 
  • I place all the chemicals for this portion of the activity on a laboratory bench (including safe distractors such as a sodium chloride solution). Each chemical reaction can be observed by combining just 1-2 drops of the solutions (as directed by each clue) in a well-plate or on a plastic sheet protector. If small-scale chemistry laboratories are not familiar to your students, be sure to provide guidance regarding safety, disposal, and procedures at the beginning of the activity.
  • If needed, teachers could provide students with an unlabeled grid for a data table to record the results of each reaction.
  • As teachers circulate the room, encourage students to take their clues as they are collected and mix the two chemicals, which will ensure an efficient flow to the activity. If your classes are regularly doing small-scale laboratories, the students will immediately and fluidly go to their small-scale chemical reactions.
  • I also place distractor clues around the room, such as false clues for mixing like “Mix Sodium Chloride with Sodium Sulfate.” These distractor chemical reactions will not chemically react.
  • Additionally, I place the clue labeled “You calculated wrong…Go back to the drawing board” in the Glenn Seaborg book at the page corresponding to the excess stoichiometric calculation answer as well as other pages. This isn’t necessary but adds to the challenge and fun of this activity.
  • When introducing the activity, I encourage the groups to be “stealthy” in their discovery of clues and solutions to the puzzles. I also encourage them to move around the room when looking for a clue not in one big group but as individuals so that other groups do not see where the clues are hidden. My students often like to “compete” in these types of activities and find them to be more enjoyable in solving them in their own groups. 
  • When student groups determine the four-digit combination to the lock, they can then unlock the four-digit bike lock to receive their prize (candy, extra credit, a handshake, or whatever you want).  This bike lock is optional as you could use folders with different combinations. In my experience, students like the culmination of getting the combination correct.
  • An answer key for all the escape room clues has been included for teachers to reference. 
  • Finally, I encourage teachers to simply act as a facilitator and questioner during this activity. Try not to give the student groups any hints, unless a group is really struggling to move forward.