Domain: Natural Science — Chemistry
Target concept: Precipitate formation in the reaction of hydroxylamine with aldehydes

Video generation prompt: Add 1 mL of 0.1 M benzaldehyde solution to 2 mL of 0.1 M hydroxylamine hydrochloride solution and 1 mL of 10% NaOH solution, and allow the mixture to stand at room temperature for 5 minutes.

Evaluation guide:
(i) Target concept: Precipitation of benzaldehyde oxime via nucleophilic addition-elimination under alkaline conditions.
Minimum mechanism: NaOH first neutralizes the hydroxylamine hydrochloride, freeing neutral hydroxylamine (NH₂OH) from its protonated ammonium form; the nitrogen lone pair of the freed hydroxylamine then performs nucleophilic addition at the carbonyl carbon of benzaldehyde, forming a carbinolamine intermediate that dehydrates to give the C=N-OH oxime linkage; the resulting benzaldehyde oxime is only sparingly soluble in water, so it crystallizes out of solution as a precipitate.
(ii) Storyline: Frame 1–2: Three labeled reagent containers visible side-by-side (hydroxylamine HCl, NaOH, benzaldehyde). Frame 3–4: Hydroxylamine HCl and NaOH combined in a test tube (no precipitate yet). Frame 5: Benzaldehyde added, followed immediately by one brief gentle swirl to mix. Frame 6–10: Test tube stationary, no further motion; precipitate emerges gradually (frames 7–10 show progressive increase in white particulates at bottom/mid-layer), supernatant remains optically clear. All under a fixed frontal view with no occlusion of the tube.

Manual:
Experimental Procedure
1. Place 2 mL hydroxylamine hydrochloride solution and 1 mL NaOH solution in a clean test tube.
2. Add 1 mL benzaldehyde solution to the test tube.
3. Gently swirl once, then set aside motionless for 5 minutes.
Observation of Experimental Phenomena
A white or off-white precipitate forms in the test tube and remains suspended/settled; the supernatant stays clear and colorless.
Summary of Experimental Principles
Benzaldehyde reacts with hydroxylamine under basic conditions to form benzaldehyde oxime, which is sparingly soluble in water and precipitates as a crystalline solid.

Prompt Grounding rubric:
level_1: No benzaldehyde solution, hydroxylamine hydrochloride solution, or NaOH solution is shown; no reagent container appears; no liquid-transfer action occurs; no standing period is depicted.
level_2: At least one reagent container appears, but the three solutions (benzaldehyde, hydroxylamine hydrochloride, NaOH) cannot be told apart by label, color cue, or context; no pouring/combining sequence is shown; nothing suggests the mixture is left to stand for about 5 minutes.
level_3: All three reagents appear as labeled or contextually identifiable clear-liquid containers: benzaldehyde solution, hydroxylamine hydrochloride solution, NaOH solution; the liquids are combined into one test tube in any order; the combined test tube is shown, but the video gives no clear sense of a roughly 5-minute standing period afterward.
level_4: All three reagents are correctly labeled/identifiable and combined in an order matching the prompt: hydroxylamine hydrochloride and NaOH combined first, then benzaldehyde added; the resulting mixture sits in a single test tube for what reads as roughly 5 minutes; aside from one brief swirl right after the benzaldehyde is added (matching the manual's mixing step), the test tube is not picked up, shaken, heated, or otherwise disturbed.
level_5: All three reagents are correctly labeled/identifiable, and their relative liquid volumes are visually distinguishable: the combined hydroxylamine hydrochloride + NaOH portion clearly holds a noticeably greater liquid height than the benzaldehyde portion added to it (consistent with the prompt's 2 mL + 1 mL vs. 1 mL ratio); addition proceeds in strict order (hydroxylamine HCl and NaOH mixed first, benzaldehyde added second); after the single brief swirl to mix, the test tube remains stationary in one continuous shot for the full roughly 5-minute standing period, with the label never occluded and no viewpoint cut or camera-angle change.

Scientific and Causal Correctness rubric:
level_1: No solid forms in the test tube; the combined benzaldehyde/hydroxylamine/NaOH mixture stays a single clear liquid for the full 5 minutes, with nothing in the video connecting the reagent combination to any new solid appearing.
level_2: A solid does appear, but it is inconsistent with a benzaldehyde oxime precipitate: e.g., it is distinctly colored (yellow, orange, or dark) rather than white/off-white, or it appears in the original benzaldehyde or hydroxylamine vial before the reagents are combined, or a solid forms and then fully redissolves during the standing period.
level_3: A white or off-white solid appears in the test tube only after benzaldehyde, hydroxylamine hydrochloride, and NaOH have all been combined; once formed it stays put and does not redissolve; no solid is visible before the three reagents are fully mixed.
level_4: The white/off-white solid forms only in the combined test tube (never in a separate vial) and, once it appears, persists without dissolving for the rest of the 5-minute standing period; the liquid above the solid stays clear rather than yellowing or browning; there is no bubbling, fizzing, or visible convection current that would suggest a gas-releasing or heat-driven reaction instead of a simple precipitation.
level_5: The white/off-white solid appears only after full combination and its amount visibly builds up gradually rather than appearing all at once, consistent with oxime crystallization; it settles as discrete granular/crystalline particles rather than an oily film or gel-like mass; the supernatant liquid stays clear and colorless throughout, with no floating film, layering, or second liquid phase forming alongside the solid.

Spatiotemporal Consistency rubric:
level_1: The test tube's position or orientation changes abruptly between shots with no visible hand or motion causing it (e.g., it is suddenly on the opposite side of the frame, or tipped over then upright with no transition shown); the lighting abruptly changes character (e.g., bright to dark or the reverse) between shots with no visible cause; the test tube's shape visibly warps or distorts from one frame to the next; the liquid height inside the tube changes without any pouring action; or the precipitate is fully present in one frame with nothing building up beforehand.
level_2: A single clear spatiotemporal break occurs: e.g., the test tube's rotation changes by more than roughly a quarter turn between consecutive frames with no visible cause, the benzaldehyde portion's liquid height shrinks or grows without a corresponding pour, or two separately filmed segments are joined so the tube's angle or shadow doesn't match from one segment to the next.
level_3: The test tube stays in the same spot in the frame throughout, aside from the single brief swirl used to mix the reagents; the relative liquid-height split between the hydroxylamine/NaOH portion and the added benzaldehyde portion stays consistent with the combined volume once mixed (no unexplained rise or drop); the emerging precipitate is shown building up gradually across at least two consecutive frames rather than snapping into its final amount in one frame.
level_4: Beyond the one permitted swirl right after the benzaldehyde is added, the test tube's position, tilt, and apparent size in frame stay fixed for the rest of the video; the liquid's meniscus stays level (horizontal) at all times; the precipitate accumulates from the bottom of the tube upward in a steady, uninterrupted progression, without any frame where its amount or pattern flickers or reshuffles.
level_5: Aside from the single brief swirl immediately after the benzaldehyde is added, the test tube never shifts position, angle, or apparent distance from the camera for the rest of the roughly 5-minute standing period shown; the meniscus of the combined liquid stays flat and level throughout; the white/off-white precipitate's granular buildup is continuous and cumulative (once a cluster of particles appears it does not disappear, relocate, or reappear elsewhere in the tube), and its growth traces a single smooth progression from first appearance to the final amount shown.