Domain: Engineering — Food and Bioprocess Engineering
Target concept: Tea Polyphenol Determination (Folin–Ciocalteu Colorimetric Method)

Video generation prompt: Pipette 1 mL of green tea extract into a test tube, add 0.5 mL of Folin-phenol reagent, and thoroughly mix. Then add 1 mL of sodium carbonate solution and allow the mixture to stand at room temperature for 5 minutes.

Evaluation guide:
(i) Target concept: Colorimetric quantification of tea polyphenols via Folin–Ciocalteu reaction requires sequential reagent addition, mixing, and alkaline-induced chromogenic development.
Minimum mechanism: Reduction of phosphomolybdic/phosphotungstic acid by phenolic hydroxyl groups under alkaline conditions must produce a stable, homogeneous blue-green chromophore; this requires precise stoichiometric order (tea → Folin → mix → Na2CO3 → stand) and cannot occur without sodium carbonate-triggered pH shift.
(ii)Storyline: [Frame 0–2] Pipette approaches green tea extract vial → draws liquid → moves to test tube → dispenses 1 mL into tube. [Frame 3–4] Folin-phenol reagent bottle opens/pours → 0.5 mL added → immediate mixing shown (inversion/swirl). [Frame 5–6] Sodium carbonate bottle opens/pours → 1 mL added → no further mixing. [Frame 7–10] Tube held motionless on bench; liquid surface perfectly still; blue-green hue initiates at ~frame 8 and deepens uniformly through frame 10. All events occur in fixed frontal view, no cuts, no off-screen actions, no object substitution.

Manual:
Experimental Procedure
1. Pipette 1 mL green tea extract into a clean test tube.
2. Add 0.5 mL Folin-phenol reagent; mix thoroughly by inversion or vortex.
3. Add 1 mL sodium carbonate solution; allow mixture to stand motionless at room temperature.
Observation of Experimental Phenomena
A homogeneous blue-green color develops gradually and uniformly in the mixture only during the standing phase after sodium carbonate addition.
Summary of Experimental Principles
Polyphenols in green tea reduce the Folin-phenol reagent in alkaline medium (provided by sodium carbonate), forming a blue-green molybdenum/tungsten complex measurable at 765 nm.

Prompt Grounding rubric:
level_1: No green tea extract, no test tube, no Folin-Ciocalteu (Folin-phenol) reagent, and no sodium carbonate solution appear, and no pipetting, mixing, or standing action is shown; the scene bears no visible relation to a colorimetric tea-polyphenol assay.
level_2: Only some of the required items appear (for example a test tube or pipette, but the green tea extract, the Folin-phenol reagent, or the sodium carbonate solution is missing); some liquid-transfer action occurs, but it does not follow the pipette-into-tube, then-Folin-phenol, then-mix, then-sodium-carbonate, then-stand order, and the overall sequence is not recognizable as this assay.
level_3: The green tea extract (brownish-yellow liquid), test tube, Folin-phenol reagent (colorless-to-pale-yellow liquid), sodium carbonate solution (colorless liquid), and pipette are all present; roughly 1 mL of extract is pipetted into the tube and both reagents are subsequently added, but the mixing step is missing or unclear and there is no visible period of undisturbed standing afterward.
level_4: All five items are present and correctly identified by appearance; the green tea extract is pipetted into the test tube; the Folin-phenol reagent is added; thorough mixing is visibly demonstrated (vortexing or repeated inversion with clearly moving liquid); the sodium carbonate solution is then added; and afterward the tube is set down and left motionless, with no hand or tool contact, for a continuous period that satisfies the procedure's 'stand' step.
level_5: All five items (green tea extract, test tube, Folin-phenol reagent, sodium carbonate solution, and pipette) are present and visually distinct; the extract is pipetted into the tube, the Folin-phenol reagent is added, the mixture is visibly swirled or inverted at least twice, the sodium carbonate solution is then added, and afterward the tube remains completely still (undisturbed by any hand, tool, or camera movement) for a continuous, unbroken period that visibly satisfies the 'stand at room temperature for 5 minutes' instruction.

Scientific and Causal Correctness rubric:
level_1: No blue-green coloration ever appears; the mixture stays colorless or keeps the original brownish-yellow green-tea hue throughout, showing no sign that the Folin-Ciocalteu redox reaction with tea polyphenols has taken place.
level_2: A color change occurs but is chemically wrong for this reaction (the mixture turns red, orange, brown, or black rather than blue-green), or a blue-green tint appears before the sodium carbonate is added, with no timing relationship between the alkaline reagent and the color.
level_3: A blue-green color does develop, but it appears too early (before the sodium carbonate is added or while the reagents are still being mixed), or it fades after forming, or it forms unevenly as streaks or patches rather than a uniform hue, so the link between the sodium carbonate addition and the color is only loosely suggested.
level_4: The blue-green color appears only after the sodium carbonate is added and only while the tube stands undisturbed; it is uniform across the whole liquid with no premature tint, no fading, and no patchiness, and it darkens steadily during standing, but the final shade is pale or washed-out rather than the rich blue-green expected from a strong positive reaction.
level_5: The blue-green color appears exclusively after the sodium carbonate is added and exclusively during the standing period, forming uniformly across the entire liquid with no streaking; it deepens progressively while the tube stands and settles into a rich, saturated blue-green consistent with a well-developed Folin-Ciocalteu phosphomolybdic/phosphotungstic chromophore, with no color visible beforehand and no loss of intensity afterward.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal breaks are visible: the test tube's position jumps discontinuously between frames, liquid appears or vanishes with no visible pouring source, the pipette tip relocates instantly instead of moving continuously, the lighting strobes violently, the tube's shape warps or spins with no physical cause, or the bench background behind the tube changes color or texture mid-sequence with no visible cause.
level_2: Multiple moderate flaws occur: the pipette moves with no liquid visibly leaving it, a reagent bottle disappears and reappears between shots, the mixing motion cuts abruptly between static poses instead of flowing continuously, the standing phase shows a sudden lighting shift or an unexplained camera refocus, or the test tube tips or wobbles as if unsupported.
level_3: One minor flaw is present (for instance a brief blur during pipetting that obscures the exact volume delivered, slight camera shake while the tube stands, a small brightness flicker during mixing, or a momentary occlusion of the tube's mouth during inversion), but the tube, pipette, and bottles keep consistent relative positions and nothing breaks apart or relocates.
level_4: All motion is physically plausible: the pipette descends at a steady, controlled speed and the liquid flows into the tube without splashing over the rim; the mixing shows natural momentum and a coherent fluid swirl; during standing the tube shows no motion, the lighting stays even, the camera viewpoint is fixed, and nothing occludes the tube; the tube itself stays rigid and upright with no warping or rescaling.
level_5: The pipette's descent is smooth and gravity-aligned, the liquid enters the tube as a continuous stream forming a clean meniscus, and the mixing produces a coherent, symmetric swirl with no liquid breaking into droplets; once standing begins, the liquid surface shows no discernible motion or ripple to the eye, the camera does not drift, the shadow does not shift, and every object edge stays sharp and stable for the rest of the shot.