Domain: Healthcare — Nutrition and Food Hygiene
Target concept: Formaldehyde Determination (Acetylacetone Colorimetric Method)

Video generation prompt: A test tube containing 10 mL of the sample extract with formaldehyde was treated with acetylacetone reagent and ammonium acetate solution using a pipette. The mixture was gently stirred and then placed in a water bath at approximately 60°C for several minutes. After removal, the tube was cooled and observed.

Evaluation guide:
(i) Target concept: Chromogenic detection of formaldehyde via the acetylacetone (Nash) condensation reaction, in which formaldehyde, acetylacetone, and ammonium acetate combine to form 3,5-diacetyl-1,4-dihydrolutidine, a yellow-orange chromophore that develops progressively while the mixture is held at ~60°C and is typically read once the tube has cooled to a stable temperature.
Minimum mechanism: Acetylacetone and ammonium acetate must both be added to the formaldehyde-containing sample; the mixture must be heated (~60°C, several minutes) to drive the condensation reaction, during which the yellow-orange color progressively appears and intensifies; cooling afterward brings the tube to a stable, easily observed temperature and lets the color finish stabilizing, but the liquid is not required to be colorless during heating; some visible color partway through the water-bath step is expected, not a defect.
(ii)Storyline: Frame 1–2: Pipette approaches tube and dispenses reagents into liquid → Frame 3–4: Pipette tip rotates gently inside tube, inducing visible liquid vortex → Frame 5–7: Tube is lowered into water bath, fully submerged, with steam rising steadily; the liquid begins taking on a faint yellow tinge partway through this heating step → Frame 8: Tube lifted vertically, water droplets visible on exterior, liquid already showing a visible yellow-orange tint → Frame 9–10: Tube placed upright on bench; the yellow-orange color continues to deepen and becomes uniform across the entire liquid column as it cools; all events occur from fixed frontal viewpoint with tube centered, no occlusion, no camera motion.

Manual:
Experimental Procedure
1. Pipette acetylacetone reagent and ammonium acetate solution into a test tube containing 10 mL sample extract.
2. Gently stir mixture with pipette tip.
3. Place tube in water bath at ~60°C for several minutes.
4. Remove tube and cool to room temperature.
Observation of Experimental Phenomena
A yellow-orange color begins appearing in the liquid during the water-bath heating step and becomes fully uniform and stable across the entire column as the tube cools to room temperature.
Summary of Experimental Principles
Formaldehyde reacts with acetylacetone under ammonium acetate catalysis (the Nash reaction) to form 3,5-diacetyl-1,4-dihydrolutidine, a yellow-orange chromophore. The color develops progressively during the ~60°C heating step itself and continues to stabilize as the tube cools, which is when it is typically read/observed.

Prompt Grounding rubric:
level_1: No test tube is visible; no pipette is present; no water bath apparatus is shown; no liquid appears in the tube; no stirring motion occurs; no cooling step is depicted; none of the objects or actions from the posted_prompt appear at all.
level_2: At least one object from the posted_prompt appears (e.g., a tube or pipette), but fewer than three of the four core objects (tube with liquid, pipette, water bath, cooling surface) are present; an action is attempted (e.g., a hand nears the tube) but the pipetting → stirring → water bath → cooling sequence is not shown correctly; critical steps are missing or out of order.
level_3: All core objects are present: a test tube containing liquid, a pipette, a water bath apparatus (a visibly heated container or a unit labeled near 60°C), and a cooling surface (bench or rack); pipetting, stirring, water-bath immersion, and cooling actions all occur; but at least one step is out of the correct spatial or temporal relationship (e.g., stirring happens before pipetting, or the tube is set on the cooling surface before ever entering the water bath).
level_4: All core objects are present and clearly identifiable by shape/function; the four key actions occur in the correct order: (1) pipette delivers reagent into the tube, (2) stirring is applied to the tube's contents, (3) the tube goes into the water bath, (4) the tube is removed and set on the cooling surface, with none omitted, duplicated, or out of place; one minor flaw may remain (e.g., the pipette tip doesn't clearly touch the liquid, the tube isn't fully submerged in the bath, or the stirring shows little visible liquid movement).
level_5: All core objects are present and unambiguous: a clear cylindrical test tube holding roughly 10 mL of liquid, a calibrated pipette delivering reagent into the tube's mouth, a visible gentle circular stirring motion that keeps the liquid turning, the tube fully submerged in the water bath with visible steam or condensation on its exterior, then the tube fully removed and set upright on a room-temperature surface without wobbling; every action starts and finishes on screen with no cut or jump between steps, and all objects stay in consistent relative positions throughout.

