Domain: Healthcare — Nutrition & Dietetics
Target concept: Milk protein denaturation caused by acid and formation of curd

Video generation prompt: In a transparent glass bowl containing warm milk, slowly add vinegar while gently stirring with a spoon.

Evaluation guide:
(i) Target concept: Acid-induced protein denaturation and aggregation into visible curds in warm dairy matrix.
Minimum mechanism: Vinegar (acetic acid) must contact warm milk; acid protons disrupt casein micelle stability; denatured proteins coalesce into insoluble aggregates large enough to scatter light and appear as opaque white curds; separation from whey requires sufficient aggregation and reduced solubility.
(ii)Storyline: Frame 0–2: Static shot of a transparent glass bowl holding uniform warm milk (subtle surface sheen, no chill cue). Frame 3–5: A spoon enters the milk and begins a slow, continuous circular stir. Frame 6–8: While the spoon keeps circulating, vinegar is poured in a thin stream from a container held above the bowl, landing in the region the spoon is stirring; curds begin appearing within that stirred zone as opaque white clusters. Frame 9–10: Curds persist and grow in number/size as stirring continues; a clear contrast is visible between curds (opaque, granular, solid-like) and the surrounding whey (translucent, smoother, less opaque), with the bowl, milk, vinegar source, and spoon all held in the same frontal/slightly-angled framing throughout.

Manual:
Experimental Procedure
1. Place warm milk in a transparent glass bowl.
2. Slowly add vinegar into the bowl while gently stirring with a spoon.
Observation of Experimental Phenomena
White curds form and separate from translucent whey as vinegar mixes into warm milk; curds appear as opaque, grainy, lump-like clusters suspended in liquid.
Summary of Experimental Principles
Acid (vinegar) denatures milk proteins (e.g., casein), causing them to unfold and aggregate into solid curds; warmth accelerates this process.

Prompt Grounding rubric:
level_1: No transparent glass bowl is shown; no milk (warm or otherwise) is visible in it; no vinegar container or vinegar stream appears anywhere; no spoon is present; nothing resembling this milk-and-vinegar curdling setup appears at any point.
level_2: A transparent glass bowl holding a white liquid is shown, but the liquid does not read as warm milk (no surface sheen or any warmth cue; it could pass for a cold liquid or something else entirely); and/or no vinegar container or stream is ever shown near the bowl; a spoon may be present but never touches the liquid, and no pouring or stirring action occurs.
level_3: The bowl holds a milk-like white liquid, a container tips and releases a visible stream into the bowl (readable as the vinegar addition), and a spoon dips into and moves through the liquid at some point; but the setup fails to line up as one coherent action: e.g., the vinegar is poured in completely before the spoon ever enters and starts moving (no overlap between the pour and the stir), or the vinegar container and the bowl appear in separate shots or mismatched camera angles rather than together in one frame.
level_4: The bowl holds warm milk with a visible surface sheen; a spoon enters the bowl first and begins a slow, continuous circular stir; while the spoon keeps moving, a container tips above the bowl rim and a visible vinegar stream enters the milk; the bowl, milk, vinegar container, and spoon stay in one fixed side-by-side arrangement under one consistent camera framing for the whole sequence, matching the manual's order: milk already in the bowl, then vinegar added while stirring is already underway.
level_5: All elements of score 4 are satisfied, and additionally: the spoon's circular stirring is already running before the first vinegar drop lands and keeps going without pause through the entire pour, rather than starting only once the pour is finished; the vinegar stream visibly lands in the same patch of milk the spoon is actively moving through, rather than in an untouched corner of the bowl; the framing keeps the bowl rim, milk surface, spoon handle, and vinegar container all legible together at the exact moment the vinegar starts entering the milk.

