Domain: Healthcare — Nutrition and Food Hygiene
Target concept: Detection of Sorbic Acid

Video generation prompt: A 8 mL jam sample containing sorbic acid was placed in a test tube. An appropriate amount of potassium permanganate solution was added, the mixture was well shaken, and then heated in a 30°C water bath for 5 minutes.

Evaluation guide:
(i) Target concept: Visual demonstration of sorbic acid's redox reactivity via decolorization of KMnO4 (a simplified qualitative illustration inspired by sorbic acid detection, not a matrix-specific confirmatory assay; jam's naturally occurring reducing sugars can drive the same decolorization).
Minimum mechanism: Sorbic acid, together with reducing sugars naturally present in jam, supplies the reducing agent; KMnO4 must be aqueous and purple pre-reaction; heating at ~30°C must be applied to accelerate kinetics; reduction must yield soluble Mn²⁺ (colorless) without side products (e.g., MnO2 precipitate).
(ii)Storyline: [Frame 0–2] Jam poured into test tube, filling it to a level consistent with about 8 mL → [Frame 3–4] Dropper delivers purple KMnO4 solution into tube → [Frame 5–6] Tube shaken: contents visibly swirl and mix, color homogenizes → [Frame 7–8] Tube placed into water bath with visible 30°C label → [Frame 9–10] Solution transitions uniformly from purple to colorless/pale yellow; no residual color, no turbidity, no gas bubbles; all events occur from fixed frontal viewpoint with consistent lighting and scale.

Manual:
Experimental Procedure
1. Place 8 mL jam sample into a clear test tube.
2. Add potassium permanganate solution until purple color appears.
3. Shake tube vigorously to mix.
4. Immerse tube in 30°C water bath for 5 minutes.
Observation of Experimental Phenomena
Purple color of potassium permanganate solution completely disappears, yielding a colorless or pale yellow solution.
Summary of Experimental Principles
Sorbic acid, along with the reducing sugars naturally abundant in jam (e.g., glucose and fructose), can reduce purple MnO₄⁻ to colorless Mn²⁺ under mild heating. This is a simplified qualitative demonstration of sorbic acid's redox reactivity, not a specific confirmatory test: because jam's native sugars undergo the same reaction, decolorization of whole jam alone does not by itself prove sorbic acid is present.

Prompt Grounding rubric:
level_1: None of the four key items (jam, test tube, potassium permanganate solution, water bath) appear on screen; there is no test tube visible at all, no purple KMnO4 solution being added, and no water bath shown anywhere in the clip.
level_2: Only some of the four items appear: for instance a test tube or a water bath is visible, but the jam itself is missing, or the purple KMnO4 solution is never shown being added to the tube; the heating step is missing entirely or shown happening in the wrong container; the overall step order (jam in tube, add KMnO4, heat) is not recognizable.
level_3: All four items are present: a jam sample filling roughly 8 mL of a test tube, purple potassium permanganate solution visibly added into that same tube, the tube placed in a water bath that is labeled or otherwise clearly set at about 30°C, and some sign of heating (e.g., steam or a stable immersion); but at least one item is the wrong kind or amount (e.g., a beaker used instead of a test tube, more than one tube shown, or the jam fill level clearly too high or too low for roughly 8 mL).
level_4: Everything in score 3 is correct in kind: one clear cylindrical test tube; jam filling a plausible fraction of the tube consistent with about 8 mL, judged by fill height relative to the tube's total length or its printed graduation marks rather than a precise liquid meniscus (since jam is a thick, non-liquid sample); a dropper or pipette adding purple KMnO4 solution into the tube; and a water bath showing a 30°C temperature display or label with the tube fully submerged, all in one frame with no extra unrelated props; only the shaking step or the heating duration is left unclear or shown incorrectly (e.g., a time-lapse clock standing in for the 5-minute wait).
level_5: Everything in score 4 is shown correctly and at a believable scale: the single test tube holds jam at a fill level clearly consistent with about 8 mL of a thick semi-solid, judged via graduation marks or fill proportion rather than a sharp liquid meniscus; purple KMnO4 solution is added via a calibrated dropper; the tube is then visibly and vigorously shaken with contents visibly moving and mixing; and it is placed into a clearly labeled 30°C water bath; all of this happens in one continuous shot from a fixed front-facing view, with no cuts, no duplicated objects, and no substituted equipment.

