Catalysts in the Classroom (Brian Smith)

Title: Catalysts in the Classroom

Principle(s) Investigated: Catalysts make enthalpically favored reactions occur at a much faster rate. Besides the demo, are there any other "catalysts" in the classroom, and how can we measure their rates?

Standards:

HS-PS1-5 - Apply scientific principles and evidence to provide an explanation about the effects of changing the temperature or concentration of the reacting particles on the rate at which a reaction occurs. [Clarification Statement: Emphasis is on student reasoning that focuses on the number and energy of collisions between molecules.] [Assessment Boundary: Assessment is limited to simple reactions in which there are only two reactants; evidence from temperature, concentration, and rate data; and qualitative relationships between rate and temperature.]

Materials:

Cell phone with Google Sheets and Google Drive

Graduated Cylinder

H₂O₂ (30% conc)

2M KI

Soap

Dye

Procedure: Teacher guides students into setting up Google sheets on their phones, helping them take a screenshot of the phone to document battery and time. This data will be used later in the demonstration.

Teacher then demonstrates the very visual H2O2 decomposition reaction with food dye and soap to engage students. Students are probed throughout the demonstration about their ideas about the reaction, and why it may or may not be occurring (perceived flaws in the demo). After demonstrating the chemical process of catalyst, teacher discusses the student accelerated depletion of their phone batteries (enthalpically favored), and how those rates could also be calculated.

Using the data from the prior activity (taking a picture of their phones), students are then able to supplement additional data (a second screenshot), and complete an interactive worksheet that automatically assesses their responses.

Student prior knowledge: Enthalpy, equilibrium, chemical energy, decomposition reactions

Explanation: At my school, we are currently running on a very strict budget. Technology is a luxury that very few teachers have in excess. I have invested over $1000 in my own classroom to incorporate tablets and charging stations for as many students as possible, but I still rely heavily on the student's own phones for interactivity.

This comes at a cost; some students get distracted by their phones (I believe that they will be distracted with or without the incorporation of the phone in the classroom, so I might as well monopolize the screen time), some students complain about battery usage, and some apps are slightly more difficult to use. In an effort to help demonstrate a low cost integration of this demo, teachers will be filling forms out through their phones, and I hope to address some of these issues.

The lecture starts with an ENGAGE, using the traditional yet very visual decomposition of H2O2. A strong concentration of H2O2 (30%) leads to a more reactive demonstration, with food dye (red) and soap helping to make the reaction become a large bubbling column of O2 and H2O bubbles.

The teacher EXPLAINS the reaction, and turns the discussion towards an EXPLORATION of other rate modifying activities. Particularly, students are led to analyze the rates of battery discharge on their phones. Many of my students complain about the battery usage in the classroom, and I hope to check this criticism by showing each student that the classroom apps (Schoology, Google Sheets, Google Drive, Kahoot, etc) take a fraction of the energy that their other apps consume. In an effort to prepare students for college, quantitative analysis is performed in the Google sheet. Students are able to complete the interactive chart for quick, rapid assessments, and determine their own rates of discharge.

Questions & Answers:

1.) Does the reaction need to be 30% H2O2 + 2M KI?

Many catalysts can be used in place of KI, but KI is readily available and easy to make in high concentration. The 30% H2O2 helps accelerate the reaction. The brown, accordion shaped bottle is designed to accommodate this natural decomposition, and could be brought up as a discussion point.

2.) What is the catalyst, exactly, in the phone demonstration?

The catalyst accelerates the thermodynamically favored reaction. A phone battery will ultimately discharge, with or without user input. The catalyst, then, is anything that will speed up this event; increased WiFi usage, increased screen lighting, and increased processor usage among other triggers. All of these are initiated by the user, so, the student themselves can be thought of as the catalyst.

3.) Why do you calculate the rates of battery decay when these topics aren't required for NGSS?

Unfortunately, many of my students are missing a core component of academic rigor; mathematics. Students are currently struggling through molar ratios, and I jump at any opportunity to assess their practical mathematical abilities. While students will not need to calculate this particular rate in any collegiate level chemistry class, more complicated rate constants are derived through various spectroscopy techniques.

Applications to Everyday Life:

1.) Your phone usage should be a consciously monitored process.

Students do not recognize their own phone usage, and falsely blame school applications for consuming data or battery. I aim to demonstrate that these biased and ill-derived claims can be proven incorrect through simple analysis. Students should see how much social media consumes their screen time, which hopefully acts

2.) Enzymes are biological catalysts. Many medicines are inhibitors of these reactions.

A charger can be thought of as two different analogies in regards to the phone catalyst model. If it completely reverses the reaction, it is a simple input of energy capable of traversing the reaction hill and capable of reversing the thermodynamically reaction. Alternatively, if the reaction merely slows (the charger just combats the drain of the user), the charger can be thought of as a catalytic inhibitor. Many medicines are enzymatic inhibitors, so students are "prescribed" chargers in order to make additional real-world connections.

3.)

Photographs: Include photos and diagrams that illustrate the how the investigation is performed.

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