Domain: Natural Science — Physics
Target concept: Leidenfrost Effect

Video generation prompt: Place a metal spoon on a lit alcohol lamp and heat the spoon until it is red-hot; then add a drop of water onto the spoon.

Evaluation guide:
(i) Target concept: Leidenfrost Effect, sustained levitation and mobility of a liquid droplet on a superheated solid surface due to self-generated insulating vapor layer.
Minimum mechanism: Surface temperature must exceed water"s Leidenfrost point (~193°C); droplet must remain intact (non-wetting, non-boiling) long enough to exhibit observable skittering motion and vapor emission; vapor layer must be visually implied by droplet shape preservation and interface haze.
(ii)Storyline: Phase 1: Spoon is positioned above flame and begins heating (no glow yet); Phase 2: Spoon tip transitions to uniform red-orange incandescence (thermal radiation dominant); Phase 3: Water droplet is released and makes contact; Phase 4: Upon contact, droplet retains perfect sphere, lifts slightly, and initiates horizontal motion while emitting translucent vapor; Phase 5: Droplet continues skittering with persistent shape and vapor until exit or evaporation. Perspective constraint: Fixed frontal view showing spoon-lamp-water spatial triad continuously; visibility constraint: All key events must occur within field-of-view without occlusion; no close-up cuts or POV shifts.

Manual:
Experimental Procedure
1. Place a metal spoon horizontally over the flame of a lit alcohol lamp.
2. Hold it steady until the spoon tip glows uniformly red-hot.
3. Using a dropper, place one clear water droplet onto the red-hot spoon surface.
Observation of Experimental Phenomena
The water droplet remains spherical, skitters rapidly across the spoon surface, and emits a faint white vapor cloud — it does not boil away instantly nor spread flat.
Summary of Experimental Principles
The Leidenfrost Effect: When liquid contacts a surface significantly above its boiling point, a vapor layer forms beneath the droplet, insulating it and enabling sustained levitation and mobility.

Prompt Grounding rubric:
level_1: No metal spoon, no alcohol lamp with a flame, and no water droplet appear anywhere in the clip; none of the three staged actions (spoon placed over the lamp flame, spoon heated to a red-hot glow, water droplet dropped onto the spoon) is shown.
level_2: Only one of the three core elements (spoon, lit alcohol lamp, water droplet) is shown; e.g. the spoon appears but is never brought near the flame, or a droplet appears without any heated spoon under it, or the lamp is shown but never lit.
level_3: All three core objects are shown - metal spoon, alcohol lamp with a visible flame, water droplet delivered by a dropper or similar - and the three staged actions occur in the right order: spoon positioned over the lit flame, spoon reaches a visibly red-hot state, then a droplet lands on the spoon; however framing or spacing is off, e.g. the spoon sits noticeably away from the flame, or the droplet lands slightly off-center on the spoon's bowl.
level_4: All of the 3-point requirements hold, and additionally the spoon is unmistakably metallic (handle plus bowl shape), the lamp shows a wick and flame, and the droplet is a clear round bead of water; the spoon sits directly in the flame's heat zone, the droplet lands squarely on the heated bowl of the spoon, and the red-hot glow is visibly established before the droplet is released - no ambiguity about which action happens first.
level_5: Everything required for score 4 holds, and in addition the camera holds a single fixed frontal framing that keeps the lamp, spoon, and droplet-drop point in view for the whole clip (no cut, zoom, or reframing), the spoon's glow is shown as a continuous, evenly colored red-orange rather than flickering on and off, and the droplet is released from a consistent, visible source (e.g. a dropper tip) directly above the spoon so the 'add a drop of water' action is unambiguous.

Scientific and Causal Correctness rubric:
level_1: No scientifically plausible Leidenfrost behavior appears: the droplet boils away instantly with a hiss, or spreads out and evaporates the way it would on a merely warm spoon, or a vapor cloud appears before the droplet ever touches the spoon.
level_2: One of the core state changes needed for the effect is missing or backwards: the spoon never visibly changes from its metallic color despite being 'heated,' or the droplet disappears the instant it lands with no sizzle, motion, or vapor, or water is shown landing before the spoon shows any red glow.
level_3: The spoon is shown glowing red-hot, the droplet lands on it, and vapor is generated quickly - but the signature Leidenfrost behavior (a droplet that stays whole and skitters around for at least a couple of seconds rather than vanishing) doesn't appear; instead the droplet flattens, bursts, or boils off within the first instant of contact.
level_4: All of this is present and in the right causal order: the spoon visibly shifts from its normal metal color to a steady red-orange glow before contact; once the droplet lands it keeps a rounded, bead-like shape for several visible moments rather than flattening; it visibly slides or skitters across the spoon surface while intact; a thin white vapor is visible around it; nothing in the clip shows the droplet boiling flat, splashing, or soaking into the spoon during this phase.
level_5: Everything above holds, and in addition the droplet's rounded shape holds up through its whole visible skitter (it doesn't flatten partway through), its travel across the spoon stays essentially along the surface rather than bouncing or leaping off it, the vapor appears to hug the droplet's underside and grows as it moves rather than appearing all at once, and no second droplet, puddle, or residue forms elsewhere on the spoon - the levitating-droplet behavior reads as one clean, easy-to-follow effect.

Spatiotemporal Consistency rubric:
level_1: A severe break in continuity occurs - e.g. the spoon jumps to a different position between shots, the flame vanishes and reappears without being blown out or relit, the water droplet appears in mid-air out of nowhere, or the spoon visibly bends, melts, or changes shape.
level_2: A clear but less extreme continuity problem occurs - e.g. the spoon's position or angle jumps between the heating and water-adding shots, the flame goes out and comes back with no visible cause, the droplet appears already formed on the spoon with no visible release/drop moment, or the lighting shifts dramatically (e.g. from natural daylight to a studio spotlight) partway through the sequence.
level_3: The spoon, lamp, and droplet stay in a sensible, stable arrangement throughout - spoon held over the flame, droplet released from a visible source and traveling to the spoon - with no object popping in or out of the scene; minor camera jitter or a brief moment of soft focus is acceptable as long as the sequence of events stays easy to follow.
level_4: All of the above holds, and additionally there is no spoon jump, no melting or bending, and no sudden change in lighting; the spoon stays rigid and in place over the flame, the droplet falls in a smooth, direct path to the spoon surface, and the flame keeps a steady size and shape - every motion looks physically reasonable and the clip runs as one continuous take without visible jump cuts.
level_5: Everything required for score 4 holds, and in addition the spoon's position in frame stays fixed with no visible jump, warp, or drift once it is over the flame; the flame shows only the kind of gentle natural flicker a small open flame normally has, without ever freezing or snapping to a different shape; the droplet's fall and its motion across the spoon look like one continuous, evenly paced event rather than skipping or changing speed abruptly; and the vapor trailing the droplet spreads outward smoothly rather than appearing in disconnected puffs.