Science Task Screener

Task Title: Le Chatelier’s Principle: Engineering Better Chemical Reactions

Grade: High School

Date: 2024-05-20

Instructions

Criterion A. Tasks are driven by high-quality scenarios that are grounded in phenomena or problems.

i. Making sense of a phenomenon or addressing a problem is necessary to accomplish the task.

What was in the task, where was it, and why is this evidence?

  1. Is a phenomenon and/or problem present?

Yes. The anchoring phenomenon is introduced in Part 1 (Engage): the Haber process for ammonia synthesis (N₂ + 3H₂ ⇌ 2NH₃ + heat) never reaches 100% yield despite being one of the most important industrial chemical reactions in the world. The problem is framed as an engineering challenge — chemical engineers must optimize conditions to maximize ammonia output while balancing energy costs and equipment safety. This phenomenon is presented explicitly in the opening paragraph of the task.

  1. Is information from the scenario necessary to respond successfully to the task?

Yes. The task requires students to use the simulation to investigate how changing concentration, temperature, and volume/pressure shifts the equilibrium position. Students cannot answer the data collection questions (Part 2) or the sensemaking questions (Part 3) without running the simulation and recording their observations. The engineering proposal in Part 4 specifically requires students to cite evidence from their simulation data to justify each recommended condition. A student relying solely on prior knowledge of Le Chatelier’s Principle could not complete the data table or support the proposal with specific concentration and temperature values derived from the simulation.

ii. The task scenario is engaging, relevant, and accessible to a wide range of students.

Features of engaging, relevant, and accessible tasks:

Features of scenarios Yes Somewhat No Rationale
Scenario presents real-world observations [x] [ ] [ ] The task opens with the real-world fact that the Haber process feeds half the world’s population via fertilizers, yet cannot achieve full conversion — an authentic observation from industrial chemistry.
Scenarios are based around at least one specific instance, not a topic or generally observed occurrence [x] [ ] [ ] The scenario is specifically the Haber-Bosch synthesis of ammonia (N₂ + 3H₂ ⇌ 2NH₃), not a generic discussion of equilibrium reactions.
Scenarios are presented as puzzling/intriguing [x] [ ] [ ] The question “why can’t we just run it and get 100% yield?” creates cognitive dissonance — students expect reactants to fully convert, and the puzzle drives inquiry.
Scenarios create a “need to know” [x] [ ] [ ] Part 1 explicitly asks students to generate “need to know” questions about how to shift equilibrium toward products, directly motivating the simulation investigation.
Scenarios are explainable using grade-appropriate SEPs, CCCs, DCIs [x] [ ] [ ] Le Chatelier’s Principle and collision theory are grade-appropriate for high school chemistry (HS-PS1-6). The simulation concretely visualizes abstract equilibrium concepts.
Scenarios effectively use at least 2 modalities (e.g., images, diagrams, video, simulations, textual descriptions) [x] [ ] [ ] The task uses a dynamic simulation with particle animation, a Conc vs Time graph, and a Shift Indicator — three simultaneous visual modalities alongside the written task prompts.
If data are used, scenarios present real/well-crafted data [x] [ ] [ ] The simulation generates realistic equilibrium data based on the exothermic reaction’s thermodynamics (92 kJ released). Concentration values respond quantitatively to condition changes.
The local, global, or universal relevance of the scenario is made clear to students [x] [ ] [ ] The first sentence connects ammonia to global food production — “fertilizers that feed roughly half the world’s population” — making the relevance immediate and universal.
Scenarios are comprehensible to a wide range of students at grade-level [x] [ ] [ ] The equilibrium concepts are supported by visual particle animation and the Shift Indicator, which reduces the abstraction. Data table templates provide structure for recording observations.
Scenarios use as many words as needed, no more [x] [ ] [ ] The Engage section is two sentences plus bullet points. Directions are concise and procedural. No extraneous text.
Scenarios are sufficiently rich to drive the task [x] [ ] [ ] The scenario supports investigation of three independent variables (concentration, pressure, temperature) plus a culminating engineering trade-off analysis, providing richness without overwhelming.
Evidence of quality for Criterion A: [ ] No [ ] Inadequate [x] Adequate [ ] Extensive

Suggestions for improvement of the task for Criterion A:

The task could be strengthened by including a brief real-world note about actual industrial Haber process operating conditions (e.g., typical industrial plants use 400–500 °C and 150–200 atm with an iron catalyst) to heighten authenticity. A single still image or diagram of an industrial ammonia reactor would add a fourth modality. However, the scenario is already sufficient to drive the task.

