Domain: Healthcare — Pharmaceutical Chemistry
Target concept: Identification of Erythromycin Drugs (Sulfuric Acid Colorimetric Method)

Video generation prompt: Transfer an appropriate amount of erythromycin reagent solution into a test tube. Slowly add concentrated sulfuric acid along the inner wall of the test tube using a pipette. Keep the test tube upright, gently shake to mix the contents, and observe the progress of the reaction inside the test tube.

Evaluation guide:
(i) Target concept: Acid-induced chromogenic reaction of erythromycin in concentrated sulfuric acid, requiring interfacial contact, controlled mixing, and time-resolved color development.
Minimum mechanism: Erythromycin must be dissolved in aqueous medium; concentrated H₂SO₄ is fully miscible with the aqueous solution in all proportions but is much denser, so when it is added slowly along the tube wall it sinks and briefly forms a distinct lower layer rather than mixing instantly; reaction initiates at the acid–solution interface due to localized protonation/dehydration of erythromycin; color formation is diffusion-limited before shaking and requires mechanical agitation for homogenization.
(ii)Storyline: Frame 1–2: Upright empty test tube → Frame 3–4: Erythromycin solution added → Frame 5–6: Pipette contacts inner wall, acid begins flowing down → Frame 7: Distinct biphasic layering (upper aqueous, lower acid) visible → Frame 8: Reddish-brown band appears sharply at interface → Frame 9: Gentle shaking initiates → Frame 10: Color disperses upward continuously; final state is homogeneous reddish-brown. All events occur from fixed frontal viewpoint; tube remains fully in frame; no occlusion of interface or reaction zone; lighting remains constant to ensure visibility of color progression.

Manual:
Experimental Procedure
1. Place a clean, dry test tube upright on bench.
2. Transfer erythromycin reagent solution into the tube (~1 mL).
3. Using a pipette, slowly dispense concentrated sulfuric acid along the inner wall of the tube.
4. Keep tube upright; gently shake to mix.
Observation of Experimental Phenomena
A reddish-brown or cherry-red color develops first at the acid–aqueous interface, then disperses upward during shaking to yield a uniform reddish-brown solution. No precipitate or gas forms.
Summary of Experimental Principles
Erythromycin undergoes dehydration and rearrangement in concentrated H₂SO₄, forming chromophoric compounds that absorb visible light in the red-orange region — basis of the sulfuric acid colorimetric identification method.

Prompt Grounding rubric:
level_1: No test tube present; no erythromycin reagent solution visible; no concentrated sulfuric acid container or pipette shown; no upright tube posture; no shaking action; no observable reaction zone.
level_2: Test tube is present and upright, but no liquid is identifiable as the erythromycin reagent solution (e.g., the tube is empty, or a liquid is shown with no source container, label, or addition action linking it to the reagent); concentrated sulfuric acid container or pipette is missing; no acid addition action shown; no mixing or shaking action depicted.
level_3: Test tube is present and upright; a liquid identifiable as the erythromycin reagent solution is present inside the tube, its identity established by context (e.g., poured from a labeled reagent bottle, or dispensed via a marked dropper) even if the liquid itself is colorless; concentrated sulfuric acid container and pipette are present; acid addition action is shown along the inner wall of the tube; shaking action is depicted; but no clear visual separation between layers, or no color develops at the interface.
level_4: All prompt-specified objects are present and correctly typed: test tube, erythromycin reagent solution (identifiable from context even if colorless), concentrated sulfuric acid container, pipette; acid addition occurs along the inner wall while the tube remains upright; gentle shaking is shown; a layered appearance (upper aqueous phase, lower denser acid phase) is visible before shaking.
level_5: All elements in score 4 are present AND the acid addition is delivered exclusively along the inner wall (no splashing, no dripping outside the wall, no direct drop into the bulk liquid); the tube remains upright throughout addition and shaking; the shaking motion shown is gentle and brief (no vigorous swirling or full inversion of the tube); the liquid volume visibly matches what was added, with no unexplained spillage or overflow; no extraneous tools or containers beyond the pipette, acid container, and test tube appear in frame.

