8.3 Forces at a Distance
How can a magnet move another object without touching it?
This unit launches with a slow-motion video of a speaker as it plays music. In the previous unit, students developed a model of sound. This unit allows students to investigate the cause of a speaker’s vibration in addition to the effect.
Students dissect speakers to explore the inner workings, and engineer homemade cup speakers to manipulate the parts of the speaker. They identify that most speakers have the same parts–a magnet, a coil of wire, and a membrane. Students investigate each of these parts to figure out how they work together in the speaker system. Along the way, students manipulate the components (e.g. changing the strength of the magnet, number of coils, direction of current) to see how this technology can be modified and applied to a variety of contexts, like MagLev trains, junkyard magnets, and electric motors.
Additional Unit Information
Next Generation Science Standards Addressed in this Unit
This 6-week unit builds towards the following NGSS Performance Expectations (PEs):
- MS-PS2-3: Ask questions about data to determine the factors that affect the strength of electric and magnetic forces.
- MS-PS2-5: Conduct an investigation and evaluate the experimental design to provide evidence that fields exist between objects exerting forces on each other even though the objects are not in contact.
- MS-PS3-2: Develop a model to describe that when the arrangement of objects interacting at a distance changes, different amounts of potential energy are stored in the system.
- MS-PS2-2*: Plan an investigation to provide evidence that the change in an object’s motion depends on the sum of the forces on the object and the mass of the object.
- MS-PS3-1*: Construct and interpret graphical displays of data to describe the relationships of kinetic energy to the mass of an object and to the speed of an object.
- MS-PS3-5*: Construct, use, and present arguments to support the claim that when the kinetic energy of an object changes, energy is transferred to or from the object (p. 61).
*These performance expectations are developed across multiple units. This unit reinforces or works toward these NGSS PEs that students should have previously developed or will develop more fully in future units. In the OpenSciEd Scope and Sequence, PS2-2, PS3-1, and PS3-5 are first built in Unit 8.1. In this new context, students are considering the same relationships, but in the context of forces that are at a distance. Students will continue to explore these relationships in the context of gravity in unit 8.4.
Disciplinary Core Ideas
The unit expands students’ understanding of forces and energy transfer, which include these grades 6-8 DCI elements:
PS2.B: Types of Interactions
- Electrical 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. (MS‑PS2‑3)
- Forces that act at a distance (electrical, 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). (MS‑PS2‑5)
PS3.A: Definitions of Energy
- A system of objects may also contain stored (potential) energy, depending on their relative positions. (MS-PS3-2)
- When two objects interact, each one exerts a force on the other that can cause energy to be transferred to or from the object. (MS-PS3-2)
The parts of the DCI elements that are not developed in this unit are crossed out. In the OpenSciEd Scope and Sequence, students will develop an understanding of gravity in OpenSciEd Unit 8.4. Electricity is treated as an extension opportunity within this unit. The placement of this OpenSciEd Unit 8.3 and associated units within the OpenSciEd Middle School Scope and Sequence.
Science & Engineering Practices
- Asking Questions and Defining Problems: This unit intentionally develops students’ engagement in this practice through the use of sentence frames to help them ask investigable questions about specific cause and effect relationships, and to construct scientific hypotheses from these questions that include a mechanistic account of an observable relationship between variables.
- Planning and Carrying Out Investigation: This unit intentionally develops students’ engagement in this practice. Students use hypothesis-building cause-effect sentence frames to identify variables they need to test to evaluate their hypothesis. In Lessons 10-11, students plan and conduct an investigation collaboratively as a class and in small groups to produce data to serve as the basis for evidence for describing cause and effect relationships between factors in a speaker system.
- Developing and Using Models: This practice is key to the sensemaking in this unit. Students develop and use models throughout the unit to try to explain how some parts of the speaker are moving without being in contact with the rest of the system, beginning in Lesson 1. They use their models to test cause and effect relationships to describe how the speaker works.
