Domain: Engineering — Food and Bioprocess Engineering
Target concept: Determination of Sodium in Food: Zinc Uranyl Acetate Method

Video generation prompt: Take 2 mL of the pickled vegetable extract into a test tube and add zinc uranyl acetate solution.

Evaluation guide:
(i) Target concept: Visual verification of sodium detection via formation of a specific yellow precipitate upon reagent addition.
Minimum mechanism: Zinc uranyl acetate must be added *to* an existing aqueous sodium-containing extract; precipitation requires direct molecular contact and cannot occur spontaneously, pre-addition, or without sodium.
(ii)Storyline: Frame 1: Static shot showing test tube with ~2 mL clear liquid (labeled/identified as pickled vegetable extract). Frame 2: Zinc uranyl acetate solution container and functional dropper enter frame from consistent direction. Frame 3: Dropper tip aligns vertically over tube mouth and begins dispensing. Frame 4: First drops contact extract surface → immediate localized yellow particle nucleation at interface. Frame 5: Particles grow in number, remain yellow, and begin gravitational settling while supernatant stays colorless and clear. All frames maintain fixed viewpoint, consistent lighting, and unoccluded view of tube interior.

Manual:
Experimental Procedure
1. Place 2 mL pickled vegetable extract in a clean test tube.
2. Using a dropper, add zinc uranyl acetate solution dropwise into the test tube.
Observation of Experimental Phenomena
A bright yellow crystalline precipitate forms immediately upon addition and settles gradually.
Summary of Experimental Principles
Sodium ions in the extract react with zinc uranyl acetate to form insoluble sodium zinc uranyl acetate, a characteristic yellow precipitate — confirming sodium presence.

Prompt Grounding rubric:
level_1: No test tube is visible; there is no clear liquid representing the pickled vegetable extract; no zinc uranyl acetate bottle or dropper appears; no transfer of any liquid into a test tube is shown.
level_2: A test tube stands upright but is empty; a zinc uranyl acetate bottle is visible but nothing is ever dispensed from it; nothing indicates roughly 2 mL of liquid was measured out, and no dropper or pipette touches the tube.
level_3: A test tube holds a clear liquid meant to be the pickled vegetable extract; a zinc uranyl acetate bottle and a dropper or pipette are both present; the dropper reaches the tube's opening and releases liquid into it; however, nothing confirms the liquid already in the tube is specifically the extract rather than some other clear liquid, and nothing shows it was measured to about 2 mL beforehand.
level_4: All 3-point conditions hold, and the liquid already in the tube is identifiable as the pickled vegetable extract (by a visible label, or by being shown poured from a labeled extract source) before the reagent is added; the dropper delivers liquid from a clearly labeled zinc uranyl acetate bottle straight into the tube; no unrelated equipment (extra beakers, stir bars, or a gloved hand) blocks the view of the tube.
level_5: All 4-point conditions hold, and the extract is clearly identifiable as the pickled vegetable extract (either by a visible label on the tube or by being shown poured from a labeled extract source) before about 2 mL sits in the tube; the zinc uranyl acetate solution is dispensed from a labeled bottle via a dropper or pipette while still actively entering the tube, not just before or after the motion; nothing else in frame interrupts the clear view of this single addition step.

Scientific and Causal Correctness rubric:
level_1: No color change occurs anywhere in the test tube; no precipitate of any kind forms; the liquid stays a single transparent, uniform phase from before to after the reagent is added.
level_2: A color shift appears (e.g., yellowish, brownish, or pink) but no discrete precipitate ever forms; or solid particles appear without any preceding color change; or particles are already visible before the zinc uranyl acetate reagent touches the extract; or the precipitate collects only as a film on the tube wall rather than as particles through the liquid.
level_3: A yellow precipitate forms only after the zinc uranyl acetate solution contacts the extract; the precipitate appears as particles suspended in or settling through the liquid, not only on the tube wall; the liquid above the precipitate shows no separate color change; however, the precipitate looks like a smooth blob, mist, or gel rather than a collection of small, grainy particles.
level_4: All 3-point conditions hold, and the yellow precipitate forms as fine, grain-like particles spread through the lower liquid within a couple of seconds of the reagent's contact, not before addition and not after a long unexplained delay; the liquid above the settling particles stays clear and colorless; no unrelated color change (such as browning or overall clouding) appears elsewhere in the tube.
level_5: All 4-point conditions hold, and the yellow precipitate first appears right where the two liquids meet and then spreads through the lower part of the tube as fine, evenly sized grains rather than clumps larger than about twice the size of a typical particle; the particles settle steadily toward the bottom under gravity without becoming re-suspended or stirred up by turbulence; the color stays a consistent yellow with no drift toward orange or red, and the liquid above the settling particles stays fully clear and colorless for the rest of the clip.

Spatiotemporal Consistency rubric:
level_1: The test tube itself vanishes or reappears partway through the clip; the liquid level inside it jumps up or down between frames with no pouring action shown; the zinc uranyl acetate bottle or dropper jumps to a new position with no travel path; the scene goes dark or flashes brightly for no reason; the tube tilts more than about 30 degrees with nothing shown holding it there.
level_2: The test tube rocks back and forth by more than its own width; the dropper's approach toward the tube mouth is jerky, freezing and then jumping ahead rather than moving smoothly; the yellow precipitate appears through the whole liquid column all at once instead of building up gradually; small ripples on the liquid surface freeze in place for a moment and then resume moving.
level_3: The test tube stays in the same place and orientation throughout; the dropper moves toward and away from the tube mouth smoothly, without sudden jumps; the yellow precipitate spreads outward from the point of contact in a gradual, connected progression rather than popping up in disconnected patches; no object clips through another, warps, or flips in perspective.
level_4: All 3-point conditions hold, and the test tube, dropper, and reagent bottle keep the same relative arrangement across the clip: tube centered, dropper approaching from directly above, bottle held or resting to one side; the dropper's motion is smooth and physically sensible (descending, pausing while liquid is released, then withdrawing); the precipitate forms only where the reagent has actually touched the liquid and spreads downward under gravity rather than sideways or upward.
level_5: All 4-point conditions hold, and the test tube's position, tilt, and apparent size stay constant across the whole clip; the dropper tip keeps a steady distance and vertical alignment above the tube mouth through its approach, contact, and withdrawal; the yellow precipitate originates only at the contact point and descends in roughly straight paths that thicken over time, with no shaking, warping, or perspective shift between the base and mouth of the tube.