Domain: Engineering — Materials Science & Engineering
Target concept: Iron sheet exhibits a large number of bubbles and rapid corrosion, while the stainless steel sheet shows no significant changes.

Video generation prompt: A iron sheet, a stainless steel sheet, and two beakers containing equal volumes of dilute hydrochloric acid of the same concentration are placed side by side; the iron sheet is placed in the left beaker, and the stainless steel sheet is placed in the right beaker, observing the reactions in both beakers.

Evaluation guide:
(i) Target concept: Differential corrosion resistance due to electrochemical passivation in stainless steel vs. active dissolution in plain carbon/low-alloy iron.
Minimum mechanism: Iron must undergo oxidation (Fe → Fe²⁺ + 2e⁻) with concurrent H⁺ reduction (2H⁺ + 2e⁻ → H₂↑); stainless steel must sustain an intact Cr₂O₃-rich surface layer that blocks ion/electron transfer at the metal–acid interface.
(ii)Storyline: Frame 0–1: Static wide shot showing two beakers side-by-side, iron sheet above left beaker, stainless steel above right beaker. Frame 2–3: Sheets descend and enter liquids simultaneously (or within one frame interval). Frame 4–10: Left beaker exhibits progressive, continuous bubbling originating exclusively at iron sheet surface; right beaker remains optically static: no bubble nucleation, no sheet discoloration, no meniscus disturbance. Perspective: Fixed frontal orthographic-like viewpoint, centered on beaker midlines; full sheet and liquid surface must remain fully visible at all times; no occlusion by fingers, tools, or frame edges.

Manual:
Experimental Procedure
1. Place two identical beakers side-by-side. Fill each with equal volume of dilute hydrochloric acid.
2. Place iron sheet into left beaker. Place stainless steel sheet into right beaker.
3. Observe reactions for 10 seconds.
Observation of Experimental Phenomena
Left beaker: iron sheet produces continuous visible bubbling; surface shows rapid pitting/corrosion.
Right beaker: stainless steel sheet shows no bubbling and no visible surface change.
Summary of Experimental Principles
Iron reacts readily with dilute HCl, producing hydrogen gas (bubbles) and soluble FeCl₂, causing rapid corrosion. Stainless steel contains chromium that forms a passive oxide layer, preventing reaction with dilute HCl.

Prompt Grounding rubric:
level_1: No iron sheet, no stainless steel sheet, no beakers, and no dilute hydrochloric acid are visible; the objects shown are unrelated to the setup (e.g., only copper, only water, test tubes, or hands).
level_2: At least two of {iron sheet, stainless steel sheet, two beakers, dilute HCl} appear, but at least one is wrong or missing: e.g., a shiny sheet is present but isn't clearly iron or stainless steel, only one beaker is shown, or both sheets sit together in a single beaker.
level_3: The iron sheet, the stainless steel sheet, and two separate beakers each holding dilute hydrochloric acid are all present and correctly identified; the iron sheet sits in the left beaker and the stainless steel sheet sits in the right beaker, arranged side by side with a clear left/right split.
level_4: Level 3's correct identification and placement hold, and additionally both beakers hold visibly the same amount of clear liquid at the same fill level, both sheets are immersed to a similar depth, and no unrelated prop (tongs, gloves, a label) blocks the view of either sheet.
level_5: Level 4's clean setup holds, and additionally the iron sheet in the left beaker and the stainless sheet in the right beaker are never swapped, duplicated, or replaced with a different-looking sheet at any point in the clip, and no extra beaker or sheet is introduced partway through.

Scientific and Causal Correctness rubric:
level_1: Neither beaker shows any reaction; or both beakers bubble the same way; or the stainless steel sheet corrodes or bubbles instead of the iron sheet; or the iron sheet stays inert while the stainless steel sheet reacts.
level_2: Only one beaker shows any change, but the change is in the wrong beaker (bubbling appears around the stainless steel sheet rather than the iron sheet); or both beakers bubble with no visible difference in how much or how fast.
level_3: The left beaker's iron sheet shows ongoing bubbling and its surface visibly roughens, pits, or darkens; the right beaker's stainless steel sheet shows no bubbling and looks unchanged; however the bubbling is faint, intermittent, or only barely distinguishable from the stainless side.
level_4: Level 3's iron-bubbles/steel-stays-clean pattern holds clearly; the bubbles visibly originate from the iron sheet's own surface rather than the beaker walls or bottom; the stainless steel sheet shows no color change, haze, or etching and keeps its shiny metallic look throughout.
level_5: Level 4's contrast holds and is unmistakable: the iron sheet produces at least three simultaneous bubble streams that continue throughout the clip, while the stainless steel sheet and the liquid around it show no bubbling, haze, or surface change at any point, even briefly.

Spatiotemporal Consistency rubric:
level_1: The iron sheet, the stainless steel sheet, or a beaker is absent in one frame and simply present in the next with nothing shown moving it there; or the iron sheet is suddenly shown inside the right beaker (or vice versa); the room lighting jumps in brightness or direction with no cause; a sheet visibly bends, stretches, or gets cut off at its edge.
level_2: The beakers shift sideways by more than a third of the frame width between key moments; a sheet's orientation flips (e.g., from standing upright to lying flat) with no visible cause; the liquid surface flickers between calm and rippled within a couple of frames for no reason.
level_3: The left beaker with the iron sheet and the right beaker with the stainless sheet each stay in their own spot throughout, and neither sheet drifts out of its beaker or blends into the glass; the light source's direction and brightness stay the same from start to finish; nothing is abruptly hidden or revealed without a sheet or the liquid actually moving to cause it.
level_4: Level 3's steady positions and lighting hold, and additionally the bubbling builds up gradually (a single bubble first, then a growing stream) rather than starting all at once; no bubble detaches and shoots upward unrealistically fast; the liquid surface ripples smoothly as bubbles rise rather than jerking or freezing mid-motion.
level_5: Level 4's realistic bubble motion holds, and additionally the video plays back smoothly with no frozen or stuttering frames; the bubbling rate and bubble size stay fairly steady from frame to frame; the edges of the sheets and the rims of the beakers stay aligned without visibly jumping; the background doesn't suddenly shift depth or blur in a way that suggests unintended camera movement.