This unit builds toward the following NGSS Performance Expectations (PEs):

Physical Science PEs

• MS-PS2-1 Apply Newton’s Third Law to design a solution to a problem involving the motion of two colliding objects. [Clarification Statement: Examples of practical problems could include the impact of collisions between two cars, between a car and stationary objects, and between a meteor and a space vehicle.] [Assessment Boundary: Assessment is limited to vertical or horizontal interactions in one dimension.]
• MS-PS-2-2 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. [Clarification Statement: Emphasis is on balanced (Newton’s First Law) and unbalanced forces in a system, qualitative comparisons of forces, mass and changes in motion (Newton’s Second Law), frame of reference, and specification of units.] [Assessment Boundary: Assessment is limited to forces and changes in motion in one dimension and in an inertial reference frame and to change in one variable at a time. Assessment does not include the use of trigonometry.]
• 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. [Clarification Statement: Emphasis is on descriptive relationships between kinetic energy and mass separately from kinetic energy and speed. Examples could include riding a bicycle at different speeds, rolling different sizes of rocks downhill, and getting hit by a wiffle ball versus a tennis ball.]

• MS-ETS1-2 Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.
• MS-ETS1-3 Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.

The following PE will be developed over three OpenSciEd units: OpenSciEd Unit 6.1: Why do we sometimes see different things when looking at the same object? (One-way Mirror Unit), OpenSciEd Unit 7.1: How can we make something new that was not there before? (Bath Bombs Unit), and OpenSciEd Unit 8.2: How can a sound make something move? (Sound Unit). This unit will address only the mechanical inputs that transmit signals to the brain through touch. The other units will address electromagnetic and other mechanical inputs (sound) and chemical inputs as well as the connection to signals processing in the brain. This unit, however, does make an important connection to how those signals are stored as memories and how damage to particular structures (axons on neurons) can cause memory loss in concussions.

• MS-LS1-8. Gather and synthesize information that sensory receptors respond to stimuli by sending messages to the brain for immediate behavior or storage as memories. [Assessment Boundary: Assessment does not include mechanisms for transmission of this information.]

This unit helps develop the following elements of Disciplinary Core Ideas (DCIs):

PS2.A: Forces and Motion

• For any pair of interacting objects, the force exerted by the first object on the second object is equal in strength to the force that the second object exerts on the first, but in the opposite direction (Newton’s third law).
• The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.
• All positions of objects and the directions of forces and motions must be described in an arbitrarily chosen reference frame and arbitrarily chosen units of size. In order to share information with other people, these choices must also be shared.

PS3.A: Definitions of Energy

• Motion energy is properly called kinetic energy ; it is proportional to the mass of the moving object and grows with the square of its speed.

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.
• Sometimes parts of different solutions can be combined to create a solution that is better than any of its predecessors.

ETS1.C: Optimizing the Design Solution

• Although one design may not perform the best across all tests, identifying the characteristics of the design that performed the best in each test can provide useful information for the redesign process—that is, some of those characteristics may be incorporated into the new design.

LS1.D: Information Processing

• Each sense receptor responds to different inputs (electromagnetic, mechanical, chemical), transmitting them as signals that travel along nerve cells to the brain. The signals are then processed in the brain, resulting in immediate behaviors or memories.

Besides the disciplinary core ideas that are part of the foundation boxes for the target PEs in this unit, additional connections to the following DCIs are also developed and used in this unit:

PS3.B: Conservation of Energy and Energy Transfer

• When the kinetic energy of an object changes, there is inevitably some other change in energy at the same time.

PS3.C: Relationship Between Energy and Forces

• When two objects interact, each one exerts a force on the other that can cause energy to be transferred to or from the object.

While this unit engages students in multiple SEPs across the lesson-level performance expectations for all the lessons in the unit, there is one focal practice that this unit targets to support students’ development in a learning progression across the 8th grade year for the SEPs:

• Planning and Carrying Out Investigations

In addition, there are three supporting practices that students will utilize over the course of the unit:

• Analyzing and Interpreting Data
• Constructing Explanations and Designing Solutions
• Engaging in Argument from Evidence

This unit is designed to be taught at the start of 8th grade. If it is taught in 6th or 7th grade, be prepared to provide students greater support in the following SEPs. For more detailed information about the focal Science and Engineering Practices in this unit, read the unit front matter in the Teacher Edition. 

While this unit engages students in multiple CCCs across the lesson-level performance expectations for all the lessons in the unit, there are four focal CCCs that this unit targets to support students’ development in a learning progression for the CCCs across the 8th grade year:

• Systems and system models
• Energy and matter
• Structure and function
• Stability and change

For more detailed information about the focal Crosscutting Concepts in this unit, read the unit front matter in the Teacher Edition. 

Which elements of the Nature of Science are developed in the unit?

• Science investigations use a variety of methods and tools to make measurements and observations. (NOS-SEP)

How are they developed?

