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Summary

In this project, students will use their knowledge of thermodynamics to design a handwarmer for a manufacturing company that can maintain a temperature of 30-40°C for at least 5 minutes and is designed to fit in the average human hand. Students will create a final product after rounds of testing and an advertising poster that summarizes the results of their testing and promotes their design.

Grade Level

High School

NGSS Alignment

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

  • HS-PS3-1: Create a computational model to calculate the change in the energy of one component in a system when the change in energy of the other component(s) and energy flows in and out of the system are known.
  • HS-PS3-3: Design, build, and refine a device that works within given constraints to convert one form of energy into another form of energy.
  • Scientific and Engineering Practices:
    • Using Mathematics and Computational Thinking
    • Developing and Using Models
    • Analyzing and Interpreting Data
    • Constructing Explanations and Designing Solutions

AP Chemistry Curriculum Framework

This project supports the following unit(s), topic(s) and learning objectives:

  • Unit 6: Thermodynamics
    • Topic 6.1: Endothermic and Exothermic Processes
      • ENE-2.A: Explain the relationship between experimental observations and energy changes associated with a chemical or physical transformation.
    • Topic 6.4: Heat Capacity and Calorimetry
      • ENE-2.D: Calculate the heat q absorbed or released by a system undergoing heating/cooling based on the amount of the substance, the heat capacity, and the change in temperature
    • Topic 6.6: Introduction to Enthalpy of Reaction
      • ENE-2.F: Calculate the heat q absorbed or released by a system undergoing a chemical reaction in relationship to the amount of the reacting substance in moles and the molar enthalpy of reaction.

Objectives

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

  • Design and engineer a final product that utilizes at least one form of energy.
  • Explain how their product works with regards to energy transfer, exothermic reactions, and calculations of energy released and/or absorbed with enthalpies and specific heat capacities.
  • Make a claim about the effectiveness of their handwarmer and support their claim with data on their advertising poster.

Chemistry Topics

This project supports students’ understanding of:

  • Conservation of energy
  • Heat transfer
  • Exothermic and endothermic processes
  • Enthalpy
  • Engineering design and development

Time

Teacher Preparation: 30-60 minutes
Lesson: anywhere from 2-4 hours spread over several days. (This may take more or less time depending on the amount of prototyping students need to do in order to complete the task for the final design and poster production.)

Materials

  • Goggles and aprons
  • Various chemicals, including:
  • Sodium chloride
  • Activated charcoal
  • Calcium chloride
  • Iron filings
  • Rice
  • Water
  • 5% acetic acid (many store-bought vinegars)
  • Sodium bicarbonate
  • Other available substances that generate exothermic reactions that students suggest based on their research
  • Scoopulas, beakers, and graduated cylinders for whatever chemicals you use
  • Balances and weigh boats
  • Temperature probes and Vernier lab quest OR thermometers
  • Ziplock bags in snack, sandwich, and quart sizes
  • Twist-ties
  • Student-provided design materials to make a realistic, sellable product (such as fabric/cloth to contain and “dress up” their final product)
  • Poster board
  • Markers/pens/colored pencils

Safety

  • 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.

Teacher Notes

  • This is a project that is used to apply concepts of thermodynamics to a real-world problem. Students should have already explored concepts of thermodynamics, including energy, conservation of energy, system and surroundings, calorimetry, enthalpy, and specific heat capacities and calculations.
  • This could be used in a thermodynamics unit or as a post-AP Exam/end-of-year activity.
  • This project can be introduced at the beginning of your thermodynamics unit to get the students thinking. Then throughout your thermodynamics unit you can stop and have your students modify their models/designs as they gain the secondary knowledge. This will allow for their design ideas to evolve throughout the unit.
  • To cut down on the quantity of supplies needed, you could have students work in small groups of 2 or 3. This also gives them the opportunity to develop ideas with their peers, which better represents real-world engineering projects. In this case, you may wish to have them evaluate their teammates throughout the process so that you can intervene if some students seem to be doing all the work or not allowing others on their team to participate fully.
    • Students are given the option to do a smaller scale run (~5 g reactants) as proof of principle for any reaction they might use as part of their design before building their first prototype to ensure their heating method is a viable option.
  • It can be hard to let the students come up with their own models. Some students will only want to use rice to make a rice bag but then they soon realize it is not practical because they have no way of activating it at a football game unless they heat it up before they leave. Stay open minded and understand that their projects/models may change drastically as they continue to collect knowledge and discuss with their peers.
  • By the end, most students end up using combinations of chemical energy along with the specific heat capacity of water and rice to create interesting designs. Some of the best designs involve the use of calcium chloride in one pouch, water in another, and then one can activate it by squeezing it. Some students then connect it to rice which allows the heat to sustain longer and not run out so quickly or disperse into the surroundings. Below are some images of previous work:
Project handwarmerdesignchallenge photos
  • Some students used electrical energy (batteries and wires) to make gloves that warm up, trying to recreate electric heating pads/blankets. They used voltage and an equation to calculate Joules of output from their design. I usually try to redirect students from this method due to safety concerns. You could tell them up front that they cannot be battery powered if you wish.
  • The calculations section will look different for each student/group, depending on the design of their product. They will all involve temperature change, and they will need to know the mass (and formulas/molar masses of chemicals) if they plan on using specific heat calculations or enthalpy of reaction. They would need to look up specific heat capacity and enthalpy of reaction values for the substances/reactions they use.
  • Students will be bringing in their own design materials. (You may want to have a selection of materials for low-income students to choose from if cost is going to present a barrier to their participation in this project.) For example, if they want to turn a stuffed bear into a handwarmer, they will provide it, or if they want to create fleece handwarmers, they will bring in the fleece along with the tape or thread needed to complete the fleece pouch. Let students know this ahead of time.
  • Encourage students to use materials that make their product resemble a real, sellable item. They will need to create their products with their own designs in mind so temperatures can be collected appropriately.
  • A suggested rubric is available for download in the sidebar. You could modify it as you desire. You could also provide it for students at the outset of the project so they know how they will be evaluated for this project.
  • If time allows, you could substitute a presentation to the class for the poster. Each student or group could “pitch” their product and gain public speaking experience. The requirements for the poster could be included on a PowerPoint (or similar) presentation instead.

For the Student

Lesson

Background

You are asked by a manufacturing company to design a new efficient style of handwarmer that holds a temperate between 30 to 40 oC (~85 to 105oF) and sustains this temperature for at least 5 minutes. Your product needs to be able to fit in the palm of a hand or held around the hands. The design should be “portable” and activated using a simple method (think of cold packs and handwarmers in the store). You will be turning in your Activity Log, your final product, an advertising poster for your product, and a reference list.

Objective

Design and build a handwarmer that sustains heat for at least 5 minutes and maintains a temperature within the range of 30 to 40oC.

Materials

Student provided materials (start planning for what you will need and how you will get it!):

  • Home materials such as: cloth, fabric, and any other styling materials needed to make the design look authentic when you present it to the manufacturer.
  • Any other material (ex: cotton balls, gloves, hand muff, etc.) you need that is not the chemicals and basics provided by the teacher listed below.

Teacher provided materials:  

  • Assorted small beakers, scoopulas, and graduated cylinders for test reactions
  • Balances and weigh boats
  • Temperature probes and Vernier lab quest OR thermometers
  • Zip-block baggies in 3 different sizes: snack, sandwich, and quart size
  • Twist-ties
  • Various chemicals, including:
  • Sodium chloride
  • Activated charcoal
  • Calcium chloride
  • Iron filings
  • Rice
  • Water
  • 5% acetic acid
  • Sodium bicarbonate
  • Other available substances that generate exothermic reactions. (If you think of another selection of chemicals based on your own research, check with the teacher for availability.)
  • Poster board, markers/pens/colored pencils

Please note that you will only get the opportunity to create 2 prototypes due to limited supplies. Plan out your design carefully the first time and then make sure you learn as much as you can before you test again since that will be ALL.

Safety

  • Always wear safety goggles when handling chemicals in the lab.
  • Wash your hands thoroughly before leaving the lab.
  • Follow the teacher’s instructions for cleanup of materials and disposal of chemicals.

Procedure

Throughout this project, you will be keeping track of your design progress in your Activity Log (at the end of this document). At the end of this project, you will submit this log, along with your final product, an advertising poster for your product, and a reference list.

  1. In your Activity Log, start to brainstorm a list of personal/primary knowledge and secondary knowledge (obtained through research) relating to how to design your handwarmers. You can add to this list as you come up with new ideas throughout the project. This could include materials you’d like to use, substances that absorb heat well, exothermic reactions and the chemicals involved, etc. For any secondary knowledge you use, cite the sources you referenced on a separate sheet of paper.
  2. Sketch your initial design plan for your handwarmer in the Design Drawings section. (It’s ok if this plan changes before you make your final product – in fact, it’s likely to happen!) Label all parts including chemicals, quantities, a balanced chemical equation for the reaction that occurs, system/surroundings, other materials being used, and the type of energy used to generate heat. There is a place for you to draw your initial model, list any adjustments you make, and draw a final model.
  3. Verify your materials and design with your instructor. Once you have gotten approval for your design, start testing! Be sure to create appropriate data tables and record all data (substances, masses, temperatures, etc.) in your Activity Log.
    1. If you would like to do some preliminary tests of any reactions before you make your first prototype, you may use small amounts of chemicals (~5 g) in the provided beakers to confirm that your energy source is viable. You can use your results to determine how much you might want to scale up based on the temperature reached by your test reaction.
    2. You can design your initial prototype without the actual packaging/fabric you will advertise your product in, but you will need to test at least your final product in the packaging/fabric you plan to use.
    3. You can test 2 prototype designs before putting together and testing a final product, for a total of 3 sets of trial data. Remember that you need the product to maintain a temperature of 30-40oC for at least 5 minutes, so you should collect at least that much data per trial.
  1. After each trial, perform the calculations appropriate to your energy source (specific heat capacity, enthalpy of reaction, etc.) in the Calculations section of your Activity Log to determine the amount of energy produced by your handwarmer in each trial.
  2. Graph your temperature vs. time data in the Analysis section for each trial.
  3. Finalize your design and sketch and label it in the Design Drawings section of your Activity Log. Prepare final product for submission.
  4. Create an advertising poster for your product. Your poster should include:
    1. A creative, descriptive name for your product.
    2. A statement about why the manufacturing company should want to make your product – what makes it special, unique, better than other options, etc.
    3. A brief explanation of the chemical processes that make your product work.
    4. A neatly drawn and fully labeled model of your final product (see steps 2, 6).
    5. The procedures you used to evaluate and finalize your product.
    6. Sample calculations to show how much energy your product generates. (You do not need to show your calculations for every trial, but a sample of each type of calculation should be included. For example, you could include all of the calculations you did for your final product test.)
    7. A data table and graph showing your temperature and time data for your two trials and final product. This should demonstrate that your product meets the design criteria (i.e. it reaches the target temperature, lasts at least 5 minutes, and is handheld and portable.)
  1. Complete the Reflection section in the Activity Log. Submit your completed Activity Log, final product, advertising poster, and reference list. You’re done!

Activity Log

Design Process

A. Safety Precautions

B. Materials List:

C. Personal Knowledge: Identify information you already know as it relates to handwarmers, exothermic reactions, chemicals that produce exothermic reactions, etc.

D. Secondary Knowledge: Record information you discovered through research on your project design. Cite any sources you use on a separate sheet to submit with your final project!

Design Drawings

Include notes on any modifications you plan to make to the original design drawing.

A. Original, labeled handwarmer design:

B. Make note in the space below of any updates or changes you made to your initial design and why you made them.

C. Final, labeled handwarmer design:

Testing Procedure

In the space provided below, list the steps/procedure you will use to test your prototypes and the data you will need to collect. Make sure your procedure is clear enough for someone else to be able to recreate your process.

Data

As you test your prototypes and final product, create appropriate data tables to organize your data and observations from each of your prototypes and your final product.

A. Prototype 1:

B. Prototype 2:

C. Final product:

Calculations

Use your data for each prototype and your final product to calculate the amount of energy produced by your handwarmer. Be sure to include the balanced chemical reaction that is powering your product!

A. Prototype 1:

B. Prototype 2:

C. Final product:

Analysis

Create a graph showing your temperature and time data for your two prototypes and final product.



Reflection

In two or three paragraphs, reflect on what you learned through this project, addressing the following questions:

  • How much did your final design change from your original design? Why did you make the adjustments you made?
  • If you had more time and resources to continue to refine your product, what improvements would you investigate?
  • What types of experts might you hire to help you continue to develop and market your product?
  • What have you learned about the engineering process throughout this project?