Domain: Natural Science — Atmospheric Science
Target concept: Frost ice gradually condenses outward from a cold metal rod exposed in subfreezing fog.

Video generation prompt: A metal rod is held stationary in a subfreezing chamber, with a narrow jet of fine liquid-water mist aimed continuously at one small spot on one side of the rod.

Evaluation guide:
(i) Target concept: Contact-freezing-driven directional frost propagation on a thermally conductive rod exposed to a localized jet of supercooled liquid-water mist.
Minimum mechanism: The rod's surface is below 0°C; the mist is liquid water (not vapor) that stays in a metastable, supercooled state until it strikes the rod; because the jet is narrow and aimed at one small region, freezing first nucleates there, and the rod's metal conducts heat away fast enough for the resulting frost front to then spread outward from that single spot along the surface.
(ii)Storyline: [Frame 0–2] The narrow mist jet is already aimed continuously at one small region on one side of the rod → [Frame 3–4] the first visible frost nucleates right at that contact spot → [Frame 5–7] frost spreads outward from the contact spot along the rod's surface, showing a visible advancing edge → [Frame 8–10] frost near the original contact spot thickens and turns more opaque while the rest of the rod, including the side facing away from the jet, stays bare and shiny; the whole sequence is shot from a fixed frontal angle with no camera movement or occlusion.

Manual:
Experimental Procedure
1. Place a clean, bare metal rod vertically inside a sealed subfreezing chamber (-10°C or colder).
2. Aim a narrow fine-mist nozzle so that it delivers a steady, low-velocity jet of liquid water droplets at one small region on one side of the rod, leaving the rest of the rod unmisted.
3. Keep the rod stationary and the jet aimed at that same spot for about 10 seconds while recording.
Observation of Experimental Phenomena
Frost first appears at the small spot where the mist jet strikes the rod, then gradually spreads outward along the rod's surface as an opaque, white, crystalline deposit — starting from that contact spot and advancing across the impinged side, with no frost forming on the side facing away from the jet or anywhere in the surrounding air.
Summary of Experimental Principles
When supercooled liquid water droplets strike a surface below freezing point, they freeze on contact. Because the mist arrives as a narrow jet rather than a broad spray, freezing begins at that one small spot; the metal rod then conducts the released latent heat away quickly enough that neighboring supercooled droplets nucleate on the growing ice rather than freezing independently, so the frost front advances outward from that original contact spot.

Prompt Grounding rubric:
level_1: No metal rod is visible; or there is no enclosed subfreezing chamber (no insulated enclosure, no cold vapor or fog visible inside); or no mist/water spray of any kind is shown near the rod.
level_2: A metal rod and some kind of mist are both visible, but the mist does not read as a jet aimed at a small region of the rod: for example it fills the whole chamber uniformly, drifts away from the rod, or seems to originate from the rod itself; and/or the chamber does not look convincingly subfreezing (no fog, no condensation on the walls, lighting and set dressing suggest an ordinary room).
level_3: A metal rod is held stationary inside a chamber that reads as enclosed and subfreezing; a mist jet is visibly aimed at one small region on one side of the rod, distinct from a broad spray covering the whole lateral surface; nothing else in the shot contradicts this setup.
level_4: The rod stays centered and consistently framed, and the mist jet's direction is clearly perpendicular to the rod's long axis and confined to that one small target spot, never drifting onto the opposite side or the rod's ends; the chamber walls or air show visible frost, condensation, or fog confirming the subfreezing setting.
level_5: The rod reads as genuinely metallic (shiny, rigid, non-porous), the mist is a translucent, droplet-like spray rather than steam or smoke, and the chamber interior keeps a persistent low-visibility cold fog throughout; the rod, the localized mist jet, and the chamber all remain visually coherent together for the full ~10 seconds with no interruption or mismatched compositing.

Scientific and Causal Correctness rubric:
level_1: No frost ever appears anywhere in the shot; or frost shows up on some unrelated surface (chamber wall, the mist nozzle) before it appears on the rod; or frost appears across the rod all at once the instant the mist starts, with no gradual buildup.
level_2: Frost appears somewhere other than the rod (e.g., only on the chamber wall or nozzle) rather than on the rod itself; or frost does appear on the rod but covers the whole impinged side in one step rather than starting at the small spot the jet is aimed at; or the frost reads as a flat, textureless white coating rather than showing any crystal-like structure.
level_3: Frost first appears exactly at the small spot where the mist jet strikes the rod, and from there it visibly spreads outward along the rod's surface as time passes, rather than appearing everywhere on the impinged side at once; frost stays confined to the rod and never appears on the nozzle or floats in the mist itself.
level_4: Beyond that outward spread from the contact spot, the frost also gets visibly thicker and more opaque the closer it is to that original spot, forming a rough gradient rather than a uniform coat; the rod's far side (facing away from the jet) and its two ends stay bare throughout; once a patch of rod has frosted, it does not go bare again or get skipped over as the front advances.
level_5: The frost's texture itself changes as it develops: it starts as fine, dew-like beads near the contact spot, then takes on a feathery or spiky look as it thickens, and finally settles into a solid, granular, opaque white layer, and this progression always happens outward from the original contact spot, never appearing first somewhere downstream of the front or jumping backward toward already-frosted rod.

Spatiotemporal Consistency rubric:
level_1: The rod jumps to a new position or angle between frames; the mist jet cuts on and off or disappears and reappears without explanation; a patch of frost appears fully formed in a single frame with no earlier trace of it forming; or the apparent light source in the chamber jumps to a different position or brightness from one moment to the next.
level_2: The rod stays roughly in place but visibly warps, stretches, or flickers in and out of transparency; the mist jet shows gaps where droplets seem to skip ahead in space; frost forms in patches that appear out of sequence (for instance, a spot farther from the nozzle frosts over before the spot directly under it); or the chamber walls change shape or the implied camera vantage shifts partway through.
level_3: The rod holds a fixed position, angle, and size throughout; the mist jet stays aimed continuously in the same direction with no visible breaks or reversals; the frost keeps advancing along the rod without skipping ahead or reversing; and the shadow the rod casts inside the chamber stays on the same side and roughly the same length across the sequence, consistent with a jet and rod that never move.
level_4: In addition, the mist droplets keep a coherent, plausible trajectory rather than suddenly scattering or converging; the visible edge of the frost advances at a steady, visually even pace along the rod rather than lurching forward or stalling and then jumping; and the mist never appears to pass through the solid body of the rod.
level_5: There is no parallax shift among the rod, the mist jet, and the chamber walls, confirming the camera never actually moves; the way the mist's density and the frost's opacity fade with distance from the nozzle and from the contact spot stays visually consistent frame to frame; and the footage shows no strobing, ghosting, or duplicated frames, nor does the rod bend or the mist stream shear in ways a rigid rod and a steady jet would not.