Domain: Natural Science — Chemistry
Target concept: Iron(III) ions react with the thiocyanate ion to form a blood-red coordination complex.

Video generation prompt: In a transparent beaker, the aqueous solution of thiocyanate was added dropwise to the aqueous solution of iron(III), while gently swirling to ensure mixing.

Evaluation guide:
(i) Target concept: Formation of a soluble, intensely colored coordination complex via ion association in aqueous phase.
Minimum mechanism: Iron(III) must be in the +3 oxidation state and present as the hexaaquo ion ([Fe(H₂O)₆]³⁺); thiocyanate must be present as the SCN⁻ anion; ligand substitution must occur rapidly in solution without hydrolysis or precipitation; the resulting complex is stable under ambient conditions and owes its intense blood-red color to a ligand-to-metal charge-transfer (LMCT) transition, not a d-d transition.
(ii)Storyline: Frame 1–2: Static shot of beaker with pale yellow solution. Frame 3–4: Dropper enters top of frame, aligned over beaker center. Frame 5: First droplet detaches and falls vertically. Frame 6: Droplet contacts surface → localized red nucleation. Frame 7–8: Swirling begins → red region expands radially and homogenizes. Frame 9–10: Fully red, uniform solution with stable meniscus and consistent lighting. Perspective: Fixed frontal view, eye-level, shallow depth of field focusing on beaker mid-height; no occlusion of solution surface or droplet path; background neutral and non-distracting.

Manual:
Experimental Procedure
1. Place a transparent beaker containing a pale yellow aqueous iron(III) solution on a stable surface.
2. Hold a dropper filled with clear aqueous thiocyanate solution directly above the beaker.
3. Release one droplet into the solution, then immediately begin gentle circular swirling of the beaker.
Observation of Experimental Phenomena
A localized blood-red color appears at the droplet impact site and spreads uniformly through the solution during swirling, resulting in a homogeneous blood-red aqueous mixture.
Summary of Experimental Principles
Iron(III) ions react with thiocyanate ions to form the [Fe(SCN)]²⁺ coordination complex, which exhibits an intense blood-red color in aqueous solution.

Prompt Grounding rubric:
level_1: No transparent beaker appears, the iron(III) solution or the thiocyanate solution is missing entirely, or neither a dropwise addition nor any swirling is ever shown.
level_2: A beaker with some liquid and a dropper with some liquid are both present, but neither liquid has a color or cue that identifies it as the iron(III) solution or the thiocyanate solution, or a drop is released but no swirling ever follows it.
level_3: A transparent beaker holds a pale yellow or light amber liquid consistent with an iron(III) solution; a dropper above the beaker holds a clear liquid consistent with a thiocyanate solution; the dropper releases liquid into the beaker, and swirling of the beaker begins sometime after a drop lands.
level_4: All of score 3, plus the beaker stays still while the drop is added, swirling starts only after the first drop reaches the surface, the dropper tip sits directly over the open beaker with nothing blocking it, and the two liquids look visibly different from each other before they mix.
level_5: All of score 4, plus the dropper releases one visible, roughly spherical drop that is airborne briefly before it lands, swirling begins right after that landing with no cut or pause in between, and the hand-to-beaker positioning stays consistent for the whole sequence.

Scientific and Causal Correctness rubric:
level_1: No red color ever appears, the solution's starting color never changes, or the mixture turns a color other than red (blue, green, purple, brown, etc.) throughout.
level_2: A color change happens but it is the wrong one (orange, yellow, pink, violet, black, or gray instead of blood-red), or a red color shows up only on the surface of the falling drop and never spreads into the solution, or red only shows up after swirling has already stopped.
level_3: A blood-red color appears in the liquid after a drop lands and spreads outward from where it landed; the red stays within the liquid itself rather than smeared on the glass or dropper, and the pale yellow/amber background color is visibly overtaken by red as mixing proceeds.
level_4: All of score 3, plus no red appears anywhere before the drop actually touches the liquid, the red region keeps growing steadily while swirling continues without breaking apart, fading, or stopping and restarting, and no in-between color like rust-orange or burgundy takes over the mixing zone.
level_5: All of score 4, plus the final mixed region is a uniform, fully saturated blood-red with no leftover streaks of the original yellow/amber color, the red tone reads as blood-red rather than shifted toward orange or purple, and no cloudiness or visible solid ever appears at any point.

Spatiotemporal Consistency rubric:
level_1: The beaker or the falling drop disappears and reappears, the liquid's level inside the beaker jumps between frames, the light falling on the beaker suddenly brightens or dims with no visible cause, or the liquid's surface tears or warps in an unnatural way.
level_2: The beaker's position shifts abruptly between frames, the drop appears mid-air with no visible release from the dropper, the swirling starts or stops with sudden jerky speed changes, or the reflections on the liquid surface look inconsistent from one frame to the next.
level_3: The beaker stays in the same spot with a steady viewpoint; the drop falls in a continuous path from the dropper tip down to the surface; the swirling moves in one steady direction; the liquid surface moves the way a real liquid would while swirling, without flickering or losing its edges.
level_4: All of score 3, plus the drop stays intact and round until it hits the surface, the beaker does not tilt beyond what a normal hand swirling it would do, and the liquid's surface distortion changes smoothly rather than snapping flat or freezing.
level_5: All of score 4, plus the whole sequence plays as one continuous shot with no cuts, the dropper tip stays centered above the beaker opening throughout, the beaker's base stays visibly planted on the surface, and the liquid volume looks constant with no sudden overflow or disappearance.