Design Must-Haves

9.B Optimize performance of a design that represents systems and energy flows between systems by revising and retesting to incorporate characteristics of the most promising solutions.

justification for amounts of reactants used

reasons for any changes in materials

trade-offs considered when calculating cost and so forth

trade-offs based on Consequences Chart

an Energy Transfer Model

a particle-level model

If a team’s redesign does not include reasoning for their changes, remind the team to go back and look at their Consequences Chart from Lesson 8. Suggest that they base their changes on prior test results (theirs or another group’s). If any team is struggling to show the transfer of energy from the reaction system to the food system on their Energy Transfer Model or the particle-level model of their design, refer to the initial consensus model you made as a class (which shows how the MRE heater’s particles were moving) and the Energy Transfer Model from Lesson 3 (which includes a particle-level model) and ask the team to consider how those might be similar to their models. Teams could also think about how their material and reactant changes impacted their Energy Transfer Model from Lesson 6. If these students experienced OpenSciEd Unit 6.2: How can containers keep stuff from warming up or cooling down? (Cup Design Unit), referring to the models that they drew of the energy transfer happening with their cups may also be helpful.