Domain: Natural Science — Chemistry
Target concept: The addition of sodium bisulfite to aldehydes, forming crystalline adducts

Video generation prompt: Stir the clarified aldehyde solution in a glass beaker, and add a sodium bisulfite aqueous solution. Then cool the mixture in an ice bath while continuing stirring.

Evaluation guide:
(i) Target concept: Nucleophilic addition of HSO3⁻ to carbonyl carbon of aldehyde, forming a charged sulfonate adduct that precipitates as a crystalline solid upon cooling.
Minimum mechanism: Aldehyde must be unhydrated and sterically unhindered at the carbonyl carbon (e.g., formaldehyde or acetaldehyde); NaHSO3 must be in aqueous form to provide free HSO3⁻ ions; cooling must reduce solubility to drive supersaturation and crystal nucleation; stirring must persist to distribute nuclei and prevent localized saturation.
(ii)Storyline: Frame 0–2: Static shot of glass beaker containing colorless aldehyde solution; stir rod enters frame and initiates continuous circular motion. Frame 3–4: Hand introduces dropper/pipette delivering colorless NaHSO3 solution into beaker; liquid stream visible entering solution, no splashing. Frame 5–6: Beaker is lifted and placed into ice bath (ice + water visible around beaker base); stirring continues uninterrupted. Frame 7–10: White crystalline particles emerge first near bottom/mid-solution, increase in number and size while stirring persists; no color change, no gas, no cloudiness; only discrete crystals against transparent liquid. Viewpoint remains fixed frontal close-up; all actions occur within single continuous take; no object leaves frame or becomes occluded.

Manual:
Experimental Procedure
1. Place clarified aldehyde solution in a transparent glass beaker.
2. Stir the solution continuously with a glass rod.
3. Add sodium bisulfite aqueous solution to the beaker while stirring.
4. Immediately place the beaker into an ice bath and continue stirring.
Observation of Experimental Phenomena
A white crystalline solid forms gradually in the stirred solution during cooling; the liquid remains colorless and transparent between crystals.
Summary of Experimental Principles
Aldehydes react with sodium bisulfite to form water-soluble crystalline bisulfite adducts (sodium sulfonate salts) that precipitate from the concentrated solution upon cooling due to reduced solubility; cooling promotes crystallization by driving the solution past the saturation point.

Prompt Grounding rubric:
level_1: No glass beaker is visible; no aldehyde solution is present; no sodium bisulfite solution is shown; no stirring occurs; no ice bath appears; none of the three procedural steps (stirring the aldehyde solution, adding the bisulfite solution, cooling while stirring) is depicted.
level_2: At least one object is present (the beaker or a solution) but no procedural action occurs (no stirring, no addition, no cooling), or only one step is shown with the wrong object (e.g., a solid powder is added instead of an aqueous solution), or the steps are missing or shown out of order.
level_3: The glass beaker, the clarified aldehyde solution, and the sodium bisulfite solution are all present, and all three actions occur (stirring the aldehyde solution, adding the bisulfite solution into the beaker, and cooling in an ice bath while stirring continues), but at least one ordering or placement error occurs (e.g., the ice bath appears only after crystals have formed, stirring stops during the addition, or the addition happens outside the beaker).
level_4: All conditions for score 3 hold, AND every object has the correct appearance (beaker clearly glass, both solutions colorless and clear, ice bath visibly containing ice and water), AND the three actions occur in the posted order (stir, then add, then cool while continuing to stir) AND all actions take place inside the same beaker with the ice bath surrounding its base and the stir rod staying inside it throughout.
level_5: All conditions for score 4 hold, AND the stirring motion continues without interruption across all three phases (before, during, and after the addition), AND the beaker stays in the same spot on the bench, AND the ice and water in the bath stay continuously visible with no fading in or out, AND the camera holds a single fixed framing with no cut, zoom, or repositioning, AND every object keeps a stable, consistent appearance throughout (no morphing or texture change).

Scientific and Causal Correctness rubric:
level_1: No scientifically plausible crystallization is shown: no crystals form at all, or a violent reaction, gas evolution, or color change occurs that is inconsistent with a bisulfite-aldehyde adduct, or a solid appears before the bisulfite is added or before cooling begins, or crystals appear only on the stir rod and never in the solution.
level_2: Crystals appear, but the causal order is wrong: they form before the bisulfite solution is added, or before cooling starts, or only after stirring has stopped; or the crystals are colored (yellow, orange, or red) instead of white; or an amorphous precipitate forms instead of distinct crystals; or the solution turns cloudy without ever producing crystals.
level_3: White crystals appear only after both the bisulfite has been added and cooling has begun, and only within the stirred solution; the liquid itself stays colorless with no gas bubbles, haze, or phase separation beyond the crystals, though the crystals may briefly dissolve again, form only on the beaker wall rather than suspended in the liquid, or lack a clearly granular shape.
level_4: All conditions for score 3 hold, AND the white crystals appear only after the addition is complete and cooling has begun, AND they stay suspended or settled in the solution while stirring continues, AND the liquid stays colorless and clear apart from the crystals, AND the crystals show a clearly grainy, faceted, or needle-like shape distinguishable from general cloudiness, AND no bubbling, layering, or unrelated cloudiness appears.
level_5: All conditions for score 4 hold, AND the amount of crystal visibly keeps increasing from first appearance through the end of the cooling phase, AND the crystals stay within the liquid rather than collecting only at the surface or on the stir rod tip, AND no crystal dissolves, clumps together, or breaks down once formed, AND the liquid between the crystals stays visibly clear with no haze, AND the crystal growth tracks with the visible cooling: no crystals form early or long after cooling starts.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal rupture: the beaker jumps between different positions in the frame with no motion shown; the stir rod disappears and reappears; the ice bath vanishes and then appears already full of ice; the scene's shadows swing to a completely different angle within a single cut; the liquid surface breaks into disconnected pieces; or several unexplained camera cuts interrupt the single take.
level_2: Moderate breaks: the stir rod visibly clips through the beaker wall; ice pieces in the bath shrink or grow unrealistically between frames; the liquid level jumps without a visible cause; the stirring pauses then resumes at a different speed or direction with no smooth transition; or the hand adding the bisulfite solution is completely hidden from view for more than a second.
level_3: Only minor, isolated inconsistencies remain: a brief flicker in the stir rod's visibility during fast motion, a slight wobble in the beaker's position while being stirred, a small unexplained shift in the ice-bath water level, or one momentary patch of cloudiness in the liquid that is not linked to crystal formation; nothing disappears outright, and stirring keeps its overall direction and continuity.
level_4: All conditions for score 3 hold, AND the beaker stays fixed in the frame, AND the stir rod stays fully visible inside the beaker at all times, AND the ice bath keeps a physically plausible ice-to-water boundary in the same region of frame, AND the stirring motion stays smooth and unbroken in direction and rhythm, AND the surface ripples move in a way that matches the visible stirring speed.
level_5: All conditions for score 4 hold, AND the stir rod moves at a steady, constant angular rate around a fixed pivot point at the rim, AND ripples spread outward from the stirring point and fade naturally rather than looping or repeating, AND small ice fragments in the bath detach and drift without any teleporting jumps, AND the clear liquid between the crystals stays visibly transparent with no added haze, AND no frame repeats, freezes, or stutters during the sequence.