Domain: Engineering — Chemical Engineering
Target concept: Copper Electrorefining

Video generation prompt: Set up the copper electrorefining apparatus, using impure copper sheets as the anode and pure copper sheets as the cathode, immersed in a 0.5 mol/L copper sulfate aqueous solution, ensuring that both electrodes are fully submerged and do not come into contact. Connect a 1.5 V DC power supply, maintain a stable current, and continuously record the setup for several hours.

Evaluation guide:
(i) Target concept: Electrolytic copper purification via anodic dissolution and cathodic deposition in CuSO₄ electrolyte.
Minimum mechanism: Cu(s) → Cu²⁺(aq) + 2e⁻ (anode oxidation); Cu²⁺(aq) + 2e⁻ → Cu(s) (cathode reduction); net mass transfer from anode to cathode without side reactions (no O₂/H₂ evolution, no contaminant deposition).
(ii)Storyline: Frame 1–2: Static shot showing container with pale blue solution and two vertically aligned copper sheets (anode rough/dull, cathode smooth/shiny), fully submerged, non-contacting. Frame 3–4: Wires attached (red to anode, black to cathode), connecting to labeled 1.5 V DC supply. Frame 5–10: Continuous observation: cathode surface gains uniform metallic layer (growing outward), anode surface recedes with distributed pitting; solution remains optically homogeneous, no bubbles or color shift; all spatial relationships preserved; viewpoint fixed, lighting stable.

Manual:
Experimental Procedure
1. Place impure copper sheet (anode) and pure copper sheet (cathode) vertically side-by-side in a transparent container filled with copper sulfate solution.
2. Ensure both electrodes are fully submerged and do not touch each other or container walls.
3. Connect red wire from 1.5 V DC power supply to impure copper anode; black wire to pure copper cathode.
Observation of Experimental Phenomena
- Cathode surface becomes progressively thicker and shinier.
- Anode surface becomes progressively thinner and rougher/pitted.
- Solution remains uniformly pale blue with no gas bubbles or precipitate.
Summary of Experimental Principles
This setup demonstrates copper electrorefining: at the impure anode, Cu metal is oxidized to Cu²⁺ ions and dissolves into solution, along with any more-reactive impurities (e.g., iron, nickel, zinc); less-reactive impurities (e.g., silver, gold) do not dissolve and instead settle at the bottom as anode slime. At the pure cathode, Cu²⁺ ions from solution are reduced back to Cu metal, so that purified copper migrates from the impure anode and deposits on the cathode.

Prompt Grounding rubric:
level_1: The container, copper electrodes, copper sulfate solution, DC power supply, and connecting wires are largely absent: for example, only an empty container or a single loose metal plate appears, with no wiring or power supply anywhere in the scene.
level_2: A transparent container with pale blue liquid appears and at least one copper sheet is visible, but the second sheet, the red/black wire pair, or the 1.5 V DC power supply is missing, or wires are shown lying loose beside the container rather than clipped to the electrodes.
level_3: Both copper sheets hang vertically in the same container of pale blue copper sulfate solution, fully submerged and not touching each other or the container walls; the 1.5 V DC power supply is present with a red wire running to one sheet and a black wire to the other.
level_4: All of score 3 holds, and the two sheets are visually distinguishable as the prompt calls for: one surface looking rough/matte (impure copper anode) and the other smooth/bright (pure copper cathode), with the red wire clipped to the rough anode, the black wire clipped to the smooth cathode, and the power supply's 1.5 V marking readable.
level_5: All of score 4 holds for the entire multi-hour recording: the rough anode and smooth cathode keep their distinct surface finishes, the solution stays a uniform pale blue across the full container, the two sheets never touch each other or the container walls, and the red-to-anode/black-to-cathode wiring and the container's position on screen stay unchanged from the first frame to the last.

Scientific and Causal Correctness rubric:
level_1: No sign of an electrochemical reaction: the anode and cathode surfaces look the same as when the recording started, or the solution's pale blue color changes for no visible physical reason (turns clear, dark, or cloudy) with no connection to what is happening at the electrodes.
level_2: Some surface change occurs but violates the expected roles of the two electrodes: for instance the anode also grows a deposit, or the cathode also thins/pits, or gas bubbles rise from one or both electrodes, or the solution turns green/brown/yellow instead of staying pale blue.
level_3: Over the recording, the cathode's surface visibly thickens and takes on a smoother, brighter finish, the anode's surface visibly thins and grows rougher/pitted, and the solution stays pale blue with no bubbles, cloudiness, or precipitate at either electrode.
level_4: All of score 3 holds, and the changes are directional and consistent with copper migrating from anode to cathode: the cathode's deposit builds outward layer by layer rather than appearing patchy or reversing, the anode's pitting spreads fairly evenly across its submerged face rather than sitting in one isolated spot, and the solution's clarity stays even across the whole container.
level_5: All of score 4 holds, and the deposition/dissolution pattern reflects the facing geometry of the two sheets: the cathode gains material mainly on the face pointing toward the anode, the anode loses material mainly on the face pointing toward the cathode, no visible flecks of dislodged copper drift free into the solution, and the pale blue color's intensity looks the same in the last frame as in the first.

Spatiotemporal Consistency rubric:
level_1: The container, copper sheets, or wires vanish and reappear between frames, the liquid level jumps up or down with no pouring or evaporation shown, the lighting abruptly flips between bright and dark with no source change to explain it, or the camera viewpoint suddenly cuts to a different angle with no pan or cut justifying the change.
level_2: The two copper sheets and the container keep their place overall, but something briefly glitches: a wire clip flickers in and out over a few frames, a sheet's edge warps or bends unnaturally for a moment, or the container's outline changes shape (e.g., a straight side turning curved) without any camera movement to explain it.
level_3: The container, both copper sheets, the power supply, and the wires stay in the same positions, sizes, and orientations across the whole recording; the liquid surface stays flat and level; nothing at the frame edges is cut off or clipped.
level_4: All of score 3 holds, and the submerged depth of each copper sheet relative to the liquid surface stays the same throughout (no sheet appears to rise or sink in the liquid), the red and black wires trace the same unbroken path from the power supply to their electrodes in every frame, and the container walls show a steady, consistent distortion of whatever is visible behind them.
level_5: All of score 4 holds, and the curve of the liquid surface where it meets the container wall stays smooth and even all the way around, the copper sheets' rough/smooth textures stay sharp rather than blurring out during any motion, and the cathode deposit and anode pitting progress continuously and gradually from frame to frame rather than the surface state jumping or repeating.