Domain: Healthcare — Nutrition and Food Hygiene
Target concept: Determination of Industrial Salt (Sodium Nitrite) Using the Griess Reagent Method

Video generation prompt: A 10 mL food extract containing nitrite was placed in a test tube, and the Griess reagent was added dropwise. The mixture was gently shaken and allowed to stand for a moment.

Evaluation guide:
(i) Target concept: Visual confirmation of nitrite presence via Griess reaction colorimetry.
Minimum mechanism: Acidic conditions must be pre-established in extract (implied); diazotization and coupling must occur sequentially in solution to yield magenta dye; color must emerge only after mixing and incubation, not instantaneously or pre-formed.
(ii)Storyline: [Frame 0–2] Static shot: labeled test tube containing pale liquid centered in frame. [Frame 3–4] Griess reagent dropper enters top of frame, aligned vertically over tube opening. [Frame 5] Single droplet detaches and falls toward liquid surface. [Frame 6–7] Droplet impacts, liquid surface ripples; hand shakes tube laterally; meniscus oscillates smoothly. [Frame 8–10] Tube returns upright; liquid surface becomes completely still; uniform pink/magenta color fills entire liquid column. All phases viewed from fixed frontal angle, full tube visible, no occlusion, consistent lighting.

Manual:
Experimental Procedure
1. Place 10 mL food extract into a clean test tube.
2. Add Griess reagent dropwise from a calibrated dropper held vertically above tube.
3. Gently shake tube side-to-side once.
4. Place tube upright and let stand undisturbed.
Observation of Experimental Phenomena
Food extract + Griess reagent yields uniform pink-to-magenta color development in liquid phase after standing.
Summary of Experimental Principles
Nitrite ions in acidic medium react with sulfanilamide to form diazonium salt, which couples with N-(1-naphthyl)ethylenediamine to form a stable magenta azo dye—quantifiable by absorbance at 540 nm.

Prompt Grounding rubric:
level_1: No test tube is shown, or no pale food-extract liquid is visible inside it, or no Griess reagent bottle or dropper appears, or the tube is never placed for viewing, or neither the shaking action nor the standing/settling phase is ever shown.
level_2: A test tube with liquid is visible and a Griess reagent bottle appears, but the dropper is never shown releasing a droplet toward the tube, and neither the shaking motion nor the standing phase is depicted; the liquid's identity as a food extract is not established (e.g., no visible label or context).
level_3: A single test tube holding a pale liquid is shown, with a labeled Griess reagent dropper positioned above the tube opening, and the tube visibly moves side to side at some point and later sits still, but the droplet leaving the dropper and entering the liquid is never actually shown on screen, only the before-and-after states.
level_4: The test tube with its pale liquid, the Griess reagent dropper, at least one visible droplet entering the tube, a shaking motion that visibly moves the liquid's surface, and a following still period are all shown in the correct order, but one setup detail is off, e.g., the tube tips at an angle inconsistent with the dropper's aim, or the shaking looks more like a full inversion than a gentle side-to-side motion.
level_5: All elements match the prompt in the correct order: the test tube holds a pale food-extract liquid; the Griess reagent dropper is held above the opening and releases exactly one droplet (no splashing, no multiple simultaneous droplets) that visibly enters the tube; the tube is then gently shaken side to side, visibly disturbing the liquid surface; the tube is set down and the liquid settles to complete stillness, with no lingering drift or vibration; with no extraneous objects, no missing step, and no camera cut interrupting the sequence.

Scientific and Causal Correctness rubric:
level_1: No color change occurs after the Griess reagent is added; the liquid stays pale/colorless throughout; or a color appears that has no connection to nitrite chemistry (e.g., the liquid turns green, black, or an instant deep purple the moment the droplet lands, with no pink stage at all).
level_2: A color change happens, but it's the wrong color for this reaction (e.g., blue or green rather than pink/magenta), or the color appears before the reagent droplet actually reaches the liquid, or the color shows up only as a streak or ring on the tube's inner wall rather than throughout the liquid itself.
level_3: After the droplet is added and the tube is shaken, the liquid turns pink-to-magenta and the color fills the bulk of the liquid rather than staying confined to the surface or the tube wall; no unrelated colors (orange, brown, violet) appear; the color is still present once the tube has settled.
level_4: The bulk pink-to-magenta color and lack of stray hues from level 3 hold, and in addition the color only becomes visible after the droplet has been added and the tube shaken (not while the droplet is still falling), the color visibly deepens from a lighter pink toward a richer magenta over the standing period, and the liquid does not turn cloudy, develop a precipitate, or fade back toward colorless while standing.
level_5: The deepening color and clear liquid from level 4 continue, and in addition the color visibly begins developing within the first part of the standing period and keeps deepening steadily over the time the tube is shown standing, reaching a stable, even magenta by the end of the clip rather than changing at an implausibly instantaneous speed; there is no reddening or blueing away from magenta; the color is uniform across the whole liquid column with no rings, streaks, or layering; no bubbles or particulate matter appear at any point.

Spatiotemporal Consistency rubric:
level_1: The test tube is visible, then missing from a frame, then back in the same spot with nothing (no cut, no motion) to explain the gap; the liquid's level changes instantly between frames with no pouring or shaking to account for it; the reagent dropper disappears the instant after releasing its droplet; the room brightens or darkens in a sudden flash unconnected to any action; the tube's glass visibly warps or twists.
level_2: The tube stays in place but shows a clear break in continuity, such as the liquid level shifting without any visible cause, the falling droplet vanishing partway down before reaching the liquid, the shaking motion starting or stopping with an unnatural jerk, or the shadow the tube casts swinging to a different side without any change in the light source.
level_3: The test tube, dropper, and liquid stay in the same relative arrangement throughout; the liquid surface moves smoothly while being shaken and settles gradually rather than snapping still; the droplet falls along a steady, unbroken path; the tube's shape stays constant with no warping; and there is no sudden jump in the picture's brightness between one moment and the next.
level_4: The steady arrangement and smooth liquid motion from level 3 hold, and in addition the droplet's fall from the dropper tip to the liquid surface is shown as one continuous path with no gap or skip; the liquid's oscillation after shaking dies down steadily rather than bouncing back up partway through; the tube and the background keep a fixed relationship with no sliding parallax; the shaking keeps a steady pace rather than speeding up or slowing down unnaturally between frames.
level_5: The steady motion from level 4 continues at a believable human hand-speed throughout, with no moments that look unnaturally slow or fast; the liquid's meniscus keeps a consistent curve: concave at rest, shifting smoothly as the tube moves during shaking; the tube's rim, the liquid's edge, and the dropper tip stay visibly aligned with each other from one frame to the next with no noticeable drift, wobble, or misregistration; and the light falling on the tube and dropper keeps the same apparent direction and brightness relative to those objects for the whole clip.