Domain: Natural Science — Chemistry
Target concept: Heller's Protein Test

Video generation prompt: Add concentrated nitric acid to a test tube, then slowly add the protein solution along the wall of the test tube.

Evaluation guide:
(i) Target concept: Acid-layered interfacial denaturation and nitration of aromatic amino acids in proteins, producing localized, textured precipitate.
Minimum mechanism: Protein must remain undisturbed as discrete upper layer long enough for acid to act at interface; nitration requires direct contact between concentrated HNO₃ and aromatic residues; precipitate formation must be kinetically constrained to interface due to pH gradient and limited diffusion.
(ii)Storyline: [Frame 0–2] Static shot: upright test tube containing pale yellow concentrated nitric acid occupying lower third. [Frame 3–5] Protein solution enters frame from top-right, contacting inner wall at top rim and flowing down wall without breaking surface tension. [Frame 6–7] Protein layer settles above acid, forming sharp horizontal interface with visible refraction. [Frame 8] Yellow-orange granular ring appears *exclusively* at interface, with no diffusion or dissolution. [Visibility constraint] Entire sequence viewed from fixed frontal angle; test tube occupies central 60% of frame; interface and ring must be fully in focus and unobscured.

Manual:
Experimental Procedure
1. Place an upright transparent test tube on stand.
2. Add concentrated nitric acid to fill lower ~1/3 of tube.
3. Slowly pour protein solution along inner wall so it forms a distinct layer above acid.
Observation of Experimental Phenomena
A sharp yellow-orange ring forms precisely at the interface between acid and protein layers; ring exhibits granular, curd-like texture and remains localized without spreading.
Summary of Experimental Principles
Heller's test detects proteins through two concurrent effects of the concentrated acid: it denatures the protein by disrupting its native folding, and, independently, concentrated HNO₃ performs electrophilic aromatic substitution (nitration) directly on the benzene ring of aromatic side chains (tyrosine, tryptophan, phenylalanine), producing yellow xanthoproteic nitro-derivatives that precipitate as curds. Denaturation is a separate, concurrent effect of the strong acid, not a precondition that enables the nitration reaction.

Prompt Grounding rubric:
level_1: No test tube, no concentrated nitric acid, and no protein solution appear anywhere in the shot; no pouring or addition action of any liquid into a tube is shown.
level_2: Only one of the three required items (test tube, concentrated nitric acid, or protein solution) is visible, and no addition action occurs; or two items appear but are combined incorrectly (e.g., both liquids poured together into open air rather than into the test tube).
level_3: An upright, transparent test tube, a yellow-tinged pool of concentrated nitric acid, and a colorless-to-milky protein solution are all visible; the nitric acid is shown settled in the tube before the protein solution is introduced, but the protein solution is poured straight into the middle of the acid rather than run down the tube's inner wall.
level_4: The test tube, nitric acid, and protein solution appear in the correct order (acid first, protein second) and the protein solution is poured down the inner wall of the tube, but the point where the protein solution meets the acid does not show a visible, held boundary; the two liquids appear to blend together the instant they touch instead of settling into separate layers first.
level_5: Concentrated nitric acid is shown fully settled in the lower portion of the upright test tube before anything else happens; the protein solution is then added by running down the inner wall without breaking the acid's surface, and it settles into a visibly separate layer sitting on top of the acid, with a clear boundary line between the two liquids before any color change begins.

Scientific and Causal Correctness rubric:
level_1: The solution shows no color change at all: no yellow or orange band ever appears at any point in the clip, and the liquids stay their starting colors (clear acid layer, colorless-to-milky protein layer) throughout.
level_2: A single, uniform color shift happens across the whole tube at once (e.g., the entire liquid column turns yellow all together) rather than a localized ring; or a solid precipitate appears without any preceding boundary or color change at the contact line.
level_3: A yellow-orange band forms at the boundary between the two liquids, but it appears before the protein solution actually reaches the acid, or the band keeps spreading up or down instead of staying at the contact line, or the band looks smooth/uniform rather than showing the grainy, curd-like texture of a protein precipitate.
level_4: The yellow-orange band forms only after the protein solution touches the acid, stays confined to the contact line, and shows a visibly grainy, curd-like texture, but it either fades away within about a second of forming or spreads well beyond the original contact line before the clip ends.
level_5: The yellow-orange, curd-textured band forms exactly at the contact line only after the protein solution reaches the acid, and it stays put (neither fading, dissolving, nor spreading) for the remainder of the clip, with no other color change or precipitate appearing anywhere else in the tube.

Spatiotemporal Consistency rubric:
level_1: The test tube vanishes from the shot or pops into view without ever having been placed there; the liquid level inside jumps from one amount to a different amount between consecutive shots with no addition shown; or the tube's wall shows a visible crack or break that appears out of nowhere.
level_2: The test tube stays on screen but suddenly rotates or tilts by a large, visible angle (roughly 30° or more) during the addition; the liquid surface breaks apart into separate floating blobs instead of behaving as a continuous liquid; the protein stream visibly detaches from the tube wall and drifts away mid-pour instead of clinging to it.
level_3: The test tube stays upright and in the same place throughout; the liquids move continuously with no jump in position; the protein stream mostly clings to the inner wall but briefly separates into a visible droplet for a couple of seconds; the video has a brief, mild change in overall brightness that does not hide the boundary or the ring formation.
level_4: The test tube stays upright and still; every bit of liquid motion looks continuous and physically reasonable; the protein stream clings to the wall the whole way down without detaching; the boundary between the two liquids stays visibly stable, but there is one brief, visible wobble of the tube (well under a second) that momentarily makes the start of the ring hard to see.
level_5: The test tube stays upright and completely still for the whole clip; the protein solution flows down as one continuous stream that clings to the inner wall the entire way, the boundary between the two liquids stays sharp and steady before, during, and after the ring appears, and there is no visible wobble, flicker, or change in lighting anywhere in the sequence.