Domain: Engineering — Food and Bioprocess Engineering
Target concept: Determination of Potassium in Food by Sodium Tetraphenylborate Method

Video generation prompt: Place 2 mL of banana extract into a test tube and add sodium tetraphenylborate solution.

Evaluation guide:
(i) Target concept: Visual confirmation of potassium-specific precipitation via sodium tetraphenylborate in food matrix.
Minimum mechanism: Banana extract must contain bioavailable K⁺; sodium tetraphenylborate must be aqueous and stable; reaction must occur in aqueous medium at room temperature; precipitate must be kinetically immediate and thermodynamically stable under observation timeframe.
(ii)Storyline: [Frame 0–2] Static shot: empty test tube centered, labeled reagent bottle adjacent. [Frame 3–5] Hand places banana extract: visible meniscus forms at ~2 mL level. [Frame 6–7] Dropper approaches surface; clear solution dispensed. [Frame 8] First contact: localized whitening at interface. [Frame 9–10] Precipitate nucleates, grows, and begins downward settling; fully visible, no occlusion, no lighting shift.

Manual:
Experimental Procedure
1. Place 2 mL of banana extract into a clean test tube.
2. Add sodium tetraphenylborate solution dropwise to the extract.
Observation of Experimental Phenomena
A white granular precipitate forms immediately upon contact and settles at the bottom of the test tube.
Summary of Experimental Principles
Potassium ions in banana extract react with sodium tetraphenylborate to form insoluble potassium tetraphenylborate, a characteristic white crystalline precipitate used for quantitative determination.

Prompt Grounding rubric:
level_1: No test tube present; no banana extract visible; no sodium tetraphenylborate solution container or dispensing action; no placement of 2 mL liquid into any container; completely unrelated scene.
level_2: A test tube is present and a liquid is poured, but the liquid is not clearly identifiable as banana extract (e.g., wrong color like blue or opaque white), and no sodium tetraphenylborate solution container or addition action is shown; quantity is unverifiable (no meniscus, no calibrated markings, no volume cue).
level_3: A clear test tube is present; a light-yellow to pale-brown transparent liquid (consistent with banana extract) is placed into it; volume appears approximately consistent with 2 mL (visible meniscus at ~1/3–1/2 height of standard 15 mL test tube); sodium tetraphenylborate solution is present in a separate labeled or recognizable reagent bottle, but no addition action occurs within video.
level_4: All elements from score 3 are present AND sodium tetraphenylborate solution is visibly dispensed (e.g., dropper tip enters frame, liquid stream contacts banana extract surface); both containers remain in same fixed viewpoint throughout; no substitution (e.g., water instead of reagent) or mislabeling (e.g., bottle labeled “NaCl”).
level_5: All elements from score 4 are present AND the banana extract is placed first (visible start of action), followed *sequentially* by addition of sodium tetraphenylborate solution (no overlap, no reverse order); both liquids are fully contained within the test tube during and after addition; test tube remains upright, stationary, and fully in-frame before/during/after both actions; no object occlusion, replacement, or duplication.

Scientific and Causal Correctness rubric:
level_1: No observable reaction or state change; liquids mix homogeneously with no precipitate; or precipitate forms but is wrong color (e.g., black, green, bright red) or wrong morphology (e.g., gelatinous, bubbly, floating film).
level_2: Precipitate appears, but its formation is temporally disconnected from addition (e.g., appears before reagent contact or >2 seconds after full addition); precipitate is present but inconsistent with potassium tetraphenylborate: not white, not granular, not settling at bottom, or fully dissolving immediately.
level_3: White granular precipitate appears *only after* sodium tetraphenylborate solution contacts banana extract; precipitate forms at liquid interface and begins settling downward; no color shift in supernatant (remains light-yellow/pale-brown); precipitate remains distinct from background and test tube walls.
level_4: All elements from score 3 are present AND precipitate formation is continuous and progressive (no abrupt “pop-in”, no flickering, no disappearance/reappearance); supernatant remains transparent (not cloudy or turbid beyond initial mixing); no secondary phenomena (e.g., effervescence, phase separation, color bleed).
level_5: All elements from score 4 are present AND precipitate is exclusively confined to the lower 1/3–1/2 of test tube post-settling; no suspended particles remain in upper 1/3 after 2 seconds of stillness; precipitate texture is uniformly fine-grained (not clumped, not fibrous); no discoloration of precipitate edges or halo effects; supernatant clarity matches pre-addition transparency except for settled mass.

Spatiotemporal Consistency rubric:
level_1: Test tube teleports between frames; sudden lighting shift (e.g., bright → dark mid-sequence); liquid jumps without motion path; container rotates >30° without visible hand support; structural break (e.g., test tube splits, bottom vanishes).
level_2: Minor discontinuity: brief cut or flash obscures action; one frame shows empty test tube, next shows filled, no visible pouring motion; dropper appears/disappears without entry/exit; shadow direction flips inconsistently across frames.
level_3: All objects maintain fixed spatial relationship: test tube centered, upright, unmoving; reagent bottle adjacent (left or right) and at consistent relative position; hand enters frame only once to place extract, then re-enters to add reagent; no contradictory limb positioning (e.g., hand enters left but reagent comes from right).
level_4: All elements from score 3 are present AND motion is physically plausible: liquid stream follows gravity-aligned trajectory; no acceleration inconsistencies (e.g., stream speeds up then stops abruptly); no interpenetration (e.g., dropper tip passes through liquid surface without resistance cue); lighting and shadow remain stable in intensity and direction.
level_5: All elements from score 4 are present AND every frame shows continuous, unoccluded visibility of: (a) banana extract meniscus pre-addition, (b) dropper tip approaching surface, (c) first contact point, (d) onset of precipitate at interface, (e) uninterrupted descent path of particles; no frame drop, no motion blur that obscures state change, no parallax jump between shots.