Summary

In this activity, students will work collaboratively to apply their acid-base chemistry knowledge in order to “escape the room.” Students will have to apply their understanding of many different facets of acid-base chemistry, including the Arrhenius Acid-Base model, Brønsted-Lowry Acid-Base model, pH calculations, and acid-base titrations, while utilizing puzzles and ciphers to work through the escape room clues. This engaging activity is not only fun for all students but also allows for interactive and collaborative review.

Grade Level

High School (AP)

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.
• Scientific and Engineering Practices:
  • Using Mathematics and Computational Thinking
  • Analyzing and Interpreting Data
  • Obtaining, Evaluating, and Communicating Information

AP Chemistry Curriculum Framework

This activity supports the following unit, topics and learning objectives:

• Unit 4: Chemical Reactions
  • Topic 4.6: Introduction to Titration
    • 4.6.A: Identify the equivalence point in a titration based on the amounts of the titrant and analyte, assuming the titration reaction goes to completion.
  • Topic 4.8: Introduction to Acids-Base Reactions
    • 4.8.A: Identify species as Brønsted-Lowry acids, bases, and/or conjugate acid-base pairs, based on proton-transfer involving those species.
• Unit 8: Acids and Bases
  • Topic 8.2: pH and pOH of Strong Acids and Bases
    • 8.2.A: Calculate pH and pOH based on concentrations of all species in a solution of a strong acid or a strong base.
  • Topic 8.5: Acid-Base Titrations
    • 8.5.A: Explain results from the titration of a mono- or polyprotic acid or base solution, in relation to the properties of the solution and its components.

Objectives

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

• Understand the Arrhenius model of acids and bases.
• Identify the formulas for common strong acids and strong bases.
• Identify the ionic components of a strong acid and strong base.
• Identify the relative pH values, electrolytic capabilities, and percent dissociation of strong acids and strong bases as well as weak acids and weak bases.
• Understand the Brønsted-Lowry model of acids and bases based on proton transfer involving those species.
• Identify conjugate acid-base pairs.
• Perform pH and pOH calculations based on concentrations of species in a solution of a strong acid or strong base.
• Identify the volume added and pH of a solution at the equivalence point given a titration curve.
• Differentiate the type of titration curve by analyte and titrant.

Chemistry Topics

This activity supports students’ understanding of:

• Acid/base theories
• Strong vs. weak acids and bases
• pH
• Titrations

Time

Teacher Preparation: 15 minutes
Lesson: 45–60 minutes

Materials

• Printed copies of the following documents:
  • Escape Room Letter
  • Escape Room Clues 1-4
• Computer, tablet, or phone with internet access
• Calculator (for pH calculations)
• Optional: lockbox containing prizes or rewards

Safety

• No specific safety precautions need to be observed for this activity.

Teacher Notes

• This activity is helpful to be used as a review of acids and bases in a Chemistry Honors class or an Advanced Placement Chemistry class.
• The role of the teacher is to circulate the room and facilitate discussion while stimulating the thinking of students working in small groups trying to solve each part of the escape room. 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.
• This escape room can be presented in hard copies of each clue, as described in these teacher notes, or virtually through a Google Form, where teachers could set up the form so that students are given access to the next clue once they have correctly entered the answer for the previous clue. Teachers could also utilize a hybrid of both approaches where students work on hard copies and input their answers to each clue on the Google Form.
• Students should be placed in groups of two or three and given the Escape Room Letter handout and the Escape Room Clue #1 handout. Once students solve this clue and present the correct solution to the teacher, they will then be given the next clue. This pattern continues until they have solved all four clues.
  • When students decipher the clue to each of the four sections of the acid-base review, they will need access to the internet to find the answer to each clue.
  • An answer key for all the escape room clues has been included for teachers to reference.
• At the end of the fourth clue, students will end up with a 4-digit number that could be used to unlock some sort of lockbox. You could put small rewards (candy, stickers, etc.) or “class coupons” (extra credit, excused homework pass, etc.) into a lockable container with a programmable lock if you would like to add a physical lock component to this activity. (You could also use a bike lock, a small lockbox, etc.) Students often enjoy the culmination of getting the combination correct.

