Domain: Natural Science — Environmental Science
Target concept: Determination of Soil Phosphorus Content (Molybdenum Blue Colorimetric Method)

Video generation prompt: Pipette 2 mL of the phosphorus-containing soil digest into a test tube, add 3 drops of ammonium molybdate-ascorbic acid reagent, and heat in a boiling water bath for 1 minute.

Evaluation guide:
(i) Target concept: Colorimetric detection of orthophosphate via formation of molybdenum blue complex under heat-activated reduction.
Minimum mechanism: Phosphate must be present in digest; reagent must contain both ammonium molybdate (oxidant) and ascorbic acid (reductant); acidic pH must be maintained; heating must supply activation energy for reduction step; blue chromophore formation requires molecular assembly and electron transfer: no blue without all components and thermal trigger.
(ii)Storyline: [Frame 0–2] Pipette draws and delivers 2 mL digest into stationary vertical test tube → [Frame 3–4] Dropper approaches, pauses, releases 3 distinct spherical drops into tube interior → [Frame 5–6] Tube lifted and lowered smoothly into boiling water bath (steam/bubbles visible on bath surface) → [Frame 7] Liquid remains unchanged (colorless/yellow) during first 0.5 s of immersion → [Frame 8] Blue color emerges homogeneously across entire liquid column → [Frame 9] Blue intensifies uniformly with no fading, streaking, or precipitation; viewpoint remains fixed frontal close-up showing test tube center, meniscus, and bath interface; no occlusion of liquid column at any point.

Manual:
Experimental Procedure
1. Pipette 2 mL of phosphorus-containing soil digest into a clean test tube.
2. Add exactly 3 drops of ammonium molybdate-ascorbic acid reagent to the test tube.
3. Place test tube in boiling water bath for heating.
Observation of Experimental Phenomena
The solution turns uniformly blue only after heating begins; blue color is stable, transparent, and fully saturates the liquid volume.
Summary of Experimental Principles
Phosphate reacts with ammonium molybdate under acidic conditions to form phosphomolybdic acid, which is reduced by ascorbic acid to molybdenum blue — a stable, intensely blue-colored complex whose absorbance is proportional to phosphorus concentration.

Prompt Grounding rubric:
level_1: No test tube is visible; no pipette appears; no reagent dropper or bottle is shown; no boiling water bath is present; none of the three steps (pipetting the digest, adding reagent drops, heating) take place.
level_2: At least one required item appears (test tube, pipette, dropper, or water bath) but no step is carried out correctly: e.g., the pipette hovers near the tube without dispensing liquid, the dropper is squeezed with no drop leaving the tip, or the water bath sits without steam or bubbling to show it is boiling.
level_3: The test tube, pipette, and reagent dropper are all shown; at least two of the three steps happen in a sensible order (liquid delivered into the tube by pipette, drops added by dropper, tube placed into a visibly boiling bath), but one step's timing is off (e.g., drops appear before the digest is pipetted in, or the tube goes into the bath before the drops are added).
level_4: All three items appear and all three steps occur in the order given in the prompt: the pipette delivers the 2 mL digest first, the dropper then adds drops into that same tube, and the tube is fully lowered into the visibly boiling water bath last, with no step skipped, no step reordered, and the same pipette and same dropper used throughout (not swapped for different tools mid-sequence).
level_5: All score 4 conditions hold AND every tool keeps a consistent look throughout its use: the pipette's shape and the dropper's shape stay the same from first appearance to last, the test tube shows no cracking, bending, or distorted reflections, and the water bath keeps visibly boiling (steam plus surface agitation) for the entire time the tube is immersed, with no gap where any of these elements briefly disappears from view.

Scientific and Causal Correctness rubric:
level_1: The liquid in the test tube never changes color at any point; it stays colorless or its original pale tint throughout, with no visible effect from either the reagent drops or the heating step.
level_2: The liquid turns a color other than blue after the reagent or heating (e.g., yellow, green, or brown); or a blue color appears before the tube is heated; or blue appears before the reagent drops are added; or a blue tint flashes briefly and then disappears completely rather than settling into a stable color.
level_3: The liquid starts colorless or pale, and only turns blue after both the three reagent drops have been added and the tube has gone into the boiling bath; the blue color is visible during heating and persists for at least 1 second while the tube remains immersed in the bath, but it is uneven: patchy, streaked, or stronger in one part of the liquid column than another.
level_4: The liquid stays colorless/pale before the reagent is added, remains unchanged right after the drops go in (before heating starts), and only turns blue during the boiling-bath immersion; the blue fills the entire liquid column evenly with no streaks or patches, and it holds steady for at least 1 second while the tube remains immersed, rather than fading back toward colorless right away.
level_5: All score 4 conditions hold AND the blue shade is a deep, saturated molybdenum-blue (not tinted green or yellow, not washed-out or hazy), and the liquid stays clear with no cloudiness, floating particles, or separation into layers; the color's appearance stays the same as the tube is handled, with no part of the liquid reading a different shade than the rest.

Spatiotemporal Consistency rubric:
level_1: The test tube's position or appearance changes abruptly between frames with no camera motion to explain it; the pipette seems to jump from off-screen to inside the tube with no visible path of travel; steam over the water bath appears or vanishes instantly rather than building or dissipating; the scene's lighting flips from bright to dark between adjacent frames; or the tube appears rotated by more than 90 degrees with no in-between frames showing the turn.
level_2: The pipette tip reaches the test tube with no visible approach motion; the dropper hovers above the tube and then instantly touches the liquid with no downward motion shown; the tube enters the water bath with no hand or supporting motion visible; steam appears in a single frame and then is simply gone; or background elements (bath, bench) flicker or warp between frames.
level_3: The test tube stays centered or in a stable position in the frame; the pipette and dropper always enter from the same side of the frame; the water bath stays in the same part of the frame throughout; there are no hard cuts, but small blips remain, such as a slight wobble of the tube from hand tremor, a brief moment where the dropper tip is hidden as a drop releases, or a passing shadow crossing the tube wall.
level_4: The pipette's approach to the tube is a smooth, continuous downward path; the dropper descends, pauses, and releases each of the three drops with a visible break at the tip and a visible fall to the liquid; the tube's lowering into the bath is one unbroken downward motion ending in full immersion; steam rises continuously in the same direction and density; no object suddenly changes size, rotates unnaturally, or deforms.
level_5: All score 4 conditions hold AND the test tube keeps the same proportions, angle, and edge sharpness in every frame; the pipette and dropper keep a constant thickness and stay aligned with the tube at every step; the background and the tube never drift relative to each other; the tube's circular opening never warps into an oval or other distorted shape; and no frame shows blur on a fast-moving element (like a falling drop) paired with a perfectly sharp background.