- Analyzing and Interpreting Data, and Using Mathematics and Computational Thinking are also key to the sensemaking in this unit. In Lessons 10-11, students analyze data from their investigations in order to identify and describe the nonlinear relationships between various factors and magnetic force.
- The following practice is also key to the sensemaking in this unit:
- Constructing Explanations and Designing Solutions.
Focal Crosscutting Concepts
- Cause and Effect: This unit intentionally develops this crosscutting concept through the application of cause-effect sentence frames. Students routinely identify, test, and use relationships to explain change throughout.
- Systems and System Models: This crosscutting concept is key to the sensemaking in this unit.Students spend the unit breaking down and modeling the speaker system, describing and explaining the system in terms of its components and interactions
- Energy and Matter: This crosscutting concept is key to the sensemaking in this unit. Students figure out and apply the idea that energy can be transferred in various ways and between objects in order to explain how the speaker system works.
- The following crosscutting concepts are also key to the sensemaking in this unit:
- Scale, Proportion, and Quantity
Connections to the Nature of Science
Which elements of the Nature of Science are developed in the unit?
- Science depends on evaluating proposed explanations. (NOS-SEP)
- Scientific explanations are subject to revision and improvement in light of new evidence. (NOS-SEP)
- Science theories are based on a body of evidence developed over time. (NOS-SEP)
- A hypothesis is used by scientists as an idea that may contribute important new knowledge for the evaluation of a scientific theory. (NOS-SEP)
- The term “theory” as used in science is very different from the common use outside of science. (NOS-SEP)
How are they developed?
- Beginning in Lesson 1, students use cause-effect sentence stems to ask questions and develop hypotheses. In the third lesson set, students use hypotheses they have constructed to help identify relevant variables, and guide the design of their investigations.
- In Lesson 3 students test an explanation for how the speaker works (something is moving through the air between the magnet and coil), and quickly find that the evidence they collect does not support the explanation. They set out to come up with a revised explanation in light of this evidence.
- Beginning in Lesson 1, students use cause-effect sentence stems to ask questions and develop hypotheses. The sentence stems help students understand the nature of scientific hypotheses as proposed relationships tied to a mechanistic explanation.
- Lesson 3 provides additional guidance about the Nature of Science as students frame and test hypotheses. There is guidance on how to introduce the term, theory, as a powerful scientific explanation that explains many phenomena and is supported by a body of evidence. There is opportunity for a rich discussion on what ‘theory’ means in science as compared to outside of science.
Unit Placement Information
What is the anchoring phenomenon and why was it chosen?
In the first lesson of this unit, students watch a slow motion video of a speaker that gets them wondering about what could be causing the motion they see. They dissect a speaker as a class, and then build their own speakers with plastic cups, wire, and magnets. When they plug in their homemade speakers, they can hear music coming from a device. This set of experiences with speakers provide a rich context to elicit questions and ideas for investigations related to the nature of magnetism, electricity, forces, and motion.
The speaker anchoring phenomenon was chosen from a group of phenomena aligned with the target performance expectations based on consultation with external advisory panels that include teachers, subject matter experts, and state science administrators. The speaker was chosen for the following reasons:
- Teachers and administrators saw high relevance to students’ everyday experiences with headphones, music players, and PA systems
- Explaining how a speaker works addresses all the DCIs in the bundle at a middle school level
- Students have the opportunity to engage in hands-on dissection on day 1
- The speaker shares constituent components with many other everyday devices that students may not have noticed
- Students are motivated to test the components of the speaker system
How is the unit structured?
This unit is broken into three lesson sets, as illustrated in the graphic below. In the first lesson set (Lessons 1-6), students begin with the anchoring phenomenon routine. In the rest of the lessons in the set, students’ investigations help them figure out how a magnet and a coil of wire can interact through forces at a distance. In the second lesson set (Lessons 7-9), students’ investigations help them figure out more about these interactions, specifically, how energy transfers through electromagnets, and across the space between magnets. In the final lesson set (Lessons 10-12), students design and carry out a set of investigations that provide evidence for what factors affect the strength of magnetic fields.
