Domain: Natural Science — Physics
Target concept: In flame emission spectroscopy, sodium salts produce yellow light.

Video generation prompt: In the dimly lit laboratory, a Bunsen burner was burning with a blue flame, and a metal wire loop dipped in sodium salt was repeatedly inserted into and removed from the flame.

Evaluation guide:
(i) Target concept: Atomic emission from thermally excited sodium atoms in a reducing flame environment.
Minimum mechanism: Sodium salt must be thermally dissociated into gaseous Na atoms, which absorb thermal energy and emit yellow photons upon electron relaxation; requires direct contact between salt-coated loop and flame zone of sufficient temperature (>500°C) and reducing character to prevent oxide formation.
(ii)Storyline: [Frame 0–2] Dim lab setting establishes ambient low luminance; [Frame 3–4] Bunsen burner ignited, blue flame stabilizes at nozzle; [Frame 5–6] Metal wire loop dips into white crystalline sodium salt (visible granular adherence); [Frame 7–8] Loop enters blue flame → instantaneous yellow emission localized to tip; [Frame 9–10] Loop withdraws → yellow extinguishes, blue flame intact; [Frame 11–12] Loop re-dips (salt reapplied); [Frame 13–14] Loop re-enters → identical yellow emission; [All frames] Fixed frontal viewpoint, no occlusion, no lighting shift, no object teleportation.

Manual:
Experimental Procedure
1. In a dimly lit laboratory, ignite a Bunsen burner to produce a steady blue flame.
2. Dip a clean metal wire loop into solid sodium salt (white crystalline powder).
3. Insert the salt-coated loop into the blue flame, observe, withdraw, re-dip, and reinsert at least twice.
Observation of Experimental Phenomena
A vivid yellow light appears *only at the tip of the wire loop* while it is inside the blue flame; yellow vanishes immediately when loop is removed; blue flame remains unchanged elsewhere.
Summary of Experimental Principles
In flame emission spectroscopy, sodium atoms excited by flame heat emit photons predominantly at ~589 nm, producing characteristic yellow light.

Prompt Grounding rubric:
level_1: No Bunsen burner or flame is shown, or no metal wire loop is shown, or no sodium salt is shown being applied to the loop; the laboratory setting is not dim (e.g., bright daylight or fully unlit).
level_2: A Bunsen burner with flame is shown, but the flame is not blue in its baseline state; a wire loop appears but is never dipped into any visible salt-like substance, or is never inserted into the flame; the insertion/removal action happens off-camera or is only implied.
level_3: A Bunsen burner burning with a blue flame is shown in a dimly lit lab; a wire loop is visibly coated with white/crystalline salt before being inserted into the flame at least once and then withdrawn; only a single insertion-removal cycle is shown, not the repeated in-and-out action called for.
level_4: All elements from score 3 are present AND the loop is dipped, inserted, and withdrawn from the flame at least twice in an alternating sequence, with salt visibly re-applied to the loop between insertions; the whole sequence is captured in one continuous camera framing without cuts.
level_5: All elements from score 4 are present AND every dip-insert-withdraw cycle is fully visible and unoccluded (loop, salt, and flame all clearly in frame at each step), the loop's motion path into and out of the flame is unambiguous, and the dim laboratory background and burner remain the same static setup throughout with no missing or skipped step in the repeated sequence.

Scientific and Causal Correctness rubric:
level_1: No yellow coloration ever appears in the flame, or a yellow color is present continuously regardless of whether the loop is in the flame, indicating no causal link between the sodium salt and the color change.
level_2: Yellow coloration appears, but is not tied to the loop's position: e.g., the whole flame turns yellow rather than just the region around the loop tip, or yellow appears before the loop ever touches the flame, or the blue flame disappears entirely and is replaced by yellow rather than the yellow appearing as a localized addition.
level_3: Each time the loop enters the flame, a yellow color appears localized around the loop tip while the rest of the flame stays blue; when the loop is withdrawn, the yellow fades out rather than persisting indefinitely; but the effect is only clearly shown for one insertion, not repeated identically.
level_4: All elements from score 3 are present AND the same localized-yellow-appears / fades-on-withdrawal pattern repeats consistently across every insertion shown, with the yellow color visibly concentrated near the loop tip each time and the surrounding blue flame essentially undisturbed.
level_5: All elements from score 4 are present AND the yellow color's brightness and extent look essentially the same at every insertion (no insertion producing a noticeably weaker or stronger glow than another), the fade-out after withdrawal happens promptly (within roughly half a second, not lingering as an afterglow), and the blue flame's shape and brightness away from the loop stay visibly unaffected throughout.

Spatiotemporal Consistency rubric:
level_1: The wire loop appears inside the flame with no visible motion path leading it there; the flame or burner vanishes and reappears between frames; the room lighting jumps between dim and bright without cause; the loop's shape or size changes without any apparent reason.
level_2: The loop moves but appears unattached to any hand or holder; the flame's flicker pattern looks erratic or directionally inconsistent with normal combustion; shadows cast by the loop or burner don't match the flame as the apparent light source; the background lab setting shifts or warps slightly between frames.
level_3: The loop's position relative to the burner stays sensible throughout (it approaches and recedes from the same flame, not a different one); the room's dim ambient lighting stays roughly constant; the loop's insertion and withdrawal motion is continuous rather than jumping between positions, with only minor unevenness in speed.
level_4: All elements from score 3 are present AND the loop follows a smooth, consistent path toward and away from the flame on each cycle; the flame's height and general shape stay stable except for the expected localized yellow color change; there is no visible strobing, whole-frame flickering, or sudden brightness shift in the lab background.
level_5: All elements from score 4 are present AND the loop's motion shows natural acceleration and deceleration rather than constant robotic speed; the flame's blue portion continues to flicker in a plausible, gas-combustion-like way throughout without becoming rigid or frozen; shadows and reflections from the loop and burner move coherently with the loop's motion across every cycle shown.