Domain: Natural Science — Physics
Target concept: Effervescent tablets dissolving in cold and hot water (comparison of effervescence rate)

Video generation prompt: Two identical transparent glass cups are placed side by side: one contains ice water, and the other is steaming. Two identical effervescent tablets are simultaneously dropped, one into each cup, from a stable frontal perspective.

Evaluation guide:
(i) Target concept: Temperature-dependent reaction kinetics in aqueous dissolution of effervescent compounds.
Minimum mechanism: CO₂ gas evolution requires aqueous-phase contact between acid and carbonate components; molecular collision frequency and energy increase with temperature, accelerating gas nucleation and release rate; thus hot water yields faster, more vigorous effervescence than cold water.
(ii)Storyline: Frame 1–2: Static shot showing two side-by-side transparent cups: left with ice cues (ice cubes/condensation), right with steam plume. Frame 3–4: Two identical tablets released from same height, descending in parallel. Frame 5: Simultaneous first-contact of tablets with respective liquid surfaces. Frame 6–8: Hot-cup bubbles emerge visibly before cold-cup bubbles; hot-cup bubble coverage expands rapidly while cold-cup remains sparse and delayed. Frame 9–10: Contrast in bubble density and spatial distribution remains unambiguous. Perspective: Fixed frontal view, no camera movement, no occlusion, full visibility of both cup interiors and tablet entry points.

Manual:
Experimental Procedure
1. Place two identical transparent glass cups side-by-side in frontal view.
2. Fill left cup with ice water (visible ice cubes or exterior condensation).
3. Fill right cup with steaming hot water (continuous upward vapor plume above surface).
4. Simultaneously drop one identical effervescent tablet into each cup from equal height.
Observation of Experimental Phenomena
- Bubbles appear earlier, denser, and more widely distributed in the hot-water cup.
- Bubbles appear later, sparser, and more localized in the ice-water cup.
Summary of Experimental Principles
- Dissolution rate increases with temperature: higher kinetic energy accelerates reaction between citric acid and sodium bicarbonate in tablet, producing CO₂ gas faster in hot water.

Prompt Grounding rubric:
level_1: No two transparent glass cups are visible; or no effervescent tablet is present; or the shot is not a stable frontal view; or the cups are not placed side by side; or neither cup shows any visual sign of its water temperature (no ice cubes/condensation in either cup and no steam plume above either cup); or the tablets are not dropped into the two cups at the same time.
level_2: Two transparent glass cups are present and side-by-side, and at least one tablet is visible, but: (a) only one of the two cups shows a visible temperature cue (e.g., ice cubes or condensation appear on one cup but no steam plume appears above the other, or vice versa), or (b) a tablet is dropped into only one of the two cups, or (c) the frontal perspective is broken (e.g., an oblique angle, a rotating camera, or a cut between the two cups).
level_3: Two identical transparent glass cups sit side-by-side in a stable frontal shot; one cup clearly shows ice cubes or condensation and the other clearly shows a continuous upward steam plume; one effervescent tablet drops into each cup, but the two drops are not aligned in time (e.g., one tablet enters its cup's water before the other, with no simultaneous splash).
level_4: All elements of 3-score are satisfied, and the two drops are synchronized: both tablets first touch their cup's water surface within the same brief visual moment (no visible lag between the two splashes); neither tablet nor cup is duplicated, deleted, or misplaced; both cups and both tablets keep their correct count, identity, and side-by-side spacing throughout.
level_5: All elements of 4-score are satisfied, and additionally: (a) both cups stay completely within the frame, with no cropping or camera shift; (b) the two tablets match each other in shape, size, and color; (c) nothing obscures either cup's interior (e.g., no glare, bloom, or blur that hides the moment bubbles start); (d) the frontal camera position stays perfectly fixed: no panning, tilting, zooming, or shifting viewpoint.

