Domain: Engineering — Food and Bioprocess Engineering
Target concept: Cholesterol Determination (Liebermann-Burchard Method)

Video generation prompt: Take 1 mL of yolk extract into a dry test tube, add 5 mL of ice acetic acid to dissolve it, then add 1 mL of concentrated sulfuric acid and shake thoroughly to mix uniformly.

Evaluation guide:
(i) Target concept: Chromogenic detection of cholesterol via acid-catalyzed condensation.
Minimum mechanism: Presence of cholesterol + acetic acid + concentrated H2SO4 → in situ acetic anhydride formation → dehydration → cholestadiene → chromogen complex with aldehydes → green-blue color.
(ii)Storyline: Frame 1: Dry test tube with 1 mL opaque yellow yolk extract at bottom. Frame 2: Clear ice acetic acid poured in, forming a distinct upper layer. Frame 3: Viscous, colorless-to-pale concentrated sulfuric acid added, contacting the interface; no immediate color. Frame 4: Shaking begins; liquid agitates, interface blurs. Frame 5: During shaking, green hue appears at the acid-contact zone and propagates. Frame 6: Post-shaking, uniform deep green-blue solution fills the tube; a faint vapor may briefly appear and dissipate. All events occur from a fixed frontal viewpoint; no cutaways; tube remains centered and upright; lighting stable; color progression must be causally locked to acid addition and mechanical mixing.

Manual:
Experimental Procedure
1. Place 1 mL yolk extract into a dry test tube.
2. Add 5 mL ice acetic acid.
3. Add 1 mL concentrated sulfuric acid.
4. Shake thoroughly to mix uniformly.
Observation of Experimental Phenomena
Immediate green-to-blue color development upon mixing, progressing to uniform deep green-blue solution; mild transient vapor may rise from surface.
Summary of Experimental Principles
Cholesterol in yolk reacts with acetic anhydride (formed in situ from acetic acid + H2SO4) to form cholestadiene, which condenses with aldehyde impurities to yield green-blue chromogen — characteristic of Liebermann-Burchard method.

Prompt Grounding rubric:
level_1: No dry test tube is shown; no yolk extract appears; ice acetic acid is never added; concentrated sulfuric acid is never added; no shaking motion occurs; none of the three reagents (yolk extract, ice acetic acid, concentrated sulfuric acid) or the test tube appear anywhere in the video.
level_2: At least one correct object appears (e.g., a test tube) but it already holds liquid or condensation before anything is added; or yolk extract is shown but its volume looks nowhere near the ~1 mL called for; or ice acetic acid is present but not recognizable as a liquid being poured into the tube; or concentrated sulfuric acid is missing or visually indistinguishable from the acetic acid; or the order of actions is scrambled (e.g., shaking happens before any reagent is added).
level_3: An empty, dry test tube is shown; roughly 1 mL of opaque pale-yellow yolk extract is placed into it as a small liquid layer at the bottom; about 5 mL of clear ice acetic acid is then added as a visibly separate addition that initially layers rather than instantly blending; about 1 mL of concentrated sulfuric acid is then added as a distinct, denser-looking stream than the acetic acid; all three liquids and the tube are present and consistent with a real lab setup; however, the shaking step is missing entirely or too brief to show any visible mixing motion.
level_4: All objects are present and correctly identified in order: dry test tube, ~1 mL opaque yellow yolk extract, ~5 mL clear ice acetic acid, ~1 mL concentrated sulfuric acid (visibly denser and slower-flowing than the acetic acid), added in the sequence yolk extract, then acetic acid, then sulfuric acid; a shaking motion is shown and lasts long enough to visibly agitate the liquid; no extraneous objects or steps appear; but after shaking the liquid still shows visible streaks, droplets, or a partly separated layer rather than a fully blended appearance.
level_5: All objects are present and visually unambiguous: a dry test tube with no condensation on its walls; a single, clearly bounded ~1 mL layer of opaque pale-yellow yolk extract at the bottom; ~5 mL of clear ice acetic acid added on top, roughly five times the yolk layer's volume; ~1 mL of concentrated sulfuric acid added as a distinct, colorless-to-very-pale, denser and slower-flowing stream than the acetic acid; each addition happens one at a time with no overlap; the shaking motion is vigorous and sustained, visibly agitating the full length of the liquid column; immediately after shaking the liquid looks fully and evenly blended, with no remaining layering, streaks, or droplets.

