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Build a Recycling-Sorting Machine

4 reviews


Grade Range
Group Size
2-3 students
Active Time
2 hours
Total Time
2 hours
Area of Science
Key Concepts
Forces, magnetism, engineering design
Ben Finio, PhD, Science Buddies

a recycling sorting machine. A plastic cup holds paper clips and shreds of paper. A vertical cardboard tube supports a downward carboard ramp. The ramp feeds into a plastic bottle lined with magnets, which feeds into a plastic cup.

Build a Model Recycling Sorting Machine


In this lesson plan, your students will build their own recycling sorting machines that use various methods, like magnets or puffs of air, to separate shreds of paper from paper clips. This lesson is inspired by the real-world engineering challenge of separating various materials, like paper, plastic, and metals, that get combined in single-stream recycling programs.

Learning Objectives

NGSS Alignment

This lesson helps students prepare for these Next Generation Science Standards Performance Expectations:
This lesson focuses on these aspects of NGSS Three Dimensional Learning:

Science & Engineering Practices
Constructing Explanations and Designing Solutions. Apply scientific ideas or principles to design an object, tool, process or system.

Engaging in Argument from Evidence. Evaluate competing design solutions based on jointly developed and agreed-upon design criteria.
Disciplinary Core Ideas
PS2.B: Types of Interactions. Electric and magnetic (electromagnetic) forces can be attractive or repulsive, and their sizes depend on the magnitudes of the charges, currents, or magnetic strengths involved and on the distances between the interacting objects.

Forces that act at a distance (electric, magnetic, and gravitational) can be explained by fields that extend through space and can be mapped by their effect on a test object (a charged object, a magnet, or a ball, respectively).

ETS1.B: Developing Possible Solutions. There are systematic processes for evaluating solutions with respect to how well they meet the criteria and constraints of a problem.
Crosscutting Concepts
Influence of Science, Engineering, and Technology on Society and the Natural World. The uses of technologies and limitations of their use are driven by individual or societal needs, desires, and values; by the findings of scientific research; and by differences in such factors as climate, natural resources, and economic conditions.


 materials to build a recycling sorting machine

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Background Information for Teachers

This section contains a quick review for teachers of the science and concepts covered in this lesson.

Single-stream recycling programs allow us to mix all of our recyclables—like paper, plastics, and metals—in a single container. These containers are collected by trucks and transported to Materials Recovery Facilities (MRFs). These facilities use a variety of machinery, combined with some manual sorting by humans, to separate all the different materials (Figure 1). For example, large magnets can pull ferrous metals (like tin cans) away from the rest of the waste. Puffs of air can blow lighter materials upward while heavier materials fall down. Sieves allow small objects to fall through the holes while larger objects keep going. Multiple videos listed in the Additional Background section show MRFs in action.

 Diagram of a materials recovery facility

Diagram showing the steps at a materials recovery facility. Mixed waste is unloaded from a truck. It then goes through a magnetic separator, air sorter, sieves to separate materials of different sizes, and some manual sorting as the materials are sorted into different bins.

Figure 1. Diagram of a materials recovery facility.

In this lesson plan, students will build their own miniature materials recovery facility. They will focus on separating just two materials: paper clips and shreds of paper. Multiple methods—like magnets, puffs of air, or manual sorting (or a combination thereof)—can be used to do this. Students will experiment with different methods and build a machine to sort the two materials as quickly as possible.

This lesson can be used to teach students about magnetic forces and magnetic fields. For example, students will notice that the magnets exert forces on each other, and the paper clips, even when they are not in direct contact. They can explore what parameters have effects on these forces, such as the distance or orientation of a magnet relative to the paper clips. See the tutorial linked in the Additional Background section for more information about magnetism.

Finally, you can also use this lesson to spur conversation about the pros and cons of recycling, and ask students to do further research about recycling as a homework assignment or follow-up project. See the references in the Additional Background section to get started.

Prep Work (15 minutes)

Engage (10 minutes)

Explore (1 hour)

Reflect (15 minutes)


Make Career Connections

Lesson Plan Variations

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