How can a process increase product yield after equilibrium is reached?
Submit: An evidence record, explanation and revision.
Related lesson: Chemical Reactions and Stoichiometry
This is a teacher-led extension beyond the short lesson. The task supplies a performance opportunity; completion alone does not certify mastery, full NGSS coverage or state alignment.
Teacher review guideBuild the idea
At dynamic equilibrium, forward and reverse reaction rates are equal; both reactions continue. For A + B ⇌ C at fixed temperature, adding a reactant or removing product can drive a net forward change until a new equilibrium is reached. A catalyst helps reach equilibrium faster but does not change its equilibrium composition.
Science / engineering practice
Constructing explanations and designing solutionsCore idea
Equilibrium responds to changed conditionsCrosscutting concept
Stability and changeEvidence and model inputs
Invented process model at fixed temperature: baseline delivers 40 product units per batch for cost 10; extra A delivers 55 for cost 14; selective C removal delivers 60 for cost 16; catalyst alone reaches the baseline sooner but still delivers 40 for cost 12. Design goal: at least 50 product units with cost at most 15. Units describe a hypothetical process, not industrial data.
Keep actual observations, published findings and invented model cases labeled separately. If a source or required equipment is unavailable, pause that part with a teacher; do not invent results.
Materials and preparation
Paper, graph paper or spreadsheet, and the linked readings.
Grade-level scope
Qualitative equilibrium reasoning; do not require equilibrium-constant calculations.
Do the work
- Model forward and reverse events with particle sketches before equilibrium.
- Apply the goal to all four options and identify which currently qualifies.
- Refine the product-removal plan by proposing a specific cost reduction, then state what new evidence is needed before calling it feasible.
- Explain the particle-level response to adding A or removing C.
- Evaluate why the catalyst-only proposal fails this yield goal despite a possible timing benefit.
Learner worksheet
Write on paper or type here and print. Entries stay in this page’s memory and are lost when you leave or reload; they are not saved or submitted.
Check your reasoning
- Which supplied option meets both constraints?
- Does equilibrium mean reactions stop?
- Does removing product destroy conservation of matter?
- Is a proposed cheaper separator already proven?
Teacher review guide
Review the actual deliverable and discuss the reasoning. For each criterion, use 0 when evidence is absent or fundamentally incorrect, 1 when partly supported with a material error or omission, and 2 when accurate, supported and complete for the stated task. Maximum 8 points is a task score, not a proficiency certification. Give feedback and allow revision.
- Models a dynamic equilibrium correctly.
- Uses criteria to compare process changes.
- Explains a shift using reactant or product changes.
- Refines a design and identifies evidence needed to validate it.
Answer guidance for the reasoning checks
Which supplied option meets both constraints?
Extra A: 55 units at cost 14.
Does equilibrium mean reactions stop?
No. Forward and reverse rates are equal.
Does removing product destroy conservation of matter?
No. Count removed product outside the reaction vessel.
Is a proposed cheaper separator already proven?
No. It needs cost and performance evidence.
Access, support and extension
Offer read-aloud support, labeled diagrams, larger print or an oral/recorded explanation while preserving the scientific reasoning. A partner or teacher can handle physical manipulation while the learner plans, records and interprets. Use a teacher-provided measured dataset only when its provenance and limitations are explicit; it does not replace conducting an investigation when that is the assessed practice. For greater independence, remove prompts and ask learners to compare a second explanation or test another justified revision.
Sources and standard reference
- Official NGSS HS-PS1-6 performance expectation — inspect the practice, core idea, crosscutting concept and assessment boundary.
Instructional text and hypothetical cases are original. Linked source readings supply published evidence where specified. Teachers should judge fit with their course and state requirements.