To check for misconceptions, I had students answer a couple of questions in an in-class simulation. After picking a students in class, I asked, "How could (specific student) increase his/her gravitational potential energy?" Since my students are middle school students, it didn't take long for someone to suggest: "Stand on the table." This first step told me that students did indeed have a grasp of gravitational potential energy. I know from other assessments that there are some students who still have not internalized this, but they are getting there.
For the second step, I asked students to apply the law of conservation of energy: "Where did that extra gravitational potential energy come from? We can't create energy so it must have come from somewhere." This is where I heard crickets, then tentative guesses such as: "His potential energy was added to the potential energy of the table." My initial thoughts were confirmed. Students would need practice working with transfer of energy to deepen their understanding of it. After some missteps, the class finally arrived at an acceptable path that the energy could have traveled to become gravitational potential energy.
What are the lessons here? How does this connect to NGSS? The biggest lesson is one that Paige Keeley has been teaching us for years: misconceptions need to be identified and addressed. This can only happen by eliciting the misconceptions through conversation or some other kind of formative assessment. Had I not taken the time to question my students, I could have quickly explained the law of conservation of energy and moved on. Students would have been exposed to it and could have memorized it, but their actual thoughts/beliefs would not have changed.
The second lesson is that change takes time. This one-time event is not enough to cause students to change their thoughts about how energy is transferred. It will take multiple exposures and multiple opportunities to think deeply about how the law of conservation of energy applies to situations that are relevant to my students. Luckily, we are about the begin building paper roller coasters which will allow my students to analyze many transfers of energy (provided that I ask the right questions).
The NGSS connection? Even as I'm typing this up, I'm realizing that students have seen the crosscutting concept, flow of energy and matter before. When we worked with photosynthesis and cellular respiration, students saw the flow of energy and matter. We even took the opportunity to trace the energy in a human back to its ultimate source, the sun. This past experience can be combined with our current study to reinforce the flow of energy and to help students realize relationships across the science disciplines.
**For more information about how students develop conceptual understanding, see this video from Smithsonian. It's animated, but it is intended for science teachers. And it's based on the latest research in learning.