During this lesson students will develop a model of the garbage disposal system that includes the system’s components and how those components interact.

This will be the first lesson in which students develop a model. Modeling will play a central role in the unit. Because modeling may be a new science practice for students, start by guiding the class in developing part of the model together.

“Today we are going to talk about how the garbage from our homes, school, and community get to the landfill. We are going to create a model that represents the garbage system.”

“We are going to create part of the system together and then I am going to ask you to work in your triad to create the remaining parts of the system.”

Post on the board “Home” and “Home Garbage” (on sticky notes).

“Let’s think about the garbage we make at home. What can you tell me about your garbage at home? What do you do with your garbage at home?” (Throw it away, put it in a garbage can.)

“What happens to the garbage in the cans?” (It goes into bigger garbage and recycling cans outside.)

Add “Outside Garbage” and “Recycling Cans” to the board. Use arrows to connect the components in the model (see example display below).

“What happens to the garbage and recycling outside?” (The garbage truck picks it up.)

Add “Garbage Truck” to the model.

“What happens to the garbage in the garbage truck? What about the recycling?” (It goes to the landfill or recycling center.)

Add “Landfill” and “Recycling Center” to the board.

Example display (see red outline for home garbage system):

“All of the parts you just named are called components. When components work together it makes a system. So what we just created on the board represents a system for handling our garbage at home.”

Following the home garbage example, ask triads to identify the components of the school and community garbage systems.

Assign each triad one of the systems—either school or community garbage—to focus on and give each group a small piece of chart paper and sticky notes. Students should work in their triads with sticky notes to determine the different components of the system and use arrows to represent how those components work together.

Bring the class together and ask the “School Garbage” and “Community Garbage” groups to share the components and how they work together. Post these components on the board next to the Home Garbage Model you created with the class.

Once the three systems are posted, ask students to make observations about the systems. If students do not notice the similarities and differences between the systems, prompt them to make note of this.

Describe what the class created: “On the board, we made a model that describes several garbage disposal systems: the school lunch garbage, home garbage, and other community garbage (e.g., from parks). This display shows the components of each system. Arrows connect one component to another when the components work together. It also shows how garbage flows into, through and, in some cases, out of one component system and into another.”

“When scientists and engineers decide on a system and show the components and their interactions, that’s a system model. Our class made a system model today that contains several systems that connect together, making one larger system.”

Tell students: “Thinking about garbage handling as a system might have made you think of more questions. Let’s take a few minutes to think about any new questions or ideas that you have.”