Oklahoma Science CH.PS1.6

ScienceGrades 9–12Matter and Its Interactions

The Standard

Refine the design of a chemical system by specifying a change in conditions that would affect the amounts of reactants or products at equilibrium.*

Oklahoma Academic Standards for Science (2026)

Teacher's field guide

What Students Need to Do: Students predict how a change in pressure, temperature, or concentration affects the amounts present at equilibrium. They choose a change that increases a target product and explain why it works.
What Mastery Looks Like: For ammonia formation, a student recommends higher pressure to increase the amount of ammonia at equilibrium. They explain that the product side has fewer gas molecules. They know a catalyst gets the system to equilibrium faster but does not change the final amounts.
Common Misconceptions: Students may think a catalyst increases the final amount of product. They may also think heating always increases product yield, even when the reaction releases heat.
How to Assess It: Exit ticket: N₂ + 3H₂ ⇌ 2NH₃ + heat. Name one change to pressure or temperature that increases the amount of ammonia at equilibrium, and explain why.

Lesson moves

Give pairs one N₂ card, three H₂ cards, and two NH₃ cards; have them compare gas molecule counts before choosing a pressure change.
Ask students to write why cooling can increase ammonia yield at equilibrium even though it slows the reaction.
Play a four-round sort: students label heating, cooling, compression, and adding a catalyst as raising, lowering, or not changing ammonia yield.
Sketch an ammonia fertilizer reactor; students mark the compressor and explain why the plant also heats the reactor.

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