Domain: Engineering — Food and Bioprocess Engineering
Target concept: Curcumin Detection (Ethanol Extraction - Colorimetric Method)

Video generation prompt: Take 1 mL of turmeric ethanol extract into a test tube, add 2 mL of dilute sodium hydroxide solution, and shake thoroughly.

Evaluation guide:
(i) Target concept: Curcumin's pH-dependent color response. Curcumin, the diarylheptanoid pigment extracted from turmeric into ethanol, carries an acidic, enolizable beta-diketone/phenolic system; under alkaline conditions it ionizes to a phenolate/enolate form whose light absorption shifts to longer wavelengths, turning the naturally yellow extract into a red-to-reddish-brown solution. This color shift only occurs once the two liquids have actually mixed, not before contact, and not without agitation to homogenize the mixture.
(ii) Storyline: Frame 0-1: static shot of a clean, empty test tube. Frame 2-3: turmeric ethanol extract (bright yellow) poured in, filling roughly one-third of the tube's height. Frame 4-5: dilute sodium hydroxide solution (colorless) poured in on top, filling to roughly three-quarters height. Frame 6-8: the tube is held and shaken with a rhythmic back-and-forth motion, the liquid sloshing coherently and the meniscus deforming with the motion. Frame 9-10: the motion stops, the liquid settles, and within about a second the color shifts from yellow to a uniform red-to-reddish-brown across the whole column, with no further change afterward. Perspective: fixed frontal close-up with the tube occupying most of the frame height, consistent lighting, no occlusion, and a top-open view that keeps the meniscus and color development visible.

Manual:
Experimental Procedure
1. Place an empty test tube upright in a holder.
2. Add 1 mL of turmeric ethanol extract (bright yellow) to the test tube.
3. Add 2 mL of dilute sodium hydroxide (NaOH) solution to the same test tube.
4. Cap or hold the tube securely and shake thoroughly for a few seconds.
Observation of Experimental Phenomena
After shaking, the solution changes uniformly from bright yellow to a stable red-to-reddish-brown color; no precipitation, layering, or color gradient is observed.
Summary of Experimental Principles
Curcumin, the diarylheptanoid pigment in turmeric, carries an acidic, enolizable beta-diketone/phenolic system. Under alkaline conditions (sodium hydroxide), it ionizes to a phenolate/enolate form whose light absorption shifts to longer wavelengths, turning the naturally yellow ethanol extract into a red-to-reddish-brown solution — a color response specific to curcumin's structure and commonly used as a simple qualitative test for its presence.

Prompt Grounding rubric:
level_1: No test tube is present, or neither the turmeric extract nor the sodium hydroxide solution is visible; no pouring, adding, or shaking action occurs; the scene does not read as a laboratory colorimetric setup.
level_2: A test tube is present but empty, or only one of the two liquids (the yellow turmeric extract or the colorless sodium hydroxide solution) is added while the other never appears; no shaking motion occurs; the liquids and container have no clear association with a curcumin colorimetric test.
level_3: The test tube contains liquid: a yellow turmeric ethanol extract is visibly poured in from an identifiable source, then a second, colorless liquid (the sodium hydroxide solution) is visibly poured in on top of it; a shaking action follows with visible liquid movement; the test tube, the yellow extract, and the alkaline reagent are all present and match the setup in the prompt.
level_4: Everything required for the previous level is present, and in addition the pour order is correct: turmeric extract added first, sodium hydroxide solution added second, with the second addition visibly larger in volume, roughly matching the prompt's 1:2 ratio; shaking begins only after both liquids are in the tube; no extraneous actions appear (no stirring with a rod, no repeated pipetting, no shaking before both liquids are added).
level_5: Everything required for the previous level is present, and in addition the whole sequence plays as one continuous, unbroken shot: empty tube, first pour, second pour, then shaking, with no cuts, no repositioning, and nothing popping in or out of frame; the tube, its holder, and the liquids keep a consistent appearance and spatial arrangement from start to finish.

Scientific and Causal Correctness rubric:
level_1: No color change occurs at all, or the final liquid ends up a color inconsistent with curcumin's known behavior (it stays colorless, or turns blue, green, or purple); or a red/brown color appears despite no liquid ever having been added, violating the premise that the color requires contact between the two liquids.
level_2: A color change occurs, but the resulting hue is implausible for this reaction (bright pink, black, or effectively unchanged pale yellow); or the color appears the instant the second liquid touches the surface, before any mixing or shaking has happened; or the color stays confined to a thin surface layer or streaks instead of spreading through the liquid.
level_3: After shaking, the mixture settles into a uniform red-to-reddish-brown color throughout the liquid column; this color is clearly different from the extract's starting yellow and does not appear until after the sodium hydroxide has been added and the mixture agitated; the resulting hue is consistent with curcumin's known base-induced color shift from yellow toward red.
level_4: Everything required for the previous level is present, and in addition the color's appearance is clearly tied to the shaking step: no red or brown tint is visible before shaking starts, the color builds up while shaking is underway, and it stabilizes right as the shaking stops, with no fading, layering, or separation into differently colored zones afterward.
level_5: Everything required for the previous level is present, and in addition the red-to-reddish-brown color is deep, even, and stable for the remainder of the shot, with no leftover yellow undertone, no graying, no pooling of color near the meniscus or tube walls, and no drift toward an unrelated hue such as orange or violet under the shot's lighting.

Spatiotemporal Consistency rubric:
level_1: The test tube or its contents change in a way no physical shake could produce: the tube's on-screen position jumps discontinuously, the liquid level changes with no visible pouring or shaking to cause it, the scene's overall lighting suddenly shifts mid-shot, the background behind the tube changes abruptly, or the tube's shape distorts unnaturally.
level_2: The shaking motion looks jerky or repeatedly stalls rather than reading as one continuous rhythm; the liquid surface stays flat and undisturbed despite the tube visibly moving; the tube's tilt changes inconsistently from moment to moment (tipping one way, then straightening, then tipping the other way with no smooth in-between); shadows or highlights on the tube flicker or jump between frames.
level_3: The test tube stays in a fixed on-screen position and orientation apart from the shaking motion itself; the shaking reads as one continuous, rhythmic motion, with the liquid surface visibly rippling and the meniscus rising and falling in response; the tube and liquid show no clipping, warping, or see-through artifacts; the background and lighting stay steady throughout, with no abrupt cuts.
level_4: Everything required for the previous level is present, and in addition the liquid behaves as one coherent body throughout: no droplets float free of the surface, no liquid splatters outside the tube, and no bubbles pop in or out of existence without cause; the meniscus shape stays consistent with the tube's cylindrical geometry; the shaking's amplitude and rhythm stay steady rather than randomly speeding up or slowing down.
level_5: Everything required for the previous level is present, and in addition the liquid's motion looks physically believable for a shaken tube: it lags slightly behind each shake and then settles back rather than moving in perfect lockstep with the hand; the tube wall shows a believable wet coating where liquid has touched it rather than staying bone-dry above the liquid line; there is no ghost-like doubling of the tube or liquid between frames, and the hand-and-tube motion reads as one smooth, continuous gesture throughout.