Domain: Natural Science — Chemistry
Target concept: Paper chromatographic analysis of food dyes on filter paper

Video generation prompt: Place a drop of food dye near the bottom of a vertically suspended chromatography paper strip, and suspend the paper in a container such that only the edge of the paper is in contact with the shallow water, without submerging the dye spots.

Evaluation guide:
(i) Target concept: Capillary-driven solvent migration enabling differential partitioning of dye components based on polarity.
Minimum mechanism: Water must be physically adsorbed into cellulose matrix; dye molecules must be soluble in water; paper must be porous and hydrophilic; dye components must exhibit measurably different partition coefficients between water and cellulose.
(ii)Storyline: Frame 1–2: Static shot showing vertical paper strip, dye drop adjacent to bottom terminus, shallow water container positioned so only paper"s bottom edge contacts liquid; dye spot fully above water. Frame 3–5: Liquid begins ascending as a continuous wet front; dye spot remains intact but lifts upward with front. Frame 6–8: Front advances; dye spot resolves into ≥2 discrete, vertically aligned color bands separating progressively. Frame 9–10: Bands maintain separation and continue upward; solvent front remains leading, smooth, and uninterrupted. Perspective: Fixed frontal close-up, full paper height visible, no occlusion of bottom 2 cm (dye + contact zone) or top 2 cm (front progression).

Manual:
Experimental Procedure
1. Hold a rectangular filter paper strip vertically and suspend it from a support.
2. Place a single drop of mixed food dye near the bottom edge of the paper.
3. Position a shallow container of water so the paper’s bottom edge just touches the water surface — dye spot must remain above water.
Observation of Experimental Phenomena
Water rises up the paper via capillary action; dye separates into distinct colored bands moving at different speeds; solvent front advances steadily ahead of all bands.
Summary of Experimental Principles
Paper chromatography separates dye components by differential affinity for stationary (paper) and mobile (water) phases; polar dyes bind more strongly to cellulose and migrate slower; nonpolar dyes travel faster with solvent.

Prompt Grounding rubric:
level_1: None of the three required objects appear at all: no chromatography paper strip, no colored dye drop, and no container of liquid with the paper touching it.
level_2: Only one of the three required objects is identifiable: either the paper strip is shown but not hanging vertically, or a colored droplet is visible but not placed near the paper's bottom edge, or a liquid container appears but the paper is not touching it; no two of the objects appear together in a sensible arrangement.
level_3: All three objects appear (a vertically hung paper strip, a single dye drop near its bottom edge, and a container with shallow liquid touching the paper's bottom edge), but at least one detail is off: the dye spot is under the liquid surface, the paper leans noticeably more than roughly 15° from vertical, or the drop sits more than about 1 cm above the very bottom of the strip.
level_4: The paper hangs vertically, the dye drop sits right at the bottom edge, the container holds shallow liquid touching only the paper's lowest edge, and the dye spot stays above the liquid line, but the paper visibly sways or drifts during the video, the dye spot spreads out before the liquid ever reaches it, or something in the frame blocks the paper-liquid contact point for a noticeable stretch.
level_5: The paper hangs vertically and stays still, the dye drop sits directly at the bottom edge with no gap or overlap, only the very bottom edge of the paper (not the dye spot) touches the liquid continuously, and the dye spot stays above the liquid surface for the whole video; every object stays fully visible with no tilt, warp, or unexplained repositioning.

Scientific and Causal Correctness rubric:
level_1: No color separation occurs; the dye spot never moves upward from where it was placed; the paper directly above the water shows no wetting; there is no visible solvent front at all.
level_2: The dye spot stays a single unchanged color and position; the paper does not appreciably wet or absorb water above the contact edge; either the dye smears sideways on dry paper without rising, or water visibly climbs the paper but the dye spot never separates into distinct colors, and no solvent front is visible advancing past the spot.
level_3: Water visibly climbs the paper as a continuous wet front from the contact edge upward; the dye spot rises together with the front as a single blob without splitting into separate colors; the front and the dye move upward together with no dripping or backward flow.
level_4: Water climbs the paper AND the dye spot visibly splits into two or more distinguishable color bands that move upward at different rates from the same starting point, with the solvent front staying ahead of all of them and no band merging back together or reversing direction, but either one band fades out before the video ends, the front stops rising before reaching roughly two-thirds of the way up the paper, or two bands briefly overlap before separating again.
level_5: Water climbs the paper and the dye spot resolves into two or more clearly separated, non-overlapping color bands, all starting from the same original spot; the solvent front stays continuously ahead of every band; once a band is faster or slower than its neighbor, that relative order holds for the rest of the video with no crossing or reordering; no band fades, bleeds sideways, or breaks apart; all visible motion is upward only.

Spatiotemporal Consistency rubric:
level_1: The paper strip jumps to a different position or angle between shots; the dye spot vanishes and reappears; the water level in the container changes with no visible cause; the paper visibly bends, kinks, or tears mid-video; or the camera cuts to a different framing of the setup.
level_2: One clear break in continuity occurs: the paper snaps from a bent to a straight shape with no visible motion causing it, the dye spot jumps upward by roughly 1 cm or more with no gradual rise shown, the paper's wet/dry boundary flickers back and forth with no smooth transition, or the camera pans/zooms enough to reframe the dye spot or contact point.
level_3: The paper stays upright and in the same place, and the dye spot and bands keep a consistent shape and position relative to the paper, but a small flaw is visible, such as the paper swaying slightly (less than about 5°) without shifting its base position, the water's meniscus trembling briefly at the contact edge, or the lighting drifting slowly without ever obscuring the dye or front.
level_4: The paper remains stationary and upright with no visible sway or bending; the dye spot and every band keep a steady, consistent shape as they rise; the paper's contact edge stays continuously touching the water; lighting stays even throughout; the only imperfection is something minor and non-core, such as a brief partial obstruction of the dye area by a passing shadow, or a short-lived small bulge in the solvent front that does not affect the bands.
level_5: The paper stays perfectly still and vertically aligned throughout; the dye spot and all resulting bands keep consistent shape, spacing, and position as they rise, with no unexplained jump or flicker; the contact edge between paper and water stays sharp and unbroken; lighting stays constant with no flare, flicker, or obstruction affecting visibility of the dye spot, bands, or solvent front at any point.