Domain: Healthcare — Pharmaceutical Chemistry
Target concept: Identification of Tetracycline Hydrochloride (Ferric Chloride Colorimetric Method)

Video generation prompt: Place a small amount of tetracycline hydrochloride powder into a test tube, add purified water to dissolve it, gently shake, and then slowly add ferric chloride solution while gently rotating. Demonstrate clean and transparent glassware, pipettes, test tubes, and the controlled sequential addition of reagents.

Evaluation guide:
(i) Target concept: Visual confirmation of tetracycline hydrochloride identity via Fe³⁺-mediated colorimetric complex formation.
Minimum mechanism: Aqueous tetracycline must be present in molecularly dispersed form prior to Fe³⁺ addition; Fe³⁺ must directly contact tetracycline to trigger instantaneous, irreversible coordination; complex must exhibit characteristic brownish-red chromophore with no competing side reactions (e.g., hydrolysis, oxidation).
(ii)Storyline: [Frame 1–2] Static shot: test tube with visible white powder. [Frame 3–4] Purified water added → powder dissolves → solution becomes optically clear. [Frame 5–6] Pipette enters frame, delivers ferric chloride solution dropwise near tube mouth. [Frame 7–8] Simultaneous gentle rotation begins as first drop contacts solution. [Frame 9–10] Brownish-red color develops uniformly within solution during rotation: no lag, fade, or heterogeneity. All events occur from fixed frontal viewpoint with full tube in frame; no occlusion; lighting enables unambiguous color and state discrimination.

Manual:
Experimental Procedure
1. Place small amount of white tetracycline hydrochloride powder into clean, transparent test tube.
2. Add purified water to dissolve powder; gently shake until solution is clear.
3. Using a pipette, slowly add ferric chloride solution while gently rotating test tube.
Observation of Experimental Phenomena
Brownish-red color or precipitate forms immediately upon ferric chloride addition and persists.
Summary of Experimental Principles
Tetracycline hydrochloride forms a stable brownish-red coordination complex with Fe³⁺ ions under neutral/aqueous conditions—basis of ferric chloride colorimetric identification.

Prompt Grounding rubric:
level_1: No test tube is visible; no white powder is shown; no water is added; no ferric chloride solution appears; no pipette or dropper introduces any liquid; none of the described actions occur at all.
level_2: At least one correct item appears (the tube, the powder, or the pipette), but the core sequence is missing: the powder is never shown dissolving, there is no clear order of adding water and then ferric chloride, and the tube is never rotated at any point.
level_3: A test tube holds visible white powder; water is added and the powder dissolves before anything else is added; a pipette or dropper then introduces ferric chloride solution into the tube; the order powder → water → ferric chloride is visually clear; the tube is gently rotated during or right after the ferric chloride is added.
level_4: Everything required at the 3-point level holds, and in addition the glassware stays clear enough throughout to see the liquid inside, with no fogging, residue, or scratches blocking the view; the ferric chloride is delivered by the pipette rather than poured straight from a bottle; the rotation keeps turning around the tube's own axis; nothing in the frame (hands, labels, clutter) blocks the tube, the pipette, or the liquid inside.
level_5: Everything required at the 4-point level holds, and in addition the test tube stays centered in the frame the whole time; the pipette tip is visible approaching and reaching the tube mouth without anything hiding it; the white powder, the clear water/solution, and the ferric chloride solution each look visually distinct from one another before they mix; the rotation continues unbroken with the tube fully in view, with no cut, zoom, or camera-angle change.

Scientific and Causal Correctness rubric:
level_1: No color change happens after the ferric chloride is added; the mixture stays colorless or only a faint pale yellow for the entire clip; the liquid never takes on any brownish-red tint, and no precipitate of that color ever forms.
level_2: A color change does happen, but it is the wrong color (blue, green, purple, or black instead of brownish-red), or a precipitate forms that is white or grey rather than brownish-red, or the coloring appears before the ferric chloride is added.
level_3: A brownish-red appearance (as a clear solution, as a precipitate, or both) shows up only once the ferric chloride touches the tetracycline solution; the color stays confined to the liquid inside the tube; once it appears, the brownish-red color does not fade or reverse before the clip ends; no unrelated effect such as bubbling, fizzing, or separate liquid layers accompanies the change.
level_4: Everything required at the 3-point level holds, and in addition the brownish-red color begins developing essentially as soon as the ferric chloride solution touches the tetracycline solution, without a long delay; if a precipitate forms, it appears only after mixing begins rather than being present beforehand; by the end of the clip the tube holds one consistent brownish-red appearance (whether a clear solution or an evenly distributed precipitate) rather than separated layers or floating clumps.
level_5: Everything required at the 4-point level holds, and in addition the color reads unambiguously as brownish-red, with no strong orange, yellow, or purple cast; if any solid forms, it is finely and evenly distributed rather than clumped in one spot; the final appearance (whether a clear brownish-red solution or a brownish-red precipitate suspension) holds steady for the remainder of the clip with no fading, bleaching, or shift to a different hue.

Spatiotemporal Consistency rubric:
level_1: The test tube jumps to a different position between frames; the room's brightness snaps from light to dark (or the reverse) with no lamp, switch, or shadow-casting object visible to explain it; the pipette appears or disappears mid-motion; the liquid level in the tube changes with nothing visibly poured in or out; or the tube's rotation suddenly reverses or jerks without a smooth transition.
level_2: One clear spatiotemporal flaw appears: the pipette tip is already inside the tube the moment it enters frame, with no visible approach; the tube starts rotating before the ferric chloride actually touches the liquid; the liquid level rises with no liquid visibly entering the tube; or the tube tilts more than about 30° off vertical and then snaps back upright.
level_3: The pipette's approach to the tube mouth, the liquid entering the tube, and the tube's rotation all look physically continuous and plausible; the liquid's surface behaves like an actual liquid meeting the tube wall rather than a flat, static shape; the tube rotates steadily about a vertical axis; nothing about the tube, the pipette, or the liquid warps or stretches unnaturally between frames.
level_4: Everything required at the 3-point level holds, and in addition the tube's glass wall and the liquid inside keep a steady level of glare and clarity as the color darkens, rather than suddenly flashing bright or turning opaque with no visible cause; the background behind the tube stays put; the tube's size and position in frame stay fixed with no unexplained zoom or pan; no part of the tube or liquid appears doubled or ghosted between frames.
level_5: Everything required at the 4-point level holds, and in addition the pipette's downward approach moves at a steady, hand-plausible speed; the tube's rotation keeps a constant turning speed rather than speeding up or slowing down abruptly; the ferric chloride enters the solution as a smooth stream or drop rather than splashing or spraying outside the tube; and no frames in the sequence appear skipped, frozen, or out of order.