Argument from collision evidence

2.B.1 Construct an argument supported by empirical evidence and scientific reasoning to support a model showing that changes in motion of colliding objects (connected to subsystems) result from energy transfer between them (cause) and changes in the shape of those objects result from force(s) between them (cause).

Students making arguments that leverage prior knowledge about changes in kinetic energy, energy transfer, and/or forces as a mechanism or interaction causing one or more of these outcomes. It's OK if students reference only one of these rather than all of them.

If students struggle with identifying any mechanisms or interactions for these causes, suggest that they will share ideas in a moment to come to consensus on these ideas, and that you will check in again on their thinking when you collect Progress Trackers at the end of the period. Collect and review students’ Progress Trackers at the end of the period to see if students are referencing ideas related to kinetic energy, energy transfer, or forces that they may not have mentioned here.

Suggested prompt

Sample student response

I think you’ve talked about energy before in science class. Can we take a moment and think back to 6th and 7th grade and brainstorm different places where you talked about or represented energy like this before?

We’ve talked about energy transfer in One-way Mirror Unit, Cup Design Unit, Everest Unit, Homemade Heater Unit, Maple Syrup Unit, Palm Oil Unit.

Do you see any connections among how energy is represented in the different systems in these units?

Answers may vary.

Even though we’ve used energy thinking to explain very different phenomena related to a cup of liquid warming up, the formation of a cloud or an air mass, heating up food, or where the energy an orangutan needs to live comes from, we have always been talking about energy transfers into or out of systems. What energy transfers do you recall between systems?

• We talked about a chemical reaction system transfering energy to our food system in Homemade Heater Unit.
• We talked about energy transfer from a particle moving fast hitting a particle moving slowly and transferring energy in Cup Design Unit.

Energy is transferred from the food sources that orangutans eat (fruits) into their bodies when they consume those foods. Palm Oil Unit

• Additional responses may vary.
• Explicitly talk about energy transfer versus forces way of thinking. If students don’t bring up forces, introduce this line of reasoning to bridge from energy transfer thinking to forces using the prompts below.

Suggested prompts

Sample student responses

Follow-up questions

In the OpenSciEd Unit 6.2: How can containers keep stuff from warming up or cooling down? (Cup Design Unit) you thought about what happens in collisions between small particles. How did you describe what happened to the energy of each particle in such collisions?

• Moving particles transfer energy into and out of systems during collisions.
• That sounds like an energy transfer perspective way of thinking.

Was shape change of the particles something you were considering too?

No.

OK, so let’s consider some of the objects we saw change shape in this collision investigation.

If the CD case was motionless on a table, what would you have to do to it with your hand to change its shape?

Squeeze it.

Push on it.

Poke it.

Smash it.

That sounds like you would have to bring your hand into contact with it and push on it. That sort of thinking is a way of talking about what is happening from a force perspective.

Say, We are raising issues about what is happening using ideas about pushing, which is a way of talking about interactions in the system using forces, and we are also describing what is happening to the motion of the objects using ideas about changes in energy, which is a way of talking about energy transfer. Both seem like important ideas we could use to explain what is happening in a collision. And scientists find both are really helpful ways to explain certain types of changes. Sometimes it seems more helpful to describe what is happening using forces, and sometimes it is more helpful to describe what is happening using energy transfer. But each is a different way of thinking about interactions within a system and between systems. Let’s clarify what we are talking about with respect to forces and what we are talking about with respect to energy transfer.

Ask questions to clarify what is meant by pushing and energy transfer and add the words force and energy to the Word Wall.

Suggested prompt

Sample student respon…