Look for: Consider whether students are connecting idea…

15.B.2 Develop a consensus model for explaining two mechanisms for energy transfer into a system, and design features that minimize energy transfer into a system.

Through this discussion, be mindful of formatively assessing the different dimensions that students are engaging with:

• Consider whether students are connecting ideas about particle motion and kinetic energy to the different mechanisms of energy transfer via conduction (particle collisions) or radiation (light absorption).
• Consider whether students are able to use model representations that they’ve agreed upon to represent their thinking. When students enter the design challenge in the next lesson, they will need to be able to model their design choices and how they minimize energy transfer without the scaffolding you are providing here.
• Consider whether students are using energy as a way of explaining the flow into the cup system.

• If students are struggling with disciplinary core ideas, focus them on the previous models that they developed, especially from Lessons 6, 11, and 14.
• If students are struggling with modeling their thinking, use questioning to elicit their ideas and then brainstorm what kinds of representation they feel would best represent those ideas in a model.

Cue students to focus on kinetic energy of particles and energy from light as a way to track the energy flow into the cup systems

Develop a consensus model for how radiation warms a drink. Move the class to the first set of posters about what happens when light interacts with matter (or move the posters to the Scientists Circle). Say, One of the things we weren’t sure about was why putting something shiny over the outside of the cup slowed the temperature increase in the liquid. We thought it was reflective, which is important, but we weren’t sure how light actually warms things up. Let’s take a look at these models and your comments and see if we know enough now to explain this.

Read the agreement side of the poster set’s comparison T-chart out loud, or ask a student to read it out loud to the class. After each idea has been read, revoice the idea to the class and ask if we all agree that this belongs in our consensus model. If the class agrees, have them add the idea to their handouts using the agreed-upon representations. You may want to project a version of the handout on document camera, or sketch one on a whiteboard or chart paper, as the class agrees on what to include in the consensus model.✱

Then move on to the disagreements. After each disagreement, ask the class if this disagreement needs to be resolved to explain how preventing light from getting in slows down or minimizes energy transfer into the cup. If the majority of the class says yes, ask the groups who disagreed to share their reasoning. Use questions to clarify their ideas. Ask other students whose reasoning they find more convincing, and add those ideas to the chart paper at the front of the room.

After all the ideas have been read, ask someone to summarize why something shiny slows the temperature increase in a cool liquid. Ask the class if they agree, and if anybody would like to add to this explanation.✱

At this point, the list of things we figured out should include:

• When light shines on something, it might reflect off particles, transmit between particles, or transfer energy into particles (absorption).
• If the light transfers energy into the particles, the energy may end up as kinetic energy, meaning that the particles will speed up. If this happens to a lot of particles in a liquid, the liquid will warm up.
• You may choose to model these ideas on a piece of chart paper. Have students add these to their Progress Tracker before moving on, telling them to leave more than half the remaining space in it to add some other key ideas.

Repeat the process for a consensus model for why air pockets keep a drink cooler for longer. Move to the second set of posters about conduction in materials with air pockets. Say, One of the things we weren’t sure about was why using materials like styrene, koozies, or coffee cup sleeves is able to minimize the temperature change in a liquid. Let’s take a look at this model and see if we know enough now to explain this.

• Review the T-chart for agreements.
• Discuss and resolve areas of disagreement.
• As you discuss, develop a model that incorporates the important ideas.

At this point, the list of things we figured out should include:

If a solid material has air pockets, there are fewer particles in the air pockets for energy to transfer between through particle collisions. If a material is solid all the way through, there are more particles to collide with one another, so the energy will conduct more easily.

Repeat the process for a consensus model for why double walls keep a drink cooler for longer. Move to the third set of posters about how double-walled containers work. Say…