Scientific and Causal Correctness rubric:
level_1: The liquid in the test tube keeps its original colorless (or near-colorless) appearance for the entire sequence, with no reddish-brown or cherry-red tint ever appearing at the acid–solution interface or anywhere else; no layering or interface band forms; the reaction shows no visible progression at any point.
level_2: A single uniform color appears (e.g., full-tube pink or yellow) without spatial localization; or color appears instantly upon mixing without interface-specific development; or color contradicts sulfuric acid–erythromycin chemistry (e.g., blue, green, black, or white precipitate).
level_3: A localized color change appears at the interface between the two liquids after acid addition but before shaking; color is reddish-brown or cherry-red (per standard sulfuric acid colorimetric method for erythromycin); color spreads gradually upward during shaking; but color fades, bleeds uncontrollably, or appears in wrong layer (e.g., only in upper aqueous phase before mixing).
level_4: Reddish-brown or cherry-red color appears exclusively at the acid–aqueous interface immediately after acid addition and remains confined to that narrow band before shaking; during gentle shaking, color disperses upward in a continuous, non-fragmented manner; final homogeneous color is reddish-brown (not orange, purple, or brown-black); no precipitation, gas evolution, or phase separation occurs post-shaking.
level_5: All conditions in score 4 are satisfied AND the interface color appears almost immediately upon acid contact, within roughly a second and with no perceptible delay; color dispersion during shaking is strictly upward and radial from the interface (no downward streaking or vortex-driven inversion); the final homogeneous color matches the reference erythromycin–H₂SO₄ standard (reddish-brown, not maroon or rust); no hue shift, desaturation, or brightness flicker occurs during the color's progression.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal rupture: the test tube containing the erythromycin solution vanishes from the frame and reappears at a different point in the sequence with no camera motion to explain it; the liquid volume inside jumps discontinuously between frames; the pipette abruptly jumps from one position to another without continuous movement in between; the overall scene brightness jumps abruptly between consecutive frames without cause; the tube rotates more than 30 degrees with no visible hand or force causing it; the bench background shifts or warps.
level_2: Moderate inconsistency: tube tilts more than about 15° during acid addition or shaking; pipette tip loses contact with the inner wall mid-dispense then recontacts; liquid surface exhibits unnatural rigidity or hyperfluidity (e.g., zero meniscus, instant splash-free impact); shaking motion lacks inertia (instant start/stop, no acceleration/deceleration).
level_3: Minor inconsistencies present: a slight tube wobble (less than about 5°) during shaking that quickly self-corrects; the pipette tip briefly and momentarily loses contact with the inner wall during acid delivery before recontacting it; the liquid meniscus flattens somewhat unrealistically during shaking but recovers its curve; overall scene brightness fluctuates only slightly across the sequence; no structural deformation of the tube or liquid boundaries.
level_4: All motions are physically plausible: the tube stays upright with only a slight wobble during shaking; the pipette maintains contact with the inner wall throughout the acid-delivery action; the acid–solution interface forms cleanly with a natural curved boundary right after the acid is added; shaking produces a smooth, gradually damping motion of the liquid surface without sudden splashing or the liquid separating from the tube wall; the reddish-brown interface color stays clearly visible and undistorted against the glass throughout, never washed out or obscured by any change in the scene's lighting.
level_5: All conditions in score 4 are met AND the tube exhibits realistic rigidity (no bending or flexing); the pipette shows plausible depth and perspective relative to the tube (not a flat, pasted-on overlay); the liquid surface reflects ambient light continuously with a specular highlight that moves naturally as the tube tilts; the shaking motion's amplitude tapers off smoothly and continuously as it settles, rather than dropping in visible jumps; the pipette never appears to pass through or penetrate the tube wall.