Domain: Natural Science — Chemistry
Target concept: The copper(II) aqua complex turns deep blue upon coordination with ammonia ligands.

Video generation prompt: Aqueous solution of copper(II) sulfate in a transparent beaker was slowly titrated with ammonia solution while being gently stirred.

Evaluation guide:
(i) Target concept: Ligand-induced d-d transition enhancement in copper(II) coordination complexes.
Minimum mechanism: The initial [Cu(H₂O)₆]²⁺ complex is pale blue (absorbing in the orange-red region). As ammonia is added, Cu²⁺ first forms a pale-blue Cu(OH)₂ precipitate right where the ammonia contacts the solution; continued ammonia addition redissolves this precipitate as H₂O ligands are progressively replaced by stronger-field NH₃ ligands, forming [Cu(NH₃)₄(H₂O)₂]²⁺. This increases Δ₀, shifting absorption to longer wavelengths and increasing the extinction coefficient → a deeper, clearer blue.
(ii)Storyline: Frame opens on a static shot of a transparent beaker holding a pale blue copper(II) sulfate solution → ammonia container enters frame or is already positioned above the beaker → first droplet/stream of ammonia contacts the solution surface → a brief, localized pale, cloudy patch (Cu(OH)₂) appears right at the point of contact → simultaneous initiation of gentle stirring motion → the cloudy patch redissolves and the surrounding solution deepens into a richer blue, spreading outward from the point of addition → deep blue color becomes uniform across the entire solution volume while addition and stirring continue → no bubbling or layering occurs, and any cloudiness fully clears by the end of addition; viewpoint remains fixed, front-facing, with the full beaker and tools continuously visible and unoccluded.

Manual:
Experimental Procedure
1. Place a transparent beaker containing aqueous copper(II) sulfate solution (initial light blue) on a stable surface.
2. Hold an ammonia solution container (e.g., dropper or burette) above the beaker.
3. Slowly add ammonia solution into the beaker while gently stirring the mixture with a glass rod.
Observation of Experimental Phenomena
As the first drops of ammonia contact the solution, a pale, cloudy blue patch forms briefly right where the ammonia lands; with continued dropwise addition and stirring, this cloudiness redissolves and the solution turns a clear, progressively deeper blue; by the end of the addition, the entire solution is uniformly deep blue and transparent, with no cloudiness left.
Summary of Experimental Principles
Copper(II) ions in water form the light-blue [Cu(H₂O)₆]²⁺ complex. The first ammonia added reacts with Cu²⁺ to precipitate pale-blue Cu(OH)₂ (Cu²⁺ + 2NH₃ + 2H₂O → Cu(OH)₂↓ + 2NH₄⁺); as more ammonia is added, this precipitate dissolves through stepwise ligand substitution to form the deep-blue [Cu(NH₃)₄(H₂O)₂]²⁺ complex (Cu(OH)₂ + 4NH₃ → [Cu(NH₃)₄(H₂O)₂]²⁺ + 2OH⁻).

Prompt Grounding rubric:
level_1: No transparent beaker is visible; no blue or colorless copper(II) sulfate solution is shown; no ammonia-delivery container (dropper, pipette, or burette) appears; no stirring rod or stirring motion is depicted; the titration action never begins.
level_2: A transparent beaker holding some liquid is visible, but the liquid is not blue (e.g., colorless, green, or brown); the ammonia container is missing or cannot be identified; no controlled addition of liquid from a separate container into the beaker occurs; no stirring rod or stirring motion is present.
level_3: A transparent beaker containing a visibly blue copper(II) sulfate solution is shown; a clearly identifiable ammonia-delivery container is positioned above or beside the beaker; liquid is seen being added from that container into the beaker; a stirring rod or similar tool visibly moves within the solution.
level_4: Everything required for the 3-point level is present, and in addition: the ammonia addition continues without interruption and lands inside the beaker rather than spilling past its rim; stirring continues at the same time as the addition; the ammonia container stays visible and recognizable in every frame while the addition is happening.
level_5: Everything required for the 4-point level is present, and in addition: the beaker, the ammonia container, and the stirring rod each keep the same position relative to one another for the whole shot; no object enters or leaves the frame partway through; the beaker's contents are never blocked from view while ammonia is added or while stirring occurs; the entire addition-and-stirring sequence plays out in one unbroken shot.

Scientific and Causal Correctness rubric:
level_1: No color or clarity change happens at all; or the final solution ends up an incorrect color (e.g., green, brown, purple, or colorless) instead of deep blue; or the solution stays cloudy/turbid the whole time with no return to clear blue; there is no visible relationship between the ammonia being added and any change in the liquid.
level_2: The initial solution is blue, but the outcome is scientifically wrong: a cloudy precipitate forms and never clears despite continued addition (the solution ends cloudy rather than deep blue and clear), or the solution's hue shifts to something other than blue (e.g., green or violet), or the color changes before any ammonia has touched the solution.
level_3: The solution starts pale blue; as the ammonia first touches the liquid, a paler, cloudy patch appears right at the point of contact; with continued dropwise addition and stirring, that cloudiness dissolves away and the solution becomes a clear, deeper blue; by the end of the addition no persistent cloudiness remains anywhere in the beaker.
level_4: Everything in the 3-point level holds, and in addition: the cloudy patch stays localized near where the ammonia enters rather than spreading through the whole beaker before it clears; the clearing and deepening of the blue color spreads outward evenly as stirring continues; no color besides shades of blue or pale cloudiness ever appears.
level_5: Everything in the 4-point level holds, and in addition: the change from cloudy patch to clear deep blue moves in one direction only, without flickering back and forth between cloudy and clear; by the final frame the entire visible solution is a uniform, transparent, deep blue with no cloudy patches or floating particles left anywhere.

Spatiotemporal Consistency rubric:
level_1: The beaker itself vanishes and reappears, or its position jumps between frames; the solution's fill level changes abruptly with no visible cause; the stirring rod jumps to a new spot or spins in a physically impossible way; the whole scene suddenly goes dark or flashes bright with no light source shown; the camera cuts or jumps to a different framing mid-action; the beaker's glass looks warped, cracked, or its rim floats free of the body.
level_2: The beaker stays visible but the liquid surface bulges or bends as though seen through a fisheye lens; the stirring motion stutters, freezing then jumping ahead; the ammonia stream or droplets blink in and out of existence rather than falling continuously; shadows on the beaker shift direction or length in ways inconsistent with one fixed light source.
level_3: The beaker keeps its shape and clarity throughout; the solution's surface stays smooth and undistorted; the stirring rod moves in one continuous, unbroken motion; the ammonia arrives as a continuous stream or as individual droplets falling smoothly, never skipping or teleporting; shadows cast by the beaker and rod stay pointed in one consistent direction for the whole sequence.
level_4: Everything in the 3-point level holds, and in addition: the stirring rod stays inside the beaker for its entire path; the ammonia stream lands only inside the beaker's mouth, never outside it; the rod never appears to pass in front of the beaker wall at a moment when it should logically be behind it.
level_5: Everything in the 4-point level holds, and in addition: the stirring rod swings with a natural arc and speed, never snapping instantly from one position to another; falling ammonia droplets curve downward under gravity rather than drifting sideways or upward; the liquid surface ripples and settles naturally in response to stirring and each new drop, without freezing mid-ripple or snapping instantly flat.