Domain: Engineering — Food and Bioprocess Engineering
Target concept: The color change of iodine gradually disappears as amylase digests starch.

Video generation prompt: Two identical potato slices were placed in transparent containers and treated with iodine solution; amylase was added to the potato slice on the right, and water was added to the potato slice on the left, followed by observation over time.

Evaluation guide:
(i) Target concept: Enzymatic hydrolysis of starch by amylase abolishes iodine-starch complex formation, causing selective decolorization. Minimum mechanism: Starch must be present and accessible in potato tissue; iodine must form initial complex; amylase must be active and in contact; water alone must not degrade starch or complex.
(ii)Storyline: Frame 0–1: Two raw potato slices placed adjacently in identical transparent containers. Frame 2–3: Iodine solution applied to both slices → immediate uniform blue-black coloration. Frame 4–5: Water dispensed into left container; amylase dispensed into right container (visually distinct delivery). Frame 6–10: Right slice shows progressive, global reduction in blue-black saturation; left slice maintains full, stable blue-black color; viewpoint remains fixed, lighting constant, no occlusion of slice surfaces during observation phase.

Manual:
Experimental Procedure
1. Place two identical raw potato slices side-by-side in separate transparent containers.
2. Apply iodine solution evenly to both slices — both turn blue-black immediately.
3. Add water to left container; add amylase solution to right container.
4. Observe color change over time.
Observation of Experimental Phenomena
The right (amylase-treated) potato slice gradually loses its blue-black iodine color; the left (water-treated) slice retains its blue-black color unchanged.
Summary of Experimental Principles
Amylase hydrolyzes starch into maltose and glucose; iodine forms a blue-black complex only with intact starch helices — digestion breaks the helix, abolishing the color reaction.

Prompt Grounding rubric:
level_1: None of the required objects or actions appear: no potato slices, no transparent containers, no iodine application, no addition of water or amylase, and no side-by-side layout that lets the two slices be told apart. The setup described in the prompt is not established at all.
level_2: At least one potato slice appears in a container, but something essential is missing: the second slice, the two containers placed next to each other, iodine applied to both slices, or any visible difference between the water-treated and amylase-treated sides.
level_3: Two potato slices sit next to each other in transparent containers; iodine solution is applied to both, and both slices turn blue-black; water is added to the left container and amylase solution to the right, with the two additions visually distinguishable, for example through separate droppers or being dispensed one at a time, matching the setup in the prompt.
level_4: All of 3, plus the water and amylase are delivered through clearly separate actions or droppers, both containers stay in frame with a steady viewpoint, neither addition is hidden from view, and the two containers look like a matched pair in shape, size, and transparency.
level_5: All of 4, plus water is added to the left slice before amylase is added to the right, with no overlap between the two additions; both slices stay fully visible and unobscured during each addition; the amylase solution is distinguishable from water in some consistent way, such as a faint tint or a clearly separate reagent container; and the two containers sit at the same distance from the camera under matching lighting.

Scientific and Causal Correctness rubric:
level_1: No color change occurs in either container: both slices show identical color throughout, or both lose or keep their color in the same way. The clip gives no evidence that amylase is breaking down starch.
level_2: Color change happens, but the causal direction is wrong: the water-treated left slice loses color faster than the amylase-treated right slice, the right slice's color gets darker instead of fading, the color starts fading before amylase is actually added, or both slices fade identically with no difference between them.
level_3: The amylase-treated right slice shows its blue-black iodine color progressively fading over time; the water-treated left slice keeps its blue-black color steady throughout; the fading on the right is gradual and does not reverse or flicker back once it begins.
level_4: All of 3, plus the fading on the right slice only begins after amylase has actually been delivered, not during the pour itself; the left slice shows no fading at all, its blue-black color staying uniformly saturated; and nothing else on the left, such as a passing shadow or reflection, is mistaken for color loss.
level_5: All of 4, plus the right slice only loses saturation of its blue-black color, with no shift toward another hue such as green or yellow, no bubbling or visible breakdown of the potato tissue's surface, and no strong edge-versus-center bias in how the fading spreads; the left slice's blue-black color stays essentially unchanged in hue and pattern from the first frame to the last.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal rupture: a potato slice's position in its container, or a container's position on the bench, changes abruptly between frames with no hand or motion shown; a container's angle snaps to a new orientation between one frame and the next; or the blue-black color on the right slice switches directly from fully saturated to fully clear with no gradual fading shown in between.
level_2: Moderate breaks appear: one container tilts or rotates more than 15° with no visible cause, a slice appears to compress or stretch, the iodine application shows inconsistent liquid amounts between the two containers, or one container or slice is hidden from view for a long stretch of the clip.
level_3: Both containers and slices stay in consistent, fixed positions throughout; neither slice changes shape, size, or rotates unexpectedly; and the sequence of actions, placing the slices, applying iodine, adding water or amylase, and observing, plays out as smooth, physically plausible motion rather than jumps or freezes.
level_4: All of 3, plus each dropper stays close to its container's opening while dispensing, without jerking or hovering away, the liquid stream from each dropper is continuous rather than broken into disconnected drops, and the containers' and slices' outlines stay steady and aligned across the clip rather than visibly drifting.
level_5: All of 4, plus no motion blur hides the dropper tip or the slices' surface texture during delivery, the containers' walls show consistent, undistorted refraction of what's behind them, and the left, water-treated container does not darken or change apparent brightness on its own. Any such shift would misleadingly look like the amylase-driven fading and must not occur.