Criterion B. Tasks require sense-making using the three dimensions.

i. Completing the task requires students to use reasoning to sense-make about phenomena or problems.

Consider in what ways the task requires students to use reasoning to engage in sense-making and/or problem solving.

Students must reason through multiple cause-effect relationships: (1) why adding a reactant shifts equilibrium forward even though no mechanical force is applied — this requires reasoning about collision frequency at the molecular level. (2) Why decreasing temperature increases NH₃ yield for an exothermic reaction — students must treat heat as a product in the equilibrium expression. (3) Why changing volume/pressure shifts equilibrium based on the mole ratio (4 moles of gas on the reactant side vs 2 on the product side). (4) Why the “optimal” temperature is not simply the lowest one — students must reason about the tradeoff between thermodynamic equilibrium position and kinetic reaction rate. Each of these requires active reasoning rather than recall.

ii. The task requires students to demonstrate grade-appropriate dimensions:

Evidence of SEPs (which element[s], and how does the task require students to demonstrate this element in use?)

Constructing Explanations and Designing Solutions: In Part 3, students must construct evidence-based explanations for why each condition shift occurs, using their simulation data. In Part 4, students design an engineering solution (the optimal operating conditions for a Haber process plant), specifying conditions and justifying trade-offs using collected data. The task explicitly requires them to “use evidence from your simulation data to support every claim.”

Evidence of CCCs (which element[s], and how does the task require students to demonstrate this element in use?)

Stability and Change: Students observe a system at equilibrium (stable) and then perturb it by changing concentration, temperature, or pressure. They track how the system responds (change) and re-establishes a new equilibrium (new stability). The task explicitly prompts students to observe the transition via the Conc vs Time graph and the Shift Indicator, which directly visualizes the stability-and-change dynamic. Energy and Matter: Students trace how heat energy (92 kJ released) functions as a de facto product in the exothermic reaction, and how adding or removing heat shifts the equilibrium.

Evidence of DCIs (which element[s], and how does the task require students to demonstrate this element in use?)

PS1.B Chemical Reactions: Students must understand that chemical reactions are reversible and reach equilibrium, and that changing conditions (concentration, temperature, pressure) shifts the equilibrium position. The task requires applying Le Chatelier’s Principle to predict and explain shift directions for the specific reaction N₂ + 3H₂ ⇌ 2NH₃. ETS1.C Optimizing the Design Solution: In the engineering proposal (Part 4), students must optimize their design by prioritizing criteria (yield, cost, safety, rate) and making trade-off decisions. The prompt explicitly says “balancing equilibrium yield against reaction rate” and “discuss at least one real-world tradeoff.”

iii. The task requires students to integrate multiple dimensions in service of sense-making and/or problem-solving.

Consider in what ways the task requires students to use multiple dimensions together.

The task consistently integrates dimensions. For example, in the temperature analysis: students use the simulation (SEP — using the tool to collect data) to observe how temperature changes affect NH₃ concentration (DCI — equilibrium shift), then explain the pattern using the CCC Stability and Change (the system moves from one equilibrium state to another when perturbed). In the engineering proposal, students must simultaneously apply their understanding of equilibrium (DCI PS1.B), stability and change (CCC), and design principles (DCI ETS1.C) to construct a written argument (SEP). The dimensions are not separated into discrete, unrelated questions but are woven together in each part.

iv. The task requires students to make their thinking visible.

Consider in what ways the task explicitly prompts students to make their thinking visible (surfaces current understanding, abilities, gaps, problematic ideas).

Students make their thinking visible in multiple ways: (1) The structured data table in Part 2 requires students to record both quantitative observations (concentration changes) and qualitative judgments (shift direction). (2) Part 3’s open-ended questions prompt written explanations of “why” shifts occur, surfacing students’ causal reasoning. (3) Part 4’s engineering proposal is a multi-paragraph synthesis that forces students to articulate their full chain of reasoning from data to recommendation. (4) The “need to know” questions in Part 1 surface students’ initial curiosities and gaps. These artifacts collectively reveal what students understand about equilibrium, what they misunderstand, and how they integrate concepts.

Evidence of quality for Criterion B: [ ] No [ ] Inadequate [x] Adequate [ ] Extensive

Suggestions for improvement of the task for Criterion B:

The task could be enhanced by adding a prompt for students to draw annotated particle-level diagrams showing what happens when a stress is applied (e.g., “sketch the chamber before and after adding N₂, showing how the ratio of collisions changes”). This would more directly surface molecular-level reasoning and provide additional evidence of student thinking. The current written-explanations approach is adequate but could benefit from this visual component.

