Conservation of Energy

Neck Wrap

High School

Student teams design hot or cold, portable, neck wrap packs using the engineering design process. In addition, students prepare a written report that includes graphs of the time versus temperature data, analyze the activation energy, develop a model to illustrate the changes in total bond energy that occur during the reaction, and give a class presentation utilizing digital media.


Printed Material

  • 1 Student Handout: Neck Wrap (per student, group, or class)


  • 1 Computer with Internet access (per group)
  • 2 Beaker, 250 mL (per group)
  • 1 Thermometer (per group)
  • 1 Timing device (per group)
  • 1 Scissors (per group)
  • 1 Goggles (per student)
  • 1 Balance, digital (per group)


  • Acetic acid (quantity per group request)
  • Calcium chloride (quantity per group request)
  • Magnesium sulfate (quantity per group request)
  • Sodium carbonate (quantity per group request)
  • Water (quantity per group request)
  • Bag, plastic, resealable, quart-size (quantity per group request)
  • Tape, masking (quantity per group request)
  • Assorted construction materials:
  • Children’s stretch knee-high socks
  • 9 Oblong (not round) latex balloons
  • Tape (medical, electrical, duct)
  • Resealable plastic bags (various sizes)
  • Rubber bands
  • Small or large spout funnel
  • Press and seal wrap, container


Student Handout: Neck Wrap


  1. Student Handouts can be printed individually for student use, as a reusable class set, or assigned online.
  2. Assemble construction materials and chemicals.


  1. Some students may have special material requests that should be considered.
  2. Because student groups specify the quantity of chemicals needed, have on hand large quantities of each of the chemicals.
  3. The design procedure:
  • Review the engineering design process with students who have not practiced this skill before.
  • Students should have their steps listed in their lab journals.
  • Students will present their design to the class.
  • Time needed: 2-3 days
  • Discuss the Student Handout.
  • Complete as specified.
  • Grade model according to EDP rubric.

21st Century Skills Addressed: Collaboration

During this task, students are expected to demonstrate their ability to collaborate during their design process.

The Engineering Design Process

The Challenge

Work as a team of research chemists in a medical supply company to design a cold or hot, portable, neck wrap pack. You will use the data you have compiled to design this pack for treating minor injuries.

Criteria and Constraints

  1. Pack: The pack must be portable, intended for one-time use, and designed in such a way that it will only change temperature when the user activates the mixing of components. The components must comprise a combination of two or more of the following: acetic acid, calcium chloride, magnesium sulfate, sodium carbonate, and water.
    1. For a hot neck wrap, the temperature must increase to 30oC but not to more than 40oC.
    2. For a cold neck wrap, the temperature must decrease to 15oC but not to less than 10oC.
  2. Materials: Test to determine which chemicals to use for the pack. Once this is established, continue testing to determine the best amount and ratio of each chemical. You are only allowed to test in increments of 5, 10, 15, and 20 g of each reactant to determine the amount of chemicals needed. Remember, the more chemicals you use, the more expensive the product will be. Once your team has decided on the chemicals and the correct amounts needed, check with the other teams that have the same type of pack and come to a consensus on how much of each chemical is needed.
  3. Prototype: Each team should design a pack according to specifications and the amount of each chemical needed. You may use resealable plastic bags provided by your teacher or other materials of your choice. Once you have a final design, have it approved by your teacher, collect the materials, and create the prototype.
  4. Presentation: The presentation of your proposed pack must include a diagram or model to illustrate the changes in total bond energy that occurs when the pack is activated and either an endothermic or exothermic chemical reaction occurs. The presentation must also utilize digital media to enhance understanding and add interest.

Use your lab journal to record all of your steps and observations.

  1. What is the problem (challenge)? (State the problem in your own words.)

Introduce the design challenge and define the problem.

Discuss the criteria for the design challenge.

The experiment must include all investigation materials, safety precautions, and procedures used so that anyone can replicate the investigation.

Students should test their experimental designs as needed.

Data should be collected and analyzed mathematically.

  1. Explore and research the problem.
    1. List what you know and what you need to know.
    2. Research portable, cold or hot, (chemical) neck wraps.

Research and explore the problem.

Remind students that engineers usually work in groups or teams so that many different ideas can be generated and combined to come up with one great idea. Divide the class into groups.

Give each group a copy of the design challenge along with the rubric.

Make sure the materials needed to complete the lab are in a central location that groups can access as needed.

Allow sufficient in-class time for groups to complete their lab procedures and calculations.

Have a presentation time during which each group shares their ideas and findings (optional).

  1. Brainstorm and design a solution to the problem.
    1. Draw two prototypes of your design and all its parts. (Use criteria to help you.)
    2. Choose which prototype to make. (Use argumentation and discourse within your group to decide this.)
    3. Identify what materials you will use. Develop a testing method to determine which chemicals to use. (Remember the material constraints previously listed.)
      1. You may need to brainstorm and share ideas with other teams.
      2. Gather the necessary materials to make your prototype (either from purchasing these items or recycling items from home or school).

Brainstorm and design a solution to the problem.

Give students time to brainstorm and design.

Make sure students have created a materials list and established safety precautions and procedures before they proceed.

Assist students as needed.

  1. Build, test, and analyze your design.
    1. How will you construct your prototype?
    2. What formulas and calculations will you use to mathematically construct this model?
    3. Analyze how the structures are related to making a neck pack.
    4. Each team should design a pack according to specifications and the amount of each chemical needed. You may use resealable bags provided by your teacher or other materials of your choice. Once you have a final design, have it approved by your teacher and create the prototype.

Build, test, and analyze the model.

Monitor as the students complete the design process.

Ask questions and redirect thinking as necessary.

Be sure they answer the questions on the design process.

  1. Improve or redesign and retest the solution.
    1. Are the assembly procedures easy enough for others to follow?
    2. What errors could have been made during collection of research data? How can you improve this data-gathering technique?
    3. Were you able to create a prototype of a neck pack with all the criteria? If not, what changes do you need to make to your design?
    4. Retest your prototype.

Improve or redesign and retest the solution.

Give the groups time to analyze their criteria on the design process.

Assist the students in redesigning and retesting their investigation as needed.

  1. Present and share your solution.
    1. Create a presentation that includes digital media. The presentation should include the following:
      • A graph from your final data table with time on the x-axis and the activation energy identified.
      • The time the reaction takes to reach the minimum or maximum temperature.
      • A diagram or model illustrating the changes in total bond energy that occur when the pack is activated.
      • Identification of the reaction as endothermic or exothermic.
      • An account of any unexpected events in your research.
    2. Decide how you will share your solution with the teacher or class.
    3. Discuss who will talk about what you discovered.
    4. Conclude with a class discussion.

Present and share your solution.

Allow time for each group to present their results.

Let other groups ask questions. Discuss as desired.

Complete the group rubric for each group. Discuss with students.

Hold a post-activity discussion for students to evaluate their solution and make notes for improvement.

Post-Activity Discussion

To evaluate your solution, answer the following questions:

  1. What was the best solution to the problem? Explain.
  2. What could have been done differently?
  3. What can you add to your solution to make it better?

Answers to all post-activity discussion questions will vary, but students should support their answers with evidence and reasoning.