Domain: Natural Science — Physics
Target concept: Comparison of a metal spoon and a wooden spoon in hot water, demonstrating different rates of heat transfer

Video generation prompt: Place a metal spoon and a wooden spoon side by side in the same transparent container filled with hot water, and place a small equal amount of butter on the handles of each spoon above the water surface.

Evaluation guide:
(i) Target concept: Differential thermal conductivity between metal and wood drives asymmetric phase change in butter placed on spoon handles above hot water.
Minimum mechanism: Heat must propagate conductively through solid spoon material (not convectively via water or radiatively); butter phase change requires sufficient temperature rise at handle location; no external heat sources or forced convection may interfere.
(ii)Storyline: [Frame 0–2] Stable wide shot: transparent container with hot water (steam/meniscus visible); two spoons inserted side-by-side, handles aligned above water. [Frame 3–5] Butter placed simultaneously on each handle: identical size, position, orientation. [Frame 6–8] Metal spoon butter begins losing shape (edges soften, surface glistens, then pools); wooden spoon butter retains crisp geometry, no gloss or deformation. [Frame 9–10] Contrast fully established: one melted, one solid; no reversal, no ambiguity. Perspective: fixed frontal view, full spoons and waterline in frame, no occlusion, consistent lighting.

Manual:
Experimental Procedure
1. Fill a transparent container with hot water (visible steam or surface shimmer).
2. Place a metal spoon and a wooden spoon side-by-side into the water, fully submerging their bowls/shafts, with handles extending identically above water.
3. Place one small, equal portion of butter on the handle of each spoon, above water surface.
Observation of Experimental Phenomena
Butter on the metal spoon melts (loses solid shape, pools, or drips), while butter on the wooden spoon remains solid (retains original shape and sharp edges) throughout the observation period.
Summary of Experimental Principles
Metals conduct heat faster than wood; thermal energy transfers rapidly from hot water through the metal spoon to its handle, melting the butter. Wood is a poor conductor, so little heat reaches the wooden handle, leaving the butter unmelted.

Prompt Grounding rubric:
level_1: No transparent container is shown, or no spoon appears, or only one type of spoon is present, or butter is missing from both handles, or the spoons are not standing in water, or butter sits below the waterline instead of above it.
level_2: A transparent container and at least one spoon are visible, and butter appears on at least one handle, but the spoons are not placed side by side, or they are not both standing in the same container of water, or the butter sits on the bowl or shaft of a spoon rather than the handle, or it is not clear from looks alone which spoon is metal and which is wood (e.g., both appear shiny, or both appear brown and grainy).
level_3: A transparent container holds visibly hot water (steam rising or the surface shimmering); one spoon has a shiny, silver-gray, reflective look and the other has a matte, tan/brown, grainy look; both stand side by side in the same container with their handles rising above the waterline; a small portion of butter sits on each handle above the water.
level_4: Everything in level 3 holds, and additionally: the spoons stay put for the whole video without being lifted, turned, or repositioned; the two butter portions look about the same size and shape when first placed; nothing (a hand, a thermometer, a label) blocks the view of either spoon or its butter; the camera holds a steady front-on view showing both full handles and the waterline.
level_5: Everything in level 4 holds, and additionally: the two spoons sit parallel to each other, the same distance from the container's walls and at the same depth in the water, with their handle tips ending at the same height above the surface; the two butter portions start in matching positions on their respective handles (e.g., both centered, both near the tip) and sit flat rather than smeared or tilted.

Scientific and Causal Correctness rubric:
level_1: Neither butter portion changes shape at all, or both portions melt (or both stay solid) by the same amount, or a portion disappears outright rather than softening or pooling, or the wooden spoon's butter melts faster or more than the metal spoon's butter.
level_2: One butter portion melts while the other stays visibly solid, but the melting happens on the wooden spoon's handle rather than the metal spoon's handle, or it cannot be told from the video which spoon is metal and which is wood at the moment melting starts, so the melting pattern does not confirm that metal conducts heat faster than wood.
level_3: The butter on the metal spoon's handle visibly loses its shape (softens, pools, or drips) while the butter on the wooden spoon's handle keeps its original block shape with sharp edges; neither portion changes color or chars; melting starts only after the spoons are already sitting in the hot water, not before.
level_4: Everything in level 3 holds, and additionally: the melted butter on the metal handle stays as a cohesive pool or drip rather than splattering or misting away; the wooden spoon's butter shows no softening, sagging, or rounding at its edges; the metal spoon's butter visibly begins changing noticeably earlier than any change appears on the wooden spoon's butter.
level_5: Everything in level 4 holds, and additionally: melting is confined to the metal handle above the waterline and never starts at or below the waterline (which would suggest direct water contact rather than conduction through the metal); the wooden spoon's butter shows no gloss, sheen, or blurred edges suggesting any heat reached it; the sequence reads cleanly as spoons entering hot water, then only the metal handle's butter melting while the wooden handle's butter stays solid throughout.

Spatiotemporal Consistency rubric:
level_1: The container or a spoon vanishes and reappears in a completely different spot, or a spoon flips or slides across most of the frame between one frame and the next, or the water's surface jumps or flickers violently, or a butter portion jumps from its handle into midair or into the container, or the lighting suddenly flashes, strobes, or cuts to darkness.
level_2: A spoon drifts sideways by a small amount (noticeably less than a quarter of its width) between frames, or one handle's tilt angle shifts slightly relative to the other without a matching cause, or a butter portion wobbles or shears in place without any corresponding motion of its spoon, or the water surface ripples a bit more than expected for two motionless spoons.
level_3: Both spoons stay side by side and parallel for the entire video; the water level in the container stays constant; each butter portion stays fixed on its handle without sliding, falling, or floating away; neither spoon nor its butter flickers, breaks apart, or shows ghosting; the apparent light source stays in the same place and the scene's overall brightness does not swing up or down.
level_4: Everything in level 3 holds, and additionally: the motion across frames looks smooth with no stutter, frozen frames, or sudden jump-cuts; the metal spoon's shiny surface does not flicker between reflective and dull-looking; the container's edges and background stay in consistent perspective if the camera shifts slightly.
level_5: Everything in level 4 holds, and additionally: neither spoon's outline nor the butter's edges shimmer, flicker, or waver at any point; the two spoons keep the same size and position relative to each other from first frame to last with no visible sliding or resizing; nothing about either spoon's rigidity looks unnatural (steady stillness of the solid handles is the correct look, not a flaw).