Domain: Natural Science — Microbiology
Target concept: Yeast in a sugar-rich solution vs. yeast in pure water produce carbon dioxide bubbles.

Video generation prompt: Two transparent bottles are placed side by side, with their mouths loosely covered by balloons; the left bottle contains warm sugar water, and the right bottle contains warm distilled water. After adding equal amounts of dry yeast to both, they are left undisturbed for incubation.

Evaluation guide:
(i) Target concept: Anaerobic fermentation by Saccharomyces cerevisiae requires fermentable carbohydrate substrate to produce CO₂.
Minimum mechanism: Yeast cells must be viable, temperature must be permissive (~30–40°C), sugar must be present and soluble, and O₂ limitation must be ensured (loose balloon allows CO₂ accumulation but prevents aerobic respiration dominance).
(ii)Storyline: Frame 1–2: Static wide shot showing two identical bottles side-by-side, both with clear liquids and loose balloons. Frame 3–4: Hands add dry yeast granules to both bottles in synchronized motion. Frame 5–10: Continuous still shot: left balloon progressively expands (visible dome growth, neck lift, membrane stretch), right balloon unchanged in shape/size; no liquid agitation, no color shift, no bubble streams visible inside bottles; viewpoint fixed, lighting stable, no occlusions.

Manual:
Experimental Procedure
1. Place two identical transparent bottles side-by-side.
2. Fill left bottle with warm sugar water; right bottle with warm distilled water.
3. Loosely cover each bottle mouth with an identical balloon.
4. Add equal amounts of dry yeast to both bottles simultaneously.
5. Leave undisturbed for incubation.
Observation of Experimental Phenomena
Left balloon inflates visibly due to CO₂ production; right balloon remains completely deflated.
Summary of Experimental Principles
Yeast ferments sugar anaerobically, producing carbon dioxide gas; no sugar means no fermentation, hence no gas.

Prompt Grounding rubric:
level_1: No two transparent bottles are shown, or only one bottle appears; no balloon is draped over a bottle mouth; the liquids are not identifiable as warm sugar water and warm distilled water; no dry yeast is added to either bottle; or the bottles are never shown positioned next to each other for comparison.
level_2: Two bottles appear near each other, but the setup is wrong or incomplete: one bottle lacks a balloon over its mouth, a balloon is tied down airtight instead of draped loosely, both bottles appear to hold the same liquid, or yeast is added to only one bottle instead of both.
level_3: Two similarly sized transparent bottles sit next to each other, each with a balloon loosely draped over its mouth (not sealed tight); the left bottle's liquid reads as warm sugar water and the right bottle's liquid reads as warm distilled water (via label, dialogue, or an added visual cue like sugar granules dissolving on screen); dry yeast is added to both bottles in visually comparable amounts, after which the scene settles into an undisturbed incubation period.
level_4: All score 3 elements hold, and additionally the two liquids stay distinguishable via a legible cue that persists for the whole shot (e.g., on-screen labels "Sugar Water" / "Distilled Water", or sugar crystals shown only in the left bottle before mixing); each balloon keeps the same loose, sagging drape rather than tightening or slipping off; yeast is poured into each bottle in a single, comparable amount rather than trickling in unevenly over a long stretch.
level_5: All score 4 elements hold, and additionally the two bottles match each other in size, shape, and transparency, and the two balloons match in color, size, and sag; yeast is added to both bottles within the same brief window rather than one bottle first with a long gap before the other; any on-screen labels use matching font, size, and placement so a viewer can tell at a glance which bottle is which.

Scientific and Causal Correctness rubric:
level_1: Neither balloon shows any inflation at all, so there's no visible fermentation signal in either bottle; or both balloons inflate by a similar amount, erasing the sugar-vs-no-sugar contrast the experiment is meant to show.
level_2: A balloon inflates, but the pattern contradicts the science: the distilled-water (right) balloon inflates instead of, or as much as, the sugar-water (left) balloon; or a balloon begins expanding before the yeast is added; or the liquid itself changes color or turns cloudy in a way that has nothing to do with fermentation.
level_3: Only the left (sugar water) balloon visibly grows larger over the course of the incubation shot, while the right (distilled water) balloon stays essentially the same size and shape it started with; no color change or cloudiness appears in either liquid; the left balloon's growth only begins after yeast has been added to both bottles.
level_4: All score 3 conditions hold, and additionally the left balloon's growth reads as a steady, ongoing expansion rather than one sudden jump in size; the right balloon shows no growth at all, not even a slight puff or lift at the neck; no extra effects appear that aren't part of the fermentation story, such as foam spilling over or visible bubbling breaking the liquid surface.
level_5: All score 4 conditions hold, and additionally the left balloon's expansion looks continuously gradual across the whole incubation shot, without pausing, shrinking back, or lurching in size; the right balloon looks exactly as still and unchanged at the end as it did at the start, with no lift, sag change, or wobble of its own; nothing in the shot could be mistaken for gas activity in the right bottle (no stray reflections or specks that look like bubbles or balloon movement).

Spatiotemporal Consistency rubric:
level_1: A bottle or balloon vanishes and reappears, or swaps position with the other between frames; the two bottles' relative left-right arrangement flips or scrambles; lighting flips from one side to the other or between bright and dark between consecutive frames with no transition; a bottle or balloon's shape warps unnaturally (e.g., stretches, melts, or bends).
level_2: A clear spatial or lighting break occurs: the bottles drift closer together or farther apart than their starting arrangement; a balloon detaches from its bottle mouth and later reattaches; the liquid level inside a bottle rises or falls without any addition or removal shown; the direction or strength of the shadows cast by the bottles changes between shots as though the light source moved.
level_3: The two bottles stay in the same left-right arrangement and distance from each other throughout the shot; each balloon stays attached at its bottle's mouth without slipping off or reattaching; the liquid surface in each bottle stays at a constant, unshifting level (aside from the balloon's own inflation); shadows cast by the bottles and balloons point in the same direction with roughly the same darkness from the start of the shot to the end.
level_4: All score 3 conditions hold, and additionally the camera holds a single fixed framing with no zooming in/out, panning, or tilting; the two bottles show no shift in their apparent size or spacing relative to each other that would suggest camera movement; nothing (like a hand or arm) partially covers a bottle or balloon and then disappears from frame without ever being shown leaving.
level_5: All score 4 conditions hold, and additionally the inflating left balloon's outline shows no visible shaking or drifting from one frame to the next: its growth reads as smooth and continuous rather than juddery; the background stays in consistent focus throughout, with no blurring in or out; no motion blur appears anywhere in the shot, consistent with the bottles themselves never moving.