Domain: Natural Science — Biochemistry & Molecular Biology
Target concept: The iodine solution reacts with starch in bread or potato slices.

Video generation prompt: Place a slice of raw potato and a slice of fresh apple side by side on a dish, and add iodine solution to the surfaces of both using a pipette.

Evaluation guide:
(i) Target concept: Iodine-starch reaction as a biochemical indicator for amylose presence.
Minimum mechanism: Amylose must be present in sufficient quantity and accessible in hydrated plant tissue; iodine must be in aqueous solution (I₂/KI); reaction requires direct molecular contact and occurs within seconds at room temperature; apple parenchyma contains negligible amylose but may contain other polyphenols that cause non-blue-black browning.
(ii)Storyline: [Frame 0–2] Static wide shot: empty dish enters view → potato slice placed left → apple slice placed right, both stationary and adjacent. [Frame 3–5] Pipette enters from top, descends smoothly to hover over potato surface → single droplet dispensed → immediate localized blue-black appearance. [Frame 6–8] Pipette retracts, moves laterally, hovers over apple surface → second droplet dispensed → no blue-black develops (only amber-brown wetting). [Frame 9–10] Final static frame: two slices held in fixed side-by-side position, showing contrasting color outcomes under stable lighting; no motion, no occlusion, full visibility of both reaction zones.

Manual:
Experimental Procedure
1. Place one raw potato slice and one fresh apple slice side-by-side on a shallow dish.
2. Using a pipette, apply iodine solution separately onto the exposed surface of each slice.
Observation of Experimental Phenomena
The potato slice turns blue-black where iodine contacts it; the apple slice does not turn blue-black (may show light brown/yellow stain but no blue-black).
Summary of Experimental Principles
Iodine forms a blue-black complex with amylose, a polysaccharide abundant in potato starch but absent or minimal in apple tissue.

Prompt Grounding rubric:
level_1: The video is missing the raw potato slice or the apple slice (or both); it shows only one of the two produce items; it never shows iodine solution being applied; there is no dish or shallow container holding the slices; the slices are not resting on a flat surface; or the iodine is applied without any pipette (e.g., poured straight from a bottle).
level_2: Both the potato slice and the apple slice appear on a surface, but they are not placed next to each other: for example one sits on top of the other, they overlap, or a wide gap or other object sits between them; or the iodine is applied with a dropper, brush, spray bottle, or squeeze bottle rather than a pipette; or no dish or shallow plate is shown holding the slices.
level_3: The potato slice and apple slice sit next to each other on a visible shallow dish; a pipette is used to apply iodine solution to the exposed surface of both slices; the potato, apple, dish, pipette, and iodine liquid or bottle are all clearly identifiable; neither slice is mistaken for a different produce item (no sweet potato standing in for the potato, no pear standing in for the apple).
level_4: Everything required for score 3 is shown, and in addition: the potato and apple slices stay in the same left/right arrangement they were placed in, without sliding, rotating, or being repositioned afterward; the pipette tip is shown at or just above the surface of each slice as it dispenses, not hovering over the dish rim or empty air; the iodine appears as a visible bead or wet droplet sitting on each slice's surface rather than as a pre-existing stain or a droplet that has already soaked in before the camera shows it landing.
level_5: Everything required for score 4 is shown, and in addition: both slices stay completely still for the entire clip, with no blur, tremor, or drift in their outlines; the pipette delivers iodine in two separate, clearly targeted actions (first onto the potato, then onto the apple), with no iodine visible on either slice before its own turn; the dish's background stays plain and uncluttered, so it is always obvious which slice is the potato and which is the apple.

Scientific and Causal Correctness rubric:
level_1: Neither the potato slice nor the apple slice changes color after the iodine touches them; or both slices react the same way as each other (for example both turn blue-black, or both stay unchanged); or the color change happens only on the dish or the pipette rather than on either slice; or the apple slice turns blue-black, which is chemically wrong for a fruit with negligible starch.
level_2: Only one of the two slices changes color, but the resulting color is wrong for that slice: for instance the potato turns brown, green, yellow, or purple instead of blue-black where the iodine landed; or the apple slice develops a blue-black patch; or both slices end up looking the same shade with no visible difference between them.
level_3: Where the iodine touches the potato, that spot turns blue-black; where it touches the apple, no blue-black appears: the apple keeps its original pale yellow or tan color, at most gaining a faint amber-brown wash; the color change on the potato stays confined to where the droplet landed; once formed, the blue-black patch does not fade or vanish again before the clip ends.
level_4: Everything required for score 3 holds, and in addition: the blue-black color spreads through the potato's starchy flesh itself, not just sitting on the skin or the cut edge; the apple shows no trace of blue-black anywhere: any tint on it stays a light amber or translucent brown; the two slices end up clearly different colors at the same time, so a viewer can immediately tell which one contains starch.
level_5: Everything required for score 4 holds, and in addition: the blue-black patch on the potato looks solid and even everywhere the iodine soaked in, rather than speckled or patchy; the apple slice shows no blue-black flecks anywhere on its surface at normal viewing distance; the two color outcomes stay separate and do not bleed or merge into each other across the boundary between the slices; no stray blue-black tint shows up on the apple's peel or along any vein-like line in either slice.

Spatiotemporal Consistency rubric:
level_1: The potato or apple slice vanishes from the dish and reappears in a different spot without the pipette or a hand placing it there; the shallow dish itself changes shape, disappears, or is swapped for another mid-clip; the whole scene jumps from bright to dark lighting with no fade or transition; the pipette snaps from above the potato straight to above the apple with no visible path connecting the two positions.
level_2: The potato and apple slices swap their left/right positions between frames without any hand or tool moving them; the pipette tip disappears mid-dispense and reappears already withdrawn; one slice changes size relative to the dish partway through the clip even though the camera never zooms; an iodine droplet is already sitting on a slice before the pipette has moved into position above it.
level_3: The potato stays on its side of the dish and the apple stays on its side for the whole clip, in the same orientation they started in; the pipette's descent toward each slice follows a smooth, continuous path rather than snapping between positions; the room's light source stays in the same place, so the blue-black patch on the potato and the untouched surface of the apple are lit from the same direction in the last frame as in the first; neither slice, the dish, nor the pipette flickers, warps, or turns see-through at any point.
level_4: Everything required for score 3 holds, and in addition: the hand or mechanism moving the pipette slows down naturally as the tip nears each slice's surface rather than stopping abruptly; no frame repeats or skips ahead in a way that makes a droplet seem to jump into place; the pipette is never shown appearing to pass through the dish's rim in a way that makes part of it vanish when it should still be visible above the rim; the dish and its background stay fixed and unchanging behind the two slices.
level_5: Everything required for score 4 holds, and in addition: the potato and apple slice outlines stay steady from frame to frame, without visibly wobbling or trembling; the iodine droplets look like smooth liquid beads rather than flickering or sparkling as they sit on the slices; the dish and the two slices stay at a constant distance from each other, with no sense that the background has shifted relative to the foreground; an iodine droplet never appears on a slice before the pipette has visibly begun moving down toward it; every object moves the way a solid potato slice, apple slice, dish, and pipette actually would, with nothing stretching, floating, or bending unnaturally.