Domain: Natural Science — Atmospheric Science
Target concept: Nitrogen Dioxide–Dinitrogen Tetroxide Equilibrium: Monomer–Dimer Structural Transformation

Video generation prompt: A sealed transparent glass tube containing nitrogen dioxide gas was alternately immersed in an ice-water bath and a warm water bath under continuous camera observation.

Evaluation guide:
(i) Target concept: Reversible monomer-dimer equilibrium governed by Le Chatelier"s principle under thermal perturbation.
Minimum mechanism: Gas must be enclosed in rigid, impermeable, optically transparent container; thermal baths must impose distinct, sustained temperature conditions; color change must reflect population shift between NO₂ (absorbs visible light strongly) and N₂O₄ (weakly absorbing); no chemical decomposition or side reactions occur.
(ii)Storyline: [Frame 0–3] Tube fully immersed in ice-water bath → gas gradually lightens → stabilization in pale yellow-brown state. [Frame 4–6] Tube lifted and moved laterally → no color change during transit. [Frame 7–10] Tube fully immersed in warm water bath → gas gradually darkens → stabilization in reddish-brown state. Perspective: Fixed frontal camera, centered on tube midsection, capturing full tube length and bath interface; no occlusion; lighting front-diffused to avoid glare on glass; background neutral and static.

Manual:
Experimental Procedure
1. Place a sealed transparent glass tube filled with nitrogen dioxide gas into an ice-water bath.
2. Observe color change for ~3 seconds.
3. Remove tube and place it into a warm water bath.
4. Observe color change for ~3 seconds.
Observation of Experimental Phenomena
When immersed in ice-water bath: gas color lightens to pale yellow-brown or straw color.
When immersed in warm water bath: gas color darkens to reddish-brown.
Summary of Experimental Principles
NO₂ (brown, monomeric) and N₂O₄ (colorless, dimeric) exist in temperature-dependent equilibrium: cooling favors exothermic dimerization (N₂O₄), lightening color; heating favors endothermic dissociation (NO₂), darkening color.

Prompt Grounding rubric:
level_1: No sealed transparent glass tube holding a brownish gas is shown; no ice-water bath and no warm-water bath appear on screen; the tube is never lowered into either bath; the footage is not a single continuous camera view of this setup (e.g., only a still frame, text, or an unrelated apparatus is shown instead).
level_2: A glass tube, a water bath, or a brownish gas appears, but the setup is assembled wrong: the tube is open at the top or too fogged/opaque to see the gas inside; the gas is missing or a color unlike NO₂ (e.g., colorless or vividly green/purple); the two baths cannot be told apart by temperature (e.g., both look like plain still water with no ice or warmth cue); the tube sits beside a bath rather than being placed into it; or the camera cuts to a different angle partway through.
level_3: A sealed transparent glass tube holding a brownish gas is centered in frame; an ice-water bath (ice cubes or condensation visible on its container) and a warm-water bath (clearly warmer-toned water, no ice) are both present in the same continuous shot; the tube is placed into each bath in turn; the camera holds one unbroken framing with no cutaways, but the order of the two immersions may be reversed, simultaneous, or otherwise unclear rather than clearly ice-bath-then-warm-bath.
level_4: Everything required for a 3 is present, and the sequence follows the prompt's order: the tube is lowered fully into the ice-water bath and held there, withdrawn, then lowered fully into the warm-water bath and held there, with no overlap between the two immersions and neither step skipped; during each immersion the tube stays at the same position relative to that bath's rim rather than drifting sideways or jumping to a new spot between shots.
level_5: Everything required for a 4 is present, and the tube's entry into and exit from each bath traces one smooth downward-then-upward path with no sudden repositioning or unexplained change in height; the ice-water bath keeps its ice/condensation visible for the whole time the tube is in it, and the warm-water bath stays visibly free of ice for the whole time the tube is in it; the tube's tilt and depth relative to the bath rim stay constant from the start to the end of each immersion; the camera itself never re-centers, re-zooms, or refocuses across the two segments.