Scientific and Causal Correctness rubric:
level_1: No effervescence observed in either cup; or effervescence appears identically intense in both cups; or effervescence occurs before tablet contact; or bubbles appear only in cold cup while hot cup shows none, or vice versa contrary to scientific expectation.
level_2: Effervescence occurs in both cups, but: (a) onset timing is identical in both (no observable difference in speed), or (b) bubble volume/coverage is indistinguishable between cups, or (c) bubbles appear in wrong cup (e.g., vigorous bubbling only in ice water cup, absent in steaming cup).
level_3: Effervescence begins in both cups after tablet contact; visible bubble formation is present in both; but the rate difference is detectable: one cup shows earlier and denser bubble emergence (more bubbles covering larger area of liquid surface sooner), consistent with faster dissolution in hot water; however, the *direction* of difference is not visually unambiguous (e.g., cold cup shows some early bubbles too, or hot cup's steam plume obscures initial bubbling).
level_4: All elements of 3-score are satisfied, and the contrast is unambiguous: hot-water cup exhibits significantly earlier onset (bubbles appear visibly before cold-water cup), greater bubble density (more bubbles per unit surface area), and broader spatial spread (bubbles cover larger portion of liquid surface), all while cold-water cup shows delayed, sparser, and more localized bubbling; no reversal or contradiction of this pattern.
level_5: All elements of 4-score are satisfied, and additionally: (a) bubble morphology is physically appropriate (spherical, rising, non-coalescing during early phase); (b) no bubble generation occurs outside liquid volume (e.g., no bubbles floating in air or adhering to dry cup wall above waterline); (c) dissolution progress is monotonic: bubbling in each cup keeps building or holding steady rather than dying out and restarting after onset; (d) no visual confound (e.g., steam mist mistaken for bubbles, or ice melt turbulence mistaken for effervescence).

Spatiotemporal Consistency rubric:
level_1: The two cups jump to a different position or spacing between frames; or a tablet skips straight from mid-air into the water with no visible fall; or the glare/highlight pattern on the glass or liquid surface suddenly relocates or disappears with no change in camera framing; or a cup's outline changes shape between frames (e.g., a cylindrical cup appears conical); or one of the two cups vanishes from the shot and later reappears.
level_2: Cup and tablet positions are mostly preserved, but: (a) one cup visibly slides sideways or up/down between frames, breaking the side-by-side layout; (b) a tablet's descent is jerky or skips positions instead of falling in one continuous motion; (c) the ice cup's ice cubes/condensation or the hot cup's steam plume abruptly appears, disappears, or shifts location without a physical cause; (d) the liquid level in either cup jumps up or down between frames with no matching cause such as splashing from tablet entry; (e) a shadow cast by a cup or tablet changes direction or noticeably changes intensity between frames with no corresponding change in lighting or camera position.
level_3: The two cups keep the same side-by-side layout throughout; each tablet falls along a single continuous downward path into its own cup; both liquid surfaces stay level and at a constant height except for the momentary disturbance from tablet entry; the ice cup's ice cubes/condensation and the hot cup's steam plume stay visibly present and in roughly the same place throughout (neither vanishes nor jumps location); shadows and highlights cast by the cups and tablets stay consistent in direction and relative intensity throughout; no cup or tablet edge tears, splits from, or fuses with the background; a slightly wavering steam wisp or a faint wobble in the tablet's outline as it falls is acceptable as long as the tablet's position and the instant it touches the water stay clearly visible.
level_4: All elements of 3-score are satisfied, and additionally: (a) each tablet's fall, its contact with the water surface, and the first appearance of bubbles are shown clearly enough that the exact moment of contact is not in doubt; (b) each liquid surface stays visually calm apart from the tablet-entry splash and the bubbles rising afterward, no unrelated rippling; (c) the sequence plays with no skipped or repeated frames that would confuse the cup-to-cup timing comparison; (d) the glass of both cups keeps the same degree of transparency throughout (neither cup suddenly looks more frosted or clearer than before).
level_5: All elements of 4-score are satisfied, and additionally: (a) each tablet falls in a straight vertical line with no sideways drift, descending at a visibly constant rate; (b) any glare or highlight visible on the glass or liquid surface of each cup stays in a consistent position relative to that cup as the camera and scene remain still; (c) any background object visible behind or between the two cups lines up consistently with both cups from frame to frame, with no shifting or doubling; (d) the bubbles rising in both cups move upward smoothly and continuously, without flickering, freezing, or jumping between positions.