Domain: Natural Science — Chemistry
Target concept: The deep blue copper(II)-ammonia coordination complex forms in solution.

Video generation prompt: A glass beaker containing a pale blue copper(II) sulfate solution is being titrated with ammonia while gently swirled.

Evaluation guide:
(i) Target concept: Ligand-induced coordination complex formation in transition metal aqueous chemistry.
Minimum mechanism: Cu²⁺(aq) must be initially surrounded by H₂O ligands (giving pale blue [Cu(H₂O)₆]²⁺); NH₃ must displace H₂O stepwise to form [Cu(NH₃)₄]²⁺ (deep blue, square planar); the reaction requires direct molecular contact and mixing to overcome kinetic barriers; no oxidation state change or precipitation occurs.
(ii)Storyline: Frame 1: Static shot: beaker centered, filled with uniform pale blue liquid, no motion. → Titration begins: dropper enters frame, tip aligns above beaker mouth, first ammonia droplet contacts liquid surface. → Simultaneously, beaker starts gentle clockwise rotation; liquid surface tilts and forms dynamic meniscus. → Deep blue color appears *at the point of titrant impact*, then spreads radially and vertically via convective mixing. → Color intensifies uniformly with continued titration and swirling; final state is homogeneous deep blue liquid with no pale zones or interface lines. Perspective: fixed frontal-medium close-up (beaker occupies ≥60% frame height), top-down visibility of liquid surface and titrant stream, no occlusion of reaction zone.

Manual:
Experimental Procedure
1. Place a transparent glass beaker containing a pale blue aqueous copper(II) sulfate solution on a stable surface.
2. Using a dropper or burette, slowly add aqueous ammonia solution into the beaker while gently rotating the beaker clockwise with the other hand.
Observation of Experimental Phenomena
The pale blue solution gradually transforms into a deep, transparent blue color as ammonia is added and mixed; no precipitate forms; color change is uniform and progressive throughout the liquid volume.
Summary of Experimental Principles
Copper(II) ions form the deep blue [Cu(NH₃)₄]²⁺ tetraammine complex in aqueous solution upon coordination with ammonia ligands — a reversible ligand substitution reaction that shifts the d-d transition absorption band.

Prompt Grounding rubric:
level_1: No beaker present; no copper(II) sulfate solution visible; no ammonia reagent container shown; no titration action occurring; no swirling motion visible.
level_2: At least one of the following is present: a beaker, a pale blue liquid, or a dropper/burette; but no simultaneous presence of beaker + pale blue liquid + titration action + swirling motion; sequence of steps is absent or reversed.
level_3: Beaker containing a pale blue liquid is present; a titration tool (e.g., dropper or burette) is visibly dispensing liquid into the beaker; swirling motion of the beaker is visible; all core objects and actions are present but at least one spatial or sequential flaw exists (e.g., titrant added before beaker is shown, or swirling occurs only after titration ends).
level_4: Beaker containing pale blue liquid is present from start to end; titration tool dispenses liquid continuously into the beaker while it is being swirled; all three core elements (beaker + pale blue liquid + titration + swirling) co-occur in correct temporal order; no object appears/disappears abruptly; no spatial mismatch (e.g., titrant stream does not miss beaker); only non-core flaws allowed (e.g., minor hand occlusion, brief focus shift, non-distorting lighting change).
level_5: Beaker with pale blue liquid is continuously visible; titration tool dispenses liquid into the beaker throughout the entire video; swirling motion is continuous and synchronized with titration; titrant stream is fully visible and consistently directed into the beaker; no occlusion, no cut, no spatial discontinuity, no timing misalignment; all prompt-specified elements are present, correctly positioned, and co-occurring without interruption or deviation.

Scientific and Causal Correctness rubric:
level_1: No color change observed; liquid remains pale blue throughout or changes to an incorrect color (e.g., green, purple, yellow, colorless, or black); no deep blue appearance at any point; no transition from pale blue to deep blue.
level_2: Deep blue color appears but is not preceded by pale blue liquid; or pale blue liquid is present but deep blue never appears; or deep blue appears without titration action or swirling; or color change occurs in reverse order (deep blue → pale blue).
level_3: Pale blue liquid is visible at video start; titration action and swirling occur; deep blue color appears during titration; but deep blue either appears too early (before titrant contact), too late (after titration stops), or inconsistently (flickering, patchy, or localized only at surface without mixing).
level_4: Pale blue liquid is present at start; deep blue color emerges progressively *only during* active titration and swirling; deep blue spreads continuously and uniformly through the liquid volume as titration proceeds; no incorrect intermediate colors (e.g., no green, violet, or turbid gray); all color states are chemically plausible and temporally aligned with action.
level_5: Pale blue liquid is uniformly visible at frame 1; deep blue color begins *exactly at first visible contact* of titrant with liquid surface; deep blue intensifies smoothly and homogeneously throughout the liquid volume *only while titrant is being added and beaker is swirling*; no moment shows incorrect color, no lag between titrant entry and color onset, no spatial inconsistency (e.g., unmixed streaks or persistent pale zones), no fading or reversal; full causal fidelity: titrant addition + mixing → immediate and uniform deep blue complex formation.

Spatiotemporal Consistency rubric:
level_1: The beaker instantly jumps to a different spot on the countertop or changes size between consecutive frames, breaking away from the fixed footprint it held beneath the poised dropper/burette tip in frame 1; the liquid's top surface jumps to a different height or shape with no continuous swirl to cause it; the ammonia stream jumps from one position to another with no continuous path from the dropper tip down to the liquid; the glass beaker's wall visibly bends, cracks, or turns fluid mid-titration, something rigid laboratory glassware being hand-swirled cannot do.
level_2: At least two of the following occur: the beaker rotates by more than a quarter turn between two adjacent frames with no visible hand motion to explain it; the liquid's meniscus tilts in a direction that does not match the way the beaker is visibly swirling; the ammonia droplet or stream vanishes mid-air before reaching the liquid surface and reappears already inside the beaker; the clockwise swirl stops for over a second and then resumes at a different speed or in the opposite direction.
level_3: One clear spatiotemporal flaw is visible: for instance the beaker's outline flickers out of view for two or more consecutive frames while the ammonia stream and liquid remain visible, then the beaker reappears in the same spot; the ammonia stream briefly overshoots the beaker mouth and lands outside before correcting back into the beaker; or the swirl pauses completely for one sustained stretch while ammonia is still visibly being added. Aside from this single flaw, the beaker and its contents otherwise keep a coherent shape and position.
level_4: The beaker keeps a constant size, orientation, and position on the surface; the clockwise swirl is smooth and centered on the beaker's vertical axis, with the liquid's meniscus tilting and forming a vortex consistent with that rotation; the ammonia stream falls in an unbroken, gravity-directed line from the dropper tip into the liquid; at most one minor imperfection is allowed, such as a single frame of motion blur on the swirling hand that does not hide the beaker's position or the titrant's landing point.
level_5: Across every frame, the beaker's position, size, and orientation on the surface stay fixed except for the smooth, constant-speed clockwise swirl; the liquid's vortex and meniscus respond naturally and continuously to that swirl with no sudden jumps; the ammonia stream remains a single, unbroken, gravity-aligned thread visible from the dropper tip to the point where it enters the liquid; the beaker rim, body, and liquid surface never flicker, warp, or misalign from one frame to the next.