Where does this unit fall within the OpenSciEd Scope and Sequence?
This is the third unit in 8th grade in the OpenSciEd Scope and Sequence. In OpenSciEd Unit 8.1: Why do things sometimes get damaged when they hit each other? (Collisions Unit) the first unit of the 8th grade course, students will have established an understanding of forces, and of the relationship between energy and forces. In OpenSciEd Unit 8.2: How can a sound make something move? (Sound Unit), students figure out the link between vibration and sound. In this unit, students apply these ideas to explain the forces and energy transfer in a speaker that result in sound.
How will I need to modify the unit if taught out of sequence?
This is the third unit in 8th grade in the OpenSciEd Scope and Sequence. Given this placement, several modifications would need to be made if teaching this unit earlier or later in the middle school curriculum. These include the following adjustments:
- If taught before OpenSciEd Unit 8.1, supplemental teaching of the definitions of forces and energy would be required, particularly in the context of physical pushes and pulls (contact forces). These ideas are fundamental to the model of forces and energy in a magnetic field that students need to build.
- If taught before OpenSciEd Unit 8.1 (or at the start of the school year), supplemental teaching of classroom norms, setting up the Driving Question Board, and asking open-ended and testable questions would need to be added. (These supports are built into 8.1.)
- If taught before OpenSciEd Unit 8.2, supplemental teaching of what a sound is and how sound travels would be required, with an emphasis on how movement back and forth creates the physical pushes necessary to move air so that sound waves can transfer energy. These ideas are fundamental to students’ understanding of the anchoring phenomenon in this unit.
What mathematics is required to fully access the unit’s learning experiences?
In this unit, students will collect, manipulate, and analyze data from several investigations. In Lesson 7 students will calculate the rate of change from data collected and organized in a table. They will interpret this rate as the speed of a cart moving along a track. Data organization and analysis in Lessons 10 and 11 include graphing tabular data in two quadrants of the coordinate plane and interpreting the meaning of data in graphs.
Prerequisite math concepts from students math classes include the following:
- CCSS.Math.Content.7.PR.1. Compute unit rates associated with ratios of fractions, including ratios of lengths, areas, and other quantities measured in like or different units.
- In their 7th grade math classes, students have experience in determining rates of change from quantities where units are different, and they frequently calculate average speed. Students also begin to algebraically manipulate the variables in the equation for speed (s = d/t) and can determine any of the three when given the other two. Helping students focus on units needed for the desired quantity will minimize errors.
- CCSS.Math.Content.6.NS.C.8. Solve real-world and mathematical problems by graphing points in all four quadrants of the coordinate plane. Include use of coordinates and absolute value to find distances between points with the same first coordinate or the same second coordinate.
- In 6th grade, students are introduced to graphing points in all four quadrants of the coordinate plane and frequently use direction as an analogy. For example, if the origin of the graph is a starting point, walking north and west would result in a location in quadrant II. In Lessons 10 and 11 students consider the symmetry of data graphed in quadrants I and IV across the y-axis. The idea of reflection across an axis is not introduced until 8th grade, so be sure to check with math colleagues about the timing of this concept.
How do I shorten or condense the unit if needed? How can I extend the unit if needed?
The following are example options to shorten or condense parts of the unit without eliminating important sensemaking for students:
- Lesson 1: The speaker dissection is best as a real-time investigation to do with your students. However, there are two alternative approaches to the speaker dissection: using a previously dissected speaker or playing a video of a speaker dissection. If you select an alternative approach, the advance preparation is different. Watch the speaker dissection video yourself to orient yourself to how you would do it as a real-time investigation with students.
