Domain: Natural Science — Physics
Target concept: Saltwater Floats an Egg

Video generation prompt: Place two identical transparent glasses side by side on a table, with the glass on the left containing saturated saltwater and the glass on the right containing an equal volume of pure water. A single egg is placed in each glass simultaneously.

Evaluation guide:
(i) Target concept: Differential buoyancy due to liquid density difference enabling flotation in saltwater but not in pure water.
Minimum mechanism: Egg must be denser than pure water but less dense than saturated saltwater; liquids must be static, homogeneous, and unmixed; egg must be intact, uncracked, and free of air pockets affecting average density; gravitational field uniform and stable.
(ii)Storyline: Frame 1–2: Static wide shot showing two empty glasses side-by-side on table. Frame 3–4: Liquids poured (not scored, but must conclude before egg placement). Frame 5–6: Two eggs enter frame simultaneously from top. Frame 7–8: Eggs descend along continuous vertical paths into respective glasses. Frame 9–10: Eggs reach final states (left egg floating with clear air–liquid interface beneath, right egg fully submerged and contacting bottom), both motionless, fully visible, side-by-side, under consistent lighting and fixed viewpoint.

Manual:
Experimental Procedure
1. Place two identical transparent glasses side-by-side on a flat table.
2. Fill left glass with saturated saltwater; fill right glass with equal volume of pure water.
3. Simultaneously place one raw hen egg into each glass.
Observation of Experimental Phenomena
The egg in the left glass floats (partially or fully above liquid surface); the egg in the right glass sinks (fully below liquid surface, resting on bottom).
Summary of Experimental Principles
Buoyant force equals weight of displaced fluid; saturated saltwater has higher density than pure water, so it exerts greater upward buoyant force on the egg — sufficient to exceed the egg’s weight, causing flotation. Pure water’s lower density yields insufficient buoyant force, so the egg sinks.

Prompt Grounding rubric:
level_1: No two transparent glasses are shown, or only one glass appears, or neither glass has an egg in it; the two glasses are not placed side by side on the table; the containers are opaque, tinted, or non-glass (e.g., ceramic bowls or metal cups) rather than clear glass; the eggs are absent, clearly mismatched in size or shell color, or more than one egg sits in a single glass.
level_2: Two clear glasses stand side by side, but at least one egg is missing, is floating outside a glass, is held by a hand, or rests on the table rather than fully inside its glass; or the saturated saltwater and plain water called for by the prompt are not both shown poured into their respective glasses before the eggs are added.
level_3: Two similarly sized clear glasses sit side by side on the table, each filled to a comparable height with liquid; one intact egg rests fully inside the left glass and one intact egg fully inside the right glass; both eggs match each other in size, shape, and shell color; the two eggs are placed into their glasses at essentially the same time, matching the prompt's simultaneous placement.
level_4: Everything required for score 3 is present, AND the liquid fill lines in the two glasses visually match each other, consistent with the prompt's 'equal volume'; both liquids appear clear and visually similar to one another (no fabricated cloudiness, tint, or suspended particles used to make the saltwater look different, since a fully dissolved saturated solution is optically clear); each egg is fully covered by liquid immediately after entering its glass; the left glass consistently corresponds to the saltwater and the right glass to the plain water for the whole video, with no swap in position.
level_5: Everything required for score 4 is present, AND the camera holds one fixed frontal framing with no cut, pan, or zoom from before the eggs enter until both reach their final resting state; the two eggs enter their glasses within the same continuous shot rather than in separate cuts; no hand, dropper, or utensil remains visible in the frame once the eggs are released; both liquid surfaces settle to still and level after the entry ripples fade, and the two glasses keep the same left/right positions and apparent size relative to each other throughout.

Scientific and Causal Correctness rubric:
level_1: The two eggs behave identically: both sink fully to the bottom in both glasses, or both float in both glasses, or both hang suspended mid-liquid in both glasses: saturated saltwater and pure water produce no visible difference in how the eggs settle.
level_2: A difference seems to appear (e.g., the left egg looks like it is rising while the right looks like it is sinking), but it cannot be confirmed by eye: one egg is out of frame, occluded, blurred, or reflects too much glare, or an egg rests at an ambiguous mid-depth that is neither clearly floating nor clearly resting on the bottom.
level_3: The egg in the left (saturated saltwater) glass ends up floating with at least about half its volume above the liquid surface; the egg in the right (pure water) glass ends up fully submerged and resting on the glass bottom; both final states are stable, unambiguous, and clearly visible without occlusion: the correct differential-buoyancy outcome.
level_4: Everything needed for score 3 holds, AND the floating egg settles into a stable position without spinning, tipping onto its side against the glass wall, or slipping back underwater; the sunk egg lies flat on the glass bottom without rocking or sliding sideways; neither liquid surface keeps rippling or splashing once the eggs have come to rest.
level_5: Everything needed for score 4 holds, AND the floating egg shows a clear, fixed boundary between its submerged lower portion and the air above the saltwater once it stops moving; the sunken egg's underside stays in full, unbroken contact with the glass bottom for the rest of the video; neither egg shows any further rotation, sliding, or bounce after it first settles, and the float-versus-sink contrast between the two glasses remains visible and unchanged through the final frame.

Spatiotemporal Consistency rubric:
level_1: A glass or an egg jumps to a different position or size between one frame and the next with no visible motion connecting the two; an egg or a glass vanishes from view and later reappears; the liquid level inside a glass changes suddenly rather than through a continuous pour or entry ripple; the room lighting switches abruptly from bright to dark (or back) within a single frame; a glass appears to crack, bend, or melt with no physical cause.
level_2: An egg appears already inside its glass with no visible drop connecting its start above the glass to its landing in the liquid; a glass's rim or wall visibly warps or wobbles between frames instead of staying rigid; the shadow cast by a glass or egg jumps to the opposite side of the object with no change in the light in the scene; a background object flickers, duplicates, or briefly changes shape.
level_3: Both glasses stay in the same left/right positions throughout; each egg descends along a continuous, visible path from above its glass down into the liquid, with no skipped frames; the liquid surface in each glass ripples and settles smoothly after the egg enters, without a sudden jump in level; no glass or egg passes through another surface, clips through the table, or briefly turns transparent.
level_4: Everything described for score 3 holds, AND each egg's descent visibly slows as it nears its final resting depth rather than stopping instantly; the direction and brightness of the shadows on the table and glass walls stay the same from the first frame to the last; the liquid surfaces and egg edges do not flicker or shimmer from one frame to the next.
level_5: Everything described for score 4 holds, AND both glasses keep the same outline and position frame to frame with no visible wobble, resizing, or drift; each egg's transition from entry to fully settled float or sink plays out as one continuous motion with no visibly missing stage; the curve where the liquid meets the glass wall changes smoothly as the egg settles, with no abrupt jump in its shape; the glass walls stay clear and free of flickering double edges or ghost outlines around the eggs.