Domain: Natural Science — Physics
Target concept: Solidification

Video generation prompt: A small amount of molten paraffin is placed in a transparent test tube. A thermometer is inserted into the paraffin so its bulb is submerged, and the test tube is then lowered into an ice-water bath containing floating ice cubes and liquid water.

Evaluation guide:
(i) Target concept: Solidification of paraffin as a temperature-driven phase transition under controlled cooling.
Minimum mechanism: Paraffin must be initially above its solidification point (~46–68°C), ice-water bath must be at 0°C, and heat transfer must occur from paraffin → bath via conduction through glass; solid nucleation requires thermal gradient and time.
(ii)Storyline: Frame 1–2: Molten paraffin visible inside upright test tube; thermometer inserted, bulb submerged; ice-water bath with floating ice cubes and liquid water visible beside tube. Frame 3–4: Test tube lowers smoothly into bath until fully immersed; no paraffin solid yet; thermometer reading begins falling. Frame 5–7: Solid regions emerge near tube walls/bottom (visually distinct opacity/grain), expanding inward; thermometer column continues descending; ice-water interface stable. Frame 8–10: Solid regions dominate (>50% volume); paraffin surface may show slight contraction; thermometer reading lower than start; ice still present, water unchanged. Perspective: Fixed frontal view, full test tube in frame, no occlusion of paraffin, thermometer bulb, or ice-water interface.

Manual:
Experimental Procedure
1. Place a small amount of molten paraffin into a transparent test tube.
2. Insert a thermometer into the paraffin so the bulb is fully immersed.
3. Immerse the entire test tube into an ice-water bath (visible ice cubes + liquid water).
Observation of Experimental Phenomena
- Paraffin starts as homogeneous translucent liquid.
- After immersion, solid regions (opaque, grainy, matte) appear first near tube walls/bottom and spread inward.
- Thermometer reading decreases continuously.
- Ice-water bath maintains coexisting ice and water throughout.
Summary of Experimental Principles
- Solidification is exothermic phase transition from liquid to solid.
- Cooling via ice-water bath removes latent heat, enabling crystallization.
- Temperature remains constant only during pure substance phase change — here, paraffin is impure/mixed, so gradual cooling is expected.

Prompt Grounding rubric:
level_1: Fewer than two of the four required elements are shown (transparent test tube, molten paraffin, thermometer, and ice-water bath with floating ice cubes plus liquid water); for example only a test tube is visible with no paraffin, no thermometer, and no ice-water bath anywhere in the video.
level_2: Two or three of the four required elements appear but the setup stays incomplete (e.g., test tube and thermometer are shown but the ice-water bath never appears, or the tube holds no paraffin); or all four elements appear but the test tube is never lowered into the ice-water bath at any point, or the thermometer is inserted only after the tube is already sitting in the bath.
level_3: All four elements are present: a transparent test tube holding a visible amount of molten paraffin, a thermometer inserted into the paraffin with its bulb submerged, and an ice-water bath (floating ice cubes plus liquid water) into which the test tube is fully lowered; the paraffin is placed and the thermometer inserted before the tube touches the bath; no extra apparatus such as a beaker, stirrer, or burner appears in frame.
level_4: Everything required for a 3 is present, and in addition the layout is physically sensible: the thermometer bulb sits within the paraffin rather than pressed against the glass wall or tube bottom, the test tube stands upright and centered in the bath without tipping, the paraffin's fill line sits visibly below the tube's rim, and neither the paraffin nor the thermometer bulb is hidden behind the tube wall or the bath's rim.
level_5: Everything required for a 4 is present, and in addition every element keeps a consistent identity across the whole video: the test tube stays transparent and the same size and shape throughout; the paraffin looks like a uniform clear liquid before immersion begins, not already grainy or cloudy; the thermometer stays in the same inserted position with its stem visible above the paraffin surface; the ice-water bath keeps showing visible ice pieces alongside liquid water; and no paraffin solidification is visible before the tube is fully lowered into the bath.

Scientific and Causal Correctness rubric:
level_1: No causal relationship between the ice-water bath and the paraffin's state is shown at all: the paraffin appears solid for the entire video with no preceding liquid phase, or the thermometer reading never changes from the first frame to the last, or the ice-water bath is missing ice, missing water, or missing entirely, leaving nothing for the paraffin to respond to.
level_2: A cooling effect is attempted but is scientifically backwards or incomplete: the paraffin becomes more liquid after immersion instead of solidifying, or the thermometer reading trends upward for at least half of the time the tube sits in the bath, or the ice-water bath shows only ice with no liquid water or only water with no ice, or the paraffin already looks opaque or grainy before the tube ever touches the bath.
level_3: The paraffin starts as a clear, uniform liquid with no cloudiness; after the tube is fully immersed, visibly opaque, matte, or grainy solid regions begin appearing in the paraffin; the thermometer reading falls steadily from the start of immersion to the end; the ice-water bath keeps showing both floating ice pieces and liquid water at the same time throughout.
level_4: Everything required for a 3 is present, and in addition the solidification follows a believable pattern: the first opaque or solid patches appear near the tube's inner wall or bottom (the surfaces closest to the cold bath) before spreading toward the center of the paraffin column; the thermometer's bulb stays submerged in the paraffin the whole time; the temperature reading never rises or plateaus once immersion has begun.
level_5: Everything required for a 4 is present, and in addition the timing of every event matches the setup: no solid paraffin appears before the tube is fully immersed, solid regions never revert back to fully liquid, the thermometer's liquid column moves steadily downward without reversing direction, and the ice-water bath's ice pieces neither melt away completely nor does the water freeze solid before the video ends.

Spatiotemporal Consistency rubric:
level_1: The test tube jumps from outside the bath to fully submerged between two consecutive frames with no visible lowering motion; or the thermometer vanishes from the tube and later reappears; or the paraffin's volume or shape changes abruptly between frames with no visible cause; or the whole scene suddenly switches from bright to dark lighting within a single frame; or the test tube's shape bends or warps unnaturally.
level_2: The test tube tilts or rotates by more than about 30 degrees within a single frame instead of moving smoothly; or the thermometer's visible position shifts sideways by more than its own width from one frame to the next; or the ice cubes in the bath disappear and reappear during the sequence; or the paraffin surface suddenly ripples and then freezes in place with no transition; or the shadow cast by the test tube points a different direction than the shadow cast by the ice-water bath.
level_3: The test tube stays upright and in the same horizontal position throughout the entire immersion; the thermometer stays inserted at the same depth without sliding up or down on its own; the paraffin surface stays level and undisturbed except for the gradual appearance of solid regions; the ice-water bath's surface stays flat and level; no object among the test tube, thermometer, or ice cubes blinks in or out of view between frames.
level_4: Everything required for a 3 is present, and in addition the tube-lowering and thermometer-insertion motions play out as one continuous, unbroken movement with no visible jump cuts; the paraffin's transition from clear liquid to opaque solid unfolds gradually rather than popping into its final texture in a single frame; the ice cubes keep a steady size and shape and do not vanish or crack apart suddenly.
level_5: Everything required for a 4 is present, and in addition the whole scene holds together physically from start to finish: the test tube's glass wall shows the same kind of light-bending throughout with no sudden distortion; the paraffin's top surface keeps a consistent curved shape as it cools; the thermometer's stem stays visibly in place with no flicker; the ice-water surface keeps a natural curved edge where it meets the glass; and no part of the scene jumps, warps, or shifts in perspective between frames.