Domain: Natural Science — Chemistry
Target concept: The Effect of Cold and Warm Acetic Acid on the Temperature of the Effervescence Reaction

Video generation prompt: Two beakers are placed side by side, containing cold vinegar and warm vinegar, respectively; an equal amount of baking soda is added to both.

Evaluation guide:
(i) Target concept: Temperature dependence of reaction kinetics in acid-base gas evolution reactions.
Minimum mechanism: CO₂ gas must be generated *only* upon contact between acetic acid and sodium bicarbonate; bubble formation requires nucleation at solid-liquid interface; foam layer forms due to surfactant-like stabilization of CO₂ bubbles by dissolved species; warmer solution reduces gas solubility and increases diffusion rate, accelerating bubble growth and release.
(ii)Storyline: Frame 0–1: Static shot showing two identical beakers side-by-side, each filled with colorless liquid (cold left, warm right; distinguished only by subsequent reaction vigor). Frame 2–3: Hands (or dispenser) introduce white granular baking soda simultaneously into both beakers; motion identical in timing and scale. Frame 4–8: Immediate onset of bubbling in both; bubbles rise continuously from bottom; foam layer nucleates and expands upward; warm side consistently exceeds cold side in bubble count, rise speed, and foam thickness. Frame 9–10: Foam peaks and begins gradual collapse; warm side retains foam longer. Throughout: fixed viewpoint, consistent lighting, no occlusion, no object deformation.

Manual:
Experimental Procedure
1. Place two identical transparent beakers side-by-side on a flat surface.
2. Fill left beaker with cold vinegar (colorless liquid), right beaker with warm vinegar (colorless liquid).
3. Simultaneously add equal amounts of white baking soda powder to both beakers.
Observation of Experimental Phenomena
- Both beakers produce effervescence (rising bubbles + transient foam layer) immediately after addition.
- The warm vinegar beaker shows more vigorous effervescence: faster bubble rise, higher bubble density, thicker and longer-lasting foam layer.
- The cold vinegar beaker shows slower, sparser bubbling and thinner, quicker-collapsing foam.
Summary of Experimental Principles
- Acetic acid in vinegar reacts with sodium bicarbonate to produce carbon dioxide gas.
- Reaction rate increases with temperature: warm vinegar accelerates molecular collision frequency and energy, yielding faster CO₂ generation and more vigorous effervescence.

Prompt Grounding rubric:
level_1: Only one beaker is shown, or no vinegar is visible in either container, or baking soda is never shown being added to either beaker, or the two containers are never visible together in the frame at the same time.
level_2: Two containers appear, but they are not matching beakers (e.g. one is a cup or bowl), or vinegar is visible in only one of them, or baking soda is added to only one container, or the two containers are stacked or otherwise not shown side by side at the same time.
level_3: Two matching beakers sit side by side in the same shot, one holding the cold vinegar and one holding the warm vinegar; baking soda is visibly added to both beakers while they remain in place and in view.
level_4: The two beakers match each other in shape, size, and color; the amount of baking soda added to each looks about the same in both volume and pour duration; nothing extraneous, such as labels, a thermometer, or a lingering hand, blocks the view of either beaker during the addition.
level_5: Both beakers are unambiguous, transparent, cylindrical containers filled with clear liquid to a similar height, roughly one-third to one-half of the beaker, before any addition; the baking soda poured into each follows the same path, speed, and endpoint on both sides; there is no cut, flicker, or jump in either beaker's appearance during the entire addition sequence.

Scientific and Causal Correctness rubric:
level_1: Neither beaker shows bubbling, foam, or cloudiness after the baking soda is added, or both beakers bubble identically with no visible difference between the cold and warm side.
level_2: Only one of the two beakers effervesces at all, or the bubbles that appear never rise or disturb the surface, or no foam layer ever forms, or the cold and warm beakers show the same intensity and duration of bubbling.
level_3: Both beakers produce rising bubbles and a temporary foam layer right after the baking soda is added; the warm vinegar beaker's reaction is visibly more vigorous than the cold one, showing more bubbles, a faster rise, or a thicker foam, for at least part of the clip.
level_4: The warm vinegar beaker consistently shows a faster onset, with smaller and more numerous bubbles, and a taller foam layer than the cold vinegar beaker throughout the reaction, not just briefly, while the cold vinegar beaker shows comparatively larger, sparser bubbles; the foam in the warm beaker also holds up longer before collapsing than the foam in the cold beaker; at no point does the cold beaker out-bubble the warm one.
level_5: From the moment the baking soda touches each liquid, the warm vinegar beaker's bubbling starts sooner, stays denser, and its foam rises higher and lasts longer than the cold vinegar beaker's, with this relationship holding at every stage of the reaction; bubbles rise from within the liquid rather than appearing at the surface out of nowhere, and foam builds up gradually rather than appearing instantly fully formed.

Spatiotemporal Consistency rubric:
level_1: One or both beakers change position or size abruptly between frames, the liquid level changes with no visible cause, the baking soda vanishes mid-pour and reappears elsewhere, a beaker's outline visibly warps or stretches, the lighting abruptly shifts from bright to dark (or the reverse) with no visible cause, or background elements outside the beakers flicker or change appearance inconsistently between frames.
level_2: A beaker rotates or slides noticeably between frames without anything moving it, the liquid surface ripples unnaturally as if independent of the reaction, the baking soda's fall from hand to beaker skips a visible gap in its path, a cast shadow flips to point in a different direction between frames with no light source moving to explain it, or the foam appears already fully built up in a single frame with no bubbles shown forming it first.
level_3: Both beakers stay in the same place and orientation throughout; the liquid surface is calm and undisturbed before the baking soda is added; the baking soda travels in one continuous motion from the source into each beaker; bubbles visibly originate from within the liquid and rise upward, and the foam builds up gradually from the bottom rather than snapping into place.
level_4: Both beakers remain fully visible at the same time with neither blocking the other; the camera does not shift position or angle at any point; the liquid surface is never frozen while bubbles are visibly moving through it; bubbles rise with a consistent, steady vertical motion, and the foam's thickness grows smoothly rather than in sudden jumps.
level_5: No bubble appears out of nowhere without rising from within the liquid; no foam layer shrinks and then re-grows without cause; the rate and size of the bubbles change smoothly rather than jumping abruptly; the camera viewpoint stays fixed with no visible shake, zoom, or pan for the whole clip.