Scientific and Causal Correctness rubric:
level_1: The liquid stays colorless (or only very faintly tinted) for the entire sequence, including after cooling; no yellow-orange hue ever becomes visible; nothing in the video links the heating step to any color change.
level_2: A color change occurs, but the hue is wrong (e.g., blue, purple, green, or deep brown rather than yellow-orange); or a strong yellow-orange color is already present before the reagents have even been mixed into the tube; or the liquid's color has no visible connection to the heating step at all (e.g., it flickers on and off at random points unrelated to the water bath).
level_3: A yellow-orange tint becomes visible sometime while the tube is in the water bath or shortly after it is lifted out, and the color spreads to cover the full liquid column by the time cooling finishes; no other hues (blue, purple, green, pink) or turbidity appear at any point; the color may look somewhat faint, patchy, or uneven while still developing.
level_4: Everything in score 3 holds, and the yellow-orange color is visibly present and already noticeable before the tube is removed from the water bath (i.e., some color shows during heating, not only after); by the end of cooling the color is uniform, opaque, and fully saturated across the entire liquid column; no bubbles, precipitate, layering, or fading interrupt the color's development.
level_5: Everything in score 4 holds, and the color's intensity increases steadily from first appearance in the bath through to the stabilized post-cooling result, without flickering, fading, or reversing at any point; the final color is an unambiguous, vivid yellow-orange (clearly not pale yellow, brown, or amber) that persists unchanged once cooling is complete; no coloration of any kind is visible before the reagents have been mixed into the tube.

Spatiotemporal Consistency rubric:
level_1: The test tube, pipette, or water bath vanishes or is suddenly replaced between frames with no visible motion causing it; the tube or pipette jumps to a new position instantaneously rather than being carried there; the room lighting swings from bright to dark (or vice versa) between adjacent frames; steam from the water bath appears or vanishes with no gradual buildup or dissipation; the stirring motion suddenly reverses direction or jerks in an unnatural way; or the clip cuts to a different shot or camera setup mid-sequence.
level_2: The tube visibly changes its tilt or position with no hand or tool touching it; the pipette tip appears to move on its own, detached from the hand holding it; the liquid's fill level changes without any addition, removal, or spill shown; the steam or condensation pattern around the water bath flickers on and off inconsistently; the stirring motion starts or stops abruptly with no slowing down; two or more of these problems occur together.
level_3: A brief, isolated jitter appears in the tube's position while it is being stirred; the tube is very briefly and only partially blocked from view while being moved to the water bath; a faint, momentary shift in the shadow on the bench appears during cooling; one instance of the pipette relocating without a visible path between its start and end point; none of these persist, and there is no vanishing, teleporting, or structural break at any point.
level_4: Everything in score 3 holds, and in addition: the tube stays upright and centered in frame without drifting; the pipette moves in and out along the same vertical line each time; the steam/condensation around the water bath builds up and dissipates in a steady, continuous way rather than flickering; the stirring path traces a smooth, unbroken circle with no sudden reversal or freeze; the direction and length of shadows on the bench stay the same from the start of the clip to the end.
level_5: Everything in score 4 holds, and in addition: the tube shows no visible drift or shift in its position or tilt at any point across the full clip; the pipette's speed and the radius of its stirring arc stay constant rather than varying frame to frame; the rising steam from the water bath looks like a continuous, unbroken plume rather than a series of discrete puffs; the reflected light on the liquid's surface stays steady with no sudden glints or flicker; the bench or rack holding the tube shows no visible shaking; and the motion of every object relative to the others looks physically continuous throughout.