Domain: Engineering — Food and Bioprocess Engineering
Target concept: Determination of Protein in Food (Biuret Method)

Video generation prompt: Take 2 mL of soymilk into a test tube, add 1 mL of reagent A of the biuret test, shake thoroughly to mix, then add 4 drops of reagent B, and shake again.

Evaluation guide:
(i) Target concept: Visual verification of biuret test execution and positive result for protein in soymilk.
Minimum mechanism: Soymilk must contain sufficient intact peptide bonds; reagent A must be strongly alkaline (e.g., NaOH/KOH); reagent B must contain CuSO₄; mixing must enable complex formation; violet-purple chromophore must be stable and visually resolvable under ambient lighting.
(ii)Storyline: [Frame 0–1] Static shot: empty test tube centered, soymilk container and two reagent bottles (A and B) adjacent in fixed positions. [Frame 2–3] Soymilk poured into tube: volume fills ~1/3, appearance light-beige and opaque. [Frame 4–5] Reagent A poured: clear stream, volume ~1 mL, followed immediately by vigorous swirling (meniscus distortion, liquid ascent/descent). [Frame 6–7] Four distinct blue drops descend into tube, spaced evenly, followed immediately by gentle flick-shake (small amplitude, rapid oscillation). [Frame 8–9] Violet-purple color emerges progressively from point of last drop impact, spreading uniformly to fill entire liquid column before video ends. All events occur from fixed frontal viewpoint; no camera movement; lighting constant; no occlusion of tube or reagent interfaces.

Manual:
Experimental Procedure
1. Place 2 mL soymilk (light-beige, opaque liquid) into a clear glass test tube.
2. Add 1 mL reagent A (colorless, clear liquid) using a calibrated dispenser; shake tube vigorously to mix.
3. Add 4 drops reagent B (blue solution) from a dropper; shake tube gently to disperse.
Observation of Experimental Phenomena
After step 3, the mixture develops a uniform violet-purple color throughout the liquid column.
Summary of Experimental Principles
The biuret reaction detects peptide bonds: Cu²⁺ (from reagent B) forms a violet-purple complex with peptide bonds in alkaline medium (provided by reagent A), confirming protein presence in soymilk.

Prompt Grounding rubric:
level_1: No test tube present; no soymilk visible; no reagent A or reagent B containers shown; no pipetting, dispensing, or shaking actions depicted; none of the three required steps (addition of 2 mL soymilk, addition of 1 mL reagent A, addition of 4 drops reagent B) occur in any form.
level_2: At least one container resembling a test tube is present, and at least one liquid is visible, but: either soymilk is absent or unidentifiable (e.g., wrong color/opacity), reagent A and reagent B are not distinguishable by container type, label, or volume cue, and fewer than two of the three required steps occur; e.g., only soymilk is poured, with no reagents added.
level_3: Test tube is present and contains a light-beige opaque liquid (soymilk); reagent A is delivered as a ~1 mL volume from a labeled or distinctly shaped container (e.g., dropper bottle or graduated cylinder) into the test tube; reagent B is delivered as discrete drops (≥3 visible drops) from a separate dropper; all three steps occur in correct order (soymilk → reagent A → reagent B), but shaking actions are missing or not visually confirmed (no motion blur, no swirling meniscus, no hand/tube movement).
level_4: All three steps occur in correct sequence with correct object types and quantities: (i) 2 mL soymilk (light-beige, opaque, filling ~1/3 of standard test tube) is placed in test tube; (ii) 1 mL reagent A (clear, colorless liquid) is added from a container with visible volume marking or calibrated delivery device; (iii) exactly 4 drops of reagent B (blue solution) are dispensed from a dropper with visible drop formation and separation; shaking after reagent A and after reagent B is clearly depicted (visible swirling motion of liquid, meniscus distortion, or tube rotation), but one of the two shakings lacks full continuity (e.g., brief cut, momentary stillness interrupting motion flow).
level_5: All elements from score 4 are present AND both shaking actions are fully continuous, uncut motions: (i) immediate vigorous swirling after reagent A addition results in homogeneous mixing (no stratification, no visible unmixed streaks); (ii) immediate gentle inversion or flick-shaking after reagent B addition produces uniform dispersion (no pooling, no isolated blue droplets remaining on wall); all objects retain consistent identity, labeling (if shown), and spatial relationship throughout; no camera jump, zoom, or occlusion during any step.