Scientific and Causal Correctness rubric:
level_1: No hint of the green-blue Liebermann-Burchard color ever appears; the liquid stays pale yellow, colorless, or otherwise unchanged in hue all the way to the end of the video; or a green/blue tint appears before the sulfuric acid has been added at all.
level_2: A color change happens but it is the wrong color for this reaction (e.g., the mixture turns red, brown, black, or purple instead of green or blue); or a green/blue tint appears only as a thin surface film without spreading into the bulk liquid; or the timing of the color change has no visible connection to when the sulfuric acid was added or when shaking occurred.
level_3: A green-to-blue color starts to appear only after the concentrated sulfuric acid has been added and only during or after shaking begins; the color is still localized (e.g., only near the acid-contact zone or in swirled streaks) rather than filling the whole tube; the liquid still looks layered or streaked while the color is emerging, but the timing relative to acid addition and shaking matches what the Liebermann-Burchard reaction should look like.
level_4: The green-to-blue color appears only after the sulfuric acid has been fully added and only once shaking starts, then spreads outward from the point of acid contact until the whole liquid column looks a uniform green-blue; no wrong-colored patches (e.g., no yellow halo, no red edge) appear at any point; the color never appears before the acid is added and never appears only after shaking has already stopped; a faint vapor or slight fogging on the tube wall may or may not be visible; either is acceptable at this level.
level_5: All conditions of the 4-point level are met, and the color's first appearance is right at the point where the sulfuric acid meets the acetic-acid/yolk mixture, spreading outward evenly during shaking until the entire tube is a uniform deep green-blue (not turquoise, violet, or gray) with no yellow or colorless patches remaining; if a thin wisp of vapor rises from the liquid surface during or just after shaking, it looks brief and gentle rather than like boiling, splashing, or heavy condensation on the tube walls, but the video is not penalized if no vapor is visible at all.

Spatiotemporal Consistency rubric:
level_1: The test tube goes missing from the frame at some point and then reappears with no camera motion explaining it; a liquid's volume changes size or disappears between one frame and the next with no visible cause; the shaking motion jumps or stutters so hard that steps of it appear skipped; the tube snaps to a dramatically different tilt (more than roughly a quarter turn) with no visible motion in between; the tube deforms unnaturally, such as bulging outward and then snapping back to its original shape; or a shadow or highlight on the tube disappears and comes back with no change in the scene's lighting.
level_2: The tube shifts sideways by more than about a third of its own width between shots with no visible motion carrying it there; the liquid level resets to a different height with no visible cause; the shaking motion starts or stops instantly with no visible ramp-up or slow-down; the sulfuric acid stream appears already flowing in mid-air with no visible source; the camera cuts to a different angle with no visible transition connecting the two views.
level_3: The tube stays centered in frame, upright, with its base in the same place throughout; each liquid layer keeps its relative position as the next liquid is added; the shaking motion looks like a smooth, confined wrist-level back-and-forth rather than a wide arm swing or spin; nothing in the shot flickers, disappears, or duplicates; the lighting on the scene does not visibly shift; brief, hard-to-notice unsteadiness during otherwise-still moments, or a single short stumble in the shaking motion, would not by itself lower the score below this level.
level_4: The tube stays in the same position, orientation, and apparent size for the entire video; every liquid addition visibly pours in from off-screen at the tube's mouth, from a consistent direction; the shaking motion keeps a steady rhythm and range of motion without sudden changes; nothing flickers, jumps, or warps in perspective; a small amount of motion blur during the fastest part of the shaking is acceptable as long as it does not hide the liquid's color or state.
level_5: The tube shows no visible sideways or vertical drift and stays visibly vertical throughout, with no noticeable tilt developing over the course of the video; every liquid addition follows a physically believable path (the acetic acid pours in a steady stream, the denser sulfuric acid drips or flows more slowly with a visibly thicker stream); the shaking motion looks mechanically consistent (same pivot point at the tube's base, same swing width, same rhythm from start to finish), with no visible motion blur, flicker, or change in the scene's lighting at any point.