7.2 Chemical Reactions & Energy
How can we use chemical reactions to design a solution to a problem?
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Unit Summary
In this 21-day unit, students are introduced to the anchoring phenomenon—a flameless heater in a Meal, Ready-to-Eat (MRE) that provides hot food to people by just adding water. In the first lesson set, students explore the inside of an MRE flameless heater, then do investigations to collect evidence to support the idea that this heater and another type of flameless heater (a single-use hand warmer) are undergoing chemical reactions as they get warm. Students have an opportunity to reflect on the engineering design process, defining stakeholders, and refining the criteria and constraints for the design solution.
In the second lesson set, students develop their design solutions by investigating how much food and reactants they should include in their homemade heater designs and go through a series of iterative testing and redesigning. This iterative design cycle includes peer feedback, consideration of design modification consequences, and analysis of impacts on stakeholders. Finally, students optimize their designs and have another team test their homemade heater instructions.
![video thumbnail](https://img.youtube.com/vi/P7uWNQO-XNU/mqdefault.jpg)
Unit Examples
Additional Unit Information
Next Generation Science Standards Addressed in this Unit
Performance Expectations
This unit builds towards the following NGSS Performance Expectations (PEs):
- MS-PS1-6: Undertake a design project to construct, test, and modify a device that either releases or absorbs thermal energy by chemical processes.
- MS-ETS1-2: Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.
- MS-ETS1-3: Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.
- MS-ETS1-4: Develop a model to generate data for iterative testing and modification of a proposed object, tool, or process so that an optimal design can be achieved.
Disciplinary Core Ideas
This unit expands students’ understanding of energy in chemical reactions in the context of engineering design. These are the Grades 6-8 DCI elements:
PS1.B: Chemical Reactions
- Some chemical reactions release energy, while others store energy.
ETS1.B: Developing Possible Solutions
- Models of all kinds are important for testing solutions.
- A solution needs to be tested and then modified on the basis of the test results in order to improve it.
- There are systematic processes for evaluating solutions with respect to how well they meet the criteria and constraints of a problem.
- Sometimes parts of different solutions can be combined to create a solution that is better than any of its predecessors.
ETS1.C: Optimizing the Design Solution
- Although one design may not perform the best across all tests, identifying the characteristics of the design that performed the best in each test can provide useful information for the redesign process—that is, some of the characteristics may be incorporated into the new design.
- The iterative process of testing the most promising solutions and modifying what is proposed on the basis of the test results leads to greater refinement and ultimately to an optimal solution.
You can view the placement of this OpenSciEd Unit 7.2 and associated units within the OpenSciEd Scope and Sequence document
Science and Engineering Practices
- Planning and Carrying Out Investigations
- Constructing Explanations and Designing Solutions
Crosscutting Concepts
- System and System Models
- Matter and Energy
Connections to the Nature of Science
Which elements of the Nature of Science are developed in the unit?
- Science investigations use a variety of methods and tools to make measurements and observations. (NOS-SEP)
How are they developed?
- Students consider what observations to collect as data that will serve as evidence to confirm a chemical reaction is happening.
Unit Placement Information
What is the anchoring phenomenon and why was it chosen?
For the anchoring phenomenon, students begin by thinking about how they would heat up food without having typical methods available. They see images from a real situation, after Superstorm Sandy in New York, during which people were given Meals, Ready-to-Eat (MREs) that can heat up food by just adding water. The class explores the flameless heater from the MRE in action, which seems like some kind of chemical process or possibly a chemical reaction. Students develop an initial model to consider how a flameless heater works, but they also notice some problems with prepackaged MREs. In order to solve some of the identified problems, the class decides to help people in situations in which typical heating methods aren’t available to heat up food by designing a homemade flameless heater with instructions that others could follow.
Each OpenScied unit’s anchoring phenomenon is chosen from a group of possible phenomena after analyzing student interest survey results and consulting with several external advisory panels. The MRE flameless heater was chosen to anchor this unit for the following reasons:
- Homemade Heater Unit directly builds upon Disciplinary Core Ideas from grades 6-8 regarding chemical reactions OpenSciEd Unit 7.1: How can we make something new that was not there before? (Bath Bombs Unit), which comes just prior to this unit in the OpenSciEd Scope and Sequence. Students leverage their ideas about chemical reactions to figure out that energy transfer happens when substances undergo chemical reactions. It also builds directly upon the Disciplinary Core Ideas (DCIs) from OpenSciEd Unit 6.2: How can containers keep stuff from warming up or cooling down? (Cup Design Unit) as we use the model developed hete about energy transfer at the particle level to build a systems level model of energy transfer on which to base our homemade flameless heater designs.
