Domain: Healthcare — Medicine
Target concept: Identification Test of the Drug (Ferric Chloride Reaction)

Video generation prompt: A transparent test tube containing a small amount of salicylic acid powder was placed on the table. One milliliter of distilled water was added to dissolve the powder, followed by the addition of two drops of ferric chloride reagent. The color change of the solution was observed.

Evaluation guide:
(i) Target concept: Ferric chloride test for phenolic functional group in salicylic acid.
Minimum mechanism: Salicylic acid must be molecularly dissolved in aqueous medium to expose phenolate oxygen for chelation with Fe³⁺; complex formation requires stoichiometric Fe³⁺ and neutral-to-weakly-acidic pH; the violet/purple color arises from ligand-to-metal charge-transfer (LMCT) transitions in the resulting octahedral [Fe(salicylate)₃] complex, not from d-d transitions (which are Laporte- and spin-forbidden for high-spin Fe³⁺ and far too weak to account for the intense color observed), and not from oxidation or hydrolysis.
(ii)Storyline: Frame 1: Static wide shot: transparent test tube centered on table, dry salicylic acid powder visible as fine white crystalline deposit at bottom. Frame 2: Hand enters, adds clear liquid (water); powder visibly disperses and fully disappears into clear solution. Frame 3: Hand re-enters with dropper, releases two separate droplets into solution; no splashing or surface rupture. Frame 4: Solution remains still for ≥0.5s post-addition (no agitation). Frame 5: Uniform violet or purple hue emerges across entire solution volume and persists; no fading, no stratification, no residue. Perspective: Fixed frontal view, eye-level, full tube in frame, no obstructions, consistent lighting.

Manual:
Experimental Procedure
1. Place transparent test tube containing salicylic acid powder on table.
2. Add 1 mL distilled water to dissolve powder completely.
3. Add two drops of ferric chloride reagent.
Observation of Experimental Phenomena
Solution changes from colorless to uniform violet or purple after reagent addition.
Summary of Experimental Principles
Salicylic acid contains phenolic –OH group; reacts with Fe³⁺ to form violet/purple coordination complex — diagnostic for phenols.

Prompt Grounding rubric:
level_1: No transparent test tube is shown; or no white salicylic acid powder is visible inside it; or no water is added to the tube; or no ferric chloride reagent is applied via dropper; or the tube never contains any visible liquid; the core setup from the prompt (tube, powder, water, reagent) is essentially absent.
level_2: Only one or two of the five setup elements appear (for example the test tube and powder are shown but no water or dropper ever enters the frame, or a dropper adds liquid to an empty tabletop with no tube in view), and/or the order is scrambled (e.g., reagent appears to enter before any water is present).
level_3: All five setup elements appear in the prompt's order: transparent test tube on the table, white powder resting in it, water poured in and visibly dissolving the powder, then two drops of ferric chloride reagent added from a dropper, with the resulting solution remaining in the same single tube, regardless of whether any color change occurs or what hue results.
level_4: Everything required for score 3 holds, and in addition the setup mechanics are precise: the powder is fully dissolved before the dropper enters, exactly two separate drops (not a stream or a single blob) fall from the dropper, no extra powder, liquid, or third reagent is introduced, and the same tube (never swapped for another) holds the growing solution throughout; whether a color change appears, and what hue it is, is not evaluated here.
level_5: Everything required for score 4 holds, and in addition there is no staging error of any kind: the dropper never touches the tube or liquid before releasing its two drops, the water volume and tube position stay constant from the moment of pouring to the end of the clip, and the video closes on the same single test tube in the same spot on the table it started in; the correctness of any resulting color is judged only in the science-correctness rubric, not here.

Scientific and Causal Correctness rubric:
level_1: The solution never plausibly changes color: it stays colorless throughout, or it jumps to a hue that no ferric chloride–salicylate reaction produces (orange, black, fluorescent green, etc.), or a color appears before the reagent is even added, or the powder itself fizzes, bubbles, or changes color on contact with water alone before any reagent is present.
level_2: Some color change happens, but it violates the reaction's causal chain: color appears while water is still being added (before the reagent), or only inside the falling reagent droplet before it mixes into the bulk solution, or only as a thin ring at the liquid's surface that never spreads through the volume, or the final color settles on something other than violet/purple while no dissolution of the powder was ever shown.
level_3: The powder is shown fully dissolving into a clear solution, two drops of reagent are then added, and a violet or purple color appears throughout the solution, but the color is washed out (e.g., a pale lavender fighting a bright background), or it appears and then fades out before the clip ends, or flecks of undissolved powder persist alongside the color change.
level_4: Everything for score 3 holds, and the violet/purple color is fully saturated, even across the whole solution, and holds steady to the end of the clip, appearing only once the reagent has fully mixed in, but the water phase shows a slight haze not explained by incomplete dissolution, or the reagent droplet briefly sits as a separate layer before blending in, or the color spreads in visible streaks rather than blooming evenly.
level_5: Everything for score 3 and score 4 holds, and in addition: the solution is optically clear right up until the reagent is added, the reagent blends in without any droplet lingering visibly, the violet/purple color blooms through the whole solution in one continuous transition, the final hue is unambiguously violet/purple with no brown, gray, or blue cast, no glare or reflection is mistaken for a color shift, and no sediment, cloudiness, or layering suggests the powder never fully dissolved.

Spatiotemporal Consistency rubric:
level_1: Between one frame and the next, the test tube snaps to a different spot on the table with no hand seen carrying it, or the tube shown mid-pour is swapped for a visibly different tube (different width, cap, or fill level); the powder or liquid changes shape or volume with nothing touching it; a reagent droplet is simply sitting inside the solution with no dropper or hand ever shown delivering it; the tabletop scene snaps from bright to dim (or back) with no lamp, hand, or object passing through to explain it; the camera angle or zoom jumps between shots.
level_2: The test tube slides across the table (shifting by more than roughly a third of its width) without the hand visibly pushing or lifting it; the dropper tip touches the rim of the tube or dips into the liquid before releasing its drop; loose powder appears to hover just above the bottom of the tube instead of resting on the glass; a drop of water or reagent follows a curved or upward path into the tube instead of falling straight down; the dropper is momentarily missing from view mid-motion and then reappears in a different position.
level_3: The test tube stays put on the table the whole time; the hand only enters the frame to place the powder, pour the water, or squeeze the dropper, then withdraws cleanly; droplets fall straight down into the solution; the powder settles and dissolves without any unexplained movement; a brief, easy-to-miss moment where the hand or dropper partially blocks the view of the tube, or a short soft-focus moment during the pour, is still acceptable.
level_4: Everything for score 3 holds, and in addition: the two reagent droplets each fall as a distinct drop rather than part of a continuous stream; the powder finishes dissolving and the water surface settles before the dropper enters the frame; the tube, liquid, and tabletop show no flicker or strobing from one frame to the next; only one small slip is allowed, such as the hand briefly leaving the frame right as the second droplet lands.
level_5: Everything for score 3 and score 4 holds, and in addition: the tube never jumps position, size, or angle at any point in the clip; the video never freezes, skips ahead, or speeds up; the tube keeps its cylindrical shape and the liquid inside keeps a flat, level surface throughout; the moments of powder placement, water pouring, droplet impact, and any resulting color change are each fully visible, with no hand, dropper, or camera angle blocking them exactly when they happen.