Domain: Healthcare — Pharmaceutical Chemistry
Target concept: Detection of Cyanide Impurities in Medicines

Video generation prompt: Take a small amount of the sample and place it in a transparent test tube. Add 3 mL of distilled water to dissolve the sample, then add 1 mL of sodium hydroxide solution and 1 drop of ferrous sulfate solution. After shaking uniformly, add dilute hydrochloric acid to acidify, and observe the changes.

Evaluation guide:
(i) Target concept: Detection of cyanide via Prussian blue formation requires sequential alkaline ferrous complexation followed by acid-enabled Prussian blue precipitation.
Minimum mechanism: Ferrous sulfate must supply Fe²⁺; NaOH enables ferrocyanide formation; ambient O₂ or trace Fe³⁺ must be present to generate Fe³⁺ *in situ*; acidification protonates and drives insoluble Prussian blue nucleation; all steps must occur in strict order for blue precipitate to appear exclusively post-HCl.
(ii)Storyline: [Frame 0–1] Solid sample placed into stationary transparent test tube. [Frame 2–3] Distilled water poured in, dissolving sample into clear solution. [Frame 4–5] NaOH solution added, no immediate change. [Frame 6] Single ferrous sulfate drop contacts solution. [Frame 7] Uniform shaking motion mixes contents. [Frame 8] Dilute HCl added, no color yet. [Frame 9–10] Within 1 second post-acidification, deep blue granular precipitate emerges and remains stable. All events occur in fixed frontal view; tube never leaves frame; lighting remains neutral and consistent; no external interference or editing breaks temporal flow.

Manual:
Experimental Procedure
1. Place solid sample in transparent test tube.
2. Add 3 mL distilled water; observe dissolution.
3. Add 1 mL sodium hydroxide solution.
4. Add 1 drop ferrous sulfate solution; shake uniformly.
5. Add dilute hydrochloric acid to acidify.
Observation of Experimental Phenomena
Deep blue granular precipitate forms only after acidification.
Summary of Experimental Principles
Cyanide reacts with ferrous ions under alkaline conditions to form ferrocyanide; upon acidification, ferrocyanide reacts with excess Fe³⁺ (from air oxidation or impurity) to yield Prussian blue (Fe₄[Fe(CN)₆]₃), confirming cyanide presence.

Prompt Grounding rubric:
level_1: No transparent test tube is shown; no solid sample is placed in it; none of distilled water, sodium hydroxide solution, or ferrous sulfate solution can be identified; no acidification with hydrochloric acid is shown; there's no visible sequence of adding reagents at all.
level_2: A transparent test tube holds a solid sample, but no liquid is ever added to it; or only one reagent (say, just water) goes in with nothing following; the additions of sodium hydroxide, ferrous sulfate, and hydrochloric acid are missing or impossible to tell apart.
level_3: A transparent test tube with the solid sample is shown; distilled water is added and the sample visibly dissolves; sodium hydroxide solution and ferrous sulfate solution are both added as two separate, visible additions; dilute hydrochloric acid is then added to acidify the mixture: all six items (tube, sample, water, NaOH, FeSO4, HCl) appear, and the order of addition is mostly clear, though one step (e.g., a single drop versus a stream, or whether shaking happens) may be hard to pin down.
level_4: All six items are clearly identifiable: the transparent test tube, the solid sample, distilled water, sodium hydroxide solution, ferrous sulfate solution (added as a single visible drop), and dilute hydrochloric acid; the five steps happen in the correct order: sample placement, water addition and dissolution, NaOH addition, the FeSO4 drop, then HCl addition; uniform shaking is visible right after the FeSO4 drop; no step is skipped or extra; the same tube stays in view from the same camera angle throughout.
level_5: Every 4-point requirement is met, with the following also true: the ferrous sulfate addition is unmistakably a single drop, not a stream or several droplets; the shaking motion is smooth and continuous, without pausing or looking incomplete; the hydrochloric acid is added after the shaking finishes and before any color appears; nothing enters or leaves the frame partway through; there's no cut, zoom, or re-angling that breaks the single continuous shot; NaOH and HCl remain visually distinguishable from each other rather than looking like the same clear liquid.

