Domain: Natural Science — Chemistry
Target concept: Carbon dioxide is bubbled into lime water, causing it to become turbid.

Video generation prompt: Carbon dioxide gas is passed through a tube into a glass beaker containing clear lime water.

Evaluation guide:
(i) Target concept: Formation of insoluble calcium carbonate precipitate via CO₂ + Ca(OH)₂ reaction.
Minimum mechanism: CO₂ must dissolve and react in aqueous phase; Ca(OH)₂ must be present as dilute saturated solution; product CaCO₃ must remain suspended as colloidal particles, not settle immediately.
(ii)Storyline: Frame 0–1: Clear lime water visible in stationary beaker, tube above liquid. Frame 2–3: Tube tip enters liquid; first bubbles emerge at interface. Frame 4–6: Bubbles rise steadily; turbidity initiates at bubble path and expands upward/downward symmetrically. Frame 7–9: Full turbidity achieved — liquid uniformly milky white, obscuring beaker base but retaining translucency; bubbles continue rising visibly through turbid medium. Perspective: Fixed frontal camera angle, no occlusion, full beaker and tube insertion zone always in view.

Manual:
1. Place a clean glass beaker on a stable surface and fill it halfway with clear, colorless lime water.
2. Insert one end of a rigid delivery tube into the lime water so the tip is fully submerged.
3. Gently bubble carbon dioxide gas through the tube into the lime water.
Observation: The initially clear lime water becomes uniformly turbid (milky white) during and after bubbling.
Principle: Carbon dioxide reacts with calcium hydroxide in lime water to form insoluble calcium carbonate, causing turbidity.

Prompt Grounding rubric:
level_1: No lime water container visible; no tube or gas delivery apparatus present; no beaker shown; no carbon dioxide introduction action depicted.
level_2: A beaker is present and contains a liquid, but the liquid is not clearly lime water (e.g., wrong color, no label, or indistinguishable from water); tube is present but not inserted into the liquid; no visible connection between gas source and tube.
level_3: A transparent glass beaker containing a clear, colorless liquid is present; a rigid tube is visibly inserted into the liquid; the tube extends from outside the beaker into the liquid volume; no other apparatus contradicts the posted_prompt.
level_4: All elements from score 3 are present AND the tube enters the beaker from above (not sideways or submerged externally); the beaker is stationary on a flat surface; the tube maintains fixed insertion depth throughout the video; no extraneous objects (e.g., hands, labels, unrelated equipment) occlude or replace core prompt elements.
level_5: All elements from score 4 are present AND the tube is visibly connected to an implied or partially shown gas source (e.g., tubing junction or labeled CO₂ cylinder visible in frame periphery); the beaker is centered in frame with unobstructed frontal view; no visual ambiguity about tube–liquid contact at all frames.

Scientific and Causal Correctness rubric:
level_1: No turbidity appears at any time; liquid remains completely clear throughout; no state change observed; no causal link between tube presence and liquid appearance.
level_2: Turbidity appears but is inconsistent (e.g., appears before tube insertion, disappears during insertion, or occurs only at edges without spreading); turbidity color is incorrect (e.g., yellow, blue, or opaque white instead of milky white); liquid was initially cloudy or colored, violating baseline clarity.
level_3: Liquid starts clear and colorless; turbidity appears only after tube insertion into liquid; turbidity is milky white and uniformly distributed within the liquid volume (not localized to bubble path only); turbidity persists continuously after onset.
level_4: All elements from score 3 are present AND turbidity develops progressively from the point of bubble emergence upward through the liquid column; no reversal (e.g., clearing) occurs; no discoloration (e.g., yellowing, browning) or phase separation (e.g., precipitate sinking visibly as distinct layer) contradicts standard CaCO₃ suspension behavior.
level_5: All elements from score 4 are present AND turbidity fully obscures visibility of the beaker bottom and sidewall markings (if any) while retaining translucent milky appearance (not opaque solid block); bubbles are visibly rising through the turbid medium without breaking surface violently; no unnatural dissolution or coagulation artifacts.

Spatiotemporal Consistency rubric:
level_1: Beaker jumps position or changes size abruptly; tube appears/disappears mid-video; liquid surface level changes discontinuously without cause; lighting shifts drastically between frames (e.g., full shadow to full highlight).
level_2: Minor spatial inconsistency: tube tip moves in/out of liquid without corresponding motion origin; beaker rotates or tilts without physical support; turbidity appears in one frame and fully covers liquid in next without intermediate frames showing spread.
level_3: All objects maintain fixed relative positions; tube remains continuously inserted; liquid surface stays level; turbidity spreads gradually across frames (no frame-skipping appearance); lighting and shadows remain consistent in direction and intensity.
level_4: All elements from score 3 are present AND no object flickers, warps, or pixelates; no inter-frame jitter or misalignment of beaker/tube edges; no abrupt brightness/contrast shifts; no temporal discontinuity (e.g., missing frames manifesting as jump-cut motion).
level_5: All elements from score 4 are present AND motion is physically plausible: bubbles rise vertically at steady pace without acceleration/deceleration artifacts; turbidity diffusion follows smooth, continuous gradient progression across adjacent frames; no aliasing, blurring, or strobing that breaks perceptual continuity.