Domain: Natural Science — Physics
Target concept: Copper ions that produce characteristic colors in flame tests

Video generation prompt: In the laboratory, a metal wire loop immersed in a copper salt solution was heated for several seconds in a Bunsen burner flame.

Evaluation guide:
(i) Target concept: Flame test identification of copper ions via characteristic flame emission.
Minimum mechanism: Heat from the Bunsen burner flame thermally excites copper species carried on the wire loop (Cu²⁺ ions and, when chloride is present, volatile copper halide molecules); as these excited species relax back down they emit visible light concentrated in the blue-green part of the spectrum, giving the flame its characteristic turquoise/blue-green tint; this emission must occur only while the coated loop is inside the flame and only in the region immediately around the loop tip.
(ii)Storyline: [Phase 1] Wire loop shown dry → [Phase 2] Loop dips into liquid (coating appears) → [Phase 3] Loop lifts and moves into flame base → [Phase 4] Green-blue color ignites precisely at tip, confined and steady → [Phase 5] Loop withdraws → color vanishes instantly. Perspective: Fixed frontal view, no cuts or re-framing; full loop and flame base always in frame; lighting ensures high contrast between flame and background; no occlusion of loop tip during color phase.

Manual:
1. A clean metal wire loop is dipped into a copper salt solution, acquiring a visible liquid coating.
2. The coated loop is held steadily in the non-luminous (blue) zone of a Bunsen burner flame for several seconds.
3. A vivid green-blue flame color appears exclusively at the loop tip during heating.
Observation: Immediate emergence of localized green-blue color at the wire tip when heated; color vanishes upon removal.
Principle: Copper ions (Cu²⁺) emit characteristic green-blue photons when thermally excited in flame; color is diagnostic for copper presence.

Prompt Grounding rubric:
level_1: No metal wire loop is ever shown; no liquid coating (from the copper salt solution) ever appears on it; no lit Bunsen burner flame appears; none of these three elements (loop, coated liquid, flame) are ever shown together.
level_2: Only one of the three elements appears (e.g., a flame with no loop nearby, or a bare dry loop with no flame, or a droplet of liquid sitting with no loop or flame in view); the loop is never shown being dipped into liquid or carried toward the flame.
level_3: A metal wire loop, a visible liquid coating on the loop, and a lit Bunsen burner flame are all present; the loop is shown dipped into the liquid and then carried into the flame in that order; however the loop stays in the flame only very briefly, or wobbles/rotates/partly leaves the frame while inside it.
level_4: All conditions for score 3 are met AND the loop keeps a visible liquid coating right up until it enters the flame AND the loop is held steadily inside the flame for several continuous seconds without an early withdrawal, keeping the loop tip fully visible and unoccluded the whole time.
level_5: All conditions for score 4 are met AND the liquid coating is clearly visible on the loop before heating and visibly shrinks/evaporates while the loop sits in the flame AND the loop's position, tilt, and depth of insertion stay essentially unchanged for the entire heating period AND the loop is pulled out of the flame in one clean final motion.

Scientific and Causal Correctness rubric:
level_1: The flame never changes from its normal yellow-orange color; or it turns a color inconsistent with copper, such as red, violet, or white; or a blue-green tint appears before the loop ever enters the flame or lingers after the loop has fully left it.
level_2: The flame does change color, but not to the blue-green associated with copper (e.g. pink, purple, or yellowish-green appears instead); or the color engulfs the whole flame rather than staying near the loop tip; or the color stays visible well after the loop has been withdrawn.
level_3: A blue-green color appears in the flame right around the wire loop tip while the loop is inside the flame; the color starts only after the loop has entered the flame and stops soon after the loop exits; no other metal's flame color (such as sodium's yellow or potassium's lilac) appears at any point.
level_4: All conditions for score 3 are met AND the blue-green color is clearly distinguishable from the plain yellow-orange flame around it and from the background AND the color does not flicker or pulse independently of the loop's position AND no unrelated color artifacts (such as an orange halo or yellow streaking) overlap the blue-green region.
level_5: All conditions for score 4 are met AND the blue-green color appears essentially as soon as the loop tip reaches the flame, with no noticeable delay, stays steady or intensifies while the loop remains in the flame, and fades away in one smooth transition as the loop is withdrawn, without ever splitting into separate colored zones (such as a distinct blue core next to a separate green rim).

Spatiotemporal Consistency rubric:
level_1: The wire loop appears wet, or already in the flame, with no visible dipping or approach motion; the flame's size or shape changes abruptly with no cause; the loop rotates or flips with no connecting motion; liquid on the loop drips or splashes in a way that doesn't match a real dipping motion.
level_2: The loop's motion into the liquid or into the flame skips between positions rather than moving continuously; the flame's brightness or shape changes suddenly partway through the sequence; the liquid coating appears or disappears on the loop without a gradual drying/evaporating look; the shadow cast by the loop or burner shifts inconsistently from one frame to the next.
level_3: The loop stays in a stable position or moves along one continuous path throughout; the flame stays upright with its base in the same spot; the liquid coating stays visible on the loop until it enters the flame; the loop's movement from the liquid into the flame is smooth and unbroken.
level_4: All conditions for score 3 are met AND the lighting on the loop and flame never jumps or flickers between frames AND the loop keeps its shape with no warping or stretching AND the flame's outline stays sharply defined rather than blurring or breaking up AND neither the loop nor the flame strobes frame to frame.
level_5: All conditions for score 4 are met AND the loop keeps the same orientation and apparent size throughout AND the flame keeps a natural, continuous cone shape without flattening or tapering oddly AND the liquid coating shows realistic surface behavior (staying beaded on the wire rather than looking painted-on) before heating begins AND there is no camera jitter or shift that would throw off the loop-to-flame spatial relationship.