Domain: Natural Science — Chemistry
Target concept: Oxygen corrosion of steel

Video generation prompt: Immerse an iron nail into a saturated sodium chloride solution, seal the apparatus, and connect the tube to water in a beaker.

Evaluation guide:
(i) Target concept: Oxygen-driven electrochemical corrosion of iron in saline electrolyte, resulting in localized rust formation and pressure differential-induced water displacement.
Minimum mechanism: Presence of O₂, H₂O, and Cl⁻ ions enables anodic dissolution (Fe → Fe²⁺ + 2e⁻) and cathodic oxygen reduction (O₂ + 2H₂O + 4e⁻ → 4OH⁻); rust precipitates where Fe²⁺ meets OH⁻; O₂ depletion lowers headspace pressure, causing external atmospheric pressure to push water up tube.
(ii)Storyline: [Phase 1] Iron nail placed upright into clear liquid in container → [Phase 2] Lid sealed firmly, eliminating air exchange → [Phase 3] Tube visibly attached to lid outlet and positioned to contact water surface in adjacent beaker → [Phase 4] Rust initiates and accumulates only on immersed nail segment (not on air-exposed tip) → [Phase 5] Water level rises monotonically in beaker, beginning only after sealing is complete and tube is connected; all phases occur from fixed frontal viewpoint with no camera repositioning or occlusion.

Manual:
Experimental Procedure
1. Place an iron nail into a container filled with saturated sodium chloride solution.
2. Seal the container with a tight-fitting lid equipped with a gas-tight tube outlet.
3. Connect the tube to a beaker of water so the tube end just touches the water surface.
Observation of Experimental Phenomena
- Reddish-brown rust forms only on the submerged portion of the iron nail.
- Water rises steadily in the beaker through the tube after sealing.
Summary of Experimental Principles
Oxygen dissolved in the NaCl solution reacts with iron to form hydrated iron(III) oxide (rust); this consumes oxygen, lowering internal pressure and drawing water up the tube via atmospheric pressure.

Prompt Grounding rubric:
level_1: None of the four required elements (the iron nail, the saturated NaCl solution, the sealed container, and the tube leading to the water-filled beaker) appears at any point in the clip.
level_2: Only one of the four required elements appears (for example the nail alone, or the beaker of water alone); the container is open or has no lid; there is no tube at all; there is no visible connection between the container and the beaker.
level_3: Two or three of the four required elements appear together: for instance the nail and the NaCl solution are shown but the container is never sealed, or the container is sealed but no tube runs to the beaker; when all four elements do appear, the tube end sits below the beaker's water surface, or the tube is not visibly attached to the container, or the nail is not immersed in the solution.
level_4: All four elements are present and correctly arranged: the nail is immersed in the visible NaCl solution inside a sealed container with its upper portion exposed above the liquid surface, and a tube runs from the container to rest at the water surface of a separate beaker, matching the setup in the prompt, with the container and beaker shown together in one fixed view.
level_5: All four elements are present and arranged exactly as above, and additionally the seal shows no visible gap around the lid, the tube stays firmly attached to both the container outlet and the beaker rim without drooping or slipping, the nail sits upright and centered in the solution, and the container and beaker stay in the same spot throughout the clip.

Scientific and Causal Correctness rubric:
level_1: The nail stays a uniform metallic silver-gray the whole time (no color change, no bubbling, and no rust), and nothing in the scene suggests an oxygen-driven reaction is taking place.
level_2: The nail changes color, but not as expected (for instance it turns uniformly black, blue, or green rather than developing reddish-brown rust), or rust appears before the nail is immersed or on a part of the nail outside the liquid, or the water in the beaker rises or falls even though the tube is never connected.
level_3: Reddish-brown rust appears only on the submerged part of the nail and not on the dry part above the liquid, and the water level in the beaker does rise during the clip, but the rise happens in sudden jumps rather than gradually, or it starts before the tube is connected, or before the container is sealed.
level_4: Rust forms only on the submerged section of the nail, appearing granular and uneven rather than as a smooth coating; the water in the beaker climbs steadily and only begins climbing after the container is sealed and the tube is connected; the exposed part of the nail above the liquid stays rust-free; and there is no bubbling or color change in the solution itself.
level_5: The rust texture looks granular and stays attached to the nail rather than flaking off or floating in the solution; the water rises smoothly and only in one direction with no pause or backward dip; the solution itself stays clear with no color change or cloudiness; and no air pocket is visible interrupting the water's rise inside the tube.

Spatiotemporal Consistency rubric:
level_1: The nail suddenly appears in a different spot with no motion shown, the container or beaker vanishes and reappears, the tube disconnects and reconnects with no hand or cause visible, the lighting shifts dramatically between shots, or the water surface flickers or breaks apart unnaturally.
level_2: The nail's position within the container jumps by more than a third of its height between frames without smooth movement, the tube bends or kinks with no physical cause, the water's height in the beaker changes abruptly rather than gradually, the container's lid appears or disappears partway through the clip, or the shadow on the nail or container flips direction with no change in the light source.
level_3: There is one small flaw: the nail shifts slightly in position (less than a fifth of its height) without a fully smooth motion, or the tube wobbles briefly while the water is rising, or the water surface flickers for a moment; but the nail, container, tube, and beaker never disappear, jump to a new location, or break apart, and their positions relative to one another stay consistent.
level_4: The nail stays in the same spot within the solution, the tube keeps the same attachment points on the container and beaker, the lid stays fully seated, and the water level rises steadily rather than in jerks, with no part of the apparatus passing through another.
level_5: The water's surface rises smoothly and steadily with no visible shaking, wobble, or backward dip; the nail shows no drift or vibration in its position; the container and beaker keep sharp, stable edges in every frame without warping or misalignment; and the camera view holds completely still with no drift or zoom during the rise.