Domain: Natural Science — Chemistry
Target concept: Physical Properties of Sulfur

Video generation prompt: Two beakers are placed side by side on the desk. The left beaker contains a suitable amount of carbon disulfide liquid, and the right beaker contains a suitable amount of distilled water. A small amount of solid sulfur is added to both beakers, followed by stirring.

Evaluation guide:
(i) Target concept: Differential solubility of elemental sulfur governed by solvent polarity.
Minimum mechanism: Sulfur must exist as discrete solid particles before addition; carbon disulfide must behave as a nonpolar, volatile solvent capable of molecular dispersion; water must behave as a polar solvent incapable of overcoming sulfur"s lattice energy; dissolution requires direct particle–solvent contact and agitation to initiate dispersion.
(ii)Storyline: Frame 0–1: Static wide shot showing two empty beakers side by side on desk. Frame 2–3: Liquid pouring: left receives pale yellow CS₂, right receives colorless H₂O. Frame 4: Solid sulfur (yellow granules) dispensed simultaneously into both beakers. Frame 5–6: Stirring begins; separate rods enter each beaker and rotate continuously. Frame 7–9: Post-stirring state: left beaker shows uniform yellow solution (no particles), right beaker shows settled/suspended yellow particles in clear water. Perspective: Fixed frontal desk-level view, no camera movement, full beaker visibility throughout; all causal transitions (addition → contact → stirring → dispersion/none) must be visibly contiguous and unbroken.

Manual:
Experimental Procedure
1. Place two identical transparent beakers side by side on a flat desk.
2. Pour carbon disulfide (pale yellow, volatile liquid) into left beaker; pour distilled water (colorless, still liquid) into right beaker.
3. Add small amount of solid sulfur (bright yellow crystalline powder) to each beaker.
4. Stir each beaker separately with clean glass rod.
Observation of Experimental Phenomena
Sulfur rapidly disperses and dissolves in carbon disulfide, forming a uniform pale yellow solution. Sulfur remains visibly undissolved in distilled water — yellow particles settle or suspend without homogenizing.
Summary of Experimental Principles
Sulfur is nonpolar and highly soluble in nonpolar solvents like carbon disulfide, but insoluble in polar solvents like water — demonstrating “like dissolves like” based on molecular polarity.

Prompt Grounding rubric:
level_1: No two beakers visible; or only one beaker present; or no carbon disulfide label/visual cue; or no distilled water label/visual cue; or sulfur not shown as solid before addition; or no stirring action depicted; or beakers not placed side by side on a desk surface.
level_2: Two beakers are present and side by side on a desk, but at least one of the following is missing: (a) clear visual distinction between carbon disulfide and distilled water (e.g., both liquids appear identical in color/transparency), (b) solid sulfur added to both beakers, (c) stirring action applied to both beakers.
level_3: Two beakers side by side on a desk; left beaker contains a liquid visually distinct from right beaker; solid sulfur is visibly added to both beakers; stirring motion is shown for both beakers; all objects (beakers, liquid, sulfur, stirrer) are present and correctly positioned, but no labeling or contextual cues confirm which liquid is carbon disulfide vs. distilled water.
level_4: All elements of 3-score are present AND at least one unambiguous visual cue confirms identity: e.g., left beaker has a visible “CS₂” label or distinctive yellow-tinged liquid (characteristic of commercial carbon disulfide), right beaker has “H₂O” label or colorless/water-like appearance; sulfur remains visibly solid during addition and stirring begins after addition.
level_5: All elements of 4-score are present AND both beakers maintain consistent identity cues throughout: left beaker’s liquid retains its CS₂-specific appearance (pale yellow, volatile sheen) without mixing or color shift; right beaker’s liquid remains colorless and non-volatile-looking; sulfur particles are clearly visible as yellow crystalline solids before and during stirring in both beakers; stirring occurs synchronously and independently in each beaker with no cross-contamination or shared tool.

Scientific and Causal Correctness rubric:
level_1: Sulfur dissolves identically in both beakers; or sulfur disappears completely in water; or sulfur fully dissolves in water; or sulfur remains fully undissolved in carbon disulfide; or color/state of sulfur changes identically in both beakers; or no dissolution contrast is observable.
level_2: Sulfur appears to dissolve in one beaker only, but the dissolution is inconsistent with known solubility: e.g., sulfur dissolves in water (visually disappears or homogenizes) OR fails to dissolve in carbon disulfide (remains as large unmixed clumps with no dispersion).
level_3: Sulfur visibly disperses/dissolves in the left beaker (carbon disulfide): particles break apart, reduce in size, and become uniformly distributed in the liquid, while sulfur remains visibly intact as discrete yellow particles in the right beaker (distilled water); no misattribution of dissolution direction.
level_4: All elements of 3-score are present AND dissolution state is stable post-stirring: left beaker shows homogeneous yellow-tinted solution (no settling, no visible particles); right beaker shows undissolved sulfur settled at bottom or suspended as distinct yellow granules/powder; no particle transfer between beakers; sulfur color remains consistently pale yellow in both.
level_5: All elements of 4-score are present AND dissolution contrast is maximally discriminable: left beaker liquid exhibits uniform pale yellow hue with no sediment or cloudiness; right beaker shows sharp visual separation: clear upper layer + dense yellow sediment or stable suspension of coarse yellow particles; no ambiguity in particle presence/absence, no blending of appearances, no temporal reversal (e.g., particles reappearing after dissolution).

Spatiotemporal Consistency rubric:
level_1: Beakers teleport between frames; or sudden change in beaker position/orientation; or sulfur appears inside beaker without entry motion; or stirring motion starts mid-air with no visible tool contact; or lighting/shadow jumps abruptly between shots.
level_2: At least one major spatiotemporal rupture: e.g., beaker moves laterally without continuous motion; sulfur materializes in liquid without descent path; stirring stops and restarts with inconsistent tool orientation; shadow direction flips between frames; desk surface discontinuity (e.g., texture or edge mismatch).
level_3: All objects maintain fixed spatial relationship: beakers remain side by side on same desk plane; sulfur addition shows downward motion into each beaker; stirring shows continuous rotational motion with consistent tool shape and contact point; no object flickers, vanishes, or warps; lighting and shadow remain directionally stable.
level_4: All elements of 3-score are present AND motion is physically coherent: stirring tool enters frame before contact, maintains contact throughout stirring, exits cleanly; sulfur falls along gravity-aligned path into each beaker; no interpenetration (e.g., stirrer passing through beaker wall); no abrupt scaling or perspective shift.
level_5: All elements of 4-score are present AND full continuity is preserved: no frame-level jitter or micro-teleportation; stirring motion is smooth and unbroken across all frames; sulfur descent and dispersion occur without pause or reversal; desk surface, beaker bases, and liquid menisci remain geometrically stable and aligned; zero inter-frame occlusion artifacts or depth inversion.