Domain: Engineering — Food and Bioprocess Engineering
Target concept: Determination of Magnesium in Food (Magneson Reagent Method)

Video generation prompt: Take 2 mL of the porphyra extract into a test tube, add sodium hydroxide solution to adjust the pH to greater than 10, and then add the magnesium reagent (Magneson reagent).

Evaluation guide:
(i) Target concept: Alkaline-dependent chromogenic complex formation between Mg²⁺ and Magneson dye.
Minimum mechanism: Porphyra extract must contain bioavailable Mg²⁺; NaOH must raise pH above 10 to deprotonate Magneson and enable chelation; Magneson must be added after alkalinization to trigger the specific blue complex.
(ii)Storyline: [Frame 0–2] Test tube with ~2 mL amber-brown porphyra extract visible; [Frame 3–5] Clear NaOH solution dispensed into tube: liquid level rises, no immediate color change; [Frame 6–8] Pale yellow/colorless Magneson reagent dispensed: mixing occurs; [Frame 9–10] Uniform blue coloration or suspended blue precipitate appears exclusively after Magneson addition and only when NaOH was previously added; entire sequence viewed frontally, fixed focal plane, no camera motion.

Manual:
Experimental Procedure
1. Place 2 mL porphyra extract into a clean test tube.
2. Add sodium hydroxide solution dropwise until alkaline (pH >10).
3. Add Magneson reagent.
Observation of Experimental Phenomena
A distinct blue coloration or fine blue precipitate forms immediately after Magneson addition under alkaline conditions.
Summary of Experimental Principles
Magneson reagent forms a blue chelate complex with Mg²⁺ ions only in strongly alkaline medium (pH >10); this selective color reaction enables qualitative detection of magnesium in biological extracts.

Prompt Grounding rubric:
level_1: None of the three core items (the test tube, the porphyra extract, and the Magneson reagent) appear in the video; no pH-adjustment action (sodium hydroxide addition) is shown.
level_2: The test tube appears, but the porphyra extract or the Magneson reagent is missing from the video, or the sodium hydroxide addition is never shown, or Magneson is added before the sodium hydroxide (wrong order).
level_3: All three items appear (the test tube, the porphyra extract inside it, and the Magneson reagent), and the sequence follows the correct order: extract first, sodium hydroxide second, Magneson third; no reagent teleports into the tube or swaps identity with another reagent.
level_4: Before Magneson is added, the porphyra extract and the sodium hydroxide are visibly two distinct liquids being combined in the same tube rather than pre-mixed off-screen; the Magneson reagent is a separate liquid added only after the sodium hydroxide, from a visibly different container than the NaOH bottle; every addition goes into the same test tube, with no second tube substituted partway through.
level_5: The test tube and all three reagent containers keep the same labels and appearance from the first time they appear to the last: the NaOH bottle is never confused with the Magneson bottle or vice versa; the extract is never replaced mid-video by a different-looking liquid; the tube's orientation (upright, same side facing camera) stays the same across the pipetting, NaOH-dispensing, and Magneson-dispensing steps.

Scientific and Causal Correctness rubric:
level_1: No blue color or blue precipitate ever appears in the tube; the final liquid stays colorless, yellow, green, red, or brown regardless of what's been added, none of which matches the magnesium–Magneson blue complex.
level_2: Some color change happens, but not the right one: the liquid turns purple, orange, or black instead of blue; or a blue color appears before the sodium hydroxide has been added; or a precipitate forms but it's white or gray and grainy rather than fine and blue.
level_3: A blue color or a suspended fine blue precipitate appears in the tube, and it only appears after both the sodium hydroxide and the Magneson reagent have gone in, not before Magneson is added, and not if the NaOH step is skipped or never shown; the color reads as clearly blue, not violet, cyan, or teal, and any precipitate stays as fine suspended particles rather than a chunky layer at the bottom.
level_4: The blue color spreads evenly through the liquid or forms an evenly fine-dispersed precipitate, rather than streaking or separating into distinct color layers; no other color (red, brown tint, or unrelated cloudiness) appears alongside the blue; if a precipitate forms, it's still visibly suspended by the end of the clip rather than having already settled to the bottom.
level_5: The blue color or precipitate visibly begins only once the Magneson has been mixed into the already-alkaline extract, never during the NaOH addition by itself, and without an unexplained delay after Magneson goes in; once blue appears, its intensity stays steady for the rest of the clip (no fading or deepening); no separate ring of color forms at the liquid surface or on the tube's inner wall suggesting a coating artifact rather than a true bulk reaction.

Spatiotemporal Consistency rubric:
level_1: The test tube is present one moment and gone from the shot the next without any hand moving it out of frame; the porphyra extract or Magneson reagent shifts from one container to another with no pouring or pipetting motion shown; the room brightness swings from bright to dark within a single cut; the tube spins more than a quarter turn with no hand touching it; the liquid's fill line changes abruptly between two frames rather than rising or falling gradually.
level_2: One clear flaw appears: the pipette tip vanishes momentarily while still inside the tube; a brief flash or dropped frame hides part of an addition step; the liquid's fill level looks different from one frame to the next with no visible pour causing it; the shadow under the hand disconnects from the hand while a reagent is being added; the tube rocks or shakes hard with nothing touching it.
level_3: The test tube stays in view and intact throughout, with no clipping or warping of its outline; the camera viewpoint doesn't change; a hand enters and exits the frame the same way each time it adds a reagent; the liquid volume in the tube after each addition looks consistent with what was poured in: no sudden overflow and no liquid vanishing between additions.
level_4: The pipetting hand moves at a steady, natural speed rather than snapping between positions; each poured stream of liquid flows straight downward into the tube rather than appearing to hover or splash backward out of it; the pipette tip never appears to pass through the glass wall of the tube; the reagents and tube stay in sharp focus during each addition, without a sudden blur washing out their color.
level_5: The test tube stays upright and doesn't drift sideways or tip at any point; its round cross-section still looks round from every angle shown, without stretching into an oval as the camera view is held; no colored fringing or lens flare washes out the liquid's true color at any frame; no duplicate or mirrored copy of the tube or hand appears from a reflection; the curve of the liquid's meniscus and its height against the tube's markings stay consistent with the amount poured in throughout.