Domain: Engineering — Chemical Engineering
Target concept: Carbon steel

Video generation prompt: Immerse the carbon steel specimen in a transparent beaker containing 5% sulfuric acid solution, place it under ambient temperature conditions, and film the beaker for 24 hours.

Evaluation guide:
(i) Target concept: Acid-metal displacement reaction producing hydrogen gas and soluble ferrous sulfate.
Minimum mechanism: Carbon steel must be electrochemically active in acidic medium; H⁺ reduction must occur preferentially at cathodic sites on steel surface; dissolution must be heterogeneous and interface-limited (not bulk erosion); solution must remain undersaturated with respect to iron hydroxides.
(ii)Storyline: [Frame 0] Empty transparent beaker on flat surface → [Frame 1] Carbon steel specimen lowered into beaker → [Frame 2] Sulfuric acid solution poured in, submerging specimen completely → [Frame 3–10] Continuous bubble nucleation and vertical ascent from specimen surface only; no bubbling from walls or surface; specimen surface progressively dulls in immersed zone; liquid remains optically homogeneous; all objects retain fixed spatial relationships and consistent lighting; no perspective shift or motion artifact.

Manual:
Experimental Procedure
1. Place a clean carbon steel specimen into an empty transparent glass beaker.
2. Pour 5% sulfuric acid solution into the beaker until the specimen is fully immersed.
3. Position beaker under ambient room lighting and stationary background.
Observation of Experimental Phenomena
- Continuous stream of small, colorless gas bubbles emerges exclusively from the submerged surface of the carbon steel.
- Carbon steel surface becomes locally duller and darker, retaining metallic gray but losing specular reflectivity.
- Sulfuric acid solution stays clear and free of sediment, but gradually takes on a faint pale-green tint from dissolved ferrous sulfate (Fe²⁺) as corrosion proceeds over the 24 hours.
Summary of Experimental Principles
Carbon steel reacts with dilute sulfuric acid via redox reaction: Fe(s) + H₂SO₄(aq) → FeSO₄(aq) + H₂(g). Hydrogen gas evolution causes bubbling; iron dissolution leads to surface etching and loss of luster, without immediate rust formation due to acidic suppression of Fe³⁺ hydrolysis.

Prompt Grounding rubric:
level_1: None of the three required objects (the carbon steel specimen, the transparent beaker, and the sulfuric acid solution) appear together; no immersion of the specimen into liquid is shown.
level_2: At least one of the three objects appears (e.g., the beaker or the metal specimen), but the specimen is never placed into the beaker, the container isn't transparent or holds no visible liquid, or the pouring/placement order is missing or reversed.
level_3: The carbon steel specimen sits fully inside a transparent beaker of visible liquid; the specimen entering or resting inside the beaker is shown; the specimen, beaker, and acid solution are all present together in one continuous scene with no object cutting in or out.
level_4: Beyond the level-3 setup, the beaker stays in the same place on the surface for the whole clip; the specimen stays fully submerged with no part poking above the liquid or floating; the liquid surface stays level and unbroken; the specimen is not lifted out or re-inserted after the initial placement.
level_5: Beyond the level-4 setup, the specimen is clearly a separate object from the beaker wall, not merged or hidden behind it; the acid solution looks uniformly transparent, without artificial cloudiness or added tint at this stage; the beaker is a cylindrical container with a flat base and vertical walls; the specimen is a solid, roughly rectangular or cylindrical piece of matte gray metal; no duplicated or glitching copies of the beaker or specimen appear.

Scientific and Causal Correctness rubric:
level_1: No sign of corrosion appears anywhere: the carbon steel surface looks unchanged, the liquid shows no bubbles, no gas evolution, no surface darkening or etching; everything in the beaker stays static and inert for the whole clip.
level_2: A surface or liquid change happens, but not one consistent with acid attack on steel: for example the whole specimen changes color uniformly rather than just its submerged surface, the specimen rapidly crumbles apart, or bubbles are large and slow and clearly detached from the specimen's surface rather than forming right against the metal.
level_3: Small gas bubbles continuously rise from the submerged carbon steel surface and from nowhere else; the specimen's surface looks locally duller or darker where it sits in the acid, without yet showing rust-red color; the liquid is still clear with no yellow or brown tint and no floating flakes, consistent with early hydrogen evolution and iron dissolution.
level_4: Beyond the level-3 behavior, bubbles rise only from the submerged part of the specimen, never from the beaker walls or the liquid's open surface; bubbling doesn't stop and restart erratically; the surface dulling stays confined to the immersed portion; and later in the clip the liquid shows a faint, even pale-green tint from dissolved iron, rather than staying perfectly clear or turning cloudy, orange, or brown.
level_5: Beyond the level-4 behavior, bubbles are fine, numerous, and rise steadily from across the whole submerged surface; the once-shiny specimen surface visibly roughens and dulls further, losing essentially all of its remaining metallic sheen; no orange rust appears anywhere; the pale-green tint in the liquid develops gradually and stays even throughout the solution, with no sediment, no cloudiness, and no floating particles, matching dissolved ferrous sulfate rather than any rust or precipitate.

Spatiotemporal Consistency rubric:
level_1: The specimen, beaker, or liquid appears or disappears abruptly between frames; the specimen teleports into or out of the beaker; the beaker suddenly changes position or tips over with no transition; the overall lighting jumps to a very different brightness or color cast from one moment to the next; the liquid surface flickers or vanishes; the beaker or specimen shape breaks or glitches.
level_2: The specimen drifts or rotates on its own after being placed, with no physical cause; the beaker wobbles as if unsupported; bubble paths bend diagonally then snap vertical; the liquid surface ripples for no reason; shadows detach from their objects or point the wrong way.
level_3: The specimen stays inside the beaker and the beaker stays on the same stable surface for the whole clip; the liquid surface stays level and continuous; bubbles rise straight upward from the specimen; neither the specimen nor the beaker stretches, warps, or deforms; the lighting keeps the same angle, brightness, and softness from start to finish.
level_4: Beyond the level-3 behavior, the bubbles rise at a steady, believable speed rather than suddenly speeding up or slowing down; there's no frame stutter or duplicated frame; the specimen never appears to pass through the beaker wall; the camera never jumps or repositions; the background stays static and free of clutter.
level_5: Beyond the level-4 behavior, there are no skipped or frozen frames anywhere in the clip; the bubble streams stay straight, roughly parallel, and evenly spaced apart; the specimen shows no vibration or drifting motion; the beaker's glass reflects the room light consistently, with steady specular highlights and edge refraction that don't flicker or jump across the whole clip.