Domain: Natural Science — Biochemistry & Molecular Biology
Target concept: Phenol-chloroform extraction for DNA purification (core technology in nucleic acid isolation)

Video generation prompt: Take a small volume of the DNA solution into a tube, add an equal volume of phenol-chloroform mixture, gently invert the tube three times, and let it stand for 3 seconds to observe.

Evaluation guide:
(i) Target concept: Liquid-liquid phase separation driven by immiscibility and density difference following mechanical emulsification.
Minimum mechanism: Two immiscible liquids of different densities must be combined, agitated to form a transient emulsion, then allowed to rest so interfacial tension drives coalescence and stratification into distinct layers; a brief few seconds of standing after gentle inversion is expected to show the layers beginning to resolve, not necessarily a fully sharp, final interface.
(ii)Storyline: Frame 1–2: DNA tube and phenol-chloroform reagent shown side-by-side in fixed overhead/frontal view. Frame 3–4: Reagent added into tube (visible meniscus rise). Frame 5–7: Tube capped and inverted three discrete times (full 180° rotations, hands visible). Frame 8–10: Tube placed upright and held motionless; over these few seconds, a boundary begins to emerge between the two immiscible liquids and grows progressively more distinct (a fully sharp, stable interface typically continues to develop beyond this brief window, or is achieved via subsequent centrifugation, which is outside this shot). Critical visibility constraints: tube must remain fully in-frame and unoccluded during all phases; the emerging boundary must be visible across the tube's diameter; color differentiation between the amber-yellow organic layer and the colorless/faint-blue aqueous layer must be unambiguous under neutral lighting.

Manual:
Experimental Procedure
1. Place a tube containing colorless DNA solution on bench.
2. Add equal volume of amber-yellow phenol-chloroform mixture using pipette/dropper.
3. Cap tube, gently invert three full times (end-over-end).
4. Place tube upright and wait 3 seconds.
Observation of Experimental Phenomena
Within the few seconds of standing, the mixture begins visibly separating into two regions: an upper colorless/faint-blue layer (aqueous DNA phase) and a lower amber-yellow layer (phenol-chloroform phase). The boundary between them is still somewhat hazy at this point rather than perfectly crisp, and continues to sharpen with additional undisturbed standing time (full resolution of a clean, stable interface typically benefits from longer settling or brief centrifugation).
Summary of Experimental Principles
Phenol-chloroform is immiscible with water; DNA remains in the aqueous phase due to its polarity; the organic phase (phenol-chloroform) extracts proteins and lipids; the density difference between the two phases drives phase separation upon standing after emulsification by inversion.

Prompt Grounding rubric:
level_1: No tube containing DNA solution is shown, no phenol-chloroform mixture is shown, no addition action occurs, and no inversion or standing action is depicted; none of the required elements (DNA-solution tube, phenol-chloroform reagent, capping, hands performing inversion) appear in a coherent setup.
level_2: A tube appears, but either the DNA solution or the phenol-chloroform mixture is missing or unidentifiable; no addition of reagent into the tube is shown; no inversion motion occurs; or the sequence of steps is out of order (e.g., the tube is shown standing still before the reagent is even added).
level_3: A tube holding DNA solution and a separate container of phenol-chloroform mixture both appear in the same scene; the phenol-chloroform is added into the DNA-solution tube; the tube is capped and inverted; a standing/still period follows the inversion; the four key actions (add, cap-and-invert, stand, observe) occur in the correct order, but at least one component's visual identity is off (e.g., the phenol-chloroform mixture is shown colorless instead of its characteristic amber-yellow tint, or the tube shows no visible liquid meniscus after addition).
level_4: Everything required for score 3 is present, and in addition, all core elements are correctly identified: (a) a transparent tube holding colorless-to-faint-blue DNA solution, (b) a separate dropper/container holding amber-yellow phenol-chloroform mixture, (c) the reagent added into the DNA tube at roughly equal volume, (d) hands capping the tube, inverting it, then releasing it to rest. Inversion is performed exactly three times, visually countable as three separate end-over-end rotations, followed by the tube being set down to stand; no extraneous actions (e.g., vortexing, centrifuging, shaking) occur; camera framing and adjacent placement stay consistent throughout.
level_5: Everything required for score 4 is present, and in addition: the phenol-chloroform mixture is unambiguously amber-yellow and the DNA solution is unambiguously colorless or faintly blue; the three inversions are performed with consistent amplitude and rhythm and are individually countable with no missed or extra rotation; the hands remain visible and steady throughout, never obscuring the tube's contents once it is set down to stand; no visual glitch (flicker, duplicate hand, tube popping in/out) interrupts the sequence.

Scientific and Causal Correctness rubric:
level_1: No separation into two phases occurs at any point: the liquid inside the tube appears as a single homogeneous phase (or a single uniform color) throughout inversion and standing, with no visual sign that the phenol-chloroform and aqueous DNA solution are immiscible.
level_2: The two liquids remain fully mixed after standing, or an interface appears only fleetingly and then disappears again (the liquid re-homogenizes); or the phenol-chloroform is depicted as colorless/water-clear, making it impossible to distinguish the two phases even if they are physically separated; or the aqueous DNA layer is shown opaque/strongly colored in a way that would mask any layering.
level_3: After the three inversions and a few seconds of standing, the two liquids begin visibly separating into an upper and a lower region, but the boundary between them is hazy, wavy, or only partially resolved across the tube's width (consistent with just a brief standing period), or the layer colors are reversed relative to what they should be (e.g., the amber-yellow organic phase appears above the aqueous phase instead of below it), or separation appears without the preceding inversion having been shown.
level_4: Everything required for score 3 is present, and in addition: the emerging lower layer is amber-yellow (phenol-chloroform) and the emerging upper layer is colorless or faintly blue (aqueous DNA solution), positioned in the density-correct order; the separation becomes visibly more distinct as the few seconds of standing elapse (rather than appearing instantly, fully formed, the moment the tube stops moving); no mixing or re-entrainment of the two phases occurs once separation begins; the sequence of events (inversion causes temporary cloudiness, standing lets it resolve into layers) is visually supported.
level_5: Everything required for score 4 is present, and in addition: the relative volumes of the two layers look roughly equal, consistent with equal-volume addition; the upper aqueous layer stays visually clear with no turbidity or particulate matter; the boundary between the layers continues to sharpen (rather than blur or re-mix) for as long as the tube is shown standing; the hue of each layer (amber-yellow below, colorless/faint-blue above) stays consistent under the scene's lighting.

Spatiotemporal Consistency rubric:
level_1: The tube's position or appearance jumps discontinuously between the addition, capping, inversion, and standing stages (as if spliced from different shots); hands appear or vanish between one frame and the next without entering or leaving the frame naturally; the liquid level inside the tube jumps up or down without a visible cause; the scene's lighting flips abruptly from bright to dark or vice versa; the tube appears to rotate with no hand visibly touching it; or a layer boundary appears before the inversion motion has finished.
level_2: The tube's position or tilt changes noticeably between the addition and inversion stages without a smooth transition between them; hands appear only during the inversion motion and are gone before the standing period begins; the curvature of the liquid surface looks inconsistent from one frame to the next; background elements shift or resize in a way that doesn't match camera movement; or the footage shows more than a couple of visible freezes, jumps, or judders during the sequence.
level_3: The tube stays centered and upright in the same spot through the addition, capping, inversion, and standing stages; the hands keep a consistent, natural grip on the tube during the three inversions; the liquid surface and any forming boundary stay visible without being blocked from view; the room's lighting and any shadow on the tube stay steady rather than flickering; the inversion motion looks smooth and physically natural: the tube does not appear to move on its own. One moderate flaw is acceptable, such as a brief instant where a hand partly blocks the tube's bottom during the last inversion, or a short focus shift during the standing period.
level_4: Everything required for score 3 is present, and in addition: the tube stays essentially motionless during the standing period, without swaying or drifting; once the hands set the tube down, they pull away cleanly with no extra bump or re-grip; the background stays fixed and unchanging; the camera itself never pans, tilts, or zooms during the whole sequence. One minor flaw is acceptable, such as a single frame where a highlight on the glass shifts slightly.
level_5: Everything required for score 4 is present, and in addition: the tube and liquid surfaces keep a consistent shape and outline across every frame of the standing period, with no warping, stretching, or shearing; the points where the hands' fingers contact the tube stay physically plausible throughout all three inversions, without sliding unnaturally; the rotating tube shows smooth, continuous motion rather than a stroboscopic or stepped look; and no visible compression blockiness, shimmering, or moiré-like patterning appears on the tube or liquid at any point.