Domain: Natural Science — Earth Science
Target concept: Immerse silicified wood and modern wood in water, and compare their sinking behavior.

Video generation prompt: Two clear water containers are placed side by side. A piece of petrified (silicified) wood is held above the left container, and a piece of cedar wood is held above the right container, both at the same height; the two pieces are released into the water at the same time.

Evaluation guide:
(i) Target concept: Density-driven buoyancy contrast between silicified (petrified) wood and modern cedar wood in water.
Minimum mechanism: Petrified wood must have undergone complete permineralization with silica (density above 2.0 g/cm³), replacing organic matter and eliminating porosity, causing it to sink and remain fully submerged; cedar wood, a common low-density modern wood, must retain intact cellular structure with air-filled lumens (density roughly 0.3–0.4 g/cm³, well under half that of water), causing the majority of its volume to stay above the waterline, consistent with Archimedes’ principle.
(ii)Storyline: Frame 1–2: Static wide shot showing two clear containers side-by-side, each filled with still water; petrified wood held above left container, cedar wood above right container; both at identical height and orientation. Frame 3–4: Simultaneous release, both objects begin downward motion. Frame 5–7: Contact with water surface, visible meniscus deformation and splash/ring formation. Frame 8–10: Petrified wood continues uninterrupted descent to bottom; cedar wood decelerates at surface, stabilizes horizontally or vertically, and remains partially emergent above the waterline. Fixed frontal viewpoint throughout; no cut, zoom, or angle change; all events occur within a single continuous take.

Manual:
Experimental Procedure
1. Place two identical clear water-filled containers side-by-side on a flat surface.
2. Simultaneously release one piece of petrified wood into the left container and one piece of cedar wood into the right container.
Observation of Experimental Phenomena
Petrified wood sinks completely and rests on the container bottom; cedar wood floats, with a clearly visible majority of its volume remaining above the waterline.
Summary of Experimental Principles
Petrified wood is mineral-replaced (silica-dense, density above 2.0 g/cm³) and denser than water, so it sinks; cedar wood retains cellular air spaces and has a low density (roughly 0.3–0.4 g/cm³, well under half that of water), so it floats high with most of its volume above the waterline — producing their contrasting buoyancy.

Prompt Grounding rubric:
level_1: Neither water container appears on screen, or no petrified wood or cedar wood is shown at all, and no release-into-water action occurs for either piece.
level_2: Two containers appear but are not positioned beside one another (e.g., one is stacked above the other, they are far apart, or only one is ever shown at a time); or both wood pieces look visually identical/indistinguishable; or one piece is released into the water while the other is never shown entering it.
level_3: Two clear, water-filled containers rest next to each other; one piece with a hard, stone-like mineralized texture (petrified wood) and one piece with a lighter, fibrous, tan-toned grain (cedar wood) are both shown being released into their own containers without a long delay between the two releases.
level_4: Everything at the 3-point level holds, plus the petrified-wood piece is specifically positioned over the left container and the cedar piece over the right container, and both are held at the same starting height and orientation immediately before release, matching the prompt's left/right assignment.
level_5: Everything at the 4-point level holds, plus both wood pieces remain fully visible (not cropped or hidden behind a container wall) from just before release through their settling behavior in the water, and the frontal view of both containers is maintained without any cut.

Scientific and Causal Correctness rubric:
level_1: The petrified wood floats or the cedar wood sinks (the behavior is reversed from what silica-replacement and low wood density predict), or neither piece ever reaches a settled resting state, or the cedar piece sinks to the container bottom like the petrified wood.
level_2: Only one of the two contrasting behaviors is correct: for example, the petrified wood correctly sinks but the cedar piece also sinks rather than floating, or the cedar piece correctly floats but the petrified wood also floats rather than sinking.
level_3: The petrified-wood piece sinks fully beneath the surface and comes to rest on the container's bottom, while the cedar piece floats with at least half of its volume clearly visible above the waterline, and this contrast holds steadily for at least a second or two after both pieces enter the water.
level_4: Everything at the 3-point level holds, plus the cedar piece stays buoyant without repeatedly rolling, tipping over, or briefly submerging and re-surfacing, and the petrified wood sinks in one continuous downward motion without pausing mid-water or drifting back upward.
level_5: Everything at the 4-point level holds, plus no spurious event misrepresents the causality: no bubble burst pushes the cedar piece further out of the water, no cloud of sediment near the petrified wood implies it is dissolving or losing density, and the initial splash does not obscure which piece enters which container.

Spatiotemporal Consistency rubric:
level_1: Either container or either wood piece appears in a different position, size, or state from one frame to the next with no motion shown connecting the two states: for example, a piece is already resting on its container's floor with no descent ever shown, a container's position on the table changes abruptly between shots, or the lighting shifts abruptly between shots with no cause.
level_2: A wood piece changes direction or orientation without any contact from a hand, a tool, or the water itself (for example, the cedar piece spins on its own well after settling), or the ripple pattern on the water's surface breaks off and restarts without any new disturbance causing it.
level_3: Both containers stay in the same left/right positions and sizes across the whole clip; each wood piece travels a single, unbroken downward path from where it was held into its own container's water, and neither piece is duplicated, swapped between containers, or shown already resting before its entry motion is depicted.
level_4: Everything at the 3-point level holds, plus the descent of each piece toward and into the water is smooth and gravity-like, with no sudden jumps, freezes, or backward motion, and the surface ripples produced by each splash spread outward and settle rather than looping or repeating.
level_5: Everything at the 4-point level holds, plus the two release-and-entry events occur within the same short window with no reordering: the petrified wood is never shown resting on the bottom before its own splash occurs, and the cedar piece is never shown floating before it has actually touched the water.