Criterion C. Tasks are fair and equitable.

i. The task provides ways for students to make connections of local, global, or universal relevance.

Consider specific features of the task that enable students to make local, global, or universal connections to the phenomenon/problem and task at hand. Note: This criterion emphasizes ways for students to find meaning in the task; this does not mean “interest.” Consider whether the task is a meaningful, valuable endeavor that has real-world relevance–that some stakeholder group locally, globally, or universally would be invested in.

The task explicitly connects to global food security: ammonia fertilizers support roughly half of world food production. Chemical engineers at companies like CF Industries, Yara, and BASF routinely face the trade-offs students explore. The relevance is universal — every student eats food that may depend on Haber process fertilizers. Additionally, the energy cost and safety trade-offs connect to broader societal issues of sustainable manufacturing and industrial safety that affect communities near chemical plants globally.

ii. The task includes multiple modes for students to respond to the task.

Describe what modes (written, oral, video, simulation, direct observation, peer discussion, etc.) are expected/possible.

Students respond in multiple modes: (1) Interactive simulation manipulation — students directly control variables and observe outcomes. (2) Written data recording — completing the structured data table. (3) Written short-answer explanations — sensemaking questions in Part 3. (4) Extended written argument — the engineering design proposal in Part 4. (5) The task could be extended to include peer discussion or oral presentation of proposals. The simulation provides real-time visual feedback (particle animations, graph updates, shift indicator) as an additional non-written modality.

iii. The task is accessible, appropriate, and cognitively demanding for all learners (including English learners or students working below/above grade level).

Features Yes Somewhat No Rationale
Task includes appropriate scaffolds [x] [ ] [ ] The data table provides a structured template for recording observations. The investigation proceeds from simpler (concentration) to more complex (temperature trade-offs). Part 2 provides explicit step-by-step instructions for each experiment.
Tasks are coherent from a student perspective [x] [ ] [ ] The 5E sequence (Engage → Explore → Explain → Elaborate/Evaluate) provides a natural learning progression: first ask questions, then collect data, then make sense of it, then apply to a design challenge.
Tasks respect and advantage students’ cultural and linguistic backgrounds [x] [ ] [ ] The simulation is highly visual (particle animations, graphs, shift indicator), reducing reliance on advanced English proficiency. Scientific vocabulary (equilibrium, exothermic, concentration) is consistently used with contextual support.
Tasks provide both low- and high-achieving students with an opportunity to show what they know [x] [ ] [ ] Lower-achieving students can successfully complete the data collection and basic observations. Higher-achieving students are challenged by the engineering proposal requiring integration of multiple concepts and explicit trade-off reasoning.
Tasks use accessible language [x] [ ] [ ] Sentences are direct and procedural in Part 2, explanatory in Part 3, and open-ended in Part 4. Chemical formulas use Unicode subscripts (N₂, H₂, NH₃) for readability. The reaction equation is clearly displayed.

iv. The task cultivates students’ interest in and confidence with science and engineering.

Consider how the task cultivates students interest in and confidence with science and engineering, including opportunities for students to reflect their own ideas as a meaningful part of the task; make decisions about how to approach a task; engage in peer/self-reflection; and engage with tasks that matter to students.

By casting students as chemical engineers designing a real industrial process, the task empowers them to see themselves as practitioners of science and engineering. The simulation gives students agency — they choose which variables to test, in what order, and must make interpretive decisions. The engineering proposal requires students to defend their own design choices, building confidence in evidence-based argumentation. The global relevance (feeding the world) helps students see science as meaningful. The task could be further enhanced with a peer-review component where students evaluate each other’s proposals against a rubric.

v. The task focuses on performances for which students’ learning experiences have prepared them (opportunity to learn considerations).

Consider the ways in which provided information about students’ prior learning (e.g., instructional materials, storylines, assumed instructional experiences) enables or prevents students’ engagement with the task and educator interpretation of student responses.

The task assumes students have prior knowledge of: (1) basic chemical equations and mole ratios, (2) the concept of reversible reactions, (3) introduction to collision theory, (4) exothermic vs endothermic reactions. These are standard topics in a high school chemistry course before the equilibrium unit. The task itself teaches Le Chatelier’s Principle through investigation rather than assuming prior knowledge of it. Students who have not seen equilibrium before can still engage with the simulation and derive patterns from data. The task could be used as an introductory inquiry or as a culminating assessment — it is flexible.

vi. The task presents information that is scientifically accurate.

Describe evidence of scientific inaccuracies explicitly or implicitly promoted by the task.

The reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g) + 92 kJ is accurately represented as exothermic. Le Chatelier’s Principle is correctly applied throughout — adding reactants shifts toward products, removing products shifts toward products, decreasing temperature favors the exothermic direction, increasing pressure favors the side with fewer gas moles. The mole ratio (4 moles reactants → 2 moles products) is correct. The temperature range of 200–800 K is reasonable for exploring the Haber process. No scientific inaccuracies were identified.

Evidence of quality for Criterion C: [ ] No [ ] Inadequate [x] Adequate [ ] Extensive

Suggestions for improvement of the task for Criterion C:

The task could include a glossary of key terms (equilibrium, exothermic, concentration, catalyst) for English learners. A sentence about the iron catalyst used industrially could be added to Part 4 to enrich the engineering context. A peer-discussion component would strengthen opportunities for collaborative sensemaking. The task could also offer an optional “challenge extension” where students calculate the equilibrium constant (K_eq) from simulation data for advanced students.

Criterion D. Tasks support their intended targets and purpose.

Before you begin:

  1. Describe what is being assessed. Include any targets provided, such as dimensions, elements, or PEs:

HS-PS1-6: “Refine the design of a chemical system by specifying a change in conditions that would produce increased amounts of products at equilibrium.” The task targets the integrated use of Constructing Explanations and Designing Solutions (SEP), PS1.B Chemical Reactions and ETS1.C Optimizing the Design Solution (DCIs), and Stability and Change (CCC).

  1. What is the purpose of the assessment? (check all that apply)
    • Formative (including peer and self-reflection)
    • Summative
    • Determining whether students learned what they just experienced
    • Determining whether students can apply what they have learned to a similar but new context
    • Determining whether students can generalize their learning to a different context
    • Other (please specify): Inquiry-based learning — the task is designed as an instructional activity that also produces observable evidence of three-dimensional learning.

i. The task assesses what it is intended to assess and supports the purpose for which it is intended.

Consider the following:

  1. Is the assessment target necessary to successfully complete the task?

Yes. To complete the engineering proposal (Part 4), students must specify a change in conditions that increases ammonia yield — this is the exact language of HS-PS1-6. The proposal requires them to refine the design of the chemical system by selecting a temperature range, pressure level, and concentration management strategy, and to justify these choices using evidence from their investigation.

  1. Are any ideas, practices, or experiences not targeted by the assessment necessary to respond to the task? Consider the impact this has on students’ ability to complete the task and interpretation of student responses.

The task requires some familiarity with using a computer simulation (clicking buttons, reading a graph, interpreting an indicator light). For students with limited prior experience with simulations, a brief tutorial or orientation to the simulation interface may be needed. The task does not require any mathematical calculation beyond qualitative observation of concentration changes (up/down). No stoichiometric calculations are required, so students who struggle with quantitative chemistry can still succeed.

  1. Do the student responses elicited support the purpose of the task (e.g., if a task is intended to help teachers determine if students understand the distinction between cause and correlation, does the task support this inference)?

Yes. The data table provides evidence of whether students can correctly observe and record equilibrium shifts. The Part 3 explanations reveal whether students understand why the shift occurs (causal mechanism), not just that it occurs. The engineering proposal in Part 4 reveals whether students can integrate their understanding across multiple variables and make trade-off decisions. A teacher can distinguish between a student who memorized “low temperature favors exothermic” and one who understands why and can apply it with appropriate caveats about reaction rate.

ii. The task elicits artifacts from students as direct, observable evidence of how well students can use the targeted dimensions together to make sense of phenomena and design solutions to problems.

Consider what student artifacts are produced and how these provide students the opportunity to make visible their 1) sense-making processes, 2) thinking across all three dimensions, and 3) ability to use multiple dimensions together [note: these artifacts should connect back to the evidence described for Criterion B].

Three key artifacts are produced: (1) Completed data table — Shows whether students can systematically collect data (SEP), and whether they correctly identify shift directions (DCI) and observe stability-and-change patterns (CCC). (2) Written explanations (Part 3) — Reveals causal reasoning about why shifts occur, integrating the DCI (equilibrium, exothermic, mole ratio) with the CCC (system stability perturbed by external change). (3) Engineering proposal (Part 4) — The most integrative artifact. Students must select conditions (applying DCI PS1.B), justify trade-offs (applying DCI ETS1.C), reference stability patterns observed in data (CCC), and construct a written evidence-based argument (SEP). This artifact provides the richest evidence of three-dimensional learning.

iii. Supporting materials include clear answer keys, rubrics, and/or scoring guidelines that are connected to the three-dimensional target. They provide the necessary and sufficient guidance for interpreting student responses relative to the purpose of the assessment, all targeted dimensions, and the three-dimensional target.

Consider how well the materials support teachers and students in making sense of student responses and planning for follow up (grading, instructional moves), consistent with the purpose of and targets for the assessment. Consider in what ways rubrics include:

  1. Guidance for interpreting student thinking using an integrated approach, considering all three dimensions together as well as calling out specific supports for individual dimensions, if appropriate:

The task itself does not include an embedded rubric, but the structure of the questions maps directly to the dimensions. The engineering proposal could be evaluated using a three-dimensional rubric where points are assigned for: (a) Correct application of equilibrium reasoning (DCI), (b) Use of simulation data as evidence (SEP), (c) Explanation of stability-and-change patterns (CCC), and (d) Quality of trade-off analysis (DCI ETS1.C + SEP). A model answer key should specify expected ranges: e.g., “optimal temperature around 400–500 K (high enough for reasonable rate, low enough for favorable equilibrium), high pressure (200+ atm), continuous reactant injection and product removal.”

  1. Support for interpreting a range of student responses, including those that might reflect partial scientific understanding or mask/misrepresent students’ actual science understanding (e.g., because of language barriers, lack of prompting or disconnect between the intent and student interpretation of the task, variety in communication approaches):

The data table provides a low-language-demand entry point — even students with limited English can demonstrate understanding by correctly recording shift directions and concentration changes. The written explanations in Part 3 provide more nuanced insight but could mask understanding for students with weaker writing skills. Teachers should be aware that a weak written explanation may reflect language barriers rather than conceptual gaps. The engineering proposal’s multi-paragraph format similarly advantages fluent writers.

  1. Ways to connect student responses to prior experiences and future planned instruction by teachers and participation by students:

Student responses on this task can inform instruction in several ways: (a) If students struggle with the mole-ratio reasoning for pressure effects, a review of gas stoichiometry is warranted. (b) If students correctly predict shifts but cannot explain why, additional instruction on the collision-model explanation of Le Chatelier’s Principle may be needed. (c) The engineering proposal can serve as a launching point for a broader unit on industrial chemistry, sustainability, or the role of fertilizers in global food systems.

iv. The task’s prompts and directions provide sufficient guidance for the teacher to administer it effectively and for the students to complete it successfully while maintaining high levels of students’ analytical thinking as appropriate.

Consider any confusing prompts or directions, and evidence for too much or too little scaffolding/supports for students (relative to the target of the assessment—e.g., a task is intended to elicit student understanding of a DCI, but their response is so heavily scripted that it prevents students from actually showing their ability to apply the DCI).

Directions are appropriately scaffolded. Part 2 provides clear step-by-step instructions with specific variables to test, preventing students from getting lost in the simulation. The data table is pre-formatted but requires students to fill in both observations and interpretations (shift direction), balancing structure with analytical thinking. Part 3 questions are open-ended enough to reveal genuine understanding without being so broad that students don’t know where to start. Part 4 gives explicit bullet-point requirements that guide students toward the key elements of a good engineering proposal (conditions, justification, trade-offs, evidence) without prescribing the answer. The balance between guidance and open-endedness is appropriate for high school students.

Evidence of quality for Criterion D: [ ] No [ ] Inadequate [x] Adequate [ ] Extensive

Suggestions for improvement of the task for Criterion D:

An explicit three-dimensional rubric should be developed and provided to teachers alongside the task. The rubric should include scoring descriptors for each dimension at three levels (emerging, developing, proficient). Additionally, a one-page teacher guide with suggested time allocations, common student misconceptions to watch for, and discussion prompts for debriefing the engineering proposals would strengthen the task’s usability.

Overall Summary

Consider the task purpose and the evidence you gathered for each criterion. Carefully consider the purpose and intended use of the task, your evidence, reasoning, and ratings to make a summary recommendation about using this task. While general guidance is provided below, it is important to remember that the intended use of the task plays a big role in determining whether the task is worth students’ and teachers’ time.

This task provides a well-structured, NGSS-aligned investigation of Le Chatelier’s Principle through the real-world context of the Haber process. It earned at least “Adequate” ratings across all four criteria. The anchoring phenomenon is compelling and relevant, the simulation allows direct manipulation of variables, and the 5E learning cycle guides students from curiosity through data collection to synthesis. The culminating engineering proposal effectively integrates all three dimensions. The task is accessible to a wide range of learners while providing sufficient challenge for advanced students. Minor improvements could include an explicit three-dimensional rubric, a glossary for English learners, and an annotated particle-diagram prompt, but the task is fully usable and instructionally sound in its current form.

Final recommendation (choose one):