Domain: Natural Science — Chemistry
Target concept: Sodium metal reacts with water

Video generation prompt: A beaker containing an appropriate amount of water with phenolphthalein solution is placed, and a small piece of metallic sodium is introduced into the water using tweezers.

Evaluation guide:
(i) Target concept: Alkaline product formation via alkali metal–water redox reaction.
Minimum mechanism: Sodium must be elemental (not oxide/hydride), water must be neutral solvent, phenolphthalein must be present and functional (pH-sensitive), and reaction must produce hydroxide ions sufficient to exceed pH ~8.2 for colorimetric activation.
(ii)Storyline: [Frame 0–1] Static shot: beaker with pink/purple liquid, tweezers entering frame holding sodium. [Frame 2–3] Tweezers lower sodium toward liquid surface; sodium remains solid, silvery-white, intact. [Frame 4] Sodium contacts liquid; immediate fizzing/bubbling originates at interface. [Frame 5–6] Sodium moves, shrinks, and vanishes; bubbling continues but diminishes. [Frame 7–8] Bubbling ceases; pink/purple color intensifies and spreads uniformly upward. [Frame 9] Final stable pink/purple solution with no sodium residue. Perspective: Fixed frontal view, shallow depth of field emphasizing beaker center; no occlusion of sodium during reaction; full visibility of liquid surface and beaker interior throughout.

Manual:
Experimental Procedure
1. Place a clear glass beaker containing water with phenolphthalein (pink/purple solution) on a stable surface.
2. Using metal tweezers, grasp a single small piece of silvery-white metallic sodium.
3. Lower the sodium into the solution until it contacts the liquid surface, then release.
Observation of Experimental Phenomena
- Sodium moves rapidly across or sinks in water while fizzing vigorously.
- Colorless gas bubbles form exclusively at sodium surface.
- Sodium shrinks and disappears completely.
- Solution turns uniformly pink/purple after sodium vanishes.
Summary of Experimental Principles
Sodium reacts exothermically with water: 2Na + 2H₂O → 2NaOH + H₂↑. The NaOH produced makes the solution alkaline, turning phenolphthalein pink/purple.

Prompt Grounding rubric:
level_1: No beaker present; no water visible; no phenolphthalein solution observable (i.e., no pink/purple hue in liquid); no metallic sodium object shown; no tweezers present; no action of placing sodium into liquid occurs.
level_2: Beaker is present and contains a liquid, but the liquid shows no pink/purple color (i.e., phenolphthalein absent or unactivated); sodium object is present but not handled with tweezers; sodium is not placed into the liquid: it appears static outside or falls without tool-mediated placement.
level_3: Beaker present with liquid showing pink/purple color (indicating phenolphthalein solution); tweezers are present and visibly hold a silvery-white metallic sodium piece; sodium is placed into the liquid (contact between sodium and liquid occurs) and remains fully submerged at initiation; all required objects (beaker, water+phenolphthalein, sodium, tweezers) are present and correctly typed.
level_4: All conditions for score 3 satisfied; additionally: sodium is placed *only* using tweezers (no fingers, no dropping from height, no pre-submerged state); beaker remains stationary throughout; liquid fills beaker to a visibly moderate level (neither empty nor overflowing); sodium piece is single, small, and solid (not powdered, not multiple pieces, not pre-dissolved).
level_5: All conditions for score 4 satisfied; additionally: tweezers release sodium *at the liquid surface*, followed immediately by full submersion; sodium maintains intact solid form for ≥1 visual frame before any reaction onset; beaker is transparent glass with visible meniscus and no occluding labels/condensation; no extraneous objects (e.g., gloves, hands beyond tweezers, lab coat sleeves) enter frame.

Scientific and Causal Correctness rubric:
level_1: No color change occurs; liquid remains colorless throughout; sodium shows no motion, melting, or disappearance; no gas evolution (bubbling, fizzing, or surface disturbance); no heat-induced visual effect (e.g., steam, shimmer, distortion).
level_2: Liquid remains colorless; sodium either vanishes instantly on contact or remains inert and unmoving; if bubbling occurs, it is decoupled from sodium location (e.g., bubbles appear away from sodium) or persists after sodium disappears; no pink color ever appears.
level_3: Liquid is initially colorless, then turns pink/purple *after* sodium contacts water and begins reacting; sodium moves rapidly across surface or sinks while fizzing; visible gas bubbles originate *exclusively from sodium surface* during its presence; sodium shrinks in size or disappears completely before pink color fully develops.
level_4: All conditions for score 3 satisfied; additionally: pink/purple color appears *only after* sodium has fully disappeared or ceased visible motion; bubbling stops *before* color change completes; no yellow/orange flame, no explosion, no splashing that ejects liquid from beaker; sodium never turns black or forms crust before dissolution.
level_5: All conditions for score 4 satisfied; additionally: pink/purple color spreads uniformly from reaction site upward through liquid column (no isolated patches or bottom-only staining); bubbling intensity decreases monotonically as sodium diminishes; no residual undissolved fragments or floating residue; color transition begins within 1 visual segment after sodium vanishes and completes before video ends.

Spatiotemporal Consistency rubric:
level_1: Beaker teleports or changes position/orientation abruptly; sodium jumps or reappears at new location without motion path; liquid surface distorts discontinuously (e.g., sudden height change, split meniscus); lighting shifts mid-sequence (e.g., shadow vanishes then reappears); tweezers disconnect from sodium mid-action.
level_2: Beaker wobbles or rotates >15 degrees without physical cause; sodium exhibits non-physical motion (e.g., levitation, rigid rotation without torque, acceleration without force); liquid surface ripples persist identically across ≥3 consecutive frames then vanish without decay; tweezers move independently of hand/arm motion (e.g., float, jerk, or scale inconsistently).
level_3: Beaker remains fixed in frame with stable orientation; sodium moves continuously from tweezers to liquid surface with smooth trajectory; liquid surface deforms gradually upon sodium impact and recovers partially before bubbling begins; lighting and shadows remain consistent in direction and intensity; no object flickers, vanishes, or reappears.
level_4: All conditions for score 3 satisfied; additionally: sodium motion path is uninterrupted and confined within beaker’s vertical plane; liquid meniscus remains intact and continuous (no tearing, shearing, or pixelated breakage); no inter-frame object warping (e.g., stretching, squashing, morphing); no temporal reversal or stutter (e.g., same bubble frame repeated).
level_5: All conditions for score 4 satisfied; additionally: spatial relationships preserved exactly; tweezers tip stays adjacent to sodium until release; sodium remains fully within beaker’s field-of-view from first appearance to final dissolution; liquid surface deformation evolves smoothly frame-to-frame with no skipped or duplicated states; no parallax jump between foreground (tweezers/sodium) and background (beaker rim).