Domain: Healthcare — Clinical Laboratory Science
Target concept: Nitroprusside Test for Urine Ketones

Video generation prompt: Collect 1 mL of urine from a patient with excessive urinary ketones into a clear tube, add 0.3 mL of sodium nitroprusside reagent, then add 2 drops of glacial acetic acid and mix thoroughly. Tilt the tube and carefully layer 1 mL of concentrated ammonium hydroxide (ammonia solution) down the inner wall without mixing, then observe the junction between the two layers.

Evaluation guide:
(i) Target concept: The nitroprusside-ketone (acetoacetate) condensation forming a violet-purple/pink chromophore requires alkaline conditions; acidifying the urine with glacial acetic acid alone does not produce the color. A layer of concentrated ammonia placed on top of the acidified urine without mixing creates a localized alkaline zone at the liquid-liquid interface, where the colored complex forms (Legal's ring test).
Minimum mechanism: Acetoacetate + sodium nitroprusside (mixed into acidified urine) + concentrated ammonia layered on top (unmixed) → alkaline microenvironment develops at the interface → [Fe(CN)5NO]2−-acetoacetate adduct forms there → visible absorption near 540 nm → a purple-to-pink ring/zone appears specifically at the boundary between the two layers.
(ii) Storyline: [Start: Static shot of a labeled conical urine tube containing 1 mL pale yellow liquid.] → [Action 1: A dropper enters from the right and dispenses sodium nitroprusside into the tube, no color change.] → [Action 2: A second dropper dispenses 2 drops of glacial acetic acid; the tube is swirled, still no color change.] → [Action 3: The tube is tilted at an angle and a third dropper slowly releases concentrated ammonium hydroxide along the inner wall so it forms a distinct layer on top of the acidified urine, without mixing the two.] → [Action 4: The tube is returned upright and held steady; a purple-to-pink ring becomes visible at the boundary between the two layers over several seconds and strengthens.] → [Final frame: Stable close-up of the tube showing the colored ring at the layer junction, with the lower urine layer and upper ammonia layer still visually distinguishable. All actions are shown from a fixed frontal viewpoint; no cutaways or POV shifts.]

Manual:
Experimental Procedure
1. Place 1 mL urine in a clear conical tube.
2. Add 0.3 mL sodium nitroprusside reagent using a dropper; mix.
3. Add 2 drops glacial acetic acid using a dropper; mix thoroughly.
4. Tilt the tube and carefully layer 1 mL concentrated ammonium hydroxide (ammonia solution) down the inner wall so it sits above the acidified urine without mixing.
5. Return the tube upright and observe the boundary between the two layers for several minutes.
Observation of Experimental Phenomena
No color develops while only urine, nitroprusside, and acetic acid are present. After the concentrated ammonia layer is added, a purple-to-pink ring or zone develops at the interface between the acidified urine and the ammonia layer.
Summary of Experimental Principles
Sodium nitroprusside reacts with acetoacetate (a ketone body) to form a violet-purple complex, but this condensation requires alkaline conditions. Glacial acetic acid keeps the bulk urine acidic; the layered concentrated ammonia creates a localized alkaline zone at the interface, so the colored complex forms specifically at that junction rather than throughout the acidic solution. Ring/zone color intensity correlates with urinary ketone concentration.

Prompt Grounding rubric:
level_1: No urine-filled tube is shown; no sodium nitroprusside source or dropper is present; no glacial acetic acid source or dropper is present; no concentrated ammonia source or dropper is present; no layering or mixing action occurs.
level_2: At least one correct object appears (e.g., a urine-filled tube) but two or more of the following are missing or wrong: sodium nitroprusside reagent, glacial acetic acid, concentrated ammonia; steps occur out of order (e.g., ammonia layered before acetic acid is added); or a volume is clearly mismatched (e.g., urine visibly far from 1 mL, nitroprusside far from 0.3 mL, acetic acid not resembling 2 drops, or the ammonia layer far from 1 mL).
level_3: The urine tube, sodium nitroprusside source, glacial acetic acid source, and concentrated ammonia source are all shown; the order matches: urine present first, then nitroprusside added, then acetic acid added and mixed, then ammonia layered on top; each addition is a visually distinct, unambiguous action; no tool or container is swapped for a different one mid-scene.
level_4: Everything described for level 3 is shown, and in addition: sodium nitroprusside and acetic acid are delivered by dropper/pipette rather than poured from a bottle rim; the tube stays upright and stationary during the nitroprusside and acid additions; for the ammonia step the tube is deliberately tilted and the ammonia runs down the inner wall rather than dripping straight into the liquid; the tube is recognizable as a clinical specimen tube (conical shape with a frosted labeling area).
level_5: Everything described for level 4 is shown, and in addition: each dropper tip touches the tube's inner wall or liquid surface when dispensing rather than releasing in mid-air; the tube is returned upright after the ammonia layer forms and held steady for observation; a clean, undisturbed boundary between the acidified urine layer and the ammonia layer is visible with no stirring together of the two; separate droppers are used for the nitroprusside, the acetic acid, and the ammonia with no reuse across reagents.