- This unit includes a substantial engineering component with multiple iterations on design. Designing any device in the classroom can be costly and material intensive, but designing the instructions for a homemade flameless heater allowed for fewer specialized materials and an easier design process compared to other options.
- In thinking about who they may be helping with this homemade flameless heater, students realize that anyone in their community (including their own family and friends) are also the stakeholders and could potentially need to use an MRE at some point. Feedback from the field test indicated that students identified with the need for a device that could warm food as they reflected on times they lost power for extended periods of time due to snow storms, floods, or other large scale power losses.
- This anchor gives students to engage directly with the community about what they are learning, and an authentic opportunity to get stakeholder feedback. Students survey family, friends and other members of the community to get some initial ideas about the experience people have with MREs, any other initial ideas or questions, as well as feedback on designs and instructions.
How is the unit structured?
The unit is organized into two main lesson sets, each of which help make progress on a sub-question related to the driving question for the entire unit. In Lessons 1-5, students are focused on figuring out ideas related to defining and refining the problem of designing a flameless homemade heater. Then, in Lessons 6-10, students use these ideas to optimize the design of a flameless homemade heater.
Where does this unit fall within the OpenSciEd Scope and Sequence?
This is the second unit in 7th grade in the OpenSciEd Scope and Sequence and it directly builds off the Disciplinary Core Ideas (DCIs), Crosscutting Concepts (CCCs), and Science and Engineering Practices (SEPs) developed in the preceding unit. In OpenSciEd Unit 7.1: How can we make something new that was not there before? (Bath Bombs Unit) (Unknown material with identifier: ca:n), the first unit of the 7th grade course, students establish an understanding that substances can be identified by their properties, substances are made up of molecules, which are made up of atoms, and sometimes when substances are combined, a chemical reaction occurs which causes the molecules to break apart and rearrange resulting in a new substance. In this unit, students apply these ideas to identify that energy is transferred to or from a system of substances when a chemical reaction is happening, then they use this knowledge to design a solution to help people be prepared to warm their food in an emergency.
Additionally, this unit builds from the Disciplinary Core Ideas (DCIs), Crosscutting Concepts (CCCs), and Science and Engineering Practices (SEPs) developed in the 6th grade unit OpenSciEd Unit 6.2: How can containers keep stuff from warming up or cooling down? (Cup Design Unit). In that unit, students develop and refine models to explain how objects can change temperature when matter moves out of a system, and when energy is transferred between objects. Students develop particle models early on in the unit to explain what happens to the water inside the cup to warm up, they also develop particle models to show how gases, liquids, and solids at high temperature move in comparison to low temperature. We use those ideas as well as the system modeling developed in that unit to build our initial models describing how the MRE works, and eventually use that and add our new ideas about energy transfer related to chemical reactions to design our homemade flameless heaters.
What modifications will I need to make if this unit is taught out of sequence?
This is the second unit taught in 7th grade in the OpenSciEd Scope and Sequence. If this unit is taught earlier in the middle-school curriculum, the following modifications would need to be made:
- Introducing the students to the concept of a Driving Question Board and a shared set of classroom norms. This would not be necessary if taught after other OpenSciEd units.
- Supplemental teaching of several PEs from 6.2 Thermal Energy:
- MS-PS1-4: Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
- MS-PS3-3: Apply scientific principles to design, construct, and test a device that either minimizes or maximizes thermal energy transfer.
- MS-PS3-4: Plan an investigation to determine the relationships among the energy transferred, the type of matter, the mass, and the change in the average kinetic energy of the particles as measured by the temperature of the sample.
- MS-PS3-5: Construct, use, and present arguments to support the claim that, when the kinetic energy of an object changes, energy is transferred to or from the object.
- MS-ETS1-1: Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.
- Supplemental teaching of several PEs from 7.1 Chemical Reactions & Matter:
- MS-PS1-1: Develop models to describe the atomic composition of simple molecules and extended structures. Chemical formulas of substances are used in this unit. It is assumed that students understand the DCI element that substances are made from different types of atoms, which combine with one another in various ways.
- MS-PS1-2: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred. This unit does not teach students how to identify if a chemical reaction has occurred. Students use this previous knowledge and apply it to new phenomena to determine if the chemical processes they observe are, in fact, chemical reactions. Students may start to recognize chemical reactions as early as Lesson 1 while observing the MRE heater, which gives off hydrogen gas as a product. This is an indication that the MRE heater is undergoing a chemical reaction, which students should recognize from their prior experiences in 7.1 Chemical Reactions & Matter.
