Domain: Natural Science — Physics
Target concept: Milk protein film formed on a heated stainless steel surface

Video generation prompt: A stainless steel plate is heated from below, while milk continuously flows over its surface under continuous heating.

Evaluation guide:
(i) Target concept: Thermally induced interfacial protein denaturation and deposition on a heated metal surface.
Minimum mechanism: Milk must be in direct, sustained liquid contact with a heated stainless steel surface; thermal energy must exceed protein denaturation threshold (~65–75°C surface temp); surface must be hydrophilic and non-stick enough to allow flow but adhesive enough for film retention.
(ii)Storyline: [Frame 0–2] Heat source activates beneath stationary stainless steel plate → [Frame 3–4] Liquid milk enters top edge, makes first contact → [Frame 5–7] Wetting front advances; film initiates at initial contact zone and extends synchronously with flow → [Frame 8–10] Film fully covers wetted region; milk exits bottom edge still liquid; film remains intact, matte, and confined. Perspective: Fixed frontal/slightly oblique view showing full plate width, top-to-bottom flow axis, and unobstructed view of surface-film interface; no occlusion of contact zone.

Manual:
Experimental Procedure
1. Place a clean, horizontal stainless steel plate on a stable heat source.
2. Heat the plate from below until thermally active (no visible glow required).
3. Pour fresh liquid milk steadily onto the top edge of the hot plate so it flows continuously downward across the surface.
Observation of Experimental Phenomena
A thin, opaque, off-white to pale yellow film forms selectively on the stainless steel surface *only where milk contacts it*, progressing downstream as flow continues; milk upstream remains fully liquid and translucent; no film forms in air or on cold surfaces.
Summary of Experimental Principles
Milk proteins (especially casein and whey) denature and coagulate upon contact with a sufficiently hot stainless steel surface, forming an insoluble, adherent protein film — a thermally driven interfacial deposition process.

Prompt Grounding rubric:
level_1: No stainless steel plate is shown, or no milk is shown flowing, or no heat source beneath the plate is indicated, or the milk simply sits still rather than moving across the surface.
level_2: The plate, the flowing milk, and a heat source are not all present together: for example the plate appears but milk never touches it, or milk flows but nothing beneath the plate suggests heating.
level_3: The stainless steel plate, a heat source positioned beneath it, and a stream of milk are all present at the same time; the plate sits roughly horizontal with the heat source underneath it; milk moves across the plate's top surface in a generally top-to-bottom direction.
level_4: The plate stays in place without sliding or rotating out of position; the milk flows in one steady direction without splashing or pooling at the plate's edges; the heat source itself (flame, coil, or burner) is not shown poking up above or beside the plate; only its heating effect on the plate surface is implied.
level_5: Milk enters at the plate's upper edge, wets the surface almost immediately on contact, travels the full visible length of the plate without lifting off or splashing, and exits at the lower edge in one continuous, unbroken stream from start to finish.

Scientific and Causal Correctness rubric:
level_1: Nothing resembling protein denaturation appears: the milk stays liquid and visually unchanged in color and texture everywhere on the plate, with no film and no discoloration at any point.
level_2: Some change happens but is scientifically wrong for this setup: for example the milk instantly boils into foam, blackens or chars right away, or a film appears on the milk stream itself or in mid-air before the milk ever touches the plate.
level_3: A thin, matte, off-white to pale-yellow film appears on the plate specifically where milk has already flowed over it, while milk further upstream (in contact only briefly) still looks liquid; no film appears anywhere the milk hasn't touched.
level_4: The film begins to appear promptly at the wetting front as milk first reaches each section of the plate, keeping pace with the advancing flow rather than forming ahead of contact or lagging noticeably behind it, and it spreads gradually downstream as more milk flows, staying flat and matte rather than bubbling, cracking, or peeling.
level_5: The film's outer edge visibly tracks just behind the leading edge of the milk's wetting front, so the coated region keeps growing to match the area the milk has covered; once deposited, the film stays on the plate rather than fading or lifting away if the flow later thins or slows, consistent with a coagulated protein deposit that does not redissolve.

Spatiotemporal Consistency rubric:
level_1: The plate's position or shape changes abruptly between frames (it shifts, bends, or appears to split); the milk stream jumps across a gap instead of flowing continuously; the light on the scene changes abruptly, such as a sudden jump from bright to dark, with no visible cause.
level_2: The direction or angle of the light on the plate changes noticeably more than once across the sequence; the plate or the milk stream flickers out of view for two or more frames and then reappears; the milk's flow direction reverses or freezes momentarily with no visible cause.
level_3: The plate never shifts, bends, or rotates out of its fixed orientation; the milk keeps flowing without gaps or sudden jumps; the direction and brightness of the light on the plate stay the same from the first frame to the last, with no jarring jumps in camera angle.
level_4: The camera viewpoint itself never pans, tilts, or zooms; the plate and the heat source stay in the same position relative to each other throughout; the milk's flow speed changes smoothly, if at all, rather than stuttering or jumping between frames.
level_5: The milk's surface shows small, physically plausible ripples as it flows rather than sitting perfectly still or jittering; the film's coated region visibly keeps pace with the wetting front with no noticeable lag or jump ahead of it; at no point does the milk appear to sit both above the plate and already coating that same section, which would contradict the direction of flow.