• Students use their fingers as force sensors and a peak force collar to measure the contact forces on two colliding objects, and they use a variety of materials such as a rubber band to measure the amount of friction from different surfaces and dissect various cushioning materials.  They collect data using push-pull force scales, rulers, slow motion videos, reflected laser beams, and computational simulations.

This unit uses two anchors, one to drive student questions and investigations in the first two lesson sets off the unit, and one to drive student questions and engagement in the use of engineering ideas and the iterative design process in the last third of the unit. This unit begins with students considering national statistics on the frequency and cost of cell phone breakage. Students share situations in which they have seen cell phones break. Students then contrast these situations with other situations where something else collided with another object and either did break or, surprisingly, did not break. Students then attempt to identify the factors that contribute to damage occurring in some collisions and not others, as well as try to explain what is happening during the collision that causes some items to become damaged in a collision, when others are not. Students then develop a Driving Question Board (DQB) to guide future investigations.

This introduction, using a commonly broken and widely used device, allows students to engage in the investigation of ideas regarding energy and forces in a collision. The ideas of deformation and breaking point examined in Lesson set 1 apply widely to phone use, as some collisions result in damage while others surprisingly do not. In Lesson set 2, students also have the ability to re-examine how different collisions can lead to damage or no damage on their devices.

Lesson set 3 re-anchors students thinking about the question of why some phones still break when in protective cases. They identify an object of their choice to design protection for in a collision, they define related criteria and constraints for such design solutions and they develop initial models for why their solutions would affect the outcome of a collision. Students then add new questions to their Driving Question Board (DQB) to guide future investigations.

Each OpenScied unit’s anchoring phenomenon is chosen from a group of possible phenomena after analyzing student interest survey results and consulting with external advisory panels. We also chose cell phone breakage as the first anchoring phenomenon for this unit for these reasons:

• This anchor ranked higher than the top alternative (related to bike helmets) in a pre-field release student survey.
• +80% of teenagers own cell phones, and those who don’t are around classmates who do. Nearly all students, therefore, have multiple interactions with people on a daily basis who have these devices , even if they do not own one themselves.
•  A subsequent piloting of this anchor confirmed that witnessing the type of phenomena referenced in the anchor, some sort of collision that caused someone’s cell phone to get damaged, was an extremely common occurrence.
• Cell phones are devices that people commonly buy protective cases for.
• Two pre-field tests pilots of the cell phone damage) anchor produced driving question boards that had a majority of the students’ questions on them and ideas for investigations to answer those questions, which were anticipated by the unit development team, and were specifically targeted in the field test version of the storyline.

We chose a re-anchor around a design problem for an object of the students choice for these reasons:

• One important aspect of engaging in the engineering design process, is to define what the problem is. Positioning students as the ones who define for themselves where the problem exists and what might benefit from a solution, positions them in a more genuine problem-definition context. Subsequent interviews with potential users of such a solution also provided an opportunity for students to involve community members for their perspectives to determine important criteria for their design solution.

This unit is broken into three lesson sets each of which help make progress on a sub-question related to the driving question for the entire unit. Lessons 1-6 focus on developing science ideas about force interactions between colliding objects. Lessons 6-10 focus on the relationship between forces and energy transfer in collisions. Lessons 11-16 focus on design solutions to protect an object of their choice in a collision and how the structure of materials can mitigate the damage that a collision can cause.

This unit is designed to be taught as the first unit of 8th grade. It is designed to be taught after students have experienced the Cup Design Unit and Healing Unit. As such, work in this unit can leverage ideas about the particle nature of matter, how energy can be transferred through particle-level collisions (conduction), how neurons work together to transfer signals from our senses to our brain. 

This unit is designed to be taught prior to OpenSciEd Unit 8.2: How can a sound make something move? (Sound Unit). That unit will leverage ideas about how forces transfer energy across a system and that all solid matter can be elastically deformed in a collision that are developed in this unit. It is also designed to be taught prior to OpenSciEd Unit 8.3: How can a magnet move another object without touching it? (Magnets Unit). That unit will leverage ideas about how every force is part of a force pair, that are two equal and opposite forces on two different objects.

This is the first 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 the Cup Design Unit, supplemental teaching of the following would be required:
  • Energy transfer as the result of two colliding objects at the particle level.
  • Understanding of the role of independent and dependent variables, along with controlled variables, in an investigation.
  • What criteria and constraints are, and how they can be used to inform design decisions.

• If taught before the Tsunami Unit, supplemental teaching of the following would be required:
  • What a stakeholder is, and the role of stakeholders in the iterative design process

In general, this unit is taught using a conceptual approach to describing the relationship among force, mass, and change in motion during collisions, students need only have experience with qualitatively reasoning about positive and negative associations (e.g., as force increases, change in motion increases; but as mass increases, change in motion from a given force decreases). But because the focus of MS-PS3-1 is on quantitative understanding of the relationship of the kinetic energy of an object to the mass of an object and to the speed of an object, students will need to leverage the following experiences from grade 7 Common Core Math Standards math to use in this unit in Lessons 7 and 10:

In lesson 7, students will be working with unit rates and ratios. By the beginning of 8th grade, students should be well versed in how to do this calculation. It will be leveraged in Lessons 7 and 10 of this unit when students recognize that the relationship between mass and kinetic energy is directly proportional. Such a relationship is one they have encountered in graphs many times in Common Core mathematics since 6th grade. Recognizing the relationship between speed and kinetic energy as nonlinear will also be straightforward. But describing the change in kinetic energy as being related to the square of the speed of an object will be challenging. Students will have encountered working with squared relationships in 6th grade in finding the surface area of a cube with sides of length s, and in 8th grade they will be working with squaring the side lengths of a right triangle in their work with the Pythagorean theorem. Coordinate with your math teachers to determine where you students will be at in their familiarity with thinking about relationships like these.

