Domain: Healthcare — Pharmaceutical Chemistry
Target concept: Detection of Naturally Occurring Nitrites (Griess Reagent Method)

Video generation prompt: Add the sulfanilic acid reagent and gently mix. Add the N-(1-naphthyl)ethylenediamine reagent, shake slightly, and observe the test tube during the reaction.

Evaluation guide:
(i) Target concept: Azo dye formation via sequential diazotization and coupling in aqueous solution.
Minimum mechanism: Presence of nitrite ion in sample; acidic environment (implied by reagents); stoichiometric compatibility of sulfanilic acid and N-(1-naphthyl)ethylenediamine; aqueous solubility of all species; thermal stability of intermediate diazonium salt at room temperature.
(ii)Storyline: [Frame 0] Static shot: upright test tube with colorless liquid, two labeled reagent bottles adjacent in view. [Frame 1–2] Sulfanilic acid bottle tip approaches and dispenses reagent into test tube; liquid remains colorless. [Frame 3] Hand swirls test tube: meniscus oscillates, no color shift. [Frame 4–5] N-(1-naphthyl)ethylenediamine bottle tip approaches and dispenses reagent into same test tube. [Frame 6] Hand taps test tube: liquid oscillates uniformly. [Frame 7] Within a few seconds after tapping ceases, pink-to-magenta color fills entire liquid volume, persisting to end. Perspective: fixed frontal close-up; test tube center-framed; no occlusion during critical actions; full visibility of liquid column throughout.

Manual:
Experimental Procedure
1. Place a clear test tube containing colorless nitrite-containing sample solution.
2. Add sulfanilic acid reagent dropwise; gently swirl test tube to mix.
3. Add N-(1-naphthyl)ethylenediamine reagent dropwise; tap test tube lightly to shake.
Observation of Experimental Phenomena
After step 3, the solution develops a distinct pink-to-magenta color — no color change occurs after step 2 alone.
Summary of Experimental Principles
Nitrite ions react with sulfanilic acid under acidic conditions to form diazonium salt; this salt couples with N-(1-naphthyl)ethylenediamine to produce a stable azo dye with characteristic pink-to-magenta color — the Griess reaction.

Prompt Grounding rubric:
level_1: No test tube is shown; neither the sulfanilic acid bottle nor the N-(1-naphthyl)ethylenediamine (NED) bottle appears; there is no hand or tool adding anything to a test tube, and no two-step addition sequence occurs anywhere in the video.
level_2: A test tube is present and stays still; only one of the two reagent bottles (sulfanilic acid or NED) is visible; neither reagent is ever added to the test tube, and no mixing or shaking action occurs.
level_3: The test tube and both the sulfanilic acid bottle and the NED bottle are visible; sulfanilic acid is added to the test tube and gently mixed (swirl or tap); NED is added afterward and the tube is shaken; the two additions and their respective mixing/shaking actions occur in this order.
level_4: Everything expected at the score 3 level holds; in addition, both bottles carry a readable label or a distinct visual identifier (e.g., differently colored caps or printed names) so a viewer can tell them apart; the test tube stays in one fixed spot for the whole sequence; no hand or tool blocks the view of the tube during either addition or during mixing/shaking; nothing extraneous enters the frame.
level_5: Everything expected at the score 4 level holds; in addition, each reagent goes directly into the tube with no spill or missed pour; the mixing motion stays confined to the tube itself, with no separate pouring gesture after the liquid is added; the shaking motion (short vertical taps) looks visibly distinct from the earlier swirling/mixing motion; the tube stays upright and steady before, during, and after every action; the whole sequence plays as one continuous shot from a fixed frontal angle with no cuts or zooms.

Scientific and Causal Correctness rubric:
level_1: The liquid in the test tube stays colorless/clear through both additions, or a color appears with no visible connection to either reagent being added; the reaction's characteristic color change never happens.
level_2: A color does appear, but it is the wrong hue for this reaction (e.g., blue, green, yellow, or an immediate dark brown/black instead of pink-to-magenta); or the color appears before either reagent is added; or a color appears right after the sulfanilic acid step alone and never changes further once NED is added.
level_3: The liquid is colorless before either reagent is added and stays colorless after sulfanilic acid is added and mixed; only after NED is added and the tube is shaken does a pink-to-magenta color appear, and that color persists for the rest of the video.
level_4: Everything expected at the score 3 level holds; in addition, the pink-to-magenta color spreads evenly through the liquid rather than in streaks or isolated patches, visibly deepening from a lighter pink toward magenta while or just after shaking, with no competing tint (no orange rim, no yellow cast, no fading) appearing at any point.
level_5: Everything expected at the score 4 level holds; in addition, the final color stays within the pink-to-magenta family with no drift toward an unrelated hue such as blue or green; the color fills the whole liquid column with no cloudiness or layering; the color becomes visible within a few seconds of the shaking ending rather than only after a long unexplained pause; the liquid shows no unrelated washing-out or darkening once the color has appeared.

Spatiotemporal Consistency rubric:
level_1: The test tube is not continuously present: e.g., it vanishes and reappears, a reagent bottle jumps between positions with no travel shown between frames, a hand appears from off-screen and deposits liquid outside the tube before instantly appearing inside it, the scene's brightness or shadows jump abruptly between one moment and the next, or the tube's shape changes discontinuously.
level_2: The test tube stays visible but shifts sideways or vertically by more than its own width between the two additions; the liquid stream separates from the bottle tip with no visible trail connecting them; the mixing motion starts before the reagent has actually reached the liquid; the shaking motion starts before the NED reagent has fully entered the tube; the lighting flickers or the shadow direction changes between consecutive moments.
level_3: The test tube holds one fixed spot in the frame throughout; each reagent's stream visibly runs from the bottle tip into the liquid; the mixing action starts only once the sulfanilic acid has fully entered the tube; the shaking action starts only once the NED has fully entered the tube; the brightness and the direction of shadows on the tube and bench stay the same from the first addition through the last; nothing in the scene flickers, warps, or changes shape unexpectedly.
level_4: Everything expected at the score 3 level holds; in addition, the bottle and hand motions look physically natural, with no sudden jerks and no liquid pausing mid-air unsupported; the hand or dropper keeps a consistent size and distance relative to the tube; the hand never appears to pass through the tube's wall; the shaking action never appears in the frame order before its corresponding addition.
level_5: Everything expected at the score 4 level holds; in addition, the liquid surface stays smooth while each reagent is poured in, without splashing or bubbling; the swirl from mixing appears only during the mixing action and settles before the next step begins; the oscillation from shaking appears only during the shaking action and dies down fully before the color is shown developing; there is no stutter, repeated frame, or jump in the motion at any point in the sequence.