Domain: Natural Science — Physics
Target concept: Time-lapse growth process of sodium chloride crystals from evaporating salt solutions

Video generation prompt: Time-lapse photography of sodium chloride crystal formation in a shallow salt solution within a transparent glass dish as water evaporates.

Evaluation guide:
(i) Target concept: Evaporation-induced heterogeneous nucleation and cubic growth of NaCl crystals at air-liquid-solid interface.
Minimum mechanism: Supersaturation must arise solely from water loss (not cooling or dilution); nucleation requires a solid substrate defect or edge; crystal morphology is constrained by cubic symmetry and interfacial energy minimization; growth proceeds via solute addition to exposed crystal faces, not bulk precipitation.
(ii)Storyline: Frame 1: Full dish with shallow, still, colorless liquid showing curved meniscus at rim. → Liquid surface area begins decreasing at edges. → First white specks appear at rim/micro-defects (nucleation). → Specks grow into distinct cubic micro-crystals with right-angle corners. → Crystals coalesce into larger angular clusters, advancing inward as liquid recedes. → Final frames show mature white cubic aggregates occupying dried regions; exposed substrate visible between clusters; liquid confined to shrinking central zone. Perspective: Fixed overhead view; no occlusion; all events occur within single continuous shot; crystal visibility maintained throughout via sufficient contrast and resolution.

Manual:
Experimental Procedure
1. Pour saturated aqueous sodium chloride solution into a clean, flat-bottomed transparent glass dish until depth is ~1–2 mm.
2. Place dish undisturbed in still, ambient air (no fan, heater, or direct sunlight).
3. Record continuous top-down time-lapse video for 10 seconds, capturing evaporation-driven crystal nucleation and growth.
Observation of Experimental Phenomena
- Initially: uniform colorless liquid with visible meniscus at dish edge.
- Progressively: white, angular, cubic crystals appear first at dish perimeter and surface defects, then expand inward as liquid recedes.
- Finally: interconnected white cubic clusters cover drying regions; liquid surface area visibly shrinks; no crystals float or submerge.
Summary of Experimental Principles
Sodium chloride crystallizes from supersaturated solution upon solvent evaporation. Nucleation occurs heterogeneously at substrate interfaces. Crystal habit is cubic due to NaCl’s face-centered cubic lattice, yielding right-angle facets and symmetrical growth under isotropic conditions.

Prompt Grounding rubric:
level_1: No transparent glass dish appears; no shallow salt solution is shown; no sodium chloride crystals appear at any point; there is no time-lapse progression at all - the scene instead shows unrelated objects or a setup that has nothing to do with evaporation.
level_2: A transparent glass dish is shown, but it is either empty or holds an opaque or colored liquid instead of a clear salt solution (for example oil, syrup, or dyed water); no crystals form at any point, and nothing in the scene suggests evaporation is taking place.
level_3: A transparent glass dish holding a shallow, clear, colorless liquid is shown, with no crystals visible in the earliest frames; at least one later frame shows small white, angular crystalline shapes on the dish, but the progression from bare liquid to these crystals is incomplete or discontinuous - for instance the crystals appear already fully formed with no visible intermediate growth stage.
level_4: The transparent glass dish holding the shallow, colorless liquid stays visible throughout, without being replaced or blocked from view; crystals appear in stages - first as isolated white specks, then as growing clusters with visibly angular, cube-like shapes - and stay confined to the dish; no unrelated objects or different containers appear.
level_5: The transparent glass dish stays in the same position throughout, and the shallow colorless liquid occupies a visibly consistent area early on; crystal nucleation is shown starting at the dish's rim or at small surface imperfections, and growth proceeds through clearly distinguishable stages - isolated specks, then connected clusters, then larger white angular aggregates - all confined to the drying surface of the dish; the video plays as one continuous shot with no dropped frames, cuts, or changes in camera angle.

Scientific and Causal Correctness rubric:
level_1: Crystals are missing, or appear as round blobs, needles, or other non-crystalline shapes instead of angular crystals; the liquid itself changes color (for example turns blue, yellow, or cloudy) with no explanation; crystals appear before any liquid is shown, or they appear submerged within the body of the liquid rather than at its surface or edge.
level_2: Crystals appear but have the wrong shape for sodium chloride - rounded, needle-like, or branching rather than angular - or the wrong color (gray, yellow, translucent, or iridescent rather than white); crystals appear to float or hang in the air above the liquid rather than sitting on or in it; the liquid's surface area stays the same or grows instead of shrinking over time.
level_3: Crystals are white and angular, though not clearly cubic (for instance irregular polyhedra or crystals fused into shapeless masses); the liquid's surface area visibly shrinks over time; crystals mostly appear at the dish bottom or at the liquid's edge, but a few appear to be floating free rather than attached to the dish or an existing cluster; the liquid never appears to melt or redissolve the crystals.
level_4: All visible crystals are white with flat faces meeting at right angles, consistent with a cubic shape; crystals form only where the liquid meets the dish surface (its rim or floor), not suspended within the liquid or floating above it; the liquid's surface area steadily shrinks with no sudden regrowth; no crystal ever appears to dissolve, melt, or change color, and none move in a way unrelated to the drying process.
level_5: Every crystal cluster shows unmistakable right-angle, cube-like geometry; new crystals only start forming at points where the liquid touches the dish (its rim or a surface imperfection), never in open liquid or thin air; growth spreads outward from these starting points without ever shrinking back; the area of remaining liquid decreases in step with the area gained by growing crystals; nothing in the sequence - color, shape, or location of growth - contradicts how sodium chloride is expected to crystallize as water evaporates.

Spatiotemporal Consistency rubric:
level_1: The dish itself jumps to a different position or is replaced by a different dish between frames; crystals appear or disappear with no visible growth or fading; the scene's lighting switches suddenly from bright to dark (or the reverse) within a single cut; the dish appears rotated, flipped, or structurally broken (for example a cracked rim) with no cause shown.
level_2: The dish shifts noticeably in position from one key moment to the next, by roughly its own width or more; crystals appear suddenly at full size rather than growing into view; the shadow cast by the dish or crystals points in a different direction partway through with no visible reason; the liquid level changes suddenly between two frames with no gradual recession shown in between; playback appears to skip or stutter through the growth stages.
level_3: The dish stays in the same position and orientation for the whole video; the direction and brightness of light on the scene stay the same throughout; the liquid surface recedes gradually rather than in sudden jumps; crystals are visibly fewer and smaller in earlier frames than in later ones, showing a believable growth progression; brief softness of focus or slight unsteadiness during a transition does not make it unclear which crystal or region is which.
level_4: The dish does not shift or drift at all across the video; the light source produces a cast shadow and highlights on the dish that keep the same direction and brightness in every frame; the liquid's surface area shrinks steadily and evenly rather than in fits and starts; each new patch of crystal growth appears directly next to crystals already present, never suddenly in an empty part of the liquid; nothing in the image appears to stretch, warp, or shift perspective between frames.
level_5: The dish's rim, base, and the liquid's edge keep the same outline from one frame to the next with no visible shifting; the shape, brightness, and direction of shadows stay the same throughout; crystal clusters visibly grow only by extending outward from their existing edges, never by suddenly filling in new areas away from where crystals already are; the shrinking area of remaining liquid visibly matches the area gained by the growing crystal clusters, so the two changes track each other consistently across the video.