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Untouchable Key Escape Room Mark as Favorite (96 Favorites)

LAB in Percent Composition, Stoichiometry, Limiting Reactant, Percent Composition, Lewis Structures. Last updated April 29, 2020.


In this lab, students are presented with a key wrapped in aluminum foil a quantity of solid copper(II) chloride, a balance, distilled water and a selection of standard laboratory glassware and equipment. Without using their hands to touch the key, students must react the key with a copper(II) chloride solution in order to free the key and use it to escape from the chemistry classroom!

Grade Level

High School

NGSS Alignment

This lab 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.
  • Scientific and Engineering Practices:
    • Using Mathematics and Computational Thinking
    • Analyzing and Interpreting Data


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

  • Complete a chemical reaction in the lab, and separate the products by filtration.
  • Determine the limiting reactant in a chemical reaction using both collected lab data and observations, as well as theoretical data and stoichiometry.
  • Determine the percent composition of water in a hydrated compound.
  • Explain what happens microscopically in a single replacement reaction.

Chemistry Topics

This lab supports students’ understanding of:

  • Chemical Reactions
  • Stoichiometry
  • Limiting Reactant
  • Hydrates
  • Lewis Dot Diagrams
  • Percent Composition


Teacher Preparation: 20 minutes

Lesson: 80 minutes

Materials (per lab group)

  • A key wrapped in 1 layer of Aluminum foil
  • Copper(II) chloride dihydrate (1.50g needed)
  • Distilled Water
  • 100ml Beaker
  • Stirring Rod
  • Balance
  • Tongs
  • Filter Paper
  • Funnel
  • Erlenmeyer Flask


  • Always wear safety goggles when handling chemicals in the lab.
  • Students should not handle any chemicals with their bare hands.
  • 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.

Teacher Notes

  • To learn about this escape room, read the article, Using Escape Rooms in the Chemistry Classroom, published in the May 2020 issue of Chemistry Solutions.
  • The author also has created another escape room, focused on Thermodynamics for use in the AP Chemistry classroom.
  • It is recommended that this lab is used as a final exam review at the end of a general chemistry course.
  • It’s recommended that students are placed in homogeneous groups based on ability level.
  • Keys were purchased at a craft store and could be any size. They are wrapped in one layer of standard aluminum foil.
  • The premise of this activity is that the key is wrapped in aluminum foil and the students need to free the key by reacting it with copper(II) chloride. The students are supplied with enough copper(II) chloride dihydrate to enable them to mass 1.50 g of it and dissolve it into 50mL of water. This ensures that the aluminum is the limiting reagent and the key will be freed.
  • This activity can easily be adjusted for an Honors level class. For these students, have them determine how much cooper(II) chloride dihydrate they will need (and justify their answer) before they can begin the lab procedure.
  • Students are instructed to filter the solids from the solution so everything can be disposed of safely—solutions can be disposed of down the drain, as long as it returns to a wastewater treatment facility, and solid copper can be disposed of in the trash (refer to Flinn procedure 26a and Flinn procedure 26b for additional information). This also enables them to separate the key from the rest of the solids using tongs.
  • Students can determine limiting reactant from the mass of the foil/key package before the experiment and the mass of the key at the end of the experiment (so they could determine the mass of the aluminum foil).
  • Clues may be necessary for some student groups to be successful. Differentiating the hints can be helpful, so that students who need more help receive it, but discretely. Students should be told that their clues are confidential and not to share them with other groups. This was effective in that students did not know which groups had easier clues.
  • Examples of Clues:
    • Remember when drawing the Lewis Dot structure for H2O that it's sharing electrons. Remember when drawing the Lewis Dot structure for CuCl2 that there are ions with charges.
    • Remember that H2O and CuCl2 Lewis dot structures are drawn 2 different ways.
    • Remember when drawing the Lewis Dot structure for H2O that it's a covalent compound and when drawing the Lewis Dot structure for CuCl2 that it's an ionic compound.
    • Remember that the limiting reagent is the reactant that you cannot see any more after the reaction has finished.
    • Use your observations to give you your first guess as to limiting reagent.
    • Remember that the limiting reagent is the reactant that is used up first.
    • The molar mass of CuCl2.2H2O is 170.49 g/mol
    • Remember that the copper(II) chloride is a hydrate.
    • Remember that the molar mass of the copper(II) chloride dihydrate has to include the water molar mass.

For the Student



You have been caught in chemistry class all year and now, in order to escape, you must show what you have learned. The knowledge you have been given this year is your key to escaping. In order to escape, you must hand back that key to me.

As a group, you will be provided with a key wrapped in aluminum foil, a quantity of solid copper(II) chloride, a balance, distilled water and a selection of standard laboratory glassware and equipment. You CANNOT touch the key with your hands. You must instead react the aluminum with copper(II) chloride to free the key. By the end of the class period, you must submit the key and the answers to the accompanying questions.

In order to help you with this task, you will be provided with 3 clues. (Note: the clues will be different for different groups, so keep your clues confidential.) You must work only within your group. Consultations within the groups are encouraged, but consultations between groups are forbidden. The members of each group have been assigned. A portion of your grade will be assigned based on cooperation.

Special Note: The first group that hands me the key and the correct answers to all questions will earn 5 extra points, and the second group to do so will receive 3 extra points.


  • Always wear safety goggles when handling chemicals in the lab.
  • Do not touch any chemicals with your hands.
  • Wash your hands thoroughly before leaving the lab.
  • Follow the teacher’s instructions for cleanup of materials and disposal of chemicals.


Recall that this is a reaction between copper(II) chloride, CuCl2 and aluminum, Al. The balanced chemical equation is:

3CuCl2(aq) + 2Al(s) --> 2AlCl3(aq) + 3Cu(s)


  1. The form of CuCl2 we will be using is the hydrate, CuCl2 ● 2H2O. Mass out 1.50 g of CuCl2 ● 2H2O.
  2. Dissolve it in about 50 mL of distilled water in a 100 mL beaker.
  3. Mass the aluminum foil/key packet.
  4. Add the aluminum foil/key packet to the dissolved CuCl2 ● 2H2O.
  5. Stir carefully and observe.
  6. When the reaction seems to be over, stop stirring and let the solids settle on the bottom of the beaker.
  7. Filter the solids using a funnel and an Erlenmeyer flask.
  8. Use tongs to retrieve the key.
  9. Being careful not to touch the key with your hands, dry off the key and mass it again.


Mass of CuCl2 ● 2H2O (g)

Mass of Aluminum Foil/Key packet before the reaction (g)

Mass of the Key after the reaction (g)


Escape Questions

  1. Draw the Lewis dot structure for CuCl­2 and for H2O.
  2. What kind of chemical reaction is this? Justify your answer.
  3. What percent of CuCl2 ● 2H2O is water?
  4. Determine the limiting reagent using both your observations and with math.
  5. In this experiment, the aluminum "disappears". What happens to it microscopically and why can it no longer be seen macroscopically?