Domain: Natural Science — Marine Science
Target concept: Oil spreads on the water surface and covers a feather.

Video generation prompt: In a shallow seawater tray, dark crude oil was poured onto the water surface, with a clean bird feather floating nearby. The water surface was gently disturbed by slow hand movements.

Evaluation guide:
(i) Target concept: Interfacial fluid displacement driven by surface-wave momentum transfer causes a floating oil film to advance across a water surface until it engulfs a floating object in its path, illustrating how surface oil contamination reaches and coats objects such as seabirds' feathers.
Minimum mechanism: Oil must remain a contiguous, non-wetting surface film; water must sustain propagating waves generated by the hand motion rather than by direct hand contact with the oil or feather; the feather must act as a passive, buoyant marker until the oil reaches it; wave-driven advance of the oil film must eventually bring its leading edge into contact with the feather and visibly coat its surface.
(ii) Storyline: [Frame 0–2] Oil poured → forms a static circular patch; feather placed nearby, stationary and clean. [Frame 3–4] Hand enters frame, begins a slow horizontal sweep → ripples initiate at the water surface near the hand. [Frame 5–7] Ripples propagate outward → the oil film deforms and spreads concentrically toward the feather while staying cohesive. [Frame 8–10] The oil film's leading edge reaches the feather, and the feather's surface becomes visibly darkened and coated where the oil touches it; ripples dampen gradually; all other spatial relationships within the tray stay unchanged. Perspective: Fixed overhead or 30° oblique view, level with the water surface; full tray visible; no occlusion; lighting reveals oil iridescence and the contrast between the feather's clean and oil-coated regions.

Manual:
Experimental Procedure
1. Fill a shallow transparent tray with clear seawater to about 2 cm depth.
2. Gently pour dark crude oil onto the center of the water surface.
3. Place a clean white bird feather a few centimeters from the oil patch, floating freely.
4. With a hand held just above the water surface, make slow, horizontal sweeping motions to generate gentle ripples.
Observation of Experimental Phenomena
- The dark oil forms a cohesive, iridescent film that spreads radially across the water surface.
- The feather stays clean and afloat while the ripples reach it, but once the advancing oil film's edge reaches the feather, the feather's surface becomes visibly coated and darkened by the oil.
- Ripples propagate outward from the hand's motion and visibly push the oil film ahead of them until it reaches and engulfs the feather.
Summary of Experimental Principles
- Oil is hydrophobic and less dense than seawater, so it forms a film on the surface rather than mixing in.
- Surface tension and viscosity govern how fast and how continuously the oil spreads.
- Mechanical disturbance from the hand transfers momentum to the water and then to the oil film, driving its lateral displacement until it reaches and coats objects such as the feather — the same mechanism by which oil spills contaminate wildlife at sea.

Prompt Grounding rubric:
level_1: None of the following are visible: the shallow tray, the water surface, the dark oil, the feather, or a hand; none of the posted_prompt's elements appear at all.
level_2: At least one element appears (the tray, water, oil, feather, or a hand), but not in a coherent setup: for example the feather is missing while oil is present, or a hand moves with no oil or feather anywhere in the shot, or the tray is missing while the other objects float against an undefined background.
level_3: The tray with visible water is present, dark oil sits on the water surface, and a clean feather floats on that same surface, and a hand is visible near the tray and moving, but the hand's motion is not clearly slow and gentle (it looks abrupt, jerky, or the hand stays still), or the oil and feather are not both visible together in the same continuous shot.
level_4: The tray, the oil, the feather, and a hand performing a slow, smooth sweeping motion near (but not touching) the water surface are all present and visible together in the same frame throughout the 10-second sequence, with no cut or occlusion hiding any of them.
level_5: Everything in level 4 holds, and in addition the hand stays visibly near the water's surface without ever touching the oil or the feather throughout its motion, the tray, oil patch, and feather remain visible in the same continuous shot for the full sequence, and the camera viewpoint stays fixed and level with no tilt, zoom, or cut for the whole video.

Scientific and Causal Correctness rubric:
level_1: The oil never appears as a dark, cohesive film distinct from the water; the feather is submerged, badly discolored, or missing entirely; the water shows no visible boundary between the oil and the clear water; nothing resembling spreading or surface disturbance takes place.
level_2: The oil appears but behaves implausibly: for example it shows a color wrong for crude oil (translucent, bright blue, bright yellow) or dissolves into the water like a dye instead of staying as a separate film; the feather sinks or becomes soaked with no visible spreading process; the hand's motion produces splashing or turbulent chop rather than smooth surface ripples.
level_3: The oil forms a cohesive dark film that stays visually distinct from the water, the feather starts out clean and floating, and the hand's slow motion produces visible ripples on the surface, but the oil film does not visibly respond to those ripples; it neither spreads nor advances as ripples pass near it, so there is no visible link between the hand's motion and the oil's movement.
level_4: Everything in level 3 holds, and in addition the oil film visibly spreads outward in the same direction the ripples travel, its leading edge advancing further with each successive ripple rather than staying static or spreading in an unrelated direction; the oil stays cohesive as it spreads, with no droplets breaking off and no retreat back toward its starting point.
level_5: Everything in level 4 holds, and in addition the spreading oil film's leading edge visibly reaches the feather, and the feather's surface becomes visibly darkened and coated where the oil touches it (the feather does not stay untouched), with the coating appearing only after the oil film's edge has visibly traveled from its pour point to the feather's location, so the contact reads as the endpoint of the wave-driven spreading rather than an instantaneous or pre-existing state.

Spatiotemporal Consistency rubric:
level_1: Severe breaks in continuity: the tray, oil, feather, or hand vanishes and reappears between frames; the water surface's geometry distorts implausibly, such as rippling with no visible cause or the reflection plane shifting inconsistently; the scene suddenly switches from daylight to darkness or back again partway through the shot.
level_2: Moderate breaks: the hand disappears and reappears across frames; the feather jumps by more than its own length from one frame to the next instead of drifting smoothly; the oil film flickers in and out of existence between frames; the water surface loses its flat, continuous look, showing visible warping or an implausible bulge.
level_3: Minor but noticeable flaws: the hand's motion briefly freezes for a couple of frames mid-sweep before continuing; the feather shows a slight positional jitter that doesn't match the ripple pattern near it; the oil film's edge breaks into disconnected patches for a moment in a way that doesn't match how a cohesive liquid film would behave; the specular highlight on the water shifts placement between frames in a way that doesn't match the ripple motion.
level_4: The tray stays in a fixed position and the water surface stays flat and reflective; the feather floats steadily, moving only in small increments that track the nearby ripples; the oil film moves as one connected sheet rather than in disconnected pieces; the hand follows one continuous path with no freeze, jump, or moment where it incorrectly passes in front of or behind another object.
level_5: Everything in level 4 holds, and in addition the ripples' outward speed looks physically reasonable for their visible size, neither instant nor unnaturally slow; the oil's leading edge advances at a pace that plausibly follows the ripples reaching it rather than moving independently of them; the feather's small movements scale with the size of the ripples passing under it; and there is no shift in framing or apparent camera position at any point in the sequence.