Domain: Natural Science — Chemistry
Target concept: Distribution of iodine solution between the oil and aqueous phases after shaking

Video generation prompt: A glass vial containing oil above water; when the brown iodine solution is added, the cap is sealed, and the mixture is shaken and left to stand, the layers gradually separate.

Evaluation guide:
(i) Target concept: Iodine is nonpolar and preferentially partitions into the nonpolar oil phase over the polar aqueous phase. Minimum mechanism: Immiscibility of oil and water must be preserved; iodine must be soluble in oil but nearly insoluble in water; shaking must enable molecular contact and redistribution; gravity-driven phase separation must dominate over diffusion or emulsification. (ii)Storyline: Frame 0–2: Static vial showing oil-on-water stratification + sealed cap. Frame 3–4: Brown iodine solution enters vial (single continuous stream, no splatter). Frame 5–6: Cap secured; vial begins shaking; interior liquid shows turbulent mixing, temporary homogenization of brown color. Frame 7–9: Shaking stops; liquid oscillates with damped motion; interface blurs then progressively sharpens. Frame 10 onward: Two distinct horizontal layers fully reformed; brown concentrated exclusively in upper oil layer; aqueous layer fully colorless and transparent; viewpoint remains fixed frontal, full-vial framing throughout; no occlusion of vial body, cap, or interface region.

Manual:
1. Place clear glass vial with oil layer visibly floating atop colorless aqueous layer. 2. Add brown iodine solution into vial, seal cap tightly. 3. Shake vial vigorously for ~1 second (visible interior agitation), then hold still. 4. Observe gradual reseparation: oil layer rises, aqueous layer sinks, brown color concentrates in oil. 5. After standing, two sharp horizontal layers reappear — upper oil layer brown, lower aqueous layer colorless.

Prompt Grounding rubric:
level_1: No glass vial visible; no oil-over-water layering shown before iodine is added; no addition of the brown iodine solution shown; no shaking action shown; no standing/settling phase shown.
level_2: A glass vial appears with two immiscible layers, but oil and water are not in the correct starting order (e.g., water sits on top); the iodine solution is added without appearing brown; a shaking action is only implied (e.g., an off-screen hand) with no visible motion of the liquid; or the standing/settling phase is missing entirely.
level_3: The vial shows oil clearly on top of the aqueous layer before the iodine solution is added; the brown iodine solution goes into the vial; the vial is visibly shaken (the liquid inside is agitated, the meniscus is disturbed); after shaking stops, the vial is held still and at least one frame shows the two layers beginning to reform.
level_4: All conditions for score 3 are met, and additionally: the oil layer stays on top of the water layer for the entire video with no inversion; the cap is visibly on the vial and sealed before shaking begins and remains on through the standing phase.
level_5: All conditions for score 4 are met, and additionally: the cap stays fully visible on the vial for the whole video with no removal or occlusion; the oil layer stays a continuous horizontal band above the aqueous layer in every pre-shake, shaking, and post-shake frame; the iodine solution is added only once, as a single pour or stream, with no second addition or stray droplet appearing later in the video.

Scientific and Causal Correctness rubric:
level_1: The iodine color stays evenly brown across both layers after standing (no partitioning); or the coloring goes to the wrong layer (oil stays colorless, water turns brown); or the two layers never separate at all; or water ends up on top of the oil after standing.
level_2: The color shifts, but violates how iodine actually partitions: the aqueous layer ends up visibly darker than the oil layer, or both layers keep the same brown intensity after separation, or the oil layer seems to vanish or dissolve into the water.
level_3: After shaking and settling, the brown color concentrates mostly in the oil layer, and the aqueous layer is noticeably lighter than the oil layer; the two layers stay immiscible and stacked horizontally; the coloring is never inverted (the oil layer is never colorless while the water layer looks brown).
level_4: All conditions for score 3 are met, and additionally: in every frame after separation where both layers are visible together, the oil layer is distinctly darker/more colored than the aqueous layer; no brown streaks or suspended droplets bridge the interface; the aqueous layer looks clear again once separation is complete; the brown color first appears spread uniformly through the mixture during shaking, and only concentrates into the oil layer as the layers reform, showing the redistribution actually happening rather than being present from the start.
level_5: All conditions for score 4 are met, and additionally: the aqueous layer ends up essentially colorless in the final resting state; the oil layer's brown looks even throughout, without patches or a fading edge near the interface; no brown is visible in the oil before the iodine solution is added, and no color diffuses back across the interface once separation is complete; the contrast between the two layers' colors is clearly and stably visible.

Spatiotemporal Consistency rubric:
level_1: The vial vanishes and reappears; the layers flip order or shear apart with no visible motion causing it; the lighting jumps abruptly between one frame and the next with no source change shown; the cap disappears mid-shake; the vial visibly tips more than about 15 degrees from upright.
level_2: The vial stays in place, but the liquid inside shows jarring motion breaks: swirling that stops dead and restarts; the interface between layers wobbles violently with no settling; the cap is partly hidden and then suddenly fully visible with no gradual reveal; background objects flicker or warp.
level_3: The vial stays upright and stationary throughout; the liquid inside shows coherent swirling and bubbling while being shaken; once shaking stops, the liquid settles with visibly decreasing motion rather than stopping instantly; the interface between the layers reforms smoothly, without jumping or fracturing; the cap stays fully visible and still on top of the vial.
level_4: All conditions for score 3 are met, and additionally: the shaking motion itself looks continuous, with no frozen frames or motion blur heavy enough to make the layers indistinguishable; the settling motion keeps calming down rather than surging back up partway through; the vial doesn't appear to shift relative to the background; the reflection or bright spot on the vial's glass stays consistent with the liquid's own motion rather than jumping to a new position for no reason.
level_5: All conditions for score 4 are met, and additionally: the vial does not visibly drift or shift position at any point in the video; the liquid's slowing motion looks physically natural, with no instant stop and no sudden reversal; the interface settles into its final sharp line at a steady pace rather than stalling and then jumping; the cap stays aligned with the vial's opening throughout; the vial's overall brightness doesn't flicker in a way that makes the layers hard to distinguish.