Domain: Natural Science — Chemistry
Target concept: Comparison of Ethanol and Acetic Acid

Video generation prompt: Two beakers are placed side by side on the table, with the left beaker containing an appropriate amount of ethanol and the right beaker containing an appropriate amount of acetic acid. Sodium bicarbonate solid is added to both beakers simultaneously.

Evaluation guide:
(i) Target concept: Acid-carbonate reaction selectivity. Only carboxylic acids (e.g., acetic acid), not alcohols (e.g., ethanol), react with carbonate/bicarbonate salts to release CO₂ gas.
Minimum mechanism: Presence of acidic proton (pKa ~4.76 for acetic acid) sufficient to protonate HCO₃⁻; ethanol (pKa ~15.9) lacks proton-donating ability under neutral conditions.
(ii)Storyline: Frame 0–1: Static wide shot showing two side-by-side beakers on table, left labeled/identified as ethanol, right as acetic acid; both contain clear liquids. Frame 2–3: Hand enters with sodium bicarbonate (white granular solid) and deposits it into both beakers in synchronized motion. Frame 4–10: Immediate onset of continuous bubbling exclusively in right beaker; left beaker remains quiescent: no surface disturbance, no bubble formation, no cloudiness; all spatial relationships and lighting remain invariant; viewpoint is fixed frontal mid-shot ensuring full visibility of both beaker interiors and reaction zones.

Manual:
Experimental Procedure
1. Place two identical transparent beakers side-by-side on a flat table: left beaker filled with ethanol, right beaker filled with acetic acid.
2. Simultaneously add a small amount of solid sodium bicarbonate to both beakers.
Observation of Experimental Phenomena
- Vigorous bubbling (effervescence) occurs only in the right beaker (acetic acid); no bubbling occurs in the left beaker (ethanol).
Summary of Experimental Principles
- Acetic acid reacts with sodium bicarbonate to produce carbon dioxide gas (CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂↑); ethanol does not react with sodium bicarbonate under these conditions.

Prompt Grounding rubric:
level_1: Fewer than two beakers are shown, or the two liquids are not positioned as one on the left and one on the right, or no white granular solid resembling sodium bicarbonate is ever added to either beaker, or ethanol and acetic acid are not distinguishable as separate contents of the two beakers.
level_2: Two beakers sit side by side, but the ethanol ends up in the right beaker or the acetic acid ends up in the left beaker, contradicting the prompt's left/right assignment; or the solid is added to only one beaker, or it is added to the two beakers with a long, obvious delay between the two additions rather than as one coordinated action; or the two beakers' contents give no visual or contextual cue as to which liquid is which.
level_3: Two beakers are placed side by side on a table; the left beaker holds a clear liquid identifiable as ethanol per the prompt, the right holds a clear liquid identifiable as acetic acid; a white granular solid (sodium bicarbonate) is added into both beakers as part of the same continuous action, with the two additions occurring close together in time.
level_4: Everything in score 3 holds, and additionally the solid is delivered to both beakers with a similar motion and from a similar source (e.g., the same hand or tool) rather than by two very different actions; both beakers stay in their fixed left/right positions throughout; nothing else blocks the view of either beaker while the solid is being added.
level_5: Everything in score 4 holds, and additionally the two additions land on their respective liquid surfaces within about half a second of one another rather than being widely staggered; the two beakers look the same size and shape and sit level with each other; the camera does not pan, zoom, or reposition during the sequence; if any labels are shown, they are legible and attached to the correct beaker.

Scientific and Causal Correctness rubric:
level_1: No bubbling occurs in either beaker after the solid is added, or vigorous bubbling appears in the ethanol beaker, or the acetic acid beaker shows no bubbling at all, or either liquid changes color, or the solid fully dissolves in the acetic acid beaker with no gas evolution.
level_2: Bubbling occurs in only one beaker but it is the wrong one given what should happen, or bubbling appears in the ethanol beaker before or around the same time as in the acetic acid beaker, or the two beakers show visually indistinguishable levels of bubbling, or bubbling begins before the solid actually touches either liquid.
level_3: After the solid touches each liquid, bubbling appears only in the acetic acid (right) beaker; the ethanol (left) beaker shows no bubbling; in the acetic acid beaker, the solid is seen reacting (partially undissolved while gas is released) rather than merely dissolving away silently.
level_4: Everything in score 3 holds, and additionally the bubbling in the acetic acid beaker continues for at least several seconds rather than a single brief burst; the ethanol beaker never starts bubbling at any point in the clip; the added solid remains visibly undissolved in the ethanol beaker throughout.
level_5: Everything in score 4 holds, and additionally the acetic acid beaker shows clear effervescence, with bubbles rising to and disturbing the liquid surface, while the ethanol beaker shows no bubbles, no surface disturbance, and no cloudiness at any point after the solid is added.

Spatiotemporal Consistency rubric:
level_1: One of the beakers vanishes and reappears somewhere else in the frame, or a beaker's size or shape suddenly distorts, or the sodium bicarbonate solid appears inside a beaker with no visible path leading to it, or the room lighting flips abruptly between frames.
level_2: The beakers stay present but shift position or tilt inconsistently from frame to frame; the solid's path from source to beaker skips (e.g., it is in the hand in one frame and already inside the liquid in the next with no transit shown); background objects flicker or warp; the liquid surfaces reflect light inconsistently from one frame to the next.
level_3: Both beakers stay fixed in position and orientation throughout; the sodium bicarbonate travels along a continuous, visible path into each beaker rather than jumping there; each liquid surface stays calm except for the bubbling caused by the reaction in the acetic acid beaker; neither beaker's shape breaks or distorts.
level_4: Everything in score 3 holds, and additionally the solid's fall into each beaker follows a plausible downward or arcing path rather than floating or clipping through the beaker wall; the solid does not hover above the liquid before making contact.
level_5: Everything in score 4 holds, and additionally the two beakers remain visibly side by side, level with each other, and unrotated throughout, with no perceptible drift in their relative positions; the motion of the solid into each beaker is smooth and evenly paced rather than stuttering or skipping frames.