Domain: Natural Science — Marine Science
Target concept: Sea Ice Formation and Salt Exclusion (Brine Rejection)

Video generation prompt: Fill natural seawater into a transparent container, leaving a small headspace at the top and sealing it just loosely enough to vent as the contents expand, and place it in a low-temperature freezing environment, then capture the entire process of water freezing and internal material changes through time-lapse photography.

Evaluation guide:
(i) Target concept: Brine rejection during sea ice formation requires simultaneous presence of (a) saline aqueous solution, (b) directional thermal gradient enabling crystal nucleation and growth, and (c) physical confinement preventing bulk mixing. Minimum mechanism: Salt ions cannot incorporate into ice lattice → rejected into interstitial liquid → density increase → gravitational segregation → visible dark inclusions in ice and/or sinking plumes.
(ii)Storyline: [Frame 0] Natural seawater fills the transparent container up to just below the rim, leaving a small headspace, level stable, surface calm. [Frame T1] Freezing initiates at top/side interface: first opaque white ice layer appears with coarse granularity. [Frame T2] Ice thickens directionally; dark brine inclusions emerge *within* ice near growth front. [Frame T3] Inclusions descend vertically relative to ice boundary while unfrozen zone shrinks and retains transparency. [Frame T4] Final state: majority ice volume with embedded descending brine streaks; residual liquid occupies bottom region, darker and denser than initial seawater. All phases observed from fixed frontal viewpoint; no occlusion; lighting consistent; container remains motionless, with its lid on and headspace intact.

Manual:
Experimental Procedure
1. Fill a transparent container with natural seawater, leaving a small headspace at the top, and seal it loosely enough to vent as the contents expand on freezing.
2. Place container into a low-temperature freezing environment.
3. Capture entire freezing process via time-lapse photography.
Observation of Experimental Phenomena
- Ice forms directionally (e.g., top-down), appearing translucent-to-opaque white.
- Unfrozen seawater remains visible beneath/adjacent to ice.
- Dark brine-rich inclusions appear within ice and migrate downward during freezing.
- Clear contrast between ice (lighter, granular) and liquid (darker, transparent).
Summary of Experimental Principles
- Sea ice forms when seawater cools below its freezing point (~−1.8°C), but dissolved salts inhibit complete freezing.
- As ice crystals form, salt is excluded into surrounding liquid, increasing local salinity and density — a process called brine rejection.
- Rejected brine becomes trapped in channels or sinks as dense plumes, creating visible dark inclusions in the ice matrix.

Prompt Grounding rubric:
level_1: No transparent container is shown; no seawater is visible; there's no sign of a freezing environment; the clip has no time-lapse structure (e.g., it's one static shot or a set of disconnected jump cuts); none of the three steps (filling, placing in the cold, and capturing the freeze) appear.
level_2: At least one of the following shows up: the transparent container, the seawater, or cues of a cold environment (e.g., frost on the outside), but the sequence doesn't hold together: for instance the container appears empty after supposedly being filled, freezing begins before the container is placed in the cold setting, or there's no real time-lapse pacing (just one still shot or erratic jumps).
level_3: The transparent container, the seawater inside it, and a freezing setting (implied by visible cold cues) are all present; the three steps happen in order: seawater is shown inside the container, the container is placed into the cold environment (e.g., moving into a freezer or cold chamber), and the time-lapse pacing is evident from a steady, compressed passage of time showing the state changing.
level_4: Everything from the 3-point level holds, and the container stays completely still for the whole time-lapse; the seawater fills the container to the same visible level before freezing starts as afterward, allowing for the small headspace left at the top; nothing unrelated (gloves, labels, tools) enters the frame; the camera view never zooms, pans, or cuts away.
level_5: Everything from the 4-point level holds, and the container is visibly closed with a lid or cap while still showing a small headspace/air gap at the top (rather than being packed completely full and rigid), consistent with a vent that lets the contents expand as they freeze; the freezing environment is confirmed from the outside, for example frost building up on the container's exterior or visible cold vapor in the background, with all of this visible at once and unambiguous.

Scientific and Causal Correctness rubric:
level_1: No sign of any phase change: the liquid stays fully clear and see-through the whole time; there's no brine escaping, no cloudiness, no separation; any ice that appears looks like a single uniform white or gray block with no internal structure; there's no visible difference in appearance between the ice and the liquid beneath it.
level_2: Ice forms, but with no internal structure to it: the whole volume turns to ice at once with no streaks, channels, or dark inclusions, and nothing sinks or floats within it; the seawater's color looks exactly the same before, during, and after freezing; there's no visible sign that ice and liquid are separating by density.
level_3: Ice visibly grows in from the top or from one side; the solid ice looks translucent-to-opaque white; unfrozen seawater is still visible below or next to the ice; there's a clear visual contrast between the lighter, less see-through ice and the darker, clearer liquid; the ice doesn't start forming at the bottom first without some visible disturbance (like convection) to explain it.
level_4: Everything from the 3-point level holds, and brine rejection is visible: dark, concentrated streaks or droplets show up within or just beneath the ice; the unfrozen liquid right next to the ice looks a bit cloudier or grainier than the rest; these dark streaks and cloudy patches don't blend back into the surrounding ice or liquid; they stay put and stay visually distinct from one frame to the next.
level_5: Everything from the 4-point level holds, and the dark brine streaks stay trapped inside the ice rather than floating loose in the liquid; they visibly move downward relative to the ice boundary as freezing continues (higher up in earlier frames, lower down in later ones); the unfrozen liquid stays clearer than the ice throughout; nothing looks artificially added: no uniform glitter, no bubbles rising upward, no dye-like color that wouldn't come from real salt exclusion.

Spatiotemporal Consistency rubric:
level_1: The container suddenly jumps to a different spot or size between frames; the lighting swings from bright daylight to near-total darkness within a single cut; ice appears or vanishes without any in-between stage of forming; the container looks cracked in one frame and whole again in the next; the liquid level changes with no visible cause.
level_2: The container shifts position across more than a couple of frames without any visible motion connecting them; the ice boundary grows, then visibly retreats, then grows again instead of advancing steadily; the lighting flickers or the shadows on the container/ice swing to a different side more than once with no change in the room; the unfrozen liquid appears to increase partway through the freeze; the container's shape changes without anything pushing on it.
level_3: The container sits in the same spot in the frame the whole time; the ice grows steadily inward from one direction (from the top or one side) without ever pulling back; the volume of unfrozen liquid keeps shrinking, never growing; the side of the container that looks brighter (facing the room's light) stays the same side across the whole clip; the container and ice keep their true shape, with no stretching, bending, or warping.
level_4: Everything from the 3-point level holds, and the ice front creeps forward in small, steady increments rather than jumping ahead in visible leaps; the liquid surface (where still unfrozen) stays flat and undisturbed, without ripples or waves appearing from nowhere; nothing passes in front of the container to block the view (no hand, no reflection flare cutting across); no frame repeats itself or skips ahead, leaving a visible gap in the freezing progress.
level_5: Everything from the 4-point level holds, and the container walls stay crisp and steady with no shimmer or flickering along their edges; the ice's texture thickens and its grain gets visibly coarser in a smooth progression rather than changing in sudden bursts; there are no sudden flashes of brightness or odd color speckling between frames; any blur present matches the slow pace of the time-lapse itself, with no directional smear that isn't explained by the camera's own motion (which shouldn't be present in the first place).