Domain: Healthcare — Nutrition and Food Hygiene
Target concept: Safrole Detection

Video generation prompt: Ten milliliters of a spice extract containing safrole were placed in a test tube, followed by the addition of formalin-sulfuric acid solution. The mixture was thoroughly shaken and allowed to stand.

Evaluation guide:
(i) Target concept: Marquis-type colorimetric detection of safrole via electrophilic aromatic substitution and condensation under strong acid conditions.
Minimum mechanism: Safrole must be present in extract; formalin (HCHO) and concentrated H2SO4 must coexist to generate electrophilic iminium/carbocation species; biphasic system must form (aqueous acid + organic extract) to localize reaction at interface; protonation and cyclization yield conjugated chromophore absorbing at ~550 nm (violet-purple).
(ii)Storyline: [Phase 1: Setup] Static shot: vertical test tube centered, containing pale yellow spice extract (organic layer). [Phase 2: Addition] Formalin-sulfuric acid (colorless/clear) flows visibly down tube wall into extract, forming lower aqueous layer; no immediate color change. [Phase 3: Mixing] Tube shaken: layers temporarily emulsify, then begin separating. [Phase 4: Standing] Tube held motionless: biphasic separation completes, violet-purple ring emerges *only* at interface and intensifies over ~1–2 s. [Perspective constraint] Fixed frontal close-up (tube occupies >60% height), no occlusion, full tube visible including meniscus and interface region. [Visibility constraint] Lighting ensures interface region is glare-free and high-contrast; no reflections mask violet-purple development.

Manual:
Experimental Procedure
1. Place 10 mL spice extract into a clean vertical test tube.
2. Add formalin-sulfuric acid solution carefully down the inner wall.
3. Cap and shake vigorously for ~2 seconds.
4. Stand upright undisturbed for ≥3 seconds.
Observation of Experimental Phenomena
A distinct violet-purple ring forms at the interface between the two immiscible layers, or a violet-purple band appears selectively in the upper organic layer.
Summary of Experimental Principles
Safrole reacts with formalin-sulfuric acid (Marquis reagent) to yield a characteristic violet-purple condensation product; the reaction requires acid catalysis, aldehyde condensation, and is specific to allylbenzenes with methylenedioxy groups.

Prompt Grounding rubric:
level_1: No test tube is shown, no spice extract liquid appears, no formalin-sulfuric acid solution is visible, no shaking action occurs, and no standing/settling period is shown.
level_2: The test tube holds a clear or pale-yellow liquid, but the formalin-sulfuric acid solution is never added, no shaking occurs, and no standing period follows.
level_3: The test tube contains liquid, the formalin-sulfuric acid solution is visibly poured or added into it, the tube is then shaken with visible rhythmic motion, and afterward the tube sits motionless for a stretch of the clip.
level_4: Everything in the 3-point level holds, and in addition the addition happens before the shaking, and the shaking happens before the standing period, in that order; the same tube is used throughout with no swap, and the liquid volume looks consistent before and after the reagent is added, with nothing appearing or vanishing unexplained.
level_5: Everything in the 4-point level holds, and in addition the tube is held upright during both the addition and the shaking with no tipped or inverted pouring, the standing period shows the same tube in the same position and orientation with no cut or replacement, and nothing extraneous (gloves, labels, other reagents) intrudes on the main action.

Scientific and Causal Correctness rubric:
level_1: No color change ever appears; the liquid stays colorless or pale yellow the whole time; no layered or ring-like feature ever forms; no cloudiness or precipitate appears either.
level_2: A uniform color change happens, but instantly upon addition before any shaking, or it happens and then fades away again during standing, contradicting the expected reaction timing.
level_3: A violet or deep-purple color appears only after the tube has been shaken and has stood for a while, either as a ring at the boundary between the two liquid layers or as a band within the upper layer; it looks clearly different from the original pale-yellow liquid.
level_4: Everything in the 3-point level holds, and in addition the violet-purple appearance stays localized to the interface or upper layer rather than spreading evenly through the whole tube, no other color such as red, blue, green, or orange shows up instead, and the color doesn't fade or disperse for the remainder of the clip.
level_5: Everything in the 4-point level holds, and in addition the violet-purple ring or band has a crisp, well-defined edge rather than blending gradually into the surrounding liquid, the lower layer stays colorless or pale yellow, and there is no bubbling, fizzing, or visible fuming that would suggest a different reaction is happening.

Spatiotemporal Consistency rubric:
level_1: The test tube vanishes partway through and comes back, the liquid level jumps to a different height with no visible cause, the shaking motion cuts out or skips moments, the camera angle changes abruptly mid-clip, or the standing phase suddenly shows the tube under starkly different lighting or shadow than the addition and shaking phases had, with no lamp change or cut to explain it.
level_2: The tube stays visible but its apparent size or framing jumps suddenly as if from an unintended zoom cut, the liquid surface flickers or briefly disappears, a hand appears only during the shaking step and is absent before or after, or the standing phase starts under noticeably different lighting than the earlier phases.
level_3: The tube stays in view in a consistent position and orientation, the liquid surface is steady and visible throughout the standing period, the shaking looks like a smooth, physically plausible back-and-forth motion, and the shadow the tube casts doesn't swing to a new angle between the addition, shaking, and standing phases.
level_4: Everything in the 3-point level holds, and in addition the poured stream connects visibly and continuously from the source vessel to the liquid surface with no jump, the shaking begins and ends with the tube in the same grip and posture, and the standing period shows the tube fully at rest with no lingering wobble or vibration.
level_5: Everything in the 4-point level holds, and in addition the tube stays visually stationary in the frame with no discernible pan or drift, the shadow it casts stays consistent with a single fixed light source, the curve of the liquid surface against the glass looks physically plausible throughout, and there is no apparent shift in perspective between the tube, any hand present, and the background during any step.