ACS Lesson 4.1 (Grade 2 Float and Sink) - a lean ACS lesson. Density formula explicitly deferred, zero molecular content. Excellent fair-test inquiry and a memorable three-layer liquid demo, zero map errors. But Foundation 0% (Not Recommended, floor) because there's no atomic anchoring anywhere. Most extreme Type 6 Clean-but-Empty case.
| Program | ACS Inquiry in Action |
| Lesson Title | Grade 2, Lesson 4.1: Float and Sink |
| Publisher | American Chemical Society |
| Author | ACS Education Division (2019) |
| Year | 2019 |
| Grade Band | Grade 2 (K-2 calibration applied) |
| NGSS Alignment | 2-PS1-1 |
ACS 4.1 scores Foundation 0% - the lowest and tied with the framework floor. Zero map errors across 21 student-facing passages. Zero confirmed FSEs after rigorous review. But adjusted gap is 100% - all 14 mechanism passages are UNSCAFFOLDED. The lesson contains no molecular, atomic, or even particulate content. The teacher's note on p. 1 explicitly states: "The quantitative concept of 'density' as D=mass/volume is not addressed directly." The atomic/molecular deferral that comes with it is implicit but total.
This is the third type of K-2 atom-deferred pattern observed, alongside other atom-deferred patterns at K-2. The verdict is Not Recommended because Foundation 0% is at the floor. This is a clean-but-empty lesson: excellent inquiry design, descriptively correct, zero errors - but zero atomic anchoring.
The lesson is approximately 5 pages following the 5-E structure. Engage: the teacher places a stick and a stone in water; students predict and observe, then generalize that "stone has the characteristic property of sinking" and "wood has the characteristic property of floating." Explore: students test 8 objects (pencil, popsicle stick, candle, crayon, penny, paper clip, eraser, rubber band) and identify patterns by material class. A surface-tension caveat handles initially-floating rubber band and crayon. Explain: an animation demonstrates that floating and sinking are size-independent - a bigger piece of wood than metal still floats; a smaller piece of eraser than candle still sinks. Extend: a teacher demonstration with three liquids (colored water, colored corn syrup, vegetable oil) produces a three-layer demonstration (oil top, water middle, syrup bottom).
"The quantitative concept of 'density' as D=mass/volume is not addressed directly. Instead, students explore sinking and floating and develop the understanding that things that sink are heavy for their size and things that float are light for their size." (Overview, p. 1)
The explicit scope-limiter. The curriculum designer's deliberate choice - defensible at Grade 2 (NGSS introduces D=m/V at 5-PS1) but sets the WWG ceiling at Not Recommended.
"Whether something floats or sinks in water has to do with how heavy it is compared to how big it is. Things that are heavy for their size tend to sink in water." (Key Concepts, p. 1)
The K-2 proxy for density. Right intuition pump, but doesn't connect downward to atoms.
Floating is presented as "a characteristic property of wood no matter how big it is" and sinking as a characteristic property of rubber "no matter how small it is." Size-independent properties. (Explain, p. 4)
Correct K-2 framing of intensive property without naming intensive properties.
"Even though a crayon is made mostly from wax, most crayons sink. This is because of the pigments and other substances added to the wax to give them color." (Explore, p. 3)
Genuine compositional explanation at substance scale - stops at "substances added" without naming molecules.
"The oil floats on the water. The corn syrup sinks through the oil and water and ends up on the bottom of the cup." (Extend, p. 5)
Three-layer demo - vegetable oil ~0.92 g/mL, water 1.00, corn syrup ~1.38. A perfect teaching moment for density-as-intensive-property that passes without molecular grounding.
Practices: 64.3% (amber tier - lowest). Three of seven NGSS practices are PRESENT, three are PARTIAL, one is ABSENT. A standout practice is planning investigations - predict-and-test with 8 objects plus the three-layer liquid demo. Asking questions is PRESENT with "What do these have in common?" pattern-recognition prompts. Constructing explanations is PRESENT - size-independence in the animation is a real attempt to make density-as-property accessible. Modeling is PARTIAL (no atomic/molecular models). Mathematics is ABSENT - explicit deferral of D=m/V removes the obvious quantitative hook.
