Domain: Natural Science — Chemistry
Target concept: The colorless solution gradually turns into a uniform bluish purple, with no precipitate and no phase separation.

Video generation prompt: Mix glycine solution with ninhydrin reagent and heat under a water bath.

Evaluation guide:
(i) Target concept: Formation of Ruhemann"s purple via ninhydrin reaction with glycine under aqueous heating.
Minimum mechanism: Glycine must be in solution phase; ninhydrin must be soluble and reactive; heating must be sufficient to drive condensation/decarboxylation but not degrade product; resulting chromophore must remain molecularly dispersed (no aggregation → no precipitate/phase separation).
(ii)Storyline: Frame 1–2: Two adjacent containers: left holds colorless glycine solution, right holds ninhydrin reagent (typically colorless or pale yellow). Frame 3–4: Transfer/mixing action introduces reagents into shared container; solution remains colorless. Frame 5–6: Shared container is placed into visible water bath (immersed, with water surface and/or thermal cues). Frame 7–10: Colorless solution undergoes continuous, uniform hue shift, progressing through pale violet to bluish purple, filling entire volume homogeneously; no opacity, no sediment, no interface lines; color stabilizes only after heating context is fully established.

Manual:
Experimental Procedure
1. Place colorless glycine solution and ninhydrin reagent in adjacent containers.
2. Mix them into a single container.
3. Place mixture in water bath and heat gently.
Observation of Experimental Phenomena
The initially colorless solution gradually turns into a uniform bluish purple, with no precipitate and no phase separation.
Summary of Experimental Principles
Ninhydrin reacts with α-amino acids (e.g., glycine) under mild heating to form Ruhemann’s purple — a stable, water-soluble bluish purple chromophore.

Prompt Grounding rubric:
level_1: No glycine solution is shown, no ninhydrin reagent is shown, no mixing action occurs, and no heating context (a water bath container, immersion, or visible steam) is depicted.
level_2: Only one of glycine solution, ninhydrin reagent, a mixing action, or a water bath container appears, but they do not appear together in the same scene, and there is no sequence in which mixing is followed by heating.
level_3: Glycine solution and ninhydrin reagent both appear together in the same scene before being combined; a mixing action (pouring or stirring together) happens before any water bath or heating cue appears; the two reagents and the mixing step are visually distinguishable from each other.
level_4: Everything required at the 3-point level holds, and in addition a water bath container (or an unambiguous heating cue such as visible steam or the mixture being immersed in heated water) appears right after the mixing step, the combined solution is shown inside this heating setup, and the camera keeps the reagents, mixing, and heating context all visible without cutting away.
level_5: Everything required at the 4-point level holds, and in addition the sequence of reagents-present, then mixing, then water-bath heating is shown without skipping or reordering any step, the camera holds one fixed viewpoint on the container throughout, and the mixture, container, and heating setup all stay unobstructed and clearly visible for the whole clip.

Scientific and Causal Correctness rubric:
level_1: No color change happens; or the final color is wrong (red, yellow, brown, black, pink, or green instead of bluish purple); or the solution shows a precipitate, cloudiness, layering, or separates into phases at any point; or nothing visually ties the mixing-and-heating to any color change.
level_2: The final color is close to purple but off (e.g. plain violet with no blue tint, an overly dark indigo, or a pink-leaning lavender); or the color starts appearing before the mixture is both combined and heated; or cloudiness or a precipitate appears at the same time as, or before, the color begins.
level_3: The final color is a recognizable bluish purple (consistent with Ruhemann's purple) but is uneven across the solution (patchy, only a gradient, darker at the edges, or brighter in the center); the solution stays transparent, though a little localized haze may appear briefly while the color is developing, with no precipitate or separated layer remaining once the color is fully developed.
level_4: Everything required at the 3-point level holds, and in addition the final bluish purple color is even across the whole volume of solution, the solution stays fully clear and single-phase with no precipitate, cloudiness, or sediment, and the color begins appearing only once both mixing and a water-bath heating context have been shown, though the heating cue itself may be less than fully unambiguous (e.g. no visible steam or immersion is clearly shown).
level_5: Everything required at the 4-point level holds, and in addition the bluish purple color only starts appearing once both the mixing and a clear heating cue (visible water bath immersion, steam, or another unambiguous heat indicator) have been established, the color is even across the entire volume, and the solution stays fully transparent and single-phase throughout, with no precipitate, haze, meniscus distortion, or interface line appearing at any point.

Spatiotemporal Consistency rubric:
level_1: An object appears to teleport (e.g. a reagent shows up mid-air and then vanishes); the container abruptly changes shape or size; the lighting jumps from full shadow to full highlight within a single frame; or the solution's surface distorts unnaturally (impossible ripples, a broken reflection, or the meniscus suddenly collapsing).
level_2: At least one clear break in continuity happens: a pipette enters the frame empty and is suddenly full in the next frame with no pour shown; the water bath container appears or disappears without any motion; the color spreads in an unnatural way (a hard-edged wipe or a flicker rather than a fluid gradient); or the camera cuts between unrelated angles without ever settling on one fixed view.
level_3: The glycine and ninhydrin containers, where both are shown, keep the same spatial arrangement relative to each other; the combined solution stays in the same container for the whole clip; the water bath container, once it appears, stays in place and fully visible; the color spreads through the liquid in a way that looks like an ordinary fluid process (bottom to top or center outward) rather than jumping around; and at most one brief lighting flicker or momentary focus shift happens.
level_4: Everything required at the 3-point level holds, and in addition none of the objects deform, resize, or rotate unexpectedly; the color spreads smoothly with no sudden jumps, skips, or reversals; the direction and brightness of the light stay the same for the whole clip; and there is no tearing, warping, or stutter in the motion, aside from at most one brief, minor timing hiccup (e.g. steam that flickers in and out for a moment, or a very brief dip in color saturation during the transition).
level_5: Everything required at the 4-point level holds, and in addition the containers stay exactly where they started, in the same size and orientation, for the entire clip; any pouring or mixing motion looks smooth and follows gravity naturally; the heating cue (water surface motion or visible thermal haze) stays steady and continuous; the color develops smoothly and evenly across the whole solution with no pause, reversal, skip, or flicker; and the lighting, shadows, and reflections stay the same in every frame.