You can search for the Evidence Statements here. You can search by Grade (I chose high school), Discipline (Physics is with Chemistry under "Physical Science") and then click "Submit" to see all of them. Depending on how your particular school or district has divided Physical Science into Chemistry and Physics the Performance Objectives you need to look at may vary. For my district I printed pages 16-27 and 30-41.
This is a screenshot of page 16 of that full file so let's break that box down. [more description is available here in a 2013 NSTA graphic called "Inside the NGSS Box] If you're already familiar with the basic box breakdown you can scroll down below the image.
The "HS-PS2-1" title means "High School Physical Science;" 2-1 is for that specific Performance Objective within this grade level discipline.
The Performance Expectation is just that, a description of what students are expected to be able to do (perform). There are often Clarification Statements and Assessment Boundary descriptions that clarify how students will be assessed. For example, these statements in this example assure us our students will only be asked about one dimensional motion and nothing approaching the speed of light.
The Science and Engineering Practices section details the skills you students should be able to apply to this problem. [Spoiler: your students will probably be using more than just these skills.] These are practices that you may want to focus on to learn this concept.
The Disciplinary Core Ideas section details which concepts are being assessed in this Performance Expectation. I like to write in my extra learning objectives into this section. For example in my forces unit I have additional learning objectives about Newton's First and Third Laws of Motion because I think those are important too.
Finally the Crosscutting Concepts section describes major themes that students should be exposed to in all their science classes throughout their years.
But ah ha! There's the new stuff. On this document there is a table titled "Observable features of the student performance by the end of the course:" that are called Evidence Statements. I find the title awkwardly worded; and have not been able to find a list of just these statements without the boxes above.
From the NGSS website: "NGSS Evidence Statements provide educators with additional detail on what students should know and be able to do. These are statements of observable and measureable components that, if met, will satisfy NGSS performance expectations."
Within the 17 page "Introduction and Overview" document (which I do actually recommend reading) I found this:
"The evidence statements, as described here, describe what teachers or assessors would observe (not infer) from successful student performance of each performance expectation (PE). The evidence statements can serve as supporting materials for the design of curriculum and assessments. In the NGSS, each PE is accompanied by a foundation box with associated practice, core idea, and crosscutting concept. The evidence statements expand this initial structure to include specific, observable components of student performance that would demonstrate integrated proficiency by using all of the necessary tenets of the practice to demonstrate understanding of the disciplinary core ideas (DCIs) through the lens of the crosscutting concepts (CCC)."
That first line says it all, Evidence Statements "describe what teachers ... would observe (not infer) from successful student performance..."
But I want to do what I want to do! [Yes I can hear you yelling at your screen.] These Evidence Statements are meant to clarify, to aid you with your lesson planning, not replace them. From the same document:
"...the evidence statements are written to provide more clarity about what the PEs ask students to demonstrate, these statements are not sufficient to replace lesson plans or assessment items; asking students to simply perform the PEs verbatim would not be useful for instruction or assessment."
So if you've felt like you've been guessing how to get your students to a point where they could meet those Performance Expectations, you know have a bit of a road map. That's a bit of relief in the last few days of July.