Scientific and Causal Correctness rubric:
level_1: The gas stays one constant shade throughout both baths (e.g., always colorless, always deep purple, or always bright green) with no visible change at all; or the gas visibly changes color while the tube is touching neither bath; or the color the tube shows is outside the NO₂/N₂O₄ brown-to-pale-yellow family (e.g., blue, green, or violet) regardless of which bath it is in.
level_2: The gas does show two different colors tied to the two baths, but the direction is backwards from real NO₂/N₂O₄ chemistry: the tube looks paler/straw-colored after the warm-water immersion and darker reddish-brown after the ice-water immersion; or a color shift happens well after bath contact rather than during it; or the tube's interior appears to show liquid droplets or frost rather than gas; or the color switches instantly with no visible build-up.
level_3: The gas inside the tube is darker reddish-brown while immersed in the warm-water bath and lighter pale-yellow or straw-colored while immersed in the ice-water bath; each color appears only while the tube is in contact with its matching bath; the tube's interior shows only gas, with no droplets or frost forming inside it.
level_4: Everything required for a 3 is present, and the two color states stay mutually exclusive: no single frame shows both the darker reddish-brown and the pale straw color inside the tube outside of a brief transition moment; once the pale ice-water color is reached it does not spontaneously darken again before the tube moves to the warm bath, and the reverse holds too; no glass reflection or lighting glare is mistaken for a change in the gas's own color.
level_5: Everything required for a 4 is present, and the color change is gradual and one-directional within each bath segment: the reddish-brown visibly deepens over the course of the warm-water immersion, and the straw color visibly clears over the course of the ice-water immersion, rather than snapping between two fixed shades; only hues along the NO₂/N₂O₄ brown-to-pale-yellow range ever appear, with no violet, green, or blue tint at any point; the tube's interior stays evenly lit enough that the viewer is clearly seeing the gas's own color change rather than a shadow.

Spatiotemporal Consistency rubric:
level_1: The tube appears in the warm bath and then in the ice bath (or vice versa) with no visible movement between them, as if it teleported; the gas inside vanishes from view and reappears with no cause; either bath's water surface warps or ripples with no tube contact to explain it; the overall light source or color tone of the scene switches abruptly between the two bath segments; the tube changes orientation (e.g., flips over) with no hand or support visibly moving it; the edges of the tabletop or bath containers change shape between frames.
level_2: The tube shakes or wobbles more than a hand placing it into water would explain; ripples on a bath's surface keep going long after the tube has stopped moving in it; the tube's reflection on the glass or water changes abruptly between two frames while the tube itself stays still; the tube's shadow jumps to a new position without the tube moving; playback stutters so the immersion motion skips steps.
level_3: The tube is never seen jumping between locations or disappearing; it moves continuously from outside a bath to fully submerged and back out; the gas fills the tube's visible volume evenly rather than appearing in disconnected patches; the room lighting keeps the same brightness and color across both the ice-water and warm-water segments; the bath containers and any visible background objects (table, stand, etc.) keep the same arrangement relative to each other throughout; neither the tube nor the baths show any tearing or warping of their outlines.
level_4: Everything required for a 3 is present, and the tube's path into each bath is a controlled, roughly vertical lowering rather than a sideways or diagonal drop; the depth to which the tube sinks is similar in both the ice-water and warm-water segments; the tube's glass wall never appears to pass through a bath's water surface without displacing it; reflections of the tube on the water shift in step with the tube's own movement rather than sliding independently of it.
level_5: Everything required for a 4 is present, and the timing supports cause and effect: the color inside the tube only begins to change after the tube is shown entering the bath, never before contact; the fully darkened or fully pale color is reached only once the tube is completely submerged, not while it is still partway in; when the tube is lifted out of a bath, its color trend stops progressing further rather than continuing to intensify after it has left the water; the tube's motion shows no sudden overshoot or backward snap, and its outline stays as sharp as its actual speed of movement would allow.