Domain: Natural Science — Environmental Science
Target concept: Exhaled gas is bubbled through an indicator solution, showing an increase in dissolved carbon dioxide.

Video generation prompt: Two identical transparent beakers, each containing an indicator sensitive to carbon dioxide, were placed on the laboratory bench; exhaled gas was blown into the left beaker through a pipette, while the right beaker remained undisturbed.

Evaluation guide:
(i) Target concept: Visual demonstration of CO₂-driven pH change via indicator color shift, requiring differential treatment of two identical systems.
Minimum mechanism: Exhaled gas must contain sufficient CO₂ to acidify solution; indicator must be chemically responsive to pH drop; color change must be irreversible within observation window; no external contamination or temperature drift affecting reaction.
(ii)Storyline: Frame 1–2: Static wide shot showing two identical beakers side-by-side, both filled with identically colored solution. Frame 3–4: Hand enters frame holding pipette, positions it over left beaker opening. Frame 5–7: Pipette tip contacts or enters left beaker liquid; simultaneous onset of progressive color change *only* in left beaker. Frame 8–10: Left beaker stabilizes at new color; right beaker retains original color and stillness; fixed viewpoint maintains spatial integrity throughout. Visibility constraints: Entire beaker bodies, liquid surfaces, pipette tip, and hand (at least partial) must remain fully in-frame and unoccluded; no zoom, pan, or cut permitted.

Manual:
Experimental Procedure
1. Place two identical transparent beakers side-by-side on bench.
2. Fill both with same CO₂-sensitive indicator solution (e.g., bromothymol blue, initially blue).
3. Blow exhaled gas through pipette into left beaker only.
4. Observe color change in left beaker; right beaker remains unchanged.
Observation of Experimental Phenomena
Left beaker solution changes from blue to green/yellow; right beaker solution remains blue throughout.
Summary of Experimental Principles
Exhaled gas contains elevated CO₂; dissolved CO₂ forms carbonic acid, lowering pH; indicator solution changes color in response to pH decrease.

Prompt Grounding rubric:
level_1: No pair of clear beakers appears; no colored indicator liquid is visible in either container; no pipette is shown; there is no cue that one container is being blown into while the other sits untouched.
level_2: Two containers appear but are not matched (different glass shape, size, or material — e.g., a flask paired with a jar); indicator liquid is present in only one of them; a pipette appears but does not point toward or touch either container; or the video gives no clear sense of which container is on the left versus the right.
level_3: Two matching clear beakers of the same shape and size sit next to each other on the bench, both holding the same colored indicator liquid; a pipette is positioned at or inside the left beaker; the right beaker has no tool or hand near it; the left/right layout stays fixed for the whole clip.
level_4: All score 3 conditions hold AND the pipette tip visibly touches the left beaker's rim or dips into its liquid surface; the right beaker shows no hand, pipette, or tool anywhere near it; both beakers sit at the same height and tilt relative to the bench, matching each other throughout.
level_5: All score 4 conditions hold AND a human hand is at least partly visible holding the pipette over the left beaker for the entire clip; the right beaker's liquid surface stays completely flat with no ripple, and no hand or shadow ever crosses over it; the two beakers keep their original spacing on the bench without either one being moved, nudged, or refocused on by the camera.

Scientific and Causal Correctness rubric:
level_1: Neither beaker's liquid changes color at all, or both beakers end up the same color they started as; there is no visible difference between the left and right beaker's liquid at any point; the pipette's presence at the left beaker has no apparent connection to any color change.
level_2: A color change happens in the wrong beaker (right only) or in both beakers at once; the color shifts to a hue not expected for a CO2-sensitive indicator absorbing exhaled breath (e.g., it turns purple, or gets darker instead of shifting toward green/yellow); or the color change starts well before the pipette ever touches the left beaker's liquid.
level_3: Only the left beaker's liquid changes color, moving from its starting hue (e.g., blue) toward a green or yellow tone consistent with the solution becoming more acidic; the right beaker's liquid keeps its original color the whole time; the left beaker's color change begins only after the pipette tip touches or enters its liquid.
level_4: All score 3 conditions hold AND the left beaker's color shift moves in one direction only, without flickering back toward the original hue or stalling partway through; the right beaker's liquid shows no hue shift, no brightening or darkening, and no change in clarity for the entire clip.
level_5: All score 4 conditions hold AND the left beaker ends at a color clearly distinct from where it started (e.g., blue to yellow-green) with a visible contrast between beginning and end; the right beaker's liquid matches the left beaker's starting color at every point in the video; the left beaker's color change begins right as the pipette makes contact and continues smoothly without stalling.

Spatiotemporal Consistency rubric:
level_1: One or both beakers change position or size abruptly between frames with no camera pan to explain it; the pipette or the hand holding it disappears from one frame and reappears in another; the room lighting switches from bright to dim between adjacent frames with no fade; a beaker's rim appears to crack or distort for no physical reason; or the liquid surface jumps or warps discontinuously from one frame to the next instead of moving smoothly.
level_2: A beaker rotates or tips noticeably from one frame to the next with no visible cause; the pipette's motion is jerky or snaps between positions rather than moving smoothly; the left beaker's liquid ripples in a way that doesn't match where the pipette entered (e.g., ripples starting at the beaker wall instead of the pipette tip); or the hand/pipette's shadow disappears for a stretch of frames and then reappears.
level_3: Both beakers stay in the same spot and orientation across the whole clip; the pipette's motion is smooth and stays aimed at the left beaker only; any ripple on a liquid surface appears only while the pipette is in contact with the left beaker's liquid and stays small; the bench and beakers keep the same lighting look from the first frame to the last.
level_4: All score 3 conditions hold AND neither beaker changes apparent size or shape across frames; the left beaker's glass and liquid surface don't flicker in transparency between frames; the hand, pipette, and left beaker always line up in a way that looks physically connected (no floating pipette, no hand at an impossible angle).
level_5: All score 4 conditions hold AND any ripple on the left beaker's liquid clearly starts at the point where the pipette enters and spreads outward while shrinking, rather than appearing at random; no frame shows blur heavy enough to hide the beakers' edges, the pipette tip, or the liquid's color; the bench surface behind the beakers holds still with no warping or shifting between frames.