Domain: Healthcare — Nutrition & Dietetics
Target concept: Emulsification stability test (oil-in-water emulsion)

Video generation prompt: Add equal volumes of water and edible oil to a transparent test tube. Add a small amount of emulsifier. Seal the test tube, vigorously shake it for several seconds, then place the test tube upright and observe over time. Clearly demonstrate the experimental procedure, equipment used, and operational methods.

Evaluation guide:
(i) Target concept: Oil-in-water emulsion formation and destabilization governed by interfacial tension reduction and droplet coalescence.
Minimum mechanism: Immiscible liquids must have density difference (oil < water) to enable stratification; emulsifier must be interfacially active to form transient droplets; Brownian motion and gravity drive coalescence and creaming without stabilizer.
(ii)Storyline: [Frame 0–1] Static upright tube showing water (bottom, clear) + oil (top, pale yellow), sharp horizontal interface. [Frame 2–3] Emulsifier added visibly at interface. [Frame 4–6] Tube sealed and shaken — liquid agitates turbulently, losing layer definition. [Frame 7] Tube placed upright, fully stationary, meniscus reforming. [Frame 8–10] Cloudy opacity gradually clears from bottom upward; oil layer visibly thickens at top while water layer sharpens at bottom; final frame shows identical stratification as Frame 0, confirming reversible instability.

Manual:
Experimental Procedure
1. Add equal volumes of clear water (lower layer) and pale yellow edible oil (upper layer) to a transparent cylindrical test tube.
2. Add a small visible amount of emulsifier (e.g., lecithin powder or liquid) at the interface.
3. Seal tube, shake vigorously for ~2 seconds, then place upright immediately.
4. Observe: initial cloudy emulsion → gradual clearing → full re-separation into two sharp layers.
Observation of Experimental Phenomena
Pre-shake: two distinct horizontal layers (water below, oil above). Post-shake: uniform cloudy/milky opacity. During observation: progressive reduction in cloudiness, oil rising continuously, water settling continuously, final restoration of sharp oil-water interface.
Summary of Experimental Principles
Emulsification stability depends on emulsifier presence: it reduces interfacial tension, enabling temporary dispersion of oil droplets in water; absence of stabilizer leads to coalescence and phase separation over time.

Prompt Grounding rubric:
level_1: No transparent test tube appears; there is no visible water or oil; no emulsifier is added; there's no shaking motion; the tube is never set upright for observation; the clip shows no time-lapse of the liquids sitting still afterward.
level_2: A test tube with two liquid layers is shown, but water or oil is missing or hard to identify by its color; no emulsifier is ever added, or it's unclear what was added; a shaking motion is only implied (e.g. the tube is shown static before and after with no visible agitation); or the tube is set upright without any shaking having occurred first.
level_3: A transparent test tube holds two clearly separate liquid layers (a lower, colorless water layer and an upper, pale-yellow oil layer) before shaking; a small amount of emulsifier is visibly added, seen as droplets, powder, or a small liquid dose either at the interface or within one of the layers; the tube is then sealed and visibly shaken (hand and tube both moving, liquid clearly agitated); afterward the tube is placed upright and left still for observation.
level_4: Everything in the 3-point description holds, and in addition the water and oil layers look like matching heights before shaking (equal volumes); the emulsifier goes in before the shaking starts, not after; the shaking is vigorous, with several visible back-and-forth or up-and-down motions rather than a single weak wobble; the tube goes upright immediately after shaking stops, with no other action in between, and the observation period begins with the tube already still.
level_5: Everything in the 4-point description holds, and in addition the emulsifier is added just the one time, visibly concentrated at the interface or dissolved into the water layer rather than scattered throughout; the shaking clearly mixes the liquids into a cloudy blend rather than just sloshing two layers side to side; once upright, no hand touches or repositions the tube again during the observation window; and the tube stays in the same spot in the frame the whole time, so the water-oil-emulsifier setup is fully legible throughout.

Scientific and Causal Correctness rubric:
level_1: No emulsion behavior is shown at all - the liquids look miscible or already blended from the very first frame, or nothing changes over time, so there's no sign of a temporary cloudy mixture forming and then separating.
level_2: Two layers exist before shaking, but shaking either produces no visible change (the tube looks identical before and after) or the cloudy mixture clears back into two layers the instant shaking stops with no gradual transition; or the oil ends up below the water with no reason given for that reversal of the expected density order.
level_3: Before shaking, water sits below and oil sits above as two sharp layers; after shaking, the tube turns uniformly cloudy/milky with no visible interface; over the following seconds, the cloudiness starts clearing - first at the top and bottom - and the two layers gradually reappear, with the oil ending up on top and the water on the bottom again.
level_4: Everything in the 3-point description holds, and in addition the cloudy state only shows up right after shaking and fades in a gradual, continuous way rather than vanishing all at once or in sudden jumps; the oil visibly rises while the water visibly settles as separate, ongoing trends; and the tube ends up looking essentially like it did before shaking, with oil back on top of water.
level_5: Everything in the 4-point description holds, and in addition the post-shake cloudiness looks evenly mixed throughout the tube rather than patchy or streaked; the clearing process doesn't start until the shaking has fully stopped and the tube is upright; the oil's rise and the water's settling happen together, steadily, without either one pausing or reversing; and the tube ends with a clean, roughly horizontal interface that looks like the original pre-shake layering.

Spatiotemporal Consistency rubric:
level_1: A severe break occurs - the test tube vanishes and reappears, the water and oil layers jump to a different arrangement with no motion shown getting them there, the lighting on the scene suddenly changes to a different setup mid-clip, the tube spins more than a quarter turn with no visible cause, or the tube itself appears to crack, split, or warp out of its normal cylindrical shape.
level_2: A clear but less extreme problem occurs - the tube shakes so violently and erratically once it's supposed to be resting upright that it looks like an editing glitch rather than settling motion; the liquid surface jumps around unpredictably instead of settling down; the light or shadow on the tube flickers inconsistently between frames; the background behind the tube changes abruptly; or the camera suddenly refocuses partway through, producing a jarring blur.
level_3: A small, easy-to-miss issue occurs - a bit of motion blur during the shaking that obscures the liquid's detail, a slight drift in the tube's position while it's supposedly held still (less than about 5% of the frame's height), or a faint shadow shift on the tube wall during shaking - but the tube never disappears, warps, or snaps between positions, and the sealed tube, liquid layers, and hand stay in a sensible arrangement throughout.
level_4: Everything in the 3-point description holds, and in addition the shaking motion looks smooth and physically natural rather than jerky or stop-motion-like; once upright, the framing holds steady with no drift or shake; the tube's lighting looks the same from the moment it's set upright through the end of the observation, matching how it looked at the very start of the clip; and the liquid's surface settles down gradually after shaking rather than jittering indefinitely.
level_5: Everything in the 4-point description holds, and in addition the tube's walls stay straight and parallel in every frame; the curved meniscus where the liquid meets the tube wall looks natural throughout; the tube, liquid layers, and interface stay smooth and coherent from frame to frame with no visible glitches, tears, or warping; and the tube's motion - from shaking, to settling, to sitting still - follows one continuous, physically believable path rather than skipping or snapping between states.