Domain: Engineering — Food and Bioprocess Engineering
Target concept: Vitamin B6 Determination (Ninhydrin Colorimetric Method)

Video generation prompt: Take 2 mL of chicken extract into a test tube, add 2 drops of ninhydrin reagent, and heat in a 50 °C water bath.

Evaluation guide:
(i) Target concept: Enzyme-independent chemical colorimetric detection of an amine-bearing vitamin B6 vitamer (pyridoxamine) via ninhydrin condensation.
Minimum mechanism: Presence of pyridoxamine (the B6 vitamer that carries a free primary amine, -CH2NH2) + ninhydrin + aqueous medium + controlled thermal activation → ninhydrin-amine condensation → conjugated chromophore (a Ruhemann's-purple-type product) → violet color. Because ninhydrin reacts with any free primary amine, the free amino acids naturally abundant in chicken extract will generate the same violet reaction, so the color change reflects general ninhydrin-amine chemistry occurring in a B6-containing biological matrix rather than a signal exclusive to B6.
(ii)Storyline: [Phase 1: Setup] Chicken extract (pale yellow, translucent) fills ~1/3 of vertical test tube. [Phase 2: Reagent Addition] Dropper descends vertically, releases two discrete droplets that strike liquid surface and merge with visible meniscus depression. [Phase 3: Thermal Activation] Tube is lowered steadily into water bath; water level rises to cover lower half; no splashing. [Phase 4: Chromogenic Response] Violet hue emerges first at liquid-air interface, then uniformly intensifies through entire column, strictly confined to liquid phase, with no wall staining or gas-phase color. Perspective: Fixed frontal view, shallow depth of field, focus on tube center; all events occur within single continuous shot; no cutaways or inserts.

Manual:
Experimental Procedure
1. Pipette 2 mL chicken extract into a clean test tube.
2. Add exactly 2 drops of ninhydrin reagent using a calibrated dropper.
3. Place tube upright in a 50 °C water bath for color development.
Observation of Experimental Phenomena
A distinct violet color develops progressively in the liquid phase after heating begins; no color forms before heating or outside the liquid volume.
Summary of Experimental Principles
Pyridoxamine, the vitamin B6 vitamer that carries a free primary amine (-CH2NH2), reacts with ninhydrin under mild heat through the classic ninhydrin-amine condensation, forming a violet chromophore (a Ruhemann's-purple-type reaction). Because ninhydrin reacts with any free primary amine, this color change is not unique to vitamin B6: free amino acids that are naturally abundant in chicken extract will also give a strong violet ninhydrin reaction, so a positive result here demonstrates the general ninhydrin chromogenic reaction occurring in a B6-containing sample rather than serving as a B6-specific confirmatory test.

Prompt Grounding rubric:
level_1: No test tube is shown; no chicken extract liquid appears; no ninhydrin dropper or droplet is visible; no water bath container appears; none of the three required actions (loading the extract, adding the ninhydrin, and immersing the tube in warm water) takes place.
level_2: A single prop from the scene appears, such as only the test tube, only the dropper, or only the water-bath container, but no correct action follows: the chicken extract is missing or not recognizable as a liquid inside the tube, no ninhydrin droplets are added, and the tube is never lowered into the water bath.
level_3: Pale-yellow chicken extract fills roughly the lower third of an upright test tube; two separate ninhydrin droplets fall from a dropper and visibly disturb the liquid surface where they land; the test tube is then placed upright inside a water-bath container with warm water visible around its lower half.
level_4: Everything described in the 3-point level is present, and in addition the test tube stays upright and stationary inside the bath for the rest of the clip; the dropper tip stays above the liquid, descending and retracting without touching the tube's inner wall; the water bath's surface stays level, with no splashing, overflow, or a visibly dry heating surface.
level_5: Everything described in the 4-point level is present, and in addition the tube is lowered into the water bath right after the second droplet is added, with no unrelated pause or action in between; the two ninhydrin droplets land one after another rather than together, each leaving its own visible ripple on the liquid surface; the bath water looks like a warm liquid consistent with a mild simmer at most, never a rolling, vigorously bubbling boil.

Scientific and Causal Correctness rubric:
level_1: The liquid never develops any new color at any point in the clip; it stays colorless or pale yellow throughout; the water bath produces no visible heating effect; there is no visible link between adding the ninhydrin droplets and any color appearing.
level_2: A color does appear, but it is the wrong hue: for example blue, green, brown, or black instead of pink/violet; or the color shows up before the ninhydrin droplets are added or before the tube enters the water bath; or the color appears instantly with no heating time elapsing; or the color spreads unnaturally to coat the outside of the tube rather than staying within the liquid.
level_3: A pink-to-violet color develops gradually within the liquid itself, not smeared on the tube wall or floating above the surface; the color only begins appearing once the tube is inside the warm water bath; the color stays confined to the liquid volume and visibly deepens as the clip progresses.
level_4: Everything described in the 3-point level is present, and in addition the color first appears at the liquid's surface or at the bottom of the column and then spreads through the rest of the liquid; the tube itself and any reagent residue outside the liquid show no discoloration; the liquid stays free of cloudiness, precipitate, or separated layers as the color develops.
level_5: Everything described in the 4-point level is present, and in addition the final color is a true violet/purple rather than pink, magenta, or pale lavender; the color only appears in the heated sample, with no tint or glow that looks like a lighting reflection instead of a real color change; the color spreads across the whole liquid column in a broadly even way rather than staying confined to one isolated patch or streak; once formed, the color does not fade or shift to a different hue for the rest of the clip.

Spatiotemporal Consistency rubric:
level_1: Severe continuity break: the test tube appears already fully submerged in the water bath with no visible lowering motion, as if it jumped straight there; the chicken extract or the tube itself is momentarily absent from the shot and then present again with no camera motion to explain the gap; the scene's overall brightness or color cast jumps to a noticeably different look partway through the clip with no clear cause; the tube spins more than a quarter turn with no continuous motion showing how it got there; the liquid's height or shape jumps to a different level with no visible cause.
level_2: Noticeable continuity problems: the tube reaches the bath by sliding in sideways through the water rather than lowering in vertically from above; droplets appear on the liquid surface with no dropper visible above the tube; the water level in the bath rises or falls with no clear reason tied to the tube's motion; the tube blinks in and out of the frame; the liquid meniscus jumps to a new position with no motion leading up to it.
level_3: The test tube stays upright and centered inside the water bath throughout; the dropper approaches the tube from above and withdraws along the same path; the bath's water surface stays level and calm apart from droplet impacts; neither the tube, dropper, nor liquid appears to stretch, bend, or warp; every movement (lowering the tube, releasing the droplets) follows a smooth, physically sensible path.
level_4: Everything described in the 3-point level is present, and in addition the camera framing does not pan, tilt, or zoom during the clip; the overall lighting stays even across the scene with no sudden flashes or newly-shifting shadows; the depth to which the tube sits in the bath stays constant once it is placed; each droplet's impact briefly dents the liquid surface and the dent smooths back out naturally afterward.
level_5: Everything described in the 4-point level is present, and in addition the motion throughout is one continuous flow with no jump cuts, repeated frames, or freezing; the bath water shows only the gentle movement expected of standing warm water, without erratic sloshing; the tube, dropper, and bath rim keep sensible relative depth and overlap with one another as the camera view is held steady, with no object appearing to jump in front of or behind another inconsistently.