react chemically in
characteristic ways. In a
chemical process, the
atoms that make up the
original substances are
regrouped into different
molecules, and these new
substances have different
properties from those of
the reactants. The total
number of each type of
atom is conserved, and
thus the mass does not
Energy and matter: matter is
conserved because atoms
are conserved in physical
and chemical processes
Develop and use a model to
describe how the total
number of atoms does not
change in a chemical
reaction and thus mass is
162 J. Krajcik et al.
have developed a ten-step process to guide teachers in developing a sequence of
lessons to build student proficiency in a bundle of PEs. While the steps are listed in a
linear fashion, in practice the lesson development process is much more iterative.
Step 1: Select PEs that work together—a bundle—to promote proficiency in
using the ideas expressed. Often the bundle will include PEs from a
single NGSS topic (see topic arrangement) or DCI (see DCI
arrangement), but a bundle could draw in PEs from other topics or DCIs.
Step 2: Inspect the PEs, clarification statements, and assessment boundaries to
identify implications for instruction.
Step 3: Examine DCI(s), science and engineering practices, and crosscutting
concepts coded to the PEs to identify implications for instruction.
Step 4: Look closely at the DCI(s) and PE(s). What understandings need to be
developed? What content ideas will students need to know? What must
students be able to do? Take into consideration prior PEs that serve as the
foundation for cluster of PEs the lessons will address.
Step 5: Identify science and engineering practices that support instruction of the
core ideas. Develop a coherent sequence of learning tasks that blend
together various science and engineering practices with the core ideas
and crosscutting concepts.
Step 6: Develop lesson level PEs. Lesson level expectations guide lesson
development to promote student learning; they build to the level of
understanding intended in the bundle of PEs.
Step 7: Determine the acceptable evidence for assessing lesson level
performances, both formative and summative.
Step 8: Select related Common Core Mathematics Standards (CCSS-M) and
Common Core Literacy Standards (CCSS-L).
Step 9: Carefully construct a storyline to help learners build sophisticated ideas
from prior ideas, using evidence that builds to the understanding
described in the PEs. Describe how the ideas will unfold. What do
students need to be introduced to first? How would the ideas and
practices develop over time?
Step 10: Ask: How do the task(s)/lesson(s) help students move towards an
understanding of the PE(s)?’’
An Illustrated Example of the Process
We will look at an example for teachers and curriculum developers to illustrate this
process. The example we have chosen comes from middle school and focuses on
students developing understanding of chemical reactions.
Step 1: Select PEs that Work Together: A Bundle—to Promote Proficiency in Using the Ideas Expressed