Domain: Engineering — Civil & Environmental Engineering
Target concept: Red to colorless

Video generation prompt: Cyanide-containing electroplating wastewater is introduced into a transparent electrolytic cell and treated with pyridine-barbituric acid reagent; titanium electrodes are then inserted into the solution and a stable current is applied.

Evaluation guide:
(i) Target concept: Electrochemical (anodic) oxidative decolorization of the red pyridine-barbituric acid–cyanide complex at a titanium electrode, demonstrating destructive treatment of cyanide in electroplating wastewater.
Minimum mechanism: Free cyanide in the wastewater must first react with pyridine-barbituric acid to form a red chromophore; titanium electrodes must then be inserted and a stable current applied; anodic oxidation must degrade the cyanide and the red chromophore itself, so the red color fades toward colorless only once current is flowing. With no current, the red color must persist unchanged.
(ii)Storyline: Frame 1–2: Wastewater visible in transparent cell. Frame 3–4: Pyridine-barbituric acid added; red color develops uniformly through the solution. Frame 5–6: Titanium electrodes inserted into the red solution. Frame 7–8: Power supply connected and current begins flowing (indicator lit/wires taut). Frame 9–10: Red color fades progressively, beginning near the electrode surfaces and spreading outward, ending in a colorless (or near-colorless) solution that remains stable. Fixed frontal viewpoint throughout; no cuts or perspective shifts; all events occur within the same continuous scene.

Manual:
Experimental Procedure
1. Pour cyanide-containing electroplating wastewater into a transparent electrolytic cell.
2. Add pyridine-barbituric acid reagent to the solution; the solution turns red.
3. Insert two titanium electrodes into the red solution.
4. Connect the electrodes to a DC power supply and apply a stable current.
Observation of Experimental Phenomena
The red color persists unchanged as long as no current flows. Once current is applied, the red color fades progressively toward colorless, beginning near the electrode surfaces and spreading through the solution.
Summary of Experimental Principles
Free cyanide first reacts with pyridine-barbituric acid to form a red chromophore. Anodic oxidation at the titanium electrode then degrades the cyanide and the red chromophore itself, bleaching the solution from red to colorless — demonstrating electrochemical destruction of cyanide in the wastewater.

Prompt Grounding rubric:
level_1: None of the four required elements appear anywhere in the clip: no transparent cell with wastewater, no pyridine-barbituric acid being added, no titanium electrodes, and no current/power supply shown connected.
level_2: Only one of the four elements appears (e.g. only the transparent cell with liquid, or only electrodes shown already inserted with nothing establishing the wastewater, reagent, or current), with the rest missing or performed in an unrecognizable way.
level_3: All four elements appear in the prompt's order: wastewater sits in a transparent cell, pyridine-barbituric acid is added to that same cell, titanium electrodes are then inserted into the solution, and a power supply is connected and shows current flowing (e.g. lit indicator or taut leads), even if some detail like electrode material or reagent delivery form is ambiguous.
level_4: Everything required for the 3-point level holds, and the objects are clearly identifiable in type: the cell is unambiguously transparent, the electrodes look like the described metallic titanium rods rather than glass, plastic, or an unrelated tool, the reagent enters as a liquid stream or drop rather than powder or gas, and every action happens to the same single cell with no cut to a different container.
level_5: Everything required for the 4-point level holds, and the spatial placement stays fully consistent throughout: both electrodes remain fully immersed and connected to visible leads for the entire current-application phase, the reagent is never re-added or duplicated, and no extra unlabeled containers, electrodes, or reagent bottles appear anywhere in frame to confuse which vessel is being treated.

Scientific and Causal Correctness rubric:
level_1: The solution never turns red after the reagent is added, so there is nothing to bleach, or a red color appears but stays constant and never fades at any point after current is applied, or the wrong hue (blue, green, orange) appears instead of red before treatment.
level_2: A red color forms after reagent addition as expected, but it fades or vanishes before current is ever applied, or fading happens with no current source connected at all, or the red reappears after fading in a way inconsistent with a one-way destructive oxidation.
level_3: Red forms only after the pyridine-barbituric acid is added, and it visibly fades toward colorless only once the current is switched on and flowing, but the fading looks uniform or instantaneous across the whole cell rather than starting near the electrodes, so the causal link to electrolysis is not tightly shown.
level_4: Everything required for the 3-point level holds, and the fading visibly begins at or near the titanium electrode surfaces and spreads outward through the solution, with the loss of color visibly accelerating the longer the current runs, and no fading occurs in any interval where the current is shown interrupted.
level_5: Everything required for the 4-point level holds, and the solution ends up essentially colorless (not merely paler) by the end of the clip, the fading rate visibly tracks the current being applied continuously (steady fade, no unexplained plateaus or sudden jumps), and no red returns once decolorization begins.

Spatiotemporal Consistency rubric:
level_1: The transparent cell's shape or position jumps between shots, the titanium electrodes appear already fully inserted with no visible insertion motion, the reagent appears already mixed into the solution with no visible addition, the red color disappears in a single frame with no gradual fade at all, the room lighting swaps abruptly (e.g., bright to dark) with no visible cause, or the camera cuts away or rotates instead of holding one fixed frontal view.
level_2: The electrodes wobble or reorient with no hand or mount visibly supporting them, the reagent stream breaks apart or jumps partway into the solution, the fading of red happens as a hard-edged wipe across the frame instead of a soft gradient, or the power-supply indicator switches on/off with no matching change in the fading rate.
level_3: The cell, electrodes, and solution keep consistent size, shape, and position across the whole clip; the electrodes enter the solution with a smooth, visible insertion motion; the reagent enters as a continuous droplet or stream; and the red-to-colorless fade spreads gradually through the liquid rather than jumping between frames.
level_4: Everything required for the 3-point level holds, and the fade shows physically believable diffusion: decolorization visibly starts near the electrode surfaces and spreads outward through convection rather than bleaching everywhere at once, the liquid surface stays undisturbed except where the reagent or electrodes enter it, and the electrodes' immersion depth stays constant once inserted, with no bobbing or sinking.
level_5: Everything required for the 4-point level holds, and the camera holds one fixed frontal framing for the entire clip with no drift, zoom, or tilt; the solution's transparency and the electrodes' reflections stay coherent and unchanging except for the fading color itself; and the rate of fading tracks smoothly with how long the current has been applied, with no freezing or sudden jumps in the decolorization progress.