## Reflection: Staircase of Complexity Evaluating Chemical Expressions - Section 1: Introduction

I was really hesitant to start the unit with this lesson. In a way, it seemed like the work for students was too easy. It turned out that I was glad that I did, for a few different reasons.

First, this was the first lesson in the stoichiometry unit. This unit, I know from previous experience, is going to be very challenging for many students. Building students’ confidence is important so that kids don’t get lost and demoralized at the beginning. Most students were able to find success with this skill.

This is not to say that I want students to feel more accomplished by giving them easy tasks. In fact, simple expressions were easy for students, but once expressions with multiple subscripts and a coefficient were thrown in the mix, students struggled a bit. I believe that I met students exactly at their zone of proximal development—in other words, I met them where they were and moved their understanding along without traumatizing them.

This skill—evaluating chemical expressions—is important because they will need to be able to comfortably do it if they are going to be able to balance chemical equations. In short, I am glad I took the time with this foundational skill. I suspect it will actually save me time and students frustration going forward.

Starting at the Beginning
Staircase of Complexity: Starting at the Beginning

# Evaluating Chemical Expressions

Unit 5: Stoichiometry
Lesson 1 of 8

## Big Idea: Subscripts indicate how many atoms for an element are in a compound, and coefficients indicate the quantity of molecules or formula units. Multiply the coefficient by the subscripts to know how many atoms of each element are contained in a chemical express

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60 minutes

### Keith Wright

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