Domain: Natural Science — Chemistry
Target concept: An iron nail is placed in a blue copper sulfate solution (iron displaces copper).

Video generation prompt: Immerse a clean iron nail into a transparent glass beaker containing blue copper sulfate solution, and record its changes over time without disturbance.

Evaluation guide:
(i) Target concept: Single displacement redox reaction where solid iron reduces aqueous Cu²⁺ ions to solid copper metal, which deposits on the iron surface.
Minimum mechanism: Aqueous Cu²⁺ must be present (blue color), iron must be in direct contact with solution, electron transfer must occur spontaneously (Fe⁰ → Fe²⁺ + 2e⁻; Cu²⁺ + 2e⁻ → Cu⁰), and deposited copper must remain adherent and insoluble under conditions.
(ii)Storyline: [Frame 0] Iron nail fully above liquid, beaker filled with uniform blue solution. → [Immersion phase] Nail descends vertically, entering solution without splash or turbulence; tip submerges first. → [Stabilization] Nail comes to rest fully submerged; liquid surface settles to stillness. → [Reaction onset] Reddish-brown coating appears progressively on submerged nail surface, beginning at bottom and spreading upward; no change to solution color or clarity. → [Steady state] Coating remains stable, confined to submerged zone; no gas, heat, or motion artifacts; viewpoint remains fixed frontal, showing full nail and beaker interior without obstruction.

Manual:
Experimental Procedure
1. Place a clean, dry iron nail vertically into a transparent glass beaker.
2. Pour blue copper sulfate solution into the beaker until the nail is fully submerged.
3. Hold the beaker steady; do not stir, shake, or disturb for the duration of observation.
Observation of Experimental Phenomena
- The originally silvery-gray iron nail develops a continuous, adherent reddish-brown coating exclusively on its submerged portion.
- The blue color of the copper sulfate solution remains unchanged in hue and transparency.
Summary of Experimental Principles
Iron displaces copper from copper sulfate solution due to higher reactivity, forming iron sulfate and depositing elemental copper on the nail surface: Fe + CuSO₄ → FeSO₄ + Cu.

Prompt Grounding rubric:
level_1: No iron nail appears anywhere; no clear glass beaker is shown; the liquid inside is never blue; the nail is never placed into any liquid; the scene doesn't read as a chemistry demonstration at all.
level_2: An iron nail, a glass beaker, or a blue liquid shows up, but not all three together in one coherent setup; the nail is shown beside the beaker rather than inside it; or the container is opaque, a different material, or the wrong shape (e.g., a plastic cup or a flask instead of a beaker).
level_3: A silvery-gray metal nail, an upright transparent glass beaker, and a visibly blue liquid filling that beaker are all present together; the nail sits fully below the liquid surface rather than resting on the rim or standing outside the beaker; no hand, tool, or label blocks the view of this core setup.
level_4: Everything required for score 3 holds, and in addition the nail is centered within the beaker and visible from head to tip, the beaker rests on a flat, steady surface, the liquid surface sits still and level with no ripples suggesting it was just disturbed, and the camera holds a fixed front-on framing without panning, tilting, or zooming.
level_5: Everything required for score 4 holds, and in addition the nail hangs vertically with its head up and tip down, the beaker's glass is free of smudges, condensation, or reflections that would block the view inside, the liquid sits at a consistent, level height with no overflow, and no stray object (drips, bubbles, labels) appears anywhere in the frame at any point.

Scientific and Causal Correctness rubric:
level_1: No color or surface change happens at all: the nail stays silvery-gray and the solution stays uniformly blue for the whole clip, with nothing suggesting a reaction is underway.
level_2: Either the nail changes or the solution changes, but not both, and not in the right way: e.g., the nail turns green instead of reddish-brown, or the blue solution fades toward pale yellow; or what appears on the nail looks like flaking debris, floating particles, or gas bubbles rather than an adherent metallic coating.
level_3: A continuous, adherent reddish-brown coating forms on the nail, confined to the part that was underwater; the solution stays visibly blue with no fading or cloudiness; no other color (green, black, white) shows up on the nail or in the liquid; the coating is absent at the very start and only appears after the nail has been immersed.
level_4: Building on the 3-point bar, the reddish-brown coating stays limited to the submerged segment of the nail and never creeps onto the part of the nail above the liquid surface; the blue solution keeps a uniform color and clarity with no gradient, settling debris, or floating residue.
level_5: Building on the 4-point bar, the coating has a dull, fine-grained look rather than a shiny, crystalline, or metallic sheen; the original nail surface shows no pitting, dissolving, or corrosion beneath the coating; none of the reddish-brown color bleeds outward into the surrounding liquid; the coating never appears and then fades away again.

Spatiotemporal Consistency rubric:
level_1: The nail jumps to a different position or angle between frames with no motion connecting them; the beaker changes position or orientation abruptly; the liquid surface disappears or jumps to a different level with no visible cause; the lighting swings drastically from one frame to the next; the edges of the nail or beaker flicker or dissolve momentarily.
level_2: The nail partly vanishes and reappears across frames; the beaker wobbles or rotates in a way nothing in the scene explains; the liquid's meniscus looks inconsistent from frame to frame, or a ripple appears suddenly with no source; a shadow changes direction or disappears with no change in lighting to explain it; the motion overall looks jerky or stutters.
level_3: The nail stays fully inside the beaker throughout; the beaker itself doesn't shift position on its surface; the liquid surface stays level and unbroken; neither the nail nor the beaker warps, stretches, or deforms; the lighting and the direction of shadows stay the same from frame to frame; any motion (like the nail settling) looks smooth and physically reasonable.
level_4: Building on the 3-point bar, the nail's position relative to the center of the beaker stays fixed with no sideways drift or rotation; the liquid surface stays essentially still with no visible flow or fresh disturbance; the camera framing doesn't visibly shift in perspective from one frame to the next; the nail's edges stay sharp and consistent rather than smearing or trailing inconsistently with how slowly it was placed.
level_5: Building on the 4-point bar, the nail's head and tip keep the correct relative size and sharpness throughout, with no part of the nail or beaker appearing to bend or warp as if seen through a distorted lens; the static parts of the scene (the beaker, the background, the resting nail) look the same in every frame with nothing flickering or strobing; the overall front-to-back depth relationships in the shot stay consistent throughout.