Our garbage journey continues! On August 27 students made individual predictions about what will happen to the properties of the four rubbish materials (apple, banana, plastic, foil) over time. They also predicted what will happen to the weight of their landfill bottle over time. Half of the students had created a closed system and the other half had created an open systems.

I introduced the idea of system models, which they had used earlier. Scientists make system models to show the important components of the system and how those components interact. Students were asked to create a model that would include the system components and tell the story of what is going on in the bottles at each time point. Today we create the model for time point 1. The model for time point 1 includes a group prediction of what will happen to the rubbish materials.

On August 30 students examined one of the group’s models to notice its features. Models are thinking tools that scientists use to describe, explain, and predict. We will use our models to keep track of how the system changes. Later, we will use the models to support our explanations of the phenomenon.

Developing and using models is one of the science and engineering practices. We discussed how we are using these practices because we are scientists. Then we reviewed the list of 8 science and engineering practices:

• Asking questions and defining problems
• Developing and using models
• Planning and carrying out investigations
• Analyzing and interpreting data
• Using mathematics and computational thinking
• Constructing explanations and designing solutions
• Engaging in argument from evidence
• Obtaining, evaluating, and communicating information

We noticed which of these we have already used in science class. We have already used at least 3 of these!

We went back to our questions to pick another thing to investigate.

Our big question is How does the rubbish system work? One component of the rubbish system is a rubbish truck. What happens in a rubbish truck?

We watched this video clip about what happens in a garbage truck. The rubbish truck crushes materials. I asked What happens to materials when they are crushed? Does the kind of material change? Does the weight change? How could we investigate this in our classroom?

Students suggested we could weigh things before and after crushing them to see what happens to weight. Then we brainstormed ideas of what we could crush. Students contributed ideas and then we narrowed the list down to items that were things easy to get and safe. We decided on cardboard, paper, wood sticks, soda can, and aluminum foil.

The last activity for the day was an exit slip that asked students about the landfill bottle investigation. Students were asked to describe the system they were investigating, its components, the data they were collecting, and what questions the investigation will help answer. I collected these formative assessments.

Upon reviewing these assessments, I found that many students did not use the concepts of systems and components correctly yet. I plan to add an additional activity to reinforce this idea before we use systems again in class.