• In lesson 7 students calculate and use a type of ratio called a scale factor. They will use this idea again in the lesson 10 assessment and potentially again in lesson 16 as they develop a scale model of their designs. Students will have encountered this concept before in math class in one or both of these contexts:

• 7.G.A.1 Solve problems involving scale drawings of geometric figures, including computing actual lengths and areas from a scale drawing and reproducing a scale drawing at a different scale.
• 7.RP.A.2 Recognize and represent proportional relationships between quantities.

• There are multiple connections between the work students will be doing in Lesson 7 and the work they will be doing in math class this year (grade 8). These include the following:

• 8.F.B.5 Describe qualitatively the functional relationship between two quantities by analyzing a graph (e.g., where the function is increasing or decreasing, linear or nonlinear).

• 8.EE.A.1 Know and apply the properties of integer exponents to generate equivalent numerical expressions.

In lesson 4, students are introduced to lines of best fit in Lesson 4. They see an example of such a line again in the Lesson 10 assessment. Students do not have to have encountered this idea in previous mathematics instruction. Lesson 4 assumes that this may be the first time students encountered this idea.

The following are example options to shorten or condense parts of the unit without completely eliminating important sensemaking for students:

• Since in some ways, lesson sets 1 and 2 are anchored in explaining why sometimes get damaged when they hit each other and other don’t and lesson 3 is a re-anchor that focuses on designing protective devices for objects that we want to protect from getting damaged in a collision, one natural end point for the unit would be at the end of lesson 10, which is the end of lesson set 2.

To extend or enhance the unit, consider the following:

• Lesson 3: Consider letting students investigate the deformation of a table and other rigid materials in small groups using the laser setup. If this option is utilized, consider all proper safety precautions when using glass with students, such as safety goggles, gloves for potential sharp edges, and proper distribution and cleanup procedures that minimize encounters with any potential broken glass or other materials. See the materials preparation section of this lesson for more guidance.
• Lesson 3: Add in additional slow-motion videos in areas of student interest, such as a football making contact with the ground for classrooms that have several students engaged in football.
• Lesson 4: Expand the investigation to allow multiple groups to test multiple conditions. This would involve an increased number of materials and increased class time.
• Lesson 5: Allow students to spend more time at each investigation station. Ask students to test out each station with increased mass, increased speed, and with a variety of moving and non-moving carts.
• Lesson 6: Ask students to also revisit the related phenomena. Ask students to pick a related phenomena and explain the outcomes of the related phenomena (damage, no damage) using our science ideas. At this point, students should be able to construct a partial explanation for their related phenomena.
• Lesson 10: Ask students to once again revisit their related phenomena and attempt to explain the outcomes of the collisions. At this point, students should be able to explain the forces on each object and the energy transfer that occurs in the collision.
• Lesson 12: Consider allowing students to test a complete CD case in addition to a section of CD case plastic. Allow students to explain why a CD case that has space for air between the cover and backing reduces peak force more than a section of plastic.
• Lesson 16: Conduct the optional 16 iterative design process.
• Lesson 16, option 2: Expand the iterative design process by involving those from the community to share their own personal protective design issues and allow students to develop a real-world solution to a problem within the community. Consider holding a design fair where the community can explore student’s designs and offer feedback.

• Michael Novak, Unit Lead, Northwestern University
• Susan Kowalski, Field Test Unit Lead, BSCS Science Learning
• Zoë Buck Bracey, Writer, BSCS Science Learning
• Joel Donna, Writer, University of Wisconsin – River Falls
• Shelly Ledoux, Writer, The Dana Center at University of Texas – Austin
• Dawn Novak, Writer and Reviewer, BSCS Science Learning
• Whitney Smith, Writer, BSCS Science Learning
• Tara McGill, Review, Northwestern University
• Christina Schwarz, Unit Advisory Chair, Michigan State University
• Thomas Clayton, Teacher Advisor, Columbia Middle School, Berkeley Heights, NJ
• Amanda Leighton, Teacher Advisor, Haddonfield Middle School, Haddonfield, NJ
• Katie Van Horne, Assessment Specialist

BSCS Science Learning

• Stacey Luce, Editorial Production Lead and Copyeditor
• Valerie Maltese, Marketing Specialist & Project Coordinator
• Renee DeVaul, Project Coordinator
• Chris Moraine, Multimedia Graphic Designer

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.

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.