Domain: Natural Science — Chemistry
Target concept: Fog formation by dripping water: Reaction between iodine and zinc (with water as a catalyst)

Video generation prompt: The reaction between iodine and zinc (with water as a catalyst): A gray mixture of iodine powder and zinc powder is placed in a mortar. One drop of water is added using a pipette, and the mortar remains undamaged.

Evaluation guide:
(i) Target concept: Water-catalyzed solid-state redox reaction between zinc and iodine powders, producing transient visible violet-to-purple fog from sublimed iodine vapor.
Minimum mechanism: Water must initiate the reaction at the powder interface; heat released by the Zn + I2 reaction must be sufficient to sublime unreacted iodine into gaseous I2, which is intrinsically violet-to-purple in color; the rising fog is this suspended iodine vapor (possibly with a faint whitish steam tinge right at the point of contact), not a colorless or white-only vapor, and no flame or charring should appear.
(ii)Storyline: [Frame 0] Static shot: mortar containing homogeneous gray powder mixture centered in view. [Frame 1–2] Pipette enters top of frame, held still above mixture. [Frame 3] Water droplet detaches from pipette tip and descends vertically. [Frame 4] Droplet contacts mixture surface → immediate localized darkening at impact site. [Frame 5] Violet-to-purple fog (sublimed iodine vapor) emerges precisely at the contact point and rises vertically in a continuous column. [Frame 6–9] Fog sustains upward motion with gradual dispersion, deepening then fading in tint; mixture remains solid, gray, and confined; mortar shows no structural change. Perspective: fixed frontal close-up; full mortar interior always visible; no occlusion of contact zone or fog base.

Manual:
Experimental Procedure
1. Place gray mixture of iodine powder and zinc powder into mortar.
2. Hold pipette vertically above mixture.
3. Release one drop of water from pipette onto mixture.
Observation of Experimental Phenomena
- Gray mixture remains solid and unmoved.
- Upon water contact, a dense violet-to-purple fog (sublimed iodine vapor) forms instantly at the contact point and rises vertically.
- Mortar remains undamaged and intact.
Summary of Experimental Principles
Iodine and zinc react exothermically in the presence of water as a catalyst, producing zinc iodide and releasing heat; this heat sublimes residual molecular iodine (I2), which is characteristically violet-to-purple as a vapor, producing the visible colored fog (with at most a faint whitish steam tinge right at the contact point).

Prompt Grounding rubric:
level_1: No mortar appears anywhere in frame; no iodine powder, no zinc powder, and no gray powder blend is shown; no pipette is present; no water droplet appears at any point.
level_2: A mortar appears but holds only zinc powder or only iodine powder rather than the combined gray blend, or is empty; a pipette is present but never brought near the mortar; a water droplet is shown detached from any pipette tip with no mortar beneath it; or the powder blend inside the mortar is the wrong color (e.g., pure violet, solid black, or a shiny metallic look instead of matte gray).
level_3: A mortar holding a gray powder blend, a pipette poised above it, and a single water droplet leaving the pipette tip toward the mortar are all shown together; no extra containers, reagents, or tools beyond this iodine-zinc setup appear anywhere in frame.
level_4: Everything in score 3 holds AND the falling droplet is shown reaching and touching the gray blend inside the mortar; the pipette stays in place while releasing it; and the mortar shows no cracks, chips, or breakage either before or after the droplet lands.
level_5: Everything in score 4 holds AND only one droplet is ever introduced; the gray powder blend sits centered in the mortar bowl; the pipette tip lines up directly above the center of that blend at the instant of release; and the mortar stays visibly whole and unmarked (no cracks, chips, or discoloration of its surface) in every frame.

Scientific and Causal Correctness rubric:
level_1: No reaction is visible at the droplet-contact point: the gray Zn/I2 blend stays unchanged, with no darkening, no vapor, and no haze; the water droplet simply beads up, evaporates, or vanishes without any visible effect.
level_2: A reaction is shown but with the wrong phenomenology for this system: the blend bubbles, foams, or produces an open flame or sparks, or the vapor rising from it is blue, green, or bright yellow, or the blend turns bright red/orange, none of which match the zinc-iodine-water system, whose real visible product is violet-to-purple iodine vapor, not fire or unrelated colors.
level_3: The gray blend darkens sharply right where the droplet lands, and within about one to two frames a visibly violet-or-purple-toned fog rises from that same spot; no open flame, melting, or scattering of solid particles occurs.
level_4: Everything in score 3 holds AND the rising fog stays violet-to-purple in tone for the whole event (never plain white and never any unrelated hue), comes only from the droplet-contact point, and climbs as one continuous column while the rest of the gray blend stays solid and undisturbed.
level_5: Everything in score 4 holds AND the violet-purple fog is dense enough to read as clearly opaque against the background, its tint visibly deepens as more iodine sublimes, no unrelated color patches (green, blue, or black soot) appear anywhere in the fog or on the blend's surface, and no second fog source appears away from the contact point.

Spatiotemporal Consistency rubric:
level_1: The mortar or its gray powder blend vanishes and reappears between shots; the water droplet appears in mid-air with no pipette tip above it; colored fog appears before the droplet has even touched the mixture; or the scene's brightness jumps sharply with no droplet-related cause.
level_2: The mortar's position or angle shifts between shots even though nothing moved it; the pipette drifts sideways while still releasing its droplet; the fog plume starts from a spot other than where the droplet landed and then relocates; or the powder blend visibly jumps or recoils the instant the droplet lands.
level_3: The mortar stays put in the frame; the pipette holds a steady vertical position; the droplet falls in a straight line from the tip to the mixture; the fog plume rises from a single point of origin; and the brightness and shadow cast by the mortar and pipette stay the same shade and direction from the first frame to the last.
level_4: Everything in score 3 holds AND the pipette tip stays directly above the center of the blend throughout; the rising fog column stays aligned above the exact contact point rather than drifting sideways; and the mortar's rim and bowl keep the same size and shape (no stretching, squeezing, or warping) across the sequence.
level_5: Everything in score 4 holds AND the droplet's fall visibly speeds up as it descends rather than moving at a constant or floating speed; the fog column grows and deepens in tint gradually rather than snapping into existence at full size; the mortar and blend stay at a consistent depth relative to the background with no swimming or sliding; and no frame is skipped or repeated in a way that breaks the motion.