Domain: Natural Science — Physics
Target concept: Deposition

Video generation prompt: Place a small amount of iodine vapor in a sealed transparent glass tube, and cool one end of the glass tube with an ice-water bath.

Evaluation guide:
(i) Target concept: Deposition as a direct phase transition from gas to solid without passing through liquid phase.
Minimum mechanism: Iodine vapor must be present in thermodynamic equilibrium above its triple point (~114°C at 12 kPa); localized cooling below triple point temperature (~114°C) at tube end induces supersaturation and nucleation of solid iodine crystals; vapor pressure gradient drives mass transport toward colder region.
(ii)Storyline: [Phase 1: Setup] Sealed transparent tube contains uniform purple-violet iodine vapor. [Phase 2: Trigger] Ice-water bath contacts one tube end; no delay, no pre-cooling. [Phase 3: Response] Within observable timeframe, dark gray/black crystals nucleate and grow only at cooled end; vapor density visibly depletes adjacent to deposit. [Phase 4: Contrast] Sharp spatial demarcation between purple-violet vapor zone (warm end) and crystalline deposit zone (cooled end); no intermediate liquid phase or mist. [Visibility constraint] Entire tube must remain fully in frame; cooled end must be unobstructed and clearly distinguishable from warm end; no angle distortion that compresses or elongates tube ends.

Manual:
Experimental Procedure
1. Place a small amount of solid iodine in a clean dry glass tube.
2. Seal both ends of the tube hermetically.
3. Gently warm the tube until iodine sublimes fully into visible purple-violet vapor.
4. Immediately place one end of the sealed tube into an ice-water bath.
Observation of Experimental Phenomena
A dark gray or black crystalline deposit forms exclusively at the cooled end of the tube, while purple-violet iodine vapor remains visible in the warmer portion.
Summary of Experimental Principles
Iodine undergoes deposition (gas → solid) when cooled below its triple point; the temperature gradient across the tube drives vapor transport and selective phase change at the coldest surface.

Prompt Grounding rubric:
level_1: None of the three required elements is visible: no sealed transparent tube, no purple-violet iodine vapor inside it, and no ice-water bath touching either end.
level_2: Only one or two of the required elements appear together, or they appear incorrectly: e.g., the tube is present but open or opaque rather than sealed and transparent; the gas inside is colorless or a different hue than the purple-violet expected of iodine vapor; or an ice-water bath appears somewhere in the shot but never touches the tube.
level_3: A sealed transparent tube containing purple-violet iodine vapor is shown, and an ice-water bath touches one end of that tube; all three required elements (sealed tube, purple-violet vapor, ice-water bath in contact with one end) are present, regardless of how the scene was assembled beforehand.
level_4: All score 3 conditions hold, AND the ice-water bath touches exactly one end of the tube, never both ends or the middle; the purple-violet vapor fills the tube's interior rather than sitting in one small pocket; the tube stays upright without tipping; nothing blocks the view of either tube end.
level_5: All score 4 conditions hold, AND the tube stays centered and fully visible for the whole clip; the vapor's purple-violet color looks even along the tube's length before cooling begins; the ice-water bath keeps touching the same single end without sliding away; the camera never zooms, pans, or cuts away from the tube.

Scientific and Causal Correctness rubric:
level_1: The tube looks the same at the end as at the start: still uniform purple-violet vapor throughout, with no dark crystals forming at either end and no visible effect from the cooling.
level_2: Some solid material appears, but it fails basic checks for this phenomenon: crystals form at the warm end instead of the cooled end; the deposit's color is wrong for iodine (e.g., white, yellow, or orange rather than dark gray or black); the purple-violet vapor disappears with no crystals appearing anywhere; or crystals are already visible before the ice-water bath ever touches the tube.
level_3: Dark gray or black crystals form only at the cooled end of the tube after the ice-water bath makes contact; purple-violet vapor is still visible in the warmer part of the tube; the boundary between the remaining vapor and the new crystals is a distinct, localized region near the cooled end.
level_4: All score 3 conditions hold, AND no crystals appear on the warm end or anywhere else along the tube walls; the purple-violet vapor visibly thins near the cooled end as crystals grow there; once formed, crystals do not melt back into vapor; the color contrast between violet vapor and dark crystals stays sharp throughout.
level_5: All score 4 conditions hold, AND crystal growth begins only after the ice-water bath is already touching the tube, not before; the crystals grow inward from the cooled end as a continuous front rather than appearing all at once; the vapor-filled region shrinks steadily toward the warm end as crystals form; no liquid droplets or misty condensation appear at any point, consistent with a direct gas-to-solid transition.

Spatiotemporal Consistency rubric:
level_1: The tube's position or angle changes abruptly between one frame and the next with nothing to explain it; the purple-violet vapor or the ice-water bath vanishes and reappears; the tube itself changes shape or appears to break apart without cause; or the lighting on the scene shifts abruptly (e.g., a sudden flash, or the scene suddenly going darker or brighter) with no connection to the cooling process.
level_2: The tube visibly shifts position or rotates by more than roughly 30 degrees within a couple of frames with no physical cause; the ice-water bath moves relative to the tube's end between frames; the amount of visible vapor jumps up or down abruptly instead of changing gradually; a crystal deposit appears, vanishes, then reappears at the same spot in later frames; or the shadow the tube casts shifts direction with no matching change in the light source.
level_3: The tube's position stays essentially the same across the clip, with only slight jitter (less than roughly 10% of the frame's height); the vapor thins out smoothly as crystals form, without sudden jumps in how much vapor is visible; the ice-water bath's contact point may shift very slightly but never separates from the tube; the tube, vapor, and bath never disappear from any frame.
level_4: All score 3 conditions hold, AND the point where the ice-water bath touches the tube stays fixed for the whole clip; the vapor recedes and the crystal deposit grows smoothly rather than in jumps; the deposit is never hidden by the bath and then suddenly revealed; the scene's overall brightness stays steady rather than flickering.
level_5: All score 4 conditions hold, AND the tube shows no visible drift in position from the first frame to the last; the boundary between vapor and crystal deposit advances at a steady, unbroken pace from the cooled end toward the warm end; the ice-water bath's visible surface moves only in small, physically plausible ripples; the clip shows no strobing, freezing, or repeated frames during the deposition process.