Domain: Natural Science — Chemistry
Target concept: Electrolytic refining of copper

Video generation prompt: The electrolytic cell contains a copper sulfate solution. Impure copper serves as the anode and is connected to the positive terminal of the power supply, while pure copper serves as the cathode and is connected to the negative terminal of the power supply. After applying electricity, keep the ammeter and both electrodes fully in frame throughout.

Evaluation guide:
(i) Target concept: Electrolytic purification of copper via selective electrode reactions in aqueous CuSO₄.
Minimum mechanism: Presence of mobile Cu²⁺ ions in solution; redox potential difference enabling preferential copper dissolution at anode and deposition at cathode; external circuit providing electron pathway; ammeter detecting resulting current.
(ii)Storyline: [Frame 0–2] Static setup: glass cell with blue solution, impure Cu anode (dull, uneven surface) and pure Cu cathode (smooth, shiny) immersed side-by-side; wires connect anode→positive, cathode→negative; ammeter in series with needle at zero. [Frame 3–6] Circuit closure: needle begins smooth rightward deflection; anode surface shows onset of pitting; cathode surface begins subtle darkening at interface. [Frame 7–10] Steady state: needle held deflected; anode visibly thinner with exposed grain boundaries; cathode coated with uniform, lustrous reddish-brown copper layer; solution remains clear blue with no gas bubbles or precipitate. All events occur from fixed frontal viewpoint; no cuts, pans, or zooms; occlusion and lighting remain physically coherent.

Manual:
Experimental Procedure
1. Place impure copper plate as anode and pure copper plate as cathode into copper sulfate solution inside glass electrolytic cell.
2. Connect anode to positive terminal and cathode to negative terminal of DC power supply.
3. Close circuit and observe ammeter needle.
Observation of Experimental Phenomena
- Ammeter needle deflects from zero, confirming current flow.
- Impure copper anode gradually thins and develops pits/residue.
- Pure copper cathode gains a smooth, reddish-brown copper deposit.
Summary of Experimental Principles
Electrolytic refining relies on selective oxidation of impure copper at the anode (Cu → Cu²⁺ + 2e⁻) and reduction of Cu²⁺ ions onto pure copper cathode (Cu²⁺ + 2e⁻ → Cu), purifying copper via controlled electrochemical transfer.

Prompt Grounding rubric:
level_1: No electrolytic cell visible; no copper sulfate solution shown; no impure copper anode or pure copper cathode present; no power supply terminals visible; no ammeter displayed.
level_2: Electrolytic cell container is present but contains incorrect liquid (e.g., water, colorless liquid, or opaque suspension); at least one electrode is present but wrong material (e.g., iron, graphite, or unlabeled metal); power supply or ammeter is partially visible but disconnected or mislabeled.
level_3: Electrolytic cell with visible blue liquid (copper sulfate solution) is present; impure copper anode and pure copper cathode are both present and placed inside the solution; power supply terminals are visible and connected: positive terminal linked to anode, negative to cathode; ammeter is present in circuit and shows a needle, but needle position is static (no deflection observed).
level_4: All elements from 3-score are present and correctly configured; ammeter needle is visibly deflected from zero position during the video, indicating current flow; spatial arrangement shows anode and cathode side-by-side in same solution, fixed viewpoint, no electrode displacement or removal.
level_5: All elements from 4-score are present; ammeter needle deflection is continuous and unambiguous throughout the visible duration; anode visibly diminishes in mass (surface roughening, pitting, or thinning) while cathode gains uniform copper deposit (darker reddish-brown layer, smooth growth), all within single fixed scene without cuts or repositioning.

Scientific and Causal Correctness rubric:
level_1: The electrochemistry breaks down entirely: the ammeter needle deflects even though no continuous current path is completed, or it deflects while neither electrode shows any resulting change for the whole run; the roles are inverted from what Faraday's law requires: the impure-copper anode appears to gain material while the pure-copper cathode appears to lose material; or gas bubbles form at either electrode (copper electrorefining in CuSO₄ should stay bubble-free).
level_2: Current flows and one electrode shows some change, but the science is only partly right: the amount of visible anode thinning and cathode deposit growth are grossly mismatched over the same stretch of time (violating charge conservation); or the cathode deposit forms as scattered specks rather than a coherent adherent layer; or a colored precipitate (e.g., a green or white solid) appears in the solution that is inconsistent with a pure Cu/CuSO₄ system.
level_3: Ammeter needle deflects from zero, confirming current flow; the impure-copper anode shows the beginning of surface pitting/roughening and the pure-copper cathode shows the beginning of a thin darker deposit, consistent with Cu → Cu²⁺ + 2e⁻ at the anode and Cu²⁺ + 2e⁻ → Cu at the cathode; no gas evolution or precipitate appears; no contradictory state change occurs (cathode does not thin, anode does not gain a deposit).
level_4: All from 3-score satisfied; anode shows clearer physical degradation (surface pitting, uneven thinning, or dark residue shedding) consistent with continued oxidation, and cathode shows a growing, uniform reddish-brown copper layer consistent with continued reduction; the rate of anode material loss and cathode deposit growth stay visually proportional to each other throughout; no bubbling, discoloration, or precipitate inconsistent with the pure Cu/CuSO₄ system.
level_5: All from 4-score satisfied; anode degradation and cathode deposit growth occur synchronously with the ammeter's deflection (visible change tracks with current flow rather than starting arbitrarily before or after it); the copper deposit forms exclusively on the cathode face that fronts the anode, matching the field geometry between the two plates, not on its back or sides; no competing phenomena (gas evolution, non-copper precipitate, or corrosion products) appear anywhere in the cell.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal breaks: the impure copper anode or pure copper cathode plate shows up in a different position or tilt from one frame to the next with no continuous path connecting the two; the ammeter needle jumps straight from one reading to a different one with no sweep in between; the blue solution's fill level in the cell changes abruptly between frames; the camera cuts to a different angle, framing, or zoom partway through the sequence.
level_2: Moderate breaks: the anode or cathode plate drifts, tilts, or rotates slightly between frames without a continuous motion path; the ammeter needle advances in visible steps rather than one smooth sweep; the solution surface ripples inconsistently frame to frame; the pitted patch on the anode or the reddish deposit patch on the cathode relocates to a different spot on the same electrode without a visible growth path connecting the two positions.
level_3: The anode plate, cathode plate, ammeter, and connecting wires hold the same positions relative to the cell and to one another for the entire sequence; neither electrode disappears, duplicates, or swaps sides of the cell; the ammeter needle sweeps continuously with no jumps or reversals; the solution surface stays calm with no unexplained turbulence; the illumination on the cell and electrodes does not change abruptly partway through the video.
level_4: All from 3-score satisfied; the anode surface and the growing cathode deposit show only the fine continuous change expected of a live reaction (e.g., subtle shimmer on the forming copper layer, gentle convection currents visible in the solution) rather than jumps; no frame-to-frame strobing, warping, or sudden change in perspective.
level_5: All from 4-score satisfied; timing is coherent throughout: the ammeter needle begins deflecting no later than the moment the circuit is shown closed and stays deflected without pause; the cathode's copper deposit thickens smoothly frame-by-frame with no sudden appearance of a finished layer; the apparent depth of the electrodes stays consistent with the solution's meniscus with no swimming/parallax error; background elements such as the lab bench and wiring stay fixed and consistently occluded by the foreground cell throughout.