Domain: Natural Science — Physics
Target concept: Bile salts or soaps added to an oil–water mixture induce emulsification.

Video generation prompt: Two identical transparent beakers are placed side by side, each containing water and a layer of oil; add liquid soap to the right beaker and gently shake both beakers.

Evaluation guide:
(i) Target concept: Emulsification via surfactant-mediated interfacial stabilization.
Minimum mechanism: Oil and water must be immiscible and initially phase-separated; soap must be introduced exclusively to the oil–water system where emulsification is expected; mechanical agitation must supply energy to overcome interfacial tension; resulting droplets must be sterically stabilized to resist coalescence during observation window.
(ii)Storyline: Frame 0–1: Static side-by-side view showing two beakers, each with sharp oil–water interface. Frame 2–3: Soap added as liquid stream into right beaker only. Frame 4–6: Synchronous gentle shaking begins in both beakers — liquid surfaces oscillate, interfaces undulate. Frame 7–9: Shaking stops; right beaker transitions to persistent cloudy/milky state (fine droplet suspension); left beaker interface rapidly re-stabilizes to horizontal, sharp, and optically distinct. Perspective: Fixed frontal view, centered on both beakers, sufficient field-of-view to resolve interface integrity and droplet texture without occlusion.

Manual:
Experimental Procedure
1. Place two identical transparent cylindrical beakers side-by-side on a flat surface.
2. Fill each beaker with equal volumes of water, then carefully layer oil on top to form two distinct, unmixed layers.
3. Add liquid soap only to the right beaker.
4. Gently shake both beakers simultaneously for ~2 seconds.
Observation of Experimental Phenomena
Before shaking: Both beakers show sharp, horizontal oil–water interfaces.
After shaking: Right beaker becomes cloudy/milky due to oil droplets dispersed in water; left beaker retains clear separation with intact interface.
Summary of Experimental Principles
Bile salts or soaps act as emulsifiers: their amphiphilic molecules surround oil droplets, stabilizing them in water and preventing coalescence.

Prompt Grounding rubric:
level_1: No two transparent beakers visible; no water and oil layers present in either beaker; no liquid soap added; no shaking action performed; no side-by-side spatial arrangement.
level_2: Two transparent beakers are present and side-by-side, but at least one beaker lacks both water and oil layers; or liquid soap is absent from the right beaker; or shaking action is missing for both beakers; or beakers differ in material (e.g., opaque, colored, non-cylindrical).
level_3: Two identical transparent beakers are side-by-side; each contains a distinct water layer and a distinct oil layer (visually separable by interface and appearance); liquid soap is visibly added only to the right beaker; both beakers are shaken (motion initiated and sustained for observable duration); all objects and actions match posted_prompt exactly in type, quantity, location, and sequence order.
level_4: All conditions for score 3 are satisfied, AND the soap addition is clearly localized to the right beaker (no spillage or visible transfer to left beaker); shaking motion is applied synchronously to both beakers (same onset, same directionality, same gross motion pattern); beakers remain stationary on a common surface throughout (no sliding, tipping, or repositioning).
level_5: All conditions for score 4 are satisfied, AND the beakers are identically sized, shaped, and oriented (same height, same cylindrical form, same upright alignment); the water–oil interface in both beakers is initially horizontal and sharply defined before shaking; soap is added as a discrete liquid stream (not powder, gel, or foam) directly into the right beaker’s oil–water system; shaking motion is gentle (no splashing over rim, no vigorous swirling), and both beakers undergo motion of matching amplitude and rhythm.

Scientific and Causal Correctness rubric:
level_1: No emulsification observed in either beaker; no discernible difference between left and right beaker after shaking; oil remains fully separated and continuous in both; no interface disruption or droplet formation visible.
level_2: Emulsification appears in only one beaker but contradicts causal logic (e.g., occurs in left beaker without soap, or fails in right beaker with soap); or oil layer disappears entirely in one beaker without forming dispersed droplets; or water and oil appear miscible from start (no initial separation).
level_3: After shaking, the right beaker shows visible emulsification: oil breaks into numerous small, suspended droplets within water (milky or cloudy appearance), while the left beaker retains a clear, stable oil–water interface with no droplet dispersion; this contrast is visually present and persists long enough to be confirmed (no immediate reseparation during video).
level_4: All conditions for score 3 are satisfied, AND the emulsified state in the right beaker exhibits uniform droplet distribution (no large undispersed oil blobs or floating slicks); the left beaker maintains complete phase separation (no turbidity, no interfacial waviness beyond gentle meniscus), and no transient mixing artifacts (e.g., temporary vortex, momentary cloudiness) occur in the left beaker during shaking.
level_5: All conditions for score 4 are satisfied, AND the emulsified appearance in the right beaker is stable and persistent (no visible coalescence or creaming during video); the left beaker’s oil layer remains fully contiguous, horizontally layered, and optically distinct (no thinning, spreading, or adhesion to glass walls inconsistent with pure oil–water contact); droplet size in right beaker is fine and homogeneous (no visible stratification of droplet sizes or sedimentation).

Spatiotemporal Consistency rubric:
level_1: Beakers teleport (appear/disappear/relocate abruptly); oil or water phases vanish mid-video; lighting changes discontinuously (e.g., flash, blackout, sudden color shift); beaker geometry distorts (e.g., warping, stretching, perspective jump); shaking motion starts/stops with frame-level discontinuity.
level_2: One beaker shifts position relative to the other (e.g., lateral drift, rotation, vertical lift) without physical cause; oil–water interface flickers or fractures unnaturally (e.g., pixelated rupture, jagged edge oscillation); shaking motion is jerky with >1 visible pause or reversal not attributable to natural deceleration; shadow positions or intensities change inconsistently with fixed light source.
level_3: Both beakers remain fixed in place and maintain rigid structure throughout; oil and water layers retain continuous, unbroken boundaries during shaking (no tearing, vanishing, or artificial segmentation); motion of liquid inside beakers is physically plausible (no floating islands, inverted flow, or gravity-defying suspension); lighting and shadows remain consistent in direction, intensity, and softness across all frames.
level_4: All conditions for score 3 are satisfied, AND the shaking motion is smooth and coherent: liquid surfaces deform continuously (no snapping or instant reshaping); droplet formation in right beaker evolves gradually (no instantaneous appearance of full emulsion); interface in left beaker oscillates gently and damps naturally; no inter-beaker visual bleed (e.g., reflection, glare, chromatic aberration) obscures critical phenomena.
level_5: All conditions for score 4 are satisfied, AND spatial relationships are preserved with zero parallax error: beakers stay perfectly aligned in depth plane (no relative zoom or focus shift); motion trajectories of liquid elements follow laminar-to-turbulent transition consistent with gentle agitation; no temporal aliasing (e.g., strobing, motion blur that erases droplet detail); all visual changes unfold at perceptually natural pace without acceleration/deceleration artifacts.