Domain: Natural Science — Physics
Target concept: The diffusion of ink in hot water and in cold water (entropy increases with rising temperature)

Video generation prompt: Two transparent beakers are placed side by side, the left one hot and steaming, the right one cold with ice inside; blue ink is simultaneously dropped into the center of each.

Evaluation guide:
(i) Target concept: Temperature-dependent diffusion rate as macroscopic manifestation of entropy increase with thermal energy.
Minimum mechanism: Water must remain still (no convection currents dominating), ink must be soluble and non-reactive, beaker walls must not interfere with observation, and thermal states must be stable enough to sustain differential molecular diffusion rates during the observation window.
(ii)Storyline: Frame 0–1: Static wide shot showing two aligned beakers (left with rising steam, right with submerged ice cubes); Frame 2: Two identical blue ink droplets enter frame from top center, aligned horizontally, descending toward surface centers; Frame 3: Droplets contact water surfaces simultaneously, causing identical initial meniscus deformations; Frame 4–9: The left (hot) ink cloud expands outward faster and reaches a visibly larger radius while keeping a smooth, rounded outer edge; the right (cold) ink cloud expands more slowly and stays within a smaller radius, also with a smooth, rounded edge; all motion occurs from a fixed camera position, with no occlusion, and full visibility of both liquid interiors and thermal indicators throughout.

Manual:
Experimental Procedure
1. Place two identical transparent glass beakers side-by-side on a neutral background.
2. Fill left beaker with hot water (visible steam rising from surface); fill right beaker with cold water containing visible ice cubes.
3. Simultaneously release one drop of blue ink at the exact center of the water surface in each beaker.
Observation of Experimental Phenomena
In the hot beaker, blue ink spreads faster and reaches a broader, still smoothly rounded cloud; in the cold beaker, blue ink spreads more slowly and stays within a smaller, smoothly rounded cloud — a clear contrast in diffusion rate and extent, with both plumes keeping a soft, unfragmented edge consistent with still, non-convecting water.
Summary of Experimental Principles
Higher temperature increases molecular kinetic energy and entropy, accelerating diffusion; lower temperature reduces molecular motion, slowing diffusion — demonstrating the thermodynamic link between temperature and entropy-driven processes.

Prompt Grounding rubric:
level_1: Fewer than two transparent beakers appear, or the two beakers are not placed side by side, or both thermal cues are missing at once (no steam over either beaker and no ice in either beaker), or the ink dropped in is a color other than blue, or ink is dropped into only one of the two beakers, or the two ink drops clearly enter at different times rather than together.
level_2: Two transparent beakers appear side by side and blue ink enters both beakers at roughly the same time, but exactly one thermal cue is missing (steam is absent above what should be the hot beaker, or ice is absent from what should be the cold beaker, but not both), or the ink lands noticeably off-center (near the wall rather than the middle of the water surface) in one or both beakers.
level_3: Two transparent beakers sit side by side; the left beaker has visible steam rising from its surface; the right beaker has visible ice cubes inside it; blue ink is present in both beakers; the two ink drops enter the frame at essentially the same moment; each drop lands at roughly the center of its beaker's water surface, matching everything described in the prompt.
level_4: Everything required for score 3 holds, plus: the two beakers sit at mirrored, evenly spaced positions with their bases aligned at the same height; the steam over the hot beaker rises mostly straight up rather than drifting sideways; the ice stays fully visible inside the cold beaker throughout; and the two ink drops match each other in size and color and follow mirrored paths into each beaker.
level_5: Everything required for score 4 holds, plus: the two beakers match each other in shape and size; the steam is a thin, continuous, mostly vertical wisp with no condensation visible on the beaker walls; the ice consists of several distinct, solid, translucent cubes fully contained in the cold beaker (no melted puddle or stray fragments); and the two ink drops match in size and color, enter at the same instant, and show no stray smearing on contact.

Scientific and Causal Correctness rubric:
level_1: No visible difference in diffusion appears between the two beakers; or diffusion looks the same speed/extent in both; or the ink in the cold beaker spreads faster than the ink in the hot beaker (reversed from what temperature dependence predicts); or the ink stays as a compact, unchanging blob in both beakers; or the ink disappears from view instead of dispersing; or the ink's color changes to something other than blue (e.g., turns green or purple) at any point.
level_2: Diffusion appears in at least one beaker, but in a way that contradicts faster molecular motion at higher temperature: e.g., the ink contracts inward, forms a ring instead of spreading, sinks as a blob without spreading outward, or drifts upward against gravity instead of diffusing through the water; or visible spreading starts before the ink drop actually touches the water surface; or the hot beaker shows spreading while the cold beaker shows no change at all.
level_3: Diffusion is visible in both beakers; the hot (left) beaker's ink spreads faster and reaches a larger, still smoothly rounded area; the cold (right) beaker's ink spreads more slowly and stays within a smaller, smoothly rounded area, a clear rate-and-extent contrast that matches faster molecular motion at higher temperature.
level_4: Everything required for score 3 holds, plus: the ink stays blue in both beakers (no hue shift), stays fully liquid (no clumping, precipitate, or separating into layers), and keeps a gradient from a darker center to a paler edge (no sudden opaque patches or cloudiness); neither beaker's ink front develops sharp, jagged, or unnaturally hard-edged boundaries.
level_5: Everything required for score 4 holds, plus: the hot beaker's ink reaches clearly greater radial coverage and turns a uniform pale blue sooner than the cold beaker's ink, while its outer edge stays smooth and rounded rather than fragmenting; the cold beaker's ink keeps a darker, more concentrated core for longer as it slowly expands, also with a smooth rounded edge; neither beaker shows swirling currents, splashes, or secondary droplets that would indicate the water is being stirred or convecting rather than sitting still.

Spatiotemporal Consistency rubric:
level_1: One or both beakers change position abruptly between frames, or a beaker is missing from view for a stretch of frames and then reappears unchanged, or the steam plume or the ice cubes are visible in one frame and completely gone in the next only to return later, or a beaker's wall visibly warps, bulges, or vanishes, or the overall scene lighting switches abruptly from one look to another (e.g., a shadow that suddenly falls on the opposite side) rather than shifting gradually.
level_2: At least one clear but less extreme break in continuity: an ink drop's size or shape changes suddenly between frames rather than through visible motion, or the rising steam stalls, reverses, or restarts mid-rise, or the number or position of the ice cubes changes without any visible motion causing it, or a beaker's base shifts sideways or up/down between frames without any camera movement, or objects in the background appear to jump or shear sideways.
level_3: Both beakers stay in one fixed spot throughout the clip; the steam rises continuously upward without sudden jumps; the ice cubes keep the same count and stay in the same place relative to the cold beaker's walls; each ink drop falls and lands on the water smoothly, without disappearing mid-fall or bouncing unnaturally; neither beaker's shape becomes distorted or collapses at any point.
level_4: Everything required for score 3 holds, plus: the steam shows a natural, gradually changing wispy rise rather than a static rigid column; the ice cubes keep a consistent size and translucency from frame to frame; the diffusing ink cloud in each beaker keeps growing outward frame after frame without freezing mid-expansion or momentarily shrinking back; and the camera framing stays fixed with no sudden reframing.
level_5: Everything required for score 4 holds, plus: there is no visible frame-to-frame duplication or strobing in the ink, steam, or ice; the ink's first contact with the water produces a brief, believable ripple that then settles into smooth, continuous outward diffusion; the steam's density and drift change gradually rather than snapping between states; and the ice cubes keep a stable, translucent look with consistent highlights for the whole sequence.