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react chemically in

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reactions—substances react chemically in characteristic ways. In a chemical process, the atoms that make up the original substances are
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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

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