Scientific and Causal Correctness rubric:
level_1: The KMnO4 solution stays a deep, uniform purple for the entire clip; contact with the jam produces no fading or color shift, and heating produces no visible effect on the solution's color at all.
level_2: The purple KMnO4 solution is shown, but it stays evenly purple throughout; the jam sits inertly without any visible mixing interface or reaction cue (no fading, no cloudiness, no precipitate), and the water bath produces no visible thermal cue (no shift in the jam/liquid level, no rising vapor).
level_3: The purple solution visibly contacts the jam; after shaking and heating, the color only partly fades (for example a lighter band forms near the top while the rest stays purple, or the fading is patchy), so it never reaches a fully colorless or pale-yellow end state, and it isn't visually clear that the heating step is what's driving the fading.
level_4: The solution is a uniform deep purple before contact, becomes a single evenly mixed purple mixture once the jam and KMnO4 combine and are shaken, and after time in the 30°C bath turns completely and uniformly colorless or pale yellow with no purple patches left, but the clip shows no accompanying cues (no bubbles, no precipitate, no visible level change) tying the color loss specifically to the heating step.
level_5: The solution starts deep purple, becomes one uniform purple mixture after the jam is added and shaken in, and then (only once the tube is in the 30°C bath) fades completely, evenly, and permanently to colorless or pale yellow, with no leftover purple streaks, no layering, and no color returning afterward; the fading visibly begins after heating starts (not before), proceeds without stalling, and produces no odd side-tint such as a brown cast or cloudy haze.

Spatiotemporal Consistency rubric:
level_1: The test tube vanishes from one moment and reappears somewhere else without any travel in between; the liquid level jumps without a pouring or mixing motion; the water bath flickers, or suddenly changes size or position; the overall lighting swings wildly between moments; the jam/liquid boundary resets to a different level with no visible cause.
level_2: The tube's angle or position changes with no hand or holder visible moving it; the KMnO4 solution shows up already fully mixed in during a single moment with no pouring motion beforehand; the jam's fill level changes in a jump rather than gradually; the water bath is only seen in the last moment of the clip with no earlier placement shown; the shaking looks jerky, skipping or freezing for more than a moment.
level_3: The test tube, jam, and water bath keep sensible positions relative to each other throughout; the tube stays upright and still while it's in the bath; the shaking shows continuous back-and-forth motion of the liquid without stutter or reversal; the jam/liquid surface moves smoothly during shaking and settles gradually afterward; the water bath's lighting and sense of depth stay consistent, though one small inconsistency is allowed, such as the dropper entering the frame from off-screen without a clear starting point, or steam appearing without a visible heat source nearby.
level_4: There is no vanishing or reappearing of the tube, no sudden lighting or shadow jump, and no visible warping of the tube or unnatural shearing of the jam/liquid surface; the shaking motion is smooth and moves back and forth along the tube's own axis; once in the bath, the tube sits at a steady depth with no sudden shift in view; but one small timing flaw is allowed, such as a brief freeze right as the tube moves into the bath, or the shaking stopping slightly before or after the tube is actually immersed.
level_5: There are no spatial or timing errors at all: the tube travels only through continuous, visible hand motion from the shaking step into the water bath; the jam/liquid surface deforms and settles the way a real viscous fluid would under shaking, with a believable slight rise as it warms in the bath; the lighting, shadows, and reflections look the same across every moment shown; there is no dropped moment, no visible glitching, and no shift in perspective: the whole sequence plays out in a single unbroken shot with a fixed camera position and zoom level.