Scientific and Causal Correctness rubric:
level_1: No color change happens at any point; no blue precipitate ever forms; every liquid still looks the same at the end as at the start; nothing about the sequence suggests a chemical reaction took place.
level_2: Some color change happens, but it isn't consistent with Prussian blue forming (say, only yellow, red, or green appears); a precipitate forms but isn't blue or isn't granular; or a blue color shows up before the hydrochloric acid is added, breaking the required order (dissolve, then alkaline mixing, then acidify).
level_3: A blue substance appears in the tube only after the hydrochloric acid is added; it looks particulate or cloudy rather than like a uniform blue dye dissolved in solution; it is absent right up until the acid goes in and present shortly after; even if the blue is faint or partly hard to see, its presence, its blue color, and its timing relative to the acid are all clear.
level_4: The blue precipitate appears only after acidification, never before; it's clearly granular or turbid rather than a clear blue solution; its blue color is rich and unambiguous, not muddy, greenish, or purplish; nothing else in the tube is a competing dominant color; the sequence of dissolving the sample, mixing in the alkaline ferrous sulfate, then acidifying, and only then seeing blue, holds up throughout.
level_5: The 4-point criteria all hold, and further: the blue precipitate sits within the liquid itself rather than clinging only to the glass walls or floating in an unnatural way; no in-between color (like a greenish tinge before acidification) gets mistaken for the final blue result; the blue stays put and doesn't fade or bleach out by the last frame; nothing like a lighting glare or color fringing on the glass is mistaken for the blue precipitate.

Spatiotemporal Consistency rubric:
level_1: The test tube vanishes from view and then reappears somewhere else in the frame; the sample jumps straight from the person's hand into the tube with no placement motion shown; reagents appear already sitting inside the tube without any pouring or dropping motion; the lighting or shadows suddenly swing in a way that has nothing to do with any action taking place; the tube's shape breaks (e.g., it visibly bends or its bottom disappears).
level_2: The test tube's size or shape changes noticeably between shots; a reagent's container is shown, then disappears from view right after it's used without any indication it was set down; the shaking motion starts and stops abruptly with no visible speeding up or slowing down; the acid is added while the tube is off to the side or partly hidden, then the tube reappears centered in frame; the lighting flickers or the shadow pattern changes inconsistently between one action and the next.
level_3: A hand blocks view of the tube only briefly during one of the additions before moving away again; a slight wobble occurs during shaking but never actually hides the tube from view; the shadow shifts slightly during acidification without ever obscuring the contents; aside from these small lapses, the tube stays fully visible and intact throughout, and the whole sequence plays out in one continuous shot with no cuts or reframing.
level_4: No breaks appear in the tube's structure or in the motion of the actions: the tube keeps the same shape, clarity, and position throughout; every addition (pouring or dropping) happens with a smooth, continuous motion that settles naturally on contact; the shaking has an even, back-and-forth rhythm without pausing or jerking; any shift in lighting or shadow direction lines up with whatever action is happening on screen rather than occurring on its own; the tube's contents are never hidden from view during any of the key steps (placing the sample, dissolving it, adding the FeSO4 drop, acidifying, and watching the result).
level_5: The 4-point criteria all hold, plus: every motion (pouring, dropping, shaking) flows smoothly from one frame to the next without freezing or skipping; the glass of the tube consistently bends light the same way, so the liquid's surface and the precipitate inside look correctly positioned through the glass; foreground and background elements shift together in a way that looks physically consistent; the camera holds one fixed position with no panning, tilting, or drifting; nothing in the shot looks unnaturally blurred or unnaturally sharp during motion; the pacing of pouring and shaking looks like real time, neither sped up nor slowed down.