Scientific and Causal Correctness rubric:
level_1: No state change is observed anywhere in the bowl: the milk stays a uniform, fully liquid white from start to finish; no curds, no cloudiness, and no change in opacity ever appear, even after the vinegar reaches the milk.
level_2: The milk grows slightly cloudier or thicker-looking after the vinegar reaches it, but no discrete curd particles ever form; there is no visible separation between solid curd and liquid whey, and the overall color/opacity change looks the same everywhere in the bowl regardless of where the vinegar or spoon has been, giving no visual link between the vinegar addition and the change.
level_3: After the vinegar reaches the milk, a patch of cloudiness or faint opacity appears, but it never resolves into distinct curd particles (no grainy or lumpy texture is visible); no separation between solid curd and clear whey is shown; the milk's color stays white while overall clarity drops unevenly, but the change looks delayed, patchy, or unrelated to where the vinegar entered or the spoon has stirred.
level_4: Distinct white curd clumps appear within the milk after the vinegar reaches it; each clump is visually distinguishable from the surrounding milk by its lumpy/grainy shape, its rougher texture, and its greater opacity; curds appear only after vinegar has entered the bowl and only in the area the spoon has stirred it into, with no curd visible anywhere beforehand.
level_5: All elements of score 4 are satisfied, and additionally: the curd clumps keep growing in size and number as stirring continues after the vinegar is added; they stay suspended in the liquid rather than fully sinking or dissolving back into a smooth liquid; a visibly clearer, less opaque whey appears around the curds, so the opaque curd clusters and the more translucent whey remain clearly distinguishable from each other for the rest of the stirring.

Spatiotemporal Consistency rubric:
level_1: The spoon or the vinegar stream jumps into the shot with no entry motion (e.g., the spoon is suddenly inside the milk with no hand or handle bringing it in); the glass bowl's position or tilt changes abruptly between frames with no hand or force shown moving it; the reflection of the room's light on the milk surface switches from one side of the bowl to the other with no visible cause; the milk surface ripples in physically impossible ways (e.g., ripples spreading from an empty patch, or freezing into a rigid pattern); the bowl rim visibly breaks apart or vanishes for part of the video.
level_2: The spoon enters the bowl with a visibly broken path (e.g., it is outside the bowl in one frame and already submerged in the next, skipping the entry motion); the vinegar stream appears mid-air already fully formed rather than emerging from the container's spout; the reflected highlight on the milk's surface stays fixed in place even as the spoon disturbs the surface; a short freeze or a duplicated-frame stutter occurs, or the room lighting flickers once for no reason tied to the action.
level_3: The bowl, milk, vinegar container, and spoon stay in the same relative arrangement from first frame to last; the spoon's stirring path is smooth and physically plausible (no sudden jumps, no floating above the liquid, no unnatural speed changes); the milk surface reacts believably to the stirring (ripples spread outward from the spoon tip rather than appearing frozen or running backward); the light's reflection on the bowl and milk keeps the same position and brightness across the video; the spoon and any forming curds stay visible frame to frame without dropping out and reappearing, though small imperfections are allowed, such as the spoon tip briefly passing behind the bowl rim, or a curd cluster momentarily blurred by the stirring motion without losing the overall curdling story.
level_4: All elements of score 3 are satisfied, and additionally: the bowl interior, the point where the spoon meets the milk, and the region where curds are forming stay unobstructed in every frame; ripples from the stirring spoon spread and fade at a steady rate that matches the spoon's visible speed; the shadow cast by the spoon and bowl on the countertop keeps the same direction and softness throughout, without suddenly appearing, disappearing, or swapping sides; no frame shows the bowl, spoon, or milk surface warping or jittering out of its expected shape.
level_5: All elements of score 4 are satisfied, and additionally: the spoon traces a steady, gentle circular path through the milk with no interruption; each curd cluster keeps a consistent size, opacity, and edge definition as the camera holds on it, rather than flickering sharper or blurrier between frames; motion blur from the stirring never obscures whether a given patch of liquid is curd or whey; no compression blockiness, ghosting, or similar rendering artifact appears on the bowl, spoon, milk, or curds; the video reads as one uninterrupted shot from the still bowl of milk at the start to the visibly separated curds and whey at the end.