Domain: Natural Science — Chemistry
Target concept: Light the hydrogen gas outlet, and confirm that the flame is a pure pale blue, stable in shape, and produces no black smoke.

Video generation prompt: Demonstrate a chemical experiment using a hydrogen gas generator equipped with a tubing interface. Open the gas source and allow the gas to flow briefly for purging. Use a igniter to ignite the gas at the tubing interface. Show a steady gas release and the correct ignition sequence. Keep the procedure concise and coherent.

Evaluation guide:
(i) Target concept: Visual verification of safe, pure hydrogen combustion via controlled ignition of purified gas stream.
Minimum mechanism: Hydrogen must be flowing *before* ignition to purge air; ignition must occur *only at outlet*; combustion chemistry requires stoichiometric H₂–O₂ mixing to yield pale blue flame and zero soot.
(ii)Storyline: [Frame 0–2] Generator and tubing visible, valve opens → [Frame 3–4] Gas flows visibly from tubing (purging phase) → [Frame 5–6] Igniter approaches tubing outlet → [Frame 7] Igniter contacts/touches outlet → [Frame 8–10] Pale blue flame appears *exclusively* at outlet, remains steady and smokeless; all events occur within fixed frontal medium shot, no cutaways, no off-screen actions, flame origin locked to tubing geometry.

Manual:
Experimental Procedure
1. Show hydrogen gas generator with tubing interface; open gas source valve.
2. Observe brief gas release from tubing (purging).
3. Bring igniter to tubing outlet and ignite.
4. Observe flame at tubing outlet.
Observation of Experimental Phenomena
- Flame appears exclusively at tubing outlet.
- Flame color is pure pale blue.
- Flame shape is steady and conical.
- No black smoke is produced.
Summary of Experimental Principles
- Pure hydrogen combustion produces a pale blue flame due to complete oxidation: 2H₂ + O₂ → 2H₂O.
- A stable, smokeless pale blue flame confirms absence of air contamination and proper gas purity.

Prompt Grounding rubric:
level_1: No hydrogen gas generator visible; no tubing interface shown; no gas source valve or flow control element present; no igniter shown; no flame appears at any time.
level_2: Hydrogen gas generator and tubing interface are present, but gas source is not opened (no visible flow indication); igniter is present but not used; no flame appears; or flame appears without prior gas purging or without being at the tubing interface.
level_3: Hydrogen gas generator with tubing interface is visible; gas source is opened (tubing shows gas release, e.g., visible flow indicator like slight mist, vibration, or audible cue implied visually via context); igniter is brought to tubing interface and flame appears there; flame is present but its color, stability, or smoke emission is not verifiable due to occlusion, blur, or framing.
level_4: All prompt-specified objects present and correctly positioned: hydrogen gas generator with tubing interface, open gas source (tubing visibly releasing gas), igniter contacting or near tubing interface at ignition moment, flame appearing precisely at tubing interface; flame is continuous and located at correct spatial position; no object teleportation or insertion/deletion mid-sequence.
level_5: All elements of score 4 met, and the sequence is strictly followed in correct temporal order: (1) gas source opened → (2) brief gas release visible (purging) → (3) igniter applied to tubing interface → (4) flame ignites *only after* ignition action and *only at* tubing interface; no extraneous actions, no duplicated/missing steps, no misaligned spatial relationships (e.g., igniter never touches generator body, flame never appears on hand or background).

Scientific and Causal Correctness rubric:
level_1: Flame is absent or replaced by non-hydrogen combustion indicators: yellow/orange/red flame, black smoke, flickering instability, popping sounds implied visually (e.g., sudden expansion), or flame originates from wrong location (e.g., inside generator, hand, floor).
level_2: Flame appears but violates core chemical knowledge: color is not pale blue (e.g., clearly yellow, orange, or white); black smoke is present; flame shape is highly unstable (e.g., repeatedly extinguishing and reigniting without cause, or violently flaring); or flame appears *before* igniter contact or *without* gas flow.
level_3: Flame is pale blue and appears at the tubing outlet only after the igniter makes contact, but one or more of the following is unclear rather than clearly wrong: (a) absence of black smoke cannot be fully confirmed because the view is partly obscured or blurred, (b) flame stability over time is hard to judge due to motion blur or a shaky shot, (c) the gas-purging step before ignition is not clearly shown (e.g., it happens off-screen or too briefly to confirm).
level_4: Flame is pale blue, appears only at the tubing outlet, produces no black smoke, and stays visibly steady in shape throughout (no extinguishing, pulsing, or distorting); the gas release is clearly shown before ignition; ignition happens only after purging and only once the igniter touches the outlet; the full causal order (gas flow, then contact, then flame) is visible and unambiguous.
level_5: All conditions of score 4 are met, and every phenomenon is clearly visible at once without ambiguity: the pale blue color is easy to distinguish from the background, zero black smoke appears for the entire time the flame is shown, the flame's shape stays evenly steady with no visible deviation for a sustained stretch (several seconds, not just a fleeting instant), and there is no confusion about the flame's color, its location, or the order of purge-then-contact-then-flame.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal rupture: the generator or tubing disappears and reappears; the tubing changes length or bends into a different shape between frames with no cause; the flame jumps to a different location instantly; the whole scene switches between bright and dark with no visible cause; the camera cuts or zooms, breaking the fixed framing; the tubing detaches from the generator and reattaches with no hand or motion causing it.
level_2: The tubing at the outlet twists, slides, or changes shape without anything touching it; the igniter is still visibly short of the outlet when the flame already appears; the flame's size jumps suddenly with no matching change in gas flow; the faint glow the lit flame casts on the nearby tubing surface disappears or relocates to a different spot even though the flame itself has not moved; background objects shift relative to the generator with no camera motion.
level_3: The flame's base wavers slightly from side to side at the outlet rather than staying perfectly put; there is a brief flicker in how clearly the tubing is visible; overall scene brightness shifts slightly without affecting the flame's color; the igniter tip slightly overshoots the outlet just before the flame appears, but the generator, tubing, and igniter all stay continuously visible and in their expected places.
level_4: All objects keep a fixed spatial arrangement: the generator body, tubing outlet, and igniter tip stay in the same relative positions throughout; the flame's base stays visibly fixed at the tubing outlet with no drift to another spot; the glow the flame casts on the nearby tubing stays in the same place and at a steady brightness the whole time; there is no stutter, jump cut, or bending of the tubing; the igniter's approach motion is smooth and unhurried.
level_5: Every frame shows the same spatial layout of generator, tubing, and flame with zero visible deviation; the flame's base stays visibly anchored at the tubing outlet for the full duration with no perceptible drift in any direction; the glow cast on the tubing by the flame keeps a constant position and brightness from the moment the flame appears; the igniter's approach and withdrawal follow one smooth, continuous path with no sudden speed change or hesitation.