- Make sure students have the necessary common-core 6th-grade math concepts regarding ratios and proportions. For more details, see the following section about prerequisite math concepts necessary for the unit.
What mathematics is required to fully access the unit’s learning experiences?
In Lesson 3, students calculate the maximum temperature change for three different amounts of reactants. They report this change in temperature using positive and negative numbers to show the increase or decrease from the starting temperature. Prerequisite math concepts that may be helpful include the following:
- CCSS.MATH.CONTENT.6.NS.C.5 Understand that positive and negative numbers are used together to describe quantities having opposite directions or values (e.g., temperature above/below zero, elevation above/below sea level, credits/debits, positive/negative electric charge); use positive and negative numbers to represent quantities in real-world contexts, explaining the meaning of 0 in each situation.
In Lesson 4, students determine the relative proportion of each reactant that showed the optimal temperature change by calculating the percentage of each reactant. Prerequisite math concepts that are needed include the following:
- CCSS.MATH.CONTENT.6.RP.A.3.C Find a percent of a quantity as a rate per 100 (e.g., 30% of a quantity means 30/100 times the quantity); solve problems involving finding the whole, given a part and the percent.
In Lesson 6 and Lesson 9, students will scale up the amount of reactants to use in their homemade heaters but maintain the same proportion of reactants they found to be most efficient in previous testing. Furthermore students then scale down amounts to test their prototypes. Prerequisite math concepts that may be helpful include the following:
- CCSS.MATH.CONTENT.6.RP.A.3 Use ratio and rate reasoning to solve real-world and mathematical problems, e.g., by reasoning about tables of equivalent ratios, tape diagrams, double-number line diagrams, or equations.
- CCSS.MATH.CONTENT.6.RP.A.3.A Make tables of equivalent ratios relating quantities with whole-number measurements, find missing values in the tables, and plot the pairs of values on the coordinate plane. Use tables to compare ratios.
In Lesson 6 and Lesson 9, students will need to calculate the correct amounts of water beads and plain water to make “water bead soup” as a proxy for food in their prototype heaters. The ratio of water beads to plain water is 1:3 (1 part water beads to 3 parts water), and students will measure the beads and water in grams. Prerequisite math concepts that may be helpful include the following:
- CCSS.MATH.CONTENT.6.RP.A.1 Understand the concept of a ratio and use ratio language to describe a ratio relationship between two quantities. For example, “The ratio of wings to beaks in the bird house at the zoo was 2:1, because for every 2 wings there was 1 beak.” “For every vote that candidate A received, candidate C received nearly three votes.”
- CCSS.MATH.CONTENT.6.RP.A.3.D Use ratio reasoning to convert measurement units; manipulate and transform units appropriately when multiplying or dividing quantities.
In Lesson 9, students may want to redesign their homemade heaters to increase the surface area of the reactant system that is in contact with the food system. While mathematical calculation of surface area will not be necessary for these design improvements, it may be helpful if students understand the concept of surface area. As such, the following standard may provide a connection point:
- CCSS.MATH.CONTENT.7.G.B.6 Solve real-world and mathematical problems involving area, volume, and surface area of two- and three-dimensional objects composed of triangles, quadrilaterals, polygons, cubes, and right prisms.
How do I shorten or condense the unit if needed? How can I extend the unit if needed?
The following are example options to shorten or condense parts of the unit without eliminating important sensemaking for students:
- Lesson 2: If you are unable to carry out the flameless heater demonstrations in your classroom https://youtu.be/1irEGXQDC_8 and https://youtu.be/8r6nYNhzx08 are available for students to make the necessary observations.
- Lesson 7: To keep the focus of sharing and feedback on identifying successes, make careful decisions about which groups are paired together. Pair teams that had similar levels of success in Lesson 6 and avoid pairing teams with the highest functioning and lowest functioning designs together. To save time, determine and post partner teams before class. Additionally, students may be reluctant to ask questions in preparation to give the required feedback. Provide students with some sentence or question starters to help them begin the discussion in a timely manner.
- Lesson 9: You can use the time during which teams are revising their how-to instructions to assign partner teams. Consider pairing teams that had similar levels of success in Lesson 6 and avoid pairing teams with the highest functioning and lowest functioning designs together. To save time, determine partner teams before class. Additionally in Lesson 9 there is an opportunity for students to individually complete a teamwork self-assessment, if you are running short on time it would be appropriate to assign the self-assessment as home learning.
