Domain: Engineering — Chemical Engineering
Target concept: Ethanol Combustion

Video generation prompt: Take a small amount of ethanol (flammable liquid), and drop it separately onto a smooth metal surface and a cotton cloth. Ignite it with a lighter, and photograph the differences in the combustion process and flame morphology.

Evaluation guide:
(i) Target concept: Combustion duration on a given substrate depends on how that substrate distributes the pooled ethanol before ignition, not on heat alone.
Minimum mechanism: Ethanol must remain a liquid pool prior to ignition; on the non-porous metal surface the ethanol collects as one coherent droplet and the metal's high thermal conductivity spreads the flame's heat evenly across that pool, avoiding localized hot spots that would break up the liquid layer, so the flame is fed steadily until the pooled ethanol is consumed; on the porous cotton cloth, capillary wicking spreads the same small ethanol volume thinly across many fibers, exposing far more surface area with much less liquid depth, so that thin film evaporates and burns off much faster, extinguishing the flame while most fibers remain unburned.
(ii)Storyline: [Frame 0–2] Side-by-side static shot shows clean metal surface and dry cotton cloth. [Frame 3–4] Two distinct ethanol drops placed separately (one on metal, one on cotton), each showing liquid cohesion and surface gloss. [Frame 5–6] Lighter flame contacts each drop individually and visibly; no cross-ignition. [Frame 7–9] Flame appears on both: metal flame expands steadily and holds shape; cotton flame rises quickly then shrinks asymmetrically and vanishes within same timeframe; cloth surface unchanged post-flame. All events occur from fixed frontal viewpoint with consistent lighting and no occlusion.

Manual:
Experimental Procedure
1. Place a smooth metal surface and a cotton cloth side-by-side on a stable, non-flammable base.
2. Using a dropper, place one small, separate drop of ethanol onto the center of the metal surface and another onto the cotton cloth.
3. Ignite each drop individually with the lighter flame, applying it directly to one drop and then the other in turn, with no cross-ignition between the two.
Observation of Experimental Phenomena
- On the metal surface: ethanol burns with a steady, continuous, yellow-orange flame confined to the liquid pool; no damage to metal.
- On the cotton cloth: ethanol ignites briefly with a flickering, narrow flame that self-extinguishes rapidly; cloth remains intact with no charring or hole formation.
Summary of Experimental Principles
Ethanol is highly volatile and flammable. On the smooth, non-porous metal surface, the ethanol stays together as a single liquid pool, and the metal's high thermal conductivity spreads the flame's heat evenly across that pool rather than concentrating it in one spot, so the flame burns steadily until the pooled ethanol is used up. On the porous cotton cloth, capillary action wicks the same amount of ethanol into a thin film spread across many fibers; with much more surface area and much less liquid depth, this thin film burns off far more quickly, so the flame self-extinguishes soon after ignition, before the fibers themselves reach sustained burning — demonstrating that combustion duration here is governed by how the substrate distributes the liquid fuel, not simply by heat absorption versus heat loss.

Prompt Grounding rubric:
level_1: Neither a metal surface nor a cotton cloth is shown; no ethanol liquid appears anywhere in frame; no lighter or ignition flame is used; no flame of any kind appears on either material.
level_2: Only one of the two materials (either the metal surface or the cotton cloth) appears in the shot, with an ethanol drop and a lighter flame applied to it alone; the other material and its ethanol/ignition step are simply missing from the video, so no comparison between the two surfaces is possible.
level_3: The metal surface and the cotton cloth both appear together in the same shot, placed near each other; a separate small ethanol drop is visible on each material; a lighter flame is brought to and touches each of the two drops; a flame becomes visible burning on both the metal surface and the cotton cloth.
level_4: The metal surface and cotton cloth sit next to each other in one continuous shot, each holding its own distinct ethanol drop that never merges into the other's; the lighter is shown touching each drop individually, and it's clear from the framing which flame belongs to which material; once lit, both the metal-surface flame and the cotton-cloth flame stay visible on screen for some time, without either one cutting away or being hidden behind an object right after ignition.
level_5: In one uninterrupted shot from a single fixed camera position, the metal surface and cotton cloth are laid out side by side (not stacked or shown one after another); both ethanol drops remain clearly liquid right up until the lighter touches them; the lighter's contact with each drop is unambiguous, showing exactly which drop it ignites; both the metal-surface flame and the cotton-cloth flame remain visible on screen at the same time for a sustained stretch, with no cut, jump, or added/removed object between the ignition moments and the ongoing flames.

