Domain: Natural Science — Chemistry
Target concept: Peroxidase–guaiacol reaction, initial rapid browning followed by a slowdown

Video generation prompt: A transparent glass cuvette containing guaiacol and hydrogen peroxide was prepared. Horseradish peroxidase was added using a pipette, followed by gentle shaking of the cuvette. The reaction was recorded by side-view photography.

Evaluation guide:
(i) Target concept: Enzyme-catalyzed oxidation producing a visible brown polymer in solution.
Minimum mechanism: Guaiacol must be present as substrate, H₂O₂ as oxidant, and horseradish peroxidase as catalyst; reaction must occur in aqueous phase inside transparent container; browning requires co-location of all three components and cannot precede enzyme addition.
(ii)Storyline: Frame 0–1: Static side-view of cuvette with colorless liquid. Frame 2–3: Pipette enters view and dispenses enzyme into liquid. Frame 4: First visible brown tint appears at liquid surface/mixing zone. Frame 5–6: Brown intensifies rapidly across entire visible liquid volume. Frame 7–9: Brown continues deepening, but rate visibly decreases — no new regions darken, existing brown only subtly intensifies. Throughout: fixed side-view perspective, no occlusion, no object teleportation, no lighting disruption.

Manual:
Experimental Procedure
1. Place transparent glass cuvette containing colorless guaiacol + hydrogen peroxide solution on stable surface.
2. Using a pipette, add horseradish peroxidase solution into cuvette.
3. Gently shake cuvette side-to-side for ~1 second.
Observation of Experimental Phenomena
Liquid rapidly turns brown within first second after enzyme addition, then brown intensity increases more slowly thereafter.
Summary of Experimental Principles
Horseradish peroxidase catalyzes oxidation of guaiacol by hydrogen peroxide, producing tetraguaiacol — a brown polymer. Initial rapid browning reflects fast enzymatic turnover; slowdown occurs as substrate depletes or product inhibits.

Prompt Grounding rubric:
level_1: No transparent cuvette is shown; no guaiacol/hydrogen peroxide liquid is visible inside any container; horseradish peroxidase is never dispensed by a pipette; no shaking of the cuvette occurs; the camera is not held in a fixed side-on view.
level_2: A transparent container appears but is not a cuvette (e.g., a beaker, vial, or plastic tube); guaiacol or hydrogen peroxide liquid is present but the pipette either never reaches the container or never releases enzyme into it; shaking, if shown, is applied to the wrong object or is absent; the camera view drifts away from a side-on angle at some point.
level_3: A transparent cuvette holding the colorless guaiacol + hydrogen peroxide mixture is shown before enzyme addition; a pipette is brought to the cuvette and releases horseradish peroxidase solution into it; the cuvette is then gently shaken; the camera keeps a side-on view of the cuvette from the first frame to the last.
level_4: Everything required for score 3 is present, and additionally: the pipette tip is visibly positioned at or just inside the cuvette mouth while dispensing; the shaking is applied to the cuvette itself, not just implied by an off-screen hand; the liquid level stays below the rim with no spill; nothing (fingers, gloves, labels) blocks the view of the cuvette body; the frame shows the full height of the cuvette including the liquid surface.
level_5: Everything required for score 4 is present, and additionally: the enzyme enters as one continuous drop or short stream that lands on the liquid surface without splashing over the rim; the shaking is brief and controlled, producing visible liquid movement but no foam or overflow; the cuvette sits back on the surface before and after shaking without sliding; the side-on framing never pans, tilts, or zooms during the whole sequence.

Scientific and Causal Correctness rubric:
level_1: The liquid never changes color; it stays colorless (or whatever tint it started as) for the entire clip, with no fast-then-slow browning pattern at all.
level_2: A color change happens, but it's the wrong color (blue, purple, green, or black instead of brown), or the whole liquid darkens instantly and uniformly with no fast initial phase, or a brown tint is already visible before the enzyme is added.
level_3: Brown color appears only once horseradish peroxidase has been added; it develops quickly within the first 2-3 seconds after mixing, then the rate of darkening visibly slows in the later part of the clip, matching a fast-then-slow browning pattern.
level_4: Everything in score 3 holds, and additionally: the brown color stays confined to the liquid itself (the cuvette walls and the meniscus edge do not stain); the color only ever gets darker, never fades or flickers back toward its original hue; there are no odd brown streaks, bubbles, or floating specks that don't belong to a normal browning reaction; the brown tone looks the same across the width of the liquid.
level_5: Everything in score 4 holds, and additionally: the first hint of brown appears right where the enzyme meets the guaiacol/hydrogen-peroxide mixture; within the next few seconds of gentle shaking the color evens out so that the top, middle, and bottom of the liquid column all read as the same shade of brown for the rest of the clip; no ring, streak, or blotch of unmixed color persists once shaking stops; the pipette tip, the outside of the cuvette, and the background keep their original colors, with no brown tint leaking onto them from reflections or lighting.

Spatiotemporal Consistency rubric:
level_1: The cuvette's position or the liquid's surface level changes with no motion connecting one frame to the next; the pipette is present one moment and simply isn't there the next, with nothing carrying it away; the shaking starts or stops on a hard cut with no easing in or out; the lighting flips abruptly from one frame to the next.
level_2: The cuvette shifts position or rotates more than about 15 degrees for no reason; the liquid surface wobbles in a way that looks rubbery rather than liquid; the pipette's path skips between positions instead of moving smoothly; the shaking changes direction or pauses partway through a cycle; shadows detach from the objects casting them or flicker on and off.
level_3: The cuvette stays in the same spot and orientation throughout; the liquid surface moves smoothly while being shaken and settles back down afterward; the pipette travels in one continuous path as it approaches, dispenses, and pulls away; the shaking keeps a steady rhythm and amplitude once it starts; the direction and brightness of the light on the cuvette look the same from the first frame to the last.
level_4: Everything in score 3 holds, and additionally: there is never a second cuvette or a second pipette appearing alongside the real one; the cuvette walls and liquid surface keep their expected straight/curved shapes rather than bending or bulging unnaturally; there are no sudden jumps in overall brightness or contrast; the pipette's approach and the shaking both speed up and slow down naturally rather than moving at a constant robotic speed.
level_5: Everything in score 4 holds, and additionally: the ripples on the liquid surface during shaking look proportional to how hard the cuvette is being shaken, rather than static or wildly exaggerated; the pipette keeps a consistent shape and size as it moves, without visibly stretching or warping; the whole sequence plays as one continuous, fluid motion with no visible freezing, stutter, or skipped moments.