Domain: Healthcare — Pharmaceutical Chemistry
Target concept: Identification of Sulfonamides (Diazotization Coupling Colorimetric Method)

Video generation prompt: Place the sulfonamide sample solution in a test tube and cool it in an ice-water bath. Add dilute hydrochloric acid, followed by sodium nitrite solution to form the diazonium salt. Finally, add the alkaline coupling reagent solution while gently shaking. Clearly demonstrate the order of reagent addition, the glassware used, the liquid handling procedures, and the smooth transition between each step.

Evaluation guide:
(i) Target concept: Diazotization-coupling colorimetric detection of sulfonamides requires strict thermal control (cold), sequential reagent addition (acid → nitrite → coupling agent), and pH-dependent coupling to yield a diagnostic red-violet azo dye.
Minimum mechanism: Diazonium salt formation is unstable above 5°C and decomposes if warmed; coupling only proceeds rapidly under alkaline conditions; color intensity and hue depend on complete, homogeneous reaction post-mixing.
(ii)Storyline: [Frame-locked fixed viewpoint] → Test tube with clear liquid enters view and is placed into visible ice-water bath → Dilute hydrochloric acid is dispensed into tube → Sodium nitrite solution is dispensed into same tube → Alkaline coupling reagent is dispensed into same tube → Hand gently shakes tube horizontally for ~1 s → Liquid transforms uniformly to red-violet/magenta hue, filling entire visible column; all steps occur in single continuous take with no cuts, no object replacement, and no lighting shift; color must not appear before final shake completes.

Manual:
Experimental Procedure
1. Place sulfonamide sample solution in a clean test tube.
2. Submerge test tube in ice-water bath for cooling.
3. Add dilute hydrochloric acid dropwise.
4. Add sodium nitrite solution dropwise.
5. Add alkaline coupling reagent solution dropwise, then gently shake.
Observation of Experimental Phenomena
Uniform red-violet or magenta color develops only after alkaline coupling reagent addition and gentle shaking.
Summary of Experimental Principles
Sulfonamides undergo diazotization in cold acidic medium to form diazonium salts, which couple with alkaline naphthol-type reagents to form colored azo dyes.

Prompt Grounding rubric:
level_1: No test tube or sample solution is shown; or no ice-water bath appears; or none of dilute hydrochloric acid, sodium nitrite solution, or the alkaline coupling reagent is visibly added to the tube; essentially none of the required reagent-addition steps is depicted.
level_2: At least one object from the setup is present (e.g., the test tube or a single reagent container), but the reagents are added in a sequence that clearly does not match acid-then-nitrite-then-coupling-reagent, or the ice-water bath never appears, or at least two of the required steps (cooling, acid, nitrite, coupling reagent, shaking) are missing entirely.
level_3: The test tube with sample solution sits in a visible ice-water bath, and all three reagents (dilute hydrochloric acid, sodium nitrite solution, and the alkaline coupling reagent) are each shown as visually distinct liquids added to the tube; at least two of the three additions occur in the correct relative order (acid before nitrite, or nitrite before the coupling reagent), but one step is either out of order or missing, and the gentle shake at the end is absent or hard to see.
level_4: The test tube stays in the ice-water bath while all three reagents are added in the correct order (dilute hydrochloric acid first, sodium nitrite solution second, and the alkaline coupling reagent third), and the tube is gently shaken only after the third addition; the same tube and camera framing are used throughout with no swapped or duplicated glassware, and no extra step is inserted.
level_5: In addition, each of the three reagent additions is a clearly separate pour (never two reagents entering the tube at the same time), the tube remains visible and stays in the ice-water bath for the entire sequence up to the final shake, the shake itself is brief and gentle and happens strictly after the coupling reagent is added and before any color is shown developing, and no cut, flash, or object swap breaks the continuity of the sequence.

Scientific and Causal Correctness rubric:
level_1: No color change happens at any point, or the final liquid turns a color unrelated to azo dye chemistry (e.g., blue, green, or bright purple) instead of red-violet/magenta.
level_2: A color appears, but not for the right reason: for example it shows up before the coupling reagent is added, or before the acid and nitrite steps are both complete, or the final color is yellow/orange rather than red-violet/magenta. Any of these breaks the diazotization-then-coupling causal chain.
level_3: The liquid only changes color after the alkaline coupling reagent is added, and it ends up a single, fairly uniform red-violet or magenta shade consistent with a sulfonamide azo dye; however, the color either appears before the shake is finished, or appears while the tube looks like it has already left the ice-water bath, or looks patchy/streaked rather than blended through the liquid.
level_4: The red-violet/magenta color appears only after both the coupling reagent has been added and the gentle shake has taken place, and it is even and consistent throughout the liquid; no color of any kind appears before the coupling step; the tube stays in the ice-water bath during the acid and nitrite additions; and no intermediate color (like yellow or a brown haze) shows up along the way.
level_5: In addition, the color's appearance clearly follows the shake (nothing colored is visible beforehand, and the red-violet/magenta tone appears within a short, continuous stretch of the clip right after shaking finishes), and it doesn't fade, streak, or turn cloudy afterward; the final hue reads clearly as red-leaning violet/magenta, not blue, not plain purple, and not pink.

Spatiotemporal Consistency rubric:
level_1: The test tube, ice-water bath, or a reagent container disappears from one frame and is simply gone or replaced in the next with no motion shown getting it there; the lighting or background changes abruptly mid-sequence; there is a visible jump cut between steps; or the liquid level changes with no pouring motion shown to explain it.
level_2: The test tube shifts position or rotates by a large, unexplained amount (roughly more than 30 degrees) with no hand visibly moving it; the ice-water bath vanishes during one step and reappears later; a reagent container's location or orientation changes between one addition and the next; or the shaking motion starts and stops abruptly rather than flowing continuously.
level_3: Small imperfections are visible but nothing breaks the scene's coherence: for example a slight camera wobble while pouring, the test tube being briefly hidden by a hand during one step, or a momentary flicker in the lighting while shaking, but no object disappears, warps, or teleports at any point.
level_4: The test tube stays centered and upright throughout; the ice-water bath remains fully visible and doesn't move; each reagent container enters the frame from a consistent direction and holds a stable position while pouring; every pour is smooth and unbroken; and the final shake is one continuous, gentle back-and-forth motion without pausing or reversing partway through.
level_5: In addition, the test tube and dropper/container show no visible shaking or drifting beyond the motions the procedure calls for; the foreground (test tube) and background (bath, bench) move together consistently with no separation or floating; the liquid's surface and its color are never hidden by heavy motion blur; and each transition between actions (stop pouring, lift the container, move to the next reagent, begin shaking) follows the previous one smoothly with no visible pause or overlap.