Scientific and Causal Correctness rubric:
level_1: A flame appears on some material that isn't ethanol soaked into metal or cotton (e.g. burning wood or plastic), or the exact same flame behavior shows up on both the metal and the cotton with no difference between them; the liquid used isn't recognizable as a flammable liquid like ethanol (e.g. it looks like water); the flame is a single uniform color on both materials with no contrast in shape or duration.
level_2: Ethanol drops sit on both the metal and the cotton, but a flame only ever appears on one of them; or a flame appears on both but they look and behave essentially the same (same height, same shape, same how-long-it-burns); or the behavior is backwards from what should happen: the cotton's flame outlasts the metal's; or instead of a brief flame, the cotton shows structural fire behavior (glowing embers, spreading char, an expanding burn front through the fabric).
level_3: A flame burns on both the metal surface and the cotton cloth, and the ethanol visibly burns away on both; on the metal, the flame is steady and stays roughly the same size while it lasts, confined to where the pooled ethanol sits; on the cotton, the flame is noticeably shorter-lived: it flickers, shrinks, and goes out on its own well before the metal's flame does, without ever growing into a sustained fire in the fabric.
level_4: The metal flame stays confined to the area of the original ethanol pool and doesn't creep or spread across the metal surface; the cotton flame never turns into sustained fabric combustion: no glowing embers, no visible ash, no advancing burn line through the cloth; comparing the two, the metal's flame reads as broader and holds a steadier shape, while the cotton's flame reads as thinner, more upright, and less stable before it dies out.
level_5: The metal surface shows no visible melting, warping, or scorch marks after the flame goes out; the cotton cloth looks essentially the same as before: no holes, no blackened patch, no missing fibers; the cotton's flame goes out while some ethanol is still left unburned nearby (rather than burning to the very last drop), whereas the metal's flame keeps burning until essentially all of its ethanol pool is consumed; there's no second flare-up, no thick smoke plume, and no lingering glow that wouldn't fit a simple ethanol-only burn.

Spatiotemporal Consistency rubric:
level_1: The ethanol drop, the metal surface, or the cotton cloth appears or disappears between frames with no placement action shown; either substrate suddenly shifts to a different spot or orientation from one moment to the next; a flame shows up in a new location with no visible link to the earlier ignition; the overall lighting flips abruptly (e.g., a bright shot suddenly going dark) partway through; the camera angle or framing cuts or zooms in the middle of the sequence.
level_2: Both materials stay in the shot, but their positions relative to each other drift between moments (say, the cotton edges noticeably closer to or farther from the metal than before); the ethanol drop is never actually shown being placed, only implied; the lighter's contact with a drop happens off-camera or is blocked from view; a flame appears without any visible ignition contact right before it; a flame flickers on and off abruptly in a way that doesn't look like natural flame movement.
level_3: The metal surface and cotton cloth stay in fixed positions relative to each other for the whole clip; the ethanol drop is visibly placed onto each material, with the liquid's arrival on the surface clearly shown; the lighter visibly touches each drop; each flame starts right after its ignition contact, with no unexplained gap; flame movement is continuous throughout, without freezing, skipping ahead, or stuttering.
level_4: The camera position never pans, tilts, or zooms during the clip; the lighting on the scene stays even, without shadows creeping across the frame or the scene abruptly brightening or dimming; the edges of the metal, cotton, and flames stay sharp enough to tell them apart at every moment, without blur that makes it unclear which flame belongs to which material; both flame boundaries stay visually readable throughout, not dissolving into an indistinct blur.
level_5: Neither the metal surface nor the cotton cloth stretches, warps, or shears between frames; the flames don't pulse at some obviously unnatural, machine-like frequency; the two materials don't visibly shift relative to each other from one frame to the next; no hand, tool, or part of the camera rig blocks either flame at any point; there's no lens flare or light bloom bright enough to wash out the flame shapes or the surface details beneath them.