Domain: Healthcare — Pharmaceutical Chemistry
Target concept: Phenytoin Sodium Assay

Video generation prompt: An appropriate amount of sodium phenytoin solution is placed in a test tube. A few drops of silver nitrate reagent are added, the test tube is gently shaken, and the change in the solution is observed.

Evaluation guide:
(i) Target concept: Precipitation reaction between phenytoin anion and silver ion to form insoluble silver phenytoin.
Minimum mechanism: Silver nitrate must dissociate to release Ag⁺; phenytoin anion must be present in solution and mobile; ionic collision must occur; product must exceed solubility limit to nucleate and grow as solid phase.
(ii)Storyline: [Frame 0] Static shot: upright test tube with colorless-to-pale-yellow liquid at ~2/3 height, meniscus visible. [Frame 1–3] Dropper enters top-of-frame, vertically aligned; 2–4 spherical droplets detach and fall under gravity, striking liquid surface with visible ripple. [Frame 4–6] Hand grasps tube near base and performs smooth, low-amplitude horizontal oscillation for ~2 seconds; liquid sloshes coherently. [Frame 7–10] A white (or faintly off-white) granular precipitate emerges first near the impact zone, then spreads uniformly through the liquid; particles remain suspended in a diffuse cloud before gradually settling; supernatant stays clear and colorless. Perspective: fixed frontal close-up, centered on tube mid-section; no occlusion; full visibility of liquid interior and precipitate dynamics throughout.

Manual:
Experimental Procedure
1. Place a test tube containing sodium phenytoin solution (colorless to pale yellow).
2. Add 2–4 drops of silver nitrate reagent using a dropper.
3. Gently shake the test tube for ~2 seconds.
Observation of Experimental Phenomena
A white (off-white) precipitate forms and remains suspended briefly before gradual settling; the supernatant liquid stays clear and colorless.
Summary of Experimental Principles
Sodium phenytoin contains phenytoin anion, which reacts with Ag⁺ to form insoluble silver phenytoin — a white (off-white) precipitate — confirming presence of phenytoin ion.

Prompt Grounding rubric:
level_1: No test tube appears at all, or no sodium phenytoin solution is shown in it, or no silver-nitrate dropper bottle appears, or the tube is never shaken, or the video never lingers on the tube's contents afterward; none of the setup or actions from the prompt are shown.
level_2: The test tube holds some liquid, but its color doesn't read as colorless-to-pale-yellow; or a dropper/reagent bottle appears without any droplet actually leaving it and entering the tube; or the shaking action is missing or happens to some other object instead of the tube; or nothing about the tube's contents visibly changes after the drops are added.
level_3: A test tube holding a colorless-to-pale-yellow liquid is shown; a dropper delivers at least one visible droplet into the liquid; the tube is then gently shaken; the camera keeps its attention on the tube's contents after the drops go in.
level_4: Beyond that: the dropper is held upright with its tip aligned over the tube opening so droplets fall freely into the liquid without splashing outside the tube; the hand shakes the tube by holding it near its base with a small side-to-side motion kept close to the tube itself; nothing besides the tube, dropper, and hand dominates the shot during this sequence.
level_5: Beyond that: the dropper releases a small, individually countable number of droplets (2 to 4) into the tube; the shaking begins almost immediately after the last droplet lands (within about a second); the camera stays focused on the tube's interior without cutting away, zooming out, or reframing from the moment the droplets enter until the shaking ends.

Scientific and Causal Correctness rubric:
level_1: No precipitate ever forms, and the liquid stays clear and unchanged in color throughout; no cloudiness, haze, or solid material appears at any point.
level_2: The liquid's own color shifts (e.g., turns yellow, tan, or brown) but no actual solid precipitate ever forms; or a precipitate does appear but it is distinctly colored (yellow, tan, or brown) rather than white/off-white; or a cloudy solid is already present before the silver-nitrate drops ever reach the liquid.
level_3: After the silver-nitrate drops are added and the tube is shaken, a white or off-white precipitate appears in the liquid, either staying suspended or settling slowly; the liquid itself keeps its original colorless-to-pale-yellow look with no darkening or browning.
level_4: Building on that: the white precipitate appears only once the shaking begins, not while the droplets are still falling; it spreads through the whole liquid volume rather than staying clumped only where the drops first landed; and it does not dissolve or vanish partway through the shaking.
level_5: Building on that: the white precipitate looks distinctly granular rather than a smooth gel or a film; it stays visibly suspended in the liquid for at least two seconds after the shaking stops before beginning to gradually settle; and it never clumps into a few large lumps or coats the inside of the tube wall as a film.

Spatiotemporal Consistency rubric:
level_1: The test tube's position, size, or tilt changes abruptly with no hand ever moving it; the liquid inside suddenly changes level or ripples with nothing (no falling droplet, no shake) to explain it; the room lighting flashes or a shadow sweeps across the tube with no matching cause; a falling droplet drifts upward or hangs in mid-air instead of falling under gravity.
level_2: The tube stays in one place but rotates by a large angle with no hand touching it; a droplet leaves the dropper but disappears before ever reaching the liquid surface; the shaking motion looks jerky or stop-start rather than smooth; or the precipitate appears all at once filling the whole tube, with no visible spreading or buildup over time.
level_3: The test tube stays fixed in the frame at a constant angle; each droplet falls straight down and visibly meets the liquid surface; the shaking motion is smooth and holds a steady rhythm and amplitude; the precipitate builds up gradually (first as a faint local haze near where the drops landed, then thickening) rather than appearing instantly, starting shortly after the shaking begins.
level_4: Building on that: the liquid's meniscus flexes naturally with the shaking motion instead of looking stiff or breaking apart oddly; the ripple from each droplet's impact spreads outward and fades naturally instead of freezing or vanishing abruptly; the tube's shape and edges stay sharp and steady from one moment to the next with no warping or flicker.
level_5: Building on that: the camera holds one fixed, unmoving view of the tube for the entire sequence; the highlight/reflection on the glass wall stays in the same place and shape throughout, shifting only as much as the liquid's own motion would cause; the liquid keeps a coherent, continuous reflection of light while it sloshes; and once the shaking stops, the suspended precipitate settles toward the bottom smoothly, without freezing in place or jumping to a new configuration between moments.