Scientific and Causal Correctness rubric:
level_1: No color develops at any point; or a color unrelated to the ketone reaction appears (e.g., blue, green, black, or a cloudy white precipitate); or a colored ring appears before the ammonia layer is added; or a color forms and then fades completely to colorless while the two layers are still in contact.
level_2: A color appears but at the wrong stage (e.g., while only nitroprusside is present, before the acid or ammonia steps) or in the wrong place (spread evenly through the whole tube rather than localized near the layer boundary); or the final hue is clearly outside violet/purple/pink (e.g., yellow-orange or reddish-brown); or the color appears and then vanishes before the observation phase ends.
level_3: No color change occurs while only urine, sodium nitroprusside, and acetic acid are present; once the concentrated ammonia is layered on top without mixing, a purple-to-pink color develops specifically at (or spreading from) the boundary between the acidified urine and the ammonia layer, and this color persists once formed.
level_4: Everything described for level 3 is shown, and in addition: the colored ring/zone visibly strengthens over the observation period rather than appearing instantly at full intensity; the color stays concentrated near the interfacial region rather than uniformly saturating both layers; no unrelated coloration (e.g., yellow cloudiness, brown flecks) competes with or masks the purple-pink zone; the tube material is clear enough that its own material does not tint the observed hue.
level_5: Everything described for level 4 is shown, and in addition: the ring/zone reads specifically as purple-to-pink, comparable to a dilute potassium-permanganate hue, rather than orange, brown, or plain red; the layers above and below the colored boundary remain visibly distinguishable from each other in clarity/tint; no residual pale-yellow tint from unreacted nitroprusside lingers in the lower layer once the ring is established; the colored zone appears even across the visible width of the tube rather than patchy or one-sided.

Spatiotemporal Consistency rubric:
level_1: The tube, droppers, or liquid layers break physical continuity: e.g., the tube's position or tilt angle changes abruptly between shots with no visible transition, a dropper appears at the tube without having moved there, the room lighting or shadow pattern jumps noticeably from one step to the next, or the tilting motion used to layer the ammonia skips straight from upright to tilted with no in-between motion.
level_2: Less severe but still noticeable breaks: a dropper's path from its source to the tube is skipped so it is simply already at the tube in the next shot; the tilt-and-return motion for the ammonia layering pauses and restarts more than once; or a highlight/reflection on the tube's surface disappears in one shot and reappears identically later without a visible cause.
level_3: The tube stays in the same place in the frame throughout, aside from the deliberate tilt for ammonia layering; each dropper always enters from the same side of the frame; no object is ever missing from a shot and then present again without visibly moving into place; the overall room lighting stays comparable in brightness and direction from the first shot to the last.
level_4: Everything described for level 3 is shown, and in addition: the tube's tilt for ammonia layering and its return to upright are smooth continuous motions rather than sudden jumps; the swirling motion after the acetic acid is added keeps one consistent rotation direction throughout; the reagent droppers move along visible paths toward and away from the tube rather than snapping between positions.
level_5: Everything described for level 4 is shown, and in addition: the moving dropper tips and tube remain clearly recognizable in shape during motion rather than smearing into an unrecognizable blur; the background behind the tube does not appear to shift relative to the tube during the tilt or mixing motions; any glass reflection or highlight on the tube moves in a way that stays consistent with a single, unmoving light source throughout the sequence.