Domain: Natural Science — Physics
Target concept: Evaporation Rate Comparison: Water and Medical Alcohol Droplets on Glass

Video generation prompt: Place two equally sized droplets simultaneously on a clean, horizontal glass plate under the same indoor conditions: the left one is water, and the right one is medical alcohol.

Evaluation guide:
(i) Target concept: Differential evaporation kinetics driven by molecular volatility.
Minimum mechanism: Both liquids must remain in stable liquid phase on inert, non-porous, thermally homogeneous substrate; ambient conditions must permit passive evaporation (no forced airflow, no heating); intermolecular forces in water (H-bonding) must dominate over those in ethanol-water mixture (weaker dipole-dipole), yielding lower vapor pressure for water.
(ii)Storyline: Frame 0–1: Two identically sized, spherical-cap-shaped, transparent droplets appear side-by-side on flat glass: left is water (neutral refractive index), right is medical alcohol (slightly lower refractive index, indistinguishable visually at start). Frame 2–8: Right droplet progressively reduces in height and diameter with smooth meniscus collapse; left droplet retains near-constant dimensions and convex profile. Frame 9: Right droplet fully disappears; left droplet remains fully intact, circular, and optically clear. Throughout: Fixed frontal viewpoint, stable lighting, no external interference; all changes arise solely from autonomous volume loss via evaporation.

Manual:
Experimental Procedure
1. Place a clean, horizontal glass plate in static indoor lighting.
2. Simultaneously place one droplet of water on the left half and one droplet of medical alcohol on the right half — both same initial size and shape.
3. Observe continuously for 10 seconds without intervention.
Observation of Experimental Phenomena
The right droplet (medical alcohol) shrinks continuously and vanishes completely before the left droplet (water) shows significant size reduction.
Summary of Experimental Principles
Medical alcohol has higher vapor pressure and lower boiling point than water, resulting in faster evaporation rate under identical temperature and humidity conditions.

Prompt Grounding rubric:
level_1: The glass plate is not shown, or no droplets are present, or only one droplet is shown, or the two droplets are not placed on the plate at the same time (one clearly appears before the other), or the droplets are positioned with alcohol on the left and water on the right, the reverse of the described setup.
level_2: The glass plate is shown horizontally with two droplets present, but the droplets are not placed side by side (e.g., one sits on top of or overlapping the other, or both are crowded onto one side of the plate), or the two droplets appear at clearly different moments rather than together, or it is unclear which side of the plate each droplet occupies.
level_3: The glass plate is shown horizontal with two separate droplets placed side by side at the same time, one on the left and one on the right, matching the water-left / medical-alcohol-right setup; because water and medical alcohol droplets genuinely look alike the moment they are placed, this left/right position (not an added color tint, glow, or text label) is what identifies which droplet is which.
level_4: Everything at level 3 holds, and in addition the two droplets start out visually equal in size (similar apparent diameter and dome height), and no hand, tool, on-screen text, or graphic marker ever covers or is overlaid on either droplet.
level_5: Everything at level 4 holds, and in addition both droplets stay inside one continuous, unmoving camera frame from the moment they are placed until the end of the clip, viewed straight-on and level with the glass surface, with no pan, zoom, tilt, or cut away from the pair at any point.

Scientific and Causal Correctness rubric:
level_1: Neither droplet shows any visible reduction in size over the course of the video, so no evaporation difference is depicted at all; or the water droplet visibly shrinks faster than the medical alcohol droplet, the reverse of the true effect; or a droplet changes through some means other than shrinking evenly (e.g., splitting apart, developing bubbles, turning cloudy or a different color) that is not consistent with simple evaporation.
level_2: Both droplets shrink at essentially the same rate and vanish at nearly the same time, so no meaningful evaporation-speed difference between water and alcohol is shown; or a size difference between the two droplets appears only briefly and then reverses or evens out again (e.g., the alcohol droplet looks smaller for a moment but the two look equal again soon after); or a droplet's disappearance looks abrupt or glitchy, blinking out rather than visibly shrinking down.
level_3: The right droplet (medical alcohol) shows a progressive, continuous reduction in diameter and height over time; the left droplet (water) shrinks visibly more slowly or negligibly by comparison; both droplets stay liquid, clear, and roughly circular from above, without splattering, splitting, or spreading out.
level_4: Everything at level 3 holds, and in addition the alcohol droplet shrinks all the way down and disappears before the water droplet shows any noticeable size reduction; neither droplet reappears, rebounds, or leaves behind a visible residue or film.
level_5: Everything at level 4 holds, and in addition the water droplet is still clearly visible, intact, and essentially the same size and clarity it started with right after the alcohol droplet fully disappears; the order in which the two droplets change stays unambiguous throughout, with no in-between state (such as a ring mark, film, or cloudiness) suggesting anything other than straightforward evaporation.

Spatiotemporal Consistency rubric:
level_1: One of the droplets disappears from the plate and then reappears in a later frame, or the glass plate itself jumps to a different position or angle between frames, or the whole scene suddenly switches between a dim and a bright look with no transition, or a droplet's outer edge breaks apart or dissolves without any visible shrinking motion, or the video visibly skips or freezes in a way that breaks the sense of continuous time passing.
level_2: The glass plate stays in place but the image shows visible warping or a shifting perspective inconsistent with a fixed straight-on camera; a droplet's outline moves in small jumps rather than a smooth, continuous shrink, as if skipping over several in-between sizes at once; the shadow cast by a droplet moves to a position that no longer matches the droplet's own location; or objects behind the plate appear to stretch or shear between frames.
level_3: The glass plate stays fixed in position and orientation for the whole clip; each droplet's shrinking looks smooth and gradual, with no sideways drift, no pulsing back-and-forth in size, and no sudden jump straight to a much smaller size; the overall brightness of the scene does not suddenly jump up or down; neither droplet's outline tears, splits into pieces, or breaks apart as it shrinks.
level_4: Everything at level 3 holds, and in addition the scene's overall brightness stays even from frame to frame rather than flickering; neither droplet's outline becomes blurred or doubled in a way that hides its true boundary; the camera view does not drift sideways or closer/farther in a way suggesting unintended movement; the spot where each droplet touches the glass stays visible and is never hidden behind glare or reflection.
level_5: Everything at level 4 holds, and in addition the alcohol droplet's shrinking proceeds in one steady direction from start to finish with no moment where it appears to grow back or pause for an extended stretch; the video shows no repeated or duplicated-looking segment; each frame's droplet size looks like a believable step between the size in the frame before it and the frame after it, with no sudden unnatural change in a droplet's texture or transparency partway through.