Domain: Natural Science — Physics
Target concept: Liquid rapidly crystallizes, turns white, releases heat, and solidifies.

Video generation prompt: A supersaturated sodium acetate solution at room temperature is contained in a transparent vessel; the solution is slowly poured onto a solid sodium acetate crystal in a shallow dish.

Evaluation guide:
Target concept: Nucleation-triggered exothermic crystallization in a supersaturated solution. Minimum mechanistic assumptions: (i) supersaturated solution is metastable and kinetically trapped; (ii) a seed crystal provides a lattice-matched template for rapid heterogeneous nucleation; (iii) phase transition to solid releases latent heat detectable via condensation; (iv) microcrystalline structure causes broadband light scattering → opaque white appearance. Phased storyline: [Phase 1: Static setup] Clear liquid in transparent vessel; isolated dry crystal in shallow dish. [Phase 2: Trigger] Laminar liquid stream makes precise first contact with crystal surface. [Phase 3: Causal cascade] Within 0.1 s: localized whitening at contact point → within 0.5 s: sharp radial front advances → within 1.2 s: full opaque white solid formed. [Phase 4: Thermal verification] Within 0.3 s of whitening: micro-condensation halo appears on vessel wall adjacent to solid. Visibility constraints: Camera must capture contact point at ≥120 fps; lighting must be diffuse and glare-free to resolve whitening onset and condensation; perspective must be orthogonal to dish plane to verify radial symmetry; no occlusion of crystal, contact zone, or vessel interior wall.

Manual:
I. Basic Demonstration Information
Demonstration Title: Supersaturated Sodium Acetate Crystallization (Rapid Solidification with Exothermic Whitening) Demonstration
Subject: Natural Science - Physics - Phase Transitions & Thermodynamics
Demonstration Purpose: To visually demonstrate nucleation-triggered rapid crystallization in a supersaturated solution, emphasizing the observable phenomena of instantaneous solidification, opaque white color development, and exothermic heat release — reinforcing the principle that phase change from metastable liquid to stable solid releases latent heat and alters optical properties.

II. Demonstration Carrier/Equipment
Core Carrier: Supersaturated sodium acetate trihydrate solution (room temperature, 20–25°C, prepared and stabilized to prevent spontaneous nucleation), transparent cylindrical vessel (glass or acrylic, 50–80 mL capacity, wall thickness ≥2 mm to minimize distortion), shallow white ceramic dish (diameter 8–10 cm, matte finish), single sodium acetate trihydrate crystal (2–3 mm, faceted, dry, stored desiccated).
Auxiliary Equipment: Stable tripod-mounted camera (120+ fps, macro lens), neutral gray background, diffused overhead LED lighting (5600K, no glare), optional infrared thermal overlay (for validation only, not required in video).

III. Demonstration Content Description
Layout: Place shallow dish on level surface against neutral background. Center crystal precisely in dish. Position transparent vessel 15 cm above dish, aligned vertically. Ensure no vibrations or air currents.
State Control: Solution must be perfectly still, bubble-free, and optically clear (no haze). Crystal must be dry and free of dust or moisture film. Temperature must be stable (±0.5°C) to avoid premature nucleation.
Pouring Protocol: Slowly tilt vessel to initiate laminar pour (flow rate ~0.5 mL/s); maintain stream diameter ≤3 mm; ensure first droplet contacts crystal surface directly — no splashing or peripheral impact.

IV. Observation of Core Phenomena
Initial State: Liquid is colorless, transparent, and motionless; crystal is small, translucent-white, geometrically defined.
Trigger Event: First liquid–crystal contact — instantaneous, localized, unambiguous.
Crystallization Sequence: Within 0.1 s: whitening initiates *exclusively at contact point*; within 0.5 s: white front propagates radially as sharp, advancing boundary; within 1.2 s: entire poured volume transforms into cohesive, opaque white solid with matte, snow-like surface texture.
Thermal Signature: Within 0.3 s of whitening onset, micro-condensation forms as a faint, circular halo on inner vessel wall adjacent to solid; persists ≥1.0 s.
Stability: Solid remains rigid, non-dripping, non-melting for ≥5 s; no bubbling, cracking, or phase separation.

V. Summary of Key Knowledge Points and Principles
Core Concept Definition: Supersaturation is a metastable state where solute concentration exceeds equilibrium solubility; introduction of a nucleation site (e.g., seed crystal) triggers rapid, exothermic phase transition to stable solid phase.
Physics Principle: Crystallization releases latent heat of fusion (≈264 J/g for NaOAc·3H₂O), raising local temperature and causing transient condensation; the white appearance arises from light scattering by microcrystalline domains (Mie scattering), not pigment.
Verification Logic: Visual feature recognition relies on strict sequence: (1) clear liquid + dry crystal → (2) contact → (3) *immediate* whitening at contact → (4) *radial propagation* → (5) *opaque white solid* → (6) *localized condensation*. Any deviation invalidates the demonstration.

