Domain: Healthcare — Nutrition and Food Hygiene
Target concept: Sulfamoyl Detection

Video generation prompt: Ten milliliters of a beverage sample containing saccharin were placed in a test tube. Dilute hydrochloric acid solution was added, the mixture was thoroughly shaken, and then left standing at room temperature. A photograph was taken continuously with the image aligned with the test tube.

Evaluation guide:
(i) Target concept: Visual confirmation of saccharin's acidic sulfamoyl (cyclic sulfonimide N-H) group through acid-driven precipitation of the free acid from its water-soluble sodium salt.
Minimum mechanism: Dilute hydrochloric acid protonates the acidic sulfonimide nitrogen of the sodium saccharin dissolved in the beverage, converting it into free saccharin (a compound far less soluble in water than its sodium salt), which separates out of solution as a fine white crystalline solid once the acid has mixed through the sample.
(ii)Storyline: [Phase 1: Setup] Test tube enters frame containing beverage-colored liquid; [Phase 2: Reagent Delivery] Dropper/pipette approaches and dispenses dilute hydrochloric acid into the tube; [Phase 3: Mixing] Tube is shaken by hand → fine white cloudiness begins to appear as the acid mixes through the liquid; [Phase 4: Standing & Settling] Tube is set down and left standing at room temperature → white crystalline precipitate continues to develop and settle toward the bottom; [Phase 5: Stabilization & Capture] Tube rests motionless, camera aligns and holds a fixed frame for the photo; all under steady ambient lighting and a fixed viewpoint with no occlusion.

Manual:
Experimental Procedure
1. Place 10 mL beverage sample in a clean test tube.
2. Add dilute hydrochloric acid solution.
3. Shake the tube thoroughly.
4. Leave the tube standing at room temperature.
5. Photograph with camera aligned to the test tube.
Observation of Experimental Phenomena
A fine white crystalline precipitate develops in the liquid as the acid mixes through the sample and continues to accumulate and settle while the tube stands at room temperature.
Summary of Experimental Principles
Sodium saccharin's acidic sulfamoyl (cyclic sulfonimide) nitrogen is protonated by the added hydrochloric acid, converting the water-soluble sodium salt into free saccharin, which is only sparingly soluble in cold water; this insoluble form separates out as a white crystalline precipitate, confirming the presence of the sulfamoyl-bearing saccharin ring in the sample.

Prompt Grounding rubric:
level_1: No test tube present; no beverage sample visible; no acid reagent added; no shaking action or standing/settling period shown; no camera alignment or photograph action shown.
level_2: A test tube holds some liquid, but it is not identifiable as a beverage sample (e.g., plain water); a reagent is added but is not visually distinct from the beverage or is not clearly delivered into the tube; no shaking action or standing period is shown; the camera never settles on or aligns with the tube.
level_3: The test tube visibly contains a beverage-colored liquid; a visually distinct thin liquid is added into the tube via a dropper or pipette; the tube is shaken by hand; however, no standing/settling period is shown before the photograph, or the final camera alignment is missing, or these actions occur on the wrong object.
level_4: All named actions occur on the same tube in order: beverage sample present, dilute hydrochloric acid delivered by dropper/pipette, tube shaken by hand, tube then set down and left undisturbed for a visible interval, and the camera settles into a fixed, centered framing before the photograph; however, the beverage volume or the standing duration is not clearly conveyed.
level_5: All prompt elements are present and unambiguously executed on one continuous tube: the liquid level matches roughly a 10 mL fill; dilute hydrochloric acid is added by dropper/pipette with a visibly distinct appearance as it enters the beverage; the tube is shaken by hand for at least about 2 seconds; the tube is then set down and left standing undisturbed at room temperature for a clearly visible interval; and the final photograph shows the same tube held in one steady, centered framing across several consecutive frames.

Scientific and Causal Correctness rubric:
level_1: No turbidity or precipitate ever forms; the liquid stays clear and its appearance is identical before and after every step; there is no causal connection between adding the acid, shaking, standing, and any visible change in the liquid.
level_2: A visible change occurs, but it is inconsistent with the acid-driven precipitation mechanism: for example the liquid changes color instead of forming a solid, or a colored haze appears, or turbidity appears before the acid is added, or the change appears only while the tube is being shaken and disappears completely once shaking stops with nothing remaining while standing.
level_3: Fine white cloudiness begins to appear in the liquid only once the acid has been added and mixed in by shaking; however, the amount of precipitate does not noticeably change while the tube stands afterward, or patches of the liquid remain clear in a way inconsistent with a uniformly mixed acid, or some cloudiness is visible before the acid contacts the liquid.
level_4: The liquid is clear immediately before the acid is added; fine white turbidity appears during or after shaking and continues to increase or settle toward the bottom of the tube while the tube stands at room temperature; no coloration (pink, green, blue, etc.) appears at any point; by the end of standing, distinctly more solid is visible than right after shaking.
level_5: The sequence unambiguously shows: clear beverage before acid addition, onset of fine white cloudiness during or immediately after shaking as the acid mixes through the sample, progressive settling and thickening of white crystalline solid toward the bottom of the tube while it stands at room temperature, and a stable, visibly turbid or precipitate-bearing tube at the moment of the final photograph, with no coloration, no precipitate before the acid is added, and no redissolving once precipitation has begun.

Spatiotemporal Consistency rubric:
level_1: The test tube's size, shape, or contents change abruptly between shots with no visible cause; the dropper or pipette appears in the frame without having entered it; the tube's position jumps to a new location between the shaking and standing steps; the tube rotates by more than roughly 90 degrees with no hand visibly supporting or turning it; the ambient lighting abruptly swings brighter or darker with no source (e.g., a hand, a camera move) to explain it; or the background or camera framing changes discontinuously between these steps.
level_2: The tube stays recognizable across the video, but shifts abruptly by more than roughly a third of the frame width between one step and the next; the shaking step and the standing/settling step appear to take place against different backgrounds or lighting; the hand or dropper enters and exits the frame in ways that don't match a single continuous action.
level_3: All steps (adding acid, shaking, standing, and photographing) happen to one tube in what reads as a single continuous scene with a consistent background; however, a step transition (e.g., from shaking to standing) is abrupt or unexplained, or the tube's orientation changes briefly in a way that isn't tied to a visible hand action.
level_4: The tube keeps a consistent position, scale, and orientation across the entire sequence except when a hand is visibly moving or holding it; the transition from shaking to standing is shown as a continuous progression (hand releases the tube, tube is set down) rather than a cut; the tube's illumination looks consistent from the shaking step through to the photograph, without sudden brightening or dimming between shots.
level_5: The tube's position, orientation, and framing are continuous throughout, changing only through visible, physically plausible hand movement; the same single tube is used for every step with no substitution; the tube's illumination and cast shadow stay consistent from the moment the acid is added through the final photograph, with no unexplained flashes or dark cuts; the final camera framing for the photograph matches the tube's resting position from the preceding standing step with no jump cut.