Domain: Natural Science — Chemistry
Target concept: Benzene does not decolorize potassium permanganate.

Video generation prompt: At room temperature, a test tube contains an appropriate amount of potassium permanganate solution. An appropriate amount of liquid benzene is added to the solution in the test tube.

Evaluation guide:
(i) Target concept: Immiscibility and redox inertness of benzene toward aqueous KMnO₄.
Minimum mechanism: Benzene must be less dense than water-based KMnO₄ solution, chemically inert to cold dilute permanganate, and optically transparent enough to reveal underlying purple layer without absorption or scattering that mimics decolorization.
(ii)Storyline: [Frame 0–2] Static shot of upright test tube with purple KMnO₄ solution filling lower portion; [Frame 3–5] Liquid benzene is introduced from above and contacts solution surface; [Frame 6–8] Benzene rises and settles as distinct upper layer due to density difference; [Frame 9–10] Stable two-layer system persists: upper benzene (colorless, transparent) and lower KMnO₄ (unchanged purple), separated by sharp horizontal interface; viewpoint remains fixed, lighting constant, no motion beyond gravity-driven settling.

Manual:
Experimental Procedure
1. Place a clean test tube upright on a stable surface.
2. Add potassium permanganate solution until ~1/3 full — appears deep purple.
3. Carefully add liquid benzene on top — forms a separate, colorless, transparent upper layer.
Observation of Experimental Phenomena
The purple potassium permanganate solution remains unchanged in color; benzene forms a distinct, non-mixing, colorless upper layer with a sharp horizontal interface; no decolorization or reaction occurs.
Summary of Experimental Principles
Benzene is unsaturated but lacks polarity and reactivity toward oxidizing agents like KMnO₄ under mild conditions; thus, it does not decolorize potassium permanganate solution at room temperature.

Prompt Grounding rubric:
level_1: No test tube is shown; no purple liquid representing potassium permanganate solution is present; no separate liquid representing benzene is ever added; the scene does not depict a substance being poured or dropped into the tube.
level_2: The test tube holds a purple liquid, but no benzene is ever shown being added to it; or benzene appears somewhere in the scene without ever entering the test tube; or the two liquids never appear together in the same container; the addition, if shown at all, happens in an order or manner inconsistent with adding benzene into an existing permanganate solution.
level_3: The test tube contains a purple liquid (potassium permanganate solution); a colorless-to-pale liquid (benzene) is visibly added into that same tube; both liquids appear together in the frame from a fixed viewpoint; the addition is a clear, discrete pouring or dropping event rather than something ambiguous or off-screen.
level_4: Everything in score 3 holds, and additionally the benzene forms an obviously separate layer above the purple solution right after being added; the test tube stays upright and still throughout; whatever tool is used to add the benzene (e.g., a dropper) stays visibly connected to the pour rather than appearing disconnected mid-air.
level_5: Everything in score 4 holds, and additionally the benzene enters the tube only through a visible addition action, not from a tube already pre-filled with two layers at the start, and not from liquid appearing off-screen with no visible source; once added, the benzene layer stays visibly present and distinct from the solution for the rest of the clip; the camera stays fixed on the test tube the entire time.

Scientific and Causal Correctness rubric:
level_1: The purple solution's color visibly fades, browns, or otherwise changes during or after the benzene is added, or the two liquids appear to mix into one uniform-colored liquid, or bubbling or fizzing appears, or there is no visible color contrast between the two layers at all.
level_2: The purple solution stays purple, but no distinct benzene layer is visible (e.g., it looks the same color and transparency as the solution), or the benzene appears below the purple solution instead of above it, or the benzene looks colored or cloudy rather than clear, or the video otherwise implies decolorization (e.g., a lightened or bleached patch near the interface).
level_3: The potassium permanganate solution stays a uniform purple color before and after the benzene is added; the benzene sits as a separate, colorless-to-pale-yellow, clear layer above it; there is no color change, no visible mixing of the two liquids, and a visible boundary separates the two layers.
level_4: Everything in score 3 holds, and additionally neither layer shows any sign of the two liquids dissolving into each other, such as a cloudy or discolored zone forming near the boundary; no part of the purple layer lightens or darkens at any point; the two colors stay clearly separated from the first frame after addition onward.
level_5: Everything in score 4 holds, and additionally the boundary between the two layers stays sharply visible and does not visibly blur or take on a mixed color over the course of the clip; the benzene layer keeps a consistent near-colorless or pale straw hue rather than drifting toward blue, green, or a stronger yellow; the purple layer keeps its full, even color throughout its volume, including near the liquid surface.

Spatiotemporal Consistency rubric:
level_1: The test tube suddenly changes position or orientation between frames; the liquid level jumps to a different height with no smooth transition; one of the two layers appears or disappears with no benzene-addition event explaining it; the lighting on the tube shifts dramatically from one frame to the next; the liquid surface curves in a way that could not happen under gravity, such as pointing upward at the tube's open top.
level_2: The test tube stays in place but wobbles or jitters noticeably; the benzene layer appears instantly at full height rather than settling into place after being poured; the boundary between the two layers appears before the pour is even finished; the purple liquid's surface bulges or curves in a physically implausible way.
level_3: The test tube stays upright and still; after being poured, the benzene settles into an upper layer with a surface curve that looks physically plausible (slightly domed where it meets air, slightly dipped where it meets the solution below); there are no sudden jumps in layer height or boundary position, and any motion is smooth and consistent with the denser solution staying below the lighter benzene.
level_4: Everything in score 3 holds, and additionally the curve of each liquid surface stays consistently shaped and stable across frames; the tube's edges and the layer boundary line up consistently from frame to frame with no visible jump or misalignment; there is no sudden brightening or dimming that breaks the sense of continuous time passing; the glass wall's thickness and the way it bends light behind it stay visually consistent without flickering.
level_5: Everything in score 4 holds, and additionally the boundary between the two layers stays continuously sharp without flickering, shimmering, or briefly blurring at any point; there is no obvious optical distortion or warping introduced at the layer boundary; the purple layer is never visible through the benzene layer in a way that contradicts the benzene sitting on top; there is no sign of duplicated or skipped motion that would make the settling process look unnatural.