Scientific and Causal Correctness rubric:
level_1: No color change occurs; final mixture remains light-beige or turns brown/black/green/yellow; no purple/violet hue appears at any time; liquid remains transparent or becomes turbid without purple tint; reagent B is absent or added before reagent A; soymilk is replaced with water/milk/other non-protein liquid.
level_2: A color shift occurs but is scientifically invalid: e.g., purple appears without reagent B addition; purple appears before reagent A; purple appears instantly upon soymilk alone; final color is pink, magenta, or lavender (not violet-purple); or purple appears only transiently then fades to gray/brown within the video.
level_3: Purple/violet color develops only after reagent B addition and only when both reagent A and soymilk are present; the color is localized (e.g., appears first at drop impact site) or patchy (non-uniform distribution), but is objectively violet-purple (not blue, not red, not grayish); no false positives (e.g., purple without protein source) or false negatives (e.g., no purple despite correct reagents and soymilk).
level_4: Violet-purple color appears uniformly across the entire liquid column within 2 seconds after completion of second shake; color is stable (no fading, darkening, or phase separation during remainder of video); no incorrect intermediate states (e.g., blue-only before purple, or greenish tinge); all causal dependencies hold: no purple without prior reagent A addition, no purple without soymilk, no purple without shaking after reagent B.
level_5: Violet-purple color emerges precisely as a direct visual consequence of the second shake: onset begins at meniscus or drop-impact zone immediately during shake motion, spreads radially and continuously through the liquid column without interruption, and achieves full uniform saturation by the end of the shake; color matches authentic biuret-positive response (distinct from copper sulfate blue or hemoglobin red); no competing artifacts (e.g., reflection glare mimicking purple, shadow-induced hue shift, or chromatic aberration).

Spatiotemporal Consistency rubric:
level_1: Test tube teleports between frames; liquid volume changes discontinuously (e.g., jumps from half-full to full without pouring motion); reagent containers vanish/reappear; shaking motion shows impossible acceleration/deceleration (e.g., instant stop from high speed); lighting shifts abruptly (e.g., bright → dark between consecutive frames); tube deforms or fractures mid-sequence.
level_2: Major spatiotemporal breaks: ≥2 frame cuts during a single action (e.g., 3 cuts during reagent A addition); test tube rotates >90° without visible hand contact; liquid surface remains perfectly flat during vigorous shaking; reagent B drops appear fully formed mid-air with no descent trajectory; background shifts perspective (e.g., side view → top-down) without justification.
level_3: All objects maintain fixed relative positions: test tube stays centered in frame; reagent containers remain in same spatial relation (e.g., left/right of tube); liquid meniscus moves plausibly during pouring and shaking; no object clipping or occlusion that contradicts 3D layout (e.g., dropper appearing behind tube wall); lighting and shadow remain consistent in direction and intensity across all actions.
level_4: All conditions from score 3 satisfied AND motion is physically coherent: pouring shows laminar liquid stream (no splatter before contact); drops fall vertically with consistent spacing and size; shaking shows natural inertia (liquid lags slightly behind tube motion, then catches up); no interpenetration (e.g., dropper tip never passes through tube opening without entering); no temporal reversal or stutter (e.g., drop rising, liquid recoiling unnaturally).
level_5: All conditions from score 4 satisfied AND every motion adheres to macroscopic fluid dynamics: (i) reagent A pours as a continuous, unbroken stream ending in a clean break; (ii) each reagent B drop detaches fully before next forms (no dripping chain); (iii) during shaking, liquid exhibits realistic sloshing frequency and damping (no oscillation beyond 2–3 cycles, no sustained resonance); (iv) no frame-level artifacts (e.g., motion blur inconsistent with speed, ghosting, or temporal aliasing).