Domain: Natural Science — Biophysics
Target concept: Needle-like sucrose crystals gradually precipitate in the solution, interweaving with each other to form crystal clusters.

Video generation prompt: Hot sucrose saturated solution (80°C) was placed into a transparent test tube, slowly cooled, and the tube was imaged at intervals.

Evaluation guide:
(i) Target concept: Diffusion-limited, temperature-driven nucleation and anisotropic growth of sucrose crystals into mechanically interlocked clusters.
Minimum mechanism: Solution must be supersaturated upon cooling; crystal growth must proceed via addition of sucrose molecules to lattice sites with preferential elongation along one axis; interweaving requires physical contact and mutual orientation stabilization, not random aggregation.
(ii)Storyline: Frame 1: Clear, still liquid filling test tube to consistent meniscus height; no particles, no distortion. Frame 2–3: First needle-like crystals appear near tube wall or bottom, aligned vertically, isolated. Frame 4–6: Crystals lengthen, new needles nucleate adjacent to existing ones, tips begin contacting. Frame 7–9: Contact points develop branching angles; clusters emerge as interconnected networks. Frame 10: Mature clusters span micrometer-scale domains, maintaining needle identity and optical clarity. Perspective: Fixed frontal view, centered on tube; full tube height always visible; no occlusion; lighting from upper-front to reveal crystal facets and meniscus.

Manual:
Experimental Procedure
1. Fill transparent test tube with hot sucrose-saturated aqueous solution (prepared at 80°C).
2. Place tube upright on stable surface.
3. Record continuous video or capture frames at regular intervals as solution cools to room temperature.
Observation of Experimental Phenomena
- Initially: fully clear, homogeneous liquid with smooth meniscus.
- Progressively: slender, transparent needle-like crystals nucleate and grow outward from tube walls/solution interface.
- Finally: crystals interweave at junctions to form branched, fractal-like clusters suspended in liquid.
Summary of Experimental Principles
Sucrose solubility increases with temperature, so as the 80°C saturated solution cools, its solubility falls below the dissolved sucrose concentration, driving supersaturation, nucleation, and anisotropic crystal growth along the c-axis, yielding characteristic needle morphology; van der Waals and hydrogen-bonding interactions drive alignment and interweaving into stable clusters.

Prompt Grounding rubric:
level_1: No transparent test tube appears; no sucrose solution is visible in it; there's no sequence suggesting cooling over time; none of the prompt's core elements (the 80°C hot saturated solution, the slow cooling, the transparent tube, the interval imaging) show up visually anywhere in the clip.
level_2: A transparent container appears but doesn't read clearly as a test tube (e.g., wrong shape, no visible cylindrical form); liquid is present but nothing marks it as a saturated sugar solution (no prior indication of dissolving or heating); nothing signals the 80°C starting condition or a cooling process; the clip doesn't break into any recognizable stages over time. It could just as easily be one continuous unchanging shot.
level_3: A transparent, cylindrical test tube holds a clear liquid; the clip is structured so that something visibly changes over its course (several distinct static-looking moments or a smooth progression); the tube and liquid match the prompt's core setup, but nothing in frame 1 signals that the liquid started out hot and freshly saturated (no steam, no shimmer from heat, no temperature marking).
level_4: Everything at the 3-point level holds, and in addition the clip shows at least three clearly different moments of progress: an early moment with uniform liquid, a middle moment with the first visible crystal specks, and a later moment with crystals clustered together; the only prompt element not directly confirmed is the initial 80°C state, which is acceptable here since temperature itself isn't something the eye can verify and the prompt doesn't demand an explicit thermal cue.
level_5: The test tube stays centered in a fixed view throughout; the liquid starts out fully clear and uniform; the clip clearly reads as a controlled cooling sequence through at least three distinguishable stages: clear liquid only, then isolated needle-shaped crystals, then crystals interwoven into clusters; nothing extraneous enters the frame, no cut breaks the sense of steady time intervals, and the tube never appears to have been repositioned between shots.

Scientific and Causal Correctness rubric:
level_1: No crystals form at all: the liquid stays uniform for the whole clip; there's no solid material, no shape change, and no clustering, which contradicts the expected needle-crystal precipitation and interweaving.
level_2: A solid phase appears, but it's spherical, granular, or shapeless rather than needle-like; there's no interweaving or clustering; the liquid turns into the wrong kind of solid altogether, like a powdery sediment or a uniform cloudiness, rather than sucrose's characteristic elongated crystal form.
level_3: Needle-shaped structures do appear, but they stay separated and randomly oriented rather than interweaving; only a few needles form and they're spread thinly through the tube; the liquid-to-solid change looks plausible for sucrose, but the clustering that the selected phenomenon requires never shows up or stays incomplete.
level_4: Needle-shaped sucrose crystals are visible, correctly slender and elongated; some of the needles touch and interweave with their neighbors, forming small clusters at a few spots; the crystals share a consistent see-through, glinting appearance; nothing contradictory happens elsewhere in the tube: no melting, no bubbling, no separation into distinct liquid layers.
level_5: Needle-shaped crystals keep appearing and lengthening as the clip progresses; they consistently touch and interweave at sharp angles, building into branching clusters; every crystal stays uniformly transparent with crisp edges; no rounded or shapeless solids appear, nothing looks like it's redissolving, and the overall growth matches the described phenomenon of needle crystals precipitating and interweaving into clusters.

Spatiotemporal Consistency rubric:
level_1: A severe break in continuity: the test tube jumps to a different position between frames; the liquid's meniscus height changes abruptly between frames instead of smoothly settling as the tube cools; crystals appear already fully formed in a single frame with nothing leading up to them; the scene swings from bright to dark with no gradual change; the tube wall or the meniscus shows a visible tear or break in its outline.
level_2: A moderate break: the tube appears to rotate or the view zooms in/out without any reason tied to the experiment; crystals jump from one part of the tube to another rather than growing in place; the meniscus blinks out and back or disappears for a stretch; the apparent direction the scene is lit from swaps partway through with no transition; two frames show the same sparse crystal arrangement and then suddenly a fully interwoven cluster, skipping the growth in between.
level_3: Small, easy-to-miss inconsistencies only: a slight jitter in the tube's position between some frames; a single instance where a crystal edge blinks in or out for one frame before settling back; the overall brightness shifts a little from frame to frame but the general sense of where the light is coming from doesn't change; no visible tearing, jumping, or structural break anywhere in the tube or liquid.
level_4: The test tube stays fixed in both position and tilt; the meniscus stays stable and changes only gradually as the liquid cools; new needles consistently sprout right next to crystals or interfaces that were already there, never appearing out of nowhere at a distant spot; the overall brightness and the general look of the tube's illumination carry over smoothly from one frame to the next with no jarring jump; no frame shows a sudden break in the tube's outline or in how see-through the liquid looks.
level_5: No spatiotemporal flaws at all: the tube stays visually locked in place across every single frame with no perceptible drift; the meniscus's curve and height change only gradually and continuously as the solution cools; every new needle can be traced to growing out of an existing crystal or the liquid's surface, never appearing in empty space; any subtle shimmer in the liquid or gradual sharpening of a crystal's edge looks physically continuous frame to frame; nothing about the tube's brightness, reflections, or transparency ever breaks continuity.