Prompt Grounding rubric:
level_1: No transparent vessel with liquid is shown; no shallow dish appears; no visible sodium acetate crystal appears; no pouring action occurs; the objects on screen don't match the setup at all (e.g., an opaque container, colored liquid, a powder instead of a crystal, or nothing resembling a crystallization setup).
level_2: Some pieces appear but are clearly wrong: a clear vessel of liquid and a dish are present, but the 'crystal' is actually a salt pile, sugar cube, or other wrong object; or the liquid is poured onto an empty dish or the wrong spot rather than near any crystal.
level_3: The core objects are present with rough fidelity: a transparent vessel of colorless liquid, a shallow dish, and a small white crystalline object in the dish, but the liquid is poured beside the crystal rather than directly onto it, or it's unclear whether the stream actually touches the crystal at all.
level_4: All core objects are correctly represented and arranged: a colorless, still, bubble-free liquid in a transparent vessel; a shallow white dish; a single, small, faceted, translucent-white crystal placed roughly centrally in the dish; the liquid is poured slowly and visibly makes contact with the crystal. Minor flaws like slight motion blur at the moment of contact, or a crystal that's a bit oversized or irregular (but still clearly a crystal), are acceptable.
level_5: Perfect setup fidelity: (i) the vessel shows a clear, still, colorless liquid with no cloudiness or sediment; (ii) the dish is flat, matte, and empty except for one small, clearly faceted, translucent-white crystal centered in it; (iii) the pour is slow, controlled, and unmistakably lands directly on the crystal's surface; (iv) nothing extraneous (no stray objects, labels, hands, or distracting background) appears anywhere in frame; (v) framing and lighting keep the vessel, dish, and crystal all clearly visible and unobstructed throughout.

Scientific and Causal Correctness rubric:
level_1: No crystallization is seen; the liquid stays unchanged or disappears (evaporating or dripping away) without solidifying; there's no sign of heat release (no steam, fogging, or thermal shimmer); the poured liquid and the resulting solid seem unconnected; or the sequence is physically backwards (e.g., the liquid solidifies before it even touches the crystal, or turns black/red instead of white).
level_2: Something solidifies, but the physics doesn't add up: a white solid appears with no crystal to trigger it; any hint of heat release comes from an unrelated cue (like random ambient steam); the solid looks shattered/brittle or like a loose slurry rather than a cohesive white mass; there's no visible sign of released heat anywhere nearby (no condensation on the glass, no faint shimmer above the new solid).
level_3: Crystallization clearly starts only after the liquid touches the crystal and keeps developing, but it's slow and patchy rather than a clean sweep, taking more than about 3 seconds and leaving parts still looking damp or translucent instead of a solid opaque white; there's no visible thermal sign nearby (no fogging on the glass, no subtle brightening from heat); the boundary between liquid and solid isn't clearly sharp.
level_4: The whole causal chain reads clearly: contact with the crystal triggers near-immediate nucleation, then a visibly rapid radial spread into a cohesive, opaque white solid; there's a mild but visible sign of released heat: a faint patch of condensation on the vessel wall near the pour zone, or a subtle shimmer above the new solid within about a second of it forming; the solid has a smooth, matte, snow-like look; it doesn't melt or revert back to liquid while still on camera.
level_5: The causal chain is complete and reads as essentially instantaneous and physically convincing: (i) whitening begins right where the liquid meets the crystal, with no perceptible delay; (ii) the white front visibly races outward from that point rather than crawling slowly; (iii) the finished solid is uniformly opaque white with a crisp liquid-solid boundary and no cloudy or translucent patches; (iv) a clear, localized patch of condensation forms on the vessel's inner wall right next to the new solid and stays visible for at least a couple of seconds afterward; (v) nothing else disrupts the demonstration (no bubbling, splashing, or cracking); the whole transition looks smooth, quiet, and self-consistent with a genuine exothermic phase change.

Spatiotemporal Consistency rubric:
level_1: A severe break in continuity: the crystal disappears mid-pour; the solid appears before the liquid even reaches it; the dish changes shape or position between frames; the liquid appears to flow upward; there's an obvious time-jump (like skipping straight from just-starting to fully finished with nothing in between); the lighting flips abruptly (e.g., day to night).
level_2: Multiple visible continuity problems: the crystal noticeably shifts position between frames; the poured liquid stream appears to jump or teleport rather than flow continuously; the solid grows unevenly in an implausible way (e.g., only from the edges inward); condensation shows up on the opposite side of the vessel from where the solid actually formed; the video visibly stutters or freezes for a noticeable stretch.
level_3: Minor but noticeable slips: the crystal appears to rotate slightly with no visible cause; the solidification front advances unevenly (faster on one side than the other) without explanation; condensation appears a beat later than it should relative to when the solid finishes forming; the lighting across the dish shifts subtly partway through.
level_4: High continuity throughout: the crystal stays essentially fixed in place; the poured liquid stream stays smooth and coherent rather than breaking into drops; the solidification front advances smoothly and fans out fairly evenly in all directions; condensation appears in step with the solid's growth and roughly follows its spreading edge; the lighting and camera angle stay steady; no dropped frames or stutter.
level_5: Excellent spatiotemporal consistency throughout: (i) the crystal shows no visible drift in position; (ii) the liquid stream's speed changes naturally as it falls (it doesn't look like a constant-speed special effect); (iii) the solidification front advances outward at a steady, visually even pace, staying roughly circular and symmetric rather than lopsided; (iv) condensation appears essentially together with the first visible whitening and spreads outward at a matching pace; (v) the camera's perspective, lighting angle, and shadows stay the same across the whole clip; (vi) there's no visible interpolation glitching, motion smearing, or focus-shifting that breaks the illusion of a single continuous real recording.