Domain: Natural Science — Marine Science
Target concept: Physical Ocean Thermocline and Density Stratification

Video generation prompt: In a transparent tank, the upper layer is dyed warm water and the lower layer is clear cold water. The intermediate partition is removed, and the process of stratification and mixing of the water body is recorded.

Evaluation guide:
(i) Target concept: Density-stratified fluid interface governed by thermal buoyancy, where warmer (less dense) fluid overlies colder (more dense) fluid, producing a stable, horizontal, diffusion-limited boundary (thermocline analog).
Minimum mechanism: Dyed warm water must be *less dense* than underlying cold water; therefore, it must remain buoyant and resist downward penetration; any vertical intrusion would violate density stratification physics.
(ii)Storyline: [Phase 1: Setup] Tank fully visible, partition in place, dyed layer fully confined above, clear layer fully confined below; both static and horizontally aligned. [Phase 2: Trigger] Partition is physically removed (not dissolved/faded) with continuous motion, leaving unobstructed vertical column. [Phase 3: Response] Interface remains intact and planar for observable duration; only molecular diffusion causes gradual, narrow-band blurring at boundary; no turbulent eddies, no plumes, no overturning. [Perspective constraint] Fixed frontal view showing full tank height; no occlusion of interface region; lighting enables unambiguous discrimination of dye presence/absence and layer continuity.

Manual:
Experimental Procedure
1. Fill transparent tank with cold clear water to ~50% height.
2. Gently overlay warm water dyed with food coloring on top using a pipette or tilted plate.
3. Insert vertical partition to separate layers completely.
4. Remove partition smoothly and observe.
Observation of Experimental Phenomena
Before removal: two sharply separated horizontal layers — colored upper, clear lower.
After removal: layers remain largely stratified; interface stays flat; slow mixing only at boundary; no bulk overturning.
Summary of Experimental Principles
Warm water is less dense than cold water → forms stable upper layer. Density difference resists mixing → creates thermocline-like interface. Removal of barrier allows diffusion-dominated equilibration, not convection.

Prompt Grounding rubric:
level_1: No transparent tank is shown; no partition is visible; no dyed (warm) water layer is shown; no clear (cold) water layer is shown; no removal action is depicted; or there is no before/after moment showing the partition being taken out.
level_2: A transparent tank is shown, but the partition is either never shown or never removed (it is absent from the very first frame); or only one water layer (dyed or clear, not both) is visible; or a removal action is implied without ever showing the tank in both a with-partition and a without-partition state.
level_3: The transparent tank clearly shows a partition separating an upper dyed (colored) layer from a lower clear layer; the partition is then visibly taken out (e.g., slid up, lifted out, or pulled away); and both layers are visible both before and immediately after this removal action.
level_4: In addition to the 3-point requirements, the dyed layer stays entirely in the upper half and the clear layer stays entirely in the lower half for the whole time before the partition is removed, with no mixing, color bleeding, or diffusion happening before the removal action starts.
level_5: In addition to the 4-point requirements, the partition-removal action itself is shown clearly and without ambiguity (the barrier is fully pulled out of frame or cleanly withdrawn without being blocked from view), and no visual glitch (smearing, sudden blending, or a jump in the water's opacity) appears at the exact moment the partition leaves the tank.

Scientific and Causal Correctness rubric:
level_1: No density-driven behavior is visible: the dyed warm layer and the clear cold layer mix together as soon as the partition is removed, or the color spreads equally upward and downward with no bias toward staying on top.
level_2: The dyed (warm) layer visibly sinks into the clear (cold) layer, or the clear layer visibly rises up into the dyed layer; or the mixing spreads with no preference for one direction; or the dyed layer already looks partly mixed with the clear layer before the partition is even removed.
level_3: After the partition is removed, the dyed water stays mostly in the upper part of the tank and the clear water stays mostly in the lower part; only the region right at the boundary between them shows some blending; there is no wholesale sinking of the dyed water or wholesale rising of the clear water.
level_4: In addition to the 3-point requirements, the boundary between the dyed and clear water stays roughly horizontal and unbroken during the early part of the mixing, with no finger-like streaks or blobs of dyed water dropping down through the clear layer (or vice versa).
level_5: In addition to the 4-point requirements, the boundary between the two layers stays flat and unbroken for a sustained stretch of the video with no visible waviness, breaking apart, or spike-and-blob patterns forming at the interface; and the dye never travels noticeably above or below where the original boundary line was.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal rupture: the tank disappears and reappears; the water layers jump to a different arrangement between frames; the partition vanishes with no visible motion of it being removed; the lighting jumps suddenly; the camera view jumps or zooms abruptly; or a frozen or dropped frame breaks the sense of continuous action.
level_2: A noticeable but less severe break: a brief flash or flicker happens right as the partition is removed; the tank's position jitters slightly; motion blur briefly hides both layers at once so their boundary can't be seen for a moment; or a shadow on the tank appears in a different place from one frame to the next with no clear cause.
level_3: The tank stays in the same place in the frame throughout; the partition's removal looks like one continuous motion with no jump cuts; the dyed and clear layers keep the same relative vertical arrangement before and during their interaction; the lighting stays the same color and brightness across the video; and the tank or water shows no warping or distorted perspective.
level_4: In addition to the 3-point requirements, the camera viewpoint never pans, tilts, zooms, or moves; the tank's edges and the boundary between the two layers don't shift sideways relative to each other from frame to frame; and neither the partition nor the two layers show any doubled or ghosted outline.
level_5: In addition to the 4-point requirements, there is no visible misalignment or drift of the tank walls or the layer boundary across frames; the motion of the interface and the dye shows no strobing or skipped-looking motion; and there is no visible shaking or trembling of the layer boundary from one frame to the next.