Domain: Engineering — Food and Bioprocess Engineering
Target concept: Vitamin B5 Determination (Colorimetric Method)

Video generation prompt: Add 2 mL yeast extract solution to a test tube, then add 2 drops of acidic ferric chloride–hydroxylamine (hydroxamate) color reagent and mix thoroughly.

Evaluation guide:
(i) Target concept: Colorimetric detection of pantothenic acid (Vitamin B5) via the ferric hydroxamate reaction.
Minimum mechanism: Yeast extract must contain bioavailable pantothenic acid, whose internal amide bond reacts with hydroxylamine to form a hydroxamic acid derivative; under acidic conditions this hydroxamic acid complexes with Fe(III) ions to give a wine-red/purple ferric-hydroxamate complex; reaction requires direct mixing/agitation for the color to fully develop; the colored complex is water-soluble and visibly distinct from the pale starting solution.
(ii)Storyline: [0–2s] Static shot: labeled yeast extract vial and dropper bottle of ferric hydroxylamine reagent in frame; test tube empty and centered. [2–3s] Pipette enters frame, dispenses clear/yellowish liquid into tube (2 mL volume implied by meniscus level). [3–4s] Dropper tip positions over tube opening; first drop detaches and impacts surface. [4–5s] Second drop detaches and impacts surface. [5–10s] Hand grasps tube and performs smooth, continuous swirling motion: liquid rotates cohesively, a wine-red/purple hue emerges progressively during rotation and fills entire volume uniformly by final frame. All events occur from fixed frontal viewpoint; no cuts; lighting remains constant; background is uncluttered lab bench.

Manual:
Experimental Procedure
1. Place a clean test tube upright on bench.
2. Using a graduated pipette, add 2 mL yeast extract solution into the tube.
3. Using a dropper, add exactly 2 drops of acidic ferric chloride–hydroxylamine (hydroxamate) color reagent into the same tube.
4. Cap tube and swirl gently for 5 seconds until homogeneous.
Observation of Experimental Phenomena
After mixing, the solution develops a stable, uniform wine-red/purple color — no precipitate, no gas, no phase separation.
Summary of Experimental Principles
Pantothenic acid (Vitamin B5) in yeast extract contains an internal amide bond that reacts with hydroxylamine to form a hydroxamic acid derivative; under acidic conditions this complexes with ferric (Fe3+) ions to give a wine-red/purple ferric-hydroxamate complex, whose intensity correlates with pantothenic acid concentration (colorimetric quantification).

Prompt Grounding rubric:
level_1: No test tube appears; no yeast extract solution is visible; no ferric hydroxylamine (hydroxamate) reagent bottle or dropper is visible; and no liquid-transfer or mixing action of any kind is shown.
level_2: A test tube containing a clear liquid appears, but no yeast extract solution can be identified entering it (e.g., no labeled source vessel, or the wrong container is used); the ferric hydroxylamine reagent is never dispensed (no dropper, no visible drops); and no addition or mixing action takes place.
level_3: A test tube holding a clear liquid is shown; yeast extract solution is visibly added to it from a labeled or otherwise identifiable source; two distinct drops of reagent are seen entering the liquid; and a mixing action (swirling, inverting, or stirring) begins afterward.
level_4: Everything described in the 3-point level is true. In addition, the reagent is dispensed from a dropper bottle that looks and/or is labeled consistent with the ferric hydroxylamine (hydroxamate) reagent (e.g., an amber glass dropper bottle with a yellow-brown liquid); the yeast extract solution comes from a clearly labeled vial or pipette; the swirling/mixing motion is continuous and completes at least one full visible rotation with the liquid clearly in motion; and no unrelated objects or actions interrupt the sequence.
level_5: Everything described in the 4-point level is true. In addition, the yeast extract solution is added first, visibly entering the tube before any reagent drop appears; exactly two reagent drops follow it, landing one after another; the swirling motion begins immediately once the second drop lands and continues without pausing until the liquid looks evenly agitated; the camera viewpoint and all object positions stay fixed throughout with no jump cuts or teleporting objects; and every label and container is clearly legible and chemically appropriate for this reagent.

Scientific and Causal Correctness rubric:
level_1: No color change happens at all: the liquid stays clear/pale throughout; or the reagent and yeast extract are combined in the wrong order or never actually mixed; or the final liquid shows no visible reaction of any kind.
level_2: The liquid changes color, but to the wrong hue (e.g., blue, green, bright yellow, or orange) or turns cloudy/turbid instead of clear-colored; or the color appears before the reagent drops land, or during the yeast-extract addition alone, with no visible connection between the reagent drops and the color change.
level_3: The color change begins only after both reagent drops have landed and mixing has started; the final liquid shows a distinct wine-red to purple hue (not blue, not green, not bright yellow); the color builds up gradually while swirling and settles into its final shade by the end of the clip; no unrelated phenomena (bubbling, precipitate, layering) appear.
level_4: Everything described in the 3-point level is true. In addition, the first visible tint of color appears within roughly a second of the second drop landing, rather than developing well before or long after the drops are added; the wine-red/purple color is even throughout the liquid once mixed, with no streaks or unmixed pockets; and nothing unrelated to the reagent reaction (lighting glare, reflections, stains) mimics the color.
level_5: Everything described in the 4-point level is true. In addition, once developed the wine-red/purple color stays steady for the rest of the clip: it doesn't fade, shift toward another hue, or bleach out; the shade is consistent with a ferric-hydroxamate complex (a red-toned purple, not a cool blue-violet and not a plain brown); and the color change is clearly caused only by the reagent mixing with the yeast extract, with no added light filters, overlays, or post-processing color effects.

Spatiotemporal Consistency rubric:
level_1: The test tube vanishes and reappears at some point in the clip; the liquid seems to jump instantly between containers without ever visibly moving between them; the room's lighting suddenly switches (e.g., a bright scene cuts straight to a dim one within a single frame) with no visible cause; there's an abrupt camera cut or zoom in the middle of an action; or the swirling motion starts or stops with a visible jump-cut rather than flowing continuously.
level_2: The test tube stays on screen but its position jumps left or right between frames with no visible cause; the dropper appears to move with no hand or arm holding it; the swirling motion halts and restarts at inconsistent speeds; or the shadow the dropper casts suddenly swings to point a different way, as though the light in the room silently jumped.
level_3: The test tube, dropper, and the hand/arm holding them stay visible and spatially coherent throughout: nothing vanishes or reappears unexpectedly; the room's lighting direction and brightness stay the same from start to finish; every motion looks physically plausible (the hand holds the dropper, then either sets it down or moves it toward the tube; the tube tilts and swirls with natural momentum); and the tube or liquid never bends, warps, or distorts unnaturally.
level_4: Everything described in the 3-point level is true. In addition, the dropper tip stays aligned right above the tube's opening while dispensing; the tube itself doesn't slide or shift on the bench while liquid is added; the swirling motion clearly originates from the hand gripping the tube and follows a smooth rotating path without the tube slipping out of the hand or floating on its own; and shadows and highlights on the tube shift smoothly and match its motion at every point.
level_5: Everything described in the 4-point level is true. In addition, the whole sequence flows without any skipped frames or stutters: the yeast-extract addition, first drop, second drop, and swirling motion each flow into the next with no unnatural pause or jump; the liquid's surface and the tube's edges stay steady from frame to frame with no jittering or flickering; and the camera viewpoint stays completely still throughout, with no panning, tilting, zooming, or refocusing.