To extend or enhance the unit, consider the following:
- Lesson 1: If time allows, you may want to provide more context about the development of MREs. The video available at https://www.kcet.org/shows/meals-ready-to-eat/natick-labs-the-science-behind-military-food explains how the US military’s goal with MREs is to not only provide proper nutrition to the troops but to give them a sense of comfort and home with this food, as well.
- Lesson 2: Students may question temperature change if the amount of hand warmers used changed. Give students an opportunity to test additional hand warmers, and give students an opportunity to wonder about and investigate the cost of this option to get adequate temperature changes to warm food.
- Lesson 3: Students may notice that there are a lot of bubbles on the steel wool when it is submerged in vinegar. Vinegar is used to clean the surface of the steel wool by removing oils left on it after manufacturing. Iron in the freshly cleaned steel surface slowly starts to react with vinegar to produce hydrogen. As an extension activity, students can collect some of the gas and conduct a flammability test as in OpenSciEd Unit 7.1: How can we make something new that was not there before? (Bath Bombs Unit). The root killer and aluminum foil in saltwater reaction also produces small hydrogen bubbles due to the sodium chloride disrupting the oxide layer on the foil; though, this may not be noticeable since it will occur inside of the closed cup. Therefore, this reaction could also be subject to a flammability test. The bubbles produced by the reaction of baking soda and vinegar contain carbon dioxide gas that will extinguish a flame and therefore is not flammable.
- Lesson 6: Like developing classroom norms, you could choose to have students develop their own list of teamwork expectations. Knowing that they will be working together to create a successful design, what do they need from each other to make that happen? As students suggest expectations, you can fill them in on a shared document (such as the digital version of Teamwork Self-Assessment) and then print that out to add to their notebooks and to use as a self-assessment at the end of this lesson (and again in Lesson 9).
Unit Acknowledgements
Unit Development Team
- Holly Hereau, Unit Lead, BSCS Science Learning
- Tara McGill, Reviewer, Field Test Unit Lead, Northwestern University
- Renee Affolter, Writer and Reviewer, PD Design, Boston College
- Arlene Friend, Writer, Von Tobel Middle School
- Sue Gasper, Writer, University Of Illinois Urbana‐champaign
- Meghan McCleary, Writer, University Of Illinois Urbana‐champaign
- Betty Stennett, Writer, BSCS Science Learning
- Wayne Wright, Writer, BSCS Science Learning
- Joel Donna, Conceptual design, University of Wisconsin – River Falls
- Michael Novak, Conceptual design, Northwestern University
- Katie Van Horne, Assessment Specialist, Concolor Research
- Joi Merritt, Unit Advisory Chair, James Madison University
- T.J. Smolek, Advisory Team, Michigan Department of Education
- Angela Webb, Advisory Team, James Madison University
- Christy Krenek, Advisory Team, New Mexico Public Education Department
- Hope Brown, Advisory Team, Prairie Lakes Area Education Agency
- David Fortus, Expert Advisor, Weizmann Institute of Science
Production Team
BSCS Science Learning
- Maria Gonzales, Copyeditor, Independent Contractor
- Kate Herman, Copyeditor, Independent Contractor
- Stacey Luce, Copyeditor and Editorial Production Lead
- Renee DeVaul, Project Coordinator and Copyeditor
- Valerie Maltese, Marketing Specialist & Project Coordinator
- Chris Moraine, Multimedia Graphic Designer
- Kate Chambers, Multimedia Graphic Designer
Unit External Evaluation
EdReports
EdReports awarded OpenSciEd an all-green rating for our Middle School Science Curriculum in February 2023. The materials received a green rating on all three qualifying gateways: Designed for the Next Generation Science Standards (NGSS), Coherence and Scope, and Usability. To learn more and read the report, visit the EdReports site.
NextGenScience’s Science Peer Review Panel
An integral component of OpenSciEd’s development process is external validation of alignment to the Next Generation Science Standards by NextGenScience’s Science Peer Review Panel using the EQuIP Rubric for Science.
We are proud that this unit has earned the highest score available and has been awarded the NGSS Design Badge. You can find additional information about the EQuIP rubric and the peer review process at the nextgenscience.org website.
Unit standards
This unit builds toward the following NGSS Performance Expectations (PEs) as described in the OpenSciEd Scope & Sequence:
- MS-PS1-6
- MS-ETS1-2
- MS-ETS1-3
- MS-ETS1-4
Reference to kit materials
The OpenSciEd units are designed for hands-on learning and therefore materials are necessary to teach the unit. These materials can be purchased as science kits or assembled using the kit material list.