Domain: Engineering — Food and Bioprocess Engineering
Target concept: Determination of Iron in Food (O-Phenanthroline Spectrophotometric Method)

Video generation prompt: Take 2 mL of spinach extract into a test tube, and add hydroxylamine hydrochloride and o-phenanthroline solution.

Evaluation guide:
(i) Target concept: Formation of Fe²⁺–o-phenanthroline complex in spinach extract requires sequential chemical reduction then chelation.
Minimum mechanism: Spinach extract must contain bioavailable iron (as Fe³⁺); hydroxylamine must be added before o-phenanthroline to enable reduction; o-phenanthroline must contact reduced iron to form the chromophore; complex formation is rapid, homogeneous, and stoichiometrically dependent on correct reagent order and identity.
(ii)Storyline: [Frame 0–2] Static shot: test tube with green spinach extract centered; two reagent bottles (amber-labeled, clear-labeled) adjacent on bench. [Frame 2–4] Pipette tip enters from right, draws from the amber-labeled bottle and dispenses a colorless liquid into test tube → no color change. [Frame 4–6] Same pipette (or second identical pipette) enters from right, draws from the clear-labeled bottle and dispenses a colorless liquid → immediate, full red-orange development. [Frame 6–10] Stable hold: uniform red-orange solution fills test tube; all objects retain fixed spatial relationships; lighting and focus unchanged; no occlusion of labels, meniscus, or color field.

Manual:
Experimental Procedure
1. Place 2 mL spinach extract (green liquid) into a clean test tube.
2. Add 1 mL hydroxylamine hydrochloride solution (colorless liquid, stored in an amber/light-protective bottle) using a dropper.
3. Add 1 mL o-phenanthroline solution (colorless liquid) using a dropper.
Observation of Experimental Phenomena
Green spinach extract becomes uniformly red-orange after o-phenanthroline addition; no precipitate or phase separation occurs.
Summary of Experimental Principles
Hydroxylamine reduces Fe³⁺ to Fe²⁺; o-phenanthroline forms a stable, colored red-orange complex with Fe²⁺, enabling spectrophotometric quantification.

Prompt Grounding rubric:
level_1: No test tube present; no spinach extract visible; no hydroxylamine hydrochloride solution or o-phenanthroline solution shown; no liquid transfer action; no reagent addition sequence depicted.
level_2: Test tube is present but empty; at least one reagent bottle (labeled or visually distinct) appears, but no liquid is transferred into the test tube; spinach extract is absent or unidentifiable as plant-derived green liquid.
level_3: Test tube is present and contains approximately 2 mL of green liquid (spinach extract); two labeled reagent bottles (hydroxylamine hydrochloride and o-phenanthroline) are visible in frame; liquid from one bottle is dispensed into the test tube, but the second reagent addition is missing or occluded.
level_4: Test tube contains green liquid; both reagent bottles are visibly labeled or distinguishable (the hydroxylamine hydrochloride bottle is amber/light-protective glass and the o-phenanthroline bottle is clear glass, and the liquid dispensed from each is colorless); liquid from the first bottle is added to the test tube, then liquid from the second bottle is added sequentially; the test tube and both bottles stay in the same relative arrangement on the bench between the two additions; no bottle or dropper appears or disappears from the frame unexpectedly.
level_5: Test tube is centered and stable; green spinach extract occupies about two-thirds of the test tube's height; hydroxylamine hydrochloride solution (a colorless liquid dispensed from a labeled amber/light-protective bottle) is added first, followed immediately by o-phenanthroline solution (a colorless liquid from a labeled clear bottle); both additions occur via dropper/pipette tip entering frame from the same side; the test tube and bottles never shift position, no label is ever blocked from view, and no bottle is swapped for a different container at any point.

Scientific and Causal Correctness rubric:
level_1: The spinach extract's color never turns red-orange despite both reagents being added; the solution stays green or turns colorless instead; the reagents are added in the wrong order (o-phenanthroline before hydroxylamine hydrochloride) or at the same time; the starting liquid is not green as spinach extract should be.
level_2: Green spinach extract is present; only one reagent is added and no color change follows it, or the final solution turns brown or yellow rather than red-orange; the two reagent bottles cannot be told apart (e.g., both appear as identical unlabeled clear containers).
level_3: Green spinach extract is present; hydroxylamine hydrochloride is added first (a colorless liquid visibly enters the test tube), then o-phenanthroline is added second (a colorless liquid visibly enters); the final solution develops a uniform red-orange hue in the test tube, but the color appears only after a noticeable delay (3 or more seconds after the second addition) or develops unevenly, with patches of red-orange mixed with green.
level_4: Green spinach extract is present; hydroxylamine hydrochloride is added first and the solution stays green; o-phenanthroline is added second and a red-orange color appears uniformly throughout the solution within about one second of that addition; no brown precipitate, cloudiness, or phase separation appears; the color change matches the expected Fe²⁺–o-phenanthroline complex formation.
level_5: Green spinach extract is present; hydroxylamine hydrochloride is added first and the extract stays green with no visible color change; o-phenanthroline is added second and the solution turns red-orange instantly and uniformly across its entire volume; no green streaks remain near the surface or edges; the resulting color is a saturated red-orange (not pink, not rust-brown); this red-orange color stays unchanged through the end of the clip.

Spatiotemporal Consistency rubric:
level_1: The test tube is present in some frames and completely absent in others with no hand removing it; the hydroxylamine hydrochloride bottle or the o-phenanthroline bottle appears in a different spot on the bench between shots with no hand carrying it there; liquid appears to spurt out beyond the test tube into empty space; the room lighting switches abruptly from daylight-like to warm/tungsten mid-clip; the test tube's tilt changes by more than roughly a quarter turn with no hand visibly touching it; the bench background changes to a different scene with no transition.
level_2: The test tube stays visible but its on-screen position shifts sideways or vertically by more than about half its own width between the two additions; the pipette enters from the right for the first addition and from the left for the second (or vice versa); the shadow cast by the test tube or bottles points in a noticeably different direction after a reagent addition than before it; one of the two reagent bottles is no longer visible right after its liquid is dispensed and only reappears later; the room lighting visibly brightens or dims during the pouring action.
level_3: The test tube stays in the same on-screen spot throughout; the hydroxylamine hydrochloride bottle and the o-phenanthroline bottle stay visible in their original left-right arrangement on the bench without swapping places; the pipette enters from the same side of the frame for both additions; the poured liquid streams continuously into the test tube without stuttering, freezing, or jump-cutting; the direction and strength of the shadows on the bench look the same before and after each addition; the test tube and bottles keep their shape with no visible warping.
level_4: All conditions from 3-score are met AND the test tube keeps the same orientation and apparent size across the whole clip; both reagent bottles stay fully in view and unmoved on the bench; the pipette tip enters at the same angle and bench position for both the hydroxylamine and the o-phenanthroline addition; the poured liquid stream keeps a consistent thickness with no visible stutter; there is no stretching, shearing, or rolling-shutter-like warping of the test tube or bottles; the bench and test tube do not appear to shift relative to each other when the hand moves.
level_5: All conditions from 4-score are met AND the test tube's on-screen position stays visibly fixed to within a small fraction of its own width from the first frame to the last; both reagent bottles keep the same on-screen position and apparent size throughout; the pipette follows the same visible path into the test tube for both additions; the poured liquid stream stays a single continuous, unbroken column fully inside the test tube; the brightness, direction, and warm/cool tone of the lighting look unchanged across the whole clip; there is no visible double-image or ghosting of the test tube or bottles at any point.