- Lesson 8: In previous lessons students designed many aspects of the investigations they carried out and had a relatively long amount of time to do them. In the very short investigations students do in this lesson, the planning aspect is not the main focus of their work. And they have a very short amount of time for each investigation. This shift in focus for this lesson is because the goal of these investigations is different. Students are carrying out these investigations in order to produce data to serve as the basis for evidence that is framed around trying to figure out answers to a series of questions the class will narrow in on at different points in the lesson. These explorations do not require students to follow a predetermined procedure. In order to accomplish the goal of each investigation in a short amount of time, students will need to attend to how they communicate, cooperate, and take turns with their group members.
To extend or enhance the unit, consider the following:
- Lesson 2: Draw on students’ experiences with magnets to help them see why this content is relevant to them. Consider asking students to each bring in a magnet from their own refrigerator or locker to test in this investigation. Would one of those magnets also make the speaker work? If there is time, try it. If students bring in magnets, give some space for them to share the magnet with the class and where it came from. Is it from a family trip? Is it sent from a relative who lives elsewhere? Is it an advertisement from a local company? Is it a picture of a loved one? Use these examples to highlight how common magnets are in our lives across a variety of contexts, even when we don’t notice them.
- Lessons 8-12: These lessons include guidance on how to provide a coherent enrichment experience for students who are interested in learning more about electricity or who have met and exceeded the performance expectations. These might also be helpful if your state has standards in addition to those laid out in the NGSS related to electricity and circuits. Look for guidance with heading “Electricity extension opportunity” to find optional enrichment support over the next four lessons. There may also be optional handouts associated with this enrichment. For more details on these opportunities, see the reference document titled Electricity extension opportunity.
- All lessons: Remove scaffolds provided with Science and Engineering Practices as a way to give students more independent work with the elements of these practices.
Unit Development Team
- Zoë Buck Bracey, Unit Lead, BSCS Science Learning
- Lindsey Mohan, Field Test Unit Lead, BSCS Science Learning
- Joel Donna, Writer, University of Wisconsin River Falls
- Shelly Ledoux, Writer, The Dana Center at University of Texas – Austin
- Michael Novak, Writer, and Reviewer, Northwestern University
- Will Reed, Writer, Chicago Public Schools
- Betty Stennett, Writer, BSCS Science Learning
- Kris Grymonpre, Teacher Advisor, John W. McCormack Middle School, Boston, MA
- Thomas Clayton, Teacher Advisor, Columbia Middle School, Berkeley Heights, NJ
- Christina Schwarz, Unit Advisory Chair, Michigan State University
- Joseph Krajcik, Unit Advisory Member, Michigan State University
- Katie Van Horne, Assessment Specialist
BSCS Science Learning
- Stacey Luce, Editorial Production Lead and Copyeditor
- Valerie Maltese, Marketing Specialist & Project Coordinator
- Alyssa Markle, Project Coordinator
- Chris Moraine, Multimedia Graphic Designer
Unit External Evaluation
EdReports awarded OpenSciEd an all-green rating for our Middle School Science Curriculum in February 2023. The materials received a green rating on all three qualifying gateways: Designed for the Next Generation Science Standards (NGSS), Coherence and Scope, and Usability. To learn more and read the report, visit the EdReports site.
NextGenScience’s Science Peer Review Panel
An integral component of OpenSciEd’s development process is external validation of alignment to the Next Generation Science Standards by NextGenScience’s Science Peer Review Panel using the EQuIP Rubric for Science. We are proud that this unit has earned the highest score available and has been awarded the NGSS Design Badge. You can find additional information about the EQuIP rubric and the peer review process at the nextgenscience.org website.
This unit builds toward the following NGSS Performance Expectations (PEs) as described in the OpenSciEd Scope & Sequence:
Reference to kit materials
The OpenSciEd units are designed for hands-on learning and therefore materials are necessary to teach the unit. These materials can be purchased as science kits or assembled using the kit material list.