Activity Overview

• Students will first read the Escape Room Letter, which is written by a fictional person named Professor Tantalum W. Rhenium (Ta W Re).
• Next, students should work through the Clue #1 handout, where they will use their knowledge of the Arrhenius acid-base model to develop two answers to each bullet point. They will then use those two answers to identify two numbers in the encryption key provided (see below right). As an example, the answers to the bullet point could be “Strong” and “OH^–” which correspond to 1 and 4 on the key. The students then can utilize those two numbers in the Polybius cipher – the two numbers correspond to a row and column, respectively, on the cipher chart (see below left) which identifies a letter. Given the answers of 1 and 4, described above, students would then identify the letter “D” (row 1, column 4) for that bullet point.
  • Students are given instructions on how to use the cipher in the text of the clue.

Activity Overview

• Students will first read the Escape Room Letter, which is written by a fictional person named Professor Tantalum W. Rhenium (Ta W Re).
• Next, students should work through the Clue #1 handout, where they will use their knowledge of the Arrhenius acid-base model to develop two answers to each bullet point. They will then use those two answers to identify two numbers in the encryption key provided (see below right). As an example, the answers to the bullet point could be “Strong” and “OH^–” which correspond to 1 and 4 on the key. The students then can utilize those two numbers in the Polybius cipher – the two numbers correspond to a row and column, respectively, on the cipher chart (see below left) which identifies a letter. Given the answers of 1 and 4, described above, students would then identify the letter “D” (row 1, column 4) for that bullet point.
  • Students are given instructions on how to use the cipher in the text of the clue.
    
  • All of the bullet points will spell out the clue “YEAR OF HIS NOBEL”.
  • Since the text in Clue #1 is all about Svante Arrhenius, the students should look up that Arrhenius won his Nobel Prize in “1903,” the answer to Clue #1.
  • Special Note: Many students will try to find the year Tantalum W Rhenium won the Nobel Prize. Professor Rhenium is a fictional figure with the initials from elements 73, 74, and 75 – if students become stuck on this, encourage them to look back at the introductory text for clue #1

• After successfully solving the first clue and presenting the answer to their teacher, students will obtain the Clue #2 handout. This clue will have them use their knowledge of Brønsted-Lowry acids and bases to fill in the missing words of each bullet point. The circled letter of each word will spell out a clue.
  • All of the letters from the boxes will spell out the clue “BIRTH CITY.”
  • Since the text in Clue #2 finishes with “there is one thing I wished I knew about Johannes Brønsted…,” the students should look up Brønsted’s city of birth, “VARDE.”
  • Special Note: Many students will solve the first word of birth and immediately try to find Brønsted’s birth year, which is an incorrect answer. Students will also try to find Arrhenius’ birth city because they did not read the text that this clue is all about Brønsted-Lowry. These are good distractors to keep your students looking at the details.
• Once students correctly identify Brønsted’s birth city, they will receive the Clue #3 handout, which will have them determine pH and pOH values given concentrations of strong acids, concentrations of strong bases, pH values, and pOH values. Each bullet point will have a numerical pH or pOH value answer, and those numbers will correspond to letters as given in the introductory text of the clue.
  • Each number corresponds to a letter which spells out the clue “WHO INVENTED THE PH METER?”
  • The answer to the clue is “BECKMAN.”
  • Special Note: There are two clues that require precision in calculating the pH (the sixth from last clue and the final clue). An example is the final bullet point calculates the pH to be 10.29. This number corresponds to three numbers (10, 2, and 9) and therefore three letters (T, E, and R). The number of spaces presented in the clue will help students out with this precision.
• The final Clue #4 handout will have students interpret four titration curves. They will have to identify volume of titrant to reach the equivalence point, pH of the solution at the equivalence point, and characteristics of different types acid-base titration curves (strong or weak acid vs. strong or weak base and vice versa) to determine three four-digit numbers.
  • The three four-digit numbers are “8468,” “7579,” and “4123.”
  • These three four-digit numbers will be put into a mathematical equation to determine the answer to the clue of “8468 – 7579 + 4123 = 5012”
  • As mentioned earlier in the teacher notes, this final four-digit number could be used as the code for a physical lock to open a container with small prizes or rewards, if desired.