The lesson is correctly designed against NGSS 2-PS1-1. Changing the verdict to Rewrite or Recommended would require adding atomic/molecular content the standard doesn't require.
Option A (lightest touch, would clear Not Recommended floor to Rewrite, ~30% Foundation): Add one teacher's note in the Extend section: "Note: liquids and solids float or sink because of how their molecules are packed. Heavy materials have molecules with more weight per space. Lighter materials have molecules with less weight per space." This single sentence scaffolds all mechanism passages.
Option B (moderate, ~60% Foundation): Add Option A plus name water as H₂O and add a molecular sentence about the layering: "Oil molecules don't mix with water molecules (oil is hydrophobic). Corn syrup molecules are sugar molecules - water is attracted to them, but the syrup is dense because there are many sugar molecules in a small space."
Option C (atoms-first restructure, ~80%+ Foundation): Restructure the EXPLAIN section around the molecular picture used in ACS 2.1 - atoms packed tightly vs loosely, molecule size, intermolecular interactions. Would bring 4.1 up to the standard set by 2.1 and 3.1.
| Total Passages Scored | 21 |
| Raw Gap Error | 100.0% (zero atomic content in lesson) FALSE = atoms/molecules not present before students are asked to explain. The student is navigating without a starting point. |
| Adjusted Gap Error | 100.0% (all 14 mechanism passages UNSCAFFOLDED) UNSCAFFOLDED = no atomic grounding at all. LESSON_ATOMS = atoms mentioned elsewhere in lesson but not connected to this concept. |
| Substance-Model Errors (REI) | 0 Curriculum treats a process or outcome as a substance - "heat flows," "energy is stored," "electricity flows like water." Student builds a substance ontology. |
| Label-as-Explanation (LAE) | 0 Curriculum provides a name and treats it as an explanation - "this happens because of gravity." Student believes knowing the name IS understanding the concept. |
| Vague-Entity Errors (AEC) | 0 Curriculum uses vague entities ("tiny particles," "building blocks") without specifying atoms or molecules. Student invents their own model with macroscopic properties. |
| Factual Science Errors (FSE) | 0 Statements that are scientifically incorrect - not imprecise framing, but wrong. Any confirmed FSE = Not Recommended. |
| Practices | 64.3% - Mid Seven practices scored PRESENT, PARTIAL, or ABSENT and averaged: asking questions, developing and using models, planning and carrying out investigations, analyzing and interpreting data, using mathematics, constructing explanations and designing solutions, and argument from evidence. Higher is better, the opposite direction from gap and map errors. Reported but not part of the Foundation Score or the verdict. |
ACS Lesson 4.1 is a lean ACS lesson. Foundation 0% with zero map errors and zero FSEs confirms that the WWG framework can identify lessons that are simultaneously descriptively excellent AND structurally empty.
Excellent fair-test methodology. Predict-and-test with 8 objects. Memorable three-layer liquid demo (oil/water/corn syrup). Surface tension caveat for rubber band/crayon. Size-independence explanation correctly captures intensive property. Zero map errors and zero FSEs after rigorous review.
shallow by default - Zero MISCONCEPTION_BY_DESIGN flags. All density-based predictions verified against published densities. The "heavy for size" framing is the right K-2 intuition pump. The size-independence explanation correctly captures density-as-intensive-property without naming density. Surface tension caveat is sophisticated K-2 science. Nothing is wrong here - there's just no atomic anchoring anywhere.
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Scores, verdict, and the full pattern count for this unit are above: adjusted gap, REI / LAE / AEC counts, FSE status, and the seven-practice score. The analysis quotes 5 passages verbatim from the curriculum.
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