Domain: Natural Science — Physics
Target concept: Diffusion of Food Dyes in Thin and Thick Gelatin Layers

Video generation prompt: Place two transparent petri dishes side by side, each containing a thin or thick layer of gelatin, respectively, and then add an equal volume of blue food dye to the center of each, keeping them stationary.

Evaluation guide:
(i) Target concept: Confinement-driven difference in visible surface spread when the same diffusion coefficient acts within gel layers of different depth.
Minimum mechanism: Blue dye molecules move by ordinary diffusion (Brownian motion) through the hydrated gelatin matrix at the same rate in both dishes, since the gel recipe and temperature are identical in each; layer thickness does not change the dye's diffusion coefficient. In the thin gel, the dye reaches the dish bottom quickly and is confined there, so continued diffusion is pushed almost entirely sideways, producing a visibly larger surface patch. In the thick gel, the dye keeps diffusing downward into the gel's depth as well as sideways, so less of it stays near the surface at a given radius, making the visible surface patch look smaller over the same elapsed time, even though the underlying diffusion coefficient is unchanged.
(ii)Storyline: Frame 0–1: Static wide shot showing two transparent petri dishes side-by-side, each containing homogeneous, still, solid gelatin (thin left, thick right), both undisturbed. Frame 2–3: Blue dye appears centered on both gelatin surfaces; no splashing, dripping, or off-center placement. Frame 4–9: Dye remains centered and begins symmetric radial expansion; expansion visibly progresses further in thin gelatin than thick gelatin by final frame; no convection currents, sinking, or surface rupture; viewpoint remains fixed at a slightly elevated three-quarter angle showing both dish rims and gel surfaces at once; lighting uniform; all materials retain physical plausibility (gelatin stays solid, dye stays blue and water-based).

Manual:
Experimental Procedure
1. Place two identical transparent petri dishes side-by-side on flat surface.
2. Fill left dish with thin layer of solidified gelatin; right dish with thick layer of solidified gelatin.
3. Add one drop of blue food dye to exact center of each gelatin surface.
4. Keep setup completely stationary; do not disturb.
Observation of Experimental Phenomena
Blue dye spreads radially from center in both dishes; spread extent is visibly larger in thin gelatin than in thick gelatin after equal time.
Summary of Experimental Principles
The dye's diffusion coefficient in the gelatin matrix is the same in both dishes — layer thickness does not change viscosity or molecular path length. The visible size difference instead comes from confinement: in the thin gel, the dye reaches the dish bottom quickly and is forced to keep spreading sideways, producing a larger surface patch; in the thick gel, the dye also keeps diffusing downward into the gel's depth, leaving less of it near the surface at a given radius, so the surface patch looks smaller for the same elapsed time.

Prompt Grounding rubric:
level_1: Fewer than two petri dishes are shown, or only one dish is visible; or one or both dishes contain no visible gelatin; or blue food dye is missing from one or both dishes; or the dye drop sits away from the center of the gelatin surface in either dish; or the two dishes are not positioned side by side on the same tabletop.
level_2: Two petri dishes sit side by side, but at least one dish shows no gelatin layer, or the blue dye drop is off-center in at least one dish, or dye appears in only one dish, or one dish is opaque or frosted rather than transparent, so the two dishes cannot be visually compared.
level_3: Two transparent petri dishes rest side by side on the tabletop; each holds a visible layer of solidified gelatin; a single drop of blue food dye sits at the center of each gelatin surface; no additional liquids, dyes, droppers, or utensils remain in frame; the arrangement matches the posted prompt (two dishes, gelatin, centered dye, stationary setup).
level_4: Everything at score 3 holds, plus: the two gelatin layers are clearly distinguishable by depth (the left dish's gel sits noticeably lower/thinner against the dish wall than the right dish's gel) under matching, even lighting on both dishes; no hands, droppers, rulers, or other tools remain visible during the observation period.
level_5: Everything at score 4 holds, plus: both dishes and their gelatin surfaces stay completely still with no jostling or repositioning; each dye drop remains a small, tight, undisturbed spot at the exact center of its gel surface in the opening frames, with no premature spreading before diffusion begins; the camera holds one fixed, slightly elevated three-quarter viewpoint throughout, keeping both dish rims (showing the thickness difference) and both gel surfaces (showing the dye spot) simultaneously in frame, uncropped and unoccluded.

Scientific and Causal Correctness rubric:
level_1: No radial spreading of the blue dye is visible in either dish; or the dye spreads to the same visible extent in both the thin and thick gelatin; or the dye in the thick (right) gelatin spreads further than the dye in the thin (left) gelatin; or the blue color fades, turns green/purple, or bleeds into the dish wall; or the gelatin visibly liquefies or collapses.
level_2: The dye spreads outward from center in at least one dish, but by the end of the clip there is no clear visible difference in spread radius between the thin and thick gelatin; or spreading is visible in only one dish; or the dye front breaks into disconnected blobs rather than an unbroken radial spread; or one gel layer appears to soften or liquefy while the other stays firm.
level_3: The dye spreads outward as a roughly circular patch from the center in both dishes; by the end of the clip, the visible dye patch in the thin (left) gelatin is clearly larger in radius than the visible patch in the thick (right) gelatin; both gel layers stay solid, clear, and intact with no dissolving or color bleed into the dish walls.
level_4: Everything at score 3 holds, plus: the dye patch in the thin gelatin grows as a smooth, evenly rounded spot with no ragged or streaky edges; the dye patch in the thick gelatin visibly lags behind (smaller radius and slower outward growth) with a visible gap between the two patches' edges at matching timestamps; neither dish shows ring-like pooling, edge crawling, or dye collecting at the dish wall.
level_5: Everything at score 4 holds, plus: both dye patches keep a clean, roughly circular outline from start to finish with no merging, streaking, or reversal (patch shrinking back); the size gap between the thin-gel patch (larger) and thick-gel patch (smaller) grows or holds steady across the clip rather than closing; growth in both dishes looks continuous frame to frame, without stalling, jumping in size, or momentarily shrinking.

Spatiotemporal Consistency rubric:
level_1: The petri dishes jump to a different position or vanish and reappear between frames; or a dish's orientation suddenly changes; or the lighting suddenly flashes, flickers, or the cast shadows jump to a new direction from one frame to the next; or a gelatin layer appears or disappears mid-clip; or a dye spot appears or vanishes instantly rather than growing; or the camera suddenly rotates, zooms, or pans.
level_2: The two dishes stay generally in place side by side, but one dish visibly warps, ripples, or distorts in shape; or the gel surface's highlight or reflection pattern changes inconsistently between frames; or a dye patch's outline jumps or jitters noticeably more than the smooth growth expected from diffusion.
level_3: Both dishes keep the same fixed side-by-side layout and orientation throughout; the gelatin surfaces keep a consistent texture and clarity; each dye patch grows outward from a stable center point with no sideways drift; overhead lighting keeps the same brightness and angle across the clip; no dish, gel, or dye shows stretching, tearing, or overlapping into the other dish's space.
level_4: Everything at score 3 holds, plus: the clip shows no repeated or skipped frames and no strobing; both dishes stay in equally sharp focus at the same apparent distance from the camera (neither dish appears to shift depth relative to the other); the rim of each dish and the edge of each gel layer line up consistently frame to frame with no visible misalignment.
level_5: Everything at score 4 holds, plus: the growth of each dye patch and the stillness of each dish stay coherent across the entire clip, with no blur inconsistent with the dishes being stationary, no sudden shift in how sharply the surfaces render, and no shimmering or flicker